2 cSS s, Ve-* ORNL-4728 1 i MOLTEN SALT REACTOR PROGRAM

Semiannual ^Piiogftess ^epoftt

^Pcjkiod finding August 31.1971

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OAK RIDGE NATIONAL .LABORATORY jP^A"' 6V SiOS 'A^'.? ^PQRAr*rs ziy^mM

BLANK PAGE Printed in the United States of America. Available from National Technical Information Service US. Department of Commerce 5285 Port Royal Road. Springfield. Virginia 22151 Kxe: Printed Copy $3.00; Microfiche $0.95

This report was piepared as an account of work sponsored by the United States Government. NeroVr the United States nor the United States Atomic Energy Commission, nor any of their employees, nor any of their contractors, subcontractors, or their employees, makes any warranty, express or implied, or assumes any legal liaMity or responsibi'ity for the accuracy, completeness or usefulness of any information, apparatus, product or process disclosed, or lemeseius that its use would not infringe privately owned rights. OAK RIDGE NATIONAL LABORATORY OPERATED »Y UNION CAftftlDC CORPORAT10M HUCUAt DiVfSlON

POST OFFICE ftOX X OAK RIDGE, TENNESSEE 3700

ORNL-4728 Errata

MOLTEN-SALT REACTOR PROGRAM SEMIANNUAL PROGRESS REPORT FOR PERIOD ELDING AUGUST 31, 1973

The TID-4500 category, UC-80 — Reaccor Technology, was Inadvertently ositted from the title page.

The following corrections should be aade to your copy (or copies) of the subject report:

Page v, PART 3. MATERIALS DEVELOPMENT should start with Chapter 11.

Page 1, PART 1. MSBR DESIGN AND DEVELOPMENT should have the names R. B. Briggs and P. N. Haubenreich.

Page 41, Fig. 5.3 should be replaced with the corrected version.

Page 45, PART 2. CHEMISTRY should have the name W. R. Grimes.

The attache I page is printed on gummed stock and the corrections may be cut out and pasted directly on the copy. Pagev

PART 3. MATERIALS DEVELOPMENT

11. EXAMINATION OF MSRE COMPONENTS 89 I I.I Examination of Hastelloy N Componenb Exposed to Fuel Salt in the MSRE 89 11.2 Examination of Components from In-Pile Loop 2 94 11.3 Observations of Grain Boundary Cracking in the MSRE 96 1' A Examination of a Graphite Moderator Element 106 11.5 Auger Analysis of the Surface Layer on Graphite Removed from the Core of the MSRE 107

12. GRAPHITE STUDIES Ill 12.1 The Irradiation Behavior of Graphite at 715°C S12 12.2 Procurement of Various Grades of Csrbcn and Graphite 114 123 X-Ray Studies i 16 12.4 Thermit Property Testing 117 12.5 Helium Permeability Measurements on Various Grades of Graphite 118 12.6 Reduction of Graphite Permeability by Pyrorytk Carbon Sealing 119 12.7 The Magnified Topography of Graphite Sealed with Pyroly tic Carbon 120 12.8 Reduction of Permeability by Fhnd Impregnation 121 12.9 Fundamental Studies of Radiation Damage Mechanisms in Graphite 122

Paget Part 1. MSBR Design and Development

R.B.Briggj P. N. Haubenreich

Page 41

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0 400 500 600 700 800 900 TEMPERATURE PC)

Page 45 Part 2. Chemistry

W. R. Grimes ORNL-4728

Contact No. W-740S«ne-26

MOLTEN-SALT REACTOR PROGRAM SEMIANNUAL PROGRESS REPORT For Period Endmg Aopm 31,1971

M. W. Rosenthal, Program Director R. B. Briggs, Associate Director P. N. Haubenreich, Associate Director

-NOT7CE-

FEBRUARY 1972

OAK RIDGE NATIONAL LABORATORY Oak Ridgt, TMMMMM 37830 operated by UNION CARBIDE CORPORATION for the U «. A fOMIC ENERGY COMMISSION

MSTMNITION Of THIS DOCUMENT «l This report is one of a series of periodic feports in which we describe the progress of the program. Other reports issued in this series are fistedbelow .

ORNL 2474 Period Ending January 31,1958 ORNL-2626 Period 1-nd J»g October 31,1958 ORNL-2684 Period Ending January 31,1959 ORNL-2723 Period Ending April 30,19S9 ORNL-2790 FSriod Ending J«!y 31,1959 O*NL-28<>0 Period Ending October 31,1959 ORNL-2973 Periods Lading Jamsry 31 and April 30,1960 ORNL-3014 Prriod Ending July 3i, 1960 ORNL 3122 Period Ending Februuy 28,1961 ORNL-3215 Period Esding August 31,1961 JRNL-3282 Period Ending F^i ^y 28,1962 ORNL-3369 Period Ending Augu* 31.19f 2 ORNL-3419 Period Ending January 31,1963 ORNL-3529 Pfcriod Ending Jury 31,1963 OPNL-3626 Period Ending January 31,1964 OKNL-3708 Period Ending Jury 31,1964 ORNL-3812 Period Ending February 28,1965 ORNL-3872 Period Ending August 31,1965 ORNL-3936 Period Ending February 28,1966 ORNL4037 H~iod Ending August 31,1966 0RNL4119 Period Endinf February 28,1967 ORNL-4191 Period Ending August 31,1967 ORNL4254 Period Ending February 29,1968 ORNL4344 Period fcwHng Augurt 31,1968 ORNL4396 Period Ending February 28,1969 0RNL4449 Period Ending August 31,1969 ORNL4548 Period Ending February 28,1970 ORNL4622 Period Ending August 31,1970 ORNL4676 Period Fading February 28,1971 Contents

PART 1. MSBR DESIGN AND DEVELOPMENT 1. DESIGN 2 1.1 Motten-Sah Pewamiatiot Reactor Desiga Sttfaly 2 l.l.i General 2 1.1.2 ReactorCore 3 1.13 MSDROrT-Gas and Salt Pump-Back System 4 !.!.4 FJram Tar* CooSsg System 7 1.1.5 DrainV?JveCell 9 1.1.6 Dean C* Catch Pan 9 1.2 Some Consequssca of Tubing Failure in tir. If S8R Heat Exchanger 9 1J Side-Stream Processing cf the MSBR Primary Flow for Xenon and/or Iodine Removal 10 1.4 MSBE Design 11 1.4.1 Reactor Core Power and Neutron Pux Distribution 11 1.4.2 Reactor Core Heat Removal , 11 1.43 Maintenance Studies 14 1.5 MSBR Industrial Design Study 15

2. REACTOR PHYSICS 16 2.1 MSR EXPERIMENTAL PHYSICS 16 2.J.1 HTLTR Lattice Experiments 16 2.2 PHYSICS ANALYSIS OF MSBR 18 2.2.1 Matron Irradiation Effects Outside the MSBR Core 18 2.2.2 MSBE Nuclear Characteristics 20 2.23 Fixed-Moderator Molten-Salt Reactor 21

3. SYSTEMS AND COMPONENTS DEVELOPMENT 26 3.1 Gaseous Fission Product Removal 26 3.1.1 Gas Separator and Bubble Generator 26 3.1.2 Bubble Formation and Coalescence Test 27 3.2 Gas System Te*t Facility 27 3.3 Off-Gas Systems 28 33.1 Off-Gas System for Molten-Salt Reactors 28 3.3.2 Computer Design of Charcoal Beds for MSR Off-Gas Systems 29 3.4 MoUcn-Salt Steam Generator 29 3.4-1 Steam Generator Industrial Program 29 3.4.2 Molten-Salt Steam Generator Technology Facility 29 3.4.3 Molten-Salt Steam Generator Test Proposal*. 30

11*. IV

3-5 Sodium Ftuoroborate Test Loop 31 3.5.1 Inspection of FKP Pump Rots-y Element 31 3 6 Coobnt-Salt Technology Facility 34 3.7 MSBR Pumps 35 3.7.1 Sah Pumps for IISRP Technology Facffities 35 3.7.2 ALPHA Pump 35 3.73 Drain Tank Jet Pump System for MSDR 36 4. niSTRUMENTATION AND CONTROLS 38 4.1 Transient aid Control Studte of the MSBR Sysm 38 4.2 MSRE Design and Operations Report, Part !!B, Nucicar as

5. HEAT AND MASS TRANSFER AND THERMOPHYS1CAL PROPERTIES 39 5.1 Heat Transfer 39 5.2 Thermophysical Properties 41 53 Mass Transfer to Circulating Bubbles 41

PART 2. CHEMISTRY 6. POSTOPERAHONAL EXAMINATION OF MSRE 46 6.1 Examination of Moderator Graphite from MSRE 46 6.1.1 ResuteofVralFjtanmiation 46 6.1.2 Segmenting of Graphite Stringer 46 6.13 Examination of Surface Samples by X-ray Diffraction 47 6.1.4 Examination with a Gamma Spectrometer 47 6.1.5 Miffing of Surface Graphite Samples 49 6.1.6 Radiochemical and Chemical Analyses of MSRE Graphite 49 6.2 Cesium Isotope Migration in MSRE Graphite 51 63 Fission Product Concentrations on MSRE Surfaces 54 6.4 Metal Transfer in MSRE Salt Circuits 55

7. HYDROGEN AND TRITIUM 3EHAVIOR IN MOLTEN SALT 56

2 7.1 The Solubility of Hydrogen in Molten «JF-BeF2 56 7.2 Permeation of Metals by Hydrogen 57 7.3 Tritium Control in an MSBR 59

73.1 MassSpectrometric Examination of Stability of NaBF3OH 59 7.3.2 The Thermal Stability of Nitrate-Nitrite Mixtures 59 7.4 Dissociating-Gas Heat Transfer Scheme and Tritium Control in Molten-Salt Power Systems 60

8. PROCESSING CHEMISTRY 62

8.1 The Oxide Chemistry of Pa** in Molten LiF-BeF2-ThF4 62

5 8.2 The Oxide Chemistry of Pa * in Uranium-Containing Molten LiF-BeF2 -ThF4 64 8.3 Reductive Extraction Distributions of Barium and Thorium Between Bismuth-Lead Eutectic and Breeder Fuel Solvent 67 8.4 Removal of Cerium from Lithium Chloride by Zeolite 67 V

9. DEVELOPMENT AND EVALUATION OF ANALYTICAL METHODS FOX MOLTEN SALT REACTORS 69 9.1 In-line Chemical Analysis of Molten Fluoride Salt Streams 69 9.2 Slotted Fr Jbe lor In-Une Spectral Measurements 70

9.3 In-line Determination of Hydrolysis Products in NaBF« Cover Gas 71 9.4 Determination of Hydrogen in Fluoroborate Salts 73

9.5 Voltammetric and Electrolysis Studies of Hydroxide Ion in Molten NaBF4 74

9.6 Ekctroanarytkal Studies in the NaBF4 Coolant Salt 75 9.7 FJectroandytical Studies of NKJI)in Molten Fluoride Fuel Solvent 75

10. OTHER FLUORIDE RESEARCHES 77 10.1 Absorption Spectroscopy of Molten Fluorides 77

10.1.1 The Disproportionarjon Equilibrium of UF3 Solutions 77 10.1.2 Estimation of the Available F ~ Concentrations in Melts by

Measurement of UF4 Coordination Equilibria 77

10.2 Solubility of BF3 in Fluoride Melts 78 10.3 Fluorides and Oxyfluorides of Molybdenum and Niobium 80 10.3.1 Mass Spectroscopy of Molybdenum Fluorides 80 10.3.2 Mass Spectroscopy of Niobium Fluorides and Oxyfluorides 80

10.4 Electrical Conductivity of Molten and Supercooled Mixtures of NaF-BeF2 . 81

10.5 Glass Transition Temperatures in the NaF-E^F2 System 82 10.6 Enthalpy of Lithium Ruoroborate from 29o--700°K: Enthalpy and Entropy of Fusion 85

10.7 Nonideality of Mixing in Li2BeF4-LiI 86 li. EXAMINATION OF MSRE COMPONENTS 89 11.1 Examination of Hastelloy N Components Exposed to Fuel Salt in the MSRE 89 11.2 Examination of Components from In-Pile Loop 2 94 11.3 Observations of Grain Boundary Cracking in the MSRE 96 11.4 Examination of a Graphite Moderator Element 106 11.5 Auger Analysis of the Surface Layer on Graphite Removed from the Core of the MSRE 107

PART 3. MATERIALS DEVELOPMENT 12. GRAPHITE STUDIES Ill 12.1 The Irradiation Behavior of Graphite at 715°C 112 12.2 Procurement of Various Grades of Carbon and Graphite 114 12.3 X-Ray Studies , 116 !2.4 Thermal Property Testing 117 12.5 Helium Permeability Measurements on Various Grades of Graphite 118 12.6 Reduction of Graphite Permeability by Pyroh/tic Carbon Sealing 119 12.7 The Magnified Topography of Graphite Sealed with Pyrolytic Carbon 120 12.8 Reduction of Permeability by Fluid Impregnation .121 12.9 Fundamental Studies of Radiation Damage Mechanisms in Graphite ...... 122 VI

IS. HASTELLOY N 125 13.1 Electron Microscopy Studies 125 13.1.! Microstructures of Hf-Modified Hastelloy N Laboratory Mehs 125

13.1.2 Ni3Ti Precipitation in Ti-Modified Hastelloy N 129 13.1.3 Strain-Induced Piecipitation in Modified Hastelloy N 130 13.2 Mechanical Properties of Unirradiated Modified Kastell^y N 132 13.3 Voidability of Several Modified Commercial Alloys 132 13.4 Creep-Rupture Properties of Hastelloy N Modified with Niobium, Hafnium, and Titanium 137 13.5 Conosion Studies 138 13.5.1 Fuel Salts 139 13.5.2 Fertile-Fissile Salt 145 13.5.3 Blanket Salt 145 13.5.4 Coolant Salt 145 13.6 Analysis of High-Level Probe from Sump Tank of PKP-1 150 13.7 Forced-Convection Loop Corrosion Studies 150 13.7.1 Operation of Forced-Convection LoopMSR-FCL-lA 150 13.7.2 Metallurgical Analyst of Forced-Convection LoopMSR-FCL-lA 151 13.7.3 Operation of Forced-Convection Lx>p MSR-FCL-2 151 13.7.4 Metallurgical Analysis of Forced-Convection Loop MSR-FCL-2 153 13.8 Corrosion of Hastelloy N in Steam 153 13.9 Evaluation of Duplex Tubing for Use in Steam Generators 156

14. SUPPORT FOR CHEMICAL PROCESSING 163 14.1 Construction of a Molybdenum Reductive-Extraction Test Stand 163 14.2 Fabrication Development of Molybdenum Components 166 14.3 Welding Molybdenum 169 14.4 Development of Brazing Techniques for Fabricating the Molybdenum Test Loop 172 14.4.1 Resistance Furnace Brazing 172 14.4.2 Induction Vacuum Brazing 172 14.4.3 Induction Field Brazing 173 14.5 Compatibility of Materials with Bismuth 173 14.6 Chemical Vapor Deposited Coatings 176

14.7 Molybdenum Deposition from MoF6 177

PART 4. MOLTEN-SALT PROCESSING AND PREPARATION 15. Fi JOWSHEET ANALYSIS 179 15.1 Cost Estimate for an MSBR Processing Plant ! 79 15.2 Comparison of Costs for Alternate Off-Gas Treatment Methods for an MSBR Processing Plant 183 15.3 Effect of Noble-Metal and Halogen Removal Times on the Heat Generation Rate in an MSBR Processing Plant , 186 15.4 Long-Term Disposal of MSBR Wastes 186 15.5 Availability of Natural Resources Required for Molten Salt Breeder Reactors 189 Vll

16. PROCESSING CHEMISTRY 191 i6.1 Distribution of Lithium ana Bismuth Between Liquid Lithium-Thorium-Bismuth Alloys and Molten LiCl 191 16.2 Mutual Solubilities of Thorium and Rare Earths in Liquid Bismuth 193 16.3 Oxide Precipitation Studies 1% 16.4 Chemistry of Fuel Reconstitution 199

17. ENGINEERING DEVELOPMENT OF PROCESSING OPERATIONS 202 17.1 Lithium Transfer During Metal Transfer Experiment MTE-? 202 17.2 Operation of Metal Transfer Experiment MTE-2B 204 17.3 Development of Mechanically Agitated Salt-Metal Contactors 207 17.4 Design of the Third Metal Transfer Experiment 209 17.5 Reductive Extraction Engineering Studies 212 17.6 Development of a Frozen-Wall Fluorinator: Induction Heating Experiments 214 17.7 Predicted Performance of Continuous Fluorinato s 217 17.8 Engineering Studies of Uranium Oxide Precipitation 220 17.9 Design of a Processing Materials Test Stand and the Molybdenum Reductive Extraction Equipment 222 17.10 Development of a Bismuth-Salt Interface Detector 222

18. CONTINUOUS SALT PURIFICATION 226 Introduction

The objective of the Molten-Salt Reactor Program is Design of the MSRE started in 1960, fabrication of the development of nuclear reactors which use fluid equipment began in 1962, and the reactor was taken fuels tliat are solutions of fissile and fertile materials in critical on June 1, 1965. Operation at low power began suitable carrier salts. The program is an outgrowth of in January 1966, and sustained power operation was the effort begun over 20 years ago in the Aircraft begun in December. One run continued for six months, Nuclear Propulsion program to make a molten-salt until terminated on schedule in March 1968. reactor power plant for aircraft. A mo.'ten-salt reactor — Completion of this six-month run brought to a close the Aircraft Reactor Experiment — was operated at the first phase of MSRE operation, in which the ORNL in 19S4 as part of the AI5P program. objective was to demonstrate on a small scale the Our major goal now is to achieve a thermal breeder attiactive features and technical feasibility of these reactor that will produce power at low cost while systems for civilian power reactors. We concluded that simultaneously conserving and extending me nation's this objective had been achieved and that the MSRE fuel resources. Fuel for this type of reactor would be had shown that molten-fluoride reactors can be oper­ 233 ated at 1200°F without corrosive attack on either the UF4 dissolved in a salt thai is a mixture of LiF and 235 metal or graphite parts of the system, the fuel is stable, BeF2, but U or plutonium could be used for reactor equipment can operate satisfactorily at these startup. The fertile material would be ThF4 dissolved in the same salt or in a separate blanket salt of similar conditions, xenon can be removed rapidly from molten composition. The technology being developed for the salts, and, when necessary, the radioactive equipment breeder is also applicable to high-performance converter can be repaired or replaced. reactors. The second phase of MSRE operation began in A major program activity through 1969 was the August 1968, when 2 small facility in the MSRE operation of the Molten-Salt Reactor Experiment. This building was used to remove the original uranium reactor was built to test the types of fuels and materials charge from the fuel salt by treatment with gaseous F2. that would be used in thermal breeder and converter In six days of fluorination, 221 kg of uranium was reactors and to provide experience with operation and removed from the molten salt and loaded onto ab­ maintenance. The MSRE operated at 1200°F and sorbers filled with sodium fluoride pellets. The decon­ produced 73 MW of heat. The initial fuel contained 0.9 tamination and recovery of the uranium were very 7 good. mole % UF4, 5% ZrF4, 29% BeF3, and 65% LiF; the uranium was about 33% 235U. The fue! circulated After the fuel was processed, a charge of 233U was through a reactor vessel and an external pump and heat added to the original carrier salt, and in October 1968 exchange system. Heat produced in the reactor was the MSRE became the world's first reactor to operate transferred to a coolant salt, and the coolant salt was on 3 33U. The nuclear characteristics of the MSRE with pumped through a radiator to dissipate the heat to the the 233U were close to the predictions, and the reactor atmosphere. All this equipment was constructed of was quite stable.

Hastelloy N, a n*ckehrx)lybdenum-iron-chromium In September 1969, small amounts of PuF3 were alloy. The reactor core contained an assembly of added to the fuel to obtain some experience with graphite moderator bars that were in direct contact plutonium in a molten-salt reactor. The MSRE was shut with the fuel. down permanently December 12, 1969, so that the

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funds supporting its operation could be used elsewhere thorium-bearing fertile salts. In late 1967, however, a in the rr-earch and development program. one-fluid breeder became feasible because of the devel­ Most jf the Molten-Salt Reactor Program is now opment of processes that use liquid bismuth to isolate devoted to the technology needed for future molten- protactinium and remove rare earths from a salt that salt reactors. The program includes conceptual design also contains thorium. Our studies showed that a studies and work on materials, the chemistry of fuel one-fluid breeder based on these processes car have fuel and coolant salts, fission product behavior, processing utilization character: *ics approaching those of our methods, and the development of components and two-fluid designs. Since the graphite serves only as systems. moderator, the one-fluid reactor is more nearly a Because of limitations on the chemical processing scakup of the MSRE. These advantages caused us to methods available at the time, until three years ago change the emphasis of our program from the two-fluid most of our work on breeder reactors was aimed at to the one-fluid breeder; most of our design and two-fluid systems in which graphite tubes would be development effort is now directed to the one-fluid used to separate uranium-bearing fuel salts from system. Summary

PART 1. MSBR DESIGN AND DEVELOPMENT The incentives for side-stream processing of the MSBR fuel salt for iodine and/or xenon removal as an 1. Design alternative means for dealing with the 13sXe poison level are being examined. Iodine stripping would require Design studies were continued on the 300-Mw\e) Ciiiy small bypass flow rates, approximately 225 gpm MSDR The core graphite was changed to slab shapes, sufficing to reduce I35Xe poison level to ~1% in a about 1% in. X 9% in. X 21 ft long. The slabs are held 100% efficient stripper. Analysis of laboratory sparging in place by graphite pests which maintain the core experiments indicates only negligible movement of configuration yet permit movement to accommodate iodine as HI into the graphne. Combined xenon and temperature and radiation effects. Salt which reaches iodine strippers appear to be a reasonable development the drain tank by entrainment in the gas effluent from goal and a highly attractive means for achieving fX5% the gas separator is now returned to the primary poison level with uncoated graphite. circulation system by two jet pumps located in a cluster Design studies on the MSBE were continued with in the drain tank. The jets are actuated by salt flows emphasis on tie core heat removal and core mainte­ from the primaiy pumps and are arranged tc prevent nance. Both prismatic and slab-type graphite elements pumpback of gas into the primaiy loops. The manifolds were considered. Maintenance studies were also con­ that connect the NaK. cooling circuit thimbles in the ducted on repair of a leak in the primary heat drain tank have been rearranged to facilitate mainte­ exchanger. nance, and three water tanks for heat rejection are now A subcontract between ORNL and the Ebasco Ser- provided instead of one. Seismic effects on the drain viccs Group, consistine of Ebasto, Babcock and Wicox, tank and its cooling system have received preliminary Byron Jackson, Cabot, Conoco, and Union Carbide study. A basin has been provided in the drain tank ceS companies, was negotiated and signed. This mdustiial to catch accidental salt spills from the salt lines or group will conduct a design study of a 100OMJW(e) valves and to drain it into the fuel-salt drain tank. MSBR plant. They haw essentially completed the A study was made of the consequences of the mixing selection of a reference conceptual design for further of fuel and coolant salts as a result of various modes of study and evaluation. failwr of tubing in the primary heat exchangers in the MSBR reference design. Four specific cases were ex­ 2. Rifffpff Pfijakt amined: (1) doubie&ended failure near the fuel-salt outlet; (2) double-ended failure near the fuel salt inlet; During the report period we completed and lamed a (3) small coolant-salt leak into the primary system; (4) report describing the Reactor Optfcaum Design Code small fuel-salt leak into the secondary system. The (ROD), with instructions for its me. The code pat sage study a, in many places, speculative both because of has been furnkhed to the Argonne Code Center, where the preliminary status of the design and the lack of it is avaOabk upon request adequate physicochenrical data on mixing of fuel and SmcetheHastelkyyNMthefadsysiemofaaMSBR coolant salts. However unpleasant some of the conse­ should fast for the life of the plant, we have Laliuhmd quence* of tubing fauure may be, no way of generating the radiation damage canted by delayed MWIIMM either a nuclear excursion or a rupture in the primary or emitted outside the core and by kakagr MMIIOUJ from secondary loop piping is foreseen. the core. Results indicate that hehmn proa%cfjoav

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l9 primarily from B(nya) reactions, would be the most formance with these small bubbles. These tests showed important source of damage (assuming an initial l0B that the production of the small bubbles is it.fi ienccd concentration of 2 ppm). The lifetime helium pro­ mostly by the pump head and speed. Dilution tests run duction in the heat exchanger due to delayed neutrons with Cad? solution showed a very sharp increase in would be less than 2 ppb with NaBF4-NaF coolant salt, separator efficiency as the concentration approached or close to SO ppb with Li2BeF4 enriched to 99.995% 2.7 wt %, probably the point at which significant in the 7 Li isotope. In the realtor outlet line, the bubble coalescence began. Such a threshold at a lower terminal helium concentration would be less than 10 concentration has been discussed in the recent litera­ ppb from the delayed neutron source. Rather larger ture. Attempts to increase the vortex to the length amounts of helium could be produced by core-leakage needed to separate gas from the higher viscosity fluids neutrons in parts of the heat exchangers or piping led to an instability when the gas flowed at the rates directly facing the reactor vessel. Far our present needed. However, removal of the core from the annular reference design, the maximum amount of helium could recovery hub resulted in satisfactory vortex stability approach 1 ppm, primarily from "Nifaa) reactions. over the full gas flow range. A test is being planned to We calculated various reactivity coefficients for the compare the bubble formation and coalescence proper­ MSBE and compared them with values for our reference ties of molten salt with those of demineralized water MSBR. The most noteworthy differences are a positive and other solutions. fuel-salt density coefficient for the MSBE (negative for The conceptual system design description and the the MSBR) and the negative graphite temperature quality assurance plan for the molten-salt loop for coefficient for the MSBE (positive for the MSBR). Both testing gas systems (GSTF) were completed, and the of these differences are associated with a grea?« design is proceeding. neutron leakage from the smaller MSBE, and result in a A report is being written on the design bases for much more negative -overall temperature coefficient, molten-salt reactor off-gas systems. that is, S X lO^rC vs -0.9 X lO"5/^ for ihe The development of a computer program for the ft&BR. desam of charcoal beds for MSR off-gas systems was Investigation of batch fuel cycles for fixed-moderator started. The pan is to develop a new program by mohen-sah reactors has been continued. We have foujd revising and expanding existing programs. The existing that reactor lifetime-averaged reaction-rate coefficients programs provide necessary information, but they are are adequate for calculating the time-dependent fuel not arranged to be of maximum nwfcmns to the conwositioo throughout the lifetime for enriched- designer. manhnn-fbeM reactors, but only for the asymptotic Foster Wheeler Corporation was chosen as the com­ portion of the lifetime for recyckd-pkitonjum-fuefe'i pany to perform the conceptual design study of the reactors. Reaction coefficients calculated specifically steam generator for use with mohen-sah reactors. The for the hr ginning of the lifetime are required for scope of work finally included in the request for plutonium calculations, because die amounts of p'.uto- proposal package differed from mat reported pre­ ninni in die system at startup are sufficient to cause viously. The changes basically hmit the industrial firm significant lwdfiring of the neutron spectrum. Calcula­ to work on the steam generator and exclude the tions with phttonium feed ate cortimang systems design work originally requested. Remits are presented for a reactor designed as a Work continued on the preparation of a conceptual baeeder (with continuous processing) but operated as a system desam description for the steam generator converter, with erniched-uraajum fsed and batch technology facility (SGTF). This facility would be a prou i wag in four cycles over the lifetime of the aide loop of the coolant-salt technology facility (CSTF) reactor. An avenge cuuveiskm ratio greater than 90% and would be used to study transients and steady-state and a fuel cost, exclude* processing, of about 0.76 operation of some fu - and part-length tube test nuWkWhr were foundfo r tins reactor. sections of a moheo-sart steam generator. A study was made of the configurations winch could be used in the SGTF and the larger (3 MW) steam generator tube test Teats on the MSBtvscale bubble separator were stand (STTS). It was found that only the %• and continued in the water loop to study the formation of \-m.-4uax steam tubes could be tested in the 150-kW the very fine bubbles encountered with the water* SGTF at ful length and that larger tubes could be glycerol test fluid and to evaluate the separator per­ tested only under hunted inlet and outlet conditions. mi

However, multiple tubes and tubes up to about 1 in. in heated) entrance, using a proposed MSBR fuel salt as diameter could be tested in the STTS. the working fluid. Experiments were performed at two The PKP pump rotary element was disassembled, and 'fmperatures, 14S0 and ~1100°F, for which the the component parts were visually examined. Except temperature coefficients of viscosity differ by a facto* for the inner heat baffle plates, the appearance of the of 4, the higher coeffk/ent corresponding to the lower Inconel metal surfaces indicated insignificant corrosive temperature. Results indicate that, in the transitional attack. The inner heat baffle plates were severely flow regime of these experiments (Reynolds modulus attacked, and this effect was attributed to the forma­ 3000 to 4000), incieasing the negative temperature tion of corrosive products by reaction of moisture in coefficient by decreasing die average temperature re­ the incoming purge gas with pucdles of NaBF4 salt sults in a reduction in the heat transfer coefficient near which were present on the heat baffle plates as a result the exit of the heated length (120 L/D) for operation of ingassing transients. without a hydrodynamic entrance region. The influence The mechanical design of the CSTF is nearing of temperature for operation with an entrance region completion. The design now includes tb? corrosion was found not to be significant beyond L/D of about product trap for studying the deposition of corrosion 40. The observed influence of temperature on heat- products and the on-line monitoring station for study­ transfer development is attributed to the shaping ing the electrochemical and surface properties of the effect of heating for the case of a fluid whose negative salt. The puts of the MSRE to be used in the temperature coefficient of viscosity is relatively large. construction have been removed and cleaned in prepara­ Thennophysical proper ties New measurements have tion for assembly. Fabrication of the drain tank and the been made of thermal conductivity of the mixture specimen surveillance station was completed. Fabrica­ LiF-BeF2 (66-34 mole %) over the range 300 to 870°C tion of the corrosion product trap and the on-line using an improved variable-gap apparatus capable of monitoring station was started. ±10% or better accuracy. These new results suggest that The pump requirements for the CSTF and the GSTF the temperature dependency of thermal conductivity were renewed, and a plan for adapting the pumps from for this mixture is smaller than previous measurements the IISRE program was developed. It was found had indicated. The ratio of the thermal conductivity of desirable to alter the IISRE Mark II pump by use of the bquid to that of the solid was determined to be avanaule equipment to provide additional he* L ~0.75. After making temporary repairs to the ALPHA pump, it was installed in the MSR-FCL-2 test faculty and s coefficients have been measured and correlateU for being operated at test program design conditions. helium bubbles (mea. diameter fromOJOlS toOJOSin. ) A study of a particular jet pump system (two pumps extracting dissolved oxygen from grycerol-water mix- in series) for retunung fuel salt from die drain tank to curcs (Schmidt modules range from 419 to 3446) over a the fuel-salt system in a Molten-Salt Demonstration Reynolds modulus range from 8.1 X 10s to 1J6 X 10s Reactor indicated that the system was hydraulicaDy for both horizontal and vertical flow. At sufficiently, suitable for the application. high low, the horizontal and vertical results are equivalent and «e correlated in terms of the dhnension- 4. faatraaaeatatioaaa d Cowtrob less Sherwood, Reynolds, and Schmidt moduli and the ratio of bubble to pipe diameter. The hybrid computer model for use in the control A criterion for predicting the condition for equiva­ studies of the MSBR is now operational. lence is presented, and use is made u." the criterion asa Part 2 of the report on MSRE nuclear and process scaling factor to correlate the mass transfer coefficients instrumentation and an updated report on instru­ in vertical flow in die transitional region between mentation and controls development for mohensah turbulence-dominated and quiescent bubble rise san­ breeder reactors were completed and prepared for ations. publication. PART 2. CHEMBTRY 5. Heat and Mm Tranter and Physical Properties 6. PortopeiafJoaal f n anunatin i of MSRE Heat transfer. The influence of the magnitude of the temperature coefficient of viscosity on the variation of A graphite stringer removed from the core of the the heat transfer coefficient along a tube has been MSRE after being exposed to fissioning .notion salt fur determined with and without a hydrodynarnic (un- the total duration of MSRE operation appeared to be in xiv generally good condition, with sharp corners, clean Cobalt-60, found on segments of MSRE heat ex­ surfaces, and no visible evidence of attack by corrosion changer tubing and core graphite bar, must have come or radiation. X-ray diffraction analysis of material from from neutron irradiation of Hastdloy N, with subse­ the surface suggested that MojC, Ru metal, Cr7C3, and quent transport ana deposition. Higher values on core Nfle* may have been present but that Mo metal, Te graphite indicates further activation after deposition. metal, Cr metal, CrTe, and MoTe2 were probably General metal loss and deposition are indicated. The absent. Gamma scanning of cross sections of the reactor vessel walls are suggested as a source, the stringer by a pinhole technique showed the deposition transported metal possibly being sputtered by fission of ' 3SSb and ' 9*Ru to be limited to the surface and to fragments from adjacent fuel. be «ery spotty and erratic. Samples milled from the surface to the middle of the 7. Hydrogen and Tritium Behavior in Molten Salts graphite stringer were dissolved and analyzed radio- chemically for many long-tived fission product species Modifications were made to the experimental appara­ The samples were also analyzed chemically and by tus in an effort to improve the reproducibility of the delayed neutron counting for U, Li, Be, Zr, Fe, Ni, Mo, data. Result* for helium solubility in Li}BeF4 indicate and Cr by spectrographic methods. The observed that these efforts have been successful; although the concentration profiles for these species were generally hydrogen solubility data still show an uncomfortable in agreement with behavior previously observed for the degree of scatter, we believe this to be due to air surveillance specimens. The uranium analyses indicated inleakage over prolonged periods. The effects of such that there was a total of about 10 g of 233U on and in mleakagr can be corrected by a straightforward but aO of the graphite in die MSRE. The spectrographic tedious procedure. analyses indicated traces of nickel in a few of the Tests of the efficiency of hydrogen recovery in the outermost surface samples. The radiochemical analyses stripper chamber of the apparatus indicate at least 90% allowed that the "nook metals'* (,MRu, 13SSb, of the gas can b? recovered within a 2-hr period of ,,#Ag, *$Nb, and l37Te) were concentrated at the operation. Moreover, in contrast with our previous surface, that the **Sr (33-sec "Kr precursor) had a (proNbfy erroneous) result, only 5% of the hydrogen much steeper concentration profile than **Sr (3.2-min recovered resulted from the stiipper annutus cot- *'Kr precursor), and that the profiles for ,34Cs and lections. ,3TGs indicated appreciable diffusion of cesium toward Measurements of the transport of hydrogen through the fuel salt The "Co analyses indicated that some Kovar metal at 495°C indicate that the pressure nickel had deposited on the graphite surfaces. dependence for the rate of transport can be described Careful analyses for tritium in the KSRE graphite by ^, where n =0.560 ±0.011 over the pressure rang? yielded the surprising result that nearly 15% of the 1.4 toirs < P < 800 tons. The product of the diffusion tiitium produced in the MSRE was retained by the coefficient and soCubflity constant characteristic of this graphite. About one-half of thn tritinro was trapped in system under the conditions cited was foun< to be DK the outer 0.15 cm of the graphite stringer. = (5.18 ± 0.24) X 10"1 • moles/cnMnm-torr". Concentration profiles for two cesium isotopes, In studies with a tane-of-fhght mass spectrometer, ,37 ,34 Cs and Cs, were obtained on the graphite bar pure NaBF3OH was shown to decompose completely from the MSRE core center, removed in early 1/71. under continual pumping at 100°C. The volatile These profiles demonstrate diffusion of cesium atoms, product was pure water, and me yield was precisely 0.5 probably on sternal graphic surfaces, after adsorption mole H,0 per took of NaBFjOH. Continued heating to at rates consistent with estimates based on data from 800*C yielded only BF3, whose evolution began at gas-cooled reactor studies. about 245°C, and NaF, whose vapor appeared at The recovery of segments of surfaces from the MSRE 725°C. met circulating system in January 1971 has permitted In uretinunary experiments with the TOF mass the determination of intensity of deposition of fission spectrometer, pure anhydrous sodium nitrate was product isotopes in the core, heat exchanger, and pump shown to evolve only NO and 07 over the temperature bowL Antimony, tellurium, technetium, ratheiiitim, range 380 to 400°C. and niobium were found deposited strongly on both The use of a dnaociating-gas heat transfer system metal and graphite surfaces, with intensities somewhat u&ng nitrogen dioxide (Na04 <* NO} ** NO • O,) (? •* gaeater than previously observed on surveillance speci­ Na • Oa) under development in the USSR, appears to mens. offer posribiities to the Molten-Salt Breeder of ft-ti- XV

gation of tritium losses from the power system. Under 9. Development and Evaluation of Analytical dissociating conditions the effective heat capacity and Methods for Molten-Salt Reactors effective thermal conductivity of the gas are increased The first successful in-line analyses of a flowing salt severalfold, resulting in increased efficiency of heat stream are now being performed. Trivalent uranium is transport, higher cycle efficiency, and the possibility of being determined in an MSRE-type salt in a thermal lower equipment costs. convection loop using the voltammetric technique. Concentrations of U(1H) from 0.02 to 0.15% of the 8. Processing Chemistry total uranium have been measured. For these deter­ As expected, it has been found that the precipitation minations we are using a special voltammeter that has of Pa4* from a molten mixture of LiF-BeFj-TM^ been modified for operation with the counter electrode at ground potential and can be operated by a PDP-8I produces a Th02-Pa02 solid solution. From measure­ ments of the distribution of Pa4* to this phase it can be computer. This system is operated automatically and predicted that in the event of an accidental contami­ performs analyses at hourly intervals. During one 72-hr nation with oxide of an MSBR fuel, the precipitated period of constant U(III) concentration the precision of the determinations was about 2%. This operation has phase would consist mainly of a UOj-Th02 solid solution with little PaO* dissolved in it. uncovered two problems not encountered in quiescent In further studies of the precipitation of the much laboratory melts: interference from particulate matter less soluble Pa(V) oxide, its solubility in the presence of on the melt's surface and an unexpectedly high effect of surface vibrations on the electrode response. These UF4 and a U02-rich oxide phase has been found close to the predicted value, baaed on measurements in the pobfcms have largely been resolved by shielding the absence of uranium. These results thus confirm that working electrode m a nickel tube which opens below Pa5* can be precipitated by oxide from an MSBR fuel the surface of the melt and is purged of salt by a stream salt while precipitating no other oxide. of helium until immediately before the analyses are A comparative evaluation of bismuth-lead eutectic made. This feature should also extend electrode fife and with pure bismuth for application in the reductive wul be incorporated in future in-line systems. extraction process was made. Distributions of barium We are developing a sample slotted optical probe that and thorium between the eutectic melt and LiF-BeFj- wffl prove useful for the analysis of fluid streams. Its

ThF4 (7216-12 mole %) were determined at 650°C application to MSRP streams will depend on the •fter successive additions of lithium metal were made. discovery of an optical material that is impervious to

The equilibrium quotient for barium, D^J moiten fluorides. At present, LaF3 appears to be the

(DLif=9»\ X 10*, from this experiment was 2.4 best candidate for NaBF4 streams. times less than that reported for pure bismuth. The A large part of our development effort was directed s equuHbriurn quotient for thorium, DjiJ{P\Sf 6.64 X toward the analysis of NaBF4, particularly for protoa- 10*. was 3.7 times greater than reported for this salt ated species which may be of sajnificance at the tfoaui and pure bismuth. The indicated sohibiity of thorium containment problem. A wdewpohit** technique appeals in the eutectic at 650*C was approximately 1500 ppm feasmle for the m-hne aaeanucment of awdroiyss by weight or about one-half that of thorium in pure products at coolant cover gas. Both electrical and bismuth. optical methods we being tested. For catfestaonof Ims The removal of cerium from molten LiCl onto Lade system and other water detninuntiiwi a special Kari 4A, sodium form, No. 8 mesh zeoite was demonstrated Fischer method is being developed. An ii»imil at 650°C. For a 1-kg batch of LiOCeCl, (99.5-0.S coulometric titrator for tins anal>v has been fabricated mole %) and successive exposures to 14-g anquoU of and is almost ready for use. dried zeolite, loading capacities of about 0.13 g of We are now routinely determining OH~ in NaBF« cerium per gram of zeolite were fond, f/hhm the samples to low ppm levels by uw •wring the ab aurbnntt precision of the data the distribution of cerium between of pressed pellets at 3641 cm'1. To confirm tentative the molten chloride and solid zeohte pUsts could be calibration factors for this infrared method we are using expressed empiricaly as m (ppm Ce in an isotonic dilution technique for the measurement of

LCI)* 12.163+ 1.35 In (g Ce/g zeoite) for cerium total hydrogen m NaBF4. Initial rcsuto are a exceBeat concentrations down to 4600 ppm. Analyses of the salt agreement with those of the infrared method; however, phase showed essenraHy complete exchange of fitfnum the blanks resulting from the extraction of hydrogea for sodium in the zeolite. from the Pyrex equimration ampule are so high that XVI

results are subject to question. Additional measure­ A systematic study of the solubility of BF3 in

ments will be done in quartz ampules. LiF-BeF2 mixtures of varying composition is con­ A novel electroanalytical method is based on the tinuing. These measurements, which are also capable of diffusion of hydrogen into a hollow palladium electrode defining free F" activity in solvent melts, continue to

when NaBF4 melts are electrolyzed at a controlled show that over the composition range 63 to 85 mole %

potential. The measurement of the pressure generated LiF the BF3 solubility varies nearly linearly with the in the electrode is a sensitive measure of protons at ppm thermodynamic activity of LiF. Enthalpies of solution concentrations. The technique offers advantage* of and mole entropies of transfer of BF3 from the gas to specificity, applicability to in-line analysis, and the solution at the same concentrations have been evalu­ possibility of a measurement of H3/H ratios in the ated. coolant. Study of the reactions A general voltammetric study in progress on molten

NaBF4 has shown a working voltage span (vs a quasi 2MoF3(s) ** Mo(s) + MoF6(g) reference electrode) from -1.2 V, limited by the deposition of boron, to +1.8 V where dissolution of the and platinum electrode occurs. Waves for Fe3* -»• Fe2* and Fe2* to Fe° are observed at approximately —0.2 and jMoF (s) ^ jMo(s) + MoF (g) , -0.4 V respectively. The Ti** •* Ti** wave occurs at 3 4 -0.5 V while the Ti5* •* Ti° reduction is beyond the cathodic limit of the melts. in which accurate measurements of equilibrium pressure To complete the fundamental study of the electro- of the product gases were made, has permitted assess­

analytical chemistry of nicker in LiF-BeF2-ZrF4, dif­ ment of the standard free energy changes for these fusion coefficients (/)) of Na(II) were measured at reactions and evaluation of the free energy of formation

platinum and pyrorytic graphite electrodes. At 500°C of MoF3 and MoF4. The free energy of formation (per values of D of 1.0S X 10"* and 1.07 X 10"* cm2/sec fluoride bond) at 700°C appears to be -50.5 kcal for

were found by vottarnmetry and chronopotentiometry MoF«(g), -5S.0 ± 03 kcal for MoF3(s), and -49 ± 1

respectively. There was no evidence of alloy formation kcal for MoF4(g). when nickel was deposited on and stripped from a An improved procedure for synthesis of pure NbF4 platinum electrode. was developed and employed during this reporting period. The vapor products from reaction of NbjO*

10. Other Fluoride Researches and F2 have been determined over the temperature range 375 to 550*0, and the gaseous products of

Spectronhotometric techniques using the diamond reaction of NbF5 with Nb^Os have been studied over window cell have been used to determine the ratio of the temperature range 350 to 750°C.

UF3 to total dissolved uranium in molten mixtures of Continuing the investigation of electrical co iductance

LiF and BeF2 in contact with graphite. The data and its relation to glass transition temperatures, mea­ obtained for these mixtuies agree -arfl with values surements were made of the temperature dependence of

calculated using activity coefficients obtained by other conductance in molten and supercooled NaF-BeF2

workers. However, data obtain in LiF-BeF2-TnF4 mixtures containing 65 and 70 mole % beryffium mixtures by the «Dectrophotoinrtric method agree fluoride. Temperatures ranged from 540 to 329°C, much less well with the calculated values. Attempts in 105* into the supercooled region, whie activation this study to unambiguously identify the stokhsometry energies varied from 10-2 to 15-2 fecal/mote. Measure­ of tine uranium carbide phase in equtsbrium with rhe ment of glass transttion temperatures Tg in this system

UFj-Uf4 solute have not been successful. indicated that the region of buk-quenched glass forma­

Similar spec trophotome trie t^rhniqufs have been tion extends from 37 (±1) to 100 mole % ReF2, Tg

used to define the equimrnnn values falling from 129 (±2)*C at XM = 0J8 to 117°

4 at XB€fj * 030 and remaining relatively constant UFi "^UF7*- + F" (±2°) to XM 0.90, beyond which the thermal effect could not be Jnceroed. in mixtures of LiF and BeF2 as a function of

compositions. It appears that a quantitative ranking of The enthalpy of UBF4 was measured from room fluoride solvents as to their activity of free F" may be temperature to temperatures above die melting jxant. possible by use of this method. No evidence for a solid transition was found. The xvu results are compared with those for the other alkali 13. HasteOoy N metal fluoroborates. The effects of Hf, Nb, Ti, Si, and C on the The phase diagram of Li3BeF4-LiI was determined The interesting deviations from ideality of both the microstructures of several small melts have been evalu­ U BeF liquidus and the Lil liquidus are discussed. ated. The fine MC-type carbide was characteristic of the 2 4 alloys low in Si and containing low to intermediate amounts of C. Higher C resulted in relatively coarse

PART 3. MATERIALS DEVELOPMENT M2C, and Si caused the formation of coarse M«C. Commercial alloys have these same microstructures 11. Examination of MSRE Components except for the ones containing Hf, where the precipitate is not generally dispersed. Many of these new alloys Examination of specimens from the mist shield of the have exceptional unirradiated strengths. The postirradi- MSRE pump bowl, a rod from the sampler cage in the ation properties generally agree with the micro- pump bowl, and rings from the control rod thimble that structural observations with good properties being had restricted salt flow showed that all components had associated with the fine generally dispersed MC car­ intergranular cracks when strained. Two samples from bides. in-pile loop 2 were strained, and some shallow cracks Corrosion studies have continued to show excellent were formed in both samples. Thus, all metal surfaces compatibility of Hastelloy N with salts composed of exposed to the fuel salt have intergranular cracks. LiF, BeFa, UF4, and ThF4. The corrosion of Hastelloy Fission products on graphite specimens were meas­ N in sodium fluoroborate seems to be dominated by ured by two techniques. Significant quantities of impurities. Four thermal convection and two pump elements from the Hasteiloy N and fission products loops are being used to evaluate fluoroborate corrosion. were observed by both techniques. Heat transfer measurements have been made in the second pumped system, and they show that sodium 12. Graphite Studies fluoroborate obeys the Sieder-Tate correlation over a wide variety of conditions. The large range of graphitic materials which have now been irradiated in HFIR has permitted certain general­ Unstressed Hastelloy N continues to show good izations as to irradiation behavior. Two classes, so-called compatibility with steam, but two tube bunt specimens conventional materials and hot-worked materials, have failed prematurely when exposed to steam under appear to have quite limited resistance to radiation stress. The duplex nickel 280-Incok>y 800 being damage. The other two, apparently bmderkss graphites evaluated for steam service shows poor creep ductility and black-based graphites, appear to offer rom for on the nickel 280 side. This can tikety be improved by substantial improvement. Both types cf material are changes in the fabrication procedure. being studied in our own fabrication program. Speci­ mens of the binderies* type that we have made have 14. Snppuit for Chenakai Pin 11 nhu, already been irradiaijd to 1 X lO22 neutrons/cm2 in die HFIR, and to that level appear to be stable. We have continued fabrication of components for the Increased efforts are being directed at seating the rootybdenum test stand. AD of the 3%-in--diam closed- graphite against fission product gases. We continue to end half sections for the feed pots and column have somewhat mixed results with irradiated sealed dryngigcuKiit containers, including sections up to 12 samples, and in no case is there an unqualified in. long, have been fabricated by back extiusiun and successful sample. A major effort is now proceeding on machined. A rofi-bonding joining technique was de­ raicTostructural examination of the coated and surface- veloped for attaching %-, %-, and %-in.-OD ants to the impregnated samples to determine the modes of failure. 3%-in.-OD containers where electron-beam weanng The thermal conductivities of potentially useful could not be used. Leak-tight red-bonded joints have graphites are now being measured as a function of been made using commercial tube ixpandtii at 250*C fluence. An apparatus to similarly follow radiation- in an inert gas enviionoent. induurd changes in thermal expansion is almost com­ Joining studies were continued on tube-to htadrr, plete. header-to-header, and the tube-to-tube types of join* The captation of strain fields about an interstitial required for the loop. A procedure was developed for aggregate has been completed, and electron diffraction electron-beam welding the %-in.-diim tube^o^headeT calculations are well under way. type of joint. Three sen of back-extruded half sections XVU1

were successfully jcuied by either electron-beam or In preparing the cost estimate, preliminary designs CTA girth welds. Development of tube-to-tube field were made for all major process equipment items, and welding techniques using the orbiting arc welding head the costs of piping, instrumentation, and certain auxil­ was continued by joining longer lengths cf tubing in a iary items were determined by using appropriate per­ vertical alignment. centages of the costs of the fabricated equipment items. The iron-base alloy Fe-15% Mo-5% Ge-4% C-1% B The total direct and indirect costs for the plant are has teen selected as the filler metal for back-brazing $20.6 and $15 million respectively. Thus, a total plant joints in the molybdenum loop. Several methods of investment of $35.6 million is required. The resulting brazing using resistance and high-frequency induction as net fuel cycle cost (1.12 mills/kWhr) is composed heating sources have been investigated. Techniques for largely of fixed charges on the processing plant (0.7 nduct'.on brazing in a dry box and induction field mill/kWhr), inventory charges on salt and fissile ma­ brazing have been developed. terials in the reactor 2nd 233Pa in the processing plant Compatibility studies of molybdenum, tantalum, (0.42 mill/kWhr), and processing plant operating T-l 11, and several grades of graphite were continued in charges (0.083 mill/kWhr); credit is taken for excess quartz thermal convection loops operated for 3000 hr fissile material produced (0.089 mill/kWhr). A 0.28 at 700°C maximum temperature and 100°C AT. Of the power dependence of processing plant cost on process­ materials tested, molybdenum and py.olytk graphite ing rate was estimated; this indicates that a considerable have been least affected by Bi-100 ppm Li solutions. saving in processing cost could be achieved by using a T-l 11 shows good resistance to mass transfer but processing plant with a larger power generation capacity becomes embrittled during test. Unalloyed tantalum has than 1000 MW(e). exhibited much higher mass transfer rates than the Capital and operating costs were calculated for two wbove-mentioned materials. Grades of graphite having methods for obtaining and disposing of hydrogen, HF, available open pores tend to allow bismuth to pene­ and fluorine in a processing plant. The first method, trate, although no other evidence of interaction has purchase and disposal of the gases after one cycle been xoted. through the process, requires large amounts of F2, H2, Chemical vapor deposition studies on molybdenum and HF to be purchased and a large amount of and tungsten coatings have indicated that the coatings radioactive waste to be generated. The second method, are less adherent to electrokss nickel-coated specimens collection of the HF and H2 and production of compared with electrodeposited nickel-coated speci­ additional H2 and Fa for recycle by electrolysis of the mens. Tungsten CVD coatings were successfully applied HF, requires the purchase of only small amounts of HF to several roll-bonded joints, but attempts to coat a and H2 and produces only a small quantity of radio­ HasteHoy N thermal convection loop resulted in cracks active waste. Contributions to the fuel cycle cost for at the corners of two joints where the tubing was the once-through case and the recycle case are 0.11 and welded together. 0.024 mill/kWhr respectively. The recycle case was adopted for use in the processing plant. FART 4. MOLTEN-SALT PROCESSING AND Calculations were made of the thermal power that PREPARATION will be produced in an MSBR processing plant by the 15. Flowsheet Analysis decay of noble-metal fission products as a function of the residence time of these materials in the primary A study was completed in which the capital and reactor system and of the fraction of the materials opeieting costs were determined for a plant that accompanying the fuel salt to the processing plant. A proreses the fuel salt from a 1000-MW(e) MSBR on a heat generation ra»e of 200 kW will result if 1% of the ten-day cycle. The processing plant is based on the noble metals reach the processing plant in the case of a reference flowsheet that uses fluorination for uranium 1-nrin holdup time, or if 20% reach the processing plant removal, reductive extraction for protactinium removal, in the case of a ten-day holdup time. Calculations were and metal transfer for rare-earth removal. The latest also made of the heat generation rate resulting from version of the flowsheet incorporates an improved decay of the halogen fission products in the processing idethod for recovering UF« from the fluorinatoroff-ga s plant as a function of the halogen and the noble-metal and a method for recycling fluorine,hydrogen , and HF removal times. The heat generation rate will be 210 kW in the plant in order to minimize the quantity of for a halogen removal time of ten days if the noble- radioactive waste produced. metal holdup time in the reactor is 0.1 day. xix

Calculations were made of the long-term hazard of A new experiment (MTE-2B) is presently under way high-level radioactive wastes produced in the three to study further the transfer of lithium from a Li-Bi nuclear fission fuel cycles under development. Several solution containing lithium at the concentraiion pro­ aspects of the MSBR fuel cycle related to waste disposal posed for extracting trivalent rare earths from LiCl (i.e., problems are considered. 5 at. %). This experiment is designed in a manner such A survey was made of published data on the that data on lithium transfer can be obtained by several availability of and future demand for natural resources independent methods. The data obtained thus far show required for an MSBR power economy. Consideration is a decrease in the lithium concentration in the Li-Bi given to the possible impact on the MSBR concept of solution that represents an equilibrium lithium concen­ the depletion of world reserves of natural resources tration in the LiCl of less than 03 wt ppm. Since the required by molten-salt breeder reactors. corresponding quantity of reductant did not transfer to the Th-Bi solution in the experiment, it is believed that part of the decrease is due to a slight loss of reductant 16. Processing Chemistry from both the Li-Bi and the Th-Bi solutions as the result of the reaction of reductant uitli impurities in Measurements were made of the equilibrium distri­ the system. It is believed that further operation of the bution of lithium and bismuth between liquid lithium- experiment will show lower equilibrium lithium concen­ bismuth alloys and molten LiCl, and of the mutual trations in the LiCl. solubilities of thorium and selected rare earths in liquid The design of the third engineering experiment for bismuth. These studies relate to the development of the development of the metal transfer process has been metal transfer process for removing rare earths from completed, and most of the equipment has been MSBR fuel salt. fabricated. The main process vessels are now being Protactinium pentoxide was selectively precipitated installed. This experiment will use flow rates that are from LiF-BeF -ThF (72-16-12 mue %) that contained 2 4 1% of the estimated rates required for processing a up to 0.2S mole % UF by sparging the salt with 4 1000-Mw\e) reactor. Mechanical agitators will be used HF H 0-Ar gas mixtures at 600°C. The equilibrium 2 to promote efficient contacting of the salt and bismuth quotient fcr the reaction PaF (d) + %HjO(g)= \ 5 phases. Tests are under way to evaluate an agitator drive Pa O (s)+ SHF(g) was determined to be about 3 at 2 s unit and nonlubricated shaft seal assembly that is 600°C. The results of this work are consistent with water-cooled and buffered with inert gas. Although earlier indications that Pa O can be precipitated from 3 s some leakage of gas around the seal has been observed, MSBR 1. el salt as a pure, or nearly pure, solid phase. it appears that the seal will be satisfactory for use with Studies relating to the chemistry of fuel rt con­ experiment MTE-3. No evidence of stable emulsions of stitution were initiated. Gaseous UF6 reacted quantita­ bismuth in salt that had been mechanically agitated was tively with UF4 dissolved in LiF-BeF2-ThF4 (72-16-12 found. The hydrodynamic performance of mechanically mole %) at 600°C according to the equation agitated salt-metal contactors was investigated using UF4g)+UF4(d) = 2UF5(d). The dissolved UF5 ap­ mercury and water to simulate bismuth and molten salt peared to be stable in both gold and graphite equip­ in order to determine favorable operating conditions. ment. Tests of several sizes of contactors with differing agitator arrangements established that the common factor that limits the agitator speed is entrapment of 17. Engineering Development of Processing water in the mercury circulating between the two halves Operations of the contactor. Consideration of the data on limiting Additional information on the behavior of lithium agitator speed, along with data from the literature on was obtained during metal transfer experiment MTE-2. mass transfer in this type of contactor, suggests that During this experiment, the lithium concentration in optimum mass transfer performance will be obtained by the Li-Bi solution used to extract rare earths from the the use of the largest possible agitator diameter. This lithium chloride decreased from an initial value of 0.35 will also result in the lowest possible agitator speed, to 0.18 mole fraction after about S70 liters of LiCl had which should facilitate maintaining a gastight seal on been contacted with the Li-Bi solution. The decrease in the agitator shaft. lithium concentration was shown to be consistent with We have tegun mass transfer experiments in which recently obtained data on the concentration of lithium the rate of transfer of zirconium from molten salt to 97 in LiCl that is in equilibrium with L»-I>i solutions. bismuth is measured by adding Zt07 tracer to the salt phase prior to contacting the salt with bismuth Fabrication and installation of equipment for a containing reductant in a 0.82-in.-diam, 24-in.-long single-stage experiment to study the precipitation of packed column. Three of the experiment* resulted in UO2-TI1O2 solid solutions from molten fluoride salts the transfer of IS to 30% of the ,7Zr present in the salt have been completed. The major equipment items and gave measured HTU values that ranged from 1 to 4 performed satisfactorily in the two experiments carried ft; the lower values were obtained from data in which out to date. In the first experiment, a gas stream we have the most confidence. These data indicate that containing 15% water—85% argon was fed to the packed column contactors will be satisfactory for use in precipitator vessel at the rate of 0.5 scffc for a period of MSBR processing systems. We believe that much ot the 4 hr with the salt at 600°C. Analyses of samples scatter observed in the mass transfer data obtained thus indicate that 17% of the uranium initially present in the far is caused by small amounts of air entering the salt was precipitated during the run sad that a water flowing stream samplers in which samples of salt and utilization of about 25% was obtained. In the second bismuth are obtained. An improved sampling technique experiment, the temperature of the salt -id the will be used in future experiments. composition of the inlet gas were the same as in the We have been investigating high-frequency induction first experiment. The salt was contacted with the gas at heating for possible use as a corrosion-resistant heat the rate of 0.5 scfh for 9 hr, after which the gas flow source (in the molten salt) in an experiment to rate was increased to 1.5 scih for an additional 5 hr. demonstrate protection against corrosion in a con­ The total precipitation time (14 hr) extended over a tinuous fluorinator by use of a frozen wall. Heat period of about ten days. During this time the run was generation rates were measured with four induction coil interrupted on several occasions for minor equipment modifications. Analyses of samples and measurements designs in a system that used 31 wt % HN03 as a substitute for molten salt. The measured heat genera­ of HF evolution throughout the second experiment tion rates were used to compute correction factors for indicate that more than 50% of the uranium was use in equations for calculating heat induced in similar, precipitated. but idealized, geometries. These equations were then The detailed designs of the extraction column and the used to design equipment for & molten-salt induction salt and bismuth head pots were completed for the heating experiment for verifying the design equations, molybdenum reductive extraction facility, and fabri­ and for testing the operation of the proposed heating cation of these items was started. Conceptual design method and the means for introducing the power leads sketches for the equipment supports in the containment into the fluorinator. The test vessel, which is 5 ft tall vess*« *nd preliminary drawings for the molybdenum and has a diameter of about 6 JS in., is a short version of piping arrangement inside the containment vessel were the proposed frozen-wall flborinator. completed. Further work on these drawings will be A mathematical analysis for predicting continuous deferred until tlu piping can be analyzed for thermal fluorinator performance was completed, and calcula­ expansion stresses and the full-scale mockuo can be tions were made for operating conditions of interest for completed to investigate fabrication and field assembly MSBR processing. The model assumed that the removal problems. of uranium from die salt is first-order with respect to An eddy-current type of detector is being developed the uranium concentration in the salt, and took into to allow detection and control of the bismuth-salt account the effects of axial dispersion resulting from interface in salt-metal extraction columns or mechani­ die rising gas bubbles. Values for the dispersion cally agitatMl salt-metal contactors. The probe consists coefficient were obtained from recently developed of a ceramic form on which bifilar primary and correlations on axial dispersion in open columns during secondary coils are wound. A high-frequency alter­ the countercurrent flow of air and aqueous solutions, nating current is passed through the primary coil, and a and the fluorination reaction rate constant was evalu­ current that is dependent on the conductivities of ated using previously obtained data on the performance materials adjacent to the primary and secondary coils is of a l-in.-diam continuous fluorinator. The predicted induced in the secondary coil. Initial tests showed that fhiorinator heights required for removal of 95 and 99% the probe v/as quite sensitive to drift in the electronic of the uranium from MSBR fuel salt on a ten-day cycle circuit, to minor variations in line voltage, and to are 10.2 ft (for a 6-in. diameter) and 17.8 ft (for an changes in temperature of the electronic components. 8-in. diameter) respectively. The calculated results are To circumvent this problem, an improved electronic encouraging since they indicate that the desired ura­ circuit that is relatively insensitive to these effects was nium removal efficiencies can be obtained with single devised. Calculations for predicting the performance of open columns of moderate height. interface detectors were made based on measurements XXI of either the magnitude of the current induced in the samples from previous experiments. This contamination secondary coil or the shift in phase between the apparently occurred during removal of salt from the primary and secondary voltages. Optimum operating nickel samplers. To eliminate this problem, the sampler conditions were defined, and a prototype probe for use design was modified, and copper was used as the in the molybdenum reductive extraction column was material of construction. Five iron fluoride reduction fabricated. Tests carried out at room temperature runs were made with iron concentrations of about 700 continued the predicted performance of the probe. to 900 ppm. The gas flow rates used in these runs were Equipment has been installed for final testing of the only about 20% of previous values since the packed probe at 600°C with molten bismuth. column had become partially restricted. After the runs had been completed, the column was removed and cut IS. Continuous Salt Purification into sections for examination. A heavy deposit of nickel and a near-uniform deposit of iron were noted on the Contamination was found to be the reason for the packing. A column of slightly modified design has been occasional high iron concentrations reported for salt fabricated and installed. Part 1. MSBR Design and Development W. R. Grimes P. N. Haubemeich

The design and development program has the purpose molten-salt reactors and assessment of the safety of of describing the characteristics and estimating the molten-salt reactor plants. The fuel cyde studies have performance of future molten-salt reactors, defining the indicated that phitonium from tight-waterreactor s has major problems that must be solved in order to bufld an economic advantage over tsgWy enriched *3SU in than, and drtigning and developing solutions to prob­ fueling molten-salt reactors. Some studies related to lems of the reactor plant. To tins end we have published safety are m progress preliminary to a comprehensive a conceptual design for a 10TX)-MW(e) plant and have review of safety based on die design of the 100r>MW(e) contracted with an industrial group organized by MSBR. Ebasco Services Incorporated to do a conceptual design The design studies serve to define the needs for new of a IO0OMW(e) MSBR phot, This design study » to or improved equipment, systems, and data for use m use the ORNL design for background and to incor­ the design of future molten-salt reactors. The purpose porate !he experience and the viewpoint of industry. of the reactor development program is to satisfy some One could not, however, propose to build a of those needs. Presently the effort is concerned largely, IQ004fwXe) pfam.t in the near future, so we are doing with providing solutions to the major problems of the studies of plants that could be built as the next step in secondary system and of removing xenon and handling the development of large MSBRi. One such plant b the the radioactive off-gases from the primary system. Work Molten-Salt Breeder Experiment (MSBE). The MSBE is is well along on the design of the one loop facility for intended to provide a test of the major features, the /esting the features and models of equipment for die most severe operating conditions, and the fuel reproc­ gaseous fission product removal and off-gas systems and essing of an advanced MSBR in a small reactor with a for making special studies of die chemistry of die fuel power of about 150 MW(t). An alternative is tU salt. Design b nearing completion and construction is in Molten-Salt Demonstration Reactor (MSDR), which progress on a second looo faciHty for studies of would be a 150- to 300-MW(e) plant based largely on equipment and processes and of the chemistry of die technology demonstrated in the Molten-Sal'. Reac­ sodium fluoroborate for the secondary system of a tor Experiment, would incorporate a minimum of fuel molten-salt reactor. The steam generator b a major item reprocessing, and would have she purpose of demon­ of equipment for which die basic design data are few strating the practicauiy of a molten-salt reactor for use and the potential problems are many. A program by a utility to produce electricity. In addition to these involving industrial participation is being undertaken to general studies of pfeilt designs, the design activity provide die technology fur designing and building includes studies of the use of various fuel cycles in reliable steam generators for molten-salt reactors. BLANK PAGE 1. Design E.S. Bettis

1.1 MOLTENSALTDEIWNSTRATION REACTOR sarily requirements for an MSBR. it was also decided to DESIGN STUDY operate the steam system at 2400 psia (with reheat to 900°F), again in line with using conservative design E.S. Bettis conditions for the MSDR. The fuel-silt chemical treat­ L. G. Alexander H. A. McLarin ment need not consist of more than fluorination, which C.W. Coffins J. R. McWherter is an already well-developed process. Periodic discard of W. K. Furlong R. C. Robertson the ?jF-BeFj carrier salt will be used to limit accumula­ H.L. Watts tion of fission products. The built-in safety features of the MSDR give it a "walk-away" capability - that is, 1.1.1 General the decay heat removal system wfll operate even with complete loss of station pow-r. Design and evaluation studies of a 3004«W(e) rad- The reactor vessel, the reactor containment and plait tensait demonstration reactor (MSDR) were continued. building layouts, tbv fuel-salt storage tanks, and prelimi­ Toil reactor would be a first-of-a-kind prototype to nary primary and secondary heat exchanger design demonstrate the feasibility and to delineate the prob­ concepts have all been described previously.1"3 The lems of construction snd operation of a large-scak design properties of the fuel salt ad the secondary and molten-salt reactor power station. Insofar as possible, tertiary heat transport salts have been reported.3 afl aspects of the MSDR design study have been made During the past report period, however, the configura­ conservatively and in such a manner as to require tion of the core graphite was changed, and the method development of little new technology. The 26-ft-diam oi handling the off-g-js and continuously pumping salt reactor has a sufficiently low power density (~10 3 back from the drain tank was revised. The drain tank W/cm ) for the radiation damage to the core moderator cooling system, along with the drain tank valve and salt to be low enough for the graphite to last the 30-year catch pan arrangement, was also studied and probably design life of the plant. The MSDR reactor outlet received the major portion of the MSDR design effort temperature was taken as 1250"F to increase the during the past period. margin of safety with regard to radiation damage to Hastelloy N, although it has not been established that this is required. Tms reduction in temperature, together 1. MSR Program Semknnu. Prop. Rep. Feb. 28, 1970, with use of 900°F steam rather than the 1000°F steam ORNI/4548. proposed for the MSBR, will allow the nitrate-nitrite 2. MSR Propum SemUuum. Prop. Rep. Aug. 31, 1970, ORNL-4622 salt in the tertiary system to operate at a lower 3. MSR Propum SemUaam. Prop. Rep. Feb. 28, 1971, tempeiature, although, here again, these are not neces­ ORNM676.

2 3

1.1.2 in the core as indicated i the plan view, Fig. 1.1, and in more detail in Fig. 12. As described previously,3 the MSDR reactor vessel is similar to one profosed by the Ebasco made of HasteOoy N and is about 26 ft in diameter by the current industrial study of an MSML 35 ft high, including the fuel-salt mfet and outlet of atirrnhling the core at bottom and top are plenums at top and bottom. The reactor is graphite ekvaton in Fig. 13. If the slabs are not moderated and reflected, with the fuel salt circulating 21-ft lengths, they can be made up of shorter upward through the core at a velocity of about 1.S fps. joined together. Because of vie i datively low At this low velocity It wffl not be necessary to seal the density in the MSDR, fuel salt trapped in soul graphite against penetration of xenon in order to at the joints would not cause exi ,35 m»ntair. the Xe poison fraction below 0.003. Use Graphite vertical posts about 2\+ X 2714 in. of the unsealed graphite will greatly simplify the section and formed as shown in Fig. 1.2 tie used to production of graphite and will lower the fabrication maintain the configuration of the graphite slabs costs. the core, while at the same The configuration of the core graphite has been thermal and radiation-induced changed from that previously reported. Slabs of graph­ The lower 6-in. length of each post is turned to !*«. 4 ite 1 %4 X 9% in. X about 21 ft long are now spaced in diameter to fit into a hole in the bottom

71-13

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provide sufficient area for the solid daughters of the normal operation, gas from the bowl is drawn into the noble gases to coalesce. venturi and discharged along with iht gas-salt mixture Each of the gas separators in the three salt-circulation from the gas separator into the drain tank. The total loops in the MSDR discharges the gas-salt mixture into flow of salt into the drain tank via the gas separators is the drain tank through a I'4 in. line. The temperature estimated to be about 40 gpm. Two small jet pumps in of the pipe is limited to about I325°F by the cooling the tank return the salt to the primary loops. The action of the salt entrained in the gas. The line is operation of the system is described below, and the provided with a syphon break to prevent drainage of design of uV jet puiiips is described to Sect 3.7.3. the main salt-circulation loops in the event of a pump An elevation of the jet pumps mounted in the center failure. The syphon break is in the form of a loop of of the drain tank is shown in Fig. 1.4. The assembly is +*ping that rises above the level of the liquid in the installed so that it can be withdrawn from the tank if prop bowl and is equipped with a venturi, the throat repair or replacement becomes necessary. One «n *he jet of which communicates via a Vto. pip* to the gas pumps takes its suction from the bottom of a vertical space above the liquid in the pump bowl. During 6-fai. pipe at the center Hue of the vessel. The suction RETURN TO I SYSTEM (3««.)

SUMP(6n>-

FILL JET 11 DBCHABGE(2«i)~^^

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FROM SYSTEM JET FJLLJET PUMP BACK JET . — LIFT JET UJ SUCTION (l'/j in) RETURN TO PfSMARY FILL JET SYSTEM SUCTION (tVfcin.) SECTION A-A (ENLMSC9)

Fig. I A. Ekvstkmofjet tbtyi

head on the pump varies from about+1S to -5 ft as the As is also shown in Fig. 1.4, a second jet pump is level of salt in the pipe changes fi n full to empty. provided in the assembly to keep the 6-in. central pipe Since the discharge from the jet is proportional to the supplied with salt from a small sump in the bottom of suction head, varying from zero at the lowest level to the drain tank. This jet has a capacity of about SO gpm, about SO ppm when the sump b full, the jet cannot keeps the liquid pumped out of the drain tank, and, pump gas from the tank when it is empty of salt. The when the tank is empty, may recirculate gas within the jet pump uses sah as its working fluid, the salt being tank. As described above, however, the system is taken from a manifold connecting the three salt-circula­ designed to prevent pumping of gas from the tank back tion pumps. Each manifold connection has a ball check to the pump bowls. It provides automatic flow control valve to prevent backflov in the event of a pump regardless of the number of primary pumps that are shutdown. running. 7

A third jet pump & provided in the assembly to ffll required to accommodate thermal expansion are made the primary system with salt from the drain tank and to much less stringent. Use of 60 different circuits limits transfer salt from the drain tank into the fuel-salt the amount of NaK ihat could leak from one circuit to storage tank. The working fluid for this third jet pump about 16 ft3. is provided by a separate small pump located in the In another change in the drain tank system from that chemical processing cell. described previously,3 the one large water tank, to which the NaK circuits reject their heat by radiation, 1.1.4 Drain Tank Coofing System ins been replaced by three smaller tanks. The NaK circuits are manifolded in such a manner as to divide The drain tank cooling system described in a previous the heat removal capability between the three water report2 has not been changed in principle, but the pools, and with any two water tanks in operation the thimbles have been rearranged. The change was made to temperature in the drain tank could be limited to .bout facilitate the manifolding of the pipes which carry the 1400°F. This arrangement is considered to be :aore cooling NaK into and out of the thimbles. As shown in reliable than the previous one in which a single leak the plan view of the top of the drain tank, Fig. 1.5, could result in total loss of water. there are now 60 sets of thimbles, each containing 6 Studies have been initiated on the effects of seismic thimbles arranged symmetrically in a circular pattern. disturbances on the drain tank and its cooling system. Figure 1.6 is an elevation of the drain tank. One of the Preliminary calculations indicate that the individual manifolds is shown in cross section in Fig. 1.6 to thimbles in the drain tank would have a natural indicate that it would be possible to remove and replace frequency of about 1.S cps when each thimble is manifolds if maintenance were required. By manifold­ considered to be a 20-fMong cantilevered member. ing only six thimbles in a circular pattern, the measures Since earthquakes produce excitation in the range of 3

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Fig, 1.6. Miliary alt drain link iectk>ml elevation. 9 to 4 cps, means for changing the natural frequency of 1.2 SOME CONSEQUENCES OF TUBING FA1LDRF the thimbles have been given preliminary study. All IN THE MSBR HEAT EXCHANGER thimbles in each group of six would be tied or banded together at 3-ft intervals along ihe length. In addition, R. P Wichner all 60 groups of thimbles would be tied together at the bottom by "IT-bolt-type clevises. These ties would A study was made of the consequciices of the mixing restrict radial movement to make the entire array act as of fuel and coolant salts as a result of various modes of a unit if seismically disturbed, but would pennit failure of tubing in the primary heat exchangers in the longitudinal motion resulting from differential thermal MSBR reference design. Four specific cases were ex­ expansion. The method of joining the units together is amined: (1) double-ended failure near the fuel-salt indicated in Fig. 1.6. outlet; (2) double-ended failure near the fuel-salt inlet; (3) small coolant-salt leak into the primary system; (4) small fuel-salt leak into the secondary system. The 1.1.5 Drain Vahe Cell study is, in many places, speculative both because of The cell provided for the freeze valve in the fuel-salt the preliminary status of *he design and the lack of drain line leading from the bottom of the reacior to the adequate physkochemical data on mixing of fuel and drain tank has been eliminated in the revised MSOR coolant salts. However unpleasant some of the con­ design, and the valve is now located in the drain tank sequences of tubing failure may be, no way or cell. This arrangement facilitates replacement of drain generating either a nuclear excursion or a rupture in the lines and associated piping should maintenance be primary or secondary loop piping is foreseen. required. The drain lines now pass through penetrations Some additional tentative conduaons of die study in the side of the reactor cell, and the valves in these are: lines are accessible through a separate Mtch in the cover (1) For a case 1 failure (double-ended tubing fatuie of the drain tank cell. near the fuel-salt outlet of the heat exchanger), 3 .5 lb/sec of coolant salt initially leaks into the primary 1.1.6 Drain Cell Catch Pan system. The boron poison in this leakage stream is sufficiently laij* such that a low-power-level trip, if A catch pan is provided in the bottom of the reactor present, is actuated essentially immediately on arrival of cell to collect any accidental spillage of salt and direct it die contaminated fuel at the lower axial blanket in the into the drain tank through frangible disk valves. An reactor vessel. The worth of the boron poison is additional catch basin has now been added near the top estimated to be 0.18% Bkjk per pound of coolant salt of the drjan tank in the drain tank cell to catch any distributed uniformly over zones I and II of the reactor leakage from the primary salt lines and direct it into the core. drain tank. This catch basin extends from the periphery (2) Additionally, for a case 1 tubing faiuie, 0.96 of the drain tank at the top to the walls of the drain lb/sec of fuel salt initially leaks into the secondary loop. tank cell. As presently conceived, a 6-in.-diam hole in However, the bulk of the fuel-salt leakage into the the basin communicates with the drain tank, the secondary system, and the coolant-salt leakage into the opening being normally sealed by an inverted cap with primary system, occurs after reactor shutdown. A total its lip in a trepanned groove that is filled with NaF. of approximately 300 lb of ifud salt leaks into the Since the melting temperature of the NaF is about secondary system, all but 4 lb occurring in the 20-min 1600°F, the opening would remain sealed unless interval in which the freeze vahres are thawing and the flooded with fuel salt, which would dissolve the NaF loops are draining. If the cover-gas pressure in the and allow the fuel salt to run into the interior chamber secondary loop were set about 3 psi higher than the 10 to float a graphite plug and then flow into the drain prig in the present design, there would be no fuel-salt tank. leakage in this interval, and the total toss of fuel salt to With catch basins provided for the reactor cell the secondary system would be approximately 4 lb for equipment, for the salt piping in the drain tank cell, and this case. for the drain tank vessel itself (in the form of a cooled (3) It is judged that the fuel sah which leaks into the "crucible" surrounding the tank), we believe that the shell of the heat exchanger after shutdown will initially likelihood of an accident in which mohen salt collects be in the form of mumscible droplets mat subsequently in a pool in the bottom of the containment vessel freeze and settle onto the lower tube sheet. The without sufficient cooiing is very remote indeed. miximum temperature caused by this localized heat 10 source is estimated to be approximately equal to that cm'3 sec"1 at a detector positjoneo nesr the outlet of reached in central portions of the heat exchanger due to the heat exchanger. This b seven tinves the lower noble-metal heating, or approximately 1660°F when detection limit a km chambers, and henc-* *t» auto­ „oolant salt remains in th> shell. matic shutdown would be initiated a few seconds after

(4) If rapid evolution of BF3 from the coolant-salt the inception of the leak, ifa delayed neutron detector stream leaking into the primary system is assumed, a wne so deployed. maximum pressure rise cf 74 psi in the primary loop is estimated for a case 1 type of failure. It is jui ted that 13 SlD&STREAMPROCE&ONGOFTrlEMSBR rapid evolution of BFS will not damage the primary pumps if shutdown procedures are initiate^ most PRIMA the msnucible droplets that freeze and setth to the lower paphhe wifl be km. Henne, the sole significant com­ tube sheet. petitive removal rate h the slow decay to xenon, and (7) For case 3 it was assumed that a pinhole in the consequently only very small bypass flow rates are tubing allows 3 X 10"4 b/sec of coolant sak into the required. If an efficient Iodine stripper is available, primary system, at which rate approximately 2.6 hr are bypass flows as low as 225 gpm wil capture almost al required to add -0.3% 6*/* - the total worth of the the iodine before it decays to xenon, and if no other control rods. A control rod location alarm is set off at control method is applied, the xenon poison fraction some point during the gradual inward drift of the wgl be the 0.001 resuK*ng from the direct fission yield ,,s control rods. If no operator action is taken, the of Xe. tow-temperature trip on the core outlet initiates shut­ A particularly attractive situation is attained by a down approximately 26 min after full insertion. Thus, essoined iodine phis xenon stripper. If on* rauraes a the duration of this incident is 2 to 3 hr; however, even bypass flow through such a device of 10% of the 9 fairly tnsensttive BFj detector on the off-gas flow, if primary flow - equal to the bypass flow rate in the one were available, would detect the presence of the leak within minutes. (8) In case 4 a 3 X I0"4 lb/sec leakage rate of fuel 4. The "effective Mtebtny** » aefieei by Pm - |l'|/*«tT salt into the secondary system i% assumed to occur aad caa be now to be • fnnctjoa of the price coaceatratioa Tht cw—iitry of ioemt miapi* w» he rwttner llicsml hi through a 2-mil-diam pinhole in the tubing near the foe) tfct next iiaaaaaaal upon and io mo fnttarnanag rtatfrof-dw- inlet A leak rate of this magnitude would cause a flux art nport oa l3,Xa coanoi awcainwi. fiaiil—ati by law of delayed neutrons of approximately 70 neutrons •ad BoaHMnjnr aw the bans of the iodiao-flliiBfwg leaMMkt. 11 reference design through the four gas separators - and analytical and numerical solutions are indeterminate at that such a device, designed primarily for xenon these points. The subroutine HOLES plots the contour removal, does so with high efficiency, then if addition­ lines by making a Unear interpolation along the grid ally only 10% of the iodine throughput were sknultetie- lines between the given values. ousry removed, a •Si Xe poison fraction of -G.003 Because of the relatively gross spacing of lattice mould be attained without employing impervious coat- points, the power density and the neutron flux tie not mgs on the graphfee. Present understanding of ihe represented accurately in the region near the boundary mechanism of iodine stripping indicates that some HI between the core and the blanket. The neutron flux is (and Tl) will be removed in a xenon stripper employing assumed to vary ttnearty between the lattice points In inert helium stripping gas due to the presence of the core and in the blanket nearest the boundary, and protons and tritons in the fuel. The degree of HI the power density varies across the boundary with the removal may be enhanced by adding some HF to the chants in flux and foes-salt fraction. The apnrnvunatinn •tripping gas. of spherical geometry by stacked ndewirfcal dhfcs. which k used in CITATrOH, becomes evident in the 1.4 MStEDESIGN perturbations in the contour haws for power naiMflu M.I.Lundifi J. & lecWherter near the vessel wal. Bfraust of the lynunatiy of aha core, al the contour Bnes should hast drmn which aee 1.4.1 Reactor Cote Power nernendicular to the axes. Aenui. the laise difference in AMJ ai^^^^^M w»n n^AJL^^m •Mi iWIQwV m UMMOK die values of the coordinates of die Ptfftir* points obscured this fharafltrittir at the higher power leveis J. R. McWbtrte J. P. Sanders where dat chanm In values for aasacent strike noaats ^*w^^* • PBW» w^^^ewnnsw' ew*/ *WJV*V w^rr enwjme^o^wvwv emra*warv uww/vjowves The design studies reported previously* were contin­ was the greatest. ued with the reactor core concept remaining sawnttaBy The values shown for power density in Fig. 1.7 ate unchanged. The core is a cylinder 45 in. m diameter and W^9m wSUwH w%^B^paasw ^a^ ejwe^a> %V«v ajaswaa) uewv^w^weias^we^V • Bw^smwPwB^ S7».lifhrcYfttedtfgTapr«iebmart tinuhiat occur at a radial position of 57 cm (22% in.) foelsalt.Thecorehma90^4DsplKricaln»k^wveastl. andatanaxiaipoa)tionof72cm(28%in.)a«ov«tsw The jpace between die vessel waR and the core k ftfcd nwJnlone: at these noasts. the salt fraction chonsss fjom •e^v^^^^e^e^^^n WJW* vw^w* wvwve^ wwe^ ^^ee?v* nnwvvi ^nssmmsnanpav •owjmsw with fuel ash. The reactor thermal power feISOMW . aiS to I JOO «the radial direction and to 0.70 tad*, A computer subroutine, entitled HOLES, was wed to axial nwaction. produce contour plots of the power dartRmfon and Thai nana subroutine was used to draw contour pfocs neutron fluxes in the MSBE core; the calculated pewtr of antral ooenMnations of the ansa enemy nrauns of and neutron flux distributions were produced by a ^** ^^ ^^^^tm w^^s^vw^m^^nva? ^^u wvv evawva* w^eewwnsjw aan^^e^msMP us ftadte-dement, multifroup reactor phyrics code called neutrons in die MSBE. To get the graphite dasnage fksx, CITATION. Data from CtTArON cm 41 (the 4S4n.- data from the first (hiajMst)grc^wemconsbinsd with dtara, S74n.-hkji cylindrical core with a 0.IS salt 85% of the data for the second energy group. This gives fraction located in a 90-nv-diom spherical vessel) was die estimated ffcu above SO IteV and wmusc4» input scaled to a reactor power of ISO MW as Input for for the plot given in Fjg. I A. HOLES. 1.4.2 sUacSmCemHeatResneval Two of the plou produced are shown In Figs. 1.7 and fLA.McLain D.W.WkW 1.8. Several characteristics of the plots are dependent upon the features of the CITATION code. The CITA- Calculations indfratf dtat the graphile inodaritor TION code indicates the value of the power density and temperature at die center of die reference three pass neutron flux for a limited number of points In the axial MSBE core1 k 100 to IS0*F hkfcer than it is at die center of die reference MSBR com.* The nwchnum spherical geometry by using a series of stacked cyimdri- ww#BBB^^BB»n>wsB"* wl8» BBBW l^flsvl 1^1 wRBv ghaaw^BRew tnRRV Be* BJW/4"WJB> cal disks of decreasing radius. Values of the power density and neutron flux for coordinate points at the center Hne and rmdptane are not given since thr 4. TVAinsjIiiiienaswjanuntteORleL. '. «» Sw aKwnener* jsunuv ew evenes? nxsvssMw jwnjpe lew* QldcMM-1177 fjtsunwir 1*70). f. Boy C Balattma (ed.K Cencnsfaef Oak* Jws> of & 5. HSR ftaavw* Smfmm. Anr. Aa\ M If, mi. Jkefeffctf MoltmSrtt aVewJr Ream*. 0RNL4S41 (lent O*NK*74,pe,»-40. 1971). 12

Ft 1.7.

1450^F, aod tha average temperature to I3WF. For a rate,9 114 W per cubic ctntimtUf of core aod II Wper tfugtopeji core, theet temperatures are about )0*F cubic etc jmettr of graphite, respectively. These tem­ tower. A disadvantage of the rinajc paw core b that tha peratures abo tosprytha t the graph** at the center of velocity required to achieve the 2S0*F AT across tha the reactor core would have to be replaced after about core to only ofuvthtod of that hi the IS-ft-lwjh MSBR

The htojh tanperatufts at the center of the MSBE core e, J, BL UUJlt* mOM /MWUM /•7/. eewvw vjpwww w^^ uoww/ OVB^HW •^^e^sw^sw so^e"OOOw)%^f wjovev WJP w^a^ewwww iSww^eu^ouwA •71-JI. pp. 4-4 (I 13

j u

r- - "i r SO 60 71 RADIAL OfSTAflCE (cm) ne,ij. fln<£>ttb*V).

1.7 years of raft-power operation usmg the relation recommended by Eatherry." Cakatotiom ware also aarfacts was redaced to 3J0, 2.75, aad 2J ia-. bvt the made for prismatic moderator etemtaJs m a samfe-past central hole ammeter ins add at 0.6 in. Theee damps resorted m average graphite temperataaes at the caster of the core of 1310, 1290, ami 1260*F, lesyeUrfly, 10. D. Scott mi W. p. Eadmty. "Cnjaln mi Xaaoa with cornspoadma araaame ttfetaam of 1.9. 2J0. aad Mnk aad Taeir fnrlatacc oa MoftniJift faartmr Dtakai** 2.1 years. Average graphite tamperataras aad matanet NucLAipL TtdmoL S, 179-ff (Fearaary 1970). akmg the reactor caatar Mae for the 3-aa. Dramatic 14

clement are shown in Fig. 1.9. The minimum graphite the reference design.7 The main difficulty in removing lifetime is at the center of the core. elements individually is holding the elements remaining Slab-type moderator elements also were considered. in the core in their normal upright positions when some At the center of the core, slabs of thicknesses of 1.0, have been removed. A permanent fixture or a re­ 1.25, and 1.5 in. have average graphite temperatures of movable jig will have to be designed to accomplish this. 1270,1290, and 1320°F, respectively, and lifetimes of uryout studies of the MSBE primary heat exchanger 2.0,2.0, and 1.9 years, respectively. were made with the major consideration being given to maintenance. In one approach proposed, a tube can be plugged in place or the entire heat exchanger can be ONNL-MB 71-ISO removed from the reactor cell for repairo r replacement. The heat exchanger is assumed to be a U-shaped unit ANERMJF. GRAPHITE TEMPERATURE m 1150 1200 1290 1900 mounted horizontally. Horizontal mounting of a U- shaped unit is desirable to permit draining of the fuel and coolant salts and to mtnimfre the possibility of xccumubtins crud in the heat exchanger tubes. In the proposal, the unit is mounted on trunnions to facilitate removal from the cell fc. repair or replace­ ment, in the unlikely event this is required. A rer >te pipe-cutting device is lowered into the ceO through an opening in the shielding above the equipment to cut the pipes connecting the exchanger to the salt systems. The exchanger is then rotated on the trunnions to a vertical 0 2 4 6 GmFHffE LIFE lytmt) position and lifted out of the reactor cell through an opening at the top of the ceB. This procedure b m§. ML At IT* reversed when installing a heat exchanger with the welding of this unit to the connecting pipes being done remotely. Pipe springback and alignment are major cons derations in the last step. Present remote welding technology1' indicates that the two end? of a pipe to 1.43 be welded must be aligned within %« in. J.R.McWherter W.K. Furlong HAMcLain J. T. Header W.Teny Studies were made of procedures for replacing the core moderator elements indniduaBy instead of replac­ 11. JmSH AuBUMI Frof. Rep, Aug. SI. 1970, ing the entire core assembly at one time as proposed in ORNL-4622, pp. 45-50.

L t^paittrt>kt-^ if^wai ^1—iiijn '\mm& t9ek*fmm * ->•••*• 15

1.5 MSBR INDUSTRIAL DESIGN STUDY Task I, the selection of a reference conceptual design, is essentially complete. Two progress reports were M. I. Lundui J. R. McWherter submitted. The subcontract12 negotiated between ORNL and The overall core size is the same as that in the ORNL the Ebasco Services group, consisting of Ebasco, reference concept,* but a slab-type graphite element is Babcock and Wilcox, Byron Jackson, Cabot, Conoco, proposed. Several of these slabs are held at the top and and Union Carbide Companies, was signed. This sub­ bottom in a hexagonal array as shown in Figs. 1.10 and contract covers the conduct of an industrial design 1.11. This assembly is sufficiently small to be handkd study of a 1000-Mr,*;c) MSBR plant. and replaced as a unit. One hundred fifty-seven such arrays are required for the core. A 2-ft-tbJck radial graphite reflector surrounds the core. A bocon-contahv ing thermal shield separates t2ae reflector from the 12. HSJt Awm Sfmimmt *ojr R*j, Feb. 29. 19?!. pressure vessel to redsce the radiation damage irniltim ORNL-4676, p. 36. from transmutatioa of boron m the Hastdoy N.

OMNL-MC 7i-«MS

Ft Ml. a—t Inli inlil ttta> amp—dpaahnta—jr - mm I - memm at atfdaajaa. 2. Reactor Physics

A. at Fny

2.1 MttEXRKMENTALPBYSiCS we ere tafc to indoor the tttf a\iil|i«|tflccaof the ___ iwr?ir>Tf y iht rod aaxtatt - which had to be 2,1.1 FTLTItLattieeExB«riBanti naahjctad ia iht putrii aitUna i Tot atuwoaiawi CURaaaa O.LSnwta wottte at 62TC Haw we ulithtii" afrwtod wonfar dharptnct.: front thoae aaaaafaai, bat partidt aeaf* Tfe* MM^ia^Mt^ ••«*•••• ^bw#0^d MM **^M*aa**aMW .»..»». _ _a» . . -.«_ - . m ,_ -» — _ « «... • •• csi^swBwiai pvnn^wjH, WKIMW m mmmi aHaMBBI etMCtS WOFt oajHCOMl HI tnOR aaacOKOlOQOOi fatal ia «* pnuiitM, jenwaanaal report,' hat now +,, baaa loaajlilii at tot aatteae Horthwett Labort- U oor niaraWoartoai, ite XSPIW coaV oo»oaai to ateaTMaV •Bt2fjMfttwfajBj£t*jfta_> fMfeflfe gjj^^^ ^M Gpjanpr AaajAf"ajnaajoa *^Mml^ aanrawaaaaBi J^A^ ••^••••••fffeflBMft «**-— ,*»«•.«•** «••«••••••*•» «•*•*•# ^Lk aut wapjaanaw •aoojOBjjaowaBBBBaa-OBjBja) wnw>ajw> BBJBBBBBW> aaa a^nennj «*a*a>*OBBiaBBB£ WBVOTJBH aWW CVw/OBv SVCQOoW 9Q( CBCaa ffVaaoOov w&TJwl wanTJw) wW 20, 300, 627, and lOOOTC. At cadi ptrfbna flrMprarf one^haowjoatl atatronJ NWL antied tht banc lattice aaoltioaV hUnai rriih ihi T Tia— nr authni" Tai canon factor *» and tht naUWty worth* of ton* 24 —r*rm ^ XSMW and hi thf ffTraVrftrtifnf a BrnftH the canter of a lattice that was K> Q^ dearee of aeteroameify par lenton, for < to a typical US** deafen pro- hitaajgnioai ran) root ahpowd hi a lattice mchoieaw mat certain am. a* haw MNT ajotjfto* tht GAM-U part of th* phywet caararteratici of toch a lattice aad to XSDCN coot to that it obtahi

a) oa^BhaaoBOi aa/najaajpan. an"aj o^paaaj ajaajjjB^ •aajok flH9DflBHflH£K CanSwauF SnTnTeflt* VOY

Tht attataatd aadtipwcacioa factor *•» varied from paMh hi nhlan Ihi ahnit —miina d fail mil any In 1J029 at TSTC to IJ004 at IOO0TC. Oar oaty precaka indaded. hied oafcjt (1.020 at 627*0 •» KoathliiaMy heater la its orhjhwi fena,4 GAhf-JJ yiehh d* Jaa*(i«#o« tht attacmd athw (IX»7 at 62TC), hat the Q) ruMdna daathy prr aait eaerfy Ft(el. Froai dat, ofll»aaaapaiaycaaaot»t ohtahuthehaap flax paraaet lethafay.

1. MM Aajra a fnaanin *njr. **+ K* 2M. 1971. OtPVhSTtVaf t4S-4t. 2.E.P.MPPI tcati, Bttajft NMtMM l^aecBOjoa*. paneaal 3. H. ML Gtfc3M arfCff. QPRM. if^ XXM* >• flr> oaaaaaacaaaa a>a L KOaaw Oak KJaat Wrtiail L+m* uix ftalitii Jhaeaaf ^laaaaaCaQj. 0ftMVThV2S« (Mr toy, riiihai IMfJi aaajr Itoaen. ABC Reedor DwUfim cad 4. a a tmmommtl.S.1>m+k,GAM-fi A*iCm+fm** Ti Jin Ian PMama* . Apt. Ma/, eai lea* 1*71. GtkukMom 0f Fmtltiwmvm J^paeaw midAtmetttfiitalHsfm^ HjnaVlS224. Cmmmtt. GA^)a5 gifimlw !9»3i.

16 17

F.{M) £F0(£) sectiom that mdude gram self-shielding effects. The tol") sane procedure s repeated for each thorium resonance, *,.•<«> S|.e<*>' as is custoniaiy with GAN-II. Instead of using the undated GAM-U treato** to wheie £ (£) is the total cross section is the Imp. f4 obtain grain shseklmf factors as ens 3one above, several These lesurts are nsade possMe by ehntaatiug explicit alternative procedures nary be used. Perhaps the un> leference to the exteraal (region 2) moderator by (I) pfcst of these is the NR upprrwunition, as jpplkd to asiuiriing that itfkM 1 sources are wd the grata. One ssmmrithMi* sources mtte by using the esyinptotk flux and the narrow i wel approxunsted by usmg nV ssynmtotfc fla* and the (NR) approximation fee then, (2) uung the flat-source pofenrJd scattering cross sections to calculate ovetafl escape wobobtttfci /«(«) and ^(u), and (3) - just as one assumes for the moderator in the invoking the ecJprodty theorem. With the SMM as- IGAftMl treutanent Thh leads to it can be shown that the region | flux is by ^-J^IMI-'SMI *• 'i>> Vt.nl") *r.o<«) '

#,(•)» I -/«(«) " *~ .

K4and F( andwrractionsl If *onfd be noted that we do not Here XL and £ , are the to be inuerfy the asymptotic %x> nor is the for the Ml # f> •o As fc

The revised GAftMl be used for al a doubt) the two degrees of walbe (MUM) The on the of theThO, pains in the foal of HTLTR The fed is first countered as and the CAnWI sohnmns tor dntjn) at the ••*•> nd «,(*) in the matrix aroond mem me •my osno enconmmmug a The fhutes ans ne #,(•)• I -ry«) -= = .»•***,(«) are then. rector is appfted to the cross factious of at each IrJhamv noaat Tenet dtandvnn> nvw wnwwnpa ewvmwenrnjgV/ m^pmnnw • uummun wjutnueunFvumjv are then taken to chnractertoe a I) foef within ant foci rods (any of the 14km 2) in a mttJce having graphite (any, region 3) be obtdued with the conwwter cone CAROL,* the rods. The GAM41 lirstmint is again selves exphcWy for the ueutionconneon donntim in peer the same hlhai|| band encempeseing the Caeostof m the earner GAftMl Now o&e performs for the given thorium sssonance the to

4, C A. Metvm sad C V 5. KM. fr tmmmmn Hnmrnc A Dww. Am. Nmd. Joe M. 3*4(197!). GA-4437 (Annul 1M5)I 18 approximations to be used in the analysis of the the GAM-ll treatment or (2) use a muhiregion code HTLT& experiments. such as EGGNIT * Procedure (1) was tried, but it was Numerous other approximate methods have been soon realized that a major obstacle in these approaches 7 r proposed. In a recent paper, P. Wahi dhcuues several is that expressions for the collision probabilities 00, of these and proposes one of his own that is somewhat /*0 ,, and ?0 3 are not available. (It was encouraging, related to the NRH4 approach Welti gives an example however, that approximate expressions §>ve results that involving a carbon matrix containing thorium carbide were dose to those obtained on the basis of the grains of 400ft diameter that occupy 10% of the assumed separability.) Efforts therefore turned to volume. We have used his problem to compare several checking the validity of the results obtained by as­ methods of obtaining grain shielding factors, with suming separability by comparison with results ob­ molts given in Table 2.1. Our results differ sbgrttiy tained using a transport method of solution for a from Watfs because we used slightly different reso­ selected problem involving a double heterogeneity. This nance parameters. Fluxes and flux ratios are given at work is still in progress. the peak* of the two lowest thorium resonances. *T jgrwwning of the Watt method and adaptation of 12 PHYSICS ANALYSIS OF MSBR CAROL to the IBM-360 were done by W. £. Thomas. 2.2.1 the MSHt Core J. it characteristics of the current MSR 21.7-eVi 23.4-eVi of a substantial fraction of the > #iO) #W*i *•<»> #iW «t/»i itrons in regions other than the core of the reactor. Besides the effect on the dynamics of GAM41 OJ 55 0.1542 0.73*1 O0754 0.1209 0.4234 the reaction in the core, the emission of neutrons MR 0.1*17 0.1544 0.73*3 04720 0.1174 04121 from orcubtiag rod slows a dumber of potentjaly llhi 0.1524 0.7323 0u0732 0.1 ltt 0.4144 it neutionic processes to occur in noucore 0.7323 OutlSi Computations were performed to estimate CAROL 0.11 It 0.1513 0.7392 041725 0.1145 0.4219 the and effects in the reference design MSBR of two out-of-core neutron processes: irradiation dan> age to the Hastefloy N structural material and neutron activation of the secondary salt. In general, two areas joined: the reactor outlet hnes where the sources are most intense and the primary heat Owe may have couAdeacr, on the bash of Table 2.1 where there is interaction with the coolant extensive studies of the same sort that out, that the use of GAM-ll to evaluate Delayed neutrons are emitted by at factor in a heieiogeneous fuel - as least 25 nuclides that have fission product precursors m our revised XSDRN code - is valid. with hatf-hves ranging from a smal fractiono f a second The results are very dote to those given by GAROL, to 55.6 sec. These precursors are normaly combined • an ahnost exact sohrtion. Not ouste so good, into six groups, and the net yield of delayed neutrons in each group is expressed as a fraction of the total neutron yield from fission. Data on die half-lives and On the other the .wjunwl separabmty of the yields of delayed neutrons are readiy avaNble for the of / certainly introduces s various fcssue materials. However, considerably less to be sijaificant. In material has been published regarding the energy the three dstmct regiom (caled 0, spectra of the delayed neutrons, particularly for neu- 1, and 3 above) simultaneously and either 0)1 tron energies above 1 to 2 hkV. Although relatively few

7. P. Wato. of Gam fhdtiai Factors far I.C1 Rickey, EGGNJT: A Htdttfovp Crots Section Code. FackCM** ScL Emj, 45,321-30(1971). BNWL-1203 (Honmka 194*/. 19

Table 2.2. Neutron activation processes in MSBR components doe to delayed neutrons

Helium production in 24 Ni inventory Tritium Component HasteUoy N in 30 EFPY in coolant salt production (ppb) 'Ci) rate c l0B(n.±f s8NHn.a)6 (Ci/day)

Heat exchanger

NaBF4-NaF 1.3 1-9 5000 0.03 7 Li}BeF4 (0.99995 U) 46 3-11 0.7 124 Li2BeF4 (natural L0 3.3 1-9 Reactor outlet line 7 8-40

'Based on initial' °B concentration of 2 atom ppm. *Range indicates effect of different assumptions for dehyed-neutron source spectrum. In the coolant salt high-energy delayed neutrons are to be expected, some ppb) have been found to significantly reduce the neutron capture processes are quite sensitive to the ductility of the standard (unmodified) aloy.1* high-energy neutron flux. Consequently, calculations Although che modified alloys are much less sensitive to were performed for two assumed shapes of the de- helium, the production rate remains of interest. For layed-neutron energy spectrum above 2 MeV. In one low-energy neutrons the principal source of heuum is series the spectrum was assumed to be flat out to 10 the iaB(n, a)7Li reaction in boron that occurs as an MeV, and in the second series the data below 2 MeV impurity m the aOoy. At higher neutron energies, the were extrapolated to zero at about S MeV. The first reaction stNi(«t, a)ssFe may also be important I assumption almost certainly overestimates the high- of the bigt nickel concentratBon in Hasteloy N. energy processes, and the second may also be con­ is evidence from high-flux irradiations of otJu servatively high. producing reactions (probably mvoiriag sequent*! nec- The intensities of the delayed-neutron sources were tron absorptions), but these are not Wu*y to be computed from a hydraulic modef' in which the significant at the low fluxes that wil exist outside the reactor was divided into 16 regions with fission-energy core of an MSR. Aside from hehum effects, KaafdsoyN production in 10 of them. Each region was treated as a is also subjsct to damage due to atom Jii|ilaMininli homogeneous vessel to compute the concentration of caused by neutron scattering events. ddayed-neutron precursors at its outlet, and the various The activation processes of interest m the secondary streams were mixed according to the flow distribution salt depend on the choice of nooiant With sodhnv throufcM the vessel. This led to s precursor concen­ fluoroborate, the principal activity is 15-hr 24Ma from tration for each tential neu- With tithhan-berylbum fluoride,th e several reactions tron-irradiation damage in HasteHoy N outside the core that lead to tritium production are of greatest interest. of an MSBR is the production of helium from (n, a) (Other activities are very short-lived.) Tritium pro- reactions. Very low helium concentratiom (as low as 35 duction was evaluated both for a ccohnt salt containing natural fthkim and for one in which the fctHmn it 0.99995 7U ComptaItow and unuiti. Afl the processes ascribed 9. R. C. Robertson, ed., Conceptual Design Study of m above were evaluated from cae-dimensional neutron Single-Fluid MoitenSSt Breeder Reactor. ORNL-4541, p. 47 transport calculations made vith tU computer r*

The \\Jues listed for helium buildup in HasteMoy N In the calculations, the effect of the assumed delayed- are based on an initial '°B concentration of 2 100 keV) were lower extended to 10 MeV. Since all of the helium values by factors of \..l to 1.3 than those that would be from s8Ni are quite low, the only potentially signifi­ encounter* * in a reactor spectrum with the same total cant difference produced by the shape of the delayed- flux above 100 k*V. Thus, the total number of neutron spectrum is in the reactor outlet line The metal-atom displacements produced in these compo­ results in Table 2.2 consider only the internal neutron nents by operat«on of an MSBR for 30 EFPY could be 19 sources - delayed fission neutrons plus these produced produced by irradiations io 2 to 4 X 10 nvt (E > 100 by fissions within the components. One calculation was keV) in a test reactor like HF»R. Although the total performed to estimate the effect of core-leakage neu­ number of atom displacements is not an entirely trons on the rate of helium production. The maximum accurate measure of metal damage (since it completely amount of helium produced in the outer shell of the ignores annealing effects), the low equivalent HFIR heat exchanger in 30 equivalent fuil-power years fluences suggest that damage by this process is probably (EFPV) was about 500 ppb, 80% from i,JNi(ii,o) not of major concern for MSR components. reactions. Thus helium production from co e-leakage neutrons may completely overshadow, at leas.' locally, 2.22 MSBE Nuclear Characteristics the production from delayed neutrons, unless appro oriate shielding is provided to reduce the fast-neuiron J. R. Engel flux from this source. Perturbation calculations were added to a two- The activation processes in the coolant salt were dimensioiial, ni^c-group diffusion calculation for the found to be essentially independent of both the core of the reference concept MSBE12 to provide high-energy end of the delayed-neutron source spec­ estimates of some of the reactivity coefficients of this trum and the incidence of core-leakage neutrons. The reactor Although these calculations are subject to 24N<, calculation is applicable only to the NaBF« refinement when a detailed core design is evolved, they coolant, and the value listed is the total steady-state serve to illustrate the kinds of values that may be inventory for the lOOO-MW(e) MSBR reference design. expected. The results are summarized in Table 2.3, The production rates of tritium in the various coolant along with previous!) published results for the single- salts are all much smaller than the rate of production in fluid MSBR.13 A prominent difference between the tho fuel salt (2400 Ci/diy). In the case of coolant MSBE va',tf£s and the comparable quantities for the containing natural lithium, however, the production in larger MSBR is in thr reactivity effect of fuel-salt the coolant is not negligible. density. In the MSBE the density coefficient is positive, The damage rate in Hastelloy N by atom placement so that voids decrease reactivity (-0.2% Sk/k for 1% was calculated for me highest f.lux regions in both the voids in the salt). This effect appears to be a con­ reactor outle ' ",1 the heat exchanger with NaBF4 sequence of the higher neution leakage from the coolant. Sir.ce u «utron flux spectrum outside the physically smaller MSBE core. Also significant is the core is quite different from any fission-reactor spec­ trum, the rate of accumulation of such damage was expected to be different also. Consequently, atom 11. J. D. Jenkins, RICE: A Program to Calculate Primary dtsplar./nent rates were computed using effective Recoil Atom Spectra from ENDFIB Data. ORNL-T4-2706 "damage cross sections'* evaluated by Jenkins.1' These ffeb. 14,1970>. crot* actions were obtained by explicit evaluation of 12. J. R. McWhtfter, Molten-Silt Breeder Experiment Design Bates, ORNL-TW-3177 (November 1970). the energy transferred Co primary recoil atoms and the 13. MSR Program Semimum. Progy. Rep. Feb. 28, 1970, Kinchb-Pease model for secondary atom displacements. ORNL4543,pv. 63-64. 21

Table 2.3. MSR reactivity coefficients 2.1 and 2.2 show the resultant heat generation rates in the graphite radially near the core midplane and axialry Coefficient Vihabk near the coe center line. MSBE MSBR OftNL-OVC 71-13MC Uranium concentration +0.33 +0.47 <**/*)/(* U/V) Thoiium concentration -0.38 (6*/ifc)/(*Th/Th) Fucl-^alt density +0.10 -0.04 (6*/Jt)/<6p/p) Temperature (6k/k)l6T,*C~l Fuel salt -7.3 X 10"5 -3.2 X 10"5 Graphite -0.7 X 10"3 +2.3 X 10"5 Total -8.0 X 10"5 -0.9 X 10"5 DISTANCE ABOVE CORE MIDPLANE (cm)

Fig. 12. Radiation hratmj n MSBE graphite Mar cove sot, negative temperature coefficient for the graphite in the ISO MW(t>. MSBE. This quantity combines with the salt density effect to produce a larger negative overall temperature 2.2 J Fixed-Moderator Molten-Salt Reactor coefficient in the MSBE as compared with the reference MSBR. H. F. Bauman The neutron nuxes and power densities from the We have extended the capability of the ROD code for above calculations were used to estimate the neutron the calculation of the lifetime average performance of and gamma heating in the core graphite by comparison molten-salt converter reactors with batch processing. At 14 with comparable quantities for the MSBR. Figures the end of a batch cycle, usually more uranium can be recovered than is required to make the reactor critical 0RNL-0WG 7-.-13365 with clean salt at the start of the next cycle. Therefore, we have added an option in the HISTRY part of ROD to permit the required portion of the uranium (as the mixture of nuclides present in the core at the end of the cycle) to be used for startup and the remainder to be fed in as required before extraneous feed (e.g., pluto- nium) is resumed. We hive also added a provision for changing from one extraneous fuel feed to another (e.g., from plutonhim to enriched uranium) at a specified thru in each cycle. Further, we have repro- grammeu the cost section of HISTRY to permit the calculation of tfr* present worm of all purchases of fissile, fertile, and carrier salt materials over any number of cycles at a specified discount rate. This method is more accurate for calculating cost* which change with time (e.g., the inventory cost, when the fissile inventory increases during 'He cycle) than the calculation of cots from data averaged over the reactor lifetime. (A 20 30 40 90 60 description ot the ROD code, incktding the foregoing RADIAL POSITION (cm) improvemeits, was pitbhshed daring this report period.1 *) The studies reported below used these new Ffr. 2.1. RadiafiM teatuif to MSBE frapMte lSOMW(t). calculations! nztko.it.

15. H. F. lain at st, ROD: A Nudmr ml Fm*Cyd* 14. tf*R htpmm Semirnvm. Prof. Rep. Aug. SI. 1969, Aimfym Code for Ckadtti^Fm} Rmeton, ORMUTIMtf* ORNL4449, pp. 63-67. 1971). 22

In previous reports we described the calculated process is inexpensive and efficient, but there :s ac performance of fixed-moderator" continuously present no economically feasible process for recovering processed molten-salt breeder reactors,17 and how a plutonium from the fuel salt.) None of the recovered reactor with core proportions optimized for breeding uranium is sold except that from the last cycle. Instead could operate as a converter using only batch process­ it a used for startup in the next cycle, with any excess ing.18 Based on these results we chose the reactor fed in as required as long as it lasts. We found that in described in Table 2.4 for further studies on the effects either case the calculated converfion ratio is high (over of various fissile feed schemes. Throughout these 0.90) so that 233U soon builds up to become the studies we held the processing interval fixed ai six dominant fissile material. Consequently, over most of full-power years (four cycles covering a 30-year life at the lifetime of the reactor the concentrations of the 0.8 plant factor). extraneous fissile nurlidcs are low compared with their The first calculations were intended to compare the concentrations for a shot: time after the initial startup. use of ptutonium and enriched uranium as the fissile Recognition of !hU situation caused us to reexamine material for the initial startup and as feed to supple­ one of the approximation* in the calculations, namely, ment the bred material. The plutonium feed compo­ that neutron energy spectra and effective cross sections sition was taken to be equivalent to that produced in do not change drastically over the time interval being water reactors (at. % 239Pu/240Pu/24IPu/*42Pu: considered. ftV24/I2/4); the uranium feed was assumed to be 93% The ROD-H1STRY computation takts an input set of 335 U. !n either case, we assumed that at the end of nine-group cross sections and generates a set of reac­ each cycle the uranium is recovered and the salt tion-rate coefficients (equivalent one-group cross sec­ containing the fission products and plutonium is dis­ tions) averaged over the reactor volume and over a carded. (Uranium recovery by the fluoride volatility neutron energy spectrum corresponding to a particular fuel composition. The program then uses these coef­ ficients to compute nuclide concentrations as a func­ 16. The term "fixed-moderate*" is used to indicate that the cote it (lfijtnrd to that the baiting fluence for fast-neutron tion of time and a new fuel composition that is the damage to graphite will not be exceeded in a 30-year nomt&al average over the time interval specified for the HISTRY leader life (24 equivalent fui-powex yean). calculation. This routine is iterated until the time- 17. MtSR Pro-am Semunnu. Prop- Hep. Aug. SI, 1970,average d composition agrees satisfactorily with the ORNL-4622,pp. 26-30. comp-ssition used in evaluating the reaction-rate coef­ 18. HSR Props'* Semkamu. fro*. Rep. Feb. 28. 1971. ficients. (The; same set o( nine-group cross sections is OftNL-4676. pp. 43-45. used throughout the iterations.) Of course, the changing fuel composition would actually affect the neutron imtlA. oftk«l«XUfW(e) energy spectrum so that the effective cross sections are not always exactly the same as they are when the fuel Core diameter overall, ft 28.5 composition is at the average for the time interval; the error involved in the calculation depends on how much Tnkkncat of core tones, ft the spectrum changes during the interval. Zonel 8.46 Zone 2 3.64 We suspected that for the reactors started on pluto­ Zone 3 1.97 nium a considerable spectnun change .-night be induced 0.14 by the effects of the kw-ly mg plutonium resonances. A Sdtvolmnefractk».t < typical set of nine-group absorption cross sections Zonel 0.137 prepared for our study is given in Table 2.5. Tut energy Zone'; 0.111 boundaries are shown in the table; groups I to 5 are Zone 3 0.127 stowing-down (fast) groups while 6 to 9 are thermal Total*** omam to fed qritem, ft9 2500 groups. The cross sections of *"U and a,,U are fairly 6917-M similar; starting up on "*U and shiftmg to 33,U, Past salt, mole % UF4UFt-TW4 Com mail owthtt frymtmm,'? 1050-1300 therefore, would not be expected to greatly change the reactor neutron spectrum or the fueJ-nuchde react on mm.MwXt) 2250 rates from those calculated fot the lifetime average. Hw te "*fu cross sections, on the otter hand, are very nvch 307*ar In (or the higher in thermal groups 7, S, aed 9. This high cross JCC-201). section stakes prntoeJum a very reactive fuel, with tow 23

TaUr23. Tjpkaii

Votes**

Grovp i 2 3 4 5 6 7 8 9 Lower bouaibiy, eV 821,000 31,800 1230 47.9 1.86 0.768 0.140 0.060 0.0047 Absorption cross S6CQ0O. osms "2Th 0.2 0.? 1.0 3.9 2.3 0.6 1.8 3.4 6.3 "Ju 2.1 2.6 7.' 2S.0 134.0 318.0 177.0 266.0 491.0 "su 1.4 1.9 6.1 31.0 66.0 49.0 17S.0 270.0 560.0 "»Pu 2.1 1.9 4.1 35 0 74.0 4!.0 2110.0 ?67.0 883.0 I4% 1.9 0.7 2.2 27.0 21.0 7114.0 189.0 159.0 242.0 M,f» 2.0 3.0 6.1 31.0 1*2.0 20.0 1149.0 850.0 1155.0

critical loadings in reactors in which the flux is well use of a lifetime-averaged fuel composition in deter­ thermalized. However, when recycled plutonium con­ mining the reaction-rate coefficient entails unacceptable taining much 2*°Pu is the principal fuel, the high error when applied to the plutonium startup cases we 24*Pu cross section (group 6) tends to depress the had been considering. thermal flux, hardening the spectrum and increasing the However, the reaction-rate coefficients for the eii- critical loading at tissue material. Over the lifetime of a riched-uranhtm startup case changed hardly at all, and molten-salt converter reactor that is started on recycled lifetime-averaged coefficients appear to be entire1./ plutonium out soon has much 333U and little ptuto- adequate for these calculations. m'um in it, the effect of plutonium on the neutron The changes in self-shielding of the pNtfonfcuu of a energy spectrum might be expected to range from quite phitonium-fed molten-salt converter reactor are great important to rather slight. Reaction-rate constants enough to affect the calculation of the nine-group cross appropriate for the low lifetime average concentration sections also. To evaluate the significance of this, we of phitoniun are therefore likely to be seriously hi calculated a set of nine-group cross sections for a error at the start of life when the plutonium concen­ reactor containing about 1000 kg of fissile plutonium. tration may be over ten times as high. (The asymptotic fuel composition used previously in Our calculations had used ? set of nine-group cross calculating nme-grcvp cross sections included less thai sections appropriate for a fuel composition close to the 100 kg of fissile plutonium.) This set %r% then used m lifetime average and had computed reaction-rate coef­ HISTRY to calculate the first ym of operation, ficients for the lifetime-averaged composition. Our first evaluating reaction-rate constants for the average com- test was to recalculate the first full-power year of position during the year. Results are shown in column 3 operation for both the uranium-fed and the pluto- of Table 2.6. The effective thermal cross sections for niunvfed converters, ustog the same nine-group cross the plutonium nuclides in the resonance groups was* sections as before but having HISTRY evaluate reac­ considerably lower in this set. The spectrum-hardenag tion-rate coefficients for the average composition for effect was therefore not as great, and the reaction-rate the first year rather than for the average over the coefficients were not as greatly depressed as ?hr,y were reactor lifetime. Some results of the tv> computations in case A32. Compared to case A24-2, however, the are lifted in the first two columns of Table 2.6. The coefficients are low, and the critical leading are much most salient point is that ih» calculated fissile loadings higher. for the phitonhinvfed reactor differ by a factor of 4 Prom the above considerations we "cadude that between two computations in which the only differei** previously reported calculations for cosierters started is the interval used in evaluating tie reactton-.ate on phitonhim,1* whle well repretenting the asymptotic constants. This is because the plutonium concentrations portion of the feed cycte, do not adequately represent during the first year, being much higher than the the startup condition in which phrtonium it the lifetime average, cause more flux hardening and de­ principal fusfle material The error involved hi time pression of the reactkMMf te coefficients. Obviously the calculations will be minimized in future calculations ni 24

Fuel composition Asymptotic* Asymptotic* HsjnPu"

cross sections Intern! for; Lifec First year47 Fusty*** oomposftkm for reaction coefficient calcolatioo Pmtooium-fccd cases Identification A24-2 A32 A33 Reaction coefficients* 1.0 1.0 1.0 233y 5.9 3.5 3.9 "*Pu 24.3 9.3 1&2 24#Pu 14.8 9.8 li5 24IP» 1S.8 8.2 8.6 a42?u 1.9 2.6 2.9 Inventoriek at end of first year,0* kg "3u 451 235 303 "»Pu 559 4190 2621 241Pu 366 1263 996 Total 1376 5688 3920 Uranium-feed cast Identification A21-1 A34 Reactkm coefficients' "aTh 1.0 1.0 6.06 6.15 5J1 5.58 "»Pu 25.5 26.0 Inventories at uni of first yea?,'' kf 233y 649 644 «5u 1683 1664 239p* 3 3 Total 2335 2311

*Compositiun cotrespondinf approximately to nd of life m case A24-2 (fot pmtonmni-feed case?) or in case A21-1 (for uranium-feed cases). ^Composition corresponding to highest fissile phitonwm concentration* in A24-2: 762 kg 23*Pu, 228 kg Mx Po. c24 equivalent roll-poweryears , with processing at 6,12, and 18 EFPY. ^First equivalent full-power year of firstcycle . 'Specific neutron absorption, normalized to 332Th. 25 which ROD-H1STRY averages fuel compositioos over the optimum, converter reactor designs to much shorter intervals. It is evident, however, that wehV4hermahxed core frax spectrum. measures to maintain a wett-ttsennahzed flux s.ectrum The results of the enridsed-vranium feed case shown wfll probably be require4 to use recycled piutonum in Table 2.7 indicate that very good perfonnaace can be effectively for the startup of higb-perfornance thonum- obtained from the breeder reactor operated as a 233U converter reactors. converter with batch processing. The changing fuel We are continuug to study phuomum startup, with composition over the reactor lifetime is shown in Fig. the object of reducing the initial tissue loading. One 23. The cxmversson ratio of over 90% is good for a method would be to increase the moderator ratio by reactor processed only every six years. The fuel coat of simply lowering the thorium concentjatioc in the about 0.76 naWkWhr exdudmg processing is attractive. reactor that we hive been studying. In addition, we The cost of processing and disposal of the spent fuel has plan to study reactors designed specifically as phuo- been roughly estimated to add about 0.1 mnVkWhr to nhinvfed converters (in contrast to the reactor stadied &s cost. The nigh SsiSe inventory cost relative to the thus far, whose core characteri *ics were optimized for burnup cost suggests that a lower thorium concen­ breeding with continuous processing). We would expect tration would give a lower overall fuel cost for a reactor designed specifically as a converter. This would result in a tower tissue inventory at some sacrifice in conversion ratio.

2000 n-mer Casr identification A2M Feed material pnr<-*>*9ed MOO Initial toading, kg fissfle 2430 Lifetime purchases, kg fimk 3599 Recovery at end of life, kg 1600 233 U 1950 *»u 23S U 381 1400 Net Kfetaae requirements^ kg fissile 1268 Lifetime avenged conversion ratio** 0.946 Fad co»ts,e mflls/kWhr 1200 Inventory Fissile 0.566 Salt 1000 0.051 Ul Salt reptacement 0.092 > Fissile burnup 0.054 800 Total 0.763

600 *Reactot described in Table 2.4. Salt and plutoaium dis­ carded and uranum tea «red at end of four sk-EFPY cycles. Recovered uranium used for startup and feed in next cycle. 400 *93% enrichment. ^Lifetime purchases less fissile uranium recovered at end of last cycle. 200 'Net, taking into account discard of phttooium and neglect­ ing any toss of uranium in each processing cycle. 'Excluding processing ccsts. Obtained from present-worth calculation of fissile, fertile, and carrier salt purchases and fissile sales over life of reactor, with discount rate * 0.07 year'1, compounded quarterly, aad inventory charge rate * 0.132 233 ve*"1. Values of 11.9 $/g"$u> 13* */» U,and9.9S/gfia- Fit, 2 J. Fad smdMft inventoriM tot sik plutonium were assumed. A2M. 3. Systems and Components Development

Dunlap Scott

3.1 GASEOUS FISSION PRODUCT REMOVAL and were representative of the size generated. The test fluid was changed from the water-glycetoi mixture to a C. H. Gabbard 31% CaCl2 solution in hopes of avoiding the very small bubbles while maintaining hydraulic similitude, but 3.1.1 Gas Separator and Bubble Generator little or no difference was observed. A gamma radiation densitometer wz?, installed on the The testing of the bubble separator continued in the water test loop to measure the separation efficiency water test loop.1 Tests were conducted to learn more under several conditions of operation. We measured the about the formation of the very fine bubbles that were performance of the separator with the large bubbles in encountered with the water-grycerol test fluid and to demineralized water and with the small bubbles in the evaluate the separator performance with these small 31% CaCl2 solution, and the results ate shown in Fig. bubbles. Although much of the available evidence 3.1. The effect of bubble size on the performance of indicates that the bubbles will be larger in molten salts, the bubble separator was also demonstrated by a the large changes observed in the emulating gas content dilution experiment starting with the 31% CaClj of the MSRE fuel salt suggest that the bubble size might solution. Figure 3.2 shows the results of tiiis experi­ vary over a considerable range. The development of the ment. As the concentration was reduced, a sharp bubble separator is therefore proceeding on the basis of increase in separation efficiency Indicated the point removing the small bubbles with the best possible where the bubble size increased as i result of coales­ efficiency. cence. The coalescence transition occurred at a concen­ A series of t&ts with glycerol was completed which tration of about 2.7 wt %, which is considerably greater shows that the liquid circulation pump was the source than the 0.61 wt % reported in recent literature,2 but of the very small bubbles and that the bubble size was this difference could be caused by other additives in OIK related to the pump head or speed. It is probable that test solution or by the grossly different hydrowynamic small bubbles formed in the pump during the operation conditions. These tests suggest that the size of bubbles with demineralized water coalesced to a larger size circulating in a reactor system will be determined by before reaching the separator, while the bubbles formed the hydraulic design of the pump and circulating system in the glycerol solution were inhibited from coalescing and by the coalescence properties of the fuel salt.

2. R. R. Lessard and S. A. Sienunski, "Bubble Coalescence 1. MSJt Protram Semkamu. Prop. Rep. Feb. 28, 1971,and Gas Transfer in Aqueous Electrolytic Solutions," fnd Eng. ORNL-4o76,p 49. Chen, Fundant, 10(2), 260-69 (May 1971).

%

T"l 27

f 3 OMH.-MS 71-102J1A of the cental core rosn the annular recovery hnb resulted in satisfactory vortex s?absbty over the ru! jets fkm range of 0 to 6 scfm Wh*n open^ in this manner the gas void diameter r oetween % and % ML depending on the gas flow rate. Efficiency tests are currently in progress for this mode of operation.

3.1.2 rhrtthrr Fnr—tinn i ml Ptiatriuaii Tut

A fast has been planned to compare the bubble formation and coalescence properties of molten salts with those of demmerahzed water and other fluids. The test will consist of mechanically agitating a sealed quartz capsule of the test fluid in a special furnace and photographing the capsule to show the size and

2 3 4 behavior of bubbles of gas in the liquid during and after GAS MPUT RATE (scfm) the agitation. The design of the test rig is nearing completion. FQ. 3.1. Peiforaaace of 4-ia.-ID standard fcLfth babbie separator at 500 gpss. 3.2 GAS SYSTEM TEST FACILITY R. H. Guymon 0NNL-W6 7I-I30S 100 ._, The gas system test facility (GSTF) is a loop for circulating a fuel salt typical of the MSBR foe use in 90 \ \ developing the technology of components to be used in • the primary system of a molten-salt reactor. The > 80 performance of bubble generators and bubble separa­ u 1 tors, being developed initially in a water loop (see Sect. I 3.1.1), will be tested, along with components for I" ^—GAS REMOVAL purification and recycle of off-gas. Other tests include V H) • ^ EFF OtNCY determining the effect of the UF3/UF4 ratio on the 60 surface tension of the salt, studying noble gas and • possibly tritium distribution, and measuring heat aw 50 mass transfer coefficients. The conceptual system de­ 1.0 1.1 1.2 1.3 4 5 SPECIFIC GRWITY sign description (CSDD) and the quality assurance for the facility weie published during the period. The faculty, shown schematically in Fig. 33, will be Pig. 3 J. Results of bubble coalescence test with CaCl2 solution at liquid flow rate = 500 gpm and gas flow wte = 5.15 located in the enclosure previously occupied by the scfni. molten-salt pump test stand in Building 9201-3 of the Y-12 plant. The loop is of 5-in. sched 40 Hascelloy N pipe, much of which was removed from die MSRE coolant system. Molten salt at 1050 to 1300°F is pumped at 1000 gpm and 100-ft head by the MSRE The distance between the swirl vane hub and recovery hub of the test separator was increased from 27 to 44 in. to achieve the greater vortex length required to 3. MSR Program SemUamu. Progr. Rep. Feb. 28.19/J, C RNL- sepzraie bubbles from higher viscosity fluids. The 4676, p. 49. separation efficiency was improved substantially at low 4. W. K. Furlong, Conceptual design Description of the Molten-Salt Loop for Testing Gas Systems, ORNX CF-71-1-40 gas flow rates by lengthening the separator, but a vortex (Jan. 25,1971Xfor Internal use only). instability limited the gas remov-il capacity to below 1 5. R. H. Guymon, Quality Assurance Propam flan for the scfm. Similar results were obtained with a long separa­ Gas Systems Technology Facility, ORNL CF-71-7-6 (July 6, tor having a tapered outer casing. However, the removal l971)(for internal use only). INSTRUMENT PfN€TRATIONS VIEWING SURVEIL­ PORTS LANCE STATION

STACK

Ra. 3^. Gas syttem teduntoty facflity.

Mark z pump modified as described in Seci 3.7.1. A at the end of the period. Initial operation is scheduled line downstream of the pump allows part (approxi- to start in the Ml of 1972, using coolant salt from the izstefy one-halO of the flow to bypass the main loop. MSRE to establish a base line for later operations. After The main loop flow goes through a flow-measuring preliminary experiments and shakedown tests are corv venturi (from the MSRE), a bubble separator, an1 a plete, this salt will be replaced with a salt similar to the bubble generator before rejoining the bypass flow and fuel salt projected for the MSBE. returning to the salt pump. Helium is injected at the bubble generator and flows 33 OFF-GAS SYSTEMS around the lc

3.3.2 CamputerDestjnofOkttccelBeds of the second dependent on the results of the first. tar MSR Off-Gas Systems First, the selected firm wul assess the feasmiity of molten-salt steam generators using feedwatcr tempera- The design of charcoal beds for the dday of fission tuses between 500 and 600°F. He will investigate both product gases in MSR off-gas systems involves an subcritka! and supercritical pressures. If the feaabiity iterative ;:akubtion best handled by a digital computer. assessment is affirmative for one or both of die above Existing computer programs, which were used for the pressurr* and if ORNL agrees, •hen the industrial firm Homogeneous Reactor Test and the Mohcn-Sah Reac­ will prep ve conceptual desytis fcr steam generators tor Experiment, are arranged to calculate charcoal using these conditions and the sah system conditions of temperatures end isotope exit concentrations and, as Task!. such, are insufficient to be of maximum usefulness to Task Iff - conceptual design of a steam generator far the charcoal oed designer. A computer progr i is a motor-self reactor of about 150 MW(s). ORNL will seeded which includes cost and other selected parais- select a steam generator conceptual design from the ete s and which furnishes data necessary for "nechanical results of Tasks I and II. Then the industrial firm vnH design. A study b hang made to determine how the adapt this concept to a mohen-salt reactor system of existing programs might be revised and enlarged to about ISO MW(t). achieve such a program. Task IV - description of a research and development program for Task III steam generator. For Task IV th? 3.4 MOLTEN-SALT STEAM GENERATOR industrial firm will describe the research s'jd develop­ ment program necessary to assure that the design of the J. L Crowley R. E. Helms Task III steam generator is adequate. \s part of tins task the industrial firm will fevfew ORNL's proposed 3.4.1 Steam Generator ladvotriel Program steam generator tube test facility and die associated Proposals were received from four of the eight program and will also review the program of testing industrial manufacturers of steam generators that re­ Hastelloy N and other materials in steam. ceived the request-for-proposal package. An evaluation We hope to have Task I conceptual design completed team studied the proposals and selected the Foster during FY 1972. Tasks II, III, and IV would be Wheeler Corporation. A subcontract is being negotiated completed during FY 1973 or early in FY 1974. with them. The scope of work requested of die industrial rum 3.4 2 Molten-Salt Steam Generator TedmotoftyFacatty was revised from that reported previously.6 The Work continued on the preparation of a conceptual changes basically involved limiting the industrial firm to system design description (CSDD) for the steam gene­ work on the steam generator and excluding the systems rator technology facility (SGTF).7 This fadL*/ would design work originally requested. Although Task II was be a side loop of the coolant-salt technology facility most affected by this change, a brief description of aO (CSTF)8 and would be used to study transient and four task* follows. steady-state operation of some full-length tube test Task I - concept**! design of a steam generator for sections and portions of a tube teat section of a the ORNL 1000-MW(e) hRBR reference steam cycle. morten-salt steam generator. The teats performed in tint The firm will produce a cot:cepturl design of a steam facility would better define some of the technological generator to operate with the salt and steam conditions uncertainties to be investigated later with a larger of the MSBR reference design. The industrial firm will rauMtube test facility (STTS). The SGTF would be consider alt aspects of a conceptual design, including used to: uni: size, control of steam temperature, and unique support systems such as a startup system and a sah 1. investigate some of the problems of geneming steam circuit pressure relief system. using sodium rraorobonrte and fcedvuter at various Task II - feasibility study and conceptual design of temperatures up to 700*F; steam generators using lower fetdwater temperature. This task is divided Into two parts, with oV* execution

7. JOR fragmm fiaaaima. hear. «m M 2*. 1971. 6. MM freamm Smmnmm. Avar. He* Aug. SI. 1970. OMu>«7t\e,S2. OftNL4*22,p.40. w* w*mm\% P* 9om 30

2. perform heat and mass transfer tests in various steam pressure equal to or greater than 3600 ^sig at 1100°F generator tube configurations; «vere selected from Table 3.1. These tubes were 3. investigate the use of thermocouples, strain gages, subjected to further study. and flow elements in a molten-salt environment A heat transfer program was written to calculate the typical of larger test facilities such as the SITS; salt and supercritical water/steam temperature profile for the tube-in-tube molten-salt steam generator test 4. study flow stability in a single tube and the ability section. The program calculates the steady-state heat of orifices to eliminate any instabilities for load transfer, steam pressure drop, water/steam temperature, changes in the range of 20 to 100%; salt temperature, and temperature difference across the 5. explore some of the problems associated with the inner tube for a finite element length of test section. detection of a steam-to-salt leak and the venting of The salt temperature (TFI), the inside wall temperature resulting pressure; of the inner tube (TWI), the water/steam temperature (TSO), and the temperature drop across the inner tube 6. obtain operating data on a scaied-down version of a wali (DTW) ~s a function of test section tube length (ft) startup system. are then displayed by the Calcomp plotter as shown in 3.43 Morten-Safe Steam Generator Test Proposals Fig. 3.4. The inner tube inside diameter (DI), the inner tube outside diameter (DO), the outer tube inside Morten-salt steam generator test configurations are diameter (DM), the outer tube diameter (DIO), the being considered for test in the SGTF and the STTS. total heat transferred (kW), the salt flow rate (WF), the To date studies have been made on several tube-in- steam flow rate (WS), the inlet pressure (psia), pressure tube configurations in which supercritical water flows drop (psi), the finite element length (ft), and the date vertically in the inner tube countercurrent to an are printed by the Calcomp plotter above the curves. unbafffed salt stream in the annuhis between the inner Using a feedwater flow rate that would produce 20 and outer tube. To select an inner tube wall thickness, a fps and a salt flow rate of six times the feedwater flow computer stress analysis program was written to calcu­ rate, the outer tube was sized to give salt velocities of late the internal working pressure that would produce a about 20 fps. Preliminary results of calculations for total primary phis secondary stress intensity of 13,000 seven tube-in-tube steam generator configurations are psi at 1 »00°F. The allowable stress intensity of 13,000 shown in Table 3.2. For full-length tubes that receive psi at 1100°F meets the requirements of Section III of 700°F feedwater and produce 1000°F steam, only the the ASME Code and Code Case 1315-3 for HasteUoy N %• and the %4n.-diam tubes could be tested in the material. The results of these calculations are shown in 150-kW SGTF, while larger tubes would be tested in the Table 3.1. 3.0-MW STTS. Sections of larger tubes could be tested Seven tube sizes ranging from % to 1 in. in diameter in the SGTF but not for full inlet and outlet steam in steps of % in. and having an allowable working generator conditions.

T*J*t 3.1. Mi •e for Hatfdky N tabic* n steani feaen-ton aM 100°F

TnbeOD Maximum pressure (psff) fir tut* wall thickness (in.) of - (m.) 04350 04490 0.0650 04830 0.09S0 0.1090 0.1200 0.1340 0.1480 0.165 0.180

0.2500 3180.4 4097.2 5002.4 57*6.2 6125.6 63934 0.3125 2585.9 34374 4283.1 507U 5501.2 5905.6 6240.0 6368.2 6481.9 0.3750 220O2 2953.4 J725.5 4481.0 4918.0 5360.7 57774 5978.8 62114 6406.4 «*98.8 0.4375 19154 2588.4 3292.1 4000.3 4423.4 4867.6 53094 5527.9 5823.3 6116.3 6347.2 04000 10924 229k 3 2545.6 3599.5 4001.4 4432.4 48754 5100.6 «1!8.0 5748.6 6068.6 0.5125 1054.3 2248.2 2379.3 3588.8 3926.1 4358.7 4794.8 50204 5349.0 56754 59974 04250 13744 18784 24224 2994.3 3351.3 3743.6 4160.0 4379.2 4698.9 5051.9 5418.0 0.4*75 1250.3 1721.0 22254 27054 3096.3 34684 3*074 4079.9 4392.2 4742.4 5113.7 0.7500 i 156.7 1587.7 20584 J558.9 2870.2 32294 36IU 3815.4 4118.2 44614 48314 0J750 99S.4 13744 17884 2232.3 2510.4 2835.4 3183.7 3371.9 3653.9 3978.3 4334.9 14600 870.1 12)14 1580.1 1978.9 2235.3 2525.1 2843.7 3017.1 32784 35811 3920.1 31

ORNl-OWG n-45138 3.5.1 lnspectioa of PKP Ponp Rotary FJeaK«t

01 (in.! 0*45 KW 149.58 INLET PRESSURE 380000 The impeller and upper imp*U*r housing (see Fig. 3.S) DO (m.5 0.?'5 *F 4812.00 PRESSURE DROP 101.06 were removed from the PKP pump rotary element, and Oil do.) 0.43-1 *S 80200 ELEMEM LENGTH (fi) I.OO DlOvin? 0.62'J N8 2 DATE 8-30-71 the upper labyrinth seal ring and the heat baffles were removed from the impeller housing. All parts were then examined visually after washing with hot water to

remove residual deposits of NaBF4 salt. The following is a summary of our findings. 1. The vanes on the back side of the anpeUer and the grooves inside the upper labyrinth seal ring showed tittle sign of wear, based on the appearance of sharp edges and corners. 2. The diameter of the stinger ring appeared to match the curvature of the high-nickel, gray-black lumps previously described.' ° 3. The appearance of the inner heat baffle plates was markedly different from that of the outer heat brfle plates. Except for a slight blackening of the surface*, the outer plates suffered very little attack. On the other hand, the inner baffle plates (see Fig. 3.6) had been severely attacked as evidenced by holes completely through in some places and by severe pitting in other places. The attack was not homogeneous on any one 0 5 10 15 20 25 30 35 plate or from one plate to another. The top surface cl" TUBE LENGTH (ft) the top plate was severely pitted, but the other surfaas which combined to form the chamber above the top Fig. 3.4. Tiibe-in-tube molten-salt steam generator test sec­ plate (shaft, inner surface of impeller housing support tion. cylinder, and lower surface of the cooling ofl chamber) were relatively free of attack. All baTle plates except 3.5 SODIUM FLUOROBORATE TEST LOOP the one below the top plate bad holes corroded completely through. The inner heat baffles fitted very A. N. Smith tightly against the inner surface of the upper hnpeUer housing support cylinder, so that probably most of the The as-removed appearance of the PKP pump rotary gas flow was past the inner annuhis between the baffle element and the appearance of certain other test loop plates and the pump shaft. components were described in the previous report. During this period, the pump rotary element was 4. A groove was found in the surface of the pump dismantled, and the component parts were examined shaft at a point adjacent to the inner heat baffles. The groove was about % in. wide and about % in. in visually after washing with hot water. Except for the maximum depth. It was smooth in contour and was not inner heat baffle plates, the appearance of tie Inconel pitted. metal surfaces was such as to imply insignificant attack during the fluoroborate service. The inner heat baffle 5. Metal surfaces had a coarse, grainy appearance but plates were badly corroded, and their condition was were not severely pitted except on the inner heat baffle attributed to corrosive material produced by the reac­ plates. tion of moisture in the incoming purge gas with puddles 6. Contrary to pump assembly drawing F-2882-K, of salt which were left on the baffle plates during the there were no holes in the impefler bousing support irgasting transients in May and J'jne 1968. More cylinder jus! above the inner heat baffles. The detailed information on observations and conclusions resulting from examination of the rotary dement parts is presented below. No further work is planned on this 9. A.fl.SmXk,Exp*itnc* with Fktorobonu Cktwktkm * 9 m MSREScak Loaf, ORNLTM-3344 (to bt IHIMH ft. test program. A report is being prepared summarizing 10. HSR Aajw Stmfmm. fro*, jbm Pek Z9. 1971. the work on the sodium fluoroburate test loop. OftNL-467f, p. SS. 32

Tabk- 3.2. Results of calculations for test sections operating with salt and feedwatei velocities at 20 fps

Test section number 1.20.1 2.20.1 3.20.1 4.20.1 5.20.1 6.20 1 7.20.1 OD of inner tube, in. 0.250 0.375 0.500 0.625 0.750 0.875 1.000 ID of inner tube, in. 0.152 0.245 0.334 0.407 0.510 0.579 0.640 Wall thickness of inner tube, in. 0.049 0.065 0.083 0.109 0.120 0.148 0.180 OD of outer tube, in. 0.375 0.625 0.750 1.000 1.125 1.250 1.500 ID of outer tube, in. 0.319 0.495 0.666 0.810 0.995 1.152 1.310 Wall thickness oi" outer tube, in. 0.028 0.065 0.049 0.G95 0.065 0.049 0.095 Inlet feedwater temperature. T 700 700 700 700 700 700 700 Outlet steam temperature, ° F 1001.6 1008.9 1001.4 1002.1 1002.1 1002.2 1002.2 Salt outlet temperature, °F 850 850 850 850 850 850 850 S«U inlet temperature, °F 1144.1 1145.8 1143.1 1142.4 1141.6 1140.6 1139.4 M:ixhnum temp drop across inner tube wall," F i32.9 i46.3 15*,4 174.4 176.6 185.3 191.9 inner tube wall temp at maximum &TW 798.0 796.0 790.4 787.9 787.4 787.4 787.8 Feedwiter flow rate, lb/hi 309.0 802.0 1491.2 2214.8 3483.0 4488.6 5469.8 Salt flow rate, Ib/hr 1854.0 4812.0 8944.2 •3,288.8 20,898.0 26,931.6 32,818.8 Maximum allowable working pressure for inner tube at 1100°F 4097 3725 3600 3743 3611 **54 3920 Water/steam pressure drop, psi 73.0 95.6 109.9 U2.6 14A.9 164.2 187.4 Tube or test section length, ft 16 33 53 76 106 139 176 Total heat transferred, kW 56.1 146.5 270.0 400.2 627.9 806.7 980.5 Heat transferred to point of max temp drop across inner tube wall, kW 28.5 81.5 141.0 212.0 33*7 442.6 572.4 Distance from inlet to position of maximum tubs wall AT, ft 6 17 28 n 58 78 101

of these holes means that all of the pump shaft purge purge gas was in intimate contact with the puddles of gas had to flow past the five inner heat baffle plates in salt, and the moisture in the purge gas, estimated to order to get to the main part of the pump bowl. have been somewhere between 1 and 20 ppm by We have drawn the foMowing conclusions from these volume, combined with the puddles of salt to form observations: reaction products which corroded the adjacent metal 1. Except for the inner heat baffles, corrosive and surfaces. erosive attack was slight, which is consistent witn 4. The degree of attack on the upper baffle plates observations made of pump bowl surfaces.l ° was at least as severe as that on the lower baffle plates. 2. The high-nickel, gray-black lumps were formed by If we assume r. significant temperature gradient between deposition on the surface of the slinger ring, probably the bottom and top plates, the implication would be by precipitation of corrosion products on the cooler that the water-salt reaction products are highly corro­ shaft surface as was discussed earlier.1 ° sive even at relatively low temperatures. Direct measure­ 3. The severe heterogeneous attack suffered by the ments of the baffle plate temperatures were not made, inner heat baffles came about in the following manner. but it is estimated that the temperature of the top

NaBF4 salt was forced into the baffle region during the baffle plate was 500°F or less. Additional tests are iiigassing transients in May and June 196&.1' Scattered needed to determine the variation of corrosiveness with puddles of salt were retained on the baffle surfaces temperature, since there are important general implica­

because the latter were not perfectly flat. The incoming tions for reactor systems using NaBF4 For example, efficient cleaning procedures will be needed to ensure

that Na£F4 s*lt residues are not left on the outside surfaces of pipes and equipment where exposure to 11. MSR Program Semiannu. Prop. Rep. Aug. 31, 1968, ORNL-4344, pp. 76-77. moist atmospheres is probable, and where Uie metal

; : :: : :: *Y

, 33 temperature is high enough to that corrosion would be caused by material, presumab y a mixture of salt, metal, significant. and corrosion products, which became wedged between 5. The groove in the pump shaft was apparently the shaft and one of the inner h;at baffles.

ORNL-DWG 71-13.39

3 NOTE: IOC cm />nin. 1 TEMPERATURE OF SALT IN PUM* TANK WAS NORMALLY 1025 "F

2 THICKNESS OF HEAT BAFFLES WAS 0.032 in. EXCEPT TOP ONE WAS MA!N <"!_ANGE 0.067 in. A 0.065-in. SPACER WIRE WAS USED BETWEEN B^CFLES

COOLING CIL PASSAGES

GROOVE FOUND IN SURFACE CF SHAFT APPEARED TO BE CURVED IN CROSS-

SECTION AND ABOUT V,6 io. WIDE BY ABOUT V in. MAXiMUM DEPTH PUMP TANK e APPARENTLY CAUSED BY MATERIAL WEDGED BETWEEN HEAT BAFFLES ANO SHAFT

FOUR ^-in.-iiCT. WEEP HOLES -JLINGER RING SIX 'A-in.-diam WEEP HOLES

UPPER LABYRINTH SEAL RING

PUMP SHAFT

WINDOWS (ZV» in. WIDE BY lV2 In. HIGH) TO PERMIT FOUNTAIN-FLOW NORMAL SALT SALT TO FLOW BACK TO MAIN PART LEVEL IN OF PUMP TANK (TOTAL OF FOUR) PUMP TANK

-lOF VOLUTE

UPPER LABYRINTH SEAL LEAKAGE (FOUNTAIN FLOW)

VOLUTE

«_ OF 3-in-diom PUMP SHAFT

Fig. 35. Crow section of PKP pomp. NaBF4 circulation test, PKP loop, 9201-3 34

PHOTO 78671A

NOTE: SEMI-ClPCULAR NOTCHES IN PERIPHERIES WCRE MADE DURING REMOVAL OF BAFFLES FROM PUMP

cLLER ENO

MOTOR MOTOR ENO ENO

Oi 23456789 10 11 12 1 , I • I . I • I , I • I . I • 1 • i . 1 . I . I INCHES

Fig. 3.6. Innei heat baffles from PKP pomp snowing posttest appearance of upper surfaces. NaBF4 circulation test, PKP lcop, 9201-3.

3.6 COOLANT-SALT TECHNOLOGY FACILITY provide: (1) a quiescent liquid surface of sodium A. I. Krakoviak fluoroborate representative of the main loop, (2) operation at constant temperature and salt level in the The rmechanical design of the coolant-salt technology vessel, (3) salt residence time of approximately 30 sec, facility is nearing completion. The design now includes (4) on-line removal, insertion, and adjustment of depth two side-stream loops and a specimen surveillance of immersion of the electrode, and (5) visuai access to station. One of the side-stream loops supplies salt to a the gas-liquid-electrode interface. corrosion product trap to investigate on-line removal of Fabrication of the drain tank and the materia!

Na3CrF6 from sodium fluoroborate by cold zone specimen surveillance station for the CSTF is complete, deposition as outlined in the "Conceptual System and fabrication of components for the two side-stream Design Description." The trap was designed to operate loops has started. from 750 to 1150°F at a salt flow rate of 0.2 gpm for a The MSRE coolant system piping, pump bowl, and salt system cycle time of approximate? 8 hr. The cold level indicator, which were removed for reuse in the trap was also designed to investigate the recombination CSTF, were cleaned with oxalic acid to remove the of 2F3 vapor (12 to 25% BF3 in the off-gas stream residual LiF-BeF2 salt. However, removal of the resid­ from the pump bowl) with the relatively cool salt melt ual tritium contamination from the inside surfaces of (MISO^F) in the cold trap. This system is expected to the pump bcwl was not complete. The peatest contam­ reduce the BF3 content in the off-gas stream to <0.5% ination was associated with oily and carbon-like coat­ BF3. Provisions have been made in the cold trap to ings on surfaces,13 and a standard smear test of a condense and collect the acid liquid12 from the off-gas coated area in the pump bowl cylinder opposite the stream. shield plug showed ~800,000 dis/min of transferable The second side-stream loop was designed for on-line tritium. After cleaning this surface with abrasive cloth monitoring of the salt by electrochemical means (devel­ and dilute nitric acid, transferable tritium was reduced oped by the Analytical Chemistry Division). The loop to 12,000 dis/min. Vziag this procedure, the piping and consist* of a 3-gal-capacity vessel with associated piping pump bowl nozzles within approximately 6 in. of which will operate at a flow rate of ~2 gpm while proposed welds were cleaned to tritium levels below maintaining a constant salt volume of 1.2 gal in the 2000 dis/min (MFC for uncontrolled rea) and are vessel. The salt-monitoring vessel was designed to ready for assembly.

12. MSR Program Semannu Prop. Rep. Aug. 31, 1970. 13, MSR Program Semiannu. Progr. Rep. Feb. 28, 1971, ORNL-4622, pp. 41-44. ORNL-4676, p. 58. 35

3.7 MSBR PUMPS Spare parts for the two pump assemblies havr be in inventoried, and spare hollow metal O-rings made from A. G. Gnndell Hastelloy N tubing have been ordered. The V-ui.-OD W. R. Huntley L. V. Wilson 4 by 0.035-in.-wall tubing for th<» O-rings will be formed H. C. Savage H. C. Young by drawing %-in.-OD by 0.072-in.-wall Hastelloy N tubing that is on hand. 3.7.1 Salt Pumps for MSRP Technology Facilities 3.7.2 ALPHA Pump The coolant pump tank and volute that were: removed 14 "ecently from the MSRE and the spare rotary element Initial operation of the ALPHA pump with high- from storage will be used in the coolant-salt technology temperature salt in the MSR-FCL-2 test facility demon­ : facility. When used with a 10.33-in.-diam impeller, this strated the need for several modification: : —rove combination will provide the required 90-ft head and reliability; the design of these modifications ^ in 800-gpm flow at 17** rpm by operating slightly toward progiess. In the meantime, the pump is being operated the shutoff side of its approximate MSRE operating in the MSR-FCL-2 at the specified design conditions. point of 85-ft head and 900-gpm flow rate. This Prior to installation in the salt facility, die pump was operation is not expected to impose excessive radial subjected tc a cold shakedown test to ensure that hydraulic forces on the pump shaft. The available 75-hp bearings and rotating and static seals function properly. motor will be loaded to approximately 45 hp for this The results of several tests indicate steady-state oil service. leakage rates past the rotating shaft seals ranging from The rotary element will be reconditioned with new 0.3 to 3.5 cc/day for a pump speed of approximately bearings, and the shaft seals will be relapped. It will 4000 Trni and a seal differential pressure of 7 psi. then be operated in a cold 'hakedown stand to check Considerable difficulty was experienced with the shaft seal leakage rates prior to installation in the hollow metal O-ring gaskets which seal the removable coolant-salt technology facility. pump rotary element to the pump bowl. In the present The head and flow requirements for the gas system design the space between two concentric gaskets is test facility will be provided by installing an available buffered with helium. The gaskets are of hollow ll%-in.-diam impeller of MSRE coolant-salt pump steinless steel t joe construction, have a toroidal diam­ design in the MSRE Mark 2 fuel-salt pump. This eter of % in., an overall Jiameter of 6 in., and are impeller will provide 1000 gpm and approximately plated with silver or gold. In an initial test with 100-ft heal with 100-bhp input at near 1800-rpm pump silver-plated gaskets, after carefully hand polishing the speed. Since tne inlet and discharge openings in the sealing surfaces in the matching flanges, a total leak rate coolant-salt pump impeller are smaller than those in the of approximately 6 cc/hr past both rings was attained fuel-salt 'ump impeller, a stationary filler piece will be with the buffer zone pressurized to 6.5 psig. The plating installed in the volute inlet. A spa.e MSRE coolani flaked from gold-plated gaskets during installation, and pump drive motor, nominally rated for 75 hp at 12C0 so gold plating is not receiving current attention. The rpm. but wound for 1800-rpm operation, will be used. total leak rate was reduced in a later installation by This oversize motor can sustain continuous operation to carefully hand polishing the silver-plated gaskets: the 113 hp at 1800 rpm. The oversize frame was selected total leak rate of approximately 1 cc/hr was attained early during MSRE design to standardize the motor-to- with the buffer zone pressurized to 8 psig. This leak beiring housing mounting dimensions 'or both the rate was considered satisfactory because it is unlikely 1200-rpm fuel pump and 1800-rpm coolant pump. that either air or moisture can enter the pump in a significant quantity past the buffer gas barriei. How­ The rotiry element from the Mark 2 pump will be ever, because of the difficulty in attaining and maintain­ reconditioned. New bearings will be installed, the shaft ing the po,'»shed surfaces needed to achieve a satisfac­ seals will be relapped, and the rotary assembly will be tory seal with the hollow metal O-rings, we plan to balanced dynamically. The element then will be oper­ replace them with a buffered ring joint seal utilizing a ated in the cold shakedown stand to check shaft seal solid metal gasket. leakage rates prior to installation in the gas system technology facility. During the assembly, measurements will be made of radial load vs shaft deflection and shaft critical frequency of the Mark 2 pump shaft with the 14. MSR Prnpam Semkmnu. Prop. Rep. Feb. 28, 19?1, 11 %-in.-diam impeller. ORNL-4676, p. 59. 36

The ALPHA pump developed a gas leak across the The jet pump system is shown schematically in Fig. lower shaft seal after 56 hr of intermittent operation 3.7. During normal operation, jet pump A, having a and a total of 520 hr at elevated temperature in the pumping capability of a little greater than 36 gpm, will MSR-FCL-2. Disassembly and inspection of the pump take salt and gas from the bottom of the drain tank and revealed than an O-ring made of Buna-N had failed. The discharge it along with its driving salt, QnA, into the O-ring is part of the shaft seal which was puro!i.->wd inner vessel. It will probably be necessary to install a gas from the Sealol Corporation. The lower shaft seal separator in the discharge line jf jet pump A. operates with oil lubricant contaciirg its top side and Jet pump B is the primary salt return pump and is gas contacting its lower side. The gas is principally designed 10 have a suction How the! is strongly helium containing approximately 0.1% BF3 whose dependent vper »he salt level in the inner vessel. The source is the sodium fluoroborate in tk» pump tank. characteristics of jet pump B are shown in Fig. 3.£,

The dilute BF3 attacked the Buna-N material and where Qsg is the flow return from the drain tank and produced ths gas leak. The split purge flow of helium in includes the driving flow.. £.7,4, for jet pump >4. During the shaft annulus was not operated in this application normal operation the salt level, //<>, in the inner vessel because it had not been found necessary to the will be between 6 and 10 ft above the center !ine of jet successful operation of a similar seal on the LFB pump pump B. If the salt level in the inner vessel should drop in the MSR-FCL-1. Impuritv control and facility to about 5 ft below t!ie jet pump centei line, the operation are also simplified when the split purge is not suction flow will go to zero and the pump will be used. operating very near cavitation. The purpose of having The mechanical design of the jower shaft seal is being this pump characteristic is to prevent the unwanted and changed to (1) repb.ee the present elastomeric static uncontrolled reintroduction of gas from the drain tank seal with a metallic bellows and (2) to eliminate the into the fuel-salt system should the salt flow from the press fit of the seal cartridge in the inner bearing separator be drastically reduced. The jet pumps have housing. The press fit has caused galling of the static sjme overcapacity should the flow from the gas sealing surface in the inner bearing housing. In addition, the cross section of the pump shaft will be strengthened in the vicinity of the lower shaft sea! and bearing. These ORNL-OWG 71- 3140 improvements in the pump will be accomplished during GAS SEPARATOR a future scheduled shutdown. /fuElS A//»*150ft / In order to proceed with the test program for the TO HEAT MSR-FCL-2, temporary repairs were made to the pump. FROM EXCHANGER An O-ring made of Viton, which is more resistant to REACTOR

BF3 than Buna-N, was installed in the present lower shaft seai. The inner bearing housing was machined and plated with copper to provide a good sealing surface for the seal cartridge. After a cold shakedown test the DRAIN pump was reinstalled in the MSR-FCL-2 facility and is TANK- 65 « presently supplying 850°F salt at the design flow rate 70 ft ^ ftsJ of 4 gpm at 4800-rpm shaft speed. l ! r

3.73 Drain Tank Jet Pump System for MSDR 20 ft T A study was made of a jet pump system to return fuel salt from the drain tank to the fuel-salt system of the 75 gpm; Molten-Salt Demonstration Reactor (MSDR). The salt LL J. going to the drain tank is part of the effluent from the ±& '9 gpm gas sepaiator used to remove the gaseous fission products from the fuel salt. It is estimated that the flow Fig. 3.7. Jet pump system for returning salt from drain tank to foci-salt system in a motten-sait demonstration reactor of fuel salt into the drain tank will be between 27 and (MSDR). Schematic of the jet pump drain tank fuel-salt system 36 gpm when all three fuel-salt pumps and their gas showing installation of jet pumps A and Sand giving elevations injector-separator systems are operating normally. and driving flows. 37 separators go above the design flow. Tlie jet pump operational characteristics of jet pump B. The (unused) characteristics are based on dimensionless exper lenval jet pump would have a nominal design area ratio data from pumps tested by NASA.15 (driving nozzle area/mixing throat area) of 0.197. Four The study was continued to obtain an indication of conditions were investigated: the effects of plating or erosion and corrosion on the a. an area ratio of 0.207 caused by an increase in the nozzle diameter by erosion and corrosion, ORNL-DWG 7I-13HI b. an £rea ratio of 0.207 caused by a decrease in the 80 • mixing throat diameter by plating, c. an area ratio of 0 187 caused by a decrease in the

70 CONDITION o nozzle diameter by plating, CONDITION V d. an area ratio of 0.187 caused by an increase in the mixing throat diameter by erosion-corrosion. // J DESIGN 60 The driving nozzle diameter for the 0.197 area ratio was about 0.500 in., and the corresponding mixing CONDITION "d" throat diameter was 1.126 in. The four conditions listed CONDITION V 50 - (A above represent corresponding diametral changes as follows: e a. o> OPERATING 40 a nozzle diameter increase of 0.012 in., CD RANGE ) b. mixing throat diameter decrease of 0.027 in., c. nozzle diameter decrease of 0.013 in., 30 d. mixing throat diameter increase of 0.030 in. The results are shown in Fig. 3.8 from which it can be 20 seen that (1) an increase in the nozzle diameter ira eases jet pump delivery just as does a decrease in the mixing throat diameter, and (2) a decrease in the nozzle 10 diameter decreases jet pump delivery as does an increase in the mixing throat diameter. It can also be seen in Fig. 3.8 that conditions a and b would result in an uncontrolled delivery of radioactive gas to the fuel-salt -5 0 5 10 15 system if the inflow of salt to the drain tank from the */ , HEAD ABOVE JET PUMP "B" (ft) 0 gas separator were reduced to about 6 gpro, which

corresponds to a Q4B of approximately IS gptn. Fig. 3.8. Jet pump for returning salt from drain tank to Conditions c and d limit the rmmpi lg capability of the fuel-salt system in a molten-salt demonstration reactor (MSDR). two jet pumps to about 40 to 45 gpm. Graph of delivery capacity of jet pump £ at its initial design area ratio of 0.197 and at four different off-design conditions. There are alternative configurations and character­ istics for jet pumps that may furnish adequate opera­ tional margins when the long-term erosion, corrosion, 15. N. L. Sanger, Cavitating Performance of Two Low-Areaand plating characteristics of container material in fuel Ratio Water Jet Pumps Having Throat Lengths vf 7.25salt are understood well enough to warrant additional Diameters. NASA-TN-D-4592 (May 1968): study. 4. Instrumentation and Controls

S. J. Ditto

4.1 TRANSIENT AND CONTROL STUDIES OF THE part,2 Chaps. 1 and 2 provide broad and quite general MSBR SYSTEM USING A HYBRID COMPUTER descriptions which are intended to convey the criteria anc philosophy used as the basis for the design of the O. W. Burke MSRE instrumentation and controls systems. Chapter 2 The hybrid computer model of the MSBR system as also contains detailed descriptions of the nuclear described in the February, 1971, semiannual progress instrumentation, the health physics, process, and stack report1 is operational. In order to accommodate the radiation monitoring systems, the data logger computer, caiculational stability and time requirements of the jnd the beryllium monitoring system. Chapters 3 digital portion of the hybrid computer, the model through 7, which are contained in this volume, provide operates in a time domain that is 20 times real system detailed descriptions of the MSRE process instrumen­ 3 time. tation and of the electrical control and aiaim circuitry. The model has been checked out, and a number of The Graft of the report has been completed, reviewed, transients have been run in order to test its validity. At and submitted for minor editing and publication. this point the model includes no controllers. The next order of business is to incorporate system controllers 43 FURTHER DISCUSSION OF into the model and to check the performance of these INSTRUMENTATION AND CONTROLS controllers. DEVELOPMENT NEEDED FOR THE The model will be used in the development of an MOLTEN-SALT BREEDER REACTOR overall control scheme for the MSBR plant. Of partic­ R. L. Moore ular interest is the effect of variabfe flow rate in the secondary salt loop sixi the use of bypass valves in the Previously published information4 concerning the secondary loop. The model will also be used to aid in development and evaluation of process instrumentation the determination of the range of thermal transients? applicable to molten-salt breeder reactors was updated. which could be expected in the salt systems under Areas where instrumentation techniques and com­ anticipated transient conditions. This information is ponents tested during operation of the Molten-Salt needed as input fo: the design studies of the steam Reactor Experiment may be applicable to the MSBR generator. are described, and recommendations for further devel­ opment are stated. In this study to date, no problems 4.2 MSRE DESIGN AND OPERATIONS REPORT, are foreseen that are bev ond the present state of the 5 PART HB, NUCLEAR AND PRC CESS art. INSTRUMENTATION This report is now in publication. R. L. Moore P. G. Hcmdon

1 lis report is the second of two parts describing 2. J. R. TaOackson, MSRE Design and Operations Report, Part IJA, Nuclear and Process Instrumentation, ORNL-TM-729. MSRE nuclear and piocess instrumentation. In the first 3. Abstract of ORNL-TM-729, Part IIB. 4. J. R. Tallackson, R. L. Moore, and S. J. Ditto, Instrumen­ tation and Controls Development for Molten-Salt Breeder 1. MSR Program Senuannu. Progr. Rep. Feb. 28, 1971, Reactors, ORNL-TM-1856 (May 1967). ORNL4676,p.61. 5. Abstract of ORNL-TM-3303.

38

HM—win if lump* ^-»-***-w ••• ———*™i—| 5. Heat and Mass Transfer and Thermophysical Properties

H. W. Hoffman J. J. Keyes, Jr.

5.1 HEAT TRANSFER It was not practical to operate the gas-pressurized heat transfer system in such a manner that exactly the J.W.Cooke same mass flow rate and average fluid temperature were In studies of heat transfer to a proposed MSBR fuel maintained for consecutive runs with and without an unheated entrance length. This was particularly true at salt (LiF-BeF2-ThF4-UF4; 67.5-20-12-0.5 mole %)we observed that, for the Reynolds modulus range from the higher temperature where both the mass flow rate 2000 to 4000, the heat transfer coefficient varies along and frictional pressure losses were so small that moni­ the test section in a manner which appears to be related toring the flow rate to hold the Reynolds modulus to a delay in transition to turbulent flow. It has been constant was not possible. In addition, the fluid suggested that this delay in transition is abetted by the temperature (and thus the fluid viscosity) varied from stabilizing influence of heating for the case of a fluid inlet to outlet of the test section, particula. ty during having a large negative temperature coefficient.1 Addi­ the higher heat flux runs. tional experimental results using the proposed MSBR salt have been obtained which lend to confirm this theory. ownL-0W6 11-«3l » 80 0130 In Fig. 5.1, the viscosity fi and its first derivative dy/dt are plotted as a function of temperature for the 70 subject molten-salt mixture. Note that the temperature 60 coefficient \dn/dt\ decreases by a factor of 10 from 900 --020* to 1450°F. If, indeed, the flcv. is stabilized by a large 5 50 negative value of dn/dt, the stabilization should become 40 (A > O less pronounced as the fluid temperature increases; the length should be less. To verify this hypothesis, 20 additional heat transfer measurements were taken at an K> -dphl i ^^^»^^_ average fluid temperature of 1450°F and compared i MELTM IPOMT • .. with existing data at 1100°F. These data are tabulated i Ji J eoo 900 4000 two eoo am MOO aoo woo in Table 5.1. TEMPERATURE

Fig. S.I. The rucosity aad its ilfiivitiw ss • 1. MSR Program SemUmnu. Progr. Rep. Feb. 28, 1971,fanctjofi of tempentaie for die motua-Mlt UF-MV ORNL4676, pp. 64-67. TI1F4-UF4 (67.5-20-12-0.5 mole%).

39 40

Tabk 5.!. Data for heat transfer experiments using the salt mixture LiF-Bef jThF4-UF4 (673-20-12-03 mole %)

q/A T AT, Run out -2 Heat h b V N (Btuhr"' ft < I,e *Pr *Nu 1 2 _1 "ST No* (°F) 5 balance IBtuhT ft" (°F) ) (°Fi (°F> x 10" )

IS 1077.2 1099.9 105.8 0.99 1.01 3370 1^0 20.4 937 7.96 16 1082.7 1106.6 Ss .8 0.99 1.08 3264 14.7 25.1 1153 9.94 22 1089.3 tns.5 170.7 2.0 1.13 3591 13.8 25.1 1157 9.87 23 1114.2 1163.6 189.8 2.0 1.09 3749 12.7 23.4 1076 9.40 104 1399.5 1445.7 78.9 0.S2 1.02 3260 6.00 20.22 930 10.93 10S 1410.0 1459.0 99.3 0.82 1.04 3152 5.84 16.21 759 8.80 106 1390.6 1510.3 246.9 1.96 1.12 3409 5.56 17.28 795 9.17 107 1385.4 1506.3 272.8 2.02 1.10 3457 5 62 16.31 750 8.57

*Even runs with unhealed entrance length; odd runs without. ^-r^u^Pr173^)' 0.14

To compare the local heat transfer coefficients at the approach to constant hx for the case without an two temperatures with or without an entrance region, a entrance length. The influence of heat flux on the heat method was developed to normalize the data using transfer development cannot be conclusively deduced Hausen's equation to include the dependence of local from Fig. 5.1, however, because of the simultaneous heat transfer coefficient on Reynolds modulus and fluid variation of Reynolds modulus in this transitional range properties: for which relatively small changes in the Reynolds modulus are significant.

2/3 1/3 tfNu = 0.116(tfRe - 125)A'pr (^) ' . (5.1) V*5/ ORNL-OWG 71-43196 This equation correlates molten salt as well as oil and water heat transfer data in the transitional flow regime. The normalizing procedure followed three steps: (1) Each local heat transfer coefficient for the individual runs was adjusted to the same Reynolds and Prandtl moduli based on the average fluid tc.perature in the test section; (2) each local coefficient for a pair of consecutive runs (with and without an entrance region) was then adjusted to an average of the two Reynolds and Prandtl moduli for the pair of runs; and (3) finally, the coefficients for two pairs of runs at two tempera­ ture levels were adjusted to the average Reynolds modulus for the two pairs of runs. In most cases, these

adjustments amounted to only a few percent in the hx value. Variations in the ratio of the normalized local heat

transfer coefficient hx to the heat transfer coefficient at

the exit, hexit (entrance length case), with distance from the inlet to the heated test section are shown in Fig. 5.2. Included are results for two values of heat flux and Reynolds modulus. Fig. 5.2 Variation in the ratio of local to exit heat transfer A small but significant improvement can be seen in coefficienu with distance from the inlet to the heater section the heat transfer development with length at the higher with and without an entrance length. The exit coefficient with fluid temperature, as evidenced by the more rapid an entrance region was used to obtain this ratio. 41

Experiments aimed at a study of the effect of wetting ORNI.-OWG 7t-13197 on molten-salt heat transfer using the proposed MSBR , ! fuel salt have been delayed due to inability, at the •: i 1 MELTING POINT present, to understand the wetting behavior of this salt 1 in static capsule expciiments. The salt was observed to _•— be wetting on Hastelloy N initially, whereas our L+—- —•••— ——*— previous experience with the salt mixture LiF-BeF - 2 i

ZrF4-ThF4-UF4 (70-23-5-1-1 mole ft) suggested that i nonweti -ig should be observed initially, and that a reducing agent (e.g., Zr or Be) would be required to produce wetting.2 Since the MSBK salt exhibited wetting under all conditions, *e believe that it is necessary to explain the behavior and to investigate techniques for inducing nonwetting which can be applied in the heat transfer system. 400 500 600 700 8O0 900 TEM°ERArjRE fO 5.2 THERMOPHYSICAL PROPERTIES Fig. 5.3. The thermal conductivity of the mottev-salt mixture J.W.Cooke LiF-BeF2 (66-34 mole %) using an improved amble-gap conductivity apparatus. Meisurements of the thermal conductivity of the salt mixture LiF-BsF2 (66-34 mole %) have been made over the temperature range from 300 to 870°C (458°C mp) Mass transfer coefficients have been measured for using the improved version of the variable-gap tech­ helium bubbles of mean diameters from OX) 15 to 0.05 nique.3 The preliminary results (omitting two data sets in. extracting dissolved oxygen from five different in the solidus region which are being analyzed) are mixtures of glycerol and water (Schmidt modulus range shown in Fig. 53. These new results fall midway 4 s from 419 to 3446) over a pipe Reynolds modulus range between previous uncorrected and corrected results, ' 3 s from 3.1 X 10 to 1.6 X 10 for both horizontal and but the temperature dependency in the liquidus region vertical flow in a 2 in.-diam conduit. Extensions of this is less than our previous measurements had indicated. program are projected for different pipe diameters and The ratio of the liquid to solid conductivity is around different interfacial conditions. Additional experiments 0.75 compared with the average value of 0.86 ±0.13 are anticipated that will establish mass transfer rates published for a group oi salts.6 The estimated maxi­ applicable to such flow "discontinuities" as ebows, mum uncertainty in the present results is expected to tees, valves, Venturis, etc. be less than ±10%. One of the first conclusions of these experiments is that the only effect on mass transfer rates of bubble S3 MASS TRANSFER TO CIRCULATING BUBBLES volume fractions up to 1% is in the highly predictable T. S. Kress change in surface area. No significant influence of bubble volume fraction on the mass transfer coeffi­ The first phase of an experimental program designed cients (which are based on unit area) was detected. to measure mass transfer rates between small bubbles An examination of all the experimental data has circulating with a turbulent liquid has been completed. revealed that the mass transfer coefficients depend on the flow orientation (horizontal or vertical). At suffi­ ciently high flows, however, the horizontal and vertical 2. MSR Program Semiannu. Progr. Rep. Feb. 28, 1971, results are observed to be indistinguishable within limits ORNL-4676, pp. 67-68. of the experimental error. To establish a criterion for 3. MSR Program Semiannu. P~ r. Rep. Feb. 28, 1970, 3 the Reynolds modulus that marks this equivalence of ORNL-4548, p. 89. horizontal and vertical flow, use was made of an 4. MSR Program Semiannu. Progr. Rep. Feb. 28, 1969, 7 ORNL-4396,p. 125. expression developed previously for the relative im- 5. MSR Program Semiannu. Progr. Rep. Aug. 31, 1969, ORNL-4449, p. 92. 6. A. G. Turnbill, Australian J. Appl. Sci. 12, 30-41 7. MSR Program Semiannu. Progr. Rep. Feb. 28, 1969, (January 1961). ORNL-439f, pp. 124-28. 42

portsnce of turbulent inertial forces compared with through a quiescent liquid. These asymptotic values, ka, gravitational forces, are well described by the correlation recommended by Resnick and Gal-Or,* 2/3 / l 2 ,/3 r F d * ka=0AS4(Qpg/n)l y,/dj2. (5.3) " '\ Vo* / "vs *

In addition, the variable ratio Fj/Fg proved to be a good linear scaling factor for calculating the vertical A conservative vahie, Flf'Fg = 1.5, has been estab­ lished above which it is valid to assume that horizontal flow coefficients in the transition region. A recom­ and vertical flow mass transfer coefficients are the mended correlation for the vertical flow coefficients in same. Equation (S.2) is a correlation of the horizontal the transition region is flow data and the vertical flow data for whkA FJF. > 1.5: 1 (lQfyFg)/1.5 *v~*« + *, l+(10rVF,yi.5 l+(lQ/y/y/1.5 Sh/Scl/2 =034Re° 94 (dJD)10 , (5.2)

1/2 where kh and ka are to be determined from Eqs. (5.2) which has z standard deviation in In (Sh/Sc ) of 0.19 and (53), respectively. The curves calculated from this and an index of determination of 0£6. Figure 5.4 1 equation are shown ir» Fig. 53, together with horizontal shows a comparison of the horizonta flow data with and vertical flow data for a 25% glycerin mixture. The Eq.(5.2). horizontal flow regression equation plotted in Fig. 55 As flow was decreased to a value for which the ratio includes data for glycerin compositions of 123,25, and of liquid axial velocity to bubble terminal velocity (in 37 5%. the gravity field) was about 3, severe stratification of the bubbles made operation in horizontal flow imprac­ tical. The vertical flow coefficients underwent a transi­ 8. W. Resnick and B. Gal-Or, "Gas-Liquid Dispersion," pp. tion from the behavior represented by Eq. (5.2) to 295-393 in Advances in Chemical Engineering, Vol. 7, approach asymptotes characteristic of bubbles rising Academic, New York, 1968.

ORNL-OWG 71-7994- A K)5 11 i < r!CP!20MTAL FLOW . j i I REGfTE^ON JNE FORCED TO F'T Sc*2 I - d„ BUBBLE 5 MEAN SCHMIDT NO..SC ~ DIAMETER (in.) 370 750 20t3 419 _ 0.015 • * • • / 0.02 * * * • M 1 2 0.025 • • • • u' m 0.03 o o o » 0.035 * * < >

4 % GLYCERINE <2.5 25 37.5 0 f -rt M * o pif i ^ o> r 1 *"""' 5 •I

mf a? * , p IJPH* 4> i 1 -.1- ! /^-a »- 0.335 to094 Sc'/2 (fy 2 i (/ ) i i

i i.—„—_„*,—i J L-L 1 .. >f C4 2 5 10s 2 Kfi W£ REYNOLDS Hb.,f**VD/r

Fia. $A. Typical experiment* aw tnMfer coeffeferts lot horizontal and vertical flowi n a 2-in.-diam conduit. 43

ORML -DW6 71-7991* 10 J 1

^,^-CALCULATEO ASYMPTOTES . *W 5, •j U.UH ~ 0.03 rt/h r ,0.02 ~™ v Ss,N^A ^2 t //L ' J 0.015 W *4 .2T 4 4 VERTICAL FLOK ir 1 rMj Mr (USING /j/j AS SCAL E FAC T OR)N^ LOCUS OF • i ^/r-1.5 — « COEFFICIEN T bJ en ^1 z ' o/ Q: »- 0.5 /7~ CO 25% GLYCERICI E CO VROM HORIZONTAL'FLOW < SCHI«K) T NO. « 750 REGRESSION EOUATION ^ 2 i I I •J ~~ BUBCIL E » I *" \ 0 / MEAM 0.2 OIAME TER HORIZONTAL VERTICAL (in. ) FL OWr FLOW Q.0> 4» o 0.0 I 1i o 0.0 i k A 0.0 3 r 4 1 11 103 5 K)4 2 5 10* PIPE REYNOLDS NO., R«sM?/r

Fig. 5.5. Coriparixm of expeiioKntal horizontal flow maa 44

The preceding correlations apparently apply only for Nomenclature mobile interfacial conditions as evidenced by the high & = molecular diffusion coefficient exponent for the Schmidt modulus. For rigid interfaces, this exponent is expected to be % and the coefficient D = conduit diameter multiplying the equation should be different. In the dys = bubble Sauter-mean diameter absence of experimental results, a tentative correlation F = gravitational force on a bubble (buoyancy) for rigid interfacial conditions might be inferred from g Eq. (5.2) to be: Fj = mean inertial force on a bubble due to turbulent fluctuations

94 1/3 10 Sh = 0^5Re°- Sc (dVJ/D) , (5.4) g = gravitational acceleration

ka - low flow asymptotic value of kv in which the coefficient 025 was obtained from the coefficient of Eq. (5.2), 034, by multiplying it by the kf, - horizontal flow axially averaged mass transfer ratio of rigid to mobile coefficients of equations9 coefficients applicable to bubbles moving steadily through a liquid. £y = vertical flow axially averaged mass transfer coeffi­ Equation (5.4) should be used with caution because it cients has not been justified experimentally or theoretically. A Re = pipe Reynolds modulus (VDpln, in which Vis the similar transformation of Eq. (53) would be required liquid axial mean velocity) to obtain the rigid-interface values of the vertical flow asymptotes. JC = Schmidt modulus (ji/p& ) Sh = Sherwood modulus (kD/&) H = liquid viscosity 9. A. C. Lochiel and P. H. Catdobank, "Mass Transfer in the p = liquid density Continuous Phase around Axttymraetric Bodies of Revolution,*' Chem. Eng. Set 19,471-87 (1964). v = liquid kinematic viscosity (p/p) Part 2. Chemistry

R.B.Briggs

The chemical development activities described below coming few weeks. Small efforts continue on improve­ are, in the main, conducted to provide chemical ments to die reductive extraction process for rare earths information required in the development of molten-salt and, more significantly, upon methods for removal of reactor systems. rare-earth species from lithium chloride. An appreciable-, though diminishing, fraction of the Study of possible mechanisms of the mtergranidar effort is still devoted to postoperational examination of attack upon die metallic components in MSRE now specimens and materials from MSRE. Such examina­ constitutes an appreciable fraction of the chemical tions, several of which are detailed in this document, research program. These studies, all initiated in recent should br largely concluded during the next reporting months, have not yet produced information to report. period. The principal emphasis of analytical chemical devel­ The behavior of hydrogen and tritium in molten salt, opment programs has been placed on methods for use metals, and graphite constitutes a substantial fraction of in seirdautomated operational control of molten-salt the research and development effect. Solubility of breeder reactors, for example, the development of hydrogen and its isotopes in molten fluorides is under in-line analytical methods for the analysis of MSR fuels, study, as are rates of diffusion of hydrogen through for reprocessing streams, and for gas streams. These pertinent metals and possible chemical exchange methods include electrochemical and spectrophoto- schemes capable of holding up the tritium to allow time rnetric means for determination of the concentration of for its controlled recovery. U3* and other ionic species in fuels and coolants, and Studies of chemical separation of protactinium during adaptation of small on-line computers to electro- this period have been confined to those based upon analytical methods. Parallel efforts have been devoted selective precipitation of oxides. It now appears that to the development of analytical methods related to such a separation process is chemically feasible; we assay and control of the concentration of water, oxides, anticipate that, insofar as small-scale studies are con­ and tritium in fluoroborate coolants. cerned, these researches will be concluded during the

45 6. Postoperational Examination of MSRE

6.1 EXAMINATION OF MODERATOR GRAPHITE Examination revealed a few solidified droplets of FROM MSRE flush salt adhering to the graphite, and one small (05 2 S-S-Kirsfa F.F.BIankenship cm ) area wh*re a grayish-white material appeared to have wetted the smooth graphite surface. One small A complete stringer of graphite (located in an axial crack was observed near the middle of a fuel channel. position between the surveillance specimen assembly At the top surface of the stringer a heavy dark deposit and the control rod thimble) was removed intact from was visible. This deposit seemed to consist in part of the MSRE. This 64.5-in.4ong specimen was transferred salt and in part of a carbonaceous material; it was to the hot ceOs in building 3525 for examination, sampled for both chemical and radiochemical analysis. segmenting, and sampling. Most of the examinations Near the metal knob at the top of the stringer a crack in and analyses were similar to those given to the graphite the graphite had permitted a chip (about 1 mm thick surveillance specimens previously removed from MSRE and 2 cm3 in area) to be cleaved from the flat top during its scheduled shutdowns. In addition to these surface. This crack may have resulted from mechanical "standard" methods, surface samples from the stringer stresses due to threading the metal knob into the were examined by Auger spectroscopy and by a special stringer (or from thermal stresses in this metal-graphite x-ray diffraction technique, cross sections of the system during operation), rather than from radiation or stringer were gamma scanned with a special pin-hole chemical effects. cowmating device, and samples milled from the stringer were carefully analyzed for tritium. 6.1.2 Segmenting of Graphite Stringer

6.1.1 Results of Visual Examination Upon completion of the visual observation and photography and after removal of small samples from Careful examination of all surfaces of the stringer several locations on the surface, the stringer was with a KolLnorgen periscope showed the graphite to be sectioned with a thin carborundum cutting wheel generally in very good condition, as were the many (Canosaw) to provide five sections of 4 in. length, three surveillance specimens previously examined. The cor­ thin (10 to 20 mil) sections for x radiography, and ners were clean and sharp, the faint circles left upon three thicker (30 to 60 mil) sections for pin-hole milling the fuel channel surfaces were visible and scanning with the gamma spectrometer. Each set of appeared unchanged, and the surfaces, with minor samples contained specimens from near the top, middle, exceptions described below, were clean. The stringer and bottom of the stringer. The large specimens, from bottom, with identifying letters and numbers scratched which surface samples were subsequently milled, in­ on it, appeared identical to the photograph taken cluded (in addition) two samples from intermediate before its installation «n MSRE. positions.

46 47

6.13 Examination of Surface Samples expected chemical behavior and are significant in that by X-Ray Diffraction they represent the first experimental identification of the chemical form of fission products known to be 1 tsvious attempts to determine the chemical form of deposited on the graphite surface. fission products deposited on graphite surveillance Several hot cell techniques were tried for mounting specimens by x-ray reflection from flat surfaces failed the x-ray diiTraction samples in glass capillaries or on to detect any element except graphitic carbon. A quartz fibers, but they proved unsuccessful. To avoid sampling method which concentrated surface impurities undue radiation exposure to analytical chemistry per- was tried at the suggestion of Harris Dunn of the sonnel, the remaining samples were not analyzed. Analytical Chemistry Division. This method involved lightly brushing the surface of the graphite stringer with 6.1.4 with a a fine Swiss pattern file which hsd a curved surface. The grooves in the file picked up a small amount of surface Is osder to provide an inexpensive guide for later material which was transferred into a jdass bottle by radiochemical work with milled stringer samples, a Upping the file on the lip of the bottle. In this way simple technique was developed (with the help of E. I. samples v;;re taken at the top, middle, and bottom of Wyatt and H. A. Parker of the Analytical Chemistry the graphite stringer from the fuel channel surface, Division) for taking gamma scans of a number of from the surface in contact with graphite, and from the locations on the cross-section samples of the grapMte curved surface adjacent to the conti ' od thimble. stringer The sample, approximately 2 X 2X0X»S0m-,

Samples were also taken of the "dirty" graL ile and silt was piaced over a V14-in.-dnm hole through the center on the top end surface of the stringer. of a targe faceofa4X4X8in.lead brick. The hole Although each sample contained only about a dozen was positioned over the center of the Nad crystal of a tiny particles and weighed less than 0.1 mg, the various gamma spectrometer. The sample was shielded above by samples read 1 to 4 R/hr at a distance of 6 in. with a a %-in.-duck sheet of plate glass with a scratched cross soft-sheP*d "Cutie Pie" outside the glass bottle wall. on the bottom surface positioned above the hole in the This radiation field made transfer of the particles into lead brick. By means of a 12%. phytic ruler taped to glass capillaries for powder x-ray diffraction examina­ the specimen, any desired region of the graphite cross tion a difficult operation. However, three (0.2 m) section could be positioned over the hole m the lead capillaries were packed and mounted in holders which brick for gamma scanning. With this lelatively rapid fitted into the x-ray camera. technique, 18 to 20 posit ons were gamma scanned on Short-exposure x-ray photographs were taken with each of the cross-section samples from the top, middle, precautions to minimize blackening of the film by the and bottom of the graphite stringer. radioactivity. In spite of the precautions, samples from The distribution of the fou* main activities obseived the fuel channel surfaces yielded very dark films which (,0*Ru, ,25Sb, l34Cs,and ,,7Cs)inthe tk-eesamples were difficult to read. Many weak lines were observed b shown graphically in Fig. 6.1. The numben on each in the ~-ray patterns. Since other analyses had shown map are counts per minute above background and are Mo; Te, Ru, Tc, Ni, Fe, and Cr to be present in proportional to the radioactivity at each position for a significant concentrations on the graphite surface, these given isotope. (For comparison between isotopes, elements and their carbides and tellurides were searched counts per minute are not proportional to disintegra­ for by careful comparison with the observed patterns. tions per minute because of different counting effi­ In all three of the graphite surface samples so far ciencies.) In broad outline, the results were as expected. analyzed, most of the lines for Mo^C and Ru metai Heavy surface depositions of l0*Ru and I2$Sb were were certainly present. Foi one sample, most of the observed with little penetration to the interior. The Cs

lines for Cr7C3 were seen. (The expected chromium isotopes were found at deeper locations since they ,33

carbide in equilibrium with excess graphite is Ci3c2, possessed gaseous precursors (5 27-day Xe and but nearly half the diffraction lines for this compound 4.2-min,37Xe). were missing, including the two strongest lines.) Five of The volume of graphite scanned by this technique was

the six strongest tines for NiTe2 were observed. Mo quite small (V,« in. diam X 0.050 in.); this permitted a metal, Te metal, Tc metal, Cr metal, CrTe, and MoTe? more fine-grained look at fission product distribution were excluded by comparison of their known pattern than was possible by the milling techniques previously with the observed spectrum. These observations (except used for sampling graphite suryeQIance specimens.

for that of Cr7C3) are in gratifying accord with Correspondingly, the surface concentrations of all 48

Tl-IHM

Ffe.6.1. Gamma tcanc of MSRE graphite stringer crow tactions. 49

isotopes varied considerably between the two fuel 10, 20, and 30 mils deep were taken. Finally, a single channel surfaces examined. Usually, but not always, cut 62 mils deep was taken on the opposite flat fuel there was less of each isotope deposited near the channel surface. Only the latter cut was taken on the surfaces in contact with adjacent graphite stringers or two stringer sample* from positions halfway between with the control rod thimble. Individual (reproduci>le) the bottom and middle and halfway between the 134Cs points were often considerably higher or lower middle and top of the stringer. than adjacent points on a line between one fuel channel Four blank samples were milled by identical proce­ surface and the other. The variations at the graphite dures in the hot ceDs from an unirradiated spare stringer surface are believed to indicate spotty rather than of CGB graphite to indicate the amount of contamina­ uniform deposition of fission products on the specimen tion received by the samples m the process of being surface. The interior variations are believed to indicate milled in the highly contaminated hot cell. variations in porosity of the interior graphite. These The sample bottles were reweighed and delivered for observations and hypotheses are in accord with auto- radiochemical analysis. radiographs of graphite surveillance specimens pre­ viously examined which indicated spotty distribution of 6.1.6 RadfedKak^aadCkcsnical Analyses total activity. of MSRE Graphite

6.15 Mfflmg of Surface Graphite Samples Tne milled graphite samples were dissolved in a

boiling mixture of concentrated H2S04 and HNO-* As was done for the five pivvious sets of graphite with provision for trapping any volatilized activities. surveillance specimens removed from the MSRE, sur­ The following analyses were run on the dissolved face samples for chemical and radiochemical analyses samples:

were milled from the five 4-in.-long segments from the l0 12s top, middle, bottom, and two intermediate locations on 1. Gamma spectrometer scans for *Ru, Sb, ,34Cs, ,37Cs, ,,0Ag, 144Ce, *5Zr, »$Nb, and the graphite stringer. The milling techniques developed 60 for previous surveillance specimens could not be used Co. because of the peculiar geometry of the graphite 2. Separate radiochemical separations and analyses for stringer. A new technique was developed using the large 89Sr, ,0Sr, ,27Te, and 3H. A frw smtptes were milling machine in building 3525 hot cells and a analyzed for "Tc. rotating milling cutter 0.619 in. in utameter. The 3. Uranium analyses by both the fhiorometric and the specimen was clamped flat on the bed of the machine, delayed neutron counting methods. and cuts were made from the flat fuel channel surface and from one of the narrower flat edge surfaces on both 4. Spectrographic analyses for Li, Be, Zr, Fe, Ni, Mo, sides of the fuel channel. The latter surfaces contacted and Cr. (High-yield fission products were slso looked t-i? "'milar surfaces of an adjacent stringer in the MSRE forbutnotfouno.) core. Atic. the sample was clamped in position, the Uranium and spectrographk analyses. In Table 6.1 are milling mr chine was operated remotely to take succes­ given the uranium analyses (calculated as 233U) by sive cuts 1, 2, 3, 10, 20, 30, 245, 245, end 245 mils both the fluorometric method and the delayed neutron deep to the center of the graphite stringer. The counting method. The type of surfaces sampled, the powdered graphite was collected during and after each number of the cut, and the depth of the cut for each cut in a tared filter bottle attached to a vacuum cleaner sample are also shown in the table. Samples between 19 hose. The filter bottle was a plastic cylindrical bottle and 29 were inadvertently tapered from one end of the with a circular filter paper convering a number of specimen block to the other so that brger-than-planned drilled holes in the bottom. This technique collected ranges of cut depth were obtained. Samples from 3 to most of the thinner samples, but only about one-half of 18 were taken from the topmost graphite stringer the larger 245-mil samples. After each sampling the specimen, those from 19 to 31 and sample 36 were uncollected powder was carefully removed with the from the middle specimen, and those from 32 to 48 empty vacuum cleaner hose. were taken from the bottom specimen. Before samples were cut from the narrow flats, the In view of the fact that the uranium concentrations comers of the stringer bars were milled off to a width were at the extreme low end of the applicable range for and denth of 66 mils to avoid contamination from the the fluorometric method, the agreement with the adjacen stringer surfaces. Then successive cuts 1,2,3, delayed neutron counting method was quite satis- so

"Ml, ppm. Cut and Depth, Total U. ppm. Met** delayed Upp* Be, ppm Zr.ppm type* nab flnoroanttric PPOB — neutioa

1 lBbak 0-6 <10 <2 _ ._ 2 2 Bin* 6-30 1 0.1±0 05 <2 <1 — .- 3 1FC 0-2 28 353 ±13 360 320 1600 — 4 2FC 1-3 21 26.9 ±1.2 340 170 — — S 3PC 3-6 8 11-5 i 0.8 — — — — 7 5FC 16-36 2 2^ ±1.2 — — — — 11 9FC 556-801 3 2J6±K3 310 200 — 820 Fe 12 IE 0-2 <1(7) 22.7 ±23 2S0 180 — MghFe 13 2E 2-3 <30 8-6123 no 50 — — 14 3E 3-6 9 53 ±0.7 ^ 17 6E 36-66 •> 5jf»iOJ It IDeep 0-6? 7 2.4 ± 0.1 40 20 — — 19 IPC 0-5 2i 213 ± 0.6 220 150 970Mo,1100Ni 20 2PC 1-7 9 10.1 *- 0 8 190 100 — — 21 3FC 3-10 4 7.1 ± OA 23 5FC 16-40 <1 1J3 ± JI-7 26 8FC 311-556 <2 0-8 ±0.6 10 610 27 IE 0-3 3 3» i 0-2 150 90 1400 HijhFe 2S 2E 1-5 <8 5.9 ± 0.1 130 no 29 3E 3-8 3 5.7 ± 0.4 31 IDeep 0-62 4 33 ± 0-1 80 50 70 150 Ni 32 IDeep 0-62 14 13.0 ± 0-2 120 90 80 180 Ni 33 1FC 0-0.2 12 18.1 ± 13 1400 290 High H*hFe + Mo 34 2FC 0-3 36 29.2 ±13 410 240 500 2900 Ni 35 3FC 3-* 18 20/1 ±0.9 36 5E 16-36 1 23 ±0.1 - ** 39 6FC 36-66 J 33 ± 0-1 43 IE 0-1 51 118 ±6 1000 400 8000 H«hFe 44 2E 1-3 46 36.6 ±1.6 40 270 550 220 Ni 45 3E 3-6 8 7.8 ± 0.7 48 6E 36—66 2 3.6 ±0.2 49 1 Blank 0-2 <10 <2 — — 50 2 Blank 2-30 <1 0.1 ± 0.04 <7 <03 <40 <70Ni

'Dashes in the body of the table represent analyse* showing none present Blanks indicate the analyse: were not done. nThe number is the number of cut toward the interior starting at the graphite surface. **FC stands for a fuel channel surface, "E" for a narrow edge surface, and "Deep" for a first cut about 62 mils Ctp from a fuel channel surface. tfMmgh" indicates an unbelievably high concentration (several percent).

factory. The data suggest that the sizable variations values indicate that uranium penetration into modera­ between different surfaces (eg., the three deep cut tor graphite should not be a serious problem in samples 18, 31, and 32) were real. Sizable variations large-scale molten-salt reactors. also exist in uranium concentrations in the deep interior The fact that fluorometric values for total uranium of different regions of the stringer. These values range and the delayed neutron counting values for 233U from 2.6 ppm at the top to 0.8 ppm at the middle to 3 agreed (with the 233U value usually larger than the ppm at the bottom. total U value) indicates that little uranium remained in The concentration profiles indicated by the data in the graphite from the operation of th* MSRE with Table 6.1 were generally similar to those previously 235U fuel. Apparently, the 238U and ,35U previously observed both on the surface and in the interior. in the graphite underwent rather complete isotopic Concentrations dropped a factor of 10 in the first 16 exchange with 2 3 3 U after the fuel was changed. mils. A rough calculation of the total a33U in the The spectrographic results also given in Table 6.1 MSRE core graphite indicates about 2 g on the surface were disappointing in several respects. The sensitivities and about 9 g in the interior of the graphite. These low for all species were lower than hoped. Thus only the 51

strongest spectra (Be and Li) could be measured with samples were also contaminated with *°Co, the concen­ any reliability, and result* for Zr, Fe, Ni, and Mo were trations in the outermost stringer samples were signifi­ highly susceptible to sample contamination. While the cantly higher. It probably was formed by an nj> U-*o-Li-»o-Be ratios were approximately the same as for reaction from stable *°Ni. Its presence confirms the fuel salt (1 to 14.5 to 8.7) for about half the samples spectrographic analyses indicating that nickel was pres­ analyzed, the Zr results were more erratic. It had been ent on the stringer surfaces. hoped that high yield stable or long-lived noble-metal Surprisingly high concentrations of tritium were fission products (Mo, Tc, Ru, and Te) might be found in the moderator graphite samples (Table 6.2). detected in these samples, but they were not. The The tritium concentration decreased rapidly from about finding of ISO to 2900 ppm Ni in a few of the surface 10'' dpm/g at the surface to about 109 dpm/g at a

samples is probably real. The main conclusions from the depth of V,6 in. and then decreased slowly to about spectrographic analyses are that adherent or permeated half this value at the center of the stringer. If afi of the fuel salt accounted for the U, Li, and Be in half the graphite in the MSRE contained this much tritium, then samples and that a thin layer of Ni vas probably about 15% of the tritium produced during the entire deposited en some of the graphite surface. power operation had been trapped in the graphite. Radiochemical analyses. Since the graphite stringer About half the total trapped tritium was in the outer

samples were taken more than a year after reactor 716-in. layer. shutdown, it was po^Jbk to analyze only for the Similarly high concentrations of tritium were found relatively long-lived fission products. However, the in specimens of Poco graphite (a graphite characterized absence of interfering short-iived activities made the by large u Jform pores) exposed to fissionirig salt in the nalyses for long-lived nuclides more sensitive and core during the final 1786 hr of operation. Surface precise. The radiochemical analyses are given in Table concentrations as high as 45 X 1010 dpm/g were 6.2, together with the type and location of surface found, but interior concentrations were below 10s sampled, the number of the nulling cut, and the depth dpm/g, much lower than for the moderator graphite. of the cut for each sample. This suggests that the graphite surface is saturated The species 12SSc, ,06Ru, ,,0Ag, 9sNb,and ,27Te relatively quickly but that diffusion to the interior is showed concentration profiles similar to those observed slow. for noble-metal fission products ("Mo,' "Te,' 32Te, If it is assumed that the surface area of the graphite 2 io3Ru JO«RU and »sNb) m previous graphite surveil­ (about 05 m /g) is not changed by irradiation (there lance specimens, that is, high surface concentrations was no dependence of tritium sorption on flux), there falling rapidly several orders of magnitude to low was one tritium per 100 surface carbon atoms. Since interior concentrations. The 9sZr profiles were of the MSRE cover gas probably contained about 100 similar shape, but the interior concentrations were two times as much hydrogen (from pump oil decomposi­ cr three orders of magnitude smaller than for its tion) as tritium, a remarkably complete coverage by daughter 9 s Nb. It is thought that9 s Zr is either injected chemisorbed hydrogen is indicated. into the graphite by a fission recoil mechanism or is carried with fuel salt into cracks in the graphite; the much larger concentrations of 95Nb (and the other 62 CESIUM ISOTOPE MIGRATION noble metals) are thought to result from the deposition IN MSRE GRAPHITE or plating of solid metallic or carbide particles on the E. L. Compere S. S. Kirslis graphite surface. The 90Sr (33-sec 90Kr precursor) profiles were much steeper than those previously Fission product concentration profiles have been observed in surveillance specimens for "Sr (3.2-min obtained on the granhite bar from the center of the *9Kr precursor), as expected. An attempt to analyze MSRE core which was removed early in 1971. The bar the stringer samples for *9Sr also was unsuccessful. It is had been in the core since the beginning of operation; it difficult to analyze for one of these pure beta emitters thus was possible to obtain profiles for 2.1-year l34Cs in the presence of large activities of the other. (a neutron capture product of the stable ' 33Cs daugh­ The hot cell facility in which the graphite samples ter of 5.27-day ,33Xe) as well as the 30-year ,37Cs v/er- milled was heavily contaminated with ' "Eu and daughter of 3.9-min ,37Xe. These profiles, extending 154Eu. Correspondingly, the blank samples (Nos. 1,2, to the center of the bar, are shown in Fig. 6.2. 49, and SO) did not contain significantly less of these Graphite surveillance specimens exposed for shorter activities than the stringer samples. Although the blank periods, and of thinner dimensions, have revealed Table 6.2. Radiochemical analyses of graphite string*; samples

Sample Cut and Depth, Disintegrations per minute per gram of graphite on 12-12*69

J ,s4 lO«Ru iaiTe no »9 , !»4Cf No. type* mils »«Sb »*Nb Ag T »"Cs »°Sr ««Ce "Zr »»E» Eu *°Co >H

1 Thin blank 0-6 <8ES <4E6 <7E9 <9ES <3E5 <8E8 5.79E5 6.22E6 <2E8 2.93E7 3.12E7 1.06E7 9.15E5 2 Thkk blank 6-30 <8E9 8.53ES <7E8 <9E4 <3E4 <7E4 1.56E6 <2E7 1.85E6 1.83E6 6.81E5 2.38E6 3 1FC.T 0-2 3.1E10 7.31E10 8.9SE10 <4E12 <1E9 -330 <3E8 1.0E9 8.7E9 8.49E9 <1.8E10 <4.8E8 <5E8 3.63E8 5.92E10 4 2FC.T 1-4 1.14E9 3.74E8 3.42E9 <2.7E11 2.84E8 -13 1.06E7 2.39E8 1.1E10 4.26E8 2.30E9 36 5E,M 16-36 1.07E7 7.34E7 4.79E7 9.85E10 <4E6 3.40E7 5.14E8 2.18E8 <6E8 3.71E6 3.53E6 2.99E9 31 1 Deep,M 0-62 3.91E9 1.86E10 9.08E9 4.90E11 <9E7 9.72E7 9.13E8 2.26E9 1.10E8 <2E9 <1E8 <6E7 1.24E8 5.50E9 32 1 Deep.B 0-62 1.4SE9 4.62E9 5.84E9 2.16E11 •S6.3E7 1.96E1 1.13E9 2.43E9 6.14E8 1.13K9 <3E7 •S1.6E7 4.30E7 8.45E9 33 1FC3 0-0.2 2.96E11 4.19EU 8.22E11 2.13E13 <2E9 1.37E9 4.69E9 1.07E10 5.09E10 <1E11 <3E9 <3E9 6.82E9 1.59E11 34 2FC.B 0-3 5.76E9 1.15E9 1.75E10 3.04E12 1.57E9 1.76E8 6.43F8 8.13E9 4.67E9 1.14K10 <2.7E7 1.63E8 4.3IE10 35 3FC.B 3-6 1.27E9 3.29E9 3.22E9 3.78E11 2.76E8 1.17E7 2.66E8 4.51E8 <2E9 <1.8E7 1.94E7 1.26E10 38 5FC3 16-36 3.27E8 8.38E8 7.27E8 <8.3E10 <5.7E6 2.20E7 1.17E9 <1E8 <6E8 6.26E6 1.96E7 3.46E9 40 7FC3 66-311 3.13E7 1.04E8 5.20E7 <1.0E10 <2E6 1.03E8 1.33E8 <3E7 <2£8 <1.6E6 .1.23E6 5.69r8 42 9FC3 556-801 <1E7 <3.9E7 6.19E6 <4E10 <2E6 3.13E8 2.93E8 1.69E7 6.91E7 <3.2E8 <1E6 4.21E6 7.23E8 43 1EJ 0-1 3.05E10 6.94E10 8.06E10 8.49E12 <7.8E8 8.57E8 2.83E9 1.11E10 2 42E10 4.58E10 <3.SE8 <2E8 1.27E9 9.18E10 44 2E.B 1-3 3.45E8 8.30E8 1.06E9 1.50E12 S.07E8 3.07E7 2.71E8 9.76E8 <4E9 <1.6E7 1.34E8 J.46E10 49 Thin blank 0-2 1.33E7 5.09E7 1.4E11 <9ES <1.0EC 1.54E6 1.77E7 3.25E7 2.10E9 1.94E7 2.3E7 8.S6E6 4.65E6 50 Thick blank 2-30 2.39E6 8.61E6 7.02E6 <3.1E9 <2E5 <1.3E5 2.90E5 1.80E6 <1E8 4.69E6 4.96E6 1.07E6 1.79E6 51 Top knob 2.24E10 1.94E10

aThe number is the number of cut toward the interior starting at the graphite surface. "FC" stands for a fuel channel surface, "E" for a narrow edge surface, and "Deep" for a first cut about 62 mils deep from a fuel channel surface. T, M, and B represent samples from the top, middle, and bottom specimens of the graphite stringer, respectively. 53

PBNL-OWG 71-13199 18 t resulted in & fairly even concentration of this isotope - 137 throughout the graphite and must have produced a flat \ -ACCUMULATED 3Xe l33 \M DISINTEGRATION (est) deposition profile for Cs. This isotope and its ,T • io a ------neutron product '34Cs could diffuse to the bar surface and could be taken up by the salt. The 134Cs profile shows that this occurred. The ! 34Cs concentration that | Tit i T .- —^ would accumulate in graphite if no diffusion occurred has been estimated from the power history of the • 10'5 =r*-H- • ! • -t == MSRE to be about 2 X 1014 atoms per gram of * \ ' , i I ! = * p ^ graphite (higher if pump bowl xenon stripping is 4 inefficient), assuming the local neutron flux was a o io' s — '34c$ - ' i ; = o --r> __„_; = minimum of four times the average core flux. The oft"! SAn ctNitK LINE^^- observed ' 34Cs concentration in the bar center where diffusion effects would be least was about 5 X 1014 atoms of * 34Cs per gram of graphite. The agreement is lO « : : ' ' 1 ' not unreasonable 0 100 200 300 400 500 6C0 700 800 Data for 30-year * 37Cs are also shown in Figure 62. DEPTH (mils) For comparison, the accumulated decay profile of the 37 Fig. 6.2. Concentration of cesiom isotopes in MSRE core parent 3.9-min * Xe is shown as a dotted line in the graphite at given distances from fuel channel surface. upper ieft of the figure. This was estimated assuming that perfect stripping occurred in the pump bowl with a mass transfer coefficient from salt to central core graphite of 03 ft/hr,4 and a diffusion coefficient of Xe 2 5 I37 ! in graphite (10% porosity) of 1 X 10 ""* cm /sec. similar profiles for Cs. Some of these along with 3 7 profiles of other rare-gas daughters Here used in an Near the surface the observed ' Cs profile is lower analysis by Kedl2 of the behavior of short lived noble than the estimated deposition profile; toward the center gases in graphite. Xenon diffusion and tne possible the observed profile tapers downward but is about the formation of cesium carbide in molten-salt reactors estimated deposition profile. This pattern should de­ have been considered by Baes and Evans.3 velop if diffusion of cesium occurred. The central concentration is about one-third that near the surface. An appreciable- literature on the behavior of fission Steady diffusion into a cylinder6 from a constant product cesium in nuclear graphite has been developed surface source to yield a similar ratio requires that in studies for gas-cooled reactors by British investigators Dt/r* = MM 4. For a cylinder of 2-cm radius and a salt (Dragon Project), Gulf General Atomic workers, and by circulation time of 21,788 hr, a cesium diffusion workers at ORNL. coefficient of about 7 X 10"9 cm2/sec is indicated. The profiles shown in Figure 6.2 indicate significant diffusion of cesium atoms in the graphite after their Data developed for cesium-in-graphite relationships in 7 formation. The 5.27-day half-life of ,33Xe must have gas-cooled reactor systems at temperatures of 800 to 1100°C may be extrapolated to 6S0°C for comparison. The diffusion coefficient thereby obtained is slightly below 10"1 °; the diffusion coefficient for a gas (Xe) is 1(a). S. S. Kirslis et al., "Concentration Profiles of Fission 5 2 Products in Graphite," in the following MSR Program Semi- about 1 X 10" cm /sec. Some form of surface annu. Progr. Reps: Aug. 31, 1970, ORNL-4622, pp. 69-70; diffusion of cesium seems indicated. This is further Feb. 28, 1970, ORNL-4548, pp. 104-105; Feb. 29, 1967, ORNL-4119, pp. 125-28; Aug. SI, 1966, ORNL-4037, pp. 180-84. (b) O. R. Cuneo et al., "Fission Product Profile in 4. R. B. Briggs, Estimate of the Afterheat by Decay of Noble Three MSRE Gtaphite Surveillance Specimens," MSR Program Metals in MSBR and Comparison with Data from the MSRE, Semiannu. Progr. Reps: Aug. 31, 1968, ORNL-4344, pj. 142, MSR-68-138 (Nov. 4,1968). 144-47;fW>. 29,1968, ORNL4254, pp. 116,118-22. 5. R. B. Evans III, J. L. Rutherford, and A. P. Malinauskas, 2. R. J. Kedl, ,4 Model for Computing the Migration of Very Gas Transport in MSRE Moderator Graphite, II. Effects of Short Lived Noble Gases intoMSRE Graphite, ORNL-TM-1810 Impregnation, III. Variation of Flow Properties, ORML-4389 (July 1967). (May 1969). 3. C. F. Baes, Jr., and R. B. iivans III, MSR Program 6. J. Crank, p. 67 in The Mathematics of Diffusion, Oxford Semiannu Progr. Rep. Aug. 31, 1966, ORNL-4037, pp. University Press, London, 1956. 158-65. 7. H.J dsNordwall, private communication. 34 ststotentiatea by the soq>tio& behavior reported by 63 FISSION PRODUCT CONCENTRATIONS ai&tead* tef me cesium-nuclear graphite system. ON MSRE SURFACES In particular Mii^tead has shown that at temperatures of 800 10 1t00*C »d concentrations of 0.04 to 1.6 mg E.L. Compere E.G Boh'mann of Cs per gram of graphite, ceaum sorption on graphite The recovery of segments of surfac; from the fuel : 2 follows a lreundhck isotherm 11.6 mg of Cs on 1 ro of circulating system of the Molten-Salt Reactor Experi­ graphite surface cotresjKJiids to the saturation surface ment in January 1971 has permitted the direct com­ cot£*ou >d CiC»). Below this, a Langmuir isotherm is parison of the intensity of deposition of several fission indicated. In the MSRE graphite under consideration, product isotopes at a number of points around the u the "'Cs conum was ~i0 atoms per gram of circuit. Activity determinations were available on seg­ graphite, and ih* 133 and 135 chains would provide ments of a central graphite bar and a control rod shniia' amounts, equivalent to a total content of 0.007 thimble from the core center, on a segment of heat rag of Cs per gram of graphite. At 650°, in the absence exchanger tube and shell, and on specimens cut from of tmerference from other adsorbed species, Langmuir the pump bowl mist shield. Most of these determina­ adsorption to this concentration should occur at a Cs tions have been described by members of the Reactor partial pvnsux of about 2 X 10 ~18 at . At ths m Chemistry and the Metals and Ceramics Divisions in this ptesa*ft, vesium transport via the gas phase should he and the preceding reports. negligible, and surface phenomena should control. In Table 63 we present these data expressed as atoms To some extent, Rb, Sr, and Ba atoms also ave per square centimeter for comparison with each other, indicated to be similarly adsorbed and likely to diffuse and with a maximum mean deposition intensity given m graphite. by the MSRE inventory aivided by total area of It thus appears that for tirr*s periods of the order of a graphite and metal in contact with flowing fuel salt. year or more the aikaU and alksune earth fcughters of Comparisons between graphite and metal for various noble gases can be expected to exhibit appreciable isotopes in various core regions do not indicate any inigmtioft in the moderator graphite of gssUen-salt marked difference in affinity or sticking factor between reactors, the two substances, except that possibly "Tc is more strongly deposited on metal. Deposits on graphite appear more intense at the bar center. For 13SSb, strong depositions occurred in almost all locations, 8. C- E, Mifctead, "Sorption Characteristic.? of the Cesum- Gnplttte System at Elevated Tempeotare* asd Low Cft-hun particularly on metal — it appears necessary for the • tmbon % 199-200 (;96*>. outer graphite regions to be lower than elsewhere to

TaMe 63. Fiaum paoiaet concentration ON graphite and metal surfaces in MSRE (1014 atoms/cm2 )

li5 12 7 106 95 Sb Te Ru Nb "Tc inventory/tota? floware a it i 52 127 3050 Graphite Metal Graphite Metal Gtaphite Metal Graphite Metal Graphite Metal

Core carter lop 6.9 2,4 6,13 17,26 150 Middle 22 IS 6 3 40 15 100 90 1500 Bottom 9 36 4 10 11 18 50 120 2S0C Heat Exchanger Tabe 15 5 7 23 1200 Start 29 8 7 29 2200 Pimp tow] Safeeurface 31 5 14 22 1500 Interface 86,54 385/1 55 iUy within inventory. Tellurium, an antimony daugh­ bulk metal serves as a measure of its irradiation history, ter, is somewhat similarly though pechaps less intensely and the detection of 60Co activity on surfaces should deposited. serve as a measure of metal transport from irradiated Ruthenium-106 was found more strongly deposited in regions. Cobalt-60 deposits were found on segments of the core than in the heat exchanger and most strongly coolant system radiator tube, heat exchanger tubing, at the gas-liquid interface in the pump bowl (as was and on core graphite removed from the MSRE in l2SSb). January 1971. Because over a dozen half-lives had elapsed before The activity founu on the radiator tubing (which counting, the 95Nb data are doubtless less precise but received a completely negligible neutron dosage) was appear similar to the ruthenium pattern. ~160 upm/cm2. This must have been transported by Generally these data show somewhat higher inten­ coolant salt flowing through heat exchanger tubing sities of deposition than reported9 for surveillance activated by delayed neutrons in the fuel salt. The heat specimens; turbulence and mass transfer rates may have exchanger tubing exhibited subsurface activity of about been less for surveillance specimens. 3.7 X 10s dpm/cc metal, corresponding to a delayed The mass transfer coefficients cited by Briggs10 neutron flux in the heat exchanger of about IX 101 °. indicate that deposition should vary with flow condi­ If metal were evenly removed from the heat exchanger tions from region to region, and also should depend on and evenly deposited on the radiator tubing throughout sticking factors presumably characteristic of the surface the history of the MSRE, a metal transfer rate at full material and substance transported. Mass transfer coef­ power of about 0.0005 mil/year is indicated. ficients for xenon atoms in various regions of the MSRE Ccbalt-60 activity in excess of that induced in the were given as: core center 15%, 0.3 ft/hr; core average, heat exchanger tubing was found on the fuel side of the 0.06 ft/hr; heat exchange;, 0.7 ft/hr; piping, 1.2 ft/hr; tubing (3.1 X 106 dpm/cm2) and on the samples of reactor vessel, 0.6 ft/hr; and 0.02-in. bubbles in salt, 2 core graphite taken from a fuel channel surface (S X ft/hr. The same proportions between regions should 106 to 3.5 X 107 dpm/cm2). The higher values on the hold for colloidal particles (

7.1 THE SOLUBILITY OF HYDROGEN Several modifications were made to the apparatus

IN MGLiEN 2LiFBeF2 during this reporting period in an effort to improve the reproducibility of the data. The extent to which these D. M. Richardsc n W. Jennings, Jr. alterations have aided the experimental method is indi­ A. P. Malinauskas cated by the results for helium which are given in Table The efficiency with which a dissolved gas can be 7.1. These data are still of a preliminary nature. They stripped from a liquid depends in part on the solubility were taken while a considerable inleakage of argon, cf the gaseous species in the fluid. Therefore, the rate which is us^d as a cover gas for the circulating pump in of removal of tritium in the MSRE circuits, both the strip section, was known to occur. intentional (in the helium sparge) and unintentional The hydrogen data, which are also presented in Table (through th? heat exchangers), is governed to some 7.1, again display an uncomfortable degree of scatter. extent by the solubility of the gas in the pertinent We now believe this scatter to be a manifestation of air molten salts. For this reason, hydrogen solubility inleakage over prolonged periods of time, with resultant studies in molten salts have been undertaken. interactions between the oxygen and the hydrogen- The experimental method and apparatus have been metal-salt system. The lattermost hydrogen result which described earlier.1 In brief, the apparatus is of the is tabulated was obtained after sparging the salt with two-chamber type which was firstemploye d by Grimes, hydrogen over an extended period of time. This run was Smith, and Watson,2 but modified to accommodate also the only one of the three involving hydrogen in effects which arise because of the ability of hydrogen to which complete removal of hydrogen in ti»? stripper migrate through metals. The molten salt under investi­ chamber v.-as indicated. However, the difference in puritv between tliis run and that immediately preceding gation is saturated with hydrogen in one of the two is due almost entirely to helium of a still undetennined chambers, and, after saturation has been attained, some origin. of the fluid is transported to the second chamber. In this second chamber the hydrogen is stripped from the Shortly after the last hydrogen run listed in Table 7.1 salt, and in auxiliary apparatus the amount dissolved in had been completed, two hydrogen recovery tests were the known volume of liquid is determined. performed. These tests involved admitting a known amount of hydrogen to the xenon strip gas in the 3 stripper chamber (which contained 622 cm Li2BeF4 at 600°C), circulating the mixture through the salt, 1. J. E. Savola ner. and A. P. Malinauskas, MSR Program then attempting to recover the hydrogen admitted. The Sermmm. Progr. Rep. Ftb. 28, 1971. ORNL-4676, pp. 115- fraction of original hydrogen recovered as a function of 17. 2. W. R. Grimes, N. V. SmUh, and G. M. Watson, / Phys. time is shown graphically in Fig. 7.1. The purity of the Chem 62,862(1958). gas collected at the termination of recovery run 1 was 57

Table 7.1. Sohibflity of hethim and hydrogen in Li2BeF4

Temperature Salt transferred Gas collected Gas f°C) (cmJ) (cm*@STP) *"** 10^

He 6u5 585 5.239 0.252 6.17 He 60S 622 2.619 0.536 5.99 He 600 287 2.020 0.337 6.22 He 601 287 1382 0.553 7.07

H2 604 579 3.454 0.732 11.51

H2 604 634 8.026 0.819 27.17

H2 600 622 2.506 0.525 5.46

The Ostwald coefficient Kc is defined as the ratio of *he concentration of the gas in the dissolved state to its concentration in the gas phase (assuming ideal gas phase behavior).

0RNL-0WG 7t-<3200 7.2 PERMEATION OF METALS BY HYDROGEN 1.00 J. H. Shaffer A. P. Malinauskas o W. Jennings, Jr. W. R. Grimes bJ (t / > o / Accurate evaluation of tritium migration in an MSBR o / UJ will depend, in part, on estimates of its permeation 4 10.95 rates through the metal walls of the fuel am* coolant systems. These estimated transport rates are currently based on diffusion coefficients and solubility constants y • / derived from relatively extensive data that are available / in the open literature. However, the extrapolation of / 0.90 these transport rates to low hydrogen pressures shows 1O0 200 300 significant departures from their classical dependence ELAPSED TIME (min) on the square root of the hydrogen pressure. This

Fig. 7 1. Fraction of original hydrogen recovered from the dependence on square root of H2 pressure at higher scl'ib'lity apparatus strip section as a function of time since hydrogen pressures is due to the dissociation and admission of the hydnjen into this region. Upper curve, association of hydrogen as the rate-controlling step. recovery nil 1; lower curve, recovery run 2. Smoothed results Departures from tiiis pressure dependence at lower, obtained f.om both the annuius and the stripper chamber collections were combined to yield the results presented here. hydrogen pressures are presumed to be due to surface adsorption phenomena as the rate-controlling event. Thus, estirm'es of gas transport rates at very low

97.3% H2. wheieas that of recovery run 2 was 95.1% tritium pressures in an MSBR (assumed to be dependent

H2. In both casas it was assumed that this purity on \/P) may be erroneous. This experimental program obtained throughout the experiment, and was charac­ has been directed toward an evaluation of hydrogen teristic of the ga collected through the stripper annuius permeation rates through metals at hydrogen pressures as well as the stripper section itself. On this basis the less than 10 tons where departure" from the PW* amount of hydrogen collected through the annuius dependence have been reported. region only amounted to about 5% of the total col The amount of hydrogen q which will pass through an lected. This is in marked contrast to the result reported area A of metal per unit time is given by the relation earlier1 when no sal: was present in the stripper chamber; we now feel that the earlier value was grossly q = -DA in error. The important poinf is that we can recover at dx' (1) least 90% of the hydrogen from the stripper chamber within a 2-hr period. Further experimental work is where D is the diffusion constant (area/unit time) and c currently in progress. is the concentration of hydrogen (cm3 @ STP per cm3 58

of metal) at any point x within the metal. For a round for the increase of pressure Pb as hydrogen diffuses tube taving length / and a radius r = or, the hydrogen through the metal cylinder from pressure Pa. flux

V4-in.-OD Kovar metal (54% Fe, 28% Ni, and 18% Co) /=

q=[2*ID/ln(b/a))(Ca-Cb). (3) the operating temperature of 495°C and to define the thermal gradient of the furnace. Gas pressures were The dissolved gas concentrations can be interchanged determined from an electronic pressure meter (MKS with gas pressure by the Freundlich relation to yield the Baiatron type 77) using two differential-pressure-sens- equation ing heads having 0* to 10- and 0- to 1000-torr ranges. Hydrogen used in the system was passed through a q=[2*IDKIto(b/a))(P2-Pl), (4) palladium diffusion unit for purification. The vacuum system was of conventional design with mercury diffu­ sion and oil pumps. where £ is the gas solubility constant. In the first set of experiments, Pf, was maintained at By material balance the amount of hydrogen q pass­ zero and the quantity q evaluated from incremental ing through the metal tube per unit time may also be changes in/*,. An average value for q at an average value expressed as for Pa for each experiment was determined by the method of least squares. In the second set of experi­ dna drtff Q = (5) ments, Pa was held constant and q was evaluated from dt dt incremental changes in P^, where Pb - 0 at / = 0. Extrapolations of the data from each experiment to t = For ideal gas behavior 0 yielded instantaneous gas transport rates at Pj, - 0 at discrete values of P . Thus, under both experimental ap« yV'i ap vbj a fc conditions the equations defining the pressure depend­ q (6) dtiRTai~dtfRTbj' ence of the diffusion process could be reduced to

where i and / denote the incremental isothermal sec­ \nq = n lnPu + la(2*1/Inb/a)DK (9) tions of each gas reservoir and 7* is the absolute temperature. By combining Eqs. (4) and (6), changes in The results obtained by least squares regression analyses the hydrogen pressure associated with the diffusion from some 30 experiments according to this equation process are related to the hydrogen pressure by the yielded a value of n = 0.560 ± 0.011 and a value of DK= equation S.18 X 10~'' moks/torr"-cm-mia (limits of standard error = 4.95 to 5.42 X 10"1') at pressures forP, of 1.4 to 800 tons. The direction of hydrogen flow through q^—J^^^IDK/hiib/a^iP^-Pl), (7) the test cell had no significant effect on the experi­ mental results. Although the results of these experiments demon­ for the decrease in pressure Pa by diffusion into a strate some deviation from the PU* pressure depend­ volume at pressure Pb. Conversely, ence of q, the experimental apparatus was not suffi­ ciently sensitive for evaluation at much lower hydrogen q=^}lmfS U«M/ln(*/«)lCS -/"&), («) pressures contemplated for an MSBR. Consequently, further work on this program has been discontinued pending results from a similar study using man spectro- metric techniques and much lower pressure ranges. 59

73 TRITIUM CONTROL IN AN MSBR TTLS reaction was followed to completion at 100°C by constantly monitoring the effusing water vapor. The tritium generated in an MSBR must be prevented Nearly 100% agreement beiween the theoretical mass of from escaping into the environment. Some removal H 0 and that accounted for by the mass spectrometer (and containment) of tritium as T , HT, or TF from the 2 2 indicated that, indeed, 1 mole of water was produced primary fuel system is expected. However, the ease of by 2 moles of decomposing NaBF3OH. At 373°C, 13 diffurion of hydrogen isotopes through metal (and 3 X 10~ g of H20 effused in 30 rrin through an orifice especially through the large area of thin metal in the 3.16 X 10"3 enr in area. By use of the Knudsen heat exchangers) ensures that a large fraction of the equation, the pressure was calculated to be 2.44 ± 0J04 tritium will proceed through the heat exchangers and X 10 "$ aim. This pressure value was used to calculate eventually to ihe outside world unless it can be held up the standard free energy change for the above reaction: by chemical means or by efficient diffusion barriers.

= 73.1 Mass Spcctroraetiic Examination ^73-K ***lnp

of Stability of NaBF3OH = 75 kcal/mole. C. F. Weaver J. D. Redman Further heating of the residue to 800°C yielded only

If hydrogenous material (i.e., NaBF3OH) can be BF3 and NaF vapors. The BF3 effused over the range incorporated in reasonable quantity in the NaF-NaBF4 245 ± 5 to 800°; NaF vapor appeared at 725°C. secondary coolant, the tritium diffusing from the fuel circuit of an MSBR could be held up by chemical 732 T^Thenr^StabartyofNitraie^itriteMixtwes exchange C. F. Weaver J. D. Redman

T + NaBF3OH ^ NaBF3OT • H A study of the nitrate-nitrite mixtures was initiated as part of an evaluation of their potential use as coolants for a period suiTicient to permit its controBed removal in molten-salt reactors. In such salt mixtures as tUTEC, from the coolant circuit. This possibility has received, NaN02-NaN03-KN03 (40-7-53 wt %\ the reaction and is receiving, considerable attention. We have investigated with a TOF mass spectrometer H2 + 2KN03 * 2KNOa + H,0 the thermal behavior of several of the pertinent mate­ 3 rials. A previous report has described the behavior of (which has a large negative staudard free energy

NaBF4, NaOH, and the products of reaction of H20 change) may afford the means to convert elemental

with NaBF4. We have studied the thermal stability of tritium to tritiated water, and thus provide a means to

NaBF3OH and the composition of gas produced during control its distribution. its decomposition over the temperature interval 25 to Since citrates and nitrites are known to decompose 800°C. thermally, it is useful to identify the vapor products of The starting material w&3 shown by x-ray diffraction the above reaction to determine what additional species

to be nearly pure NaBF3OH. The material began to are formed. la cider to establish the needed back­

decompose at 90°C, and H20 was the only gaseous ground for interpretation of such data, the separate product. The reaction, as suggested previously,4 is components were first investigated. probably: Sodium nitrate was dehydrated in a Pyrex flask by passing dried helium gas through the molten salt for

2NaBF3OH(s)*Na,BaF<0(s) + H20(g). several hours at temperatures just above the melting point, 306£eC. The product was colorless and did not

The H20 was shown to be free from impurities by mass adhere to the container. Samples of th. salt were spectrometric analysis. transferred to a nickel Knudsen effusion ceiL The gases from the heated eel were analyzed with a TOF mass spectrometer. The only vapor products at 380 to 4O0*C 3. C. F. Weaver, J. S. Gil, and J. D. Redman, MSR Prvgnm were NO and Oj. These permanent gases do not alow Semimm. Progr. Rep. Feb. 28,1971. ORNL-4676, pp. 85-87accurat, e pressure measurements because of background 93. 4. L. Kolditz and Chenc-Shoc Lung, "Condemtion of Ftaor- interference, but approximate values were NO * 1.6 X dboamr Z. Chem 12,496(1967). 10~* torr, 03 = 2.1 X 10"* ton. The presence of 60 oxygen leaves little doubt that tritium will be oxidized. nation occurs at a rapid rate until most is recombined.

The behavior of KNO3 and NaN02 is being investigated The reaction of NO and 02 is kinetically third order; by experiments now in progress. In subsequent experi­ the rate increases slightly as temperature is decreased. ments we expect to observe the vapors over HITEC salt The nitrogen dioxide associates (rapid v and reversibry) with and without H2 - to dinitrogen tetroxide at tempera.ores of 100 to 200°C, with release of an additional 6 to 7 kcsl/mole

7.4 WSSOCIATING-GAS HEAT TRANSFER SCHEME NG2. The dinitrogen tetroxide can be condensed with a AND TRITIUM CONTROL IN MOLTEN-SALT fairly low heat of vaporization. (The heat of vaporiza­

POWER SYSTEMS tion of N204 is 9.1 kcal/moie at the atmospheric boiling point of 21°C, and of course diminishes to zero E. L. Compere at the critical temperature of 158°C and 99 atm.) The The use of a dissociating-gas heat transfer system using ease of vaporization at low temperatures and the rela­ tively high heat of dissociation at high temperature may nitrogen dioxide (N204 ^ N02 * NO + 02) (? •* N2 + facilitate the recovery of thermal energy from the 02), under development in the U.S.S.R., appears to offer some interesting possibUities to the Molten-Salt moltefrsalt system.

Breeder in terms of mitigation of tritium losses from Though both N02 and NO are thermodynamically the power system. Under dissociating conditions the susceptible to decomposition into the elements, rates effective heat capacity and effective thermal conduc­ appear acceptably slow. Any decomposition of N02 tivity of the gas are increased several fold, resulting in appears first to produce NO, which may decompose increased efficiency of heat transport and the possi­ further, so NO is the critical substance. The thermal bility of lower equipment costs. decomposition of nitric oxide as reported by Yuan, 6 In the Soviet fast reactor proposal,5 pressurized nitro­ Slaughter, Koerner, and F. Daniels and Fraser and 7 gen dioxide is the primary fluid, removing, heat from Daniels proceeds by both a second-order homogeneous fuel elements and driving a gas turbine. Thermal and mechanism for which the rate at 600°C is indicated to 7 -1 1 radiation decompositions are by implication not signifi­ be ~4 X 10" X p\tm, moles titer hr" and a cant, and ,4C production was not mentioned. Similar heterogeneous, zero-order reaction for which the rate of 6 usage in molten-salt systems, though replacing both a 600°C is indicated to be less than about 3 X 1C" 2 1 secondary salt and a steam system with the dbsc^iating- moles/m" hr' . Though not trivial, such rates may well be tolerable, de~nding on processing and makeup gas system, would involve the possibility 01 leakage of f nitrogen oxides and oxygen into the primai-y salt circuit requirements in particular systems. In any event the and subsequent reaction with graphite. Although such heat of decomposition of NO, ~20 kcal/mole, is of the reactions would doubtless not be extremely violent - same order as heat transferred, and there is no increase probably the gases would behave about tike pressurized in molecules on decomposition. Consequently any de­ composition into N and 0 would require release of air — the use of nitrogen dioxide to transfer heat 2 2 these gases and makeup, but little hazard should ensue. directly from molten-salt fuel will not be further con­ sidered here. The materials of construction should be stainless For a Molten-Salt Breeder Reactor, the dissociating steels, or chromium containing alloys such as Inconel gas system could drive a gas turbine, replacing the steam (or HasteBoy N) which can be heated in pressurized air tufbine system; the primary coolant presumably would to the temperatures in question. Oxide films will build be lithium beryllium fluoride or some other such salt. up on the surface in the usual way and inhibit corrosion Heat would be transfened to nitrogen dioxide at 100 processes. atm or more, podsmh/ reaching temperatures of 600 to Tritium entry into the power system would be inhibi­ 700*C. At temperatures above about 500°C, appreci­ ted by the films. It will become diluted by the entire able (and rapidly reversble) dissociation into NO and gas phase, reducing its activity. Furthermore, any trit­ 0» occurs (absorbing about 14 kcal/mole). As the gases ium entering the system should be oxidized and re- pass through the turbine and cool, exothermic recombi- 6. E. LYowetaL, "Kioetk^ of UieD«»aipo#t«-of Nitric Oxide in the Rang* 700-1800*," J. Phyt Chem. 63,952-56 5. A K. Kaato et aL, Atomnaya Entrgfya 30, 180-85 (1959). (Febraarv 1971); ttandtsed by F. Rertea, The BRG-30, Exper­ 7. J. M. FISMT aad F. Daaieb, The Heteroteaeoas Decoat- imental Power Plant with a GmCooled, Pat Reactor amipodtk a m of Nitric Oxide with Oxide Cttth/rti," /. Phyt Chem. DmaoemtmtMeat Tramfer Agent. ORNL-tr-2500. 62,215-20(1958). 61

tained in the form of TNO3 and T20 vapors. These 1. The ability to block a major tritium path to the should react relatively slightly with oxidized walls, sc environment. little escape is indicated by permeation of corrosion 2. The recovery of such tritium as may enter the hydrogen through the metal. The gaseous T 0 or TN0 2 3 system in a concentrated form. in the system would occupy the full volume (~105 liters) of the heat transfer system, which thereby would 3. The lower equipment costs because of improved have appreciable capacitance before processing was thermal transport properties. required. (The ~2400 Ci/day of total tritium produc­ 4. Improved thermodynamic efficiency. tion is 0.04 moles/day, most of which should not even 5. Less restriction on properties of intermediate cool­ penetrate into this system.) ant salt, since vapor generation can be accomplished Processing to remove such tritium as enters the with possibly greater ease. nitrogen dioxide system could probably be accom­ plished by various schemes, batchwise or on side Hazards and uncertainties include: streams: adsorption, freezing, or distillation suggest 1. Routine handling of toxic or noxious gases under themselves. Addition and removal of H20 could readily pressure. provide an isotope dilution effect if desired. Thus the 2. The question of the irreversible decomposition of major modes of escape of tritium from the power nitrogen oxkles into the elements. system which remain are by leakage, either through turbine seals or into the condenser water. It would 3. The relation between chemical reaction rates, heat appear necessary to prevent leakage of N02 and such transfer, and flow rates when aB rates are high. burden as it has of tritium into condenser water, and to 4. The effectiveness of the oxide fUms in preventing contain or recover any leakage past turbine seals- This tritium passage has not been evaluated. appears required in corresponding steam systcnw also, but tritium is thought to enter the steam systems 5. Recovery methods for recovery of such tritium as considerably more readily. enters the system are undefined. In either system the diversion of tritium from the 6. Cost comparisons with other systems (steam) have power system implies a requirement that it be recovered not been made. from the primary circuits. Recovery from the primary On balance the use of nitrogen dioxide as a dnsociat- system E. not discussed here. ing-gas thermal fluid for a Molten-Sap Breeder Reactor In summary, possible advantages of a nitrogen dioxide appears to merit further consideration. power system thus include: 8. Processing Chemistry

8.1 THE OXIDE CHEMISTRY OF Pa4

IN MOLTEN LiF-BeF2-ThF4 (2) C. E. Bamberger C. F. Baes, Jr. ^h X X R. G. Ross D.D.Sood1

A study was initiated previously2 to determine the where X denotes mole fractions, it was necessary to precipitation behavior of PaflV) m LiF-BeF2-ThF4 determine the composition of the solid phase. Accord­ (72-16-12 mole %) when oxide is introduced. This ingly, ve decided to isolate and examine directly the information is needed not only in connection with the few milligrams of oxide phase present. development of possible MSBR fuel reprocessing meth­ The flanged top with the stirrer assembly was ods based on oxide precipitation, but also because it is removed from the cooled equilibration vessel and obviously relevant to the determination of the oxide replaced by another top provided with a l-in.-OD nickel tolerance of MSBR fuels. filter to be used for removing the molten fluorides at The resultsreporte d previously should correspond to temperature. The system was reheated to 570°C under the equilibrium flowing H3 and kept at temperature for 40 hr before we attempted to remove the molten fluorides, "i Ins permit­ ted ^dissolution of any solid phase that might have PaF4(d) + Th02(ss) precipitated on cooling. Only 10% of the fluoridephas e *M,(s} + TnlMd), (1) was subsequently removed, probaoly due to plugging of the filter. The system was again cooled to room where d denotes a dissolved species and ss a solid temperature and the procedure repeated with another solution phase. Such an exchange rerction is to be filter. This time we successfully removed all but a small expscted on the basis of the similarity in size of the fraction of the fluoride phase. After cooling, the sobd 4 4 ions Pa * and Th * and the fact that regular solutions of residue was loaded into a %-in. nickel tube with a

UOa-Th02 are formed from ftioride melts upon oxide fritted bottom, and the remnant of the fluoride phase additions.3 In order to confirm the above presumed was forced out of the compartment at temperature reaction (1) and to estimate its equilibrium quotient using If) pressure on the inside and vacuum on the outside of the compartment. 1. Goest starntiu from B'labha Atomic Research Centre, A portion of the oxide residue was repeatedly washed Bombay, Mm. with hot "Verbocit"4 solution, followed by treatment ICE. buabcifer, R. G. Ross, and C. F. Baes, Jr., MSR Progmm Semkmmt. rtogr Rep. Feb. 28. 1971. ORN?^4676, pp. 120-22. 4. "Verboat" solution: (developed by the Analytical Chem­ 3. C. E. Bambemer and C. F. Baes, Jr., / NucL Meter. 35, istry Division, ORNL) SO g sodium venenata • 20 g 177 (1970). citnte m 200 ml mnuated boric acid flotation. Final pH * 9.

62 63 with IN nitric acid solution at 70°C. It was then 0.13 to 0 33 depending on the value assumed for the washed with acetone and dried. Gamma counting solubility piouuct of Th02 and the amount of oxide indicated the solids to contain 27.9 mole % as Pa02 • No present initially.) Phase II probably precipitated as an significant amount of elements other than Pa, Th, and artifact of oxidation by impurities during the filtration O were found by spectrcgraphic analysis and analysis procedure and could consist of mixed aggregates of for fluoride. The results of these analyses were (in PaOj+x and ThO:, where x < 05. ppm): Li= 10, Be < 1, Ni = 30, Cr = 30, F«; = 200, and The composition of Phase I (XVtQ = 0.175), which F = 1700. X-ray diffraction showed, surprisingly, that is assumed to have been at equilibrium with a melt two fee phases were present, giving: containing X?M¥A = 2.7 X 10^ at 567°, gives (£» = 94.4.

I. Major phase (60 to 90 mole %), Assuming, as was the case for the U02-Th02 solid a = 5.5926 ± 0.0003 A. solutions, that the entropy change for the exchange 0 reaction (1) is zero, we obtain II. Minor phase (10 to 30 mole %),

flo = 5.5429 ± 0.0024 A. log (ft - k* (X"°>X™A = i M (lOW. (3)

^Th02*PiF4y

No Pa s*as dissolved during the treatment with HN03. Since the amount of fluorine found was quite low relative to the Pa present, it was concluded that nc significant amount of a Pa oxyfhioride phase was This estimate, along with the estimated solubility product of Th0 , leads to the predicted Pa4*-*)2" present. 2 The purified oxide sample was examined with the precipitation behavior shown by the smooth curves in Scanning Electron Microscope (SEM). The presence of Fig. 8.1. The calculation was performed as follows: First the mole fraction of Pa0 in the equilibrium two distinct phases was confirmed, the most abundant 2 phase consisting of large weil-formed octahedral crys­ oxide solid solution was calculated for each point from £?£h [(eq) 3 ] and the observed mole fraction of PaF : tals, 5 to 25 p on a side, and the other of small,

Phase I (large crystals), 173 ± 1 &% Pa . = 2 + + ,, Kho2 "r.o2) i Phase II (small crystals), 43.9 ± 4% Pa . which, in terms of ^Fa0 and QThQ , becomes Use of the above results to calculate the relative 2 _ abundance of each phase gives 61 mole % of Phase I and V*PaF4 *P«F4J 39 mole % of Phase II, which is in fair agreement with lP»O earlier estimates based on the intensities of lines a obtained by x-ray diffraction. 1 Doe to the marked difference in morphology of the

Xt F = initial mok fraction of PaF4 before oxide oxide under midly oxidizing conditions. This prediction addition, was based on measurements of the assumed equilibrium

JIT02- = mok fraction of dissolved oxide. s %Pa205(c) + /4ThF4(d) ^ PaFs(d) + %Th02(c) ,

If it is assumed that 2.5 millimoks of dissolved oxide (1) was initially present, the previously reported results »oi0.-i<«(wn£F4) (the points so corrected in Fig. 8.1) agree well with the = 5.94-9.98 (103/7*), calculated curves. Work presently continues to obtain additional Q^ combined with the previously measured equilibrium6 values with other solid solutions more dilute in Pa and to test further the assumption that the Pa0 -Th0 2 2 UF (d) + Th0 (ss)^ U0 (ss) + ThF (d) , phase is a regular solution. The data obtained thus far 4 2 2 4 (2) indicate that in the event of an accidental contamina­ log Q* = log (jTUOa ' *ThF4/*Th02*UF4) tion with oxide of an MSBR or an MSCR, the precipi­ = (2376 ±48)- \03/T, tated phase would consist mainly of a UO2-Th02 solid solution with little Pa0 dissolved in it. 2 where c, ss, d, and X denote, respectively, crystalline and solid-solution phases, dissolved species, and mole

OKML-OW6 71-0629 fractions which gave ! • - _ 1

\ \ i ViaOsfc) + %UF4(d) ^ PaFs(d) + %U02(ss) , \ . t \ tog(23 = iog(jrp,F5fiu02/4^4) O) \ \ \ i %> i \ \ <^r 30»C = 5.94-7.01 (103/r). \ i ^^ \ *—^S??*0 ti I. \\ i where Q3 relates the concentration of PaFs in the salt \ s^56 7«c \ | i phase (in mok fraction units) to the activity of 1 j U0 (fl ) when Pa 0$ is present. The value of Q a 2 UO2 2 3 a. 1 1 estimated in this way was sufficiently small to suggest Ii \P»" 563#C 1 that the concentration of PaF5 could be lowered by i \ ! oxide precipitation to a value zs low as 10 ppm in the \ i presence of 03 mole % UF without precipitating U0 - \ 1 1 4 2 25 50 75 100 In order to confirm that Q3 is indeed small enough to C?~ AOOeO (m'.bmoli/kq) achieve such a selective precipitation of protactinium, reaction (3) was measured directly by equilibrating

F«. 8.1. CoMcatntiMorPaF4 aiLiF-BeF2-ThF4 (72 16-12 molten LiF-BeF2-ThF4 (72-16-12 mok %) containing

•nfc %) • tquBbamm with Pa02-Tb02 »id sotatioas. The initially 03 mok % UF4 and 0.06 mok %PaFs (2300 abscissa shown the total oxide added to the system (as ThO*). ppm) with precipitated Pa(V) oxide and U0 -Th0 The lines were calculated with log Q^ = IM/T(°K) and 2 2 2 solid solution formed in situ by the addition of Th0 . assuming that 2.5 mM O were initially present. 2 Agitation was provided by sparging argon through the melt, which was contained in a copper liner, w,th a conical bottom, in a nickel vessel. A small amount of 8.2 THE OXIDE CHEMISTRY OF Pa5* IN CuO was added to the system to establish a relatively URANIUHMX)NTAINING MOLTEN oxidizing condition and thus assure that all the protac­

UF-BeF2TbF4 tinium was in the pentsvalent state. Filtered samples of the melt were obtained using copper filter sticks of R. G.Ross C. E. Bamberger CF.Baes.Jr. Previous measurements5 on the precipitation of Pa(V) by oxide in molten UF-BeFj ThF (72-16-12 mok%) 5. R. I Ross, C. £. Bamberger and C. F. Bees, Jr., HSR 4 Ftogmm Saiimwu. Frogr Rep. Aug. 31,1970, ORNL-4622, p. led us to predict that protactinium could be efficiently 92. precipitated from an MSBR fuel without precipitating 6. C. E. Bamberger and C. F. Bees, Jr., /. NucL Mater. 35,

any uranium (as U02) by the controlled addition of 177 (1970). 65 various porosities, concordant results from which indi­ Combination of the present direct measurements for cated that no contamination of the filtered samples Q3 with the expression for Q7 gave the additio al with oxides had occurred. The samples were analyzed values for Qx shown in Fig. 83. Also shown are the 23S for uranium (sufficient U was present for determi­ previous direct measurements of Qx. The revised nation by delayed-neutron counting) and for protac­ expression for Qx, indicated by the line in Fig. 83, is tinium (by gamma spectroscopy). The results obtained were used to calculate values of Q at various tempera­ 3 log Ct = (449 ± 0.87) - (8.66 ± 0.86) y-. (5) tures which are shown in Fig. 8.2. In these calculations of Q3, the activity of U02 in the oxide phase was estimated from the concentration of UF4 and the The measured values of Q$ thus ar.) consistent with 5 previously determined values of Q2 and 7uo2- Also those predicted over a year ago from measurements of shown in Fig. 8.2 are values of Q3 derived by Qx and Q2. It should be noted in Figs. 8.2 and 83 that combining the previously measured equilibria (i) and most of the vaiues of Q$ and Qx obtained from (2). A least-squares fit of all the weighted data gives measurements in the absence of uranium show a positive deviation from the least-squares fit. Presently, we believe that this could be caused by the presence of

log Q3 = (4.49 ± 0.87) - (5.69 ± 0-86) ~ (4) and is shown by the line in Fig. 8.2. 71-13202 TEMPERATURE CCJ ORNL-0MG 71-1320! 750 700 650 600 550 T r TEMPERATURE CC) 750 700 650 600 550

0.95 1.05 f-15 1.05 1.15 1.25

F*. 8 J. Values F*8J. VataesofC, =XPaF /xf£F4 n*anmd directly lOVTT0*). The tine represents the least-squares The line represents the combination of the expression for Q$ fit of all the data. (Fig. 8.2) and for

appreciable amounts of Pa** in the previous determi­ ORNL-OWG ^-13203 nations of Qx. It was assumed in these experiments, wherein mckel oxide WAS added, thai all the protac­ tinium was oxidized to the pentavaknt suite. In view of the uncertainty in the potential of the P> ^/Pa4* couple, this inty not have been the case. When improved values of the redox potential become available it will allow us to correct ttase data for this effect, although it is expected th*t the correction will not be i large one.

The valaer. of Qt a~ttl £3 (raw a ho been measured by NlaSeo * Wn! "a*?ig fltfvfc -fcwfcr initio concentrations of protactinium (100 ppm). His results show more scatter, probably reflecting the greater difficulty of achieving equilibrium with the much smaller amount of Pa(V) owde phase present. The resulting plots of Qx and Q3 vs 1/7* cross ours at --670°C, but they a* much steeper, in&aliag much more positive AS values and much more negative A// values for reaction; (1) and (3). We feel that the **sults reported here are more accurate not only because they show less scatter, but also because the :e»ultiag AS values are much more consistent with what one would predict from estimates of the absolute entropies for the reactants aod prodwru. The value of & obtain** by us at 600°C (0.009) agrees within a factor cf 3 with s va>* of 0.027 derived from the results «f Talent ai>d Smith (Part IV. this report i, who measured the ecadftferiurti

I 4PaJ0$(ii+ 5HPf«^PaF5(d)+ 2.5H,0(g) . (*) Fig. 8.4. Concentrations of PaF5 calculated by means of log VpiFflJoJXlJFj = 449 " 5-69 U&tn for the solvent

This agreement is n&anly good since, in order to derive UF-BeF2-TliF4-UF4 (72-16-12-0.3 mole %) at equilibrium w'h a value of Q-3

%UO,{*/ + S*m$* %W i*)+ 2 -5H O(g) (7) 4 a temperatures, calculated by means of Eq. (4), are plotted as a function of the activity of oxide ion in the estimated* from measurements « a different solvent melt. In an MSBR fuel (X a 0.003) we estimate (0.67UF-0.33»eF,). {if4 that a , must exceed -0.95 before a U0 phase The consistency u. Progr. Rep. Feb. 28, 2 5 directly because of the difficulty of isolating a suffi­ 8. ^ f. I*,**. Jr. *» \V*n|K*iuny>*> Reprocessing of Nuclear ciently large and pure sample of the protactinium oxide Fads." Midi Xeuilurp, V* 15, toNF 690801.1969. phase. 67

83 REDUCTIVE EXTRACTION DISTRIBUTIONS ORMrOWG 71-13204 cpm/i, of metal. I53BJ OF BARIUM AND THORIUM BETWEEN 50 100 200 500 1000 2000 BISMUTH-LEAD EUTECTIC AND BREEDER FUEL SOLVENT D. M. Richardson J. H. Shaffer

The eutectic mixture of bismuth and !ead (56.3-43.7 mole %) offers the advantages of a low melting point (125°C) and zero volume change on freezing; it should also be somewhat less aggressive than pure bismuth toward container materials. These properties were sufficiently attractive to merit further examination. 50 100 200 500 1000 2000 Distributions of barium and thorium between the ppm Th eutectic melt and LiF-BcF2-TliF4 (72-16-12 mole %) Fig. 8.5. Reductive extraction from Lar-BeF -ThF were determined at 650°C in a 4-in. IPS, SS 304L vessel J 4 (72-16-12 mole %) into bismuth-lead eutectic (56.3-43.7 mole with a mild steel liner. Barium fluoride was added to %)at650°C. the fuel solvent salt to make 9.1 X 10"3 mole % (with 133Ba). Reductions were performed by successive additions of C.25 or 0.5 g of clean lithium metal; This is about one-half the solubility of thorium in pure samples of salt and metal phases were taken after a 12 bismuth at 650°C. minimum of 5 hr of argon sparging at 1 liter/min. It is apparent from these data that the Fb-Bi eutectic The distribution data obtained are shown in Fig. 8.5 is less valuable for this particular separation (though it together with the derived lines (with theoretical slopes). is quite acceptable) than is pure Bi. It is clear that if the These lines arbitrarily pass through the log-average of low freezing point, low volume change upon freezirg, the first 11 data points. This weighting of the sample and probable less corrosivity of this eutectic are of real results is based on the assumption that phase segrega­ value additional separation studies should be under­ tion in the frozen metal pellets caused the measured taken. barium and thorium concentrations to be low in the later stages of reduction.9 The equilibrium quotient for 2 2 barium was: DBJ{DU) = 9.810 X 10 , 2.4 times less than reported for this salt and pure bismuth.10 The 8.4 REMOVAL OF CERIUM FROM LITHIUM equilibrium quotient for thorium with eutectic metal CHLORIDE BY ZEOLITE 4 was: DThl(DLi) = 6.635 X 10*, 3.7 times grester than D. M. Richardson J. H. Shaffer reported for this salt and pure bismuth.1' 3 The barium activity of the metal phase was essentially The observation that cerium (as Cc *) is partly constant following the last three additions of 0.5 g of removed from molten LiCl solutions by finely pow­ 13 lithium and would indicate that the solubility limit of dered Linde Zeolite 4A was reported earlier. The thorium in the eutectic had been reached. Unfortu­ same results have now been demonstrated repeatedly in nately the sample data scattered badly, and additional an experiment where the dried zeolite was exposed, special samples were not taken. Examination of the using filter tubes, in the form of commercially supplied data points suggests the thorium solubility in the No. 8 mesh spheres. Fission product processing feasi­ eutectic may be approximately 1500 ppm at 650°C. bility is indicated, at least for cerium, by observed loadings of as much as 0.13 g of cerium per gram of dry Zeolite 4A.

The initial salt was approximately 1 kg of UCl-CeCl3 (99.5-0.5 mole %) with several milhcuries of 144Ce. 9. D. M. Richardson and J. H. Shaffer, MSR Program Semiannu. Progr. Rep. Feb. 28, J971, ORNL-4676, p. 131. 10. J. C. Mailen, F. J. Smith, and C. T. Thompson, MSR Program Semiannu. Progr. Rep. Feb. 28,1970, ORNL-4548, p. 290. 12. C. E. Schilling and L. M. Ferns, MSR Program Semiannu. 11. L. M. Ferris, J. J. Lawrance, and J. F. Land, MSR Progr. Rep. Aug. 31,1968, ORNL-4?44, p. 297. Program Semiannu. Progr, Rep. Feb. 28,1969, ORNL-4396, p. 13. D. M. Moulton and J. H. Shaffer, MSR Program Semi­ 284. annu. Progr. Rep. Aug SI, 1970, ORNL-4622, p. 109. 68

Purifications and subsequent exposures to zeolite were established, cumulative encrs introduced in material conducted in the same 4-in.-IPS nickel vessel. balance calculations prevented further evaluation of the Numerous 20-mil aliquots of Linde 4A, sodium form, rare-earth removal process in this experiment. No. 8 mesh zeolite were equilibrated to constant weight Chemical analyses for sodium in the salt showed a

(five weeks) over CaCl2*6H30 solid and saturated steady increase and indicated, as shown in Table 8.1, aqueous solution at 24.5°C. Each aliquot was dried in a that exchange with lithium was essentially complete. filter tube for 18 hr at 375°C with argon purge. Th? This finding is contrary to the reported equilibrium filter tube was then transferred under continuous argon quotient BtfJ&u - 78.4 for this zeolite in LiCl at purge to the extraction vessel and slowly lowered into 6S0°C,14 and suggests that a processing plant for a the molten chlorides at 6S0°C. Salt was then pushed molten-salt thermal reactor would require that Zeolite alternately into and out from the tube by pressure 4A be in the lithium form, with 7Li. Analyses for fluctuations. Inflow was damped by autopressurization aluminum in the salt were sever-1 hundred ppm but of argon in the top of the tube and was terminated showed no rising trend. upon contact cf salt with an electric probe. Contact Zeolite 4A is initially floated by molten lithium times were approximately 20 sec per stroke; contacted chloride, but filling of the void space between crystal­ volumes were 10% of salt inventory per stroke. Al­ lites with LiCl causes the spheres to sink to the bottom. though SO strokes were usually made per aliquot, no Complete filling of the void space between crystallites significant increase of loading was noted from 20 to would result in the consumption of approximately 0.16 100 strokes. g of lithium per gram of dry, lithium form, Zeolite 4A. The exposed zeolite was recovered as loose spheres, Molecular inclusion of lithium chloride within crystal­ unaltered in appearance except for a film of salt on the lite cavities would increase this consumption by possi­ surface. It was very radioactive and could be monitored bly 50%.*s This consideration involving conservation of with a survey meter. Since the specific activity involved materials would need to be included in the final an indeterminate amount of salt, however, the amount evaluation of a zeolite process. of cerium removed per aliquot was computed from Further experiments are intended to measure the physical inventory, and the decreasiig radioactivity of removal of other fission products, both divalent and filtered salt samples removed after each batch exposure. trivalent, from molten LiCl by zeolite. Wide variations The data obtained are shown in Table 8.1. Within the may be found since the possible mechanisriiS include precision of the data the distribution of cerium bt *en ion exchange, reaction with the zeolite structure, and the molten chloride and the solid zeolite phases can oe formation of molecular inclusion <~ jmplexes. expressed empirically by the equation

In (ppm Ce in salt) = 12.163 + 1.35 In (g Ce/g zeolite) 14. W. A. Platek and J. A. Marinsky, /. Phys. Chen 65,2118 for concentrations down to 4600 ppm in the salt phase. (1961). Although an effective experimental procedure was 15. R. M. Barrer and W. M. Meier,/. Chem. Soc. 299 (1958).

Table 8.1. Removal of cerium from molten LCI by Zeolite 4A

Number of exposures to ppm Ce Gramx of cerium removed 14 g of No. 8 mesh dry Fraction of total in salt per gram of zeolite Linde Zeolite 4A sodium exchanged

1 14,200 0.133 0.98 2 11,500 0.125 0.65 3 9,000 0.115 0.73 4 7300 0.054 0.92 5 6,200 0.071 0.96 6 4,600 0.067 0.72 9. Development and Evaluation of Analytical Methods for Molten-Salt Reactois

A. S. Meyer

9.1 INLINE CHEMICAL ANALYSIS No major problems have been encountered with the OF MOLTEN FLUORIDE SALT STREAMS computer or the voltammeter in this system. Prior to J. M. Dale A. S. Meyer installation on the loop the voltammeter was modified by T. R- Mueller of our instruments group to enable the The first successful in-line analysis of a constituent in counter electrode of the system to be used at ground a flowing molten fluoride salt stream is now in potential. This was done to help suppress any electrical operation. Automated analyses for U(III) in LiF-BeF2- noise that might be contributed to the vokammetric

ZrF4-UF4 (65.4-29.1-5.0-0.5 mole %) in the NCL-21 wave by surrounding equipment. However, on occasion thermal convection salt loop are being routinely per­ the response from the electrodes has been noisy and formed by our PDP-8I computer voltammeter system. erratic, making it impossible to locate the £% of the The loop was set up and is being used by the Metals and U(1V) -*• U(III) reduction wave with any degree of Ceramics Division1 to study the effect of the melt on confidence. It appears that this is caused by some metal specimens in Hastelloy N. material floating on the surface of the melt as it comes The NCL-21 loop was filled on July 20 and held in contact with the electrodes. In order to eliminate this under isothermal conditions at about 650° until July problem a new electrode assembly was designed winch 26, tX which time the cold leg temperature was allows the salt to be flushed from around the electrode established and Hastelloy N specimens were inserted with helium. This assembly was installed in die loop into both the hot and cold leg of the loop for corrosion after the metal specimens were removed. The electrode studies. Analyses of the U(III) concentration of the is encased in a % -in. nickel tube, open at the bottom, melt were started on July 22 and were continued on a which protrudes below die surface of the melt. During routine basis until the specimens were removed from computer-controlled runs the salt enters the electrode the loop on August 23. The origir.il measurements in compartment *rom below the melt surface and remains the melt indicated that about 0.02% of the total there for the time of measurement. The salt is then uranium was present as U(III). The U(III) concentration flushed from the compartment, and the electrode showed a gradual increase until a value of 0.05% was remains in a heliuru jas envelope when not in use. This reached at 475 hr of loop operation. At this point the appears to keep floating material away from the rate of formation of U(III) increased, and the concen­ electrode and also should increase the lifetime of the tration reached a value of about 0.15% when the metal electrodes or electrode area-defining insulators which specimens were removed from the loop. may be added at a later time. It was hoped that this new assembly would also decrease the surface vibrations around the electrode. It was observed during operation J. W. Kocer, Part IV, this report. of the analysis system with the original electrode that

69 70 die derivative vohammogram which is ussd to toczi? probe.3 This probe, somewhat similar to a pH electrode die £% is highly susceptible to small variations in the in shape, makes use of multiple internal reflections of a height of the melt. If the salt loop is given a small push light beam of a selected infrared wavelength range during a run the derivative wave oscillates with »*he wave within the probe to direct a beam of light, which enters created on the melt surface. The new assembly does not the top, through the probe around the bottom and completely eliminate mis effect, but it does dampen the again through the probe finally exiting in a different surface wave in the vicinity of the electrode, and direction at the top. A detector monitors the exiting equilibrium is restored within a few seconds. beam. Since internally reflected Jght is subject to After the system is started the analyses are performed absorption by the medium which surrounds the point completely unattended through computer control. At of these reflections, the multiple-reflected beam is initiation of the analyses a signal from a logic circuit attenuated if the probe is placed in an absorbing mat we added to the computer starts a timer which solution, and absorption measurements are possmle. In causes the pressure in the electrode assembly to be considering the usefulness of such a device it seemed released and salt enters the electrode compartment. The apparent that the utility could be greatly enhanced if computer then operates the voltammeter to perform one cut a slot (see Fig. 9.1) of appropriate width in five analyses for U(IU), and the results plus some some portion of the internal beam path and in a diagnostic information are printed out on a Teletype direction normal to the beam path. With a slot of after each analysis. At the end of the run the average perhaps 0.2 to 1.0 cm in width a probe could be made U(III) concentration and standard deviation are calcu­ with a controlled and relatively much longer path lated and printed out. When the run is completed the length than that which could be realized with only tuner shuts off causing the salt to be flushed from the internal reflection. With a slot the optical design of the electrode assembly. At the present time a set of five probe could be simplified to require a minimum of two analyses is made every hour, although the number of or three internal reflections to direct a beam of light analyses and the intervening period may be adjusted in into and out of a cylindrical probe; the base of the the computer program for the particular needs of the probe would be prismatic, conical, or perhaps hemi­ experiment. The computer program which we have spherical, with the slot in the apex of the prism or on modified to fit our particular situation was originally die side of any of the shapes. By incorporating a developed by M. T. KeOey and R. W. Stelzner.' As an suitable light source and detector with a suitable slotted example of the precision of the analysis system, a optical probe, absorbance measurements could be made standard deviation of 2.1% was obtained for the results in any region of the electromagnetic spectrum. The of the hourly analyses made over a one-weekend period device could also be used for other optical measure­ when the U(1II) concentration appeared to be relatively ments such as turbidity. The design of this probe would stable. lend itself to a scalable insertion into a pool of liquid or One useful addition to die analysis system is now a flowing stream. It should be remembered that internal being considered which involves the measurement of reflection can occur only when the index of refraction the v*lt temperature. During the first month of opera­ (») of the medium through which the light is traveling tion the temperature of the melt where the analysis is (probe) is larger than n of the surrounding medium (the made varied from about 610 to 680°C. Because the liquid sample). Over the common range of values of n temperature is needed in the computer program to encountered, a difference of about 0.S in the two values calculate tie Uflll) concentration, it is planned to of v seems adequate; however, through the use of a monitor an amplified thermocouple output with the specially designed probe bottom a smaller difference computer so that the true temperature at the time of may be satisfactory. analysis is used in the calculations. It is also planned to By the use of a probe made from PkxigUs and using 'nwestigate the extension of the analysis system to the solutions of a blue dye, copper phthalocyanine sulfo­ monitoring of the corrosion products in the melt. nate, placed in the slot, absorbance data were collected and compared with similar data obtained from the 92 SLOTTED fROBE FOR IN-LINE SPECTRAL MEASUREMENTS 2. M. T. Kdky, R. W. Stenur, and D. L. Mtaniaj. JKSft J. P. Young frowm Seittimw. Prof. Rep. Aug. SI, 1969. ORNL-4449, p. 137. A device has been recently developed by Wilks 3. Wiiu Scfcotifk Corporation, South Noiwak, Coaaectkut; Scientific Corporation called a "Miran" infrared Bulletin MI-MOM, Inly 1971. 71

OftNL 0W6 7I-I1827A Iafett9.1. AbaoftaaceolCapMartocyH^vfohrtioa

Abmfeaace/1 « Sana* Carjraj SktAB^piuaC

H20 0.0 0.0 1 0.18S Q.1S7 2 0382 0J84

ousry.4 With a diamond slotted probe, several spectral measufements could be made directly in ItSftR tircatat- ing fuel. Suitable laser hcht sonrccs are mirth ft* either of these appEcaiioas; the refractive inc'ex of either arterial is quite adequate for proper irtemal reflections within the probe.

93 IN4JNEDinnaamA110NOFHYDftOLYSB

PRODUCTS IN NaBF4 COVER GAS R.F. Apple A. S. Meyer

Earifer analytical studies9'* on the oftgri of the

NaBF4 draiiatBBg test loop have shown that water can be present in significant quantities as hydrolysis prod­

ucts of BF3 in the cover gas of the proposed MSBR coolant sarL An inJmc method for the meaiuu—nt of this "water" wiuld be uefid for fe detection of leaks in steam generators, the im«stigatkmof theroteof the cover gas in the "-OBtainment of tritium, the deveiop- ment of methods for the removal of the corrosive hydrolysis products before they can reach m miliir components %n the flow control system, and studies of coolant reprocessing systems. Conventional methods for the determination of water m inert gases are subject to interference from BF* and Vgin. TYP. posaMy HF in the over gas. At the suggestion of Dunlap Scott7 we are investigating "dewpoiut tech­ niques'* for the determination of these hydrolysis Ffc.9.1. Slotted o»4k»l probe te«»ectials«ly*. products. We anticipate that this empirical tfchmqw may require extensive calibrations because the conden­ sation temperature of a given concentration of "water" solutkm with a Cary spectrophotometer, model 1411. may well be influenced by the partial pressures of both The light source used with the probe was a 100 owatt BF, andHF. He-Ne laser Hne at 633 nm, and the detector was a "Deraichron" phoictubi detector. The comparison is 4. I. B. BBSH, H. W. Kofca, I. P. Yoaag, M. M. Many, and shown in Table 9.1. G. E. Boyd, JOB Jreawm Stmtmutu Jvegr. Rep. Feb. 28, In-line applications for spectnd analysts by means of a 1971. OHNL-467*. pp. 94-96 slotted optical probe appear numerous. For molten-salt 5. R. F. Appttt MM! A. S. Meyer, MSR Anwwn Sevawant reactor applications, it is poswble that an LaF slotted Prctr. Rep. Feb. 28.1969. ORNL4396. p. 207. s 6. R¥.AptbhS.M.DaU,L.S Wn4y,—dA.&.Htytt,MSR probe would be useful in monitoring protons by means fhtgmm Semimm. From- K*p. Aug. 31. 1970. ORNL-4622, of the BF,OH" absorption in molten NaBF4; the pp. 116-11. existence of such an absorption was reported previ. 7. Rmctor I***^ 72

In feasibility studies we are using a simulated cover surface, and films of condensate are observed through a gas prepared by bubbling mixtures of BF3 and helium sapphire window. With this cell condensation is ob­ through a saturator that originally ccntains water. When served within about 15 min after the block is cooled to a steady state is reached the satur*?or contains liquid the dewpoint. Ore; the range of 45 to 7S°C dewpoints hydrates of BFa, and the exit gai contains hydrolysis are observed at about 1°C below the temperature of the products ic relatively low concentrations. By direct cover gas. It is likely that this difference reflects the Karl Fischer titration (subject to significant interference difficulty in detecting the initial formation of a film of from BF3) we have estimated "water" concentrations condensate visually. With commercial instruments (not of abot** 200 ppm at a saturator temperature of 4S°C necessarily applicable to our corrosive gases) dewpoints and 3000 pom at 75°C. In our experiments the can be measured to a few tenths of a degree. A dewpoint detector is either contained in the same oven complete evaluation of the precision and accuracy of that maintains the saturate* temperature or is con­ the method must await calibration using gas streams nected to the oven through a short nickel tube that is whose absolute water content is determined by some heated shvM the saturator temperature. Under these alternate method. The Karl Fischer titration applied conditions the observed dewpoint should coincide with after the water is separated fiom BF3 and HF by the temperature of the saturator. azeotropic distillation with pyridine appears to be the Our initial approach was to attempt to detect the most promising method. For the quantities of water formation of a conductive film of BFj hydrates by involved it will be necessary to perform the titrations 9 measuring the resistance between closely spaced plat­ with couiometrically generated reagents. D. J. Fisher 10 inum electrodes inserted in the gas stream. The elec­ and T. R. Mueller have designed an improved trodes are mounted through «-: insulator (temperature coulometric titrator for this application. The instru­ controlled by an air stream) which presides a surface ment has been fabricated and is now being tested. for the condensation of the hydrolysis products. At Initial measurements on standards have shown about present we have used Teflon, Teflon with its surface 1% reproducibility for the titration of milligram quanti­ modified by treatment with a sodium solution, and ties of water. With minor modifications in the elec­ high-fired stamina as insulating materials. Measurements tronic and in the design of the titration cell we expect on alumina appear more consistent; however, this may to achieve similar precision in the titration of 100-jjg be the result of improved electrical instrumentation quantities. This apparatus together with its metal used in the later tests. This technique gives definite azeotropic still will be sufficiently portable to permit indication of the condensation of a rum of hydrates. on-site analysis of water in engineering streams. When the probe (electrode assembly) is about 10°C A preliminary estimate of the potential sensitivity of above the saturated cover gas temperature its resistance the optical dewpoint method has been made by a

B about 500 kft for 20-mil electrodes spaced about % 6 dilution technique. When the concentration of hydroly­ in. apart. The resistance falls to about 300 ft when the sis products in a stream saturated at 59°C (estimated temperature is reduced to 10°C below that of the cover "water" concentration., 1000 ppm) was diluted fivefold gas. In its present state the electrical probe does not with a gas stream that contained the same concentra­ appear to be practical because of its extremely slow tion of BF3, the observed dewpoint decreased by 24°C. response. Several hours are required to approach these This response is roughly equivalent to that of un- equusbrhim resistance values. complexed water at room temperature. From these We are now testing an optical method for dewpoint results we estimate the precision of the method to be detection. The design of cur optical cell is based on a about 10% for visual detection with perhaps a fivefold suggestion of S. S. Kirslis.* The cell utilizes a cylindrical improvement with automatic photometric instruments. copper block with one face polished end gold-plated. Commercial photometric instruments would require the This polished face is sealed into an observation chamber replacement of their conventional glass optics. through which the cover gas sample flows. The external We believe that the optical cell will prove useful for end of the copper block is penetrated to near the various development studies and may provide mforma- polished surface by holes for cooling air and a thermo­ couple. The inlet stream is directed against the polished 9. A. S. Meyer and C. M. Boyd, "Determination of Water with Coulomethcally Generated KarJ Fischer Reagent," Anal C**m.,3i,215(i959). 10. Analytical Instrumentation Group of the Analytical 8. Reactor Chemistry Division. Chemistry Division. 73

tior on the gas phase equilibria between H20 and BF3. species. On heating the latter species it decomposes to In application to pumped systems, however, it will form water and some form of oxyfluorobcrate. probably be subject to interference from oil which From the above it is seen that one particular kind of enters the system through the shaft seals. We will nosdissolved OH species can be identified. It is reason­ therefore continue deveiopmer.t on the resistance able to assume that all OH species could be observed by method of dewpoint detection, which should be un­ their absorbance in this region of the infrared spectrum responsive to organic films, and we will test other so that their presence would be detected. Rather than insulating materials and electrode configurations. rely on this assumption, however, an independent method involving isotonic dilution of H with D was devised so that the spectrally observed BF3OH, or H, 9.4 DETERMINATION OF HYDROGEN concentrations could be compared with H concentra­ IN FLUOROBORATE SALTS tions found by mass spectrometry. If one allows a J. P. Young J. B. Bates quantity of hydrogen is a particular species to react M. M. Murray A. S. K*yer with an approximately equal amount of deuterium, as a

volume of D2 gas, in a sealed system at equilibrium, one From the results which were reported earlier4 for the should find a large and proportionate amount of H in interaction of OH' with NaBF4, it was obvious that the D2 gas. Such an equilibration was studied by protons (as BF3OH~) could be detected in fluoroborate allowing several molten samples of H-containing NaBF4 salts. The detection limits add the quantitative nature or NaF-NaBF4 to react with a known amount of Dj gas of such a determination, however, were unknown. Work in sealed Pyrex ampules fc c various periods of time at this period has been directed toward these latter ends. 440°C. The proton concentration of the original salts It was found that pellets pressed from mixtures of was determined by the infrared pellet technique using

the factor derived from the ground NaBF3OH-NaBF4 NaBF30H and NaBF4 which were ground in a micro ball mill yielded infrared spectra in which the ab- mixtures. The results of the comparison are shown in 1 Table 9.2. sorbance of the NaBF30H peak at 3641 cm' varied linearly with the added concentration of this species. In a 45-mg pressed pellet the resultant factor is 63 ppm H psr absorbance unit. The method is very sensitive; much Table 9.2. DelwJMliw of «ijdioy m WaBP4 mm^m less than ! ppm H could be detected. It is assumed that by iafnied ami anu spectral nHbois the method will be equally sensitive, on a molar basis, H found, pfHB to deuterium. Sample ^ A'."-,. Although a good calibration curve was obtained, the Man spectral Infilled method of preparing the samples did not guarantee that Eutectic 9.9* 20 these "standards" were of known hydrogen concentra­ 21.6* 24 tion. If some of the added BF30H" were lost in the 21.7* 18 grinding and pressing, or, rather, if it were converted to NaBF4 7.7* 6.4 some species which did not exhibit the sharp peak at 7.8 3641 cm"1, the experimentally observed factor would be higher than the actual factor. Indeed, one such effect * 16-hr D2 equilibration. was observed in high concentrations of NaBF3OH or if "48-hr D2 equilibration. the mixtures were ground for too short a time. Under such conditions, rather than one sharp peak, two sharp peaks are observed in the spectrum of the pellets at 3641 and at 3621 cm'1. The former peak is as seen for The correlation of the results is quite gratifying, but

BF3OH" in solid solution in NaBF4. The latter peak is there is an attendant high blank correction .in the mast at the same position as the BF3OH" peak in pure spectrometric results that is vorrisome. We have found NaBFjOH. On mild heating of the pellets, 70°C for 18 that the blank correction, equivalent to 10 to 12 jigof 1 hr, the peak at 3621 cm' disappears with little if any H, is due to Pyrex; the mechanism of the exchange is as 1 enhancement of the 3641 cm' peak. Apparently when yet unknown. The blank is reduced by at l*a»t an order these two peaks are observed, two kinds of BF3OH' are of magnitude if Sr02 ampules are used. Further isotopic present in the NaBF4 matrix: a bound or dissolved exchange studies of fluoroborate melts contained in specie", and an undissolved and probably segregated SrOj ampules will be made. 74

Various parameters of the infrared method of H few hours, however, the current essentially returned to determination in fluoroborates have been evaluated. background level. This is evidence that appreciable Too short a time of mixing with the bafl nail, less than concentrations of hydroxide km are not stable in approximately 4 ntin, or hard grinding yields absorption NaBF4 melts at least under our experimental conditio*?* peaks which give low results. Variation m the relative in which the melt is contained in a graphite crucmle humidity to which samples were exposed did not affect that is sealed in a quartz and Pyrex envelope. Vortam- the intensity, and therefore concentration, of the metry at platinum or pyrorytic graphite electrodes dees BF3OH" absorbance. Even though samples were stored not appear applicable to low levels of hydroxide ion, at 100% relative humidity for 48 hr and showed since background vohammog. *ns do not r-veal any obvious signs of caking from moisture pickup, this wave that can be related specifically to OH reduction. adsorbed water was removed in the pefletizmg process By purposely increasing the OH concentration, how­ at least down to the equivalent of 4 ppm H. Since a ever, one can observe the potential range at which this sample of k&s than 4 ppm H has not yet been observed, substance is reduced. it cannot be said as yet whether the 4 ppm is a real We jre now testing a palladium tube electrode so that concentration in NaBF4 or whether it represents the tiie hydrogen formed at the electrode surface could extent of some hydrolysis reaction occurring during diffuse through the palladium n.ic an evacuated volume pelletization. It would appear, however, that the former and be observed as a pressure Jiange of the system. view is more likely. The would appear to have two distinct advantages; it Most of the fiuoroborate samples that have been would be specific for hydrogen and would aDow for previously melted yield proton concentrations between increased sensitivity through controlled potential elec­ 20 to 30 ppm. The sample shown in Table 9.2 which trolysis. Also the separated hydrogen could be trans­ has 7 ppm has never been melted. When mis sample is ferred to an internal proportional counter for the melted under what is thought to be inert conditions the measurement of its tritium content. The technique hydrogen content increases two- to threefold. This could thus be adapted to an in-line method for JH/H apparent affinity for H, or more correctly CXI since the ratios in the reactor coolant. species being observed is BF3OH", coupled with the To test the feastbflity of this technique, a melt was partial immiscmility of fluoroborates with BeF2- prepared of commercial nonn^rystallhed NaBF4 (esti­ containing melts suggests the possmfity of extracting mated proton level 20 to 40 ppm). A palladium tube OH" from molten fluoroberyllates into fluoroborates electrode %« in. diam, 0.004 in. wall, 2 in. long rvas for the subsequent spectral determinations. Preliminary dosed at one end and fastened to a %-in. nickel tube studies using molten LiF-BeF2 equilibrated with DaO iser. The e^t-.ode was immersed to a depth of ~1 cm. ha/e shown a very small but definite transfer of The evacuated volume associated with the electrode deuterium into the fluoroborate-rich phase, as assembly is of the order of 10 cc. Upon applying a BF3OD", which must have occurred by extraction of a negative voltage step to the electrode, a pressure species from the molten fluoroberyOatephase . Further increase was observed as **)e hydrogen which is formed studies of this will be made. at the surface of the electrode diffused through the palladium into the evacuated volume. Initially the 95 VOLTAMMETWT AND ELECTROLYSIS pressure increased from background (<2 /1) to ~100 fi

STUDIES OF HYDROXIDE ION IN MOLTEN NafiF4 upon applying a 1-V step for 1 min. This is an indication that we were definitely observing the reduc­ D. L. Manning A. S. Meyer tion of protonic species present in the melt. After about Experiments were conducted to observe the voltam- 48 hr, however, the pressure measurements had de­ metric behavior of hydroxide ion in molten NaBF4 at creased to ~30 p for the same potential step and time approximately 400°C. Hydroxide added as NaOH or of electrolysis. This agrees with previous voltammetric NaBF*OH (200 to 800 mg per 80 g of melt) produced observations whjc! seemed to indicate that appreciable an increase in current over background on the voltanv concentrations of OH are not stable in NaBF4 melts mograms over the potential range ~-0.5 to -1.0 V vs a under our experimental conditions. An addition of

Pt quasi-reference electrode. Considerable noise was ~SC0 mg of NaBF3OH to the molten NaBF4 resulted encountered which is characteristic of bubble formation in an increase in the pressure measurements to about at the electrode surface. This is not surprising since 160 u. hydrogen is evolved when OK" ir reduced at the The results are encouraging. It is believed that the 3 indicator electrode (OH" • le •* O * • %H3). After a electrolysis technique at palladium will result in a 75 specific method for detecting protonic speries in 20 ppm with one recrystaftzation, and a rmnanMy fluoroborate melts. We plan to continue these experi­ wdklefined redaction wave at this level was observed. ments. However, to eliminate any effect of '" -a and A voHammetric study is in progress on titassasnQV) also to achieve higher temperatures, fur*; ' ^penV added as K2TiF4 to molten NaBF«. Metts of TifJV) hi ments wffl be conducted in a nickel cell enclosure. NaBF4 appear to be stable in graphite. The TifJV) -> Initial measurements indicate that useful vohammetric Tifjn) reduction wave is cbserved at ~-0 5 V. It may w?.ves for the reduction of OH can be obtained on the prove difficult to separate the reduction waves of palladium electrode. HfTV) and Fefll). A Tr*-• Ti* reduction wave if not

observed in NaBF4 because the cathodic hut of the 9.6 ELECraOANALYnCAL STUDIES met* occurs first.

fNTHENaBF4 COOLANT SALT D. L. Manmng F. R. Clayton1' 9.7 EUCTROANALYTKAL STUDIES CTNTO G.Mamantov13 IN MOLTEN FLUORIDE FUEL SOLVENT D.L. Maturing Voltammetric studies are in progress in molten

NaBF4 at ~420°C. Platinum and graphite eels are used Further vohaaunetric and chrooopotenbometric to contain the melt which is enclosed in aPyrex jacket studies were made at fast scan rates ar*d short transition to maintain an inert atmosphere. A cover gas of hehum times on Ni(Ii) in molten UF-BeF3-ZrF, st 500*C The was maintained under static conditions at a pressure of diffusion coefficient for Ni(U) was evaluated by the approximately 4 psig. Vohammograms were recorded at two methods. For linear sweep voftammetry, the platinum and pyrotytic indicator electrodes (~0.1 cm3 equation for the revenMe deposition of an insoluble area) vs a platinum quasi-reference electrode. The substance is platinum quasMeference is supposedly poised at the equilibrium potential of the melt. Background voham- s 2 l ip * 2.28 X 10 n*l AD*l*Cfl* , mograms recorded on Harshaw NaBF4 as received showed an iron impurity wave at ~~-0.4 V vs the where ip = peak current 0*A),n * election change, C* platinum quaa-ieference. The concentration of iron 3 concentr?.tion (roil), A * electrode area (cm ), D * calculated from the vohammogram agreed well with the 2 diffusion coefficient (cm /sec), and v * scan rare chemical analysis of -200 ppm. Reduction waves were (V/sec). The vottamniograms were recordeda t a pyro- not observed that could be attributed to the reduction lytic graphite electrode (PGE) with an area of 0.1 cm3 of nickel or chromium. Chemical analyses gave 16 and 6 and at a concentration of nickel of 6.7 rnflCPlot s of i^ ppm of Ni and Cr, respectively, which are below vs v1/3 were linear to SO V/sec. From the slope of the practical limits for well-defined voftanunograms. We 3 have not yet investigated stripping techniques for these line, the value of D n 1.07 X 10"* cm /sec Although ions. A small amount of ironfjuT) was added to the melt an unsheathed pyrorytic graphite electrode was used (r« 3 3 • 0.05 cm), the equation for linear diffusion can be to gain some idea of the potential of the Fe * -» Fe * 13 reduction. This wave was observed at a half-wave utilized as pointed out by Detahay, since the quan­ tity (l/r X^/^),/2 h less than about 0.2 at the scan potential of —0.2 V. It appears that the iron impurity 0 rates employed. in the NaBF4 is predominantly FefJI). On platinum, the melt exhibits a cathodic current limit at ~-1.2 V which Chronopotentiogr*ntt were recorded at the PGE at 3 appears to be due to the reduction of boron, while the current densities ranging from 5 to 30 mA/cm . anodic limit appears at ~+1.8 V due to the dissolution Corresponding transition times varied from 0.76 to l 2 of the platinum. 0.028 sec. Within experimental error, the i9rl prod­ uct was constant at 4.69 ± 0.25 X 10~* A cm"3 The magnitude of the iron impurity was significantly 1 2 sec" ' . From the Sand equation decreased by recrystallizing the NaBF4 from 0.1 M HF as suggested by L. O. Gilpatrick (Reactor Chemistry Division). The iron was decreased from "-200 ppm to /cr«/*«I-~liil>i/*C.

\\. Student pwtidpaat. Untonity of Tinnrt>. KaoxvMe. i.1. Coftsataflt, Department of Chenistry, Unfrentty of 13. Paol Defcaay. "New InstnuMaUi Methods in Etectxo- cfccwJtfry,M pp. 115-46, laterscfeace. New York, 1954. 76

it = current density, r = transition time, F = for a two^lectron change.14 Also from the chroco- Faraday, and at a Ni(Il) concentration of ?.6 X 10 "5 potenrjograms, the ratio of forward to reverse transition moks/an3, an average Dralur of 1.OS X 10"* cm2/sec times was approximately unity, in agreement with the was obtained. This b in excellent agreement with the predicted value for the reverable deposition of an value obtained from vottammetry. Within the precision insoluble substance.1 s of the measurements, the same results were obtained using a platinum indicator electrode. Nkkd(il) when reduced at platinum did not appear to form an Ni-Pt surface aSoy under the experimental 14. Gkb Mamantov, D. L. Manning, and J. If. Dale, /. conditions employed. Log (ip - i) vs£ plots were linear BectrotmL Chem. 9,253 (1965). over the range -0.5 to 0.9 ip with the theoretical slope 15. W. H. %cwaa1h,AiuL Chan. 32,1514 (1960). 10. Other Fluoride Researches

10.1 ABSORPTION SPECTROSCOPY OF 0MSBR> where QMSBR * tnc «q«3*>™n» quotient MOLTEN FLUORIDES measured for the disproportionation equilibrium in

LiF-BeF2-ThF4 (72-16-12 mole %). Currently accepted L. M. Toth L. 0. Gilpatrick = activity coefficients yield Q66.34 2 QMSBR - The reverse of reaction (1) has been studied in an 10.1.1 The Disproportionation Equilibrium effort to unambiguously identify the carbide phase in of UF Solutions 1 3 the equilibrium. As indicated in the previous report

Investigation of the disproportionation equilibrium exact reproducibility of the UF3 equilibrium concen­ reported earlier1 for dilute U(III>U(iV) mixtures in tration was not achieved because pure carbide reactants molten fluoride solution were not available. Efforts have been directed at ! obtaining UC, U2C3, and UC2 of greater purity with which to further test the back reaction. Some of these 4UF3 + 2C(graphite) * 3UF4 + UC2 (1)

results indicate that the carbide phase may be UaC3, but the question remains unsettled. has continued. Using LiF-BeF2 mixtures as reference solutions the following UF3/Uto,a, concentration ratios The woiU on the disproportionation equilibrium will were measured where Utota, = 0.07 mole % (Table continue in order that these questions may be settled. 10.1). These data have been used to calculate equilib­ rium quotients for the above equilibrium in both 66-34 10.1.2 Estimation of the Available F ~ Concentrations

and 48-52 mole % LiF-BeF2 mixtures. It has been in Melts by Measurement of UF4 found that at 650°C the equilibrium quotient at the Coordination Equilibria 66-34 mole % composition (designated (? .3 ) 'a *>-25 66 4 Due to insufficient experimental data, activity coeffi­ times that of the 48-52 mole % composition, or Q _ 66 34 cients in ternary fluoride systems are less accurately = 6.25 048-52- Activity coefficient data reported 2 = 7 m known than in binary systems such as LiF-BeF . It has earlier yields 0 . G48-52 8°°d agreement 2 66 34 been noted earlier that the equilibrium involving the with the data reported here. However, when ternary solvent systems are compared

with the reference system of LiF-BeF2, less satisfactory Table 10.1. Equilibrium UF3/U totalratio s for LiF-BeF2

agreement has been found. For example, G66_34 =* 0.5 mixtures in graphite

Solution (mole %) Temperature (°C) (LiF-BeF) 650 550 1. L. M. Toth, MSR Semiannu. Progr. Rep. Feb. 28, 1971, 2 ORNL-4676,p. H». 66-34 0.02S 0.004 2. C. F. Baes, Jr., MSR Semiannu. Progr. Rep. Feb. 28,1970, 48-52 0.13 0.03 ORNL-4548, p. 149-

77 78 two identified species of U(IV) in molten fluorides at ing) Second, if there were a leak in the primary heat

550°C, exchanger, NaBF4 in the coolant would decompose to

NaF and BF3. The degree of decomposition depends on 4 3 UF8 '*UF7 "+F". (2> concentration (of NaBF4 in the fuel salt), on rempeia- ture, and on the vapor space available for the escape of provides a practical means of measuring flm ride ion BF3. BF3 solubility measurements in a few melts concentrations by measurement of the relative amounts composed of NaF-LiF-BeF2-ThF4-UF4 could provide 4 of UF8 " and UF7'~ with absorption specttosoopy. In the information required to determine how these this procedure the concentration of seven and eight factors affect the decomposition of the coolant. coordinated U(IV) are measured directly by using The apparatus and procedures of measurement have 1 1 5 6 c1050mM = 14 and 20.8 liters mole" cm" for seven been previously described. Since the last report, and eight coordinated U(IV) at 550°C respectively. For measurements in four compositions have been carried 4 3 LiF-BcF2 {66-34 mole %) the (UF8 -)/(L'F7 "> ratio is out: measurements have been completed in mixtures 3 0.667 and for LiF-BeF2 (48-52 mcle %) it is 0.177. with 63 and with 80 mole % LiF, nearly completed in With these two reference points, other solvents, for mixtures with 85 mole % LiF, and begun in mixtures example. LiF-BeF2-ThF4 (72-16-12 mole %) can be with 48 mole % LiF. A summary of the solubility data 4 3 scaled. i» is interesting to note that UF8 7UF7 ~ > in six melt compositions is given in Table 10.2. 6 0.667 for LiF-BeF2-ThF4 (72-16-12 mole%) indicating In the last report we noted that, in the composition thit this proposed MSBR solvent is more F" rich (or range 63 to 80 mole % LiF, the Henry's law constant basic) than the reference composition of LiFBeF7 for BF3 solubility varied linearly with the thermo­ (66-34 mole %). These results are in good agreement dynamic activity of LiF. As Fig. 10.1 shows, the results with the equilibrium quotient Q measured for reaction at 85 mole % LiF are in reasonable accord with this (1) in the MSBR solvent, where Q is expected to linear relationship at 700°C; at 600° the deviation of decrease ?s the F~ concentration increases. this point from the line may be an artifact of thi long extrapolation tI80°C) of the data. The lines in Fig. 10.1 do not go through the origin, probably because the 10.2 SOLUBILITY OF BF3 IN FLUORIDE MELTS solubility of BF3 is also dependent on the activity of

S. Cantor R.M.Waller BcF2; this dependence is much weaker than for LiF, but is certain to be of greater importance in composi­ The general objective of this investigation is to relate tions where the activity ratio of BeF to LiF is the thermodynamic behavior of a solute gas, BF , to 2 3 considerably greater than one. the thermodynamic properties of molten fluoride sol­ For the six melts given in Table 102, the temperature vents. The guiding hypothesis for this investigation is coefficient of solubility is negative and is not very that BF , with its unsaturated valence (i.e., its Lewis 3 dependent on composition. The solubility per unit acidity), will readily interact with the more loosely pressure decreases by about one-half for every 60°C bound fluoride ions (often referred to as "free" (~100°F) rise in temperature. The enthalpy of solution fluoride) b the melt. In this part of the investigation, is calculated from the temperature coefficient of we are measuring BF solubility in the system 3 Henry's law: LiF-BeF2; depending on melt composition, this system would be expected to exhibit a large variation in "free" (/In Kff fluoride concentration because LiF is a fluoride donor and BeF2 is a strong fluoride acceptor. This work is also relevant to molten-salt reactors. where R is the ga? constant, 1.987 cal mole"1 °K *', First, boron, with its high absorption for thermal and T is temperature in degrees Kelvin. Values of AH neutrons, can be introduced into the fuel salt as BF3 are listed in Table 10.2; with the possible exception of 4 for purposes of 'eactor control. (The EF3 could be one solvent (85 mole % LiF), the enthalpies of solution readily removed tioir. the fuel salt by iner*-gas sparg- are nearly identical.

3. L. M. Toth, M"R Semiannu. Progr. Rep. Aug. 31, 1970,5 . S. Cantor and W. T. Ward, MSR Program Semiannu. Progr. ORNL-4622,p. 105. Rep. Aug. 31, 1970, ORNL-4622, pp. 78-79. 4. J. H. Shaffer, W. R. Grimes, and G. M. Watson,Nucl. Sci. 6. S. Cantor and W. T. Ward, J/S/J Program Semiannu. Progr. Eng. 12,337(1962). Rep. Feb. 28,1971, CRNL-4676, pp. 98-100. 79

Table 10 J. Solubility* of BF3 in molten LiF-BeF2 solvents; enthalpy and entropy M sohttion

Solvent Temperature Henry's law constant - temperature equation;* r C Atf A5C (at 1000°K) K in mole fraction B? /atm; 1 _I composition ange r.^isured H 3 (kcal/mole) '^almole" °K ) (mole <£ LiF) (°C) Temperature in °K

63 469-654 lnKH = -15.458 +

"Pressure range, 1.3 to 3.0 atm. ^Least-squares fit of the data. • he experimental error in Ku » approximately tSic. ''Measurements in this solvent composition not completed.

CRNL-DWG 71-13205 0.007 vapor phase to the melt at equal concentrations; this

quantity, usually symbolized ASC, is a measure of the 0.006 change in entropy of the gas caused solely by the E o interaction of the melt with the gas. For noble gases 7 8 dissolved in fluorides, ' ASC if zero or slightly m 0.005 negative. Such values may be interpreted to mean that the vibrational entropy associated with the dissolved state of the noble gases is about the same or slightly less 0.004 than the translational entropy of the noble gases in the

gaseous state. In the case of BF3, ASC would not be

z expected to be near zero; BF3, upon dissolution, should 0.003 tzo lose some of its internal degrees of freedom (rotation o and vibration); hence, ASC should be negative. The data I thus far (see last column of Table 10.2) give substance 0.002 1 .to to the expectation; ASC averages about —12 cal mole' > °K~1. There appears to be a trend in AS with mole z C UJ I fraction; the lower the LiF concentration, the more 0.001 negative is A£c. A tempting but highly speculative explanation for this trend is: the higher the local coulombic field (i.e., the higher the concentration of Be3* ions) in the melt, the greater the hindrance to 0 0.2 0.4 0.6 0.8 1.0 rotation of the dissolved boron species (which is almost ACTIVITY OF LiF

certainly BF4~). We shall have to obtain data at

different mole ratios of LiF to BeF2 to determine Fig. 10.1. Henry's law solubility of BF3 w activity of LiF in Molten LiF-BeF? at 600 and 700°C (B. F. Hitch and C. F. Baes, whether or not the trend of ASC with composition h.„Jnorg Chan. 8, 201 (1969)J. holds.

7. W. R. Grimes, N. V. Smith, and G. M. Watson, / Phyt. A second and more interesting thermodynamic quan­ Chem. 62,862(1959). tity derived from the solubility data is the mofcir 8. G. M. Watson, R. B. Evans III. W. R. Grimes, and N. V. entropy associated with the transfer of gas from the Smith,/ Chem. Eng. Data 7,285 (1962). 80

103 FLUORIDES AND OXYFLUORIDES 4NbF5 + Nb - 5NbF4 OF MOLYBDENUM AND NIOBIUM C. F. Weaver J. D. Redman at 100~C with excess NbFs provides a useful synthesis

9 Study i>f the fluorides and oxyfluorides of molyb­ of NbF4. Mass spectroscopic studies indicated that the denum and niobium has continued at an appreciably tetrafluoride was unstable with respect to dispropor- reduced level during the past six months; major donation at 200°C by the reaction emphasis has been placed or mass spectrometric investi­ gation of these materials. Though several unanswered NhF (s)*NbF (s)+NbF questions remain in each case, no studies of molyb­ 4 3 5 denum fluorides or of niobium flui>*ides in molten salt (2LiF*BeF ) solutions were perfor.ned during this 2 unless an overpressure of NbF was maintained. This period. s instability of NbF4 was not noted below 100°C The best procedure for this synthesis, therefore, is to react 103.1 Mass Spectroscopy of Molybdenum Fluorides the niobium metal at 200°C with in excess of liquid NbF 'n an isothermal container until the reaction is The thermal decomposition of solid MoF and the s 3 complete. At that time liquid NbF is present with reaction of Mo with gaseous MoF have been described 5 6 NbF vapor at nearly I atm. After the reaction is previously. One of the reactions observed 5 complete, the temperature is lowered to less than 100°C. Then the top of the capsule is cooled with

2MoF3(s) ^ Mo(s) + MoF6(g) dry ice while the bottom remains near 100°C; the

excess NbFs is evaporated from the NbF4 and is frozen

in the upper cold end of the capsule. The pure NbF4 is of interest because the pressure of gaseous MoF6 will yield the standard free energy change for this reaction, remains in the lower end of the capsule. and, when combined with the standard free energy of The following additional experiments were performed t0 formation of gaseous McF6, will give the standard to improve our understanding of the production and free energy of formation of solid MoF3. The pressure of reactions of niobium and oxyfluorides. MoF« at 700°C (973°K) was 0.79 X 10"* atm, yielding A study of the vapor products from the reaction of

27 kcal for the standard free energy of the reaction Nb205 and F2 was made over the temperature range written above. From this inforr*»,">n, the standard 375 io 550°C. Fluorine was introduced into a nickel formation free energy per bond for solid MoF3 is -55 ± reaction^ffusion cell containing pure, outipssed 10 03 kcal compared with -505 kcal per bond for Nb205. The residue remaining after several hours of

MoF*(g) at the same temperature. I., addition the fluorination was a mixture of Nb307F and Nb31O77F, reaction as identified by x-ray diffraction analysis. The vapor

species consisted of NbFs, NbOF3, and 0}. The current results, together with those from earlier studies %MoF3(s) * V3Mo(s) + MoF4(g)

of the thermal decomposition of Nb03F, indicate that the dominant reactions were: at 700°C yielded a pressure of 4.6 X 10~* atm and hence a AF° of 24 kcal. This number combined with the AF/ of MoF3(s) yields AF/ of MoF4(g) of -49 ±

1 kcal per bond. The errors were estimated from 2NbaO$(s) + 4F2(g) + 3Nb02 F(s) + NbF5(g) • 20j(g) pressure calibration measurements.

9. C. F. Weaver, J. S. Gill, and J. D. Redman, MSR Program 103.2 Mass Spectroscopy of Niobium Fluorides Semiannu. Prop. Rep. Feb. 28. 1971, ORNL-4676.pp 85-87, and Oxyfluorides 93. 10. C. F. Baes, Jr., Reactor Chem. Div. Annu. Prop. Rep. Mass spectrometric studies of NbF previously re­ Dec. 31.1966. ORNL-4076, p. 49. 4 11. F. P. Cortsema aAd R. Didchenko, Inorg. Chem. 4, ported have clarified the procedure for producing this 182-86 (1965). 1 material in high purity. The literature suggests ' and 12. C. F. Weaver and J. S. Gill, MSR Semiannu. Prop. Rep. we h?ve confirmed1 J that the reaction Aug. 31, 1970. ORNL4622. p. 71. 81 and glass-forming beryllium fluoride systems to their gkss transition temperatures. The relationship of increasing

4Nb02F(s) * Nb307F(s) + NbOF3(g) . activation energiet with decreasing temperature to the concept of a vanishing free volume'3 or ccufigurational 14,IS The pressures of NbOF3 from pure Nb02F and from entropy at temperatures above 0°K has b"-£i, + Nb205 F2 are shown below. Since the pressure discussed before' * and results reported for one super­

Pieawne (ton* at tonpe/atore CK) S°UICe 623° 64? 67? 72? 773° 823°

4 No02F 1-8x10^ 6.2 xlO" 4.1x10'* 1.1 x 10"*

5 4 Nb?Os+F2 6JX10" MxIO" MX 10"' M x 10"*

7 calibrations have a usual re&abiaty factor of 2 these cooled NaF-BeFj mixture (60 mole % BeF3).' These pressures are essentially equal, as the above equations measurements have been extended to mixtures con­ require. At 550°C (823°K) the partial pressures of taining 65 and 70 mole % beryllium fluoride where

NbFs and F, were 1.7 X 10"* and 45 X 10~* torr, conductance has been determined as a functioe of tem­ respectively. The partial pressure of 02, obscured by perature. Temperatures ranged from 540 to 329°C, 10S background interference, was definitely greater than the degrees into the supercooled region. 0 F2 pressure. The standard enthalpy, AH , of the second The results are presented in Table 103. For the 65 reaction above was calculated from the mass spectio- mole % BeFj mixture the measured rerisfeoce varied metrc data of both experiments to be 30 ± 15 approximately as a linear function of the ricfcprocal Iccal/moteofNbOFj. square root of the measuring frequency from 10 to 80 In addition, a study of the vapor products of the kHz. The data were obtained with an R-C series- reaction of NbjOj(s) and NbFs(g) was made over the component baJanctng-arm bridge and an all-metal con­ temperature range 350 to 750°C. Below 550°C the ductance cell, previously described.14 Due to the very vapor was a complex mixture of NbF$ (monomer and low resistance of the melts, the bridge (remaining the dimer), NbFj, niobium oxyftuorides, and an oxy- leads used in the measurements) was catibrated as a fluoride polymer. The oxyfluoritte polymer fragment function of frequency with calibrated resistances (2 to

Nb2OFs* has not been observed before, and we do not 10 ft) in series with a 20*iF capacitor. The corrections know the precursor formula. Analogy with ether applied to the data ranged from +0.10 ft at 10 kHz to fluoride polymers suggests that the precursor lost one +0.19 ft at 80 kHz. The values of resistance, extrapo­ ihiorine atom during ionization and that it* formula lated to infinite frequency R„, are given fat the table, was NbjOF4. Above 550°C the vapor was simpler as together with the magnitude (Aftl#^.) and relative shown below. resistance change (oft/R.) between 10 kit and Rm: Also listed in Table 103 are data for resistances of the Piaasae (torr x 103> 70 mole % BeFj mixture. Here the Measured resistances

Spede (corrected for the bridge cafibration) appeared Inde­ * 600° 625° 650° 700° 750° pendent of frequency from 10 to 80 kHz within the

NbFs 2 A 34 1.8 24 4.3 limits shown.

NbOF3 20 130 130 65 Arrhenius-type plots of the logarithm of measured NbiOF3* precursor 0.72 04 0.36 0.2^ I* resistance vs the reciprocal absolute temperature are

13. M H. Coben and D. TurnboB./ Chem. fhys. 31, 1164 104 ELECTRICAL CONDUOTVITT* OF MOLTEN (1959). AND SUPERCOOLED MIXTURES OF NaF-BeF, 14. J. H. Gibbs and t. A. Diftferzto, S. Chem. fhyt. 28,373 (19S8). G. D. Robbins J. Braunstein 15. G. Adam and I. H. Gfcb*. / Chem. Phyt, 43,139 (196S). 16. G. D. Robfeim and J. BraiMttein, MSR Progmn Semi- Measurement of electrical conductances in the molten mm. Prop. Rep. Aug. 31.1970. ORNU4622. pp. 98-100. NaF-BeFj system has continued with a view toward 17. G. D. Robbtns and 1. Branmteta, MSR Program Semi- relating the temperature dependence of conductance in mm. Prop. Rep. Feb. 28.1971. ORNL4676, pp. 109-110. 82

TabfcUD. Riaulstusi of •oHf and suewcoofcd taken graphically from Fig. 102 range from ll.3 to NaF-toF] atixtwes 15., kcal/mofc for NaF-BeF2 (65 mole %) and from 10.} to 12 kcal/mok for NaF-BeF) (70 mole %) over NaF (35 *ofc fttteF, (65 Molt *) S the temperature intervals indicated. Based on a glass r(°o *.(«> A«,^.(n» A*/*„ (%) transition temperature of l!7°C (see next section), T/Tg <°K) for NaF-BeF, (65 mole %)» 147 to 134: 454.7 1,67 0.13 74 454 6 1*9 C.13 7.7 T/Tg for NaFBeF, (70 mole %) « 2.14 to 1*1. Over 4444 IAS 0.20 10.8 the same T/Tg range in the pyrtdinium chloride-zinc 444.0 1.90 0.!5 7.9 chloride system," activation energies were 6., to 10.$ 436.7 2.03 0.20 9.9 kcal/mok for PyCl-ZnC!} (65 mok %, interpolated) 431.3 2.22 0.15 6.8 and 5* (extrapolated in T) to 7* kcal/mok for 432-f 2.15 0.17 7.9 7 419 J 2.59 017 6.6 PyCl-ZnCI: ( 0 mok %, interpolated). This roughly 398.2 341 0.18 S.l parallels the increase of activation energy with de­ 35!4 AjLh creasing temperature obseived here. At 450°C the 37 M SAO 0.21 3.9 activation energies for these NaF-BeF, mixtures are 358.9 6.90 019 2J approximately I to 2 kcal/mok higher than for the 349.2 8.22 0.23 2J 339.7 940 047 34 corresponding LiF-BcFj mixtures. 32*4 £1.74 040 4.3 10 J GLASS TRANSITION TEMPERATURES NaF (30 snott %Ht*Fj (70 s* **) IN THE NaF-idF, SYSTEM r(°o JUa> 1 TfO *«*> G. D. Robbtns J. Braunstetn 5644 1.22(t003) 1 4834 7.46 (*042> 5404 1.43 (t043) 4794 249 (*042> The investigation of glass transition temperatures in

5284 149 (*042) 479.2 245 (t042) the NaF-BeF2 system has continued, their relation to 521.9 147 444.1 341 (t044) tions; Tg't for additional compositions have been 4954 2.13(i043) 4344 4.25 1*043) obtained and some of the previous experiments re­ 4944 2.21 (*043> peated. The lower portion of Fig. 103 shows a composite of previously reported experimental glass transition tem­ peratures phis new data for compositions of 35,70,85, shown ;.•> Fig. 102. The data were taken *n the order and 90 mok % berylltum fluoride. These were deter­ mdicctec by the numbered poinu, for NaF OS mole mined by differential thermal analysts3' employing %>BeF* (65 mole %) over a four-day period, and the techniques already described.20 The open symbols Mat* (30 mole %)-BeF, (70 mole %) data over a span of represent the temperatures at which a transition was 16 days. Attempts to supercool these mixtures to lower observed in plots of temperature difference between an temperatures were unsuccessful AJJOJ reference and the fluoride glass sample vs the On termination of these experiments, cell constants temperature of the fluoride sample. Duplicate values are were determined as a function of depth of electrode indicated by ticks on the symbols. The average value of immersion (the major variable) and melt volume in Tg at 3 given composition is represented as a solid aqueous 1.000 demal KC1 solution. These will be used to calculate the composition dependence of specific conductance from the data given here and that previ­ 18. A.J. Easteal and C. A. AnteD. / toys. Oiem. 74, 3987 ously reported.17 (1970). Preliminary Arrhenius coefficients (activation ener­ 19- C. 0. RoMrins and J. Braunstetn, MSA Program Semi- gies). mum. Prop. Hep. Aug. SI. 1970. ORNM622, p. 99. 20. G. D. Robbins and J. Brauntiein, MSR Program Semi- mum. Prop Hep. FeS. 28.1971. ORNI/4676. pp. 110-112.

F ,4575*191* 21. Obtained with the apparatus Y. L. O GUpatrkfc, whose technical advice is gratefully scknowteifed. 83

OMNL-M* 71-4320* / CC) SQO 900 430 400 390 1.2

12 10

6

UQUKXJS 6 9

*

0.4

— 2

1 1.70

(far NaF (35 aMfc ftWs «5 note ft) i (31) state *>»»% (70 an* ft).

symbol with an error bar of ±2*C attached, and straight the lower convoattion limit for forming reprododble line segments connect these solid symbols. gbsies is between 36 and 38 mok % BeF3.

Investigation of a sample of 35 mole % BeF2 Glass transition temperature drops with increasing quenched from 850 to 0*C produced the transition beryllium fluoride content nati the Squid coaapoaiUon temperatures shown (the numbers indicate the onkr in from which the glass wis quenched appioaches die which they were observed), the temperatures shifting to primary phase field of BeF, (the approximate phase lower values on successive cycling between 50 and diagram'2'3' is shown in the upper portion of the 150*. Heating to highet temperatures produced very figure). little variation of Tg with conmoaftfon is little thermal effect on crystallization of the super­ observed between 50 and J5 mole % BeF,. The size of cooled liquid, yet the crystalline solid transitions were the thermal effect associated with the gam transition in sizable. This indicates the formation of very little glass uui region, nowsver, occreases wren tncnsaamg net*] and mostly crystalline phase on the initial quench, with content. While the 03° tempframe change at 8S mole precipitation of more crystaline material on each of the % is measurable, the temperature change at 90 mole % 50 to 150° cycles. Previous^, under the*; experimental conditions, we have failed to observe * glass transition temperature following quenching of a 30 mole % BeF3 mixture, while a reprodudble Tg was measured at 38 22. R. E. Thowa (•*.), Urn* Dkpmm of Nwckm Reactor Mttentb. ORNL-254S. pp. 34-35 (Noveafter 1959). mole % BeFj. Hence, it would appear that, at least 23. D. M. Rov, R. Roy, and E. F. Osbom, / Am. Cenm. under the bulk quenching conditions employed here, Soc. :*, 185 (195;). 84

ORNL.-MK Tl-W*?

H*~i no _i_ _i_ 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0

F«.ia3. traNttioa lenpentves for the system NsF-BeF2.

0< BeF2 is less than 0.1 ?. Accordingly, the 90 mole % in which conductance has been measured at a higher values are less certain thin the other data, and several temperature. However, the apparently small (or negli­ different experiments at this composition have been gible) variation of glass transition temperatures from performed. Theie arc labeled A, B, and C in Fig. 10 J OiO to 0.90 mole fraction beryllium fluoride raises the and represent three different equilibration times and possibility of metastable phase separation of the under- two different batches of homogenized starting material. cooled liquid into two liquid phases. Among the three

The average Tg of 116° at *BeF: * 0.90 is probably previous investigations of phase relations in the NaF- 24-37 uncertain by ±6°C. Glass transitions in pure beryllium BeF3 system, there is considerable discrepancy. fluoride could not be observed, presumably due to the Roy et ill." prepared 1 Of quenches of glasses from 60 6 shniiarity in heat capacity of liquid and glass. However, to 100 mole % BeF3; Vogel and Gerth,* who formed since BeF2 is a known glass former, it appears that the their glasses by pressing them between SiOj pellets. region over which bulk-quenched glasses are formed extends from 37 (±1) to 100 mole % BeFa, that is, including the primary phase fields of B«F3, NaBeF2, 24. H. Ramon, pp. 235-48 in Inorganic Glass-Forming and Na2BeF4, but not NaF. Systems, Academic. New York, 1967. In relating the temperature dependence of activation 25. D. M. Roy, R. Roy, and E. F. Osborn, / Am. Ceram. Soc. 33,85(1950). energy for electrical conductance to glass transition 26. W. Vofri and K. Gerth, Gkstech. Ber 31,15 (1958). temperatures, one desires a Tg corresponding to the 27. M. Imaoka and S. Mtzusawa. /. Ceram. Ass. Japan 61,13 gUss-to-liqukl transition where the liquid phase is that (1953), as reported in ref. 24. 85

1>Me 104. Appear ancc of NaF-BcF2 gkstm

Mok%BeF2 Visual appearance Microscopic appearance*

43 Clear glass Clear glass SO Clear glass Clear glass 55 Clear glass Clear glass 70 White, bright Ckar glass transtncent, bjhtfy opalescent 85 White, opalescent Some dear-brown pieces, soaae with dear matrix and sparse brown (oxide)

90(A) White, opaque Ckar matrix with brows (oxide)

IBCavwCnVl CVTSQBUZWUIOH 90(B,O White, opalescent Saaae as 90(A) 100 DoB-to-dirty Clear matrix with many gas

precspitatton

*G. D. BrentoA, Reactor)

were only able to produce clear glasses over the range appeared dull due to dissolved gas bubbles and did not

40 to 72 mole % BeF3, glasses of higher BeF2 content show the incipient (oxide) crystaflizatscfL Electron being opalescent or opaque; Imaoka and Mizu- micrographs ot small gold-plated spcuuicm from these sawa34*37 formed molded glasses from 45 to 75 mole samples have been obtained.1' A preliaainaty issterpre- 2S % BeFa. Furthermore, Vogel and Gerth reported utkm of the tmuoguphs indicates kittle or no surface microphase separation, as determined by electron structure on the cleavage surfaces crfniost of the tjanes microscopy, down to 49 mole % BeF2 of region 05 to (resolution «0.5 M). with some rnterestiag (and dif- IK- ferent) patterns from the two 90 mole % satrapies. Thus, We have attempted to determine if the bulk

29. L. D. Holett,Anaryticaia«naWry Ofr*>oB. 30. A. S. Dworkm and M. A Bredfe,/ Chem Er%. Dm* 15, 28. G. D. Bronton. Reader Chemistry Division, private 505 (1970). communication. 31. G. Brunton, private connnanication, 1971. 86

TsMr 103. Hmttamdmaormoiwm*

(°K) (kcal/nofc)

LiBF4 5S3 3.46 5.94 5.9

NaBF4 679 3.25 4.71 516 1.61 3.1 7.9 KBF4 843 430 5.10 556 3.30 5.9 113

RbBF4 855 4.6* 5.5 51t 2J6 5.5 UJO OBF4 S2S 4.5* $J 443 1.94 4.4 9.9

2 paper* reports that there is no iransition in UBF4 LiBF* bquidus and the eutectic in the LaBF44JF between room temperature and the melting point, whie system. From the Kquidus temperature, the mole % 3 another ' leporu a transitioa at about US'C We UF. and the heat of fusion of L*F4. the tme therefore have measured 'he enthalpy of LiBF4 from temperature of fusion is calculated to be 310*C. The room temperature up to about 40* above its melting eutectic cooceatnsuo*: can also be estimated to be ~-5 temperature to complete our Uiermochesnica; studies of mole%LiF. the a&ag metal fluoroborates. Table 103 compares the rnthalpifs and eauropies of We found no evidcacs for a transitioa either in the rusion and transition for the aJkai mesa! Stouboratcs. enJuipy measurements or in a separate thermal M«yss The high-temperature forms of the fluoioborates of experiment. UBF4 is hygrotcooic and emst be bandied sodium through cesium acquire considerable entropy at in a dry, inert atmosphere as it was m our work and m the transition temperature, probably due to amoric mat of ref. 32. However, this was not the case in the rotatjonal or nbratioaal disorder." Their entropy of work repotted in ref. 33 where in fact the L1BF4 was •testing, therefore, is lower than that for UBF4, ground to a fine powder m the open and even heated m although the sum of the entropy of tranrifioa and an ope* system for the differential thermal analysis netting (AS. + AStr) is higher than that for LnBF«.

NaBF4 differs in both high- and lovMemperature A chemical analysis performed in the Analytical structure from the other fhuxoborates as wel as from Chemistry Division showed that ow sample contained 3 L1BF4. This is reflected in its intermediate value for mok % LsF. Our measured data were therefore cor­ rected for thh impurity. The foiowiag equations represent the corrected enthalpy data for LiBF4 in It.7 WXVXAUTYOFMXmGmUzW&tAM cal/mok: A. S. Dworkin M. A. Bredsg

HT-Ha9t~-\IA¥)+3\29T+IA The small deviations from ideality of nmxing large 2 1 s BeF " ions with smal F" ions and the larger deviations X 10" 7* • 530 X 10 r* (298 to 583*K>, 4 of mixing saoalaxty huge but much more polar izaofc!" ions with F~ ions have been discussed elsewhere.14 It A"r.sfc>a * 3460 caj/mole; AS fMi01l was of further interest to examine mixtures of 1' with 1 1 3 -S^vcaldef- Jtok' (583*K). BeF4 ~ ions of similar size but different pobrirabibty.

An estimate of the degree of dissociation of the BeF4*~ H„-H„. *-ll,490*40.1 7(583 to 700°K). km in dilute molten iodide solutions can also be made from a study of this system. Indeed, the phase diagram Our thermal analysis experiment showed two breaks at of Li?BeF44Jl determined by thermal analysis showed 304 and 300°C. The breaks most probably indicate the interesting deviations from ideality. The system wouM be truly binary only if the fluoroberytbte ion remained

32. S. Cantor, D. P. McDermott, and L O. Gilpathcfc. / Ckem. Phyt 52.4600 (1970). 33. R. J. Manno and E. R. Shinier. Thrmochim. Acta 1, 34. M. A. Bntffc. Ckem. Dh. Atom. Prop'. Rep. Hey 20. 521 (1970). /97/.ORNL-4706;p. 156. 87

undhaociated- Tim does not appear to be the case in its •n- dilute Nations in Lil (Fig. 10.4). The dashed hues *m represent initial slopes of an ideal Lfl bqnidus for one particle per lh BeF4. n * I (undissocnted Brf^'l, and for if * S (complete dissociation to I Be1* and 4F~ ions). The experimental aquidus appears to start with a slope approaching the n * 5 line but then strongly curves to and apparently beyond the M * I line. Thus, the Li1Bef4 seems to show a high degree of Associ­ ation only in very diute solution. At the lowest 20 40 «0 W0 Li, Lil concentration measured, about 3 note % Lis BeF4. only about 10 to 15% dissociation is indicated. The rate at which the degree of dissociation decreases with nv Ffe.lfet.Tfct U3BsF4-UL

Li*BeF4 concentration is difficult to ****** of the noujdeaiity of mixtures of T and 2 BeF4 " ions. Tins nonukaity is apparent from the phase diagram at and near the eutectic coinposition.

The much greater dttsoemtjott reported earlier in an free energy of mixmc, Mtu»«F4 > °* begins at about MSR monthly report was most Mkely due to tne IS to 20 mole % Li. TmsWumor may be compared of oxide in the Li (-1 mole %) winch may with that MI rinauhr dnjeuseed34 for fluoride-iodide

the rordrnf to BeF4*~ + mixtures, especially those with a com O2" -» BeO +• 4F* to n effect smmnr to cation, Ca . There, positive a^p. iaitialy' dimoriarion The repented with single. smaJfer than afa? ia LaF4J mixtures. Aa crystal U which. analyzed after the melting was based on the negative rontramrjon to l£afJ from shown to contain only 0.1 the increase in polarifalion (in coar^gurationt mole % oxide. The smel halts reported at 380 to 38S*C Ca^T") of the r by Ca** m the irmtively stroag in tbi original cAUMantnts were much weaker but stnt field of the F~ ions, which are mom munafous laCaF^ present in the later nrpnmvntt. Whether these baits than m UF.»* Appfted to li,8*F4-Li mixtures, F~ 2 2 may be attributed to a ternary eutectic with the though bound to Be * in BeF4 " are more remaining oxide impurity or to the stafomzatioo of for configurations U*1~F~ by a factor of 4 another form of Lai, perhaps tetrahedraly coordi- than in LaF-Li. This amy give the strong Mgaliw

,** winch undcrgofi a phase transition to the to positive excess free energy m UaBeF4-rich octahedral one at about 385*C is stii under

The LiaBeF4 hquidus is idea) initiaBy. that is. for n « 1 particle (I ~) per Lil. Positive deviation, excess partial 35. Cf. W. RiM.2: fky*k 143.599-403 (1955). ^&oJLJ) &*** ^ ^ \\\ ^&**$ \\*$

Part 3. Materials Development *

J. R. Weir, Jr.

TV area* of materials research and development surfaces of graphite with pyrorytic carbon is proving dhtuwrd in Ihn 3 inchide the postoperation examina­ difficult. We are increasing our effort in this area by tion of components from the MSRE, the development examination of the microstructural mechanisms of fail­ of radiation-fa* aant impenneable graphite, investiga­ ure of the sealant and are investigating other sealants tion of radsatiosi rlamwy and compatjbiity of Hastelloy such as barren salt. N in various environments, and materials work in The resistance of small heats of Hastelloy N modified support of the chemical processing equipment develop- with Ti, Nb, Zr, Si, and C to irradiation-induced embrittlement continues to be studied. We are utilizing One of the most mportant problems discovered by the microstructures to evaluate the type of carbide exaimirinc compones,*! from the MSRE is a shallow precipitate developed in the various compositions, since intergfaauter penetrant mto the Hastelloy N that there is a reasonably good correlation between the produces atergranubr cracking to a depth of several existence of MC-type carbides and good radiation mfls. Tins phenomenon <>ory occurs in metal exposed to resistance. Our compatibility programs involve deter­ the fuel salt, and it is of concern whether it is associated mining the corrosion resistance of Hastelloy N in fuel with a corrosion mechanism or the penetration of salt, the coolant salt (NafiF4-NaF), and steam. The certain embrittling fission products. Work is also con­ possibility of using a duplex tube of nickel on the tinuing on the fission product and corrosion product coolant-salt side and Incoloy 800 on the steam side of a deposition on graphite removed from the reactor. steam generator is being investigated. This combination The graphite program involves an assessment of the should produce the optimum corrosion resistance for resistance of commercial graphites to the dimensional both fluids. and structural instabilities produced by radiation The major effort in our work in support of chemical damage. Recent irradiation results indicate that graph­ processing equipment involves the development of ites can be fabricated at ORNL with behavior similar to fabrication procedures to build a complicated reductive the best commercial graphites. This result is encourag­ extraction processing unit of molybdenum. Procedures ing in that it increases our confidence that we under­ have been worked out for most of the components of stand enough about the radiation damage processes to the system. Other possible materials that appear to be further improve the important properties of the moder­ candidates for this application are tantalum and graph­ ator. Maintaining low permeability (during irradiation) ite. We are evaluating these materials and a few brazing to gaseous fission product intrusion by sealing the alloys for their resistance to bismuth corrosion.

88 11. Examination of MSRE Components

H. E. McCoy temperature1 had been exposed to fuel salt in the main circulating stream. Other pieces available to us that bad 1 As described in the last semiannual report, Hastelloy been exposed to fuel salt under somewhat different N components of the MSRE appeared superficially to conditions were rods and mist shield from the fuel have suffered very little corrosion, but when specimens sampler in the pump bowl and a section of the control of a control rod thimble and heat exchanger tubes were rod thimble that had been under a loose sleeve. tested in tension at room temperature, shallow cracks The mist shield was located in the pump bowl, and its appeared at surfaces that had been exposed to the fuel purpose was to keep salt spray from the region where salt. These cracks were intergranular, extending to a salt samples were being taken. The sampler cage is depth of roughly one to two grains, and did not occur located in the center of the spiral mist shield. The mist on the other sides of the specimen?, which had been shield is a spiral fabricated of %-in. sheet that has an exposed to air or coolant salt. It thus appeared that the inside diameter of about 2 in. and an outside diameter Hastelloy N exposed to the circulating fuel had been of about 3 in. The spiral was about 1% turns, and the attacked or embrittled along the grain boundaries by outside was exposed to agitated salt and the inside to some unknown mechanism. salt flowing at a much slower rate. The outside was As part of our efforts to resolve ihe effects of the fuel exposed to salt up to the normal liquid level ami co salt salt on Hastelloy N, we have proceeded to test pieces spray about this level. The inside was exposed to salt up from the fuel sampler and part of the control rod to the normal salt level and primarily to gas above this thimble that were exposed to fuel salt under different level. The general appearance of the mist shield was conditions. We have also tested pieces of Hasteiloy N described previously.2 that were exposed to fuel salt in in-pile loop 2 in 1967 Four specimens approximately 1 in. (vertical) X % in. and have reexamined surveillance specimens removed (circumferential) X % in. thick were cut from the mist from the MSRE core at various times during its shield. Their locations were (1) outside of spiral operation. immersed in salt, (2) outside of spiral exposed to salt Examination of a graphite moderator element was spray, (3) inside of spiral immersed in salt, and (4) extended to obtain more information on the elements inside of spiral exposed primarily to gas. Bend tests at or near the surface. were performed en these specimens at 2S°C using a three-point bend fixture.3 They were bent about a tine

11.1 EXAMINATION OF HASTELLOY N COMPONENTS EXPOSED TO FUEL SALT 1. B. McNabb and H. E. McCoy, MSR Propem Sammtnu. IN THE MSRE Prop. Rep. Feb. 28,1971, ORNL-4676, pp. 147,156. 2. E. L. Compere and E. G. Bohbnann, MSR Proyim B Mctfabb H. E. McCoy Semianm. Prop. Rep. Feb. 28,1971, ORNL4676, pp. 76-83. 3. H. E. McCoy and J. R. Weir, The Effect of Irmdittkm on The control rod thimble and heat exchanger tubes the Berui Transition Temperatures of Molybdenum- and Nio- that showed cracks under tensile strain at room biu Dose Alloys, ORNL-TM880, pp. 7-10 (July 1964). 90 parallel tc the % in. dimension and so that he outer Figure 11. la is a macrophotograph of bend specimen surface was in tension. The information obtained from S-52 from the inside top of the mist shield. The black such a test is a load-deflection curve. The equations scale has popped off most of the bend area, exposing normally u^ed to convert this to a stress-strain curve do shiny surface. A weld bead used to hold the spiral in a not take into account the p'astic deformation of the fixed position is visible on the lower right of tht pari. The stresses obtained by this method become picture. The specimen failed during the bend test, but progressively in error (too hign) as the deformation was the most ductile of the mist shield specimens. progresses. Figure ll.it> is a polished cross section of specimen The mist shield was made from %-in.thick sheet of S-52. The fracture and the small cracks on the tension Hastelloy N heat 5075 with 16.2% Mo, 6.7% Cr, 4% fe, side are evident. Higher magnification photo­ 0.44% Mn, 0.06% C, 0.58% Si, 0.27% V, 008% W, micrographs of sample S-52 are ihown in Fig. 11.2 for 0.02% Al, 0.02% li, 0.07% Co, 0.01% Cu, 0.003% P, the tension and compression sides. The cracks are about 0.006% S, and 0.001% B. The yield stress at room 1 mil deep on the tension side, and no ciacks formed on temperature was certified as 53.000 psi. ultimate tensile the compression sic Figure 11.3 is a macrophotograph strength 116,000 psi, and elongation 49% for the of the rensior side of specimen S-62 from the outside original material. Table 11.1 shows the results of bend top portion ol *he mist shield that was exposed to salt r tests on the specimens from the mist shield after sp ay. Several cracks are evident. removal from the pump bowl. Note that the yieid and Photographs of specimen S-60 from the inside liquid ultimate stresses are about twice as high as those region of the ir?ist shkiu are shown in Fig. 11.4. normally reported. These values can be used only for Extensive craclving is evidem in the macrophotograph comparison of the relative effect of the environment on (Fig. 11.4a). The polished cro&; section in Fig. 11.46 the properties. The unirradiated control test of \ in. shows numerous cracks to a depth of 5 to 7 mils. A sheet of a similar material (heat N3-5106) did not fail macrophotograph of specimen S-68 from the outside when subjected to the same bend test as the mist shield liquid region of the pump bowl is shown in Fig. 11.5. specimens, Indicating 'hat the mist shield specimens Numerous cracks are visible near the fracture. were embrittled somewhat even though all of them did One of the Vin.-diam sampler cage rods was tensile strain greater than 10% in the outer fibers before tested at room temperature to determine the change in failure. mechanical properties. The rod was made from Hastel-

Table 11.1. Svnd test* at 25°C on various MSRE components

Yield Maximum Specimen Strain stress tensik strew Environment number 41 (%) (pa ) (P$«)

x 10* X 103 S-52 Mist shield top inside 97 269 46.9C Vapor region sluelded S-62 Mist shield top outside 155 224 10.7° Vapor region salt spray S-60 Mist shield bottom inside 161 292 31.6' Liquid region shielded salt flow S-68 Mist shWHrt bottom outside 60 187 17.7C Liquid region flow rapid salt

N3-5196 Unifr-jtoted cw "iol 128 238 40.5 tirst, %m.th .

K^ 487 Unirradiated control 110 147 33.8 test, 0.065 in. thidc HVra-»a7 Control rod thimble under 88 134 33.6 Restarted sell flow OD spacer HT5060 Control: - i thimble spacer 79 105 ^3.8 Restricted salt flo* ID sleeve Fast salt flow OD

*B*ed on 0.002% in. offset of crosshead travel. "Maximum tensile stress was controlled by fracture of sampk or by strain limitation of test fixture. <:Speciry?n broke. 91

PHOTO 2632-?»

Fig. 11.1. Bend specimen S-52 from the vapor region inside of the mist shield, {a) Photograph showing fracture and tension side of specimen. Black scale has popped off exposing shiny surface in some areas. ~5.5X. (ft) Photomicrograph of half of bend specimem showing shallow cracks ui tea<«>n side of bend. The lower edge of the picture does not extend to the compression side of the specimen. loy N heat 5059 with 16.9% Mo, 6.62% Cr, 3.92% Fe, level, and cracks were not apparent at 5.5X magnifi­ 0.35% Mn, 0.07% C, 0.59% Si, 0.21% V, 0.07% Co, cation at th" top specimen grips. Figure 11.7 is a 0.01% Al, 0.01% Ti, 0.04% W, 0.001% P, and 0.003% S. photomicrograph of the edge near the fracture area, The room-temperature yield stress was certified as which was in the liquid zone, showing the extensive 51,200 prJ, the ultimate tensile stress as (15,300 psi, craclang. Figure 11.8 is a photomicrograph tf a section and the elongation as 51% for the original material. The from the vapor region about 1 in. above the rupture, yield stress of the sampler cage rod from the pump and the cracks are seen to be less deep than in the bowl was 42.450 psi, th: ultimate tensile stress 93,241 section below the liquid level. psi, and the elongation 35.7%. As seen in Fig. 11.6a, the The control rod thimble was a tube having dimensions rod ruptured below the center, probably near the of 7 in. OD X 0.065 in. wall thickness. To keep the average liquid-gas interface wn?re the deposits on the thimble centered in the graphite moderator, spacer rod appeared thickest. Numerous cracks cai» be sera sfceves were used periodically. They were joined to the near the rupture in Fig. 11.66, a greater enlargement, tithTible by weld beads on the thimble that were and individual grains appear to Iiave dropped out. The deposited through a clearance hole in the sleeve. Thus cracking occurred almost to the bottom of the rod, th? skeve was restrained in the vertical direction, but even extending into the area covered by the grips where was ftym to move some in the radial direction. The the stress would be much lower. The cracking dimin­ maximum and minimum clearances (according to shop ished toward the upper part of the vod above the liquid drawings) between the sleeve and the thhnble were 92

R-559e7

{a)

-55982

U>)

PfclU. <*) of ofiftekmft*2fcoa l*M4.Cnc**ptli -1 wM. 100X. (*) of Mif raptsm* As lOOx. 93

Fn> 113. MraopfeXognph of the sit* of S42tfcat takes iron the ovtside top portkNi of the i This area was exposed to fuel salt mist. 54x

0.015 and 0.000 in., respectively. The annular region rapture area of the spacer sleeve OD, which was would !

*NOTO 2«33- 71

Fig. AA. (tf) Iteaophocofnph of the tem'om tide of bead ipecmen S-60 from "matte aquid repoa of mist shield exposed to E*ud fad sah. ~5.5x. (6) Photonricrogtaph of bend and rupture area of S-60 showing extensive cracking on tension side of bend. The lower edge of the picture does not extend to the compression side of the specimen.

11.2 EXAMINATION OF COMPONENTS FROM Son* °* the components were made available for IN-P1LE LOOP 2 testing to deternunt if crackii.g would occur under stress as had been observed for some MSRE compo-

B.McNabb H.E. McCoy ^^ cxposcfj t0 fa} ^t M^ fission products. A Loop 2 was an in-reactor thermal convection loop ****** *riP approximately 1 X % X % in. thick constructed of Hastefioy N and containing fuel salt of was «* from *» toP of *« corc wsscl «** bcnd testcd 7 composition IiF-BeF2-ZrF4-UF4 (65.4-27.S-4.8-2.0 in the sane way as tte specimens from toe imst sliield. mole %).s It had a peak operating temperature of 720°C Tht «r«w« y»w *«** was 1O4'000 P»» *• ^^ and a minimum temperature of 545°C, and it operated tensiie **«* *» 225,000, ?nd the outer fiber strain 1102 hr with fuel salt at these conditions. Average was 41-5*- Fi*"* 1113 » a macrophotograph of the power densities of 150 w/cm3 of salt were attained, and t*1"1 «P*unen, showing that it did r.ot fail. This 8.2 X 101* fissions/cm3 were produced before oper- contrasts with the failure in a similar test of the mist ation was terminated by a leak. shield, which had been cxposeo for a much longer time to flowing salt and fission products. The peak operating .... , temperature for the loop was approximately 720/>C, 5. E. L. Compere, H. G Sera* and J. K. Bato, MSR md ««• bend sPccimcn came from near ** hottest Pronm Semiemu. fro*. Rep. Aug. it, 1967, ORNL-IJ91, p. "*»<*». **»»« 11.14 is a photomicrograph of the top 176. bend-tested specimen, showing the tension side of the 95

Fig. 113. Macroptaotograpli of the team* side bead S-68f roam the Exposed to agitated fuel salt. Extensive cracking is confined to the rupture

PHOTO 2454- f*

LIQUID VAPOR io)

%M£i

-. fffpi

Fjg. 11.6. (fl) Tensile-tested sampler cage rod from pans? bowt Rupture occurred near the average liquid-gas interface. ~1X. (*) Marrophotograph of rupture area showing extensive surface cracking in the liquid region. ~5.5x. Reduced 37%. 96

^

)

^ J

% .-

fig. 11.7. fhotowiuofiaph of edge «eu the fracture area of MSRE smpler cafe rod. Note extensive cracking and grain puilout at surface. The fracture occurred in a section of the rod that was near the average liquid level. 100X. As polished.

bend with snail cracks extending to a depth of about 113 OBSERVATIONS OF GRAIN BOUNDARY 0.5 mil. CRACKING IN THE MSRE A ring was cut from the cold leg return line, %-in. H.E. McCoy pipe (corresponding to the coldest part of the loop, 545°C), and cmshed in the bend rig. It appeared to The first indication that grain boundary cracking was have good strength and did not crack externally, as occurring in the Hastelloy N in the MSRE «/as obtained shown in Fig. 11.IS. No analysis of the bending data from surveillance specimens exposed in the core. When was attempted. Figure 11.16 shows microphotographs the third set was removed and examined in April 1968, of the cross section of the ring. The small cracks we first nork;ed intergranular cracking on specimens extending to a depth of about 1 mil covered the entire stressed in tension.6 Since that time we have examined interior surface. It appears that cracking did occur on more components and find that the cracking is quite the fuel-salt side of tl*J Hastelloy N loop material when it was stressed after exposure, even with its short 6. H. E. McCoy, An Evaluation of the Molten-Salt Reactor exposure time and low temperatures (545°C). However, Experiment Hastelloy N Surveillance Specimens - Third Group, tte mechanical properties were not greatly affected. ORNL-TM-26^7 (January 1970). fig. 11.8. Photomicrograph of edge in the vapor region of teaafcMested samplex cage rod. Cracking was not as severe in this area as ui the liquid region. Gly regis. 100X.

general in the fuel circuit.7 Photographs of samples that because it is likely the parameter that w itrols the were strained at room temperature will be used to diffusion of fission products inward and also is impor­ demonstrate the cracking, since grain boundary crack­ tant in moving chromium to the surface to resupply any ing is a normal process at elevated temperatures. Thus areas depleted by corrosion.) The unirradiated specimen cracks are also present in the samples tested at elevated was exposed to static fuel ^H containing depleted temperatures, but it is impossible to separate those uranium in a control facility, and the irradiated caused from exposure to the fuel salt and those due to specimen is from the core of the MSRE. There are more deformation. An even more careful analysis has shown that the cracks were visible in many of the samples when they were removed from the MSRE, and straining only opened the cracks to make them more visible. 7. MSR Program Senmannu. Prop. Rep. Feb. 28, 1971, ORNL~4676,pp. 1-20. Several photographs of tested surveillance specimens 8. H. £. McCoy, An Evaluation of the MottenSots factor have been shown previously,6,8-10 but several of the Experiment HasttUoy N Surveillance ."Tectmens - First Gtoup, specimens were repolished and photographed more OFNL-TM-1997 (No- -mber 1967). extensively after we realized the generalness of the 9. H. E. McCoy, Ati Enkmtkm of the Molten-Salt Reactor problem. Figure 11.17 shows polished sectkms of Experiment UesteBoy N SuneSBunce Specimens - Second Group, ORNL-TM-2359 (February 1969). Hastelloy N specimens tested at 25°C after heating at 10. H. F. McCoy, An Evaluation of the Molten Salt Reactor 650°C for 4800 hr. (The samples were exposed to fuel Experiment HasteUoy N Surveillance Specimens - Fourth salt most of this time. The time at temperature is used Group, ORNL-TM-3063 (March 1971). 98

Fjg, 11.9. Macropkotojrapli of MSRE control icd ftimfcte Fig. 11.11. Macrophotograph of tensile-tested ring from from under spacer deeve exposed to stagnant fuel salt on OD. spacer sleeve on control rod thimble. Exposed to rapidly Tensile tested at 25°C. 5.5X. flowing fuel salt on OD shown and stagnant fuel salt on the ID.

R- 56054

Fig. 11.10. Photomicrograph of control rod thia&le from under Exposed to stagnant fuel salt on OD (top) and *o cell air on the ID (bottom). As polished. 40x. 99

- 56040

Ffc. 11.12. Pboto—Hoyaph of traiaV laind ring from apacer steere on control rod Exposed to rapidiy flowing fuel salt on the OD (bottom) and to stagnant fuel ah on the ID (top)-As polished.

Table II J. Teniae data on controlrod databl e i iat25*Cata ofOjOSaWndn.

Specimen iNU stress Ultimate stress Material Condition number (ptl-) (pa) (%) (in.)

2 Y-8487 Irradiated 54.400 105,100 23.2 0.54 3 Y-8487 lmdutjd 53,300 102^00 29.7 0.51 4 Y-8487 Irradiated 60,500 110,800 28.5 0.42 6 Y-8487 Unbiadiat«r 52,000 114,400 44J 1.20 7 Y-8487 Unhradiated 56,900 117,500 46.0 117 8 Y-8487 Unirradiated 58,100 151,100 43.0 1.18 Under spacer Y-8487 Irradiated 60,800 116,000 32.9 0.45 Spacer aeeve Y-5060 Inadkted 80,900 155.200 110

*Bued on an offset of 0.002 in 100

R- 55716

F*. 1* 13. Msaoffcotoanpli of of be»d specimen from top of core read of in-pile loop 2, exposed to flowingfue l Specimen did not fuL 5SX. cracks in the irradiated specimen, but there are so few and numerous cracks formed on the fuel-salt side (shell that it is not surprising that we did not feel that they side), but not on the coolant-salt side (tube side) (Fig. were significant when first observed. 11.20). A close examination of the unstressed tubirg Similar photographs of samples removed after 22,533 showed that the cracks were visible. This is shown more hr at 650°C are shown in Fig. 11.18. By now the clearly in Fig. 11.21, a photomicrograph at higher frequency of cracking in the samples from the MSRE magnification. This component revealed that neither was quite high. These samples have an tilarged section irradiation nor straining were requirements for the at each md for pulling. Note that the cracks extend cracking, but that exposure tc the fuel s&It was along the radius even though the strain is decreasing necessary rapid?/ as the cross section increases. We have voUected the information thrt we presently A ring wis cut from the control rcsl thimble after it have on the depth and number of crocks formed in had been at tentpeiature for 26,000 hr and bad received various samples (Table 113). Several points seem a thermal fluence of about 2 X 10*' neutrons/cm4'..A important: portion of the stressed tube is shown in Fig. 11.19. The outside that was exposed *,o the fuel salt is heavily 2. The maximum depth of cracking did not »«m to cracked, but the crack Up* are generally quite bhint, increase systematically with exposure time over the indicating that they did not propagate as the tube was range 4800 to 26,000 hr. The d*pth seems to have strained. The other side of the tube wa~ oxidized by been limited to one grain dimeter. expcaure to the cell environment of Ni containing 2 to 2. The frequency of cracks increased dramatically with S% O*. The oxide cracked, but the cracks do not increasinc exposure time and reached different penetrate the tube wall. Thus this component was values in different components because the grain size haavtfy irradiated, but only the side exposed to fuel sah different. Several pieces of tubing were cut from the primary 3. The cracks were present when the material was •eat exchanntr and examissd One niece was strained removed from the MSRE, and they were made more 101

t-ilx

^V1

Fig. 11.14. PhotomiciOgranH of tension side of bend specimen from top of cote vessel of in-pike loop 2, exposed to feet salt. Maximum crack depth about 0.5 mil. As polished. 100X.

visible \>y straining the sample. They have blunt tips, concentration per unit area was computed by assuming indicating that they do not penetrate much as the that the fission products were distributed uniformly sample is strained. over the entire metal area of 7.9 X 10s cm1. The Layers were removed from several samples using measured concentrations were obtained by ownming methanol-10% HG as an electrolyte. These solutions the amounts found in successively removed layers. were analyzed by several methods and did indicate that Some samples inherently yielded better data because fission products had penetrated the metal. A typical set the surface being dissolved was better defined. The of results for a heat exchanger tube is shown in Fig. surveillance specimen and the heat exchanger tube were 11.22. However, it is difficult to attach much signifi­ good specimens, but the other samples had various cance to these results since the cracks extended to problems. For example, the samples from the control depths greater than our calculated sample depth (based rod thimble were small strips cut from a thin-walled on the amount of Ni). We were able to find all fission tube. The ed^es contributed appreciably to the nickel products with sufficient half-lives to still be present in content, but did not contribute to the fission product detectable amounts. Thus, these concentration profiles concentration. The depth of penetration was based on may not represent solid-state diffusion, but rather the the nickel content of the sohitkms, so die measured deposition of materials in existing grain boundary fhiion product concentrations are actuafly lower than cracks. those present on the single surface that was exposed to Compere compared the concentrations of several fuel salt. The fission products for which 10% or more of fission products found on the HasteOoy N surfaces with the inventory was found on the metal surface are shown the total inventory. The inventory values were com­ in Table 11.4. That is much scatter in the data, and puted taking accovnt of the power history, and the there does not seem to be any systematic variation of a 102

-55745

Fig. 1 !.15. Macrophotograph of cok! leg return line of in-pile loop 2 exposed to flowing fuel salt on ID. The ring was crushed in a bend test at 25°C. Sj-ecimen did not fail. ~5.5X.

PHOTO 2453-7«

Fig. 11.16. Photc rJcrographs of cross section of crashed ring from cold leg of inpik loop 2, exposed to flowing fuel salt at 545°C. On ID maximum crack depth ~1 mil. As oolished. iOOx. Reduced 56.5%. 103

R - 55i«G t

Fig. 11.1". Photomicrographs of Hasteiloy N tested at 25°C after 4800 hi at 650°C. The top specimen was in static fuel salt containing depleted U. and the lower specimen was in the core of the MSRE. The true specimen diameters are 0.070 to 0.090 in.

particular fission product as one progresses around the melting points and would reduce the melting point of primary circuit. However, significant tractions of the the Hasteiloy N. Several of these elements (namely, Te, elements shown in Table 4.4 were found on tta metal Sb, and S) aie also known to embrittle pure nickel,1' surfaces. and Te has been shown to embrittle a Ni-Cr-Co-Mo We noted that oxide fih.is interfered with the alloy.12 Thus penetration of these elements along the dissolution process. To concentrate the materials that boundaries could produce a localized region with a were present along the grain boundaries, we pieoxidized lower melting point and low ductility. To open the a surveillance s?mole in air at 650°C, < trained it about boundary up as a crack during service would require half way to fraau. , and dissolved successive layers. We that this region become completely molten or that a found that Te, Ce, Sb, Cs, Sr, and S were higher than noted previously for samples not oxidized. Two general mechanisms seem possible based on these observations. First, the fission products (or S from the 11. C. G. Bieber and R. F. Decker, "The Melting of Malleable salt and the pump oil) could be diffusing along the grain Nickel and Nickel Alloys," Trans. AIME 221,629 (1961). 12. D. R. Wood and R. M. Cook, "Effects of Trace Contents boundaries. All of the elements mentioned above that of impurity Elements on the Creep-Rupture Properties of were concentrated along the grain boundaries have low Nickel-Base AHoys," MetaUurgia 109 (March 1963). 104

SURVEILLANCE - FOURTH GROUP

Fig. 11.18. Photomicrographs of HasteDoy N tested at 25°C after 22,533 hr at 650JC. The top specimen was in static fuel salt containing depleted U, -n-J the lower specimen was in the core of the MSRE. The true specimen diameters are 0.07C to 0.090 in.

Fig. 11.19. Photomicrograph of ring from control rod thimble that was tesUMi to failure at 25°C. The top surface vas exposed to

fuel salt, and the bottom surface was exposed to the cell atmosphere of N2 conte ning 2 to 5% 02- Part was at 650°C for ?6,000 ru­ in a h|gh radiation field. The wal thickness -z abou' 0.065 in. 105

I -5517a

UN51tESSH>

SIU5SH>

Fig. 1120. Photomicrograplis of tubing from the primary heat exchanger. It was at 650°C for 26,000 hr. The lower specimen was strained to failure at 25 °C. The original wall thickness was 0.042 in Fuel salt was on the upper side of each tube, and coolint salt was on the lower side.

R-55203

Fig. Mil. Photoirjcrograph of a tube from the MSRE primary heat exchanger. Tie up,*r surface was exposed to ccolant salt and the lower surface to fuel salt. 106

Table 11.3. Crack formation in HasteUoy strained to failure at 25°C

Time of Sample description exposure Cracks Depth (mils) (hr) Counted Pet inch Average Maximum

Surveillance, heat 5085 4,800 24 19 2.5 8.8 Control I 1 5.7 5.7 Surveillan.-e, h??t 5085 15,300 178 i34 1.9 6.3 Contrci 0 Surveillance, heat 5085 22,500 213 176 5.0 7.0* Surveillance, heat 5085 14C 146 3.8 8.8 Surveillance, heat 5063 240 229 5.0 7.5 Control, heat 5085 4 3 L> 2.8 Thimble 26,000 91 192 5.0 = .0 Heat exchanger (stressed) 26,000 219 262 3.0 6.. (unstressed) 100 228 2.5 3.8 (unstressed) 135 308

cOne crack was 15 mils deep; the next largest was 7 miis.

stress be imposed. The first possibility seems unlikely, make it usable in Bi systems. The specimen was and the design conditions of the items thai we suspended in salt at 650°C, some MoF* was injected as examined required that they either be unstressed a gas, the melt held at temperature for 48 hr, and the (surveillance specimens) or under compression (thimble, sal! discharged. The top layer is quite high in Mo, the heat exchanger tube). Another mechanism is one of intermediate layer contains salt and some metallic selective corrosion. The accepted cor/osion mechanism elements, and the substrate is type 316 stainless steel. for the fuel salt and Hastelloy N is the selective removal The grain boundary attack is quite evident. of Cr by the reaction We cannot presently distinguish between the various mechanisms that have been proposed. However, numer­

UF4 + Cr (in alloy) * UF3 + CrF2 (in salt). ous experiments are in progress to dzhtt and learn how to control the process. Much of our experimental corrosion work was done at higher temperatures, am! all of it was done in systems 11.4 EXAMINATION OF A GRAPHITE MODERATOR ELEMENT where the concentrations of UF3 and UF4 were uncontrolled and not known accurately. Thus, although B.McNabb H.E. McCoy we did not observe selective grain boundary attack in our tests, the possibility of its occurring cannot be ruled The graphite moderator element removed from the out. In fact, the grain boundaries are generally more MSRE after shutdown appeared unchanged by the reactive in metals, and selective attack would be irradiation or fuel-salt flow, as reported earlier.13 expected under «ome conditions. When the concen­ Core-drilled samples were taken from the fuel channel tration of UF3 was high no corrosion would occur, and of this element for Auger and spectrographic analyses; when it was low all elements would be removed. At the Auger analysis of the surface layer is. reported in the seme intermediate concentration selective removal next section. Small samples (% in. diitm) from about along the grain boundaries could occur. the midpiane of the core were used as electrodes for the An example of selective grain boundary attack of type 316 stainless steel in LiF-BeF2 is shown in Fig. 11.23. This experiment was run to determine whether a 13. B. McNabb and H. E. McCoy, HSR Program Semiamu. Mo coating could be produced on stainless steel to Ptoy. Rep. Feb. 28,1971, ORNL-4676, pp. 139-43. 107

ORNL-DWG 71-7106 mass spectrograph analysis of lission products. T ible HEAT EXCHANGER TIBE 11.5 shows the resuks of successive analyses, using increasing amounts of current. These data are quite 1 2 3 useful, but several factors limit their accuracy. The O penetration cf the spark into the graphite was likely a K) hemisphere, so some new surface continued to be included as the penetration depth increased. The calculated depths are estimates of the maximum depths -1 sampled. The sensitivity of the analysis increases with 10 increasing current. The size of the area sampled is also of concern, particularly at the lower penetration depths. This graphite has pores about 0,1 JJ (1000 A) in rZ 10 diameter, and the compositions of the first samples (taken from areas a few angstroms in diameter) could be quite dependent upon the location. These factors r3 make it impossible to obtain a quantitative concen­ 10 tration profile, but it appears that the fission products are concentrated at the surface and decrease rapidly with depth. r4 ?• 10 US AUGER ANALYSIS OF THE SURFACE LAYER ON GRAPHITE REMOVED FROM r5 THE CORE OF THE MSRE 10 R. E. Clausing Quantitative analysis of thin layers of fission products r6 10 deposited on the graphite and metal surfaces of the MSRE would provide information valuable for pre­ dictions of the requirements for afterheat removal in -7 fuiiire molten-salt reactors. Auger election spectros­ 10 copy offers unique capabilities for such analyses. The construction of equipment for this purpose was de­ scribed previously.14 The equipment has beea modified 10r 8 to permit ten samples and *candards to be loaded for examination at the same time, thus facilitating the comparison of samples with other samples or standards. -9 The measurements and analysis of data have been 10 delayed partially because of unexpected problems w?th the multiple sample system and partially because of the complexity of the spectra. HO 10 The measurements on four samples from the graphite moderator ebmec*. 11844% 19 removed from the MSRE 12 3 4 after shutdown are partially complete. They give spectra qualitatively similar to that reported previously DEPTH (mils)

Fif. 11.22. Concentration profiles from the fuel side of an MSRE heat exchanger tube measured about 1.5 yi after reactor 14. MSR Program Semknmu Prop. Rep. Feb. 28, 1971. shutdown. ORNL-4676, pp. 143-45. 108

Table 1 i.4. Concentrations of several fission products on the surfaces of HasteUoy N compared with the total inventory

Depth of Concentration of nuclide compared with invent My Systole location penetration 127 I34 12S ,03 ,06 95 y (mils) Te Cs Sb Ru Ru Nb * Tc

Control rod thimble (bottom) 2.4 0.43 084 0.85 0.40 0.13 0.37 0.32 Control rod thimbie (middle) 0.1 0.14 0.24 0.35 0.15 O.il 0.26 0.19 Surveillance specimen 3.5 0.001 0.35 1.04 0.006 0.087 0.006 0.30 Mist shield ouishie, liquid 60 0.23 0.035 0.74 0.069 o.io 0.067 0.19 Heat exchanger shell 4.2 0.35 0.017 0.68 0.027 0.05 0.085 0.27 Heat ex Hangtt tube 4.3 0.67 0.006 1.13 0.028 0.14 0.070 0.31

Table 11.5. Concentration in weight percent of the elements on the surface of MSRE graphite stringer at the reactor midplane

Maximum penetration depth (A) Mass Element -2.5 -25 800 900 2000 3000 4000

Fission products detected 87 Rb 0.0018 89 Y 0.0044 90 Sr 0.0067 Natural Mo 0.87 0.58 0.20 0.03 0.02 0.11 0.07 Fission Mo 3.6 2.4 0.59 0.09 0.26 0.30 0.24 93 Nb 0.003 0.002 0.001 99 Tr 0.57 0.39 0.09 0.02 0.05 0.05 0.04 101,102,106 Ru 1.4 0.95 0.19 0.04 0.11 0.09 0.09 103 Rh 0.34 0.22 0.055 0.01 0.03 0.02 C.02 110 Pd 0.11 0.053 0.01 0.02 0.015 0.01 109 Ag 0.0073 0.003 114 Cd 0.0046 0.015 0.007 125 Sb 0.01 0.0057 0.005 0.004 130 Te 0.41 0.30 0.046 0.009 0.02 0.02 0.01 133 La 0.004 0.006 0.003 0.002 138 Ba 0.005 140 Ce 0.007 0.01 0.006 0.005 141 Pr 0.003 0.003 0.003 144 Nd 0.01 0.01 0.006 147 Pm 0.0008 Nonfiaaon dementi detected Ni 0.9 Fc 0.3 Cr 0.05 Mn 0.005 109

Y-1C1661

F~

X o

o8

Fjg. 11.23. Type 316 stankst steel exposed to UF-BeF? contsiairg MoF6 for 48 hr it 650 C

for MSRE sample 6 (ref. 15) but differing considerably drum, and molybdenum are all present in large per­ in detail. For example, on one sample, MSRE 7, the centages (>5%) and niobium in a smaller but detectable amounts of rhodium and technetium are at least twice amount. The analysis of ruthenium is difficult because that on MSRE 6. (Rhcuium was found to be present on of interference from the carbon peaks and other fission MSRE 6 but had not been identified in the previous products, but there is reason to suspect tbat it may abo report.) be present in relatively large amounts in that the carbon Table 11.6 shows some sputter profile data from peak shapes are somewhat distorted. A similar situation MSRE 7. Tito sample came from the center of the flow exist, for tellurium, whose primary peaks fall at the channel near the reactor midplane. The concentration same energies as the secondary oxygen peaks. Although of fission products is only given in units relative to ihe not included in the table for this reason, it appears that carbon. The determination of the actual concentrations significant amounts of tellurium are abo present. The of various elements present must await comparison with large oxygen and nitrogen peaks may indicate that a standards. It appears, howev.T, that technetium, rho- large portion of the fission products is present as oxides and nitrides. Small amounts of iron and nickel have been detected on MSRE sample 13, which b from 15. Ibid., pp. 145-47. another part of the same moderator dement. 110

Table 11.6. Auger election intensity as a function of depth below the original surface of sample MSFE 7 from a MSRE moderator element

Accumulated Technetium, Technetium, argon ion sulfur, Niobium Rhodium Nitrogen Oxyjcn molybdenum bombardment molybdenum (200 eV) (300 eV) (383 eV) (510 eV) 1 (182 eV)

(x lO^/cm ) ifi f (148 eV)

75 15 19 40 nd* 9 i2 25 75 15 na* 35 nd 8 14 na 116 23 16 55 2 7 il 23 150 30 26 50 nd 11 17 26 225 45 13 55 2 7 8 18 525 105 15 5 nd nd 2 9 1160 230 13 2 1 nd 4 9 2325 485 5 7 2 nd nd 3 4725 945 3 8 2 nd 1 3

"nd = not detected, na = not analyzed. 12. Graphite Studies

W.P.Eatherly

The purpose of the graphite stud'.^s is to develop for sealing graphite against fission product gases. A improved graphites suitable for use in molten-salt considerable portion of the present progiess report reactors. The graphite in these reactors will be exposed centers accordingly on improved or alternative process­ to high neutron fluences and must maintain reasonable ing techniques and evaluation of the microstructure on dimensional stability and mechanical integrity. Further, previously irradiated specimens. The previous materials the graphite must have a fine pore texture that will were fabricated in fluid bed furnaces, a technique exclude not only the molten salt but also gaseous involving complex gas reaction kinetics and limiting in fission products, notably '3 5 Xe. the size specimens that could be coated or impregnated The genera] irradiation of commercial graphites and with pyrolytic carbon. For these reasons a new furnace experimental samples obtained from the Y-12 Develop­ was constructed utilizing a fixed substrate, and initial ment Division has spanned a broad range of raw coating and impregnation runs are now under way. materials and fabrication techniques. It has been found Additionally, a second look is being taken at im­ that these materials could be divided on the basis of pregnation with frozen salt as a means of pore blockage. their geometric b«ehavior under irradiation damage into Although there is reason to question whether the four classes: conventional, apparently binderless, hot- desired diffusion rates and irradiation stability can be worked, and black-based graphites. At the present time obtained, die technique is so simple in application to it appears that only the binderless and black-based justify at least a cursory exploration. materials offer the opportunity of significant improve­ During this reporting period the apparatus to measure ment. Our own fabrication studies have therefore been thermal conductivities of HFIR-irradiated samples was based on these two approaches. The first ORNL- completed and the first irradiation performed. A fabricated "binderless" graphites have now been irradi­ thermal expansion apparatus which will permit accurate ated to 1 X 10" neutrons/cm3 (E > 50 keV)inthe determination of the linear expansion coefficient as a HFIR and are stable to this level. These results are most function of temperature is almost completely con­ encouraging in supporting our general concepts as to structed. This information is desired not only for the microscopic physical phenomena controlling dam­ engineering purposes but also because of its close age. alliance to damage. In view of the initial successes of the graphite Progress cortinues on the theoretical interpretation of fabrication studies, we have recently decided to reduce damage clusters as seen in the electron microscope. The effort in this area pending further irradiation results. strain field calculation has been completed for intersti­ This permits an increased effort on various techniques tial aggregates, and diffraction effects for crystal di- 11 111 > 112

rections have been completed. At least qualitatively the 0RNL-3VG 71-6910 calculations are in excellent agreement with observed effects.

12.1 THE IRRADIATION BEHAVIOR OF GRAPHITE AT 7I5°C C. R. Kennedy W. P. Eatherly We have extensively studied the neutron irradiation behavior of graphite at 715°C, primarily to determine the incremental or decremental changes in life ex­ pectancy resulting from a wide variety of starting materials and fabrication methods. Over 40 experi­ mental and commercial grades of graphite were irradi­ ated in the HFIR to fluence levels up to 4 X 1022 neutrons/cm2 (>50 keV), invariably producing signifi­ cant volume expansions. The changes in 'inear di­ mensions and bulk density were the prime measures in evaluating the materials. The irradiation behavior of the graphites demon­ strated that all of the various grades could be separated K) 20 ("K)2') into tour bask types of mat ials: FLUENCE (nwtrom/cn£/Mc) 1. Conventional graphites. These graphites all consist of materials made from calcined coke or graphite flour Ffc 12.1. Volume of c*roeatfc>atJ graphites, 7 t5°C. as filler bonded with either thermoplastic or thermo­ setting hydrocarbons. The genera', irradiation behavior is characterized by an immediate densification followed Conventitr", aphites all have virtually the same by • parabolic expansion, as shown in Fig. 12.1. The lifetime expect- cy with no apparent effect of molding, isotropic mate ri Us have a lower tendency for densifi­ extrusion, type of filler, Theruax additions, type of cation than the iinisotropic graphites made with acicular binder, or the type of impregnant. The choice of cokes, and both demonstrate that the maximum densifi­ graphites within this category would depend uoon the cation varies inversely with the original density. A necessity of isotropy and other properties, such as considerable degree of anioctropy in the densification thermal conductivity, mechanical properties, and coeffi­ process apoears to depend on both the method of cient of thermal expansion. fabrication and the crystalline structure of the filler particles, which usually is reflected in their morphol­ 2. Apparently binderiess graphite?. The raw materials ogy. The more isotropic graphites always densified and the fabrication procedures for most of these more in the extrusion direction for extruded grades and graphites are proprietary. They are characterized by an normal to the forming force for the molded grades. apparency binderiess single-phase microstructure with a fairly fir.? optical domain size. These graphites are all The linear dimensional changes depended upon the very isotropic, have a high coefficient of thermal anisotropy of the graphite, the crystallite size, and the expansion, and generally have a lower crystallite size density changes. The growth rates at fiuences where the than the conventional materials. density change was constant agreed with the Reuss 1 Their irradiation behavior shown vi Fig. 12.2 is one-dimensional constant stress model. The affect of characterized by a delay Or ait elimination of the crystallite size on the growth tate was in excellent 2 densification process, yielding a more dimensionally agreement with that found by Bokros. stable graphite with about twice the lifetime of the conventional graphites. The linear dimensional changes are isotropic, reflecting only the bulk density changes. t. A. Reuss, Z. Angew. Math. Mech. 9,49, (1929). Thus, the individual crystallite growth rates cannot be 2. J. C. Bokros, C. 1. Guthrie, and A. S. Schwartz, Carbon 6, calculated directly from extrapolated orientation de- 55 (1968). -\dence. 113

ORNL-0W6 71-6915 ORNL-MG 71-6909

K) 20 90 WO21) — FLUENCE (Mirtro«JiA*N2/«tc)

Fh> 12.2. The of tppocKdy

3. Hot-worked and mesophase graphites. These graphites by virtue of hot working are highly aniso­ tropic. Although the original densities may not be very K> 20 MIO*) high, the void structure for densifkatioa has apparently 2 P-UEHCE (neutrons/cm /»c) been dimidiated by the hot working. None of these materials densified under irradiation, as shown in Fig. Faj. 123. behavior of hot-wodaed 123. The volume remained constant for a short period 715°C and then began to expand parabolically with fluence. The life expectancy of these grades is similar to that of the conventional grades; however, the linear di­ mensional changes are quite large due to the anisotropy evidence that the densification is binder-dependent as and would not be acceptable for most designs. The well. These materials are all isotropic, and the linear, linear dimensional behavior, excluding density changes, dimensional changes are again a result only of bulk can be represented by the Reuss model. density changes. The lifetime expectancy of these 4. Carbon-black grades. These are grad-s in which all materials is equal to or greater than that of the the filler is a carbon black. They are characterized by a apparently binderless grades, such as represented by structure of randomly oriented, ultrafine optical do­ Poco-AXF in Fig. 12.4. mains with no anisotropy and a fairly small crystallite It appears, therefore, that graphite with improved size. The coefficient of thermal expansion is generally lifetimes may be developed from either the apparently large, the thermal conductivity is low, and the mechani­ binderless graphites, carbon-black grades, or from com­ cal properties are fairly good for the generally low binations of the two. The disadvantage of the low bulk density. The densification due to irradiation is thermal conductivity of the carbon-black grades can be quite rapid, as shown in Fig. 12.4, possibly reflecting moderated by combinations of green coke and carbon- high negative crystalline growth rates. The expansion black filler materials. Also, as discussed in an earlier after densification, unlike that for all o'her materials, is report,3 the addition of carbon blacks to green filler linear with fluence and seems to be independent of grade and heat treatment. The initial increase in 3. C. R. Kennedy md W. P. Eatherly, MSR Program density, however, depends upon final heat trer-ment Semiannu. Progr. Rep. Feb. 28, 1971, ORNL-4676, pp. temperature, as shown in Fig. 12.5, and there is some 169-70. 114

22 2 1 OML-(MR 7l-tS« finances of 1 X 10 neutrons cm" sec" , as seen in F.g. 12.6, indicated that the behavior is quite similar to the apparently binderless grades exhibiting very small isotropic expansion. There appears to be no immediate influence of the binder or the addition of up to 40% Thermax »o the filler material. 8

OHHv-DWG 71-12641 S

uw") -1

£-2 '"Ac ^A, Fjg. 12.4. The effect of irradiation on varioas carbon Mack 129 ALL ROBINSON COKE-15V 9M0ER grades aid "• Poco-AXF at 715°C. 3-31 116 60% ROBINSON COKE. 40% THCRMAX-tSV BiNOER 157 60% ROBINSON COKE. *0% THERMAX-350 BINDER

-5 _J_ _L. 6 8 10 12 14 16 18 20 22 UK?) 0ML-OKT1-«9IS

F«. 12.6. The resalts of the lost irradiation of ORNL 715°C.

12.2 PROCUREMENT OF VARIOUS GRADES OF CARBON AND GRAPHITE W.H.Cook W.P.Eatherly

The various grades of carbon and graphite that we have received since January 1,1971, are summarized in 10 20 30 blO™) FLUCNCE inm*mn*/cm2/**) Table 12.1. One grade, A676, has an apparent density of 1.87 g/cm3, but the remainder have apparent r F|g. I" . The effect of final heat treatment on the dimen­ densities from 1.79 to 1.47 g/cm3. On this basis, they sional stability of a carbon-black grade irradiated at 715°C. are not outstanding; however, they generally represent some special parameters). The first tour grades listed in Table 12.1 represent studies primarily on isotropic fillers bonded with produces a graphite with a more contiguous structure. synthesized, experimental binders of acenaphthylene We are presently investigating these types of raw and isotruxene. material systems and are now irradiating grades with The graphite-fiber-reinforced-grade PTE is not ex­ representative structures for evaluation. pected to have any potential as a moderator material, Three ORNL materials have received their first but it may be useful as a high-temperature structural irradiation. These were all made using green Robinson material in regions of low flux. coke as the filler with and without Thermax additions, Grade A680 is the low-fired lampblack-base material and with coal-tar pitches 1SV and 350 as binders. The that we had requested to replenish our supply of this densities were reasonable; however, the structures con­ materia] to continue our studies previously reported.4 tained a fine network of lamellar voids normal to the molding direction. This structural fault has been elimi­ 4. O. B. Cavin, W. H. Cook, and J. L. Griffith, MSR Program nated in newer moldings. The results to maximum Semiannu. Progr.Rep. Feb. 28,1971, ORNL-4676, p. 171. Table 12.1. A summary of the various types of carbon and graphite samples received since January 1,1971

Max. Total Apparent No. of Fabrication firing Dimensions Grade weight Manufacturer Filler Binder Impregnant density Remarks pieces method temp. (g/cm*) (in.) (g) (°C)

675-U-4 4 Extruded Low-fired ACN- Butadiene Had radial cracks Santa Maria ITX* gas method 676-01-4 4 Extruded Low-fired ACN- Butadiene Had radial cracks 0.128 ID X Poco, PCD-OQ ITX gas method fMEDD" 0 2800 0.400 OD X 118 6 Molded Low-fired 0.500 Lot No. 1 of filler Poco, PCDOQ ITX* 132 6 Molded0 Low-fired Lot No. 3 of filler Poco, PCS-OQ ITX PTE 588 CPDd Pitch* 1.62 5.9 diam X 0.76 thick Graphite fiber reinforced A680 1 1,358" 0.86 X 5.66 X 11.58 Q322 1 1,394 ^-Stackpolef Carbon black Pitch' 7.4 diam X 1.4 thick A676 1 1.0X4.8X 7.9 in JA-5 1 17/ X 3%X4'/ Preliminary Airco Speer* Grade JM-15 e I6 a 1 Cracked lVl6X 3%X8%

! R18 3 5% diam X ~5 /4lor,g R20 1 Calcined 5% diam X -5% long Molded Robinson Pitch* Pitch* 2700 R22 I Coke' 5%diamx~5V, long R24 3 5% diam X ~5% long

aMateriah Engineering Development Department of the Y-12 Plant, Oak Ridge, Tennessee. *ACN - Acenaphthylene and ITX »isotruxene. folded at 1400°C and 1600 psi. <*Parma Technical Center, Carbon Products Division of the Union Carbide Corporation, Parma, Ohio. 'Not available or additional details not available. Sstackpcto Carbon Company, St. Marys, Pennsylvania. *Airc o Speer Carbon Products, St. Marys, Pennsylvania. *Great Lakes Research Corporation, Ehzabethton, Tennessee. 'Made from the Robinson Raw Coke manufactured by the Carbon Products Division of Union Carbide Corporation, Lawrenceburg, Tennessee, under AEC Contract AT(29-2)-1955. /Da^a supplied by the manufactuinr. 116

Grade Q322 is similar to the previously described interest. We continue to determine these parameters on graphitized lampblack grade A67I. Grade Q322 is a newly fabricated oodies made at both ORNL and the short section from a 7%-in.-diam cylinder and was Y-12 installations, as well as poteniai new grades that offered as physical evidence that base stock sizes as are received from the manufactures. required by the MSBE can be fabricated using a Three samples of mesophase grcphite were received lampblack filler. for evaluation. The x-ray-detei mined crystalline pre­ Grade A676 is grade A68I, the graphitized lamp- ferred orientation parameters are shown ir. Table 12.2. bUck-base body we have been studying, that has been It was thought that the mesophase bodies should be impregnated to change the nominal apparent densities nearly isotropic; however, this is not the case from 1.60 to 1.87 g/cm3. The ACF-4Q is a low-fired Poco grade that has not The grade JA-5 is in the early stages of development been above 1400°C and is the starting material for the and uses an isotropic to near-isotropic filler designated AXF grade. Three sphere samples were cut with their a? grade JM-iS. axes mutually perpendicular, and the results are shown The series of grades R18, R20, and R24 represents in Table 12.2. The sum of the three independently

the start of a study with varying amounts of pitch determined /?( values is 1.907, which is very near the binder with an isotropic filler made from calcined theoretical value of 2.0. This iiaterial >> very isotropic. Robinson (air-blown) raw coke. The latter is a product A block of grade JA-S graphite was received from from a sizable production (24 tons) from a pilot-scale Airco Speer Carbon Products for property evaluation. coker. Three sphere-type samples for anistropy determinations Arrangements have been essentially completed to were cut from this block with their axes mutually obtain specimens of carbon materials from Poco Graph­ perpendicular. From these three samples we then ite, Inc., spanning the temperature range 1400 to 25O0°C. The low-fired materials would be grade AXF precursor fired to 1400, 1800, 2000, 2200, and 2500°C. We plan to extend the temperature range to TaMeI2-2. X-ray HMOtropy pit mm trn 3000°C by refiring a Poco-supplied stock piece (fired to 25O0°C) to 3000°C and machining specimens from Sample number V RJ BAF it. Since these specimens represent material at inter­ mediate stages of a production process, certain agree­ H413 0'40 0480 1.126 ments are being arranged to protect their proprietary H-414 0.643 0478 1.109 H-415 0.636 0482 1.145 position. ACF-4Q No. 22 0.665 0467 1.014 The purpose of the experiment is to take the most ACF4QNo.42 0.667 0466 1.014 stable graphite known to us and examine the effect of ACF-4Q No. 72 0.665 0468 1.014 heat treatment on its behavior. Both the plasticity and JA-5.S-1 0.663 0468 1.016 crystalline size are sharp functions of heat treatment JA-5,S-2 0.668 0466 1.012 JA-5.S-3 0.670 0.C65 1.031 temperatures, and both are believed to be important in M-5.Y-12 0.659 O.o70 1.034 determining the lifetime of graphite under irradiation. 2020A 0.681 0459 1.135 The resulting data, aside from their intrinsic interest, 2020B 0.634 0483 1.155 will also afford a qualitative check of our proposed 2020C 0.674 0463 1.067 radiation damage model. HS-82 No. 26 0.668 0466 1.012 HS-82No.66 0463 0469 1X117 We have received a graphite flour, grade 1074 (~23.0 HS-82 No. 76 0478 0461 1.106 kg), from the Great Lakes Carbon Corporation. This 226A 0.662 0469 1X121 material is slightly anisotropic. It is being evaluated for 1226B 0466 0467 1.006 use in both the Molten-Salt Reactor and High- 1226C 0455 0473 1X184 2044A 0458 0471 1.082 Temperature Gas-Cooled Reactor Programs. 2044B 0443 0479 1.248 2044C 0481 0460 1X167 123 X-RAY STUDIES HS-17A1 0456 0472 1.049 HS-17A2 0476 0462 1.086 O. B. Cavin HS-17B 0496 0452 1.289 HS-17C 0.684 0458 1.165 Isotropic polycrystalline graphites continue to be the

most irradiation stable; therefore, the x-ray-determined "Rt refers to ti»* sphere stem axis. tsotropy parameters on new materials continue to be of ^tLi'l-R^l. 117 determined independently the anisotropy value in each ONM.-MB 74-9971 , ! , , j , of the three directions. A sample of the same grade but AXF-50 a different Mock was submitted by L. G. Overholser of Y-l 2. The results obtained from these samples are listed in Table 12.2. The anisotropy values indicate that the material was fabricated by molding and that the axis of sample S-l is parallel with the fabrication axis. The axis of Overholser's sample was also parallel with the fabrication axis but had a greater degree of anisotropy. This indicates either a nonuniformity in the graphite or it came from a position in the block near the end where die effects, if any, would be greatest. There was some question as to the maximum temperature to which JA-5 had been; therefore, all four samples were fired at 2800°C for 1 hr. The anisotropy values obtained from the fired simples are within expeiuncsfal en or of mose in Table n.2. Each of the other grades of graphite reported in Table as" 1 1 1 1 1 1 1 300 400 500 GOO 700 800 900 WOC 12.2 has been around for some time, but anisotropy TOVCMJURC (K) values had not been determined. These samples with axes mutually perpendicular were used to determine die Fig. 12.7. The thenrel n iHiiMj (X-1) of MB anisoiropy values independently in the three directions. One of the samples of HS-17A had a high density, and tomptwtimai heat-flow ^pwrifri. Coopantne heat-flow nrcments on other H-337 suapfcs are shown. so a sphere was machined on each end of a l-in.-kmg sample. The sample marked A2 was the sphere having the higher density and has a much different jnisotropy value than the Al sample. Tim ?pparerdy came from 2pfjaratus,s and the two approaches agree to ±0.2% in near the surface where impregnation effects would be the temperature range of overlap.' most pronounced. Measurement* of X and p were performed on unirra- dialed AXF-5Q and H-337 graphite to 1000°K in this The sum of the three independently determined R§ values for each grade is very near the theoretical value apparatus. The p *ad X values decrease with increasing of 2.0, but there is some variation due to the temperature. Figure 12.7 indicates a linear dependence 1 inhomogeneities of the graphite. of X" on temperature above 500°K for these graphites. We are also studying the effects of firing different Three smpfes of each of these graphites were graphites and filler particles to successively higher irradiated in HFIR for two cycles at 550, 650, and temperatures. These will be reported in the near future. 750°C. These samples are ready for remeasurement of X and p fromroo m temperature to just be'ow die relevant irradiation temperatures. 12.4 THERMAL PROPERTY TESTING Assembly is 75% complete on a 1200°K quartz dflatometer to ueasure the temperature dependence of J. P. Moore D. I McElroy T. G. Kolhe the temperature coefficient of thermal expansion of A guarded longitudinal heat-flow technique for these graphites and the influence of irradiation oa mis measuring thermal conductivity X, electrical resistivity property. The apparatus h being interfaced with a p, and thermopower S on smaii (1X7 cm) rods from computer-operated data-acquisition system to control 300 to 1000°K was tested with an Armco iron the experiment and to obtain the length, temperature, standard. An error analysis indicate? a most probable and electrical resistivity of the specimen. determinate uncertainty in X of ± 1.6%. The X results on the standard agree with the assumed values to tins uncertainty, except at 970°K where a 1 or 3% 5. M. J. Laabitz rrf D. L. Mcfiroy, Atftvfagfc 7, 1-15 difference is noted depending on the method of (1971). 6. I. P. Moore mi D. L. McBtov, Piniwwnanji XI ttrtw- calculation. The X of the standard was verified from 80 natiooal Conference oa Thermal CcaiactMtv, Atoamaae, to 400°K in a low-temperature guarded longitudinal New Mexico, September 2S-October 1,1971. 118

12.5 HELIUM PERMEABILITY MEASUREMENTS density values have been included for comparison ON VARIOUS GRADES OF GRAPHITE purposes. These grades of graphite are being studied for their unique starting materials and/or fabrication tech­ W. H. Cook J. L. Griffith niques used. The permeability deteiminations are part Table 12.3 is a summary of the permeability coeffi­ of the characterizing data that are measured on ma­ cients for helium determined for a few of the grades of terials in the irradiation studies. Since none of these is graphites involved ir. the irradiation studies. Bulk optimized for the Molten-Salt Breeder Reactor (MSBR)

Table 123. He! par MM ten of varioas grades of gra(kite| *

Baft Bv —-v Grade Source* Spec. No. Orientationc density (cm2) (cm) (cm2/sec) (g/cm3) x 10"12 x 10~7 x 10"2

SA-45' CPD 102 AG 1.54 354 3.75 154 A-68T/ sec 111 WG 1.49 332 2.24 123 A-681' sec 111 WG 1.61 291 138 101 H-39S GLCC 51.62 1.78(2) 10.3(2) 3.96(2) 9-32(2) HL-18 ACSP 82 AG 1.87 9.94 3.67 9.22 WG 1.86(2) 8.66(2) 4.43(2) 10-0(2) ATJS-G CPD 41,46 AG 1.86(23 14.8(2) 2-57(7) 8-10(7) WG 1.81(2) 25.7(3) 4.28(3) 17.7(3) P-03 PCC 51,61 1.81(2) 8.34(2) 3.04(2) 7.25(2) 9948 ASCP 101,102 WG 191(2) 7.99(6) 3.75(6) 5.20(6) HS-82 sec 101 AG 1.71 1.09 0386 2.27 82 WG 1.71 2.41 1.25 2.72 ATJS CPD 43,45 AG 1-85(2) 0.256(7) 0.098(7) 2-30(7) WG 1.83(2) 433(9) 0.411(9) 2-36(9) WG 1.85 0308(3) 0.171(3) 0-42(3) AXZ-5Q Poco 101,111 1-55(2) 9.86(2) 935(2) 183(2) AXM-5Q Poco 101,111 175(2) 3.01(2) 2.78(2) 4.96(2) AXF-SQ Poco 82,112 1.83(2) 121(2) 1.10(2) 2.17(2) AXF-5QBG Poco 832 1.83 0.472 0.499 0.962 831 1.90 0.0*11 0.0885 0.162 2 1.90 0.0438 0.0685 0123 1 1.90 04378 0.0655 0-120 5cyP? 1-94(5) 0.033(5) 0.0331(5) 0464(5) 81 1.92 0.00.>6 04096 0.018

'The numbers enclosed in parentheses indicate the number of values averaged. *ASCP: Airco Speer Carbon Products, a subsidiary of Air Reduction Company, Inc. CPD: Carbon Products Division of the Union Carbide Corporation. GLCC: Great Lakes Carbon Corporation. PCC: Pure Carbon Corcpany. Poco: Poco Graphite Inc. SCC: Stockpole Carbon Company. CAG: Across grain, perpendicular to the general a ixis orientation. WG: With grain, parallel with the general a axis orientation.

when* J?ne ~ permeability coefficient for helium at room temperature, 28°C (cm3/sec), BQ • viscous permeability (cm2), n - viscosity of gas, He (poise),

* average pressure across specimen (dynes/cm2), KQ * slip coefficient (cm), F* average molecular velocity of gas, He (cm3/sec). 'A hmpbhrk-based material fired to 2800°C or lugher. fK lanipblack-based material fired to ~1000°C. 'Average of five hollow cylinders (nominally 040 in. OD X 0.125 in. ID X 13 in. long) from the same block. 119

ORNl-MG 71-13*90 an order of magnitude more permeable to rtetium than grades AXM-SQ and AXF-SQ. The latter two are not much different from each other based on these few measurements. Data for grade AXF-SQBG for several specimens were plotted to show the e.fect of the impregnation, and *hat even though the material is relatively uniform, kike all grades of graphite, it can vary appreciably in localized zones. The latter is illustrated in Fig. 12.8 by the results obtained on specimens 831 and 832 that were machined from the same block. The impregnation appears tc itdu-~e the permeability of grade AXF-5Q by- one to two orders of magnitude.

12.6 REDIXHIONOFGRAPHnEPERMEABILrrY BY PYROLYTIC CARBON SEALING C.B.PoBock W.P.Eatberty Graphite to be used in 'he core of an MSB"* must be able to exclude fluoride salts and gaseous fission products. We have been studying techniques to seal the 6 8 X) 12 14 K 18 (HO5) surface of the gtapbite with pyrotytic carbon. Two MEAN PRESSURE (dynes/on?) techniques have been used: a vacuum-pulse urpregoa- tkm technique in which surface pores of the graphite are dosed by plugging them with pyrotytic carbon and gnptote grades AX7-5Q, AXF-5Q, ad AXF-5QBG. a coating procedure in which a continuous surface coating of impermeable pyrotytic carbon is deposited on the graphite. Both techniques have been successful applications, it is not surprising that their permeabilities in sealing commercially available graphite suitable for

KHe are relatively high. These wr.-e determined on use in the core of an MSBR. l-in.-diam disks from 0.1 to O.S in. thick that were In conjunction with the fabrication program a con­ machined with specific orientations from their starting comitant irradiation testing program is being conducted stock. Grades HL-18, ATJS-G, HS-S2, ATJS, and in which graphite samples sealed with pyroh/tic carbon AXF-5QBG illustrate how the permeability value varies are subjected to MSBR conditions of neutron fluence with orientation am! specimen location. and temperature. A HFIR irradiation experisssnt con­ The isotropic Poto grades have been given more taining a number of coated samples and impregnated attention because the AXF series have shown the most samples was recently completed. This experiment con­ resistance to fast neutron damage at 715°C. To more tained 10 graphite samples coated with pyrorytic clearly show the permeability variations from grade to carbon and 12 graphite samples that were impregnated grade and within a grade, the helium permeabilities K^e with pyrolytic carbon. are plotted vs mean pressures in Tig. i2.8 for grades Turning first to the coated samples, four of these have AXZ-5Q, AXM-5Q, AXF-5Q, and AXF-SQBG. The first been cycled twice through HFIR and now have a total three grades are standard materials that represent neutron dose of 2.4 X 10" neutrons/cm3 {E > 50 different ranges of bulk densities, and AXF-SQBG is an MeV) at a tempsratee of 700°C. Three of the samples impregnated, graphitized version of AXF-5Q. All were appeared to be intact except for some small cracks on fabricated from fillers having a maximum particle sue their ends, but independent of this, the helium perme­ of 0.001 in. (ref. 7). In Fig. 12.8 and from Table 12.3 it abilities went from less ihan 10"* to greater than 10"* is interesting to note thai grade AXZ-5Q is more than cm2 /sec. The remaining sample was extensively cracked over its entire surface. A second sei of coated samples has been cycled through HFIR for the fist time and 7. Data taken from comparison chart issued by Foco Graph­ received total neutron doses of up to 13 X 10" ite, Inc., Decatur, Texas. neutrons/cm* 50 MeV) at 700°C. Five of these 120 samples cracked badly and had helium permeabilities of would be expected from the unimpregnatcd base stock greater than 10~2 cm1/sec. However, one of the graphite at similar fluences. samples appeared to be unaffected by the experiment. Preliminary experiments have demonstrated the feasi­ The only significant difference between these two sets bility of coating graphite with pyrolytic carbon. of coated samples is the coaling thickness. The first Samples have been prepared in fluid bed furnaces group had citing thicknesses ranging from4 to 6 mils; designed for coating spherical fuel particles. The small the second set had coating thicknesses of 2 to 3 mib. graphite samples were suspended in a bed of inert The one sample of the second set that survive* h»H s particles that were levitated by a flow of helium. Then coating that was 3 mils thick. Coating thickness and the gaseous hydrocarbon was infected and cracked at ancrostructure are the significant variables, but further various temperatures, and the graphite sample was work wfll be required to determine if satisfactory coated in the same manner as the spherical particles. coatings can be devised. Dense isotropic coatings of pyroiytic carbon tightly The results on the ! 2 pyroiyticaUy impfegnated bonded to the samples were obtained in this fashion; samples are given in Tabic 12.4. Six of these have been however, thh would clearly be a difficult technique to recycled in HFIR to fluences of up to 3.7 X 10"; six use on !*rge grapuite tubes or cylinders. new samples have received only dieir first irradiation up A carbon reststat.ee furnace has been built for coating to 1.2 X I023. The new samples appear to be experiments with larger graphite samples. This furnace significantly better than previous samples irradiated to is similar to conventional fluid bed coating funuc-s but smdar fluences. The pore size distribution of these will permit the investigation of depositing dense ist^ samples wil be examined by mere jry porosimetry. The tropic pyroiytic carbon on a fixed substrate by altering amount cf pyroiytic carbon requiied for sealing can be such variables as gas flow, gas mixture, and bed controlled by varying process parameters. Helium per­ condition. The furnace is c mplete, and samples are meabilities of less than 10~* cm2/sec have been being prepared for coating. obtained in graphite samples whose weight increase was less man 4% with a processing time of only 2 hr at 12.7 THE MAGNIFIED TOPOGRAPHY 750°C. Graphite samples sealed in this manner should OF GRAPHITE SEALED WITH behave more like tumnpregnated base stock graphite. A PYROLYTIC CARBON number of samples contaming the minimum amount of W.H.Cook carbon needed for sealing has been prepared for the next experiment ir an attempt to control the neutron- We have begun a detailed characterization of the induced expansion of the graphite. graphite grades sealed v/ith pyrocarbon. The objectives As noted in Table 12.4, one of the samples has are to learn more abcut the pyrocarbon-sealing tech­ increased its length by 11%, or substantially more than niques and to determine what produces a pyrocarbon seal that has the manr.ium resistance to damage by fast neutrons. Parts of the early phases of this work are evaluations Table 12.4. of the various techniques available for characterization of the pyrocarbon sealants. The scanning electron Permeability Permeability Fhience microscope (SEM) is one of the potential tools for this Sample befove after (neutrons/cm2) ULlL 2 2 work. A preliminary examination of the surfaces of No. (cm/*ec) (cm /sec) (X 1021) (%) unirradiated grade AXF specimens of graphite ma­ 1231 2.3 X 10^ 5.1 X 10^ 12.11 chined in the shape of HFIR specimens, 0.128 in. ID by 1208 13 X 10^ 2.2 X 10"6 8.76 0.400 in. OD by 0.500 in. long, has been made with an 1236 22 X 10-* 10 X 10"* 7.82 SEM.2 One specimen was as-.nachined, and the other 1211 1J X 10"* 6.2 X 10"7 12.45 had been impregiiated with pyrocarbon from butadiene HR20 IX 10"* 2.3 X 10~* 549 8 at 750°C and heat treated at 1650°C. HR12 1X10" 64 X lO'* 11.35 1305 4A X 10"10 7.2 X 10"* i7.06 0.7 The examination of the as-machined specimen shown 1216 5.9 X 10"'° 9.8 X 10"* 21.19 2.2 in Fig. 12.9a suggests a tearing of the filler particles HL32 1.6 X10~* 9.1 X 10"* 2060 0.8 more than a cutting operation. At this magnification of 2 1182 i.7 X 10"* 1.5 X 10" 31.24 6.0 2C00X, the surfaces appear to *>e mosaic of irregular- 1181 5.1 X 10^ 9.0 X 10 "* 36.97 11.0 1163 7.0 X 10"* 2.9 X 10"* 25.67 2.0 shaped, eq taxed particles. In Fig. 12.%, at the same magnification, the surfaces of the pyrocarbon-sealed 121

PHOTO £658-7!

Ffc. 12.9. astHFIR •radiation spednsu. (*) A Hce 1650*C. 2000X. Note: The satacss of the

specimen showed that pyrocarbon covered the exposed 1Z8 REDUCTION OF PERMEABILITY filler particles so that they now had sphere-like shapes BY FLUID IMPREGNATION and appeared to be a surface cr.nposed of closely W.H.Cook stacked, rough spherules. Since the sealing with the pyrocarbon was desigued to be an impregnation rather It has been proposed* that unfueled salt impregnated than a surface coating, the latter surface appearance is into the accessible pores of graphite may be a practical not illogical. way of reducing its gas permeability. Preliminary tests There are some charging-up effects observable in Fig. with an analog impregnation with bismuth and unfueled 12.9 that might have been eliminated or reduced by salt impregnation indicate that helium permeability of a coating the specimens with a thin film of metal prior to permeable graphite can be reduced to the range of 10"* their examination with the SEM. We did not do this cm* /sec. Additional studies are required to determine because such an operation would be impractical in our the practical limits for reducing permeabilities by this future work With irradiated specimens that we periodi­ technique and to evaluate die effectiveness of such fluid cally examine and recycle for additional radiation. This SEM work indicates promise; however, addi­ tional work with it remains to be done in order to evaluate it and apply it to our objectives. 8. R.E.Evns in etal., Reactor Chemistry Drfhfon. 122 impregnations for reducing fission gas penetration into salt-impregnated specimen over the bismuth-impreg­ the graphiU. nated specimen is probably due to the shrinkage that In an analog test using impregnation by bismuth occurs in the salt when it freezes. This is supported by (which expands on freezing) instead of molten salt, the the facts that the pore entrance diameters of die hehum per-ieabihty was decreased two to fire orders of unimpregnated grades AXF and AXF-5Q are concen­ magnitude dependmg on the grade of graphite used.9 trated at 1 #*, and there is a larger viscous component of The loweit permeability values were in the 10'* gas flow for die specimen impregnated wim the frozen cm2/sec r mge. Apparently, there were enough <0.25- salt vs the one impregnated with frozen bismuth. The iaa pore < ntraice diameters that were not impregnated freezing of the salt apparently makes available porosity to preven the permeability from attaining the desired that has relatively large effective pore diameters com­ range of <10~* cm2/sec. pared with those remainingi n die bismudi-impregnated Prior to the £arly shutdown of the MSRE, we had specimen. The salt s the nsottes state should sea! planned to determine the actual effect of an unfueled against helium flow as weU as die frozen bismuth. salt anmregeant on graphite from the standpoints of the Additional studies are required to determine (1) the •eduction of gas permeabilities and gaseous fission practical Bn->*5 for reducing gas permeabilities by this products penetration into the graphite in the MSRE technique and (2) the diffusion rates of fuel salt environment. To do this, we impregnated evacuai d components into die impregmnt(s)- The final gas specimens of grade AXF-SQ graphite with NaF-BeF2 permeahikty values attained will determine the effec­ (66-34 mole %) under a pressure of 200 pa at 705°C. tiveness of such impregnations for reducing fission gas This should hare caused pore entrances down to penetration into die graphite. Xenon-135, which has a approximately 0.5 -in in diameter to be filled. Equip­ high cross section for drama! neutrons, is dt* fission gas ment imitations for the required salt temperature of primary concern. Uranium (or plutonium) and prevented our using enough pressure to penetrate pore salt-soluble fission product i ngration into the impreg- entrance dianvters down to approximately 0.25 am as nants wml be die primary concerns in the diffusion rate was done in the analog test with the bismuth. The permeability values for the bismuth- and die salt- impregnated specimens are compared with their con­ 12.9 R^DAMENTAL STUDIES OF RADIATION trols m Table 12.5. The higher permeaUity of the DAMAGE MECHANISMS IN GRAPHITE S.M.Ohr T.S.Noggfe

9. W. H. Cook, MSR flupw Monthly frogr. Rep. September Irradiation of ophite single crystals at temperatures 1969. BCSR-69-93, p. 33. of 300 to 600°C in a 200-kV electron microscope leads

TaMe VIS. renneasany cticcts on a graphite awpiegnate d witk sofiimed tmmmtk or NaF-fteF2

Permeability parameters* Graphite SpCC&BkCD Imprega !ion 2 K at 1 atm trade Number Type B (cm ) Ko(cm) He 0 (cm2/sec)

AXF 1 Hoflow cylinder None 3.30 X 10"'2 1.94 x 10"7 4.10 x 10""2 1 Cylinder Bismuth 5.49 x 10"'7 2.15 x 10":' 3.76 X 10"* AXF-5Q 5 Disk None 1.29 X 10"'2 1.22 X 10"1 2.39 X 10"2 5 5 AXF-5Q 4 Disk NaF-BeF2* 1.45 X 10"' 2.47 x 10"' ° 4.52 x 10"

«AHe«(*©/n)

*%*oK. 2 where KHt * permeability coefficient for helium at room temperature, 28°C (cm /sec), BQ * viscous permeability (cm2), T) * viscosity of gas. He (poise), (p) * average pleasure across specimen (dynes/cm2), KQ * slip coefficient (cm), V" average molecular velocity of gas, He (cm/sec).

*The nominal composition is NaF-BeF2 (66-34 mole %). 123 tc the formation of visible spot-type damage structure with variation of the diffraction condition has been in relatively Jwrt tunes. Studies of the contrast of the found to be consistent with and hence attributable to defect dusters for various diffraction conditions have the stacking fault present in the prismatic dislocation shown that the defects are dislocation loops of inter­ loop formed by the dustering of interstitial atoms. stitial type. In dark-field micrographs as in Fig. 12.10, Figure 12.11a shows the intensity of the diffracted the damage dusters frequently appear as both Mac* and bran as a function of the position ut a stacking fault in white spots in roughly equal numbers.1 ° This Mack and a 2300-A-ihick graphite crystal. The osculation of the white contrast is found to be quite sensitive to the intensity with depth about the perfect crystal value diffraction condition, that is, the deviation from the (dashed line) predicts three layers of dark (black) spots Bragg condition. Stereoscopic study of this structure and two layers of light (white) spots as has been has shown that the black and white spots are present as observed experimentally. several alternating byers paraiiei to the surface of the Other aspects of the contrast of these defect dusters, specimen. The behavior of this black-white structure although qualitatively consistent with the beharior expected cf interstitial-type dislocation loops, suggest that the strain contrast is less than would be expected 10. S. M. Ohr Md T. S. Haggle, MSR Program on the basis of diffraction contrast theory employing Ptotr. Rep. Feb. 28. 1971. ORNL-4676, pp. 174-76. the displacement field derived from isotropic elasticity

Fig. 12.10, (1011) Dark-TieU micrograph of graphite irradiated at 400°C with 175-kV election*. InterrtitiatHype prismatic dislocation loops show black and white contrast as predicted by calculations shown in Fig. 12.11.60,000x. 124

ORNL-DWG ?S -13691

(10Tl) (1011) S.F. ANDDISL.

o

QC D 0> QL o

I I- 2 o or u. Q. O O

U! I

o I h- 0. UJ Q

0.5 1.0 0 0.5

j*ap, DIFFRACTED INTENSITY

F%. 12.11. Computed depth dependence of die diffracted intensity for interstitial-type prismatic dislocation loops in a 2300-A-thick graphite specimen. Diffraction conditions and specimen thickness correspond to Fig. 12.10. (a) Stacking fault contrast, (o) Stacking fault and dislocation contrast. Dashed lines indicate perfect crystal diffracted intensity, shaded areas indicate depth regions of dark (black) loops, and unshaded areas indicate regions of light (white) loops.

theory. In order to clarify this matter, the stress and On the basis of the anisotropic elasticity theory of displacement fields for a circular prismatic dislocation atomic displacements around a dislocation loop, calcu­ loop have been derived using anisotropic elasticity lations of image contrast in the electron microscope theory. The results indicate that the overall effect of have been carried out in the IBM-360 computer. It is crvstal anisotropy is to reduce the stress and displace­ found that the crystal anisotropy does influence the ment fields around the loop by about an order of intensity and apparent size of the image of a dislocation magnitude, except for the component of displacement loop. Figure 12.116 shews the calculated diffracted normal to the loop plane which is increased by about a intensity at the exit surface of the specimen for the factor of 2. These results appear reasonable when one central region of a loop as a function oi the position of considers the nature of chemical bonds in graphite, the loop in a specimen for diffraction conditions similar which calls for a strong covalent bonding in the na&al to those present in Fig. 12.10. The variation of the plane conunred with a weak van der Waals-type intensity relative to the perfect crystal value is similar bonding across the basal plane. When a dislocation 'oop to that for the stacking fault alone (Fig. 12.11a), is created between basal planes, tlie crystal expands indicating that the stacking fault is dominant in more readily along the c axis giving riset o large atomic determining the contrast for the conditions considered displacements in this direction. In the basal plane, here. Experiments and calculations are currently being graphite is elastically too rigid to accommodate appre­ made to examine more closely the agreement between ciable displacement. observed and calculated contrast. 13, Hastelloy N

H.E. McCoy

The search for a chemically modified composition of The second area of interest deals with tht precipita­

Hastelloy N with improved resistance to irradiation tion of Ni3Ti in titanium-modified Hastelloy N. Recent damage continues. The elements of primary concern are observations indicate that a T. concentration of about Ti, Nb, Hf, Zr, Si, and C. We continue to approach the 2% may provide good resistance to irradiation embrit- problem by initially making small laboratory melts and tlement at 700°C and higher. We are concerned whetier then procuring SO- to 100-lb commercial nv?lts. This this amount of Ti will promote the formation of NijTi gives us some feel for the problems that will be at various temperatures. Precipitation of this inter- encountered in scaleup of these alloys to production metallic dramatically increases the strength, but causes size (10,000 lb or greater). This work involves mechan­ embriitiement. ical property studies on unirradiated and irradiated The last area of study reported deals vith preliminary samples. observations of strain-induced precipitation in modi­ Our compatibility programs are involved with the fied alloys. Carbides which precipitate during a creep- corrosion of Hastelloy N in several fluoride salts and in rupture test are different in morpho'ogy and distri­ steam. The salt of primary concern is the new proposed bution from those generated during short-term tensile coolant salt, sodium fluoroborate. Several thermal tests or elevated temperature exposure in the absence of convection and two pump loops are committed to strain. studying corrosion in this salt. Steam corrosion work continues at two facilities. Hastelloy N is currently 13.1.1 Mkrostnictures of Hf Modified HasteDoyN being exposed in the unstressed and stressed conditions. Laboratory Melts The laboratory heats discussed in this report have a base composition of Ni-12% Mo-7%Cr-4% Fe-0.2% 13.1 ELECTRON MICROSCOPY STUDIES Mn and are modified with 05% Hf, 0S% Ti, and R. E. Gehlbach S. W. Cook 0.6% Nb unless otherwise noted. The standard carbon and silicon concentrations are OJOS and <3DJ01%. Our studies of the effects of alloying additions on the The microstructure characteristic of hafnium- microsiructures in modified Hastelloy N at elevated modified laboratory melts has been discussed previ­ temperatures have concentrated in three primary areas. 1 3 ously ' and is shown in Fig. 13.1 for an alloy The first ?.rea consists of the effects of Hf, as a sole addition or in combination with Ti and Nb, on carbide precipitation. These studies have included variable 1. R. E. Gehlbach, C. E. Sesoom, and S. W. Ccok, MSR concentrations of C and Si and both laboratory and Program SemUmm. Progr. Rep. A.?. 31, 1969, OAN.V4449, small ooinmercial melts. We have achieved a reasonable pp. 193-95. 2. R. E. Gehlbach and S. W.lCook, MSR Program Sermon**. understanding of precipitation processes in laboratory Progr. Rep. Feb. 28,1970, ORNL4548, pp. 131-38. heats containing Hf; however, its effect in commercial 3. R. E. Gehlbach and S. W. Cook, MSR Prognm Semkamu. alloys is not clear. Prop. Rep. Aug. 31,1970, ORNL4622, pp. 164-65.

125 126

containing 0.7% Hf after aging 200 hr at 760°C. Small the same size or slightly smaller than the matrix precipi­ particles and platelets of MC carbide, about 0.1 to 0.3 tates. These grain boundary carbides are closely spaced, tan in diameter, precipitate throughout the matrix with and there does not appear to be any significant the exception of a region along grain boundaries coarsening of the matrix carbides between 10 and 1000 approximately 2 tan wide that is denuded of precipi­ hr of aging. However, a high dislocation density is tate. Grain boundaries contain many small MC carbides present around those precipitated during aging 10 hr at 760°C. No matrix precipitate is observed in annealed material prior to aging. Effect of aging temperature. The microstructure of the reference alloy (alloy 329) in the Hf-Ti-Nb series is shown in Fig. 13.2A after aging 1000 hr at 760°C. The precipitation process is similar to the hafnium-modified laboratory heat discussed above. The matrix MC car­ bides are somewhat coarser (0.3 to 0.5 tan) in the more highly modified series. In addition, a very small amount of MC carbide precipitates in the stacking fault mor­ phology previously observed in the titanium-modified alloys. This stacking fault precipitate (SFP) is much finer in the alloys modified with Hf-Ti-Nb than in those modified with Ti alone. In general, the SFP only occurs in the interior of grains. Aging at the lower temperature of 650°C results in finer matrix precipitates than at 760°C. Thin platelets are generally formed at 760°C (Fig. 13.2a), and particles and thick platelets are formed at 650°C (Fig. 13 2b). The amount of precipitate is considerably & Fig. 13.1. Typical MC carbide distribution in lufnJum- higher at 650 C than at 760°C, and formation of SFP is modaled hasteBoy N. The alloy contains 0.7% Hf and 0.06% C much more prevalent at 650°C. In addition, a disper­ and was aged 200 hr at 769°C. SOOOx. sion of very fine carc

Rf. ! 3.2. MC carbides in mkrostractare of HasteUoy; N containing 03% Hf, 0.5% Ti, 0.6% Nb, and 0.05% C. Annealed 1 hr at 1I80°C and aged 1000 hr at (a) 760*C and (b) 650°C. S000X.

L i "i 127 throughout the matrix after aging at 650°C (not formed at 650°C in heats containing lower carbon resolvable in Fig. 13.2a). These extremely fine precipi­ levels. A carbon concentrate >n of 0.087% results in tates are also present in alloys modified only with considerably more fine matrix precipitate at each hafnium after exposure at 650°C. temperature, but much primary M2C is also present. Effect of carbon concentration. The effect of carbon Effect of silicon additions. Additions of silicon to concentration on precipitation in the Hf-Ti-Nb series is Hf-Ti-Nb-modified alloys containing the standard 0.05% shown in Figs. 13.2 to 13.4. The microstructures of an carbon results in massive silicon-rich primary M«C alloy with 0.008% C (alloy 331) after aging 1000 hr at carbides primarily located in grain boundaries and as 760 and 650°C are shown in Fig. 133. The matrix stringers. The microstructures resulting from the addi­ carbides are slightly smaller at 760°C (Fig. 133a) than tion of 0.44% silicon are shown in Fig. 135 after aging those in the alloy with the nominal 0.05% C (Fig. at 760 and 650°C. Large M«C precipitates are in the 13.2a), but are present in a much lower concentration. grain boundaries in Fig. 135a after exposure at 760°C. Grain boundary carbides are very numerous, however. No matrix precipitation of MC-type carbides occurs at A high density of very fine carbides is present after this temperature (compare with Fig. 13.2a where the Si exposure at 650°C (Fig. 1336). With 0.014% C (alloy content was <0.1%). At the lower aging temperature, 332) the microstructure after aging at 760°C is similar precipitation of all morphologies of MC discussed to that of the very low carbon alloy, •> it with more previously are present in addition to the large M*C carbides present. particles in the grain boundary (Fig. 1356). Some fine Increasing the carbon concentration above the MC is also present in the grain boundaries after aging at standard (0.05%) level generally results in fewer but 650°C. coarser carbides. The microstructures of an alloy Silicon additions of about 0.15% result in a smaller containing 0.14% carbon (alloy 33S) after aging at 760 quantity of M6C and corresponding increases in the and 650°C are shown in Fig. 13.4. Lirge primary amount of MC precipitating in the matrix during aging carbides of the M2C type are present at both tempera­ at both 650 and 760°C. Thus, silicon removes much of tures. The characteristic matrix MC carbide is virtually the carbon from solution that would otherwise be absent at 760°C but is present in relatively high available for MC precipitation during aging. concentrations at 650°C. Its occurrence is generally In summary, MC carbides which precipitate in the limited to large-grained areas which do not contain large matrix of Hf-Ti-Nb-modified Hastefloy N are present in quantities of M2C. The MC carbide is coarser than that various sizes, morphologies, and concentrations de-

Fig. 13.3. MC carbide dfetribntiofl in Hf-Ti Nb modified HuteHoy N coatataig 0.008% C. Annealed t hr at 1180*C andajed 1000 hr at (a) 760°C and (b) 650°C. 50O0X. 128

YE-10362 -10358

Fa> 13.4. Carbide datfritratioa in hfeh carbon (a 14%) heat of Hf-Ti-Nb awdSed Hasteatoy N. Large carbides are M2C; small particles are MC. Annealed 1 tara t 1180°C and aged 1000 hr at (a) 760°C and (b) 650°C. S000X.

Pfc> 13.5. Effect of 0.44% atkoa on miaotttvctares of Hf-Ti-Nb modified Hutdtoy N (0.05% O. Large carbides arc M6C; others are MC. Annealed 1 hr at 1180°C and aged 1000 hr at (a) 760*C and(b) 6S0°C. 5000X. 129 pending on the aging temperature at the standard 0.05% Material from both of these commercial heats was carbon level. Decreasing the carbon content decreases remehed and fabricated at ORNL with the same the see and amount cf matrix MC precipitated. procedures used for the laboratory heats. The micro- Increasing the carbon level above 0.05% results in large structures of the lab remits after aging at 760°C are primary M2C carbk'es at the expense of fine MC. similar to each other. The remetts differ from the The addition of silicon results in precipitation of large straight commercial material in that grain boundary primary silicon-rich M«C carbides with subsequent precipitation of the reprocessed alloys strongly re­ precipitation of >-IC dependent on the amount of sembles that of conventional laboratory melts: fire carbon remaining in solid solution. particles with no precipitate adjacent to the grain Commercial alloys. We have examined the micro- boundaries. Figure 13.6ff shows typical grain boundary structures of nearly all of the commercial heats of precipitate and a patch of heterogeneous matrix carbide modified Hastelloy N listed in Table 13.1 after aging at in the commercial alloys containing 0.8% Hf. The 650, 760, and in several cases 700°C. Our general laboratory remehs (Fig. 13.6b) do not have carbides observations have been reported previously.2'3 A par­ adjacent to the grain boundary. A very small amount of ticular concern is that the rrdcrostructures of the heats matrix carbide is present in the remehs after aging containing hafnium do not resemble those of laboratory although heterogeneously distributed. melts with similar compositions. Instead of platelets The microstructures of the remehed alloys aged for and fine particles of MC carbides in the matrix and 200 far at 650°C are both tree of precipitate. This grain boundaries, the microstructure consists of large microstructure is different from that of the commercial amounts of MC in jagged grain boundaries and ex­ and the laboratory metis, and we currently have no tending into the matrix 1 to 3 fun. The grain interiors explanation for this anomalous observation. are generally quite free of precipitates, the alloy modified only with 0.8% Hf (heat 70-796) does exhibit 13.12 Ni3Ti tkminTi-Modified some matrix MC, although it is very heterogeneousry N distributed and much larger in size than that observed in the laboratory heats. The grain boundaries are rather Observations that Ti concentrations above 1% result typical of the -Hher commercial heats, although less in improved postirradiation ductility after irradiation at carbide is present adjacent to the boundaries. Similar temperatures above 700°C have generated renewed observations were made on a commercial aDoy (67-504) interest in using Ti as the sole modifying; element in containing 05% Hf that was produced by a different Hastelloy N. Precipitation of Ni3Ti would be unde­ vendor. sirable, as its effect is one of dramatic strengthening at

T*Me 13.1. Com* ofexnm

Concentration (%) Alloy No. Mo Cr Fe Mo Si Ti Zr Hf Nb C

70-7S5 12.3 7.0 0.16 0.30 0.09 1.1 04)12 <0.003 04»7 04)57 70-77.7 13J0 1A 0.05 037 <04» 2.1 0.011 <0.i'l <0.01 04M4 70-/96 12.5 73 0.054 0.64 0.01 0.04 0.024 a79 0.04 04M 69-648 12.8 6.9 03 0.34 o.(b 092 0X105 <04)5 1.93 0.043 69-714 13.0 8.5 0.10 035 <0J05 0.80 0.028 <0L01 1* 04)13 70-835 12.5 7.9 0.68 0.60 0.05 0.71 <04toS 04)31 2450 04W2 70-786 12.2 7.6 0.41 0.43 0.08 0.82 0.024 <04»3 042 04M4 69-641 13.9 6.9 0.3 035 0.02 13 0.021 0A0 <04K 04)5 70-787 12.3 7.0 0.18 0.43 0.09 0.90 0.038 0.77 0.12 04X1 70-795 13.7 83 0.035 0.63 0.03 13 0.018 0.42 04)05 04)5 70-788 12.1 73 0A3 0.41 0.1 \A OJ020 030 047 04)27 70-797 12.7 7.0 0.29 038 0.02 039 0.040 0.78 u.?S 04H9 70-798 13.5 7.9 0.26 031 0.02 0.71 04)12 0.28 0.94 04)36 68-688 14.3 7.1 44> 0.46 038 OJOI <04H0 <0L05 <04R5 04)79 68-689 13.7 7.4 4.6 0.46 033 036 <0J05 <04)S <0JC6 04)81 69-344 13.0 1A 4.0 036 034 0.77 04)19 <0.1 1.7 0.11 69-345 13.0 8.0 4.0 032 032 14)5 04)38 0J8 <04>1 04)78 130

V€-K>395 YE-10396

Ffc.134. Mkiortrecf e« of Hattdpy N cc •ItJaif 0A% Hf after. 200 H tt 760°C (a) Comme rialallo y 70-796 and (b) laboratory remett of 70-796. Carbides are of the MC type. S000X.

the expense of ductility. Therefore, we are investigating 2.4, and 2.9% Ti. The specimens examined to date were the concentration of Ti required to promote the aged 10,000 hr at 700°C. Large quantities of interme-

formation of Ni3Ti at various temperatures and times, tallic Ni3Ti are present in the 2.9% Ti alloy, very homo­ using a series of laboratory melts containing 1X), 2.0, geneously distributed throughout the matrix as shown in Fig. 13.7. The intermetallic is lenticular, appears to be shaped somewhat like a clam shell, and is oriented pauaUel to the cube planes. Although present in the

2.4% Ti alloy, the Ni3Ti is heterogeneously distributed and present in much smaller quantities. Isolated parti­ cles were observed in the 2.0% Ti, but they are much smaller nan in the more highly alloyed heats. The unstressed buttonhead from a creep specimen of the 2% alloy was examined. The specimen had been annealed and aged for 1000 hr at 760°C before a 47,000-psi creep rupture test at 650°C that lasted about

5200 hr. A considerable amount of Ni3Ti is present, although poorly developed, and was probably nucleated during the 760°C age prior to the 650°C exposure. We will look at these alloys exposed at 650 and 760°C for various times u> define more closely the maximum Ti concentration allowable for service in this temperature

range. The effect of irradiation on Ni3Ti will also be investigated.

13.13 Strain-Induced Preciptotkm flf, 13.7. M31l awfiahtttaifci nmmWor N coata ~«f 24% TL The WfeTi, formed by agng 10,000 hr at 700*C, it m Modified HasteloyN teaticahr sad exhibits friaje contrast. MC carbides in the stacks*! fasdt awrphoiofy are alto pretcnt. Dark field mkro- Examination of the gage sections of several creep-

r(111)reflectMM. IO.00OX. rupture specimens reveals that precipitation during

h 131

elevated temperature tests is different from that which provides the sites for precipitation during the remainder forms in the unstressed buttonhead or in aged material. of the test. The typical MC carbide distribution in a 1.2% Ti- A different typ; of strain-induced precipitation modified Hastelloy N (alloy 467-548) after a 40,000-psi occurs in alloys containing Nb as a major addition. This creep test lasting 450 hr at 650°C is shown in Fig. 13.8. precipitate is present as very thin sheets as shown in the Precipitation occurs as very fine carbides (200 to 1000 bright field and precipitate dark Meld micrographs (Fig. A) in high dislocation density slip bands. These disloca­ 13.9). The specimen is from a heat containing 155% tions are out of contrast in Fig. 13 AT The carbides are Nb and 05% Ti (alloy 69-648). The 63,000-psi creep clearly imaged in Fig. 13.86, a dark-field micrograph test lasted 470 hr at 650°C. As before, the initial using a carbide (220) diffraction spot. Precipitation in structure after loading consisted of bands of tangled the absence of the creep strain consists of carbides in dislocations. Although the resulting precipitate has not the stacking fault morphology, nucleated around re­ been identified, it does not appear to be the MC-type sidual primary carbides. carbide usually found in these alloys. The strain-induced precipitate is not observed in In reality, then, the nucrostructures of specimens short-term tensile samples tested over a wide range of creep tested above the yield stress are not the same as strain rates. The dislocation structure generated in those which would be found in a reactor constructed of tensile tests is characterized by relatively long, straight, annealed material and operating below the yield stress. oriented dislocations with little or no tangling. The The property changes resulting from the necessity of dislocation structure of creep test specimens is mark­ performing creep tests at stresses above the yield point edly different from that generated in tensile tests. would be an apparent increase in yield strength and Although annealed specimens are used for both types of possibly lower ductility. The extremely low creep rates tests, the load required for a creep test is well above the found in the Nb-Ti alloys are indicative of the higher yield point of the alloys. The application of this load to strength. The Nb-TMnodified alloys having this strain- the specimen results in very rapid plastic deformation induced precipitate are extremely strong with very up to approximately 5%. The dislocation structure after respectable ductilities, generally above 20%. this strain-on-loading consists of bands of tangled We will be investigating the extent of this strain- dislocations in [110] directions. This configuration induced precipitate in several of the modified alloys and

Pif.134. Sliahhlwil MCcarMJapuiifHaliiia at lJ%1Vwo#B>illiililuj N miwil «40jatprfX6frClar4id*t. I : (a) Bright field;(b ) Dvk fieldon * ,220) carbide diffraction spot. 12 «W0x. 132

Ffe. 13.9. SOMwdttd pnapitMtkM m 1.9% Nb-0.95% Tt-modifM Hutefloy N (teat 69648) stressed at 6S0°C for 475 hr. (a) Bright field;(b ) Dark field using precipitate diffraction spot.

also the effects of this starting microstructure on 133 WELDABILITY OF SEVERAL mechanical properties. MODIFIED COMMERCIAL ALLOYS

13.2 MECHANICAL FROFERflES B.McNabb H.E. McCoy OF UNIRRADIATED MODIFIED The double-vacuum-melted and electrosbg-remelted HASTELLOYN commercial melts of modified HasteDoy N have been B.McNabb HE. McCoy further evaluated by mechanical property tests. Some unirradiated mechanical properties and relative welding One of the prime requirements for nuclear reactor characteristics were previously reported.4 Mechanical materials is long-term metallurgical stability. We are property tests on transverse specimens (0.125 in. diam aging nuteriab at anticipated service temperatures and X 1.125 gage length) from welds of these alloys have measuring the mechanical properties to determine been conducted. whether the material is stable. Some modified HasteOoy Table 13 3 is a tabulation of the tensile properties of N specimens were solution annealed (1 hr at 1177°C) these alloys at 25*C and a strain rate of 0.05 mm"' and and then aged st 650 and 760°C for 1000,3000, and compares the properties of the base metal with the 10,000 hr. These will be subsequently creep tested at welded material in the as-welded and stress-relieved 650*C and 55 JOOO psi or at 760°C and 20JOOO psi. conditions (annealed 8 hr at 870°C). The base-metal The testing is partially complete, and the rupture lives yield stresses are from 40,000 to 55,000 psi, the are compared in Table 13.2. ultimate tensile strengths range from 100JOOO to The results to date indicate that the alloys are quite 130,000 psi, and the fracture strains vary from 55 to stable with only small changes in properties. The fracture strains of afl the alloys were 20% or greater, indicating no serious reductions in ductility during 4. a E. McCoy and B. McNsbb, MSR Frognm Semkamu. Prop. Rep. Feb. 28,1971. ORNL-4676, pp. 1*1-8*. 133

Table 13.2. The effect of iji^ o« raptureSf e of wiowrfoys at 650 a»d760°C

Heat Temperature Stress Solution 1000 hr 1000 hr 3000 hr 3000 hr Numbei* (°Q (psi) anneal at 650°C at 760°C at650°C at 760°C

69641 650 55,000 295.9 219.0 212.6 162.6 1933 760 20,000 6713 488.0 376.8 399.9 497.2 69648 650 55,000 1759.5 703.4 9563 1294.7 1251.7 760 20,000 769.5 380.4 1558.4 430.4 469344 650 55,000 912.7 142.8 183.6 403.6 152.9 760 20,000 231.1 128.2 111.7 226.7 354.7 46934S 650 55,000 285.6 15633 210.2 339.4 120.7 760 20,000 259.8 209.9 160.1 178.3 150.2 469714 650 55,000 146.3 379,4 3013 269.3 393.2 760 20,000 497.4 3613 413.2 403.0 362.0 470727 650 55,000 845.2 1088.4 378.1 919.4 591.2

760 20r0C0 333.8 407.9 378.1 344.9 353.0 470785 650 55,000 81.7 85.0 87.2 84.2 89.8 760 20,000 338.1 329.9 234.9 257.8 254.0 470786 650 55,000 132.2 477.7 1093 107.6 110.7 760 20,000 343.1 412.0 3543 346.4 295.7 470787 650 55,000 400.8 2293 254.8 309.7 155.1 760 20,000 4503 445.8 435.1 465.4 4873 470788 650 55,000 1251.0 1336.2 1069.7 1164.8 792^ 760 20,000 660.0 686.2 758.1 478.0 481.2 470795 650 55,000 246.0 283.0 151.2 230.9 196.7 760 20,000 469.7 730.2* 483.7 418.8 398.3 470796 650 55,000 292.4 146.7 70.4 112 J 853 760 20,000 418.8 263.2 205.4 435.3 293.8 470797 650 55,000 827.7 546.2 400.9 485.4 484.2 760 20,000 796.6 677 A 615.0 670.9 7063 470798 650 55,000 665 J6 333.0 239.8 258.7 21435 760 20,000 524.8 580.0 608.2 524.4 5633 470835 650 55,000 39113 1989.35 760 20,000 748.1 716.7 602.4 566.1 645.4

sSee Table 13.1 for chemical compositions. *42340 pa.

80%. The weld metal has a higher yield stress than the characteristic of these nickel-base alloys. The base-metal base metal and a lower fracture strain, but the ultimate yield strengths of these alloys at 650° are in the 25,000- tensile stresses are equivalent. The stress relief anneal of to 35jOOO-psi range, the ultimate tensile strength ange 8 hr at 870°C lowers the yield stress only slightly and from 70,000 to 100,000 psi, and frcture strains from recovers only a small fraction of 'die base-metal duc­ 40 to 65%. tility of the modified alloys, whereas it was sufficient to The yield strengths of the weldment specimens are recover most of the base-metal properties in the approximately double those of the base metal and are standard alloy. As reported previously,1 a higher reduced only about 10,000 psi by the 8 hr at 870°C temperature anneal (1 hr at 1175°C) or posssbty longer anneal. The fracture strains are increased a few percent times at 870°C would be required to recover the by the anneal. Failure generally occurred in the weld base-metal properties of the modified alloys. Failure metal in transverse weld specimens. generally occurred in the weld metal of the transverse Table 135 compares the creep-rupture properties of weld specimens. these alloys at 55000 psi and 650°C in air. There are Table 13.4 shows the tensile properties of these same large variations in the rupture lives of these alloys m alloys at 650°C. The same trends shown at 25°C are creep at 650°C, even though there are only small apparent at this temperature, but the fracture strains of differences in the yield strength of the base metal at 25 UK weldment spcTmens are lower at 650°C. A ductility and 650°C (Tables 13 J and 134). In general, the minimum in this temperature range appear* to be a rupture lives of the weldment specimens were much 134

Table 133. Tensile properties at 25°C of several alloys4

Heat Yield stress Ultimate stress Fracture Reduction in History* number (psi) (psi) strain (%) area(%)

70-785 A 40,400 114,300 69.8 57.7 B 86.100 117400 212 62.3 C 74,100 .'13,400 213 58.8 70-727 A 48,600 133.000 62.6 46.9 B 83,600 116,600 20.6 54.1 C 60,700 127400 31.1 55.9 67-504 A 37,400 104,800 73.2 73.7 B 58,000 101,400 40.2 55.0 C 50,000 104,900 37.3 45.3 70-796 A 39,800 116,000 64.0 54.3 3 71,400 91,000 12.6 27.9 C 59,700 98,200 18.4 30.6 69-648 A 44,700 116300 74.2 42.6 B 75,300 118,600 33.3 38.0 C 65,400 111300 31.0 39.4 69-714 A 41,800 109300 81.1 51.6 B 80,600 103,700 28.1 46.9 C 62,100 107,600 35-0 54.9 70-835 A 54,500 144,700 59.0 55.2 B 87,100 117,200 19.7 61.7 C 82300 116,700 27.7 59.7 70-786 A 37,400 106300 73.1 63-7 B 78,400 98300 124 46.4 C 75,500 114300 19.9 45.7 69-641 A 44,900 117,100 72.6 54.7 B 73300 113,700 293 524 C 65,500 116300 36.7 42.0 70-787 A 40300 113,200 694 62.4 B 85300 11830 20.4 49.9 C 66,400 93300 133 24.7 70-795 A 49,700 130300 64.3 39.7 B 87300 121,600 20.3 39.7 C 72200 116400 24.9 33.9 70-788 A 42,200 114,700 664 63.8 B 78^00 110,900 21.2 63.0 C 69300 113300 294 593 70-797 A 44300 123,400 65.4 52.4 B 88300 127400 24.9 543 C 65,200 111300 24.9 503 70-798 A 42300 121300 663 49.0 B 86300 119300 213 30.2 C 75.200 115,100 193 59.7 68-688 A 46,100 118,700 593 453 B 88,400 126400 21.4 45.9 C 61,700 113,900 26.9 404 68-689 A 52,100 117,400 55.7 50.4 B 84^00 121300 183 34.1 C 54300 114300 314 353 69-344 A 56400 130,400 56.9 47.2 B 80,700 125,700 343 423 C 67,900 117,200 284 66.4 69-345 A 48300 126400 613 503

'Strain rate of 035 mill'1. *A: base metal, annealed 1 hr at 1180°C; B: weUment, as welded; C: weUment, annealed 8 hr at 870°C. 13S

Table 13.4. Tensile property ; at 650°C of sevetil alloys3

Heat 6 Yield stress liltimate stress Fracture Reduction in History number (p«) (psi) strain {%) area (%)

70-785 A 26,300 83,300 653 42.4 B 59,200 78,000 13.7 56.7 C 49,000 73,900 13.0 53.7 70-727 A 33,800 94,100 64.7 41.5 B 64,900 82,900 13.9 35.7 43,700 72,300 18.0 35.2 67-504 A 25,600 83,000 66.9 45.1 B 21,100 21,400 2.2 4.2 C 35^00 60.100 13 8 232 70-796 A 27,900 88.300 63.6 45.7 B 29,200 34,700 103 14.4 C 38,000 61,300 11.6 47.0 69-648 A 29,400 78300 46.6 33.9 B 55,100 71,200 10.9 34-3 C 46,300 76300 193 44.1 69-714 A 27,700 78300 56.1 423 B 53,600 71300 12.3 34.7 C 43,700 69,000 20.1 283 70-835 A 33,600 99300 51.1 43.4 B 66,200 83,400 123 283 C 54,300 83300 18.3 29-1 70-786 A 23,900 65,400 45.1 31.0 B 64,100 77,400 103 32.9 C 54,000 80,100 133 303 69-641 A 29,000 92,700 53.3 373 B 56,500 72300 12.1 30.4 C 46,000 76,000 173 41.1 70-787 A 26,800 82300 61.3 39.9 B 60,700 75300 10.9 38.7 C 47300 71300 14.8 35.7 70-795 A 33^00 99300 61.2 413 B 63,400 85300 131 243 C 55,700 86300 21.0 37.7 70-788 A 29,000 71300 453 36.2 B 62,100 76,900 11.0 403 C 51,000 75,900 16.2 41.8 70-797 A 33,400 104,200 59.3 38.4 B 57,300 80,200 173 363 C 51300 85,400 203 53.9 70-798 A 27,000 91300 62.0 443 B 63,900 78300 104 36.6 C 53,300 81,600 173 533 68-688 A 30,600 85,700 *M 31.9 B 67,000 89,600 133 283 C 45400 85,400 23.3 29.1 68-689 A 31,200 79,200 31.4 21.9 B 66,000 87.30J 123 23.1 C 44300 83300 20.4 29.7 69-344 A 33,900 93300 403 293 B 67,000 86300 113 25.2 C 52,200 88300 233 333 69-345 A 37,200 91300 40.4 313

'Strain rate of 0 JOS iirin'1. bA: base metal, annealed 1 hr at 1180°C: B: weldmedt, at welded; C: weldment, annealed 8 hr at 870°C. 136

Tanfc 13.5. Creep mpraie properties of several aOo>s at 650°C and 55,000 psi

Heat Rupture Minimum creep Fracture Reduction in History* number life(hr) rate (%/hr) strain (%) area(%)

70-785 A 81.7 0.0730 53.5 43-3 B 48.0 0.028 6.1 21.9 C 52.0 0.175 19.2 60.4 70-727 A 845.2 0.0152 39.5 364 B 463.7 0.0046 5.1 163 C 189.8 0.0606 17.9 17.2 70-796 A 292.4 0.0165 37.2 31.5 B 409 0.0635 7.2 203 C 6.3 1.188 18.0 45.7 21-543 A 69.0 0.038 24.9 26 3 B 31.7 0.094 5.7 5.9 C 16.8 033 123 16.2 69-648 A 1759.8 0.0005 20.5 18.9 B 98 0.046 5.3 17.9 C 88.8 0.052 11.6 52.8 69-714 A 146.3 0.0835 47.3 51.0 B 455.7 0.0127 15.6 16.2 C 19.4 0.112 11.8 26.1 "70-835 A 3911.9 0.0041 32.0 26.0 B 814.0 00029 8.02 16.8 C 557.1 0.0117 13.7 17.8 70-786 A 132.2 0.0270 34.9 44.2 B 353 0.0275 4.4 273 C 75J0 04)848 14.4 24.3 69-641 A 295.9 0.0740 49.9 43.9 B 346.3 04)238 13.6 19.7 C 241.4 0.0386 17.1 23.1 70-787 A 400.8 0.0320 49.1 47.3 B 93.9 0.036 9.6 35.2 C 513 0.125 12.3 52.0 70-795 A 246X1 0.050 64.7 61.4 B 144.6 0.035 11.9 34.4 C 56.8 0.14 16.9 57.6 70-788 A 1251.0 0.0113 42.0 35.4 B 344.3 0.014 9.2 23.4 C 312.0 0.031 26.3 68.6 70-797 A 817.7 0.0185 48.8 45.6 B 423.4 0.0193 21.8 41.1 C 158.3 0.0830 24.6 45.0 70-798 A 665.6 0.0165 55.5 46.7 B 62.7 0.0360 10.3 28.8 C 164.7 0.0660 22.7 36.3 68-688* A 7E4) 0.0400 19.6 19.0 B 41.1 0.14 10.3 20.6 C 52.1 0.22 169 25.2 68-689* A 71.9 04)525 15.8 19.5 B 35.2 0.164 10.6 18.2 C 83.4 0.145 17.5 20.C 69-344 A 912.7 0.0075 24.2 26.7 B 631.1 0.0090 14.5 23.3 C 155.6 04)44 13.0 21.3

*A: baie metal, annealed 1 hr at 1180°C; B: weldment, as welded; C: wektroent. annealed 8 hr at 870°C. N74XW pri. 137 shorter than those of the base metal. The minimum and 13.11. The rupture lives show some scatter, but creep rate of the "as welded" specimen was lower than they generally show the expected trend of increasing that of the base metal, but the lower fracture strain of rupture life with increasing carbon content. Alloys 330 the weld caused the rupture life to be reduced and 331 have similar carbon contents, but the rupture considerably. After annealing 8 hi at 870°C, the lives are different at high stresses. This may be due to weldment specimens generally had a higher minimum the higher oxygen content of heat 330 and its influence creep rate than the base metal, a shorter rupture life, on the carbide structure. Alloys 334 and 335 with and a lower strain at fracture. Failure generally oc­ 0.087 and 0.137% C, respectively, have the longest curred in the weld metal on the weldment specimens. rupture lives of the series, and there is no detectable Rupture lives for the base metal varied from 72 to 3912 difference in the two alloys. The minimum creep rates hr for tests at 55,000 psi and 650°C in air. of these same alloys in Fig. 13.11 show a systematic progression of strength with carbon level up to 0.05%. 13.4 CREEP-RUPTURE PROPERTIES OF The data for alloys 329 (0.052% C), 334 (0.087% C), HASTELLOY N MODIFIED WITH and 335 (0.137% C) are described by a single line. Heat NIOBIUM, HAFNIUM, AND TITANIUM 333 (0.049% C) seems weaker than heat 329 (0.052%). All of the alloys are as strong or stronger than standard H.E. McCoy Hastelloy N. The stress-rupture properties of these same alloys Laboratory melts having nominal compositions of after irradiation at 760°C for 1100 hr are shown in Fig. Ni-12% Cr^% Fe-O.2% Mn-0.5% Hf-0.5% Nb- 13.12. Alloys 330 (0.006% C), 331 (0.008% C), and 0.5% Ti and various concentrations of C and Si were 332 (0.014% C) have about equivalent tupture hves, prepared. The detailed analyses of these alloys are given which slightly exceed those of standard air-melted in Table 13.6. The alloys were 24b castings and were Hastelloy N. The other four alloys with carbon levels of fabricated to %-in.-diam rods. They were annealed 1 hr 0.049 to 0.137% seem to have rupture lives that are at 1180°C before testing. Several of the samples were better than those of the lower carbon alloys. The creep irradiated in the ORR at 760°C to a peak thermal strengths (Fig. 13.13) show a similar behavior. All fiuence of 3 X 1020 neutrons/cm3. All of the results alloys have creep strengths above those noted for reported in this section were obtained at a test standard vacuum-melted material. temperature of 650°C. The fracture strains of these alloys after irradiation The first series of alloys had carbon concentrations (Fig. 13.14) are very good. Standard vacuum-melted that ranged from 0.006 to 0.137%. The results of creep material has been observed to have fracture strains cf tests on these alloys at 650°C are shown in Figs. 13.10 only a few tenths of a percent under these irradiation

Table 13.6. Compositions of experimental alloys

Alloy Concentration (%) No Mo Ci Fe Mn Nb Ti Hf Zr C Si N O

330 11.7 7.7 3.2 0.19 0.62 0.47 0.50 <0.01 0.006 0.011 0.0022 0.031 0.048 331 11.7 7.3 3.6 0.15 0.56 0.50 0.46 <0.01 0.008 <0.01 0.0016 0.0034 332 11.8 7.4 3.0 0-15 0.61 0.48 0.44 <0.01 0.014 <0.01 0.0C12 0.0060 329 11.6 7.3 4.1 0.16 0.59 0.48 0.44 <0.0! 0.052 <0.01 0.001? 0.0018 333 11.8 7.2 3.4 0.15 0.62 0.47 0.48

0MML-0W6 7I-I967B

RUPTURE TIME (nr)

F%. 13.10. Strca-raptwe properties at 650°C of alloys mrdified with 0.5% Hf, 0.5% Ti, 0LS% Nb, aad tsofC

and test conditions,5 but the minimum fracture strain carbides and very Uttie matrix nnrcipiiation during noted for these alloys was 5%. There is a marked effect aging. This should result in poor postinadiation proper­ of carbon content at lower creep rates. For alloys with ties, but the data (Fig. 13.15) do not bear this out. Two carbon contents of 0.049% or greater, the lowest factors likely account for these discrepancies. First, the fracture strain is 13%. There is no systematic effect of precipitates that form during aging without a stress may carbon content above 0.049%. be different from those that form in a stressed specimen Three of the alloys contained Si additions. The during testing. Second, irradiation may influence the variation of the rupture lives of these alloys in the type and distribution of precipitate that forms. Both of unirradiated and irradiated conditions is shown in Fig. these factors must be investigated further since nuclear 13.15. Silicon does not seem to have any systematic applications will both stress and irradiate the material. effect on the rupture life in the irradiatei or unirradi­ ated conditions. The fracture strains are quite good for 13.5 CORROSION STUDIES all specimens, and there is no detectable effect of Si. J. W. Koger The mechanical behavior of these alloys is generally what would be expected from the microstructural The success of a molten-salt reactor system is strongly observations made by Gehlbach. However, some dependent on the compatibility of the materials of apparent conflicts exist. For example, aging at 760°C construction with the salts comprising the primary and produced a relatively coarse carbide structure in the secondary circuits of the reactor. higher carbon alloys, whereas the mechanical properties A number of factors contribute to molten-salt corro­ do not show i deterioration at the higher levels. Also, sion. The tendency for a reaction to occur is measured the alloy with 0.44% Si (338) formed coarse M6C-type in terms of the chemical potentials of the reactants and the products. The reaction kinetics will be influenced by factors such as the temperature, pressure, concen­ 5. H. E. McCoy and R. E. Gehlbach, "Influence of Irradiation Temperature on the Creep-Rupture Properties of Hastelloy N," tration, and nobility of the salt constituents, solubility J.Nucl.AppL Technoi 11(1), 45-60 (May 1971). effects, and viscosity of the melts. 139

The experiments discussed in this section are intended 13.5.1 Fuel Salts to assess the mass transfer characteristics of candidate Loop 125S, containing an MSRE-type fuel salt with 1 salt-alloy systems under design parameters based on the mole % ThF and constructed of Hastettoy N, has been Molten-Salt Breeder Reactor. The majority of studies 4 terminated after 80,439 hr (92 years). The loop are conducted in thermal convection and pumoed loops contains insert specimens of standard HasteAoy N and a constructed of HasteUoy N. The salts of interest are LiF HasteUoy N phis 2% Nb alloy. The latter alloy was and BeF based with UF (fuel), ThF (blanket), and 2 4 4 developed for improved weldability and mechanical UF and ThF (fertile-fissile) and a NaBF -NaF mix­ 4 4 4 properties, although similar compositions are now ture (coolant salt). under consideration because of incrc^d resistance to Of the major constituents of HasteUoy N, chromium neutron damage. is much more readily oxidized in fluoride salts than Fe, Ni, or Mo. Accordingly, attack in our systems is This loop was operated as a "life-test" to provide normally manifested by the selective removal of chro­ long-term data on mass transfer in a fluoride salt, air mium from the HasteUoy N. Several oxidizing reactions oxidation of HasteDoy N, and corrosion properties of may occur depending on the salt composition and various weld junctions. We elected to terminate the impurity content, but among the most important experiment after a salt leak was detected under one of the main loop heaters. Prior to the discovery of the reactants causing oxidation are UF4, FeF2, and HF. Because our experimental systems are not isothermal, failure, the amperage to the loop heaters dropped by a temperature gradient mass transfer effects are quite factor of 2. Investigation revealed that half the main important. Conventionally, we observe weight losses in heaters were open and grounded, which suggested the the hotter regions of our loops and weight gains in the presence of salt. After removing the insulation and colder sections. heaters, a small salt leak was found under one of tot Lavite* bushings used to position the loop heaters The status of the themal convection loops in around the hot leg. operation is summarized in Table 13.7. 6. Trade

0MK.-CM6 71 -13877 70 1 *3 ' f / \ 1! 60 ^ \M 4 ON , Am*

50 ft 1 a. o 40 T 8 (A <* 30 ALLOY NO. C CONTENT %

,-4 0 to 10r S K>r 2 K>r» to lO* MINIMUM CREEP RATE (%/hr)

Ffc. 13.11. OeeiKaptwe propertied tfO*C of aloysmodinadw^ efC. 140

7t-««7i 70 "IT 1 1 i 60 SUNQAAOAK * • !| MELTED-x <> < 50 s4 • i • I a TA «MRC>VACU U i 40 —1 JED J v t•» 30 ALUO Y NO C CONTENT (£i 20 • 33i G.008 o 532 0.0*4 | ^ o 329 0.052 10 • 133 OJ049 * 534 0.087 • 535 ao7 1 111 llll I i |__L 10i- l «P i min10i * 10* •O9 104 RUPTURE TMEQv}

1%. 13.12. Ml 3X1«*° rtTiTCAl alon CMM 0.5% Hf, 0.5% Ti, 0.5% Nbi ittofC.

-twe 7f-t3o7» 70 _T

[ 60 pn i * 50 ( > • . 1 1 •. > i -S rANOAR O AIR JED 1 40 STAND* *D VAf UK, '!' • 30 J^^ iM.L0Y N a c CONTEIW T nw 20 • 390 not* 331 0.008 o 332 0.014 o 329 0.052 10 339 t 334 0.061 335 0.137 III llll III llll 1! »• 10° MWIMUM CREEP RATE (%/•»>

PI*. 13.13. Cht^T»ptwtp»f«ti»«lo3MrCor«l»yita»«rt^to«dw«rt«Nw»or3x 103* M*NNU/C»2 at 7*0*C Al

atoyic«it«ta0.4*Hf,OJ%Tlt«dOJ%NbMrfmioo»MOOWiUofC 141

0P*-_-BN6 71-13600 en ! 1 ! Mill! ! . ! ! I j i r " r--jr ALLOY NO. C CONTENT (1 • 330 0.006 " 11 24 _ V 331 0.508 j O 232 0-0<4 h O 329 0.052 • • 333 0.049 * 334 0.087 20 ° 335 U.13' • * i I • 16 "(••*• : O 1

• n 1 -4 .-3 .-2 fOk to fO 10r » CREEP RATE (*/Kr)

Ffc.l3J4. i at §90*C of aaaia iaaaNaal te a < «T1X IfJ2* iwrc

11 mint i ii -STANDARD HASTELL0Y N (UNIRRADIATED)

M u

to1 w* 10* RUPTURE liME (Mr)

Pfe 13.1/i. IIBNHH of of MOM ate atCMTCof (*H)at7*rCtoii .cOxif" i . Nnbcn by tte jwiafs arc the facfant 142

The appearance of the wall near the failure B shown Loop 1258, constructed of type 304L stainless stee', in F%. 13.16. The failure site was at the center of a has operated about eight years with the same sah as %-in.-diam enter whose depth was comparable to the Loop 12SS. The heaters and insulation on this loop thickness of the wall. The crater formed from the were replaced at the same time as for loop 1255, and it outside in, and its location suggests that it was caused continues to operate normally. by catastrophic oxidation of the tube wall associated Loop NCL-16, constructed of Hastefloy N and con­ with the Lavite bushing which surrounded the failure taining removable specimens in each ve tical leg, has area. We have examined metalograpbic samples from operated with MSBR fuel salt (Table 13.7) for over 3.5 various sections of the loop, including the leak site, and, years. The heaviest weight loss after this period is -2.9 except for the %-m.-dJam crater, these samples showed Kg/cm3, and the largest weight gain is +1.7 mg/cm2. only superficial corrosion (<1 mil) on either the outside Assuming uniform loss, the maximum weight loss, is or inside surfaces of the loop. Even surfaces covered by equivalent to 0.04 mil/year. The chromium content of the leaking salt showed hmited oxidation. New beaten the salt has increased 550 ppm, and the iron has and insulation had been placed on the loop after 8.8 decreased about !QQ ppm is 30,000 hr. Titanium- years of operation.7 Based on our inspection of rhe modified HasteOoy N specimens (12% Mo-7% Cr-0.5% loop at that time, we believe that the failure was Ti, bal Ni) in this loop show smaller weight losses than Induced following the heater replacement and that '.t standard HasteOoy N specimens (lt% Mo-7% Cr-5% was not progressive over the life of the loop. Fe, bal Ni) under equivalent conditions. We attribute this difference to the absence of iron in the modified alloy. Principal corrosion reactions acting in this loop 7. J. W. Koajer, MtSR ftoptm Sewiuum. Pnp. Rep. Feb. 28,appea r to be 1971, ORNL-4676, p. 194.

TaMe 13.7. States of MSR ftognm thetawJ ooaveetn a loops tanNajk Aagwt 31, 1971

Salt Max. Operating Loop Loop material Specimens Salt type composition temp. (°o time (mote%) C°C) (hr)

1258 Type304L Type 304L ttainiess Fuel UF-BeF2-ZiF4-UF4 ThF4 688 100 70,583 stainless steel tied*'* (70-23-5-1-1)

NCL-13A HasteBoyN HasteBoyN;THnodified Coolant NaBF4-NaF (92-8, phis 607 125 24.795 HastefloyN controls*'* tritium additions

NCL-14 Hastelloy N THnodified Hasteloy N*»«' Coolant NaBF4-NaF (92-8) 607 150 33370

NCL-15A HasteBoyN Tunodified Hastelloy N; Blanket LiF-BeF,-ThF4 (73-2-25) 677 55 26,632 Hastefloy N controb*c

NCL-16 HasteSoyN Ti-modified Hastelloy N; Fuel LiF-BeF2-UF4 704 170 30,990 KasteUoy N controls*'* (65.5-34.00.5)

NCL-17 Hastelloy N HasteUoy N; Ti-modiiied Coolant NaBF4-NaF (92-8) phis 607 100 19,033 Hastelloy N controls*'* steam additions

NCL-19A Hastelloy N Hasteuoy N; Ti-modified Fertile- LiF-B»F2-ThF4-UF4 704 170 13,419 HasteUoy N controls*** fissile (68-20-11.7-0.3) phis bismuth in molybdenum hot finger

NCL-20 HasteDoyN Hastelloy N; Ti-modified Coolant NaBF4-NaF (92-8) 687 250 14,913 Hastelloy N controls*'*

c NCL-21 Hastelloy N HasteUoy N* MSREfuel LiF-BeF3-ZrF4-UF4 650 110 1,009 (65.4-29.1-5.00.5) 'Hot let only. ^Removable specimens. "Hot and cold legs. 143

material remaining on the wal when the Inst noble 2UF (d) + CKs) ** 2UF (d) • CrF,(d), 4 3 constituent is removed orbydissoaationofaltheaaoy constituents with subsequent pmdpitaticn of the i FeF2(d) + Ci(s) * Fe and i natimmj, the MSKE fuel attack will continue. Such a condition amy arise if the i started and has operated lor cmv 1000 ar. That waDs of the crevice become covered with a very noble loop is ecaapped with < material (nickel or molybdenum). This coveting by a the U^/U** ratio, noble constituent can occur either by the noble of the oxidation potential of the

Y-4O0&91

0 0.5 1.0 L J INCHES

Ha. 13.16. Crottttctmnorhotlef ofloop 1255mowinjivaWMwlM«ela^oefimradaftw 9.2 144

of these probes had been to large systen. This loop differs from our other thermal systems, and tins experiment is to convection loops in that the flow op the hot leg goes possible toe for on-stream i a dkectiy into a large some tank. In our other loops the

more

Ffc> 1X17. Upper portion of Hart** N loft? ) arto which 145 ah is circulated only through tubing which is in a 25 mote % ThF«) proposed for a two-land MSMt harp-shaped configuration. The flow then goes oat the by the change of bottom of this task into a uosauver kg and into the in the alt, has been very cold kg. The different design of the vpper portion of exposed to tins alt have a "gaee" or the loop was dictated by the fact that we wanted the (probably a hsjh iw Hag ihnraa cnaf nmd) ekxtrocliea«calprobestoseeafairTyhu^andcahnsak that is hnpowlne to remove withont nangag the The eiectrochenncal probes pass through aetaL However, nnnalognpinc studies show Ittte, if fittings (separated from the metal by Teflon), which are on risers 10 in. from the sage tank (to protect the Teflon from the heat of the salt) and then enter the sah a the huge hot-teg sage tank. There 13SA are five accent ports for the probes. Loops NCH3A and NCL-14, The specimens from the loop were iciuoved, weighed, • •••-• -—— mi m azS l ISBPSgry 7t 3Blrl S after 665-hr exposure. Weight tees?an d each teg, haw operated for 1% expected in a teapciatnie gradient KUHB tivety, with the ystem, were seen in the hot and cold teg lcapeUively. The laiiaani we%ht tees in the hot teg %)- reaoval) at the was 0.1 ag/ca3 and the maximum weight gam in the 2 0.7 cold teg was OJOS am/cm . As expected, the V7U** ratio jncrearo with time, and we a? with oar weight-change data. After father steps wil involve additions of W,(d)+Ce(s)*CrF,(d)+ Fe(s), to stawy their i

Details on the ls*7U*' ratio a monitored by the probes are disiuard in the Analytical Chr aiiliy a of this report.

2lll*d)+)fl(s)~IM0 + lftTa(«). 133.2

A fe*tile4ajne USER sah ha ckcaated for over d, s, ami g refer to 13,400 hr in Hasteloy N loop NCL-I9A, which ha solid, aMl gas, respectively, aal M*Cr, Fe,Fvj,antHo. removable IT wane cs in each teg. The test ha two purposes: (I) to confain tlwcompatjbfflity of Hasteloy bal valves which ate located above the aaje tana. N with the salt and (2) u> determme if bismuth wil be These valves are exposed toa nuxture of He and BFi. picked up by the ah and carried through the loop. The eaandnottosah.Weattiftoutheleaksbothtonea^ bismuth is contained in a aoiybdenom veael located in use of the bal valves and to coiiosion induced by ay an appendage beneath the hot teg of the loop. A warning air mfcakage into the ga mixture. Although the overal uniform km, the fmxnmun weyht loan equivalent to corrosion rate in thea loon is not exceafve. the rata 0J024 mil/year. A modified Harefloy N ahoy (Ni-12% observed in the absence of ban valve teaks lave been an Mo-7% Cr-0.1% Fe-0.4% Ti-2JO% Nb) ha test tea order of -r|r—''t lower dan the avenge rale, la weight thai a standard ahoy at the same position. The NCL-14, ever the test445 0 hr, the i chromium content of the sah has increased 134 ppm m rate ha been 0J aaVyea. Figure 13.18 7400 hr, and there is no detectable bismuth in the sah. changes from iptchaiai in NCV13A a function of The corrosion reactions were diiciif d in the NCL-16 poajtioa in the loop (teaperatnre) aad tint. Note the areas of weight gaa ami wehjfct tea and the bateace points where no mta tnasfa occurs. 13JJ Loop NCH7, conatrocted of triad awl Hasteloy N and contahung tcmovabk speUmea in each kg, is Loop h* VISA, constructed of stamlard HateSoy N being used to determine the effect of steam ou the ant awi conteatring removabk specimens m ««.ch teg, ha transfer chatactethtics &f the fluoroboratesal * aixture. operated three yean with a blanket alt (UF-BeFj with After 1000 hr of aooael operation, sfnm was isajtcted 146

10 2090409060700090 wo OBXANCE FROM HOTTEST PORTION OF THE UPPER CROSSOVER («.) 4- H- -M- UPPER COLO LEG BEND LOVER HOT LE6 (VERTICAL) CROSSOVER (VERTICAL)

1S.II to NriUVNaF (92-8 matt » CRMB NCL-13A «a fi

into the salt • and the loop has now operated 18J00O hr 10,178 hr because of a leak in the cover gas system; foiowing that injection. Figure 13.19 shows specimen however, the overall mass transfer rate decreased weight change as a function of position in the loop steadily between these two events. (temperature) and time. Note the large increase in Loop NCL-20, constructed of standard HasteDo> N weight change during the first 239 hr after steam and containing removable specimens in each leg, has injection. Another abrupt weight change occurred at operated for over 14,900 hr with the fhioroborate coolant salt at the most extreme temperature condi­ tions considered (687°C max and 438°C min) for the t. J. W. Kopr,MSRhvpmmSemkimm. Progr. Rep. Aug. 31,MSB R secondary circuit. Forced air cooling of the cold /P7V,ORNL4622.p.l70. leg is required to obtain this AT. After 11,900 hr, the 147

0NML-0M6 7l-«OfO 30 1 1 1 1 [— HEATEO AND WSULAT EO—-] 1

20 ^A

<0 / ( \M^

-10 600 o

E *= ssoS •S -20 3

^^ ^ § -30 < •"I X o 450 •- THE* •ML CO HVECTIC N LOOP MCL-17 Sv o \

-50 • 239 hr • o 424 hr * 663 hr 1474 hr -60 * TME AFTER 2888 hr STEAM MJECTO N 4756 hr o 6030 hr m 9006 hr -70 t 10,178 hr • 1054 hr BEFORE STEAM

-80

-90 I0 20 304O5060 70 809O too DISTANCE FROM HOTTEST NOTION OF THE UPPE* CROSSOVER (in.) K \ H Hh -I UP-£R COLO LEG BEND LOWER BEND HOT LEG CROSSOVER [VERTICAL) CROSSOVER (VERTICAL)

1'%. 13.19. We^t froa Hastefloy N of NCL-17 [N*BF4-NaF (92-8 mole %) Jt .)«« fane* lorn of position and

ma * mum weight loss in the hot leg was measured to be Figure 1322 shows micrographs of specimens in the 6.T tiig/cm2 (0.2 mil/year assuming uniform loss) and hottest and coldest positions of the loops after wji accompanied by a maximum gain in the cold leg of 11,900-hr exposure. Microprobe analysis9 of these 42.8 mg/cm2. Figure 13.20 shows the weight changes specimens showed no detectable concentration gradi­ of specimens in the loop as a function of time and ents. The deposit on the surface of the cold specinens temperature, and Fig. 1321 shows the overall picture was rich in Fe (>25 wt %) and Ni (>64 wt %), but of the mass transfer in the system. The chromium showed very little Cr or Mo. content of the salt increased by ISO ppm. Up to 11,900 Following 12,400 hr of operation, the normal 20-psia hr the weight changes of the specimens and the loop overpressure dropped to atmospheric pressure. chemistry changes of the salt indicated that the mass Investigation disclosed that the safety valve on the transfer was the lowest yet attained with the fluoro- borate mixture in a temperature gradient system and

also confirmed the importance of salt purity on 9. Performed by H. Mateer, T. J. Henson, and R. S. Crowe of compatibility with structural material and on operation. the Metals and Ceramics Division. .'48

0W*.-*3*r, *-«OV» A salt analysis did not disclose any gross changes. The valve was replaced, and loop operation continued. V t'* During the next !850 hr. the maximum corrosior rate (assuming uniform loss) was 0.7 mil/year. Pari of this increased mass transfer was probably associated with the regulato. problem, but further inspection disclosed a leaking mechanical pressure fitting. This was repaired, and the loop is continuing operation.

~K An experiment was started to evaluate the corrosion y,ooo properties of eight brazed Hasteiloy N specimens in ?i*R Of G**«AT

wen-wet

1O20304O5O6O70809O10O DISTANCE FROM HOTTfJT PCCTION OF THE UPPER CROSSOVER (in.) H UPPER COLO LEG 9EN0 LOWER SENO HOT LEG CROSSOVER (VERTICAL) CROSSOVER 'VERTICAL)

Fig. 13.21. Weftjht cl from HMtflOov N tpedimm in NCL-20 exposed to NaBF4-NtF (92-8 mole %) as & function of pofttioa mi time. 149

-107939 ^

8

kJ X O X o o

s 8 6

Fig. 13.22. Oi*kal nBcrogcaiAs of IfcsteOc^N specimens from 685°C, weight loss 6.2 mg/cm2, etched with glyceria regia; (b) 460°C, weight gain 2.8 mg/cm3, as polished. ISO oxidizing conditions produced by the air inleatege. 13.7 FORCEIVCONVECTION LOOP Over ihe 3000-hr run the iron content of the iait has CORROSION STUDIES de.kC£j»ed 100 ppm while the chromium, nickel, and W. R. Huntley J. W. Koger H. C. Savage molybdenum content has remained unchanged. The above observations suggest that the corrosion Forced-convecJion loop MSR-FCL-1 was rebuilt fol­ reaction taking place is of the type lowing cverhe^tinv,13 and the loop is being used to evaluate the compatibility of standard Hastelloy N with

NaBF4-NaF (92-8 mole %) coolant salt at temperatures FeF2(d) + 2CrF2(d) •+ 2CrF3(d) + Fe(s), similar to those expected in the MSBR secondary circuit. The ioop designation has been changed from which would produce no measurable changes in the MSR-FCL-1 to MSR-FCL-1 A because of changes in the chromium concentration of the salt, but would account equipment and in the operating parameters. The new for a decrease in the iron concentration. velocity in the %-UL-OD. 0.042-in.-wall tubing is nominally S% fps. The maximum and minimum salt temperatures in the loop are 620 and 454°C respec­ 13.6 ANALYSIS OF HIGH-LEVEL PROBE tively. Hastelloy N corrosion tesi specimens are exposed FROM SUMP TANK OF PKP-1 to circulating salt at 620,548, and 454°C. A second forced-circulation loop of improved design, J. W. Koger MSF-FCL-2, has complete i shakedown tests and is in operation. This loop will be used to study the corrosion Loop PKP-1 was operated by A. N. Smith for over a and mass transfer of standard HasteLoy N in sodium year to test a molten-salt pump with the coolant fluoroborate coolant at typical MSBR sal- tempera­

mixture NaBF4-NaF (92-8 mole %). We had previously tures. A new pump design for MSR-FCL-2 provides salt 1 examined the BF3 feed and salt level bubbler tube ° velocities up to 20 fps. The loop contains three sets of and were asked to examine the spark plug probe removable corrosion specimens which are exposed to because of its unexpected discoloration. salt at 620, 537,454°C and salt velocities of 10 and 20 The spark plug probe consisted of a '4-in.-diam fps. electrode which was installed April 8, 1968 and was assumed to be Hastelloy N. However, metaCographic 13.7.1 OpmtioaofFofced-Convectioa examination of the rod disclosed cracks extending 5 Loop MSR-FCL-1 A mils into the metal. Spectrographic analysis revealed that t'l* material was Haynes alloy No. 25 (50% We completed loop repairs and piaced the loop in Co-20% Cr -10% W-10% Ni-3% Fe). operation at simulated MSBR conditions on Aug. 16, This parallels a finding in 1968 in which the specimen 1971. The test has operated smoothly since that time support rods of thermal convection loops NCL-13 and and has accumulated 380 hr at design conditions as of -14 were found to be Haynes alloy No. 25 rather than Aug. 31,1971. Hastelloy N." That investigation revealed that the During the repair period, modifications were made to source of the %-in. rod was a nuadentified storage the control system to prevent accidental overheating of carton, and we are assuming that the rod found in the the loop piping. About 25 ft of HasteOoy N loop tubing PKP loop was from the same source. was replaced, and new corrosion specimens were in­ It was shown in the thermal convection loop tests stalled. The specimen assembly was modified so that that the Haynes alloy No. 25 was attacked much more specimens could be clipped rather than tack welded than the HasteOoy N. In the case of the PKP-1 loop, the into the assembly. The 27-ft-tong cooler coil was undamaged and was reused. The NaBF -NaF (92-8 spark plug probe comprised an infinitesimal fraction of 4 the loop surface, a fact that would explain the much mole %) coolant, salt was removed from the dump tank heavier attack compared with Hastelloy N. and cooler coil by water flushing. This salt had been in the system for the entire period of operation preceding overheating (10,335 hr at design conditions). In view of 10. J. W. Kofn, MSR Program SemUmm. Progr. Rep. Feb. 28, J971, ORNL4676, pp. 211-15. 11. J. W. Kofer and A. i. Litman, MSR Program Semumm. 12. J. W. Kofer et at., MSR Program Sermmnu. Progr. Rep. Prop. Rep. Aug. 31,1968, ORNL4344, pp. 264-66. Feb. 28,1971, ORNL-4676, p. 202. 151 the changes in corrosion specimens and operating was filled with s specially processed sodium fhioro- conditions, the loop designation was changed to MSR- borate salt charge, placed in operation, and heat FCL-1A. transfer performance of the salt was measured. After a The LFB pump was disassembled and repaired prior short period of hot operation an Oring seal failure in to reinstallation in MSR-CFL-1 A, and new bearings and the ALPHA pump required a loop shutdown. The seal mechanical face seals were installed as is customary. failure was repaired and the test returned to design The pump was operated at 3000 rpm in a cold conditions. This loop, constructed of HasteDoy N, wifl shakedown for about 24 hr to ensure that the bearings be used to study the corrosion and mass transfer and seals were operating properly. An oil leakage rate of properties of HasteBoy N in fluoroborate-type conhnt* about 4 cc/day was observed from the internal mechan­ salt systems at conditions proposed for the MSBR. ical seal and was considered acceptable. The LFB pump Preoperational checkout was completed in acoocdince operates at 3000 rpm in MSR-FCL-1 A. which is slower with the operating manual, and aB documentation **s than the 5000 rpm previously used in MSR-FCL-1. It is reviewed for compliance with the QaaSty Auaraact hoped that this reduced speed will appreciably increase Plan (Engineering Document Q-;05664tB40l-5<0). Al the reliability and service life of the bearings and recorders and indicators of temperature, pressure, and rotating seals. power input were canorated. Heat loss iiwiaiuimini The piping system was filled with S10°C salt from the were made on heater No. 2 in preparation for deter­ dump tank on Aug. 12, 1971. The salt was circulated mining the heat transfer performance of the sah. jsothermally at 540°C for 90 hr at a flow rate of about The salt charge for MSR-FCL-2 was processed to 0.8 gpm during final system checkout. The flow rate improve its purity prior to transfer into the loop. The was then increased to the design value of 2.4 gpm first routine processing was done after 25 kg of the salt (pump speed 3000 rpm) for an additional 4 hr at components was mixed and sealed in i vesseL The intermediate temperatures prior to reaching design mixed powders were heated to 149*C and evacuated conditions on Aug. 16, 1971. The power input to the with a mfchanical vacuum pump for 45 hr to remove loop at design conditions is 63 kW. This power level moisture. The sah was then heated to 500°C and 16.7 represents a practical upper limit for long-term opera- kg was transferred to a smal fittng pot. The salt in the tics of the power input system because of hearing nwug pot was heated under seale4-off vacuum to check limitations of the saturable reactor. for further impurity outamwJng. The pressure rose from 28.7 in. Hg vacuum at 149*C to 264 in. Hg at 470*0 13.7.2 Mrlanmgii al flnalyiai of Tutud CoaMction which indicated little nulgining above the expected Loop MSR-FCL-1 A BF) vapor pressure of the salt. Aaeounferiawamfetnte of He-BF, was bubbled through the salt at 480*C at A salt sample was taken from the pump bowl on Aug. about 100 cc/mm for 60 hr, and the effluent gas was 16, 1971, after circulating the salt isothermaty for 90 passed through a cold trapat0°C. This test was run to hr at 540°C. This initial salt analysis disclosed relatively check for impurity conecnons such as were noted large amounts of chromium, iron, moryboVruun, and firing operation of a liquid level tubbier in the PKP hydrogen. However, a later sample taken from the 14 loop. The inlet gas mixture was prepared for the pump bowl at 454°C, after the loop had operated 138 experiment by mixing dried hefium (<1 ppa H»0) hr at design conditions, showed smaller amounts of with BF, in the proper ratio to balance the vapor impurities. If any of the impurities were at saturation, pressure of the hot salt. the difference in temperature at which the samples were taken could explain the apparent discrepancy. Impurities were found in the gas mixture after it had bubbled through the sah. A gas rotameter downstream of the cold trap MfttiaBy became fouled with a dear 13.73 Operation of Forced-Conncuon liquid. A white film abo deposited on the wals of the Loop MSR-FCL-2 glass cold trap. A total of 0.15 cc of brown liquid was Assembly and preoperational checkout of the second collected in the trap after 60 hr. and the materiali molten-salt forced-convection loop MSR-FCL-2 (ref. collected appeared similar to those noted by A. N. 14 13) were completed during this report period. The loop South during operation of the PKP loop. Anarysai

13. W. R. HwMley ct at., MSR hpogjwm Stmkpum. Hop. 14. A. N. Santa et at., Jfgft frajmm Stmimtm. troy. Rep. Rep. Aug. 31.1970, ORNL-4622, pp. 176-78. Feb. 28.1969. ORNL439*. pp. 102-10$. 1S2

was inconcaiaive as it only disclosed major quantities of

Na, B, and F «ith ppm values for many other elements. -_i ^~—4 * * i *•*» These instances of impurity coflection show that presently available sodhim fluoroborate systems can be o«T<**(af-: expected to give acid colection am* fouling problems when devices such as liquid level bubblers are used. HCATCD scene* uo iuno * ss< From the small amount of material collected, we concluded that our method was not practical for renwvinglaisjeanwunuofimpvntie^Hov^Yer.wefjel that improvement* could be made on the basic process which could provide more efficient removal. The heat transfer performance of NafiF«-NaF (92-8 mole %) coolant sah was measured in heater section No. 2 of MSR-FCL-2 durin* hot shakedown operations. Heat transfer data were obtained at Reynolds moduli from 4200 to 48,000, sah velocities from 125 to 10.6 fps, heat fluxes from43,000 to I57JOOOBtu hT1 ft"4. 1 1 1 fvj.l3J3. Neat rUii coefficients from 230 to 2100 Btuhf- ft" 'F" . ofNBBF4-NaF. 14W-3S the writer; therefore, the data of Fig. 13.23 are ant). considered the best avattabk evidence that sodium 14. W. R. HmtOty. MSJt hopmm Stratum. Frvgr. Rtp. Feb. 28.1969. ORNL4M9. p. 2S< 1S3

13.T.4 Mctannsgscal Aaaryan of r otcecrConvcction believed that these failures «ere caused by either flaws LoopMSR-FCL-2 in the specimens, poor rnactriiung of the cage section, or inaccuracies in measuring the wall thickness of the Corrosion test specimens were in the loop white the specimens. Later evidence indicates thtt was not the heat transfer measurements \ -,:e made. These speci­ case. Figure 13.24 is a photograph of these doubte- mens were examined after salt exposure of 510 hr and waued tube burst specimens, with the outer tube salt circulation with the ALPHA pomp for 56 of those removed. hours. During the neat transfer imamw merits the pump The 77,000-pn specimen railed catastropruc*Sy, but operated at speeds between 1400 and 5400 rpm, and the 52,500-psi specanea developed a smal crack tne specnueas were cxpoaco to lethpetatuies Detween surfing at the tip of the snov shown at the right of the 440and620t. photograph. Even though the specimens rated in a The weight changes were higher than expected (maxi- short time, they were not removed from the fariairy 2 tmm weight tost of 1^ nnV<» ) and showed a definite until 1000 hr, so the outside of the inner tube waa velocity effect. The speefcoens *xh»Sted expected exposed to steam for about the same time as the tenipefatttre«g?adient mess transfer behavior with outside of the outer tubes shown at the top of the weigh; loasts in the hjgh^enmeranue region, very little photograph. cnange in tne rneoxiroHcrnpc* acute region, ana wenjnt These two Caned specanem were replaced by speci­ fain in the cold region. mens stressed at SoJDOO psi (OJOU in. waB) and 50,000 Donna the time of the heat transfer nwanjifments, psi (OJOI6 in. wal)- These stresses bracket the lower the chfonsjum in trie sah mcreasedfrora64to82ppm, stress of the ruled spetieaeas (52400), and these and the iron changed from 359 to 347 ppm. The oxide iepsacenifnt spacaueas have been in test over 1000 hr content varied from 500 to 800 ppm, and the H* wxthoert taBase, novating the other tuecimeni had content increased from 27 to 31 ppm. Mass tnarfer was Caned pseacstsiely. These latter spechnens were not comicVred excessive, and the decision was made to machined casefuly and had a rupfriot surface finish go to design conditions. and appear to have uniform wal thidmeasea. Figure 13-25 is a photoaakrogTaph of the area of ISM COUtOSHXiOFHASnUOrtiWSTEAM Csnure of the 52^00** tube bant. It appears that B.McNaHb H.E. McCoy suess cononon craexsag am occurred win tan COCKS starting on the ID (steam sine) of the tube. Since the The awdnlcations to the sample dnanber at Bnl Run other tubes stressed hi the sssne range as this one hew to accommodate tube bunt tests nes been completed not rafted, it raises the poaaMty tiattsonaetbmg could and the teat faemty placed hack in operation. Some of nave nappenen to rnBBaaivasamspecaBen.ESm^aoaae Ula? wttHuCnVOS ^PBuavK Wmttk SBGCmnYJNV auuW'w' atCCQflMMastCQ contsuaaaant was left in the tube foflowiag tabricalion 8000-hr exposure and ate stBJ foutoiag the same trends due to poor deanang practice or soaae i nal sminanl vras reponeu picviousty. ine tisnfnoy n amcaneus, mtroduced by the steam daring operation. An msesd; both air and vacuum melted, have total weight gams ot gatwn h under way to check water ousMty records about 0.4 mg/cm3 at 538*C. The same heats of during the run to determine if any unusual -ronfltions Hastefloy N expnaed to steam at S93*C in the Florida existed daring the run. The plant had been n» a period steam plant for approximately I5J0OO hr have weight of sustained operation for over one month before the gains of about 33 sag/an3. first specimens were insrrteU. Two of the Hasficoy N tube burst soeewnem instated ihemuinarv results from studies bv Hanunond at in the Bui Run fadfcty fried pYtnamuery. The highest Daaeam. Fhu atound that Hasteaov N raav be susceo- stressed (77,000 ori, OJOIO in. waU thkknest) ipf churn tMe to stress conoaioa crackaat in steam eoaamnaaa faded m 1 hr.and the e^hajbest streased (52,500 pat w^wri^v 9^r ^^iw^^v^ vvNvspvn vsaninpnut ••» npj^*avunv> ^pap*B>vmnvjmmumt todhes fW«wfd? SSM unygca. Some of the test con­ 0J015 in. wall thicka«) taflad *a 3.7 hr. These speci­ ditions actuary deposited Mad on oat aHserial. H. W. mens were stressed rnaatrtiiahly above the yield stress IVkering, F. H. Beck, and M. G. Fontana proposed a at53S%(40jOWpa%asdyfeldauja4^ dun-watted tisbe to prods, "a rapturequickly . It was fkst It. H W. Hdnwiag. P. H.ltfc. ani HC.Fuell• i, "BaaM UiiHimrim Oaajsnoa of 1M Sniat— Saamay Oxymnani 17. I. McHnm ani H. E. McCoy. MM An*** Smtmiu. Dry Saeanu auod*>> at Etsvatsi Taausfstaaii," Ihwn. ASM *ujr. Rtp. Ftb. 23.1971. OftNl/4t7*. pp. 2l#-27. sMn-mj (mi). 154

Y-108427 I l I • I INCHES

HASTELLOY N TUBE BURST SPECIMEN HASTELLOY N TUBE BURST SPECIMEN FAILED IN 1.0 hr IN STEAM AT 77.000 psi FAILED IN 3.7 hr IN STEAM AT 52,500 psi

Fh> 1X24. Hasseftqr N take it—owed from the Bal Km Steam Rant after failure. The small tube in the test section was exposed to steam Mt 538°C and 3500 psi.

Ffcv 1125. tkotomkmjark of Ifcstdtoy N tube bent Failure occurred after exposure to steam for 3.7 hr at 52,500 psi at 538*C. Steam was on the inside of the tube. 155 mechanism for rapid intergranular deterioration of specimen had about two times the rupture Hfe of the austenitic stainless steels by oxygen and dry NaCl that coated specimen and a slightly lower creep rate. Figure may be pertinent to these observations. This mechanism 13.27 is a plot of the percent elongation vs tone for was based on the fornvtion of a nonprotective scale heat 2477 in die uncoated and coated conditions at containing NaCr04 from the reaction of NaCl and 02 593°C and 60,000 psi in air. The fust two specimens with Cr203 and CT73C6, with reaction rates increasing designated anneal 000 had a mill anneal of 1 hr at in the order listed. Since Hastelloy N contains 7% 1177°C prior to rnachining, and the third specimen had chromium, it was decided to test it in contact with an additional anneal of 1 hr at 1177°C after margining NaCl at 593°C. An air-melted heat (S06S) with 163% but prior to testing. Mo, 12% Cr, 3.9% Fe, 035% Mn, 0.6% Si, and 0.065% It appears that there is little effect of th* NaCl on the C and a vacuum-melted heat (2477) with 163% Mo, 7% creep strength of HasteBoy N at these conditions, but Cr, 4.1% Fe, 0.05% Mn, 0.05% Si, and 0.06% C were further testing will be required to determine the tested in air at 60,000 psi and 593°C in the uncoated magnitude of the effect at various stresses. The reason and coated conditions. Rod specimens having gage for the difference in creep strengths of heats 5065 and sections 1.125 in. long X 0.125 in. diam were used for 2477 is not presently understood, since at higher these creep tests. The specimens were annealed 1 hr at temperatures, such as 650 and 760°C, the strengths are 1177°C in argon prior to testing. The NaCl was applied quite dose. to the specimens by painting a saturated NaCl solution Figure 13.28 fc a photomicrograph of the rupture of on a %-in. length of the gage section and allowing it to uncoated heat 5065 after testing at S93°C and 60,000 dry before installing in the furnace. The coatings wtre psi in air. Figure 1329 is a photomiaogiaph of the typically about 5 mils thick before testing. rupture of heat 5065 coated with NaCl and tested at Figure 1326 shows a plot of the percent elougatiott 593°C and 60,000 psi in air. A comparison of these vs time for heat 5065 at 593°C and 60,000 psi in air fcr photorncrographs reveals very Mute if any difference the uncoated and coated specimens. The uncoated due to the presence of the NaCL Figure 1330 is a photomicrograph of the rupture of uncoated heat 2477 after testing at 593°C and 60,000 0RNL-CWG 71-13682 psi in air. Figure 1331 is a prxrtoincrogrsph of the 1 1 ! rupture of heat 2477 coated with NaCl and tested !• ! • 225 , 1 . • under the same conditions. A cofnparison of these i i photomicrographs and the rupture fives of these tests i 20.0 (4683 hr without and 475.9 hr with salt) shows NaCl 5 i has little if any effect on vacuum-melted Hasteloy N at I these conditions. 175 1 i i i i 1 * 15.0 1 j w z —i—i—i—i—i—r T o o TEST AS RECEIVED 5 125 12 * TEST AS RECEIVED WITH SALT * © 1 • TEST ANNEALED (tar AT 1177X WITH SALT oz ! i 10 J KXO i i , o om:OATE O l A CO "-TED WITH NoCI z 8 7.5 1i o ! 5.0 i -I t u 4

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133 EVAIXATtONOFDUrLEXTUBOTG temperature the Ni 280 and the Incoloy 800 contribute FOR USE IN STEAM GENERATORS equally to the strength in the (ensue test. A tube burst specimen was tested at 538*€ m an B.KcNabb H.E. McCoy argon atmosphere with argon internal pressure and Duplex tubing has been proposed for steam generator ruptuicd in 3263 hr. Calcinating the stress on the entae service with Incotoy 800 on the inside (steam side) and duplex wal thickness aamming 0J065 in. each for the nickel 280 (pure nickel with OJ0S%AISO, for gram are Incoloy 800 and Ni 280 would give a hoop stress of oontroO on the outside or salt side. A piece of the loco 28.720 pa. The hoop stress in the Incoloy 800. duplex tubing reported previously1' was fartherevalu ­ aawna^tneNi280dJdnotaddam/streatth/«o«)dbe ated by mechanics! property tests. A 12-in. piece of the 46,000 psi. The nip tore life of 3263 hr for a stress of 0.750«L-diam tubing was tensile tested in a Baldwin 46,000 psi at 538*C is in good afreemem with the data Teosfle Machine at 25°C and a displacement rate of in Buleun T-40 (!nco) for Incoloy 800. Therefore, it 0.05 injuria. The 02% offset yield stress was 37,600 appears that the nickel costtfeuted very little to the paU the ultimate tensile stress was 70,780 pti, and the strength at this temperature. elongation 505% in 2 in. It appears that at room Figure 1332 is a photograph of the tube burst specimen with Incofoy 80O end plugs and nfckej rings welded to the tube to reinforce the end closures. Inco 19. H. E. McCoy asd B. McNal*. JOft 82T weld wire and CTA welding were used to snake the Jrojr. Rep Amg. 31,1970. ORNL4622, pp. 181 -83 dtntimilar metal wetts. Dye penetrant was applied to 157

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the fact asctioa of the tebe,aad thai n thae for a pat of thest tested hi the cracks to the aJcfcd 280 cnbt ssea dearly hi the coadttton. It appears that the toaajtaalaal fiajare. Fjaaae 1333 is a photoaajciofiaph of the Ml 280 alahtlv stroaatr. wan a loaatr raatare He tubtaf showbaj tk» •««•* «*i ••»** of theoacUaghi a^BBapvaajv wwa)wv^nwa>wy ^^atvaw •» •^pwnaw*w swarawaw aw the osier portioa of the dvplex tabe. Ffcjare 1334 ita creep rate. However, the fleetest photoHdcvofraph of the nsptore area with the crack hi > a*jav aa^a^av •ejsw^Bj^sjBBjejnwBw The lajoaoaad aae for IIK tahasewoafd have • a)wa> swaj^pw^^en^ai waaaa* ww v>nvar waa^neesnnk w^p^aaaa aajaiw> the Hi 280 oater tube. The lacoloy 800 vat not the taste* (lacotoy 800 safe), bat it cracked stowed the drcaaafercacc at was the Ni 280, to kaow if Ni 280 woasd be ccaawatMe wKhtte aad the interface between the two materiali was the eaeat of a leak. Soast specaevae of Ni 280 were exposed to 3500 pa) steam at 53h*C hi the The letting wet aaadc by coextradiae, the two Ran fadhty for 2000 hr. The spechaeas aasea materiali into a tabe she! aad tbea drawhsj iato tabhw. 75 sne/car* m this period aad appear to be Siiwe tiki tobe bant wieciaaM was nioraeehf cracked *awaan*w HI« %m^^9 ¥vie« anjn^^aaawa>wa ^vw#w p^a^^wwjwwww %«wM*av^^B> ccsaplsmy oxJdtaed m showa hi Ffc. 1336. tQaajRveaaaey, u was laoBgnt iaai prior worneaj flaky oxide was cast/ leawned, aad the dirffthm aaeht haw iaalaeacod the crackiae behavior. heart oiids wsi sadly biufcsa hi laaadhas; thi Spechneas from soset Ni 280 sheet aheady oa head The thJckaess of the were cat lowjitudhial aad tiaawem to the roBMg of the low density of the oxide dfeectioa aad creep tested at 538*C aad 20,000 pal n that Ni 280 is aot ccaaaatibfe with arooa. Ffcjare 1335 is a ok* of the percent etnaaation 1S8

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Y- 106620

0.5 1.0 J_L J INCHES

R*. 13.32, Specimen of daplex bcoloy 800-Nt 280tabing totted at 538*C and 46,000 p*i hoop streatfa th e specimen failed in 3263 hr with 2.3% diametral strain. The longitudinal markings are dus to dye penetrant dnt was• fc • || all • it m • Aa aoeorocQ oy ne 160

Y- 106954

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R*MJ6. oTN i fat Htm fera t 53TC «i 3500 pat. 14. Support for Chemical Processing

J.R.DiStefaoo H.E. McCoy

Reducthe-exttsctkM reprocessing hat be«n proposed OD); gsr aft purarn; fiecar vahe; and %-*MX) X as a method of lernoving protactinium and nation 0j020*n.-wal, %-nu-OD X J.025-in.-waa\ %+LJOD X products from an MSBR fuel. The protest involves QX130-«L-wan\ and \-kt

14.1 COWTRUCTlONOFAl^LYBIiemM vfo have contparieU anunar/ fabticatioa of bat head UDUCTfVE€XTRACTION 75BT CTAND note. eaJarasd end sections of the colunai. and the J. I Dtttefeo We art constructing a njofjfteteiui* system that wig 1. W. P. gtaaWny C L. fa^tenen.aadl^aVVsHgaef a be used for nartaaHnuical and cJuuaJcal eageaw^fcic ivatuarton. DstoMi of the dsslgn of thte test stss>*. have fstnaillie ieataaenV* MR Itapan Jnafnam Avajr. Ana, bean leuufted elatwhsst. *^ smncnay, it nonjSals of s 2. B. L. isnnewan, Xeenasajel Dengs ant Deiahujenu* S-IMoag I VhU» pnekod cotamn vrttai**yd(3\ ftegnaa far am MsvjMeasmsbeusatoa^^ new* *™m*J wnffP enaMP va^ar#vHMH wr^vVs^penWn »"JP*™JI ^PuPfJg) \w *gp ••*• Ti*mc*r OKHL&WI Cfca> I, f fflV

1*3 164 column itself. Loop components for subassembly fabri­ and the %-m.-OD tubing to 300°C before they became cation are presently being machined. ductile. We traced the behavior of the %-in.OD tubing Evaluation of three sizes of commercially obtained to a brittle layer on the ID as indicated in Table 14J. molybdenum tubing (% in. OD X 0.020 in. wal, % in. Removal of 0.004 in. fiom the ID (0.002 in. from the OD X 0.025 in. wafl, and ^ in. OD X 0.030 in. wall) wall thickness) resulted in lowering the tenperature at has revealed differences in hardness, recrystaUuation which ductihty was observed from 300 to 125°C; when behavior, and ductility. Table 14.1 shows the variation 0.006 in. was removed from the ID the material was in hardness and mkrostructure that occurred as a ductile at room temperature. Chemical analysis in­ function ofheat treatment. The data for the \-in.-OD dicated dan material from near die ID of this tubing tubing mdicaled it was partially recrystaftzed in A* containwi higher oxygen and carbon concentrations as-received condition, and heating to 925°C resulted in compared with bulk sample analyses. We suspect that complete reoyuattaiiion. Contreriry, both the V and conUrnkntioo of the tubing occurred during fabri­ n'in.-OD samples were received m a cold-worked cation; inadequate leaning procedures, perhaps du* to coadHson. Heat treating to 925°C (hd not alter the the difficulty of getting a pickling solution into the hardness or microstructure of the %-in.-OD tubing, but relatively small diameter opening, resulted in a brittle the V,-in -OD sample softened and was almost com- zone near the ID. To determine if f£ contamination pktdy recrystaOzed. might also be responsible for the brittle behavior of the To evaluate the ductility of the tubing as t function %-in.-OD tubing, we removed (by etching) 0.001 to of temperature, we devised a somewhat qualitative test 0.002 in. fromth e inside. Subsequent tests then showed in which a ring sample was impact squashed a pre­ good ductility at room temperature for this materia! determined amount. In these tests the ring becomes abo. etiptkM, and we have defined the amount of defor­ The fabrication schedule used in nuLing the %- mation in tenm of a duplaceineat(ongM)aI ring dian- •vOD tubing could also have contributed to its lack of ttunof an dtam of dtpee) divided by the original ductility. We noted that the %-m.-OD tubing com­ ammeter at the ring. The data obtained have b»\,n pletely recrystamzed when it was heated for 1 hr at summarized m Table 14.2. Note that tnc %-m.-OD 925°C. Since lecrystalization temperature is a function tubing was "dnctaV* (no cracks) at room temperature of the prior history of the material, we felt the wSie, under the conditions of dieee tests we were fabrication schedule merited mvestsfltkm. Additional required to heat the %-m.-OD tobmg to 150 to 250°C %-tn.-OD tubing made by a different schedule was

Tab* 14.1. Ha ^o^**^^ waraacwMcflMi

Stool" ... naMnj Coodttlon DPH(lOOOt) IlicnMtractiae (ODia.)

% ASMOMWd* 237 Cold worked % 1 tar« t WC 258 Cold worked % llv&t925*C 250 CoM worked % At MQdvsd^ 200 PctfcJfrracrystalbed (10-15% ) % 1tar »t acre 243 larnagy ifjcryitiBiwd V lbrttMTC 16$ CoawAetety leciyrtamatd % Aswcahee* 242 CoM worked % ItaratWC 255 Cold worked % lhratgOirc 243 Cold worked % lhvat«00*C 234 vary anjtniy ncsyvjmumt % ItarntWrC 206 Afenost ceundetely ncrystattnd (90%)

•The tutataaj waiitesai wtsvsdfar 1 hrat l70*Cfeafoiedsiwi| to m. 165

14 J. Dacttttjraf

Sfee Defbtsattioa of •t/tri CO (ODBL)

% 8 25 % 8 100 % 8 200 % 4 25 4 100 % 4 ISO % 4 175 % 4 200 % 4 250 % 4 300 % 6-5 25 \ 6.5 100 % 6.5 ISO % 6.5 250 % 3.25 25 % 3.25 100 % 3.25 ISO % 3.25 175 % 3.25 200 % 10 25

acquired, and some improvement in as-received duc­ A robVbooding technique has been developed to join tility was found. However, removal of 0.001 to 0.002 the %-, %-, and "j-in.-OD tubes to the dosed-end feed in. from the ID greatly improved its room-temperature pots and upper and lower column disengagement ductility, indicating that ID contamination is definitely sections. Some of the coimnerdsuy obtained tube the r»ost significant problem. expanders that we are using to make these joints ire shown in Fig. 14.1. The tool fits inside the tube to be ioined suck as the one shown extending into the boss of Table 14J. Mechanical bckaviof of %-isvOD tubiag the typical back-extruded half section in Kg. 141. as a fraction of removing tmaemtaM layers torn the ID swiace Expandable tube rotters then meclianicslh/ force the tube against the surface of the boss to which it is to be Material joined. Because of its room-temperature brittlencss, Deformation removed Temperature disptacement/^tbe Observation molybdenum join** are more easily made at 250°C; in from (°C) diameter (%) order to prevent contamination of areas that must be ID (in.) subsequently joined by welding, an inert atmosphere is 7 0.002 25 Hairline crack required (Fig. 14.2). Leak-tight joints (<1 X 10" aim 0X102 125 Hairline crack cc/sec) have been made under the following conditions: 0.004 25 Hairline cracks 0JM>4 125 No cracks 0J0O6 25 No cracks 0.006 125 No cracks 0X08 25 No cracks (0*>«.) (fav*) 0X08 125 No cracks 0X10 25 No cracks % 10-12 0X10 125 No cracks % 30-35 166

PHOTO 4990-^

Fig. 14J. T«be expanders used in rott-boodiag mofybdcaam.

These joints were also leak-tight after they were 14.2 FABRICATION DEVELOPMENT thermally cycled ten times from room temperature to OF MOLYBDENUM COMPONENTS 650°C. To further strengthen roll-bonded joints, each joint A. C. Schaffhauser R. E. McDonald will be sealed by a chemically vapor deposited tungsten We have completed development of a back-extrusion layer on the bismuth or salt side and. wil! be back 7 process for fabricating 3 / -in.-diam closed-end molyb­ brazed with the alloy Fe-15% Mo-5% Ge-4% C-1% B 8 denum vessels for head pots and disengaging sections of on the in*srt gas atmosphere side. A macrophotograph the molybdenum test stand. The process has been of a cross section through a typical joint and blowups described previously.3 A starting blank, tooling, and a of the three types of seals are shown hi Fig. 14.3. completed tack extrusion are shown in Fig. 14.4. The More detailed information on the design and purpose of the molybdenum test stand is presented in Part 4 of this report. Progress on welding, brazing, and fabri­ 3. R. E. McDonald and A. C. Schaflhauaer, MSR Program cation of molybdenum compone&U is reported in this Smkmm. frogr. Rep. Feb. 28. 1970. ORNL4548, pp. section. 253-54. 167

PHOTO «99«-7*

Ffe. 14 2. RoMxmdiaf nofarbdmwn radar fawrt *m*pku* at 250°C 168

Y- 409960

Fig. 14.3. ScctiM I

tooling consists of a 3%-in.-diam plunger and a split die the required length as did the odiers. It was reheated to with an oblong hole in the closed end to produce a boss 1700°C, and by carefully aligning it with respect to the needed for support of inlet and exit tuLes. Alt surfaces die it was again back extruded to increase its length of the tooling in contact with molybdenum are coated without altering the preformed boss. with plasma-sprayed ZrOj to prevent chemical inter­ Our studies have shown that back extrusion of action. molybdenum depends upon the quality of the starting We have fabricated all of the required eleven 3%- blank, back-extrusion temperature, and reactivity be­ iiL-dum back extrusions for the molybdenum test tween the tooling and molybdenum. Some of the early stand. Four of five 5-m.-k>ng back extrusions have been starting blanks had small surface cracks, and we found machined for the salt and bismuth head-pot assemblies, it difficult to avoid cracks in the finished product. leaving one spare. Two of three 8-tn.long back ex­ Initially we used a Zr03-coated plunger and die, but the trusions ue being machined for the lower disengaging die length was short and allowed the molybdenum to section of the packed column, also fcaving oac spare. contact the tool steel container of the press along its All of these back extrusions were accomplished at OD as it was being back extruded. Interaction of the 1600°C with a stem load of 800 to 900 tons. molybdenum with the steel caused some tearing of the In order to make the lower disengaging section of die OD surface. This was eliminated by use of a ZrO?- column from two back extrusions of approximately coated long-length die as shown in Fig. 14.4. We also equal length, 9V,6-in.4ong half sections are required. A found that recoating both plunger and die before each 12-in.4ong (he was procured, and three half sections back extrusion ensured high-quality finished products. between 9 and 10 in. long have been back extruded at Since coating and tooting life is dependent upon 1700°C. One of the half sections was made in two temperature, we tried temperatures from 1350 to steps. Under similar conditions, it did not back extrude 1700°C during our development period. Unfortunately. 169

Y-«or*e»

4 l i I l J INCHES

F%.14.4. tadMxtfwhMi toouag with stvttag

we often had more than temperature as a variable and described in an earlier report.4 During this period we were unable to conclude what might be the optimum have fabricated more complex uructures which sim­ temperature. However, we did find we were able to ulate actual loop components. We are aho optfasMng conastentry produce apod quaMty oack extrusions at our welding procedures and are desjaning and bufldttg temperatures from 1600 to 1700°C. Tensile and bend- weld fixtures. test specimens have been machined from hack ex- Asa^iiidtor^ri(»tioii,m^liavebeasncotu4ructinga trvskms made at several temperatures for mechanical rutt-scale mockup of the moijrbdennm test stand. properties evaluation. Wooden models of the four pots ware oaade, aad short stubs of Mood tubing wart inserted in the.approprfarte 143 WELDING MOLYBDENUM holes in the boast*. The tubas ware piiriouny bent to the shaoaa remaned of the moivMenuBn A. J. Moorhead Three major types of welded joint (tube4o-headtr, hesritt-to-fieader, and tube-to-tube) are required for •#• A* -J* klOOOMmwJ MM •• R* _ w fabrication of the molybdenum test stand for chemical Smmtmtm. f>»r. Jtnv. Fsk 2$, 1971. OHIVMtt, an. ptuosssing. Our initial work on time three joints was 230-21. 170

INLET OUTL£T

F%.KJ>. Feed pot for chc—ical ptoctmag loop.

subassemblies are presently being used to check out the plates for the head pots. These welds, which were of the rotary fixture for girth welding to ensure that the tube-to-header type, were made by rotating the electron fixture and pots are compatible. Subsequently, the pots beam around the joint rather than by rotating the wiO be interconnected with full lengths of tubing to workpiece under the beam. The speed of beam rotation evaluate the procedures and fixturing for tube-to-tube was manually controlled. This technique is very useful welding sad brazing in the glove box and in the field. in welding parts in which the weld joint is off-centered We have developed a procedure for electron-beam (as ir this case) or otherwise difficult to rotate. welding the %-bvdiam tube-to-headet type of joint. Visually, both welds looked good, and no defects were The standard 80-mil wall thickness of the molybdenum detected by fluorescent penetrant inspection. tubing will be machined down to 50 mils for this weld. Three sets of back-extruded headers were successfully Therefore, %-in.-OD X O-050-in.-wafl tubes were joined by girth welds to form three nearly full-size feed welded to 1%-UL-OD cyhnders representing the boss on pots. The first u\ was welded using the electron beam the back-extruded header. The weld joint was preheated process and the step joint (shown as the "alternate" to about 700°C with t>e defocused electron beam. joint) in Fig. 14.5. Both header* were preheated to Welding parameters were 1404V accelerating potential, above 700*C with the defocused electron beam prior to 10mA beam current, 1 l-hv/mm travel speed, with the welding; earner work had revealed that preheating was beam defocused 15 mA. This is the final size of tubing necewary to prevent weldment cracking, although the to be welded in developing procedures for welding the ntinarum preheat temperature has not been de­ tabe-tc~header type of joint. termined. The welding parameters were: 1404V ac­ Two '^-tn.-dJam tubular wears were electron-beam celerating potential, 20-mA beam current, 4) J-in^min welded into one of the %-in.-thkfc molybdenum baffle work travel speed.and trie beam defocused 10mA from 171 sharp focus. No weld defects were revealed by flu- ves-groove weld joint (Fig. 143), using low-carbon, orescent-penetrant inspection. However, metallographic low-oxygen molybdenum filler wire. No weld preheat examination revealed that weld penetration was about was requiicd. One of these welded pots is shown in Fig. 45 mils rather than the desired 100 mils. We will try to 14.6 togethei with the two back-extruded headers. No overcome this shortcoming on the next practice weld defects were detected on either arc-welded feed pot by using a more sharply focused besm and a higher when they were fluorescent-penetrantinspected . beam current. To more closely simulate conditions requketi in The other two sets of headers were joined using the fabrication of the test stand, additional tube-to-tube manual gas tungsten-arc process in an argon-filled welds have been made with the orbiting arc weld head. chamber. Two weld passes were required to fill the 90° Longer lengths of tubing were joined with the axs of

Y-1Q60M

Pfc, 14* Ma»MiiiM>acfcutiriilhalfgmioMioaMi»yCrA waMMj, 172 the tube vertical. As we expected, probL ms of axial must be roll bonded or welded and then back brazed. tube misalignment after welding ai.d weld cracking due At the same time, a split ring covering the girth welds of to excessive restraint of the joint occr red. In order to the pots or chambers will also be brazed. Mockups of overcome these difficulties, we have procured longer these subassemblies were biazed in a resistance furnace weld inserts to provide better internal support and a with a 7-in. X 7-in. X 30-in.-long chamber at relatively yoke type of fixture for external support. The latter isothermal conditions at a pressure of 10"s torr. will be left in place around the joint until after the To ensure proper flow of the br^ing filler metal into sleeve surrounding the weld has been attached. the joint, a joint gap of at least 0.001 in. is necessary. We are ako in the process of optimizing our welding However, the joint preparation for roll bonding and procedures for each size of tubing to increase the welding requires a closer tolerance to product sound reproducibility of these welds. Helium-leak-tifeht tube- welds and proper alignment. Therefore, the porf^n of to-tube welds have been made in all the required sizes the joint to be back, hra.ed will be counter b.red an of tubing, but the penetration achieved on the %• extra 0.0015 to 0.0025 in. on the diameter to a depth in.-OD tubing has been only about one-third of the of \ in. We have also provided filler-metal feeder holes 50-mii v/all thickness. The welding current required to by drilling into the bosses of the large components; make uVse latter weMs is relatively high (110 amp), these serve as reservoirs for the brazing alloy powder and the wekir g speed slow (11 in./min), resulting in and provide insurance that the filler metal does not overheating oi :he orbiting-arc weld head. Therefore, prematurely flow away from the joint. Otherwise, the we are investigating the use :,l a weld cycle in which the thin-walled tubing may reach the brazing temperature current is pulsed between a high current (to get deeper faster than the heavy pot, and the brazing fi'lc. niSUl penetration) and a lower current to permit some might flow along the holler tube (and away from the cooling of the head. joint) raiher than into the joint.

14.4 DEVELOPMENT OF BRAZING TECHNIQUES 14 A 2 Induction Vacuum Brazing FOR FABRICATING THE MOLYBDENUM TEST LOOP We plan to manually weld the 1 %-in. OD X S-ft-long X 0.080-in.-wall packed column of the chemical proc­ N.C.Cole essing system in a dry box filled with argon. In The iror**ase alloy, Fe-15% Mo-5% Ge-4% C-1% addition, the 4-in. tubing that connects the bismuth B, has been selected as the filler metal for back-brazing head pot to the upper disengaging section of the joints in sections of tr.e chemical processing test loop column will also be welded in the dry box. Because of that will contain bismuth. Back brazing will serve two the size and fragility of the-e large welded sub­ purposes. It will provide reinforcement to the weld assemblies, we plan to induction braze the reinforcing zone which is brittle at room temperature, and it will sleeves over the weld before the 10-ft assembly is provide a seal should a leak develop through a roll bond removed from the dry box. The controlled atmosphere or a cracked weld. The alloy selected satisfies the of the dr' box will also be utilized to prevent oxidation requirements of having a moderately low brazing of all portions of the assembly which will be heated temperature (<1200°C) and adequate resistance to duiing the welding operation. bismuth at 65C°C. Since specific brazing techniques for In prelLninary experiments, we learned that brazing the variety of joints encountered have never been must be accomplished in vacuum (1G~S torr) since we developed previously, much of our work has been experienced difficulty with arcing in helium or argon devoted tc basic process development and im­ atmospheres. To add further complication, the organic provement. W< have developed several methods of binder, which is used to preplace the powdered filler brazing using resistance and high-frequency induction as metal, caused arcing when it began to vaporize. As a the heatii£ sources. result, it is necessary to vaporize the binder by other heating techniques before the induction unit is ac­ 14.4.1 Resistance Furnace Brazing tivated or else preplace the fiiier metal without using the binder. To eliminate the need fo. the binder, we Small thjn-walled tubes have been brazed to large pots have machined grooves on the inside diameter of 3% in. OD X 9% in. long X % in. wall) in vacuum in a samples of split sleeves to hold the powdered filler resistance furnace. Into each end of the container metal. These grooves also allow space for the reinforced shown in Fig. 14.S, two or more short hngths of tubing (raised) weld bead. 173

We have induction sleeves over tube-to-tube welds in remain relatively cool, and the entire brazing cycle the atmosphere chamber. However, actual mockup fakes less than 5 min. assemblies have not been brazed tut are currently being We

Y-106657

¥%. 14.7. Sleeve biased to notfbdttmm tab*. 174 maximum temperature of 7Q0°C, and the loops have a mil/year, the room-temperature mechanical properties A7* of 95 ± 5°C. For lithium concentrations up to 100 of the molybdenum were unaffected by exposure to ppm, we have used quartz !o. ps, but for higher Bi- 100 ppm Li, at indicated in Table 14.5. concentrations of lithium (<2.5 wt %) the loop is made Tantalum specimens exposed to Bi + 100 ppm Li in from the material to be tested. loop 13 losi weight at all temperatures (Table 14.4). Previously we reported grain boundary cracking of The maximum lo?? (45 2 mg/cm2) corresponds to a small surface grains on recrystallized molybdenum corrosion rate of 3.! 3 mils/year. This does not agree samples.5 Since cracking was limited to these grains we with results obtained by Shimotake et al. in short-term hope to circumvent this problem by removing these tests (100 hr) at 1000°C in which they reported no grains prior to testing. This vas done by electro- observable corrosion.6 The room-temperature me­ poiishing samples after vacuum annealing for 1 hr at chanical properties of these samples were unaltered !500CC. These samples were included in loop 11, and (Table 14.5) even though there was a detectable the results arc suruinarized in Ta^ 5e 14.4. decrease in their dimensions. The maximum measurable The samples lost weight above a temperature of change in dimensions corresponds to a uniform surface 650°C and gained weight at or below this temperature. remr /al of 2.6 mils/year, which is in close agreement Because of difficulties in removing residual bismuth with that calculated from weight-change data. from the specimens, we cannot be certain of the Conversely, the Till aUoy (Ta-8% W-2% HO absohite magnitude of the weight changes, although tested in lcop 12 showed excellent resistance to they are relatively small. The effect of electropolishing dissolution and mass transport. Tensile samples all will be evaluated by metallographic examination of the showed slight weight losses of up to 4.45 mg/cm2 (031 specimens. A maximum weight loss of 3.18 mg/cm2 mil/year), but all the tab samples had weight increases was observed on one of the tensile sampler and of up to 037 mg/cir2 (Table 14.4). These weight losses corresponds with a uniform surface removal of 036

6. H. Shrmotake, N. R. Stalica, and J. C. Heson, "Corrosion 5. O. B. Cavin and L. R. Trotter, MSR Propum Sohuuvm. of Refractory Metals by liquid Bismuth, Tin and Lead at Prop. Rep. Aug 31,1970, ORNL4622, p. 189. 1000°C,n Tnns. Am. NucL Soc 10,141-42 (June 1967).

Table 14.4. WefeM change of avitena b tested • fMmjbmMttt « for 3000 to

RecrystaDjzed tabs Tens*'* samples Surface Surface Material Temperature Weight change removal* Temperature Weight change removal* 2 (°Q 2 (°Q (mg/cm ) (mil/year) (mg/ci ) (mil/year)

Mo 650* •0.09 660 None (loop 11) 670 -1.30 -0.15 690 -3.18 -OJ6 620 +0.46 640 •0.14 650* -•1.09 660 -038 -0.04 Ta 650 -16.29 -1.13 660 -22 55 -t.56 (loop 13) 670 -2.24 -0.16 690 -45.H -3.11 620 -38.32 -2.66 640 -15.11 -1.05 650 -5.63 -0.39 6c0 -13.66 -0.95 T-lll 650 +i,.24 660 -0.2* -0.02 (bop 12) 670 •0.37 690 -4.45 -0.31 620 •0.15 640 -0.48 -003 650 +0.28 6C0 -0.75 -0.05

'Bismuth contained 100 ppm Li. 6Assuming uniform surface removal. cSamples were electropofished prior to test. 175

TaMe 14.5. Room-temperature dMchanfcal properties of materiab tested in flowing bismuth" for 3000 hi

Test Fracture strain Tensile strength Yield strength6 Sample temperature (°C) (%in 1.S in.) (psi) (pa)

X 103 X 103 Mo-1 660 8.0 111 101 Mo-2 690 11.3 HI 104 Mo-3 640 11.3 112 104 Mo4 660 11.3 112 105 Mo As received 8.7 110 100 Ta-1 660 26.0 4o.5 33.7 Ta-2 690 23.3 47.2 35.4 Ta-3 640 ".7 46.7 32.6 Ta4 660 26.0 50.0 36.7 Ta As received 24.0 44.2 35.7 Tlll-lc 660 0 61.4 d Til 1-2 6<»0 0 51.7 d Tl!l-3 640 0 46.7 d Til 1-4 660 1.7 88.0 87.3 Tlll-5r 700 15.3 91.7 79.2 Til 1-6 As received 10.0 95.9 81.0

"Bi contained 100 ppm Li. d0.2% offset. cTa-8%W-2%Hfafloy. dBritue fracture. 'Aged 3000 hr in argon atnosphere.

are of the same magnitude as those observed for Fouv grades of giaphite were tested in loop 14, and molybdenum. However, the loom-temperature ductility the weight-change data are shown in Table 14.6. All the of the T-111 was drasticaDy reduced, as shown in Table samples increased in weight except the high-density 14.5. This is no different from the data previously pyroh/tic sample. The available open porosity of grades reported for T-111 in pure bismuth.7 To determine the AXF-SQ and ATJS are IS and 13%, respectively, but effects of aging T-1! 1 at 700°C, samples were held at the majority of the pores in AXF-SQ have »r. entrance this tempera* ire for 3000 hr in an argon-filled capsule. diameter of 0.8 to 1 /i, and those in ATJS have a No significant changes in the room-temperature me­ diameter of 3 to 5/i.10 chanical properties were observed, and, if anything, the Grafoil is a trade name for a laminated low-density ductility was slightly higher. The microstructure of the graphite foil used for gaskets. It has many large open as-received material shows a grain boundary precipitate. pores and in the uncompressed state was infiltrated by Similar precipitates have been identified by Inouye8 as bismuth. A graphite bolt was used to hold a second HfC and by Sheffler and co-workers9 as a hafnium sample of Grafoil under compression during test, but oxide. We are presently evaluating the extent to which weight-change information was not meaningful because such hafnium-rich phases may interact with bismuth or the bismuth had penetrated along the threads und*r the impurities dissolved in bismuth. nut. Other means will be used to compare the bismuth intrusion into the compressed and unimpressed Grafoil. The total amount of bismuth intrusion into graphite 7. O. B. Cavin and L. R. Trotter, MSR Program Semiamtu. Progr. Rep. Aug. 31,1970, ORNL-4622, p. 189-9J. appears to depend upon the pore entrance diameter and 8. H. Inouye, privat: communication. 9. K. D. Sheffler, J. C. Sawyer, and E. A. Steigerwakt, "Mechanical Behr.r of Tantalum Base T-lll ABoy at Elevated Temperature," Trans. ASM 62,749-54 (1969). 10. W. H. Cook, private communication. 176

Table 14.6. Results obtained oa graphite tested in ftowiagBi-100 ppnl: for 3000 ar

Noroalized Density Test temperature Weight change Sample 3 wei;ht change (3/cm > CO (mg) (mg/cm3)

AXF-50-1* 181 666 +8.4 +2.7 AXF-SQ^ 1.30 680 +2.6 +0.8 ATJS-1* 1.84 678 -36.4 +11.1 ATJS-2* 1 82 665 +20.0 +6.1 Pyroiytic-1 2.14 655 -0.6 -0.5 Pyrolytic-2 2.12 650 -1.4 -1.3 Grafoulc 1.08 +529.4 817.7 Giafoa-2c 1 12 620 H671.6 1095.8

'Manufacture! by Poco Graphite Inc., Decatur, Texas. ^Manufactured by Union Carbide C«« . Carboc Products Division, New Yoiic. N.Y. CA trade name for lamixated graphite fa» used for casket* and manufactured by Carbon Products Division of IXC.

not primarily upon the total available porosity. Since 14.6 CHEMICAL VAPOR DEPOSITED COATINGS graphite generally is an ^homogeneous material as to density and porosity, samples taken from the same J. I. Federer billet may vary considerably. This, as well as the uncertainty in complete bismuth removal, .ouiti account for some of the weight-change variations Roll bonding of molybdenum tubes to integral bosses observed in Table 14.6. ai'ached to molybdenum vessels is being used to make An all-metal T-111 alloy loop containing T-111 mechanical joints. Although these joints can be made tensile samples has been successfully filled with Bi—2.5 hak-tight, brazing from the outside of the vessel will wt % Li (nominal composition) and is operating at a icinforce the mechanical bond. A chemical vapor maximum temperature of 700°C with a A7 of 100°C. deposited coating around the joint on the inside of the Many of our analyses of tests recently completed are vessel is also contemplated as an added precaution. The still in progress; however, the results are encouraging. coating provides an additional sealf hat nunioiizes any Of the materials tested, molybdenum continues to be compatibility problems between the braze alloy and the least affected by exposure to bismuth and Bi-100 bismuth. Several joints have been coated for evaluation. ppm Li up to temperatures "»f 700°C. Equal dissolution These were made by roll bonding 0-5-in.-OD mo­ and mass transport data were obtained on T-l 11 alloy, lybdenum tubes into 0.5-in.-ID molybdenum cylinders. but it became embrittled by exposure to bismuth, The tubes extended about % in. or more out of the probably by an intergranular Hf-Bi reaction. If this cylinders. Four joints were coated at S00°C with reaction resulting in loss of ductility can be eliminated 0.002-, 0XJ07-, 0.015-, and 0i)18-in.-thick layers of by some pret.eatment of the T-111 or by alloying tungsten. Three other joints were coated at 900°C with additions, a tantalum-base alloy may also be attractive 0.005- to 0.0G9-in.-thick layers of molybdenum. The as container material. Graphite appear: suitable if the joints had very small but measurable helium leak rates available open porosity can be eliminated, at least at the prior to coating (~10~* std cc/sec). After coating all surface. Tests will be done to determine the extent to the joints were leak-tight as determined with a helium which bismuth will penetrate commercially available leak detector having a sensitivity of 8 X 10~10 std graphites and to evaluate the resistance of pyrolytically cc/sec. sealed ^aphite to bismuth and bismuth-lithium in­ An attempt was made to coat a HasteDoy N loop with trusion. A molybdenum thermal convection loop is tungsten so that the coating could be tested in flowing being readied for operation and will contain Bi-2.5% Li bismuth. The loop dimensions, pteliminary coating at 600 to 700°C. experiments, and the method for coating the loop were 177 desciibed previously.1' Portions of the coated loop lybdenum. The coating en the type 304 specimen was that were accessible to a borescope were visually too rough for accurate thickness measurements. !ne examined. The entire loop was radiographed. We coating on the type 430 specimen was much smoother determined that all surfaces of the loop were coated, but spalled during bend testing. Since previous ex­ but that several small cracks occurred in the coating at periments showed that molybdenum coats smoothly on the corners of two joints where tubing was welded specimens electroplated with nickel, we believe that the together at approximately a 90° angle. Also, the coating electroless nickel was responsible for the poor costing was thinner in one cross member than elsewhere, and a characteristics. These results and the previous obser­ Vt-in.-diam blister occurred in the cross member near vation1 ' that both tungsten and molybdenum coatings one of the joints mentioned above. Subsequently, we are less adherent to ekctroless nickel containing about coated the two joints and the cross member again. 8% phosphorus indicate that electroless nickel is in­ Radiography revealed that the cracks on the joints were ferior to electroplated nickel for promoting adherence. filled, the blister was covered, and the coating thickness in the cross member was comparable to other parts of

the loop; however, a new crack was found in the cross 14.7 MOLYBDENUM DEPOSITION FROM MoF6 member. This crack was probably caused by the large difference in thermal expansion between tungsten and J.W.Koger Hastelloy N. The cross member was coated again, but We have continued to conduct experiments to op­ the crack persisted, and further attempts to coat the timize the conditions tor coating stainless steel with loop have not been made. molybdenum by contacting the stainless steel with a Several specimens of types 304 and 430 stainless steel molten fluoride salt containing MoF«. Holding temper­ were nickel plated by the electroless method so that the ature and time constant, we have determined the

adherence of tungsten and molybdenum coatings to the concentration of MoF6 which must be added to our salt specimens could be evaluated. The plating method used mixture to get a eating. Future plans involve an for these specimens yielded a phosphorus content of evaluation of time god temperature effects on coating about 2% in the nickel plate compared with about 8% rates and coating integrity. phosphorus in specimens plated previously. One spec­ In one of our more successful runs, micropfobe imen of each type steel was coated with about analysis1* of the type 316 stamfess steel capsule on 0.004-in.-thick tungsten. The coating was smooth in which molybdenum was deposited showed that mo­ both cases but spatted from the type 430 specimen lybdenum was deposited at the sample surface and that during bend testing. Another' pair of specimens was grain boundaries at least 350 u into the metal were coated with about 0.00i- to 0J004-in.-ihick mo- enriched in molybdenum.

11. J. I. Federer, MSR Prj nan Sentiannu. Prop. Rep. Feb.12 . Performed by H. Msteer, T. J. Heiuon, and R. S. Crone 28.1971. ORNL-4676, pp. 231-32. of the Metab and Ceramics Dfaricton. Part 4. Molten-Sait Processing and Preparation

L. £. McNeese

Part 4 deals with the development of processes for the UFs The molten salt containing UFS appeared to be isolation of protactinium and the removal of fission stable in both gold and graphite equipment. These re­ products from molten-salt breeder iczctoa. During this sults are in agreement with thov from scouting experi­ perod we continued to evaluate and develop a flow­ ments carried out several years ago on fuel reconstitution. sheet based on fluorination-reductive extraction for During this report period we found that the lithium protactinium isolation and the metal transfer process and bismuth concentrations in LiCl in equilibrium with for rare-earth removal. The portion of the flowsheet lithium-bismuth solutions are higher than initially ex­ dealing with recovery and recycle of th* UF* from the pected and increase markedly as the lithium concentra­

Cuorinators was modified so that the UF6-F2 gas tion in the Ifthium-bismuth solution is increased. We stream would be directly absorbed in molten salt realized that this could have a significant effect on the containing UF4 and the resulting uranium fluoride performance of the metal transfer process since lithhun- would be reduced to UF4 by contact of the salt with bismuth solutions having lithium concentrations of 5 hydrogen. A method was devised for recycling fluorine, and about 50 at. % are proposed for extracting rare hydrogen, and HF in the plant in order to miriimize the earths from lithium chloride in the process. Therefore, a quantity of radioactive waste produced. A study was study of the equilibrium distribution of lithium and completed for determining the capital and operating bismuth between molten LiCl and liquid lithium- costs for a plant that processes the fuel salt from a bismuth solutions was initiated. Data obtained thus far 1000-MWXe) MSBR on a ten-day cycle. The total direct with lithiuir concentrations of 20 to 50 at. % are and indirect costs for the plant were found to be $20.6 consistent with the observed behavior of lithium in the and $15 million, respectively; thus the total plant second metal transfer experiment (MTE-2) completed investment required would be $35.6 million. The previously. An engineering experiment involving the resulting fuel cycle cost was 1.12 mills/kWhr. A metal transfer process (MTE-2B) is in operation in order 0.28-power dependence of processing plant cost en to study further the behavior of lithium in the process. processing rate was derived; this indicates that a The experiment, in which a 5 at. % lithium-bismuth considerable saving in processing cost could be achieved solution is being used to extract rare earths from by associating a processing plant with a larger power lithium chloride, has been in operation for about nine gc leration capacity than 1000 MW(e). weeks. To date, the results indicate that the equilibrium Studies relating to the chemistry of fuel reconstitu- concentration of lithium in lithium chloride above a 5 at. % lithium-bismuth solution is less than 0.3 wt ppm. tion were initiated. It was found that gaseous UF6 reacts quantitatively with l»F dissolved in LiF-BeF - It is not believed that the metal transfer process will be 4 2 affected significantly by the unexpected behavior of ThF4 (72-16-12 mole %) at 600°C to produce soluble

178 179 lithium and bismuth in the process. The design of the aiong with data from the literature, indicate thai third engineering experiment (MTE-3) for development satisfactory mass transfer performance may be achieva­ of the process was completed. Most of the equipment ble in this contactor without dispersing either the salt was fabricated, and the main process vessels are now or the metal phase. Contactors ci this design may be being installed. The experiment will use salt flow rates easier to fabricate than packed columns, and the that are 1% of the estimated flow rates required for problem of entrainment of bismuth in salt to be processing a 1000-MW(e) reactor. returned to the reactor should be eliminated If the Our work on contactor development was continued phases are not dispersed. successfully during this report period. Mass transfer We have continued studies of oxide precipitation as experiments were carried out in which the rate of an alternative to the fluorination—reductive-extraction transfer of zirconium from molten salt to bismuth was method for isolating protactinium and for subsequently measured in a 24-in.-long, 0.82-in.-ID column packed removing uranium from MSBR fuel salt. Protactinium with %-in. molybdenum Raschig rin<*s. The results pentoxide was selectively precipitated from LiF-BeFa- indicate HTl» values of 1 to 4 ft, with the lowest values ThF4 (72-16-12 mole %) that contained up to 0.25 being given by data in which we have the most mole % UF4 by sparging the salt with HF-H20-Ar gas confidence. These results indicate that packed column mixtures at 600°C. Recent results on the equffibridu contactors c?n be used successfully in MSBR processing quotient for the precipitation reaction are in agreement systems. We have initiated studies on mechanically with earlier results and are consistent with earlier agitated salt-metal contactor* ^s an alternative tc indications that Pa3Os can be precipitated from MSBR packed columns. This type of contactor is of particular fuel salt as a pure or nearly pure solid phase. Installa­ interest for use in the metal transfer process since tion of equipment was completed in preparation for designs can be envisioned in which the bismuth would engineering studies of the precipitation of UOa-ThO* be a near-isothermal internally circulated captive phase. solid solutions from molten fluoride salts. Two experi­ The hydrodynamic performance of a mechanically ments in which as much as 40% of the uraniutn inivi&By agitated contactor was investigated using mercury and in the salt was precipitated were carried out SOCASS- water to simulate bismuth and molten salt. These data, fully. Results of these experiments are encouraging.

15. Flowsheet Analysis

A study was completed in which the capital and 15.1 COST ESTIMATE FOR AN MSBR operating costs were determined for a plant that PROCESSING PLANT processes the fuel salt from a 1000-MW(e) MSBR on a W. L. Carter E. L. Nicholson ten-day cycle. The plant is based on the reference L. E. McNeese flowsheet that uses fluorination, reductive extraction, and metal transfer. Capital and operating costs were We have completed a study to determine the capital calculated for two methods for obtaining and disr osing am1 operating costs for a plant that processes the fuel of hydrogen, HF, and fluorine in a processing plant. salt from a 1000-MW(e) MSBR on a ten-day cycle. The Calculations were made of the thermal power that will processing plant is based on the previously described be produced in an MSBR processing plant by the decay reference flowsheet1 '3 that uses fhiorination for ura­ of noble-metal fission products as a function of the nium removal, reductive extraction for protactinium residence tin.^ of the; materials in the primary reactor removal, and the metal transfer process for rare-earth system and of the fraction of these materials accom­ removal. The most recent version of the flowsheet, panying the fuel salt to the processing plant. The long-term hazard of high-level radioactive wastes pro­ duced by MSBRs was considered. A survey was izste of published data on th e availability of and future demand 1 L.E.McHee9t,MSRProfrwmSemicmm.m3gr.Rep.Fe*. 28.1970. ORNls4$48, pp. 277-88. for natural resources required for an MSBR power 2. L E. H*Neeat,MSR Propwm Semfarviu. Prop. Rep. FA economy. 28.1971, ORNL4676, pp. 234-38. H2 TO «>'IRGE COLUMNS (95%) (5%)

Al203 SORBER (10 scfm)

(SeFs-TeFs)

H2 MAKEUP

H2+HF FROM HYOROFLUORINATORS AND PURGE COLUMNS CAUSTIC SCRUB

H +HF 2 * 1 I (14.9scfffP I (105scfm)li SALT MAKEUP KOH (Har-Hl) (2 gal/mini acF2(74.8g molt/doy)

ThF4 (100.3 g mole/day) DISTILLATION

|Ufs REOUCTION

-4) CARRCR SALT OlSCARO

(LiF-BeF2-ThF4) n- '2.38 gal/day) BISMUTH REMOVAL

u d! r~£FISSION PRODUC' T I TRANSFER 3 TOLiCI + RARE EARTH I EXTINCTION SALT CLEANUP AND HFTO |U*+A)4+| HYOROFLUORIMATORS I VALENCE* ADJUSTMENT ^ISMUTH_ iSf^zPE-lj-.. —. — i. —. — J "(12.4"gol/miB)"~ """"""' 7*"""" F2+UF« FUEL SALT RETURN TO REACTOR (0.6?gol/nift) ^ F- A UFC PRODUCT SECONOARY REMOVAL FLUORINATION (1659 U/doy) LJ

SALT FROM REACTOR *2 <

UF-B»F2-ThF4-yF4 71.7-16.0-<2JO-0.3 «wM>% (0-67gol/i»ifl)

Hg-HF TO 1 PRIMARY Pa STORAGE AND DECA:AYY \ FLUOfllNATtONl RECYCLE LiF-THF4-ZrF4-Pol4 U7<-0-2&0-2.«»-0.2 moi* I \J2 »"^ BISMUTH Jf 150-1*5 ft3 V 1 I f(0.l3gol/min) V J BATCHWISE DISCARD (25ft 3/220 days) *» PRIMARY STREAMS F HYCROFLUORIKATION 1 UF-B«F2-T>iF4 SALT 220-day — — —— BISMUTH Pa DECAY —»« LiCi HF-H, / \ F2-UF, (0.78gal/min)

Ffc 15.1. FtooriMtkM-redactive extnctiM-nietal transfer process flowsheet tot processa*MSBR fuel «IL Flow rates are shown for processui floorisntov of 95%. BLANK PAGE 180

OftNL- DWC 71 - 7M9A

AljO, SOR9ER CHARCOAL SORBER -•> VENT TO STACK

(StFc-T«Fs) J-HD (Kr-Xc)

LITHIUM AOOITION (53 9 mote/doy)

.* shown for processing a lOOO-MW(e) reactor on a ten-day cycle with an assumed uranium removal efficiency in the primary 181 shown in Fig. 15.1, inchides two significant improve­ carrier salt for return to the reactor. Several difficulties ments over the previous version of the flowsheet: (I) an were encountered with this approach, for example: (1) improved method for recovering UF* from the fhiorina- the uranium inventory in the UF« collection system tor off-gas and (2) a method for recycling fluorine, would be appreciable (3 to 10% of the uranium hydrogen, and HF in the processing plant in order to inventory in the reactor); (2) beds of granular heat- minimize ihe quantity of radioactive waste generated. emitting solids (NaF) would have to be filled and The behavior of fission products and other com­ discharged remotely; (3) the discharged NaF would ponents of the fuel salt in the processing plant is require subsequent treatment in order to ensure ac­ summarized in Table 15.1, which shows only the ceptably low uranium losses; and (4) collection of UF« dominant removal method for each of several groups of in the cold traps might be complicated by heat fuel salt constituents. The removal times for the noble produced by the decay of fission products that are gases (SO sec) and noble and seminobie metals (2.4 hr) desorbed from the NaF beds with the UF«. Initially in are short as compared with the ten-day processing the present study, consideration was given to recycling cycle, and only small amounts of these materials are the unused fluorine after UF« collection; however, removed by the processing plant. In the previous several problems were encountered with this mode of flowsheet,1 the fluorinator off-gas (primarily a mixture operation. The two major problems were: (1) fission of fluorine and UF6) passed through NaF sorption beds product iodine accumulated to appreciable concentra­ and cold traps operated at -40°C foi UF« recovery. tions in the fluorine rearcuhrtion system and repre­ The UF« was then combined with the processed fuel sented a significant heat sou.ce (210 kW as shown in

Table 15.1. Methods for mrnri*

Group Components Removal time

Noble gases Kr.Xe SO sec fuel ck unit Semir Me metals Zn.Ga.Ge. As, Se 2.4 hr Plating out on vessel and heat Nobk metals Nb, Mo, Tc, Ru, Rh, 2.4 hr Plating oat on Ag,Cd,In,Sn,Sb, venal and heat Te Trivzknt rare earths Y,La,Ce,Pr,Nd, Varies for different Reductive extraction into BHi aBoy Pm,Gd,Tb,Dy,Ho, nuclides; effective followed by metal transfer via LiCl Er (note: Yttrium removal time * 25 into Bi-5 at % Li sortition is not a rare earth days but behaves similarly.) Divalent rare earths Sm, Eu, Sr, Ba Varies for different Reductive extraction into BHi aloy and alkaline earths nuclides; effective foBowed by metal transfer via LiCl removal time = 25 days into Bi-5 at. % Li solution Alkali metals Rb.Cs 10 days Reductive extraction into Bi-Li auoy followed by accumulation in LiCl Halogens Br, I 10 days Volatilization in primary fluorinator followed by accumulation in KOH solution in gas recycle system Uranium 233U,"4U,"5U. 10 days Volatilization in primary fiuorinator;

236U237U returned to c«iiicr salt and recycled to reactor Zirconium Zr, "3Pa 10 days Reductive extraction into Bi-Li aBoy and protactinium foUowei by hydrofmorinaHon into Pa dtcay salt Corrosion products Ni,Fe,Cr 10 days Reductive extraction with Bi-Li ?Jdoy followed by nydrofhiorination into Pa decay salt Carrier salt UBe.Th -1.5 years Salt discard 182

Sect. 153); and (2) maintenance on the sealed dia­ TaHelSJ. Capita! costs for a process* pint for a phragm-type fluorine compressors is known to be •000-lfW(e) MSBR based on the flBoantion-ieductive higher than desired. The alternative of disposing of the extraction-metal transfer flowsheet ue'ised fluorine by absorption in aqueous KOH solu­ Reactor fuel volume = 1683 ft* tions was unattractive because of the large volume of Processing cycle time — ten days radioactive waste (mostly KF) that was generated. Thousands In the current flowsheet, difficulties assecrated with of dollars UF* collection and recycle oi disposal of unused Installed motybdenum process equipment 4^79 fluorine were avoided by sending the F2-UF6 gas mixture directly to the UF reduction step, where both Instated molybdenum pumps 245 6 Instated rod Ixknum heat exchangers 90 the F2 and UF6 are absorbed in a sufficient quantity of Installed molybdenum piping 1,474 molten salt containing UF4 to produce an average Instated HasteBoy N, ^fainter steel, 3,129 uranium valence between 4+ and 5+. The resulting and nickel equipment Instated auxiiary equipment 2,486 uranium fluoride is reduced to UF4 by contact of the salt mixture with hydrogen. The reconstituted fuel salt Process piping (other than molybdenum 2,342 is then returned to the reactor after a final cleanup Process instrumentation 2,711 operation. The HF produced in the UF* reduction CeH electrical connections 494 operation is -snt to a remotely operated fluorine plant, Thermal insulation 588 where F2 and H3 are generated for recycle to the Radiation monitoring ISO processing plant. As discussed in Sect. 152, the cost for Sampling stations 1,275 recycling the fluorine and hydrogen via a fluorine Fluorine plan: 1,005 generation plant is only 0.024 mill/kWhr as compared Total direct cost 20,568 with a total cost of O.il rraU/kWhr associated with Construction overhead* 4,114 absorbing the HF in an aqueous KOH solution and F.nginwjiug and inspection 3,790 disposing of the resulting radioactive wastes. Taxes and insurance' 864 Contingency* 2,836 Cost estimate. la preparing the cost estimate, prelimi­ 32,172 nary designs for all major process equipment items were Subtotal completed, and the equipment cost was estimated using Interest during construction' 3,442 unit costs for fabricating the various structural shapes. Total plant investment 35,614 The general design criteria assumed that a material having a cost equal to that of Hastelloy N would be *20% of total direct cost used for vessels containing only molten salt and that *5.3% of total direct cost, plus a S2.7 million "novel" design molybdenum would be used for vessels that contained c4.2% of total direct cost. bismuth. The cost of fabricated molybdenum equip­ d 20% of toul direct cost, exclusive of the cost of molyb­ ment w*« assumed to be $200/Ib; a value of this denum components. magnitude was used because of the difficulty of 'Money borrowed at 8%/year for a three-year period. fabricating molybdenum. The costs of piping, instru­ mentation, and certain auxiliary equipment items were estimated as appropriate fractions of the costs of processing plant (0.7 mill/kWhr), inventory charges on fabricated equipment items. salt and fissile materials in the reactor and 233Pa in the A sammaiy of the capital costs for the processing processing plant (0.42 mill/kWhr), and processing plant plant is shown in Table 15.2. The total direct and operating charges (0.083 mill/kWhr): credit is taken for indirect costs are $20.6 and $15 million, respectively; the excess fissile material produced (0.089 mill/kWhr). thus the total plant investment is $35.6 million. Variation of the capital cost of the processing plant Fuel cyde cost. A breakdown of the fuel cycle cost is with plant throughput. The variation of the capital ccst given in Table 153 for a 1000-MW(e) MSBR that is of the processing plant with plant throughput was processed on a ten-day cycle (a processing rate of 0.38 estimated by determining the capital cost for a plant gpm) by fluorination—reductive extraction—metal transfe . The inventory charges on fissile materials and salt in the reactor are those given for the reference 3 3. R. C. Robertson (ed.), Conceptual Design Study of a MSBR design. The net fuel cycle cost (1.12 mills/ Single-Fluid Molten Salt Breeder Reactor, ORNL-4541 (June kWhr) is composed largely of fixed charges on the 1971), pp. 180-81. •«>•*«$*

183

TiMe 153. Fad cycle cost for a I0004fW(c) MS8R essing rate of 024 gpm), it is believed that a plant cost Processing cyde time = ten days of $25 nullion should be used (see Fig. 152). Plant factor = 80% The cost information shown in Fig. 152 indicates that a significant saving in processing cost can be MOb/kWhr achieved by using a processing plant with a larger power Fixed charges on processing plant at 13.7%/year 0.6962 generation capacity than 1000 MW^e). Although tins is Inventory charges at 13.2%/year undoubtedly true, the processing costs associated with a

UF-BeF2-ThF4 in reactor 0.0608 higher plant throughput cannot be obtained directly 233y 23Sy 233^ ^ j^^^ + + 0.3281 from Fig. 152 since a larger amount of radioactivity

UF-BeF2-ThF4 in processing plant 0.0073 would be present in the processing plant. 0.0286 LiCi in processing plant 0.0006 Bi in processing plant 0.0040 ORNL-OBS 7I-9843A too 1 0.4294 Operating charges Li metal makeup 0.0171 BSF2-H1F4 makeup 0.0209 50 _^0.**' HF makeup 0.0001 LOP en s c- o JH2 makeup 0.0002 o KOH makeup 0.00003 Waste disposal 0.0164 20 Payroll 0.0285 0.0832 10 Gross fuel cycle cost 1.2088 0.1 0.2 OS 1 2 Production credit (3.27%/year fuel yield) -0.0894 SALT PROCESSUS RATE f«rt/atol Net fuel cyde cost 1.1194 Fuj. 15 J. Variation of capital coat for a awe eTTracnow war rat nantiri throughput for a 10004fw{e) MSML

based on a 33-day processing cycle (a processing rate of 152 COMPARISON OF COSTS FOR ALTERNATE 2.9 gpm). The total plant investment for this case was OFF-GAS TREATMENT METHODS FOR AN $48.5 million. Th«? resulting cost data are shown in Fig. MSBR PROCESSING PLANT 152, where a power-type dependence of plant cost on throughput is assumed. The resulting cost-vs-throughput W.L. Carter relationship is: Capital, and operating costs associated with two methods (see Fig. 153) for obtaining and disposing of R \°-2« HF, H2, and F2 in a plant were determined. In the first method, HF, H , and F are purchased, and the H and -«(£J 2 2 3 HF that appear in the plant off-gas ore subsequently where disposed of; in the second, the HF and H» from the plant off-gas are collected, and the HF is electrotyzed to C = cost of processing plant, produce H2 and F2f which are recycled to the R - processing raie, processing plant. The. once-through gas cycle results in

Co = cost of plant for a ten-day processing cycle, the purchase of a large amount of F2, H2, and HF and in the generation of a significant volume of radioactive R - processing rate for a ten-day processing cycle. 0 wastes. The second method, however, results in the

purchase of only minor amounts of HF and H2 and We believe that this relationship can be used for produces only a small quantity of radioactive waste. processing cycle times of about 3 to 37 days. However, The princip;! fission product activity in the process for process cycle times longer than 37 days (a proc- off-gas is iodine, although small amounts of bromine, 184

krypton, xenon, and volatile noble and seminoble metal before the solution is evaporated to produce a solid fluorides are also present. waste residue. Evaporation is carried out in the waste Oace-tkroqgb. gas cycle. As shown in Fig. 153, container, which has a diameter of 2 1t ar.d a length of hydrogen and HF are collected from the plant off-gas 10 ft. This is the largest wast* container presently

streams resulting from UF6 reduction, hydroftuorina- considered for interment in a salt rune. The aqueous tion of bismuth, and hydrogen sparging. The combined condensate produced by evaporation of the waste is HF-Hj stream enters a caustic scrubber, where it is recycled to produce additional 10 Af KOH solution. contacted with an aqueous KOH solution for removal The hydrogen stream leaving the scrubber is assumed 3 of HF, HI, and HBr. It wa& assumed that 135 ft of 10 to contain low concentrations of SeF6 and TeF&. The

M KOH solution would be recirculated through the gas is passed through a dryer, an A1203 bed fc;

scrubber for 100 hr and that the KOH concentration sorption of SeF6 and TeF6, and a charcoal bed for would be reduced to 0.5 M during this period. The heat retention of noble gases. About 103 scfim of hydrogen generation rate in the scrubber solution after 100 hr is discharged lo the stack. vould be about 153 kW, and the solution would be This off-gas treatment method results in the produc­ held for an additional 400 hr for fission product decay tion of 489 kg of solid waste per day and requires that

0RKL-PV6 71-9553A

Hg TO DRYER AlgO, CHARCOAL HSTAC K

Kg FROM SPACING KOH H2O KOH MAKEUP Hg-HF FROM n- HYDROFLUORtNATORS KOH SCRUBBER KOH 5 RESERVOIR FUEL SALT rT^ ^ n KOH-KF-KI -n WASTE CAN + «* UFe-UF4 REDUCTION EVAPORATE TO SOLID FUEL SALT lb RESIDUE

ONCE-THROUGH 6AS CYCLE

Hg FROM SPARGING Hg-HF H2 TO I 5i-» DRYER •• ' »| A CHARCOAL Hg-HF FROM f~~ STACK H RECYCLE HYPROFLUORINATORS \ t.H~l r~i^_ . L_ 2 •KOH TO SPARGING F 1 r~i 1 ^^TO CONDENSER CONDENSER HgO SCRUBBEKOH R KOH u RUBBER I KOH MAKEUP Hg-HF HF Hz KOH ,r~u—I RESERVOIR KOH-KF-KI HF RECYCLE n TO HYDRO- WASTE CAN FLU0RINATORS EVAPORATE TO SOLID FUEL SALT HF HF FLUORINE RESIDUE

+ UF4 n DISTILLATION PLANT UF,-UF4 REDUCTION

FUEL SALT Fg RECYaE TO FLUORINATORS Fg-UF, GAS RECYaE SYSTEM

Fig. 15 J. Alternate methods foe treating otT-guw in an sfSBR procmiaa plant. „,„-•- *m&*m<0*m mem

185

105 waste cans be stored annually in a salt min*. end of this perkx\ the KOH concentration will have Approximately 66 kg of fluorine, 102 kg of HF, and 41 been reduced to 0.5 M, and the steady-state heat kg of hydrogen would be required dairy. generation rate in the solution will be 210 kW. The

Recycle of H2 and F2 via electrolysis. In this off-gas solution would be held for 45 days for fission product treatment method, hydrogen and HF are collected from decay before it is evaporated to produce a soBd waste. the various off-gas streams in the process. The mixture The solid waste production rate is only 9.7 kg/day, and is compressed o a pressure of about 2 atm and chilled only 2.1 containers having a diameter of 2 ft and a to a temperature of — 40°C to condense the bulk of the length of 10 ft would b« filled annually. HF. The liquid HF is distilled at essentially total reflux The hydrogen stream leaving the caustic scrubber is to separate volatile fission product fluorides (principally dried and recycled to the processing plant. About 5%

HI, HBr, SeF6, and TeF6). About 70 kg of HF is (05 scfm) of the hydrogen is discarded through an electrolyzed per day in a remotely operated fluorine Alj03 bed (for removal of SeF6 and TeF«) and a plant in order to produce the hydrogen and fluorine charcoal bed (for retention of noble gases). Tins oif-gas that are required for plant operation. The remaining HF treatment system requires the purchase of only 1.4 kg is recycled to the plant, where it is used principally for of hydrogen and 13.4 kg of HF per day. hydrofhiorination of bismuth streams couiaining dis­ Comparison of -osls for off-ga* treatment Costs solved metals. associated with the operation of the two off-gas The hydrogen stream leaving the HF condensation treatment methods were determined by calculating the and distillation operations will contain most of the capital equipment and operating charges for each. fission product activity in the initial H2-HF stream and Results of these calculations are summarize 1 in Table a small amount of HF. This gas stream is contacted with 15.4 for a 1000-MWXe) MSBR that is processed on a nz aqueous KOH solution to remove IiF, HI, and HBr. ten-day cycle. The contribution to the fuel cycle cost it is assumed that 20 ft3 of 10 M KOH solution will be for the once-through gas cycle is about 0.11 rmll/kWhr, recirculated through the scrubber for 34 days. At the while the cost for the treatment system resulting in

Table 15.4. Fud cycte cost tXHiuiwfom for two >»etf>ods of treaty {HOcespmnnMSBR|Hocemgpbat Reactor power = 1000 MW(c) Plant factor = 80%

Fad cycle cost (mifls/kWhr) Once-through gu cycle Gas recycle Waste disposal charges Waste containers 0.0485 0.0009 Carriers 0.0U22 0.0004 Shipping C.00S0 0.0001 Salt mine storage Q.QQ4S 0.0001 0.0602 00015 Chemicals and interest on capital equipment KOH tanks 0.0124 0.0013 Fluorin* plant 00196 Fluorine 0.0304 Hydrogen 0.0055 0.0002 Hydrogen fluoride 0.0026 0.0005 Potassturb hydroxide 0.0038 0.000! HF distillation equipment 0.0007 0.0547 0.0224 Total 0.11 0.024 186 almost complete recycfe is only 0.024 mill/kWhr. The tor. The elements in the second group will remain in the higher cost for the once-through gas cycle is due salt and wili be extracted into bismuth in the protac­ i primarily to the cost of disposing of a relatively large tinium isolation system. If he removal of 1% of the quantity of solid waste and to the purchase of fluorine. noble metals from the holdup volume occurs with a The most significant cost for the gas recycle method is residence time of 1 min, the heat generation in the amortization of the remote fluorine plant, which has a processing plant will be increased by 200 kW, with the

direct cost of $1,005 million. In making the cost bulk of the heat being generated in the UF6 recovery estimate, capital costs were amortized at 13.7%/year. system. About the same heat generation rate would Salt mine storage charges4 were assumed to be $300 per result if 10% of the noble metals reached the processing waste container, which is the minimum interment plant after a one-day holdup or if 20% reached the charge. Based on this comparison, the gas recycle plant after a ten-day holdup. method was saected for use in the MSBR fuel The heat generated by the halogens (Br and I) in the reprocessing plant. processing plant will depend upon both the halogen removal time and the noble-metal removal time since 153 EFFECT OF NOBLE-METAL AND HALOGEN halogens are produced by the decay of some noble REMOVAL TIMES ON THE HEAT GENERATION metals. If the noble metals are removed from the fuel RATE IN AN MSBR PROCESSING PLANT salt on a very short cycle., their daughters are prevented from entering the fuel salt and thus will not reach the M.J.BeD L.E.McNeese processing plant. The heat generation rate resulting The thermal power that will be generated in an MSBR from the decay of halogen fission produces is shown in processing plant by decay of the noble-metal fission Fig. 153. An effective noble-metal removal time of 0.1 products will depend on the residence time of these day is believed to be reasonable for the present elements in ait primary reactor system and the frac­ flowsheet. This would result in a heat generation rate of tion? of these elements accompanying the fuel salt to 210 kW for the halogens for a halogen removal time of the processing plant. We have performed a series of ten days or 520 kW for a removal time of three days. calculations in which tKe noble metals were assumed to For a noble-metal residence time in the holdup volume be transferred from the fuel salt, on a 50-sec cycle, into as long as one year, the halogen thermal power would a holdup volume having a residence time ranging from 1 be increased by only 60% over that for a 0.1-day sec to 1 year. The holdup volume was assumed to be in residence time. contact with fuel salt so that materials produced by the decay of noble metals could return to the fuel salt if 15.4 LONG-TERM DISPOSAL these materials were not noble metals. The model is OF MSBR WASTES sufficiently general that the holdup volume could represent noble metals associated with circulating gas M. J. BeO bubbles, a stagnant film of noble metals in a pump A recent study5 has b. en made of the long-term tank, or noble metals deposited on graphite and metal hazard associated with higiv !cvs! "^active wastes surfaces. The residual thermal power of the noble produced by nuclear reactors operating on the enriched metals leaving the holdup volume is shown in Fig. IS.4 23SU, uranium-239Pu, and thorium-2"U fuel cycles. as a function of residence time in the holdup volume. In this investigation, the reference MSBR was assumed The residual thermal power is defined as the integral, to be typical of the thorium-2 33U fuel cycle. It was over all time of the instantaneous heat generation rate found that the ingestion hazards represented by the for all isotopes leaving the holdup volume. Tin noble high-level wastes produced by the three fcAl cycles are metals wer* divided into two groups: those that form quite similar after comparable periods of decay. These stable volatile fluorides (As, Se, Nb Mo, Tc, Ru, Sb, ; high-level wastes were assumed to include all fission and Te) and those that do not (Rh, Pd, and Ag). products produced by the fuel eye'? and, in the case of Element, in the first group are assumed to be com­ 23S 239 the U and uranium- Pu fuel cycles, to include pletely removed from the salt in the primary ftuorina-

5. M. J. Bell and R. S. Dillon, The Long Term Hazard of 4. Staff of the Oak Ridge National Laboratory, Siting of Pud Radioactive Wastes Produced by the Enriched Uranium, Pu- Reprocessing Plants and Waste Management Facilities, ORNL"8<7, -and 2i3UThorium Pud Cycles, ORNL-TM-3548 (in 4451 (Jolv 1970), pp. 6-44-6-47. pren). 187

10s «• 10* HOLO-UP roe (SK>

F«. 15.4. Residual thermit power of noble metals as a iatfce system.

ORNL-OHG 71-2973* the plant, and that afl of the transuranium botopes and 1.0 1 1 1 their daughters would be present in the waste. The i removal times for the transuranhim elements were 0.5 I assumed to be ten days except in the case of neptu­

.NOBLE ME TAL REMOVAL nium, which was assumed to have a removal time of 16 t iRHt Hi W t* years. £ 0.2 The volume of water required to dilute the three 2 types of high-level wastes to the radioactivity concen­ tration guide values for continuous ingestion in unre­ 1 o-i f ^ 1 stricted areas is shown in Table 153 for wastes of ID X 0/-M *\ various ages. Also shown for comparison are the 0.05 volumes of water required to dilute comparable quanti­ s ties of (1) uranium ore tailings and (2) material

50 sm: containing uranium and thorhim at concentrations equal to their respective average concentrations in the 0.02 earth's crust. The quantities of these mzteials used in the comparison were assumed to be those that would 0.01 occupy the same volume as the high-level waste and 5 K) 20 50 WO TALOGEN REMOVAL TIME (days) associated salt and shale in the proposed Federal salt mine repository. Wastes aged 300 years would present Fkj. 153. Effect of halogen and noble-metal remoral times an ingestion hazard similar to that from uranium ore on the thermal power of the halogen fission products. tailings, and wastes aged 10,000 years would present a hazard about one order of magnitude greater than that associated with naturally occurring uranium and tho­ 03% of the uranium and phitonhim and 100% of other rium at their average concentrations in the earth's crust. transuranium isotopes and their daughters present in The study identified two potential problems relating the spent fuel at the time of chemical processing (ISO to the MSBR fuel cycle, as envisioned at the present days after discharge for the "5 U fuel and 90 days after time. As a result of the inefficient use of relatively discharge for the "*Pu fuel). In the case of the MSBR inexpensive thorium in the present MSBR concept, the it was assumed that the thorium in the waste salt would mass of wastes produced per MWXe) by an MSBR is not be recovered, that 03% of the reactor uranium substantially greater than the masses of waste produced inventory would be discarded over the 30-year life of by the other reactor types. Abo, MSBR * astes aged one 1*8

TaMe 153. V< of water (in m3) potewisay i nntiaaiaatti to for iofsoliM • MHCsliictei SK« (10CF1UA, Table n, 2) ay from 33J00O MUM of exponas of 23$U.239rV 133 u 2i> X 108 m3 = vohnne of water required to reduce ingestion hazard of the corresponding amount of uranium ore (0.17% U). 1.1 X 107 m3 = vohmie of water thfct results front dissolving the salt required to store waste equivalent to 33,000 BiWd exposure to * terminal concentration of 500 ppra. 1.0? X 10* m3 = approximate vohnne of water required to reduce ingestion hazard potential of the corresponding *-*' -at of earth containing naturally occurring uranium plus thorium in equilibrium with their daughters at the average concentration in the earth's crust.

Age of waste 235. 233 (years) "W If

30 1.26xi011(9°Sv) 7.22 x 1010 (90&> 2.11 X lO'^Sr) 100 2.24 X 1010 (90Sr) 1.32 X 1010 (9CSr) 3.75 > 1010 (^Sr) 300 2.00 X 108 (9°Sr) 3.93 x 108(24IAm) 3.76 X 108 (^Sr) 1,000 l-55X107(24,Am) 1.C9X 10*(M,Am) 4.72 X 10* (223Ra and 228Ra) 3,000 6.53 X 106 (243Ani) 224 X 107 (243Am) 5.06 X 10*(223Raand228Ra) 10.000 4.26 X 10* (239Pu) 1.26 X 107 (243Am) 9.34 X 10* (22*Ra) 3OJ000 2.44 X 10* (239Pu) 6.88 X 10* (239P») 2.2 X 107 (22*Ra; lOOjOOO 2.14 X 10* ("*Ra) 5.74 A 10* (22*Ri) 4.45 X l07(22Va) 300,000 2.38 X 10*("*Ra) 5.8! X 10* (22*Ra) 4.68 X 107 (226Ra) 1,000,000 I-58X10*(I291) 2.03 X 10* (,29I) 9.42 X 10* (22*Ra) 3,000,000 9.93 X 10s (,29I) 9.53 X 10s (,29I) 1.80 X 10* (228Ra) 10,000,000 5.28 X 10S(,29I) 4.88 X 10S(,29D 1.56 X 10* (228Ra) s 129 228 30,000,000 2.57 X 10s (l29D 2.38 x 10 ( I) 1.20 X 10* ( Ra)

'Reference rVR fueled with 33% enriched uranium, operated at a specific power of 30 MW per mein ton of heavy metal charged to reactor. Processing losses of %% of uranium and phitctuum to waste are assumed. *AI reference oxide LMFBR mixed core and blankets fueled with LWR discharge phitonium and diffusion plant tain. Average specific power of blend is 58.2 MW per metric ton of heavy metal charged to reactor. Froceacmg tones of %% of uranium and plutonium to waste are assumed. 'Reference MSBR with continuous protactinium isolation on a ten-day cycle and rare-earth removal by the metal transfer process. Thorium is discarded on a 4200-day cycle, and %% of the uranium inventory in the reactor is assumed to be lost to waste over a 30-year plant life.

millioit years or more have a greater ingestion hazard of 22*Ra, a daughter of 238Pu. The isotope 238Pu associated with them than other waste types, princi­ exists in MSBR wastes in substantial concentrations as a pally as the result of radioactivity from 232Th daugh­ result of the long removal time for neptunium and the ters. Both of these problems can be alleviated by short removal time for phitonium in the present miking more efficient use of thorium in the fuel cycle, processijig scheme. The amount of 2 38Pu in the MSBR which is, at present, utilized with an efficiency of only wastes coulU be reduced by removing neptunium more 13.7%. We are investigating processing schemes that can efficiently or by use of a processing scheme that wcula increase the thorium utilization to greater than 90% and allow ptutonium to remain in the fuel salt and be thus eliminate these problems. consumed by neutron capture. Both of these possi­ The study also revealed that a greater ingestion hazard bilities ar* being considered a» improvements to the is associated with MSBR wastes during the period present processing flowsheet. 30,000 to 1 million years as the result of the presence 189

15.5 AVAILABILITY OF NATURAL known world reserves of beryDnirj, fluorine, and RESOURCES REQUIRED FOR bismuth are being rapidly depleted by non-MSBR r?es MOLTEN5ALT BREEDER REACTORS and are expected to be exhausted before the end c'the century. Ample beryQhnn resources (in the form of M.J.Ben bertrandite) and fluorine (in the form of phosphate A study has been made of published data on the rock> exist; however, an improved mining technology availability of and future demand for natural resources will be required to make recovery of these materials of special importance to the MSBR program.6 Materials economical. Bismuth resources are limited by the considered in the survey included the constituents of demand for lead, copper, and zinc ores from which coolant an.i fuel salts, HasteUoy N, and materials bismuth is recovered as a by-product. In order to satisfy required for construction and operation of a chemical the cumulative world demand through the year 2000, it processing plant. Table 15.6 presents the cumulative is necessary that new base metal ores be developed and demand for a number of materials through the year that the technology for recovering bismuth during '.he 2000, compares the requirements of the assumed MSBR refining of copper and zinc ores be improved. economy with those of the rest of the world, and Ores from which thoria can be recorded for $10/l> compares the world demand with world reserves ?nd wiO be available well into the next century. Large estimated world resources of these materials. The reserves of higher-priced thoria are aho available. MSR demands for ail materials, with the exception of thorium and hafnium, comprise only a small fraction of the world demand for these l^aieriab and will not 6. M. J. Bell, The AvaSabiity of Natunt Resources for require the development of new industries for the sole Motter^Salt Breeder Reactors, ORNL-TM-3S63 (in pies). purpose of sustaining an MSBR economy. 190

TaMelS*. wodl forii iteriab over the period 1968-2000

Cumulative MSBR cnmnlatm: World cumulative Curr.ulafrre MSBR demand world demand desasd for the demand for the world demand Element as percentage of as percentage of period 198S-2000 period 1968-2000* as percentage of world demand world resources'plus (tons) (tons) world reserves world reserves

Fuel salt Li 7 J X 103 2.7-3 J X 10s 2-3 36-44 d Bee 2.1 x 103 3.0-4.3 X 104 5-7 250-360 1.9-2.7 Th/ 4.0 X 10* 2.3-8.4 X 104 A* 4.S-16 1.7-6.3 F* 42 X 104 1.2-1.4 X 108 0.O3-O.04 500-600 180-210 HasteBoyN Ni 2.5 X 10$ 2.4-2.9 X 107 0-8-1.0 32-39 d Mo 33 X 10* 42-S.O X 10* 0.8-0.9 78-93 d a 23 X 104 0.9-1.1 X 10* 0.02 11-14 d re 6.5 X 103 1.7-2.1 X 1010 <10^ 17-21 3-4 Mn 6.5 X 10* 3.9- 6X 10* <10"5 53-63 2-3 ri 1.6 X 103 1.9-4.4 X 106 0.O4-O.08 1.2-2.9 d Nb 3 2 X 102 2.7-4.0 X 10s 0.O8-O.12 2.7-4.0 d Hf 32 X 10* 1.9-2.9 X 103 11-17 0.6-0.9 d Other Bi 52 X 103 1.4-1.8 X I0$ 2.9-3.7 140-180 78-100 B 1.5 X 104 M-1.8 X 107 0.O8-O.1 20-25 d

•U.S. Bureau of Mines, Mineral Facts and Problem, Bulletin 650,1970 ed-, U.S. Govt. Printing Office. ^Reserves are known materials that may or may not be completely explored but may be quantitatively estimated; considered to be economically exploitable at the time of ti»e estimate. cResources are materials other than reserves that may be ultimately exploitable; these include undiscovered but geologically predicted deposits similar to presentreserves a s well as known deposits whose exploitation awaits more favorable economic or technologic conditions. ''Quantitative estimates of world resources of these elements are not available. 'Beryllium resources include deposit, containing at least 1% equivalent beryl (0.1% BeO).

'Thoriumreserves an d potential resources recoverable at $10 va pound of Th02. tRatio baseu on high range of forecast world cumulative dctnand.

*Fluerinereserves and resources of ores containing u least 35% CaF2 or equivalent value in fluorspar and metallic sulfides. HNtWM

16. Processing Chemistry

L. M. Ferris

Studies relating to the metal transfer process1 *2 for Work done at Argonne National Laboratory3 with die removal of nre-eartii and other fission products LiCl-LiF solutions indicated diat high hthhim and from MSBR fuel salt were continued. Included in this bismuth concentrations (up to 0.1 mole %) might be work were measurements of the equilibrium distri­ expected in LiCI tint is in equilibrium with htfaram- bution of lithium and bismuth between liquid Li-Bi bismuth solutions in winch the lithium concentration is aDoys and molten LiCI, and of die mutual solubilities of 5 to 50 at. %. Concentrations of tins magnitude could thorium and selected rare earths in liquid bismuth. The have a significant effect on the performance of the equilibrium precipitation of Pa2Os from MSBR fuel metal transfer process. Consequently, we have initiated salt by sparging with HF-H20-H2-Ar gas mixtures was a study of the equilibrium distribution of h'thhim and also studied. The effect of temperature on the solubility bismuth between molten liCl and fiqirid lithium- of Pa2Os in fuel salt that was also saturated with Th02 bismuth solutions. The results of tins study should aid was determined. Studies relating to the chemistry of in optimizing operating conditions for the metal fuel reconstitution were begun. The initial phase of this transfer process. work involves a study of the reaction of gaseous UF6 In tins study, LiCI containing less than 0.05 mole % with UF4 dissolved in MSBR fuel salt. UOH was equilibrated with various fitiuum-bisniuth solutions at 650°C. Thorium was added to the system 16.1 DISTRIBUTION OF LITHIUM AND BISMUTH in some cases to minimize the oxide and hydroxide BETWEEN LIQUID LTTHIUM-THORIUM BISMUTH concentrations in the salt. The apparatus and general ALLOYS AND MOLTEN Lid procedure have been described elsewhere.4 The equi­ librium lithium concentration in the salt phase was L. M. Ferris J. F. Land generally determined by removing a salt sample with a In the metal transfer process,1 *2 rare eardis and the stainless steel sampler, hydrolyzing the sample in water, attendant small amount of thorium would be stripped and measuring top amount of hydrogen evolved by a from the LiCI acceptor salt into lithium-bismuth so­ gas-chroinatognipnic procedure. Samples for bismuth lutions having lithium concentrations of 5 to 50 at. %. analysis were taken with quariz samplers. When the

1. L. E. McNeese, MSR Program Semiannu. Progr. Rep. Feb. 3. E J. Calms et at, Gahenic Cells with Fuxd&ft £fec 5c', 1970, ORNL-4548,p. 277. trofytes. ANL-7316 (November 1967), p. U9. 2. D. E. Ferguson and Staff, Chem. Technot. Dtv. Arum, 4. L. M. Ferns, J. C. ftfaifen.J , J. UwraiK*, F. J Smith, and Progr. Rep. Mar. 31.1971, ORNL4682, p. 2. E. D. Nocneara, /. fnorg. NucL Chem. 32,20t* (1974)1

191

•'-:>.\ 192 bismuth concentration in the salt was greater than previous work done at Argonnc National Laboratory3,5 about 100 the metal phase. In those cases where bismuth will be less than 1 wt ppm in LiG that is in fcoth lithium ard bismuth analyses of the salt were equilibrium with Li-Bi (5-95 at. %), which is the node, the Li/Bi atom ratio in the dissolved species was composition of the alloy proposed for stripping the about 3. Thus, the dramatic increase in the equilibrium trivalent rare earths and thorium from the LiG in the concentrations of lithium and bismuth in the salt with metal transfer process.1'2 Lithium and bismuth dis­ increasing lithium concentrction in the metal phase solved in the LiG at these low concentrations should uppeart to be related to the simultaneous increase in not produce a deleterious effect on the performance of concentration it the metal phase of a saitlike species, this part of the metal transfer process. However, the such as Li5 ft, which has a high solubility in Lid. The present results indicate that the lithium and bismuth data given in Table 16.1 indicate that the presence of concentrations in the LiCl in contact with the divalent thorium in the metal phase had no measurable effect on rare-earth strip solution, Li-Bi (50-50 at. %), would bz the distribution of lithium and bismuth between the about 0.3 and 0.1 mole % respectively. These concen­ two phases. Mr.'surements have also been made of the trations are sufficiently high that a significant amount of lithium and bismuth (as much as 370 and 1110 soiubilities of pare bismuth arid of Li3Bi in molten LfCI. The preliminary results indicate that the solubility moles/day, respectively) will transfer from the lithium- of bismuth is about 0.1 wt ppm at 650°C, whereas the bismuth solution used to remove divalent rare earths solubility of Li3?Ji is about 0.3 mole %. The magnitude of the equilibrium lithium and bismuth concentrations in LiCl determined in this 5. M. S. Foster, C. E. Crouthamel, D. M. Gnien, and R. L. investigation is consistent with the limited amount of McBeth,/. Phys. Chem. 68(4), 980 (1964).

Table 16.1. EtwKbriiiin distribution of lithium and bismuth between molten LiCl and liquid Li-Th-Bi solutions at 650°C

Concentration in metal phase Lithium concentration in Bismuth concentration in Li/Bi E*

61a 1.09 24.9 0 21 ±8 126 ± 50 186 ±20 38 ± 4 3.4 ± 1.4 7* 1.20 26.8 0 30 ±7 184 ± 42 225 ±75 46 ± 15 4.0 ± 1.6 76 a '..85 36.2 750 U0 ±50 673 ± 300 74 • 1-90 36.8 0 176 *15 1080 ± 90 78 2.00 38.1 0 108 ± 16 662 ±96 1016 ±20 206 t 3 3.2 ± 0.5 74 b 2.09 39.1 0 210 t 40 1280 ±225 75 2-16 39.9 750J 220 ± 40 1340t 225 76 b 2J6 41.0 1300 298 ± 50 1820 ± 325 76c 2.52 43.8 1900 430 * 75 2620 ± 460 2.50 47.4 2500 525 ± 60 3210 ±340 3m2 3.00 48.2 0 4260 ± 460 864 ± 93 193

ORNL-OwG 71-9539A 16.2 MUTUAL SOLUBILITIES OF THORIUM 5000 AND RARE EARTHS IN LIQUID BISMUTH F. J. Smith C. T. Thompson J. F. Land 1 A Lithium-bismuth solutions having lithium concen­ / • trations of 5 to SO at. % will be used to strip thorium and rare earths from the LiCl acceptor salt in the metal transfer process.1,2 We have been determining the 2000 / f solubilities, both individual and mutual, of thorium and E • o. selected rare earths in lithium-bismuth solutions to help Q. f define optimum process conditions. Previously.6 we c studied the precipitation of thorium bismuthide from e solutions containing rare-earth metals and observed partitioning of lanthanum (initial concentration, ~1000 ~ 1000 pprn) between the liquid and solid phase(s) at tempera­ tures below about 5O0°C. The available data were z <-4i interpreted in terms of coprecipitation of lanthanum o -f and thorium bismuthides. Results obtained in our < current investigations of the mutual interaction* of o: r thorium and rare earths in lithium-bismuth solutions 500 / have led us to reevaluate our original work. Data o z ootained recently have confirmed the earlier obser­ o / vations but cannot be explained in terms of a co- U preupitatior model. The general behavior observed is 2 consistent with the formation of a compound con­ x taining a rare earth and thorium (possibly a bis­ muthide). The general reaction for the formation of such a compound would be: 200 / f Th + x Ln + y ?i = ThLn Bi i , • (Bi) (Bi) (liq) x y($0 id)

in which Ln denotes a lanthanide metal. A mole / • fraction solubility product can be written as / 100 *sp =ArTh^Ln^B,J (1) 10 20 30 40 50 LITHIUM CONCENTRATION Under the experimental conditions employed, the Ln IN Li-Bi ALLOY (at %) and Th concentrations were low; therefore, the mole fraction of bismuth was close to unity and the mole fraction solubility product can be dosely approximated Fig. 16.1. Eqwtibriam distribution of ithtam between mol­ x ten lid and f thhun-trismiith solutions at 650° C by K%p = NJhNln . The variation of Ksp with temperature would be expected to follow the usual relationship

!og KSVI = log (NThNLn*) = A + BIT (2) fron.' LiCI. It is not believed that transfer of these amounu of lithium and bismuth will cau?e difficulties with the present flowsheet, however, since the lithium will be available for the extraction of uranium and 6. F. J. Smith and C. T. Thompson, MSR fropam Semiannu. protactinium. Prop. Rep. Aug. 31,1969, ORNL-4449, p. 217. 194

In each of a set of experiments, 300 g of bismuth trations in each experiment are in excellent agreement containing the equivalent of about 2000 ppm of rare with the published7 values for the solubility of thorium earth (either La or Nd) and about 4000 ppm of thorium in liquid bismuth. Similarly, as the temperature was was equilibrated for at least 8 hr at several temperatures lowered, the lanthanum concentration in the liquid between 750 and 300°C. At the end of each equili­ remained at its original value until some temperature bration period, a filtered sample of the liquid phase was below 550°C was reaeheo.; then i decreased regularly removed for analysis. The experiments were initiated by with decreasing temperature (Fig. J 6.2). The lanthanum heating the system to about 750°C, where both the behavior in each experiment was identical. The equi­ thorium and the rare-earth metal were soluble. The librium lanthanum concentrations in the liquid were temperature of the system was then progressively much lower than the reported solubility values.8'9 On lowered to about 300°C; finally, the temperature was the basis of the lanthanum results, we postulate the returned, in sxeps, to 750°C. The results from one of formation of a La- and Th-containing solid phase that our recent experiments (LA-3), along with those from a has a very low solubility in Uquid bismuth. The results previous* experiment (LA-2), are shown in Fig. 16.2. obtained for thorium indicate that there was sufficient Agreement among the results cf these two experiments thorium present in the system to satisfy the solubility is obvious. As the temperature of the system was product cf the compound containing Jhe rare earth and lowered, the thorium concentration in the liquid thorium and to saturate the system with thorium remained at its original value until about 650°C was bismuthide. In this case, the maximum thorium concen­ reached. Below 650°C, the thorium concentration in tration in solution at a given temperature is determined the liquid decreased regularly with decreasing temper­ by the solubility of thorium in bismuth. The variation ature (Fig. 16.2). The equilibrium thorium concen­ of thorium solubility in bismuth with temperature has been shown: to follow the usual relationship

ORW.-0MG 7I-7868A k>gN =A'*B'/T. TUIPERATURE rC» Th (3) 700 650 6O0 550 500 450 4O0 350 4 « T ...--,, - -, , ,-p — T|- 'I T i ji i • i '! Substitution of Eq. (3) into Eq. (2) yields 1 —INITIAL CONCENTRATION s I • LO, EXPT LA-2 O La, EXPT LA-3 1 x\osNLi--A" + B"/T, i a Th, EXPT LA-2 "**"VA A Th. EXPT LA-3

1 indicating that a plot of the logarithm of the lanthanum -a. ft ^lM/^w 1 •»SL concentration in titc bismuth solution vs 1/7 should be o E linear. As seen in F:g. 16.2, lanthanum behaved as a. L£ « predicted. It should be not?d that a value of x cannot iio3 ^ ^ P i ^\^ be determined from data obtained in the manner outlined above if thorium bisnuthide is present as a \ k °\. second solid phase. z TW An experiment (Nd-6) with neodymium as the rare o \i l*_ < earth was conducted in the same manner as experiments £z 2 > e^ LA-2 and LA-3, and the results obtrined were similar to ui uz those obtained with lanthanum. In addition, an approx­ ° » imate value of x = 1 was obtained in an experiment ^ T ^ L (E-70) conducted entirely at 640°C. In this experiment, V\ neodymium was added to a thorium-bismuth solution, \ \ and the equilibrium concentrations in solution were A ^ determined after each addition. From Eq. (1), a plot of XV 10 If 42 13 14 15 16 17 «>floo/ . n K) 7. C. E. Schilling and L. M. Ferris, /. Less-Common Metah 20,155 (1970). Fij. 16-2. Mutual solubilities of kathaaain sad thorium in 8. V. I. Kober et al., Russ. J. Phys. Chem. 42,360 (1968). loaid bimmth sofationt. Excess solid thorium tmmuthide was 9. D. G. Schweitzer and J. R. Weeks, Tron- ASM 54, 185 present, Qxing the thorium concentration in solution. (1961). i

195

log Nj^ vs log JVNd was expected to be linear with a used. The equation for the ine in Fig. 16.3 is log slope of -x. Our data covc-ed only a limited range of *sp(Nd-Th) = 3-233 ~ 7285/7X°K). Assuming that x is concentrations, but the slope of the plot indicated x to also 1 for the La- and Th-containing solid phase, we = be about 1. A third experiment (Nd-7) was conducted obtain, from Fig. 16.2, log A*$p(La-Th) 2.410 — in an attempt to measure the solubility of the Nd- and 6480/7CK). 1 Th-containing solid in the absence of excess thorium In reference to the metal transfer process, »* the Ksp bismuthide. The solution initially contained about 1 wt values for both lanthanum and neodymium indicate % Nd and about 3500 ppm of Th. The temperature of that the desired thorium and rare-earth concentrations the system was varied between 500 and 700°C, and should be attainable in the lithium-bismuth strip so­ samples of the liquid phase were removed at selected lutions without precipitation of a rare-earth- and temperatures. Analyses of these samples showed that thorium-containing compound if the temperature of the both the thorium and neodymiuiri concentrations in the trivaient rare-earth strip solution Li-K (5-95 at %) is liquid were much lower than the solubilities of the kept at 600°C or higher. respective bismuthides. From these results, we assumed Using the data and interpretation given above, we that only one solid phase, a Nd- and Th-containing considered a scheme for removing rare earths from compound, was present. Assuming JC = 1. we calculated MSBR fuel salt that involved reductive extraction

the mole fraction solubility product Ksp = NJiiNjh, followed by selective precipitation of thorium bis­ using data from the three experiments involving neo- muthide. Rare-earth fission products would be ex­

dymium. The resulting log A"$p vs 1/7* plot is shown in tracted from fuei salt that is free of uranium and Fig. 163. As seen, the data yield the expected linear protactinium into bismuth that contains lithium and plot. It should be noted that agreement among all the thorium as reductants. If the extraction were conducted data cannot be obtained if values of x otbn than 1 are at 600°C, the thorium concentration in the bismuth leaving the extraction unit would be about 1800 wt ppm for the reference case of a 10004kfW(e) MSBR and

ONNL-OMG M-7867A a 25-day rare-earth removal cycle. The correspondmg TEMPERATURE PC} rare-earth concentration would be less than 10"* rook 700 650 600 550 500 450 400 4 fraction. Equilibrium cooling of the bismuth to 3S0°C I 1 — i n II - -ii "i 1 •1 ' i ' i EXPT. Nd-6. SOLUTION ALSO SATURATED would precipitate thorium bismuthide and decrease the \ WITH THORIUM BlSMUTHDE thorium concentration in solution to about 35 wt ppm. • EXTRAPOLATION OF DATA FROM Nd-6. - 5 I -—-— . EXPT. Nd-7. NO THORIUM BISMUTMOE No rare earths would precipitate because their concen­ \ PRESENT trations in solution would be too low to satisfy die JH— A EXPT. E-70 TEMPERATURE CONSTANT AT V 640 "C. AVERAGE OF 9 POKT5 WITH for the compound containing the rare earth and \J VARYMG Th/Nd RATIO M50LUT ON i thorium. For example, the AT$_ for the La-containing \ solid at 350°C is about lO-8 With a thorium concen­ \ h L - \ tration of 35 wt ppm (JV = 2.9 X !0~*), the T Th \ lanthanum concentration in solution could be as high as \ 3 X I0"4 mole fraction (about 240 wt ppm) without \ < precipitation of a La-containing solid. The supernatant solution resulting from the precipitation of thorium V bismuthide would be removed, and the dissolved species \ \ (Li, Th, and rare earths) would be .stripped, either by \ _ hydrofluorination or hydrochlorination, into a suitable '-alt phase for disposal. The clean bismuth would then \v~ i be used to dissolve the thorium bismuthide, more 1 \ thorium and lithium would be added, and the resulting A solution would be recycled to the reductive extraction unit. The thorium decontamination factor for the r \ conditions cited above wouid be about 100 but could 10 M >Z 13 44 45 46 U increased to about 1000 if the extraction were 40,Q00/ rno conducted at 750°C and the resulting bismuth solution were cooled to 300°C. The decontamination factor is Fig. I6J. Temperature dependence of the winlwUfi protect for the compound IfcNdBi,, in frnrid bwmrtli. not affected markedly by increasing the rare-earth 196 removal cycle to at least 100 days. The chief dis­ pressure respectively. If the ratio p^ Q/PHF * ^^ at advantage of the above scheme is the economic penalty some value A, Eq. (5) can be written, in logarithmic involved in the large lithium and thorium losses, about form, as 30 and IS kg/day, respectively, for the reference case. •oS^PaFs = 2 5 "fc^HF ~ Io*<*>« <*> 163 OXIDE PRECIPITATION STUDIES For a given value of A, a log-log plot of pcotactinium O. K. TaDent F. J. Smith concentration in the salt vs HF partial pressure should Studies in support of die development of oxide be linear with a slope of 2.5. If the gas present at precipitation processes for isolating protactinium and equilibrium contains hydrogen in addition to HF and uranium from MSBR fuel salt have been continued. H20, tetrapositive protactinium is produced according Previous work1 ° has shown that addition of oxide to a to the reaction salt solution containing Pa5* results in precipitafJQn of pure, or nearly pure, Pa20s and that Pa2Os can be PaF5(d) + % H:(g) = PaF4(d) + HF

would be treated with the appropriate HF-H20-H2 gas mixture to convert practically all of the protactinium to 5 Pa * and to precipitate a large fraction of the protac­ & = (8) ,/2 tinium as Pa20s without precipitating uranium oxide. *PaFsPH2 We have also determined the effect of temperature on

the solubility of Pa2Os in MSBR fuel salt that was The total protactinium concentration in the salt is saturated with both ThOj and NO. These measure­

ments aid in definmg the lowest protactinium concen­ /V + V ^Pa- PaF ^ PaF (9) trations attainable at a given temperature without 4 s thanfjn£ the uranium or thorium concentrations in the When P^Os is the solid phase at equilibrium, Nrtf is salt. defined by Eq. (5). Substitution of Eqs. (5) and (9) into Protactinium has been systematically precipitated Eq.(S) thus yields:

from molten LiF-BeF2-TriF4-UF4 solutions at about

600°C by equilibrating the salt with various HF-H 0-Ar 5/ 3/2 ,/2 2 G*=*Pafi.>* VHF- PHr and HF-H20-H2-Ar gas mixtures. The data obtained

,/2 with HF-H20-Ar gas mixtures were considered in terms -PHFPH2' <»<» of the equilibrium

Two experiments designed to yield values of Qx at 600°C have been completed. Each experiment was PaFs(d)+%H20(g)=y2Pa205(s)+5HF(g), (4)

initiated by loading 200gof UF BeF2-Th^ (72-16-12 343 for which ihe equilibrium quotient at a given tempera­ mole %), a weighed amount of U oxide, the 231 ture crji be written as equivalent of about 100 wt ppm of Pa, and 1 raCi of 333Pa tracer into a nickel vessel. After the system had been heated to 600°C, the salt was sparged for two PHF <2.= (5) days with HF-H2 (50-50 mole %) to dissolve the 5/2 PH20 AVaF, uranium and protactinium in the salt. After residual HF

and H2 had been removed by sparging with argon, In the above expressions, (d), (g), (s), N, and p denote filtered samples of the salt were taken for analysis. By dissolved species, gas, solid, mole fraction, and partial analysis, the initial uranium concentration in the salt was 0.288 ± 0.028 wt % (about 0.08 mole %) in 10. R. G. Ron, C. E. Bamberger, and C. F. Bacs, Jr., MSR experiment I and was 0.93 i 0,03 wt % (about 0.25 Program Semkmm. Prop. Rep. Aug 31,1970, ORNL-4622, molp. e %) in experiment II. The sslt was then sparged 92. with either an HF-H20-Ar or an HF H20-H2 Ar gas It. J. C. Maifcn, L. M. Ferris, and J. F. UadMSR Program mixture. A standardized aqueous HF-H 0 solution Semtmmu. Prop. Rep. Aug. 31,1970, ORNL-4622, p. 206. 2 (H 0/HF mole ratio = 3) was fed at a controlled rate to 12. J. C. Maflen and L. M. Ferris, MSR Prognm Semtawi. 2 Progr. Rep. Feb. 28.1971, ORNL4676, p. 24S. a heated vaporizer, using a Sage syringe pump with a 197

Tiflon syringe and piston. The vaporizer was a heated regularly with the partial pressure of HF in the gas cyfadricalry sh-ped 500-ml Mood vessel that had a mixture. A log-log plot of the protactinium concen­ gok!-plated cup in the bottom The HF-H20 solution tration vs j>||F b shown in Fig. lo.4. The protactinium was fed into the cup, where it was vaporized and then concentrations used in this plot were those obtained by was carried into the nickel reaction vessel by a stream gamma spectrometry, since this analytical method gave of argon or an Ar-H2 mixture. The argon and hydrogen what appeared to be the most accurate and self- flow rates were controlled using calibrated DP cefls. In consistent results. Increasing the UF4 coocentratkva aD cases, the .alt was sampled without measurably from 0 OS to 0.25 mole % had no measurable effect on changing the composition of the gas phase. In prelim­ the equilibrium protactinium concentrations- The slope inary experiments, in which samples of the salt were of the tine in Fig. 16.4 is 2.5; we interpret thai as removed periodically, it was shown that equilibrium confirmation that the equilibrium involved was that was attained in less than 16 far. AH data reported below given by Eq. (4). The equation of the Mae e log (wt were obtained by allowing at feast 16 hr for equHV ppm Pa) = 2.5 tog pgF + 4.870, from which we derive bration. Etch sample was first analyzed for protac­ N 2 5 ** T*F5 " - ** PRF ~ 1-6925. Since A = 3, we tinium by gamma spectrometry and then was submitted obtain (2,= 3.2 at 600°C. to the Analytical Chemistry Division for dcsolution and The uranium analyses of the salt, despite their analyses for 131Pa and 233U by the alpha-pufae-hoght considerable variation, support the contention that method. protactinium oxide was precipitated as a pore sold Data obtained at 600°C in the two experiments phase. However, we do not vet have sufficient data to outlined above are summarized in Table 16.2. As seen, define accurately the lowest protactinium concen­ when HF-H20-Ar gas mixtures were used, the equi­ trations attainable under given conditions without librium protactinium concentration m the salt varied precipitating uranium and thorium oxides. Our data

TaMeltU. (72-16-121

HF-B20-Ar or W-H^O-H^«

0.019 0 5.5 941 0.024 0 7.2 0.030 0 134) 0.031 0 13.4 10.7 0-241 0.040 0 19.4 159 0J92 0042 0 33.* 25.7 0.259 0.043 0 yj> 3i-2 0.174 0.043 0 *SA 202 0.199 n 0.047 0 37.5 364) 0.907 0050 0 44J 0.052 0 36.2 59J6 0.263 0.052 0 41.6 43.9 0J62 0055 0 66.1 714) 0.920 0.058 0 UJO 884) 0-937 0.063 0 nx> 71.5 0334 04)65 0 724) 5SJ 0.332 n 04)65 0 64.9 864) 0.977 0.070 0 69.0 58.5 0.282 OJ0212 0.101 10.4 048 OJ0227 0.0843 264 0X1340 0.140 49.5 0.19 0.0375 0.154 624) 0J0 198 indicate that at 600°C the protactinium concentration ORNL-cms 7i -9538A 100 can probably be reduced to about 5 wt ppm without 1 1 A the attendant precipitation of i.tatifn oxide. _• EXPT I; Nyp = 0.<3 6 A A _A EXPT 11 :N.— =0-25 When hydrogen was present in the gas mixture, the 9 c -ur4 A Q. equffibrium protactinhun concentration at a given value Q. of Pup was iigher than that obtained in die absence of 5 50 / / hydrogen (Table 16.2). We slmbute tins benavior to 5 ; the formation of Pa**, accordsof to Eq. (7). The values CO

of Q2 given in Table 16.2 were calculated, using Eq. z (10), from the data obtained with hydrogen present in y the gas mixture. Our average value of & = 0.2 at 600°C f is in good agreement with ife va?ue of about C5 •RATIO N / obtained by extrapolation of values given by i Bamberger, Ross, and Bees.13 '* * / 'Hie Mfabftty of Ft2Os m LiF-0eF2H>F4 (72-16-12 %) that was also saturated with ThOj and NK) IU M C0NCEN 1 determined over the temperature range 569 to 5 1 5 l\ 690°C The equilibrium involved was assumed to be /. og J %Ttf (d)+ViPa O (s) = PaF (d) + %Th0 (s), (11) or 4 I s $ 1 Q, 1 m / for 5 w

^VaF. 0.01 O02 0.05 0.1 s Ca (12) (otm) $ 4 HF *T.F4 '

The apparatus and general technique have been de­ wjr Hif HIaT4eF2-TV4 (72 14-12 i ;W4 scribed elsewhere.* knttaBy, 100 g of sah contammg vvAvKkmBF^O-AffwantaMa HjCHF about 10.5 wt ppm of 2iJ Pa and about lmCi of "3Pa •Mle ntio was 3. The riwifina tor me oztonwtppmH)

tracer ws hy&ofluoriasted at 650*C in a molybdenum *2^logpHF*4JnO. crucible to dissolve the protactJuium in the salt. After stripping residual HF and Ha from the system with pure

argon, sufficient Th02 (~!.2 g) was added to saturate the melt withThOj. About 0.4g of NK)(an oxidant) the alpha-piilse-height method. The wjreemem among was also added to ensure that the protactinium was in the analyses was generally good. the 5+ oxidation state.19 After an initial period of six The data obtained are summa.ized in Table 163 and days, duplicate filteredsample s of the salt were taken at are shown graplncaBy in Fig. 16.5 as a plot of the each of several temperatures. At least 20 hr was slowed logarithm of the protacthrcm concentration vs 1/7. The plot includes our previously reported12 values. The for the attainment of equilibrium at each temperature. least-squares equation for the line is log (wt ppm Pa9*) The samples v#5ie analyzed for protactinium by 233 = 19.4?! - 17890/7TK),wrakiibeq«vaJtnt tologCj counting the gamma raysemitte d by the Pa. Where 23, = 14.06 - 17890/TfK); the standard deviation of tog possible, the samples were also analyzed for Pa by Q3 u 03. At temperatures above 650*0, our values of

Q3 are in reasonable agreement with those determined by Ross, Bamberger, and Bees;1* however, our values are much lower than theirs at teinperatures below 13. C. E. BaWMipi, R. C. Row, aa4 C. F. Baes, Jr., Reactor 650°C.

Chew. Dtf Anm. Prop. Rep. May 31. 1971, ORNL4717, p. Values of 03 can abo be estimated by combining the It. quotients for the following two equilibria: 14. R. G. Row, C. E. Buaberger. ted C. F. Bacs, Jr., MS* Propmrn Semkmtu. frogr Rep. Feb. 28,1971, ORNL4676, p. 130. %UF4(d) + %Pa2Os(s)»PaF$(d) + %U02(ss), (13) 199

OK 71-9540* UF4(d) + ThO,(ss) = UOJCSS) + ThF4(d) . (14) TEMPERATURE C"C) In these expirssions, (ss) denotes TbO,JJOj solid 750 700 650 600 550 too solution. It is easily seen that log Q3 =k>sG,3-% log

0i4. Utilizing the values of Q, 3 determined by Mailen and Ferris12 at temperatures above 600°C and the toqCwtppn t\P+)=&.47i-mgQ/rirK} ls values of Ot4 reporred by Bamberger and Baes, we calculate values of Q* m the temperature range 600 to 75G*C that are within a factor of 3 of the values E obtained by our direct measurements. Both Qt 3 and

QXA were evaluated at AfUF4(d) - 0.0022 for the «n K lafekKJ. -TfcF« 10 (72-14-12 %)atTh02 < k K I- Z Ul io*e, 8 • salt i ro (WtpfW) OJ 562 0.014 0.06 • TM5 WORK 610 0.17 0J66 632 032 U 642 0.4S iJf 6SS 3.75 15 660 0.63 US i 675 4.95 19 act 690 4J60 IS 9J5 COO «5 RJO RL5 tf-O

f0^00/rw

*+ 165. 1M>$ • (72-16-12 ao**) iliOzawJMOi 16.4 CHFMBTRY OF FUEL RECONSTTTUTION II. R. Bennett

The current flowsheet2 for the fnuccsMug of MSBR 1 17 fuel involves removal of die uranium from the salt as Some ameago '' this concept was tested by i o UF* by fluorinatkn prior to isolation of protactinium gaseowUF.at600 CtoliF^rF4(5I-«9iiiole%) by reductive extraction and removal of rare earths by initially contained about 1 wt % UF4. The salt, die metal transfer process. The proposed fad re- was held in a akfcel vesael, was sparged wit] constitution method co nts in contacting, in the after the addition of UF*. AB of the UF* added to lis presence of hydrogen, the purified UF* with carrier salt system was absorbed by the salt; however, tar mawjaui was found to be almost entirely in the 4+ oxidation that contains some dissolved UF4. The expected sequence of reactions, which could occur almost samd- state even befcie hydrogen was admitted to the system. taneousry,B It was postulated that UF, was isJtiaty formed according to reaction (IS) and that the UF, was fery UF«tt) + UF4(d)*2UF5(d), 05)

2UF (d) + H,(g) = 2UF (d) + 2HF(g) s 4 (16) 16. L. E. McNscae ami C. D. Scott, RtcomtiiutkM Fmd by ReamttHg OF* Gm to UP* m m ORNL-1M-1051

2UF5(d) + Ni(s) = 2UF4(d) + NiF2(d) (H) ranged from 0.1 to G.2S g/min. Argon was admitted at a low flow rare at point B (fig. 16.6) at the same time We have begun a more comprehensive study of die that UF* was flowing into the reaction vessel. This chemistry involved in the fuel reconstitutjon step. Our argon flow was maintained after the UF« introduction initial goals were to establish the validity of the period until :he thermocouple and sparge tube had been stoidnometry of reaction (IS) and to find a suitable retracted to positions above the sah level. The system material for containing molten-salt solutions in which was dien left under argon for the desired period cf time uranium is present Li oxidation states higher than 4+. before the salt was sampled. Samples were taken by The experimental equipment is shown schematically inserting a cold graphite rod through the ball valve into in Rg. 16.6. The UF* generation system consisted of a the salt and withdrawn: 3 it rapidly. The sample was 14b UF* cylinder fitted with the appropriate control hydroryzed in phosphoric add, and the resultant valves and gages and a calibrated DP cell for the solution was analyzed for total uranium and U**. We accurate control of UF» flow rates. The entire assumed that uranium present in the salt in an generation system was wrapped with resistance heaters oxidation state other than 4+ was present as UFS, and and thermal insmatioa so that it could be maintained at thus on hydrolysis the fbttowmg reaction occurred: 65 to 70°C. The nickel reaction vessel, which 4 to the vessels used in our related studies, 2U5* = U#* + U* (18) nth %-m.-&mm ports for a thencowel and tube and a %-m.-dnm ball-valve sample port. Obviously, when all the uranium in the sat* is present in The general experimental procedure used was as ibt 5+ state, the U** concentration is one-half the total follows: Rrst, the UF* generation system was re­ uranium ccscentration. peatedly pHn»Lid and purged with UF« at about IS first series of experiments was initiated by prig hi order to remove argon fromth e ines and valves. 2.9 g of UF4 and 197.1 g of LiF-BeF2-TfeF4 Excess UF« was vented to NaF trap No. 1 (Fig. 16.6). (72-16-? 2 mole %) into a high-density, tngh-purity

ORNL-OWG 71-9542A

NoF TRAP NO.*

OP CELL © Ar —*>o- 65-TO-C I*-,

BALL-VALVE CAPILLARY SAMPLE PORT TUBEJ UF 65-WC 6t OR Ar NoF TRAPNa2

.a THERMOCOUPLE

MCKEL REACTION WELL-TYPE VESSEL FURNACE SPARGE TUBE MOLTEN SALT

in the of dw mctiN of ki Ffc. It*. UF«wffhUF4 201 graphite crucible, which was then sealed in the nickel during die 0.5-hr period in which UF* was being added reaction vessel under ergon and heated to 600°C. When to die system, or it was corroded according to die molten, the salt produced z pool about 2 in. deep. The following sequence of reactions: salt was then sparged with HF H7 (50-50 mole %) for about two days to ensure dissolution of the UF4 and to remove oxide from the system. The sparge tube used UF6(g) + UF4(d) = 2UFs(d), (15) for the hydrofluorinarjon was fabricated of a relatively low-density spectrographic-grade graphite. Analysis of 2UF$(d) • Cu($) = CuF2(d) * 2UF4(d) . (20) the salt after hydrofluorinatkn gave the expected 1.1 wt % uranium. With die system at 600°C, we attempted to introduce UF* gas into the system through the Despite die corrosion of die copper sparge tube, die graphite sparge tube, which extended to wstiss % in. of lesuiis of tins test strongly indicated Out the graphite the bottom of the reaction vessel. However, the UF4 crucible was inert, at least for a short time, to UF$ was quantitatively reduced to UF4 at the ir"et of the dissolved in a molten salt. tube, even though die temperature was 2O0°C or lower Even more convincing evidence for die stabnrty of at this point. Analysis of the salt after das attempt graphite to dissolved UF$ was obtained in tie final test showed diat tin uranium concentration in die salt was in this series. The salt from die prior test involving die still 1.1 wt%. copper sparge tube was left at 600°C under argon for Prior to a second test, die graphite sparge tube was about two days while we awaited analyses of tin replaced by one made of high-fired A1203. Then, five samples. Otce diese anatyns were available, die amount times die amount of UF« necessary to convert die of UF« necessary to convert tin 40% of the uranium uranium to UFS was fed to die system. Following die calculated to be present as UF4 to UF$ was admitted to addition, tin A1203 sparge tube was retracted to a die system through a gold sparge tube. Ike gold was position above die squid salt, and tin system was unaffected dining die 03-hr period required for tint maintained under an argon atmosphere for several hours addition of the UF*. After tin gold sparge tube had before die salt was sampled. Analyses showed that al of been retracted, die salt was left under argon for about 6 the uranium added to die system was prefect in die salt hr before it was sampled. Analyses continued not only (die uranium concentration had increased from 1.1 to that afl of the uranium added as UF* had been absorbed (die total uranhim concentration was \2Z wt 5.1 wt %), but littie, if any, UFS was produced. The AI2Q) sparge tube had been severely corroded. % compared with die expected 12.5%) but also tint on* The AI2O3 sparge tube was replaced by ore mad: of jranium was present in the salt, within aaafytical uncertainty, as UF (the U** concentration in tire add copper, and die amount of UF* required to convert a0 S of die UF in die salt to UF was introduced. The was equivalent to 637% U** in the salt). These results 4 5 strongly indicate that die UF concentration in the suit copper sparge tube was dm retracted so *£at it was not S in contact witii die molten salt, and die system was had not been reduced m die two-day period between again maintained under argon tor several hours before die tests with die copper and gold sparge tubes, die sah was sampled. Analyses of ihz samples showed puviding additional confirmation tint graphite h 'able to UF, dnaohed in molten UF-Bcc, ThF (72-16-12 tint aO of die uranium introduced as UF* had been 4 mole %). These results also support the ttokhiomrtry absorbed in die salt; die total uranium concentration of reaction (15) and suggest dnt gold would be a was i?ow 9.63 wt %. About 60% of die uranium was suitable material for tin containment of dbsohed UF . present as UF , and the Cu/Uf ratio was about l.The S S 4 Consequentiy, we are prawning an experiment in gold copper sparge tube was badly corroded. Eitiier die apparatus not only to evaluate me long" term stabSty of copper had reacted witii UF* according to die reaction gold to db»obed UFS but also to obtain further confirmation of tin stoichkmietry of reaction(15) . UF«(g) • Cu(s) = UF4(d) + CuF*(d) (19) 17. Engineering Development of Processing Operations

L. £. McNeese

Studfes related to die development of a number of was continued. Studies of a salt-bismudi interface processing operations were continued during this report detector for use in salt-metal contactors were also period. Additional information on die behavior of continued. Etfrium during metal transfer experiment MTE-2 was developed. The data arc consistent widi recendy ob­ 17.1 LITHIUM TRANSFER DURING METAL tained data on die concentration of fitiuum in LiCl diat TRANSFER EXPERIMENT MTE-2 sin eqofibrium wnii Etimim-bismuth solutions. A new E. L. Youngblood L. E. McNeese experiment (MTE-2B) is under way to study further die transfer of Ednum from a Li-Bi solution containing Additional analytical results were obtained for die ftfasum at die concentration proposed for extracting concentration of fiduum in die Li-Bi solution used for trivalent rare earths from htinim chloride (S at %). extracting rare eartiis from lithium chloride in metal Srodfes on mechanically agitated salt-metal conuctcn, transfer experiment MTE-2, which was completed whkh are being developed « an alternative to packed previously. During die experiment,1 die hdiium con­ columns, were also continued during tins period. The centration decreased from an initial value of 035 to design of die third engineering experiment for develop­ 0.18 mole fraction after about 570 titers of lithium ment of die metal transfer process (MTE-3) has been chloride had been contacted with die Li-Bi solution (see completed, and most of die equipment has been Fig. 17.1). Only a small fraction of dm decrease can be fabricated. Installation of die completed equipment accounted for by the reaction of rare earths witti items is in progress. Mass transfer experiments were Stimuli. The major portion of die decrease is believed begun in which die rate of transfer of zirconium from to be associated with the circulation of die hduum molten salt to bismuth was measured during die chloride since Mttie or no decrease occurred during countercurrert contact of salt and bsmum in a packed periods in which UCl was not circulated. Recently, it column. Equations were developed for predicting die has been determined tiiat die equilibrium concentra­ ate of heat generation in a frozen-wall fluorinator tiiat tions of idaum and bismuti! in lithium chloride in uses radio-frequency induction heating. Calculations contact with btirium-bisiniidi solutions are appreciable were carried out for predicting die performance of continuous fluorinatofs. The installation of equipment for en •neeriag studies on uranium oxide precipitation was completed, and two experiments were carried out. 1. E. L YoonfMood and '„ E. McNee«c, HSR Propfm work on die design of a processing materials test stai.d Semiaum. Prop. Rep. Feb. 28. 1971. ORNL-4676, pp. and die moryboenum reductive extraction equipment M9-53.

202 203

ORNL-OWG 71-95-16A 0.40 whet-? I • 1 F .. = volume of the bismuth-fithium solution, i p Li > • i 1 moles, 2 0.35 9B A • ~1j i j PREDICTED Li jt , = concenuatian of lithium in lithium- » Li Bi) ! CONCENTRATION bismuth solution, mole fraction, o • t 1 0.3C 4 t = time, min, • •• /= fractional approach to equilibrium ob­ & 0.25 ^N * s tained at the UCl-Li-Bi interface,

[*-.! •"** F~ lithium chloride circulation rate, moles/ ^^ -1 0.20 M. mifl, •i * LHLICI)= concentration of lithium in lithium chlo­ ride in equilibrium w*th Lt-Bi solution, 0.15 i 1 «0 20C 300 400 500 600 mole fraction, VOLUME OF LiCI PUMPED Miters)

RL% - rate at winch btbiun is removed from the Li-Bi solution by reaction with LaCt , F% 17.1. Variatioa of •i the I>ti 3 foriemovHg fro* Lid rooks/mm. •fIE-2.

In the above relation, it has been assumed that essentially ali of the KthUim was removed from the htbjurn chloride by extraction into the man. bismuth and that they increase markedly as the lithium concen­ pool in the experiment. Equation (1) was substituted tration in the metal phase b increased (see Sect. 15). into Eq. (2), and the resulting equation was solved A mathematical analysis has been carried out using numerically for various values of /in order to determine the recently obtained data on the equilibrium titnium the value that best represented die data. The curve concentration in lithium chloride in contact with Li-Bi shown in Fig. 17.1, which resulted from an/value of solutions. These data can be represented by the 037, is in good agreement with the measured fathium relation: concentration in the Li-Si solution during the experi­ ment, and the value of /is in reasonable agreemer* with

= s.si the value of 0.2 reported earlier, based on the rate of *Li(LiCI) °-2278 *Li(Bi) (0 accumulation of lanthanum and neodymhim m me Li-Bi solution. It should be observed that essentially no where transfer of lithium occurred until after about SO liters *Li(LiCi) = concentration of lithium in lithium chlo­ of lithium chloride had been circulated; at this time, ride, mole fraction, operation of a gas sparge tube in the Li-Bi container was initiated. Similar behavior was observed in deleriuining = concentration of lithium in fithhim- 'Li(Bi) the rate of accumulation of lanthanum and neodymium bismuth solution, mole fraction. in the Li-Bi solution during this period in that essen- In experiment MTE-2, lithium would have been re­ tially no accumulation was observed until the sparge moved from the HUnum-bismuth solution as a result of tube was activated. The agreement of the measured (1) circulation of the UQ and (2) extraction of lithium concentration with the predicted values was lest materials into the tithiurn-bisrnuthsolution . During the satisfactory after a total of 400 liters of lithium period of interest (which constitutes most of the chloride had been circulated because, by this time, a experiment), only lanthanum was present in sufficiently hole had developed in the Li-Bi container. This hole high concentrations to react with an appreciable caused poor contact of part of the solution with the amount of lithium. Thus a material balance on lithium hthhun chloride during the remainder of the experi­ in the Li-Bi fiolution can be written as follows: ment. Thus the measured lithium concentrations would be expected to be lower than the predicted values, as is

X + (2) observed in Fig. 17.1. ~ ^Bi-Li Jt *Li(Bi) ~& Li(LiCI) *L.' 204

The agfcerrtmt between the predicted and observed bismuth zie fabricated of carbon steel. The main vessel behavior of lithium in experiment MTE-2 provides good is constructed of 6-in.-diam sched 40 pipe and is divided confirmation of the recently measured data on the into two compartments by a partition that extends to equilibrium concentration of lithium in lithium chloride within % in. of the bottom of the vessel. The two in contact with a Sthium-bismuth solution having a high compartments are interconnected by a pool of bismuth lithium concentration. containing eductant. One compartment contains fluo­

ride salt (67-J3 mole % LiF-BeF2 ) to which were added 147 17.2 OPERATION OF METAL TRANSFER 11 mCi of NdF3 and sufficient ThF4 to produce a EXPERIMENT MTE-2B concentration of 0.19 mole %. The other compartment contains lithium chloride. A separate, electrically insu­ E. L. YouogUood L. E. McNeese lated vessel containing a 5 at. % Li-Bi solution is As discussed in the previous section, a much larger connected to the lithium chloride compartment with a decrease than expected was observed in the lithium %-in.-diam sched 80 pipe. During operation, molten concentration -n the bismuth into which rare earths lithium chloride is circulated between the Li-Bi vessel were extracted from the lithium chloride in metal and the compartmented vessel by pressurizing the Li-Bi transfer experiment MTE-2. A new experiment, desig­ container with argon. Gas-lift sparge tubes are used to nated MTE-28. is cow under way to study further the improve the contact of the salt and metal phases. The transfer of lithium from a lithium-bismuth solution experiment is being operated at 645°C. containing li&um at the concentration proposed for The quantities of materials used in the experiment are extracting trrotent rare earths from lithium chloride shown in Table 17.1. These materials were purified for (ije., 5 at. %). removal of oxides prior to being used in the experi­

The experimental equipment is shown schematically ment. The two bismuth phases were sparged with H2 at in Fig. 17.2. Ail components that contact salt and 6S0°C for 12 hr and were charged to the carbon-steel

ORNL-0WG 7I-6199A ARGON INLET AND VENT

6-in. CARBON STEEL PIPE

fri-in. .LEVEL / ELECTRODES

4-*. CARBON LiF-etF -ThF STEEL P»E 2 4 (66.8-33-0.19 mo* V

BISMUTH WITH 0.2 Ot % Li 3-M. CARBON STEEL PIPE

* at. % Li M Bi

Ffc.17.2. MK* &* Vital hr •XBwtwMrt MTE^2B. 205

Table 17.1. Materials used in metal transfer experiment MTE-2B Data obtained thus far are summarized in Table 17.2. During the first two weeks of the experiment, decreases Volume Moles were observed in the concentrations of lithium in the (cm3) (g) Li-Bi solution and in the main bismuth pool. Simulta­ Fluoride salt 794 47 neous decreases were noted in the distribution coeffi­

(LiF-BeF2-ThF4, cients for thorium and neodymium, whereas an increase 66.8-33-0.19 mok% was noted in the emf measured between the two ,47 plusllmCiof Nd bismuth phases. We believe the decreases in the tithium as tracer) concentrations resulted from reaction of lithium with Bismuth (containing 1130 52 impurities in the system. Two weeks after the begmnmg about SO ppm of Li and20GppmofTh) of the experiment, 8.5 g of thorium was added to the Th-Bi solution in order to increase the concentration of LiCl 1338 47 reductant to the desired value. At this time, die Li-Bi (5 at. % Li) 187 9 measured emf between the two bismuth phases de­ creased to near the expected value of about 250 mV, and the distribution values for thorium and neodymium vessel, which had also been contacted with hydrogen at increased to about the expected values. During the 650°C for 12 hr. The lithium chloride was contacted subsequent operating period, the lithium concentration with bismuth that had been saturated with thorium at in the Li-Bi solution decreased slightly (from 4.40 to 650°C, and the fluoride salt was obtained in purified 4.0 mole %), as shown in Fig. 17.3. During this period, form from the Reactor Chemistry Division. the emf measured between the two bismuth phases The experiment is designed in a manner such that increased steadily from about 2S0 to about 276 mV. data on lithium transfer can be obtained by the Calculated values for the lithium concentration in the following independent methods: Th-Bi solution, based on the measured emf values and 1. Direct determination of lithium in the Li-Bi solution the concentration of lithium in the Li-Bi solution, are used for extraction of rare earths from the lithium observed to be in reasonable agreement with lithium chloride. concentrations determined by analysis. Data on the 2. Direct determination of the lithium and thorium variations of the thorium and neodymium distribution concentrations in LiCl in equilibrium with the Li-Bi ratios during the experiment are shown in Fig. 17.4. solution. Calculated results based on emf measurements and on lithium analyses of the Th-Bi solution are shown for 3. Determination of the rate at which lithium is comparison with experimentally determined values. transferred from the Li-Bi solution to the main Although the- scatter in the experimental data is bismuth pool, as indicated by changes in the appreciable, the values appear to lie closer to the results 147 distribution ratios for thorium and Nd. The that are based on emf measurements than to those composition of the fluoride salt and the relative based on lithium analyses. volumes of fluoride salt and bismuth were chosen Several conclusions can be drawn from these data. such that the maximum thorium concentration that The observed decrease in the lithium concentration in can be attained in the bismuth is only one-half the the Li-Bi solution represents an equilibrium lithium solubility of thorium in bismuth. This will prevent concentration in the LiCl of less than 0.3 wt ppm; the bismuth phase from becoming saturated with however, transfer of this amount of lithium from the thorium. If saturation occurs, the thorium and Li-Bi solution to the Th-Bi solution would have neodymium distribution ratios will not be sensitive increased the concentration of reductant in the Th-Bi to transfer of lithium into the main bismuth pool. solution by about 10% and would have also increased 4. Measurement of the voltage that is developed when the ueodymhim and thorium distribution ratios by the two bismuth phases containing lithium are about 33 and 46% respectively. In addition, a decrease connected by the lithium chloride. It was antici­ in measured emf of about 5% would have been pated that the developed voltage could be interpre­ observed. The data appear to be consistent with a slight ted in terms of a concentration cell involving loss of reductant from both the Li-Bi and the Th-Bi bismuth phases that contain lithium at different solutions by reaction with impurities in the system. It is concentrations. believed that further operation of the experiment will Table 17.2. Summary of data from metal transfer experiment MTE-2B Meuuxed distribution ratios Volume Li concentration in: Time Pumping ofLrCl Measured Thorium Neodymium Neodymium Inventories (%) Time emf Li-Bi Main Bi Comments (days) pumped solution pool between between between (hr) (mV) Biand Thorium Neodymium (liters) (mole %) (mole %) Biand Biand fluoride fluoride LiC)

0 0 0 254« 4.93* 0.196fl 0.15 41 100 7 0 0 332 4.88 0.00003 0.006 106 12 0 0 345 4.33 0.02 0.003 <0.00004 <0.0003 ISO 69 14 0 0 Added 8.5 g of thorium to Th-Bi 15 0 0 250 0.07 2.6 50 solution 1% 0 0 253 4.33 0.16V 0.10 0.16 2.5 86 20 20 7.3 11.6 255 4.60 0.157 0.10 0.15 1.4 87 11 22 21.0 36.6 255 4.05 0.18 1.7 10 25 27.7 46.9 253 4.60 0.30 0.08 0.16 1.2 96 6 27 41.8 69.9 253 4.60 0.151 0.11 0.18 1.8 84 8 32 62.4 103.7 260 4.05 0.15 7 0.06 0.15 3.5 91 10 34 81.6 131.9 259 4.60 0.139 0.07 0.15 1,7 76 10 39 160.2 244.6 267 4.33 0.151 0.06 0.12 1.5 78 5 41 173.4 265.0 262 4.60 0.160 0.05 0.06 0.6 75 5 46 1943 293.3 264 4.05 0.111 0.04 0.20 0.4 85 4 53 280.7 428.0 273 4.05 0.142 0.03 0.09 1.2 76 11 60 384.7 591.1 276 4.05 0.0994 0.06 0.4 13

"Calculated value.

n 207

ORNL-OVG ?«-954«RA 0RNL-QV6 71-9547RA K>

« f |«J|JL « —•—• Li IN Li-8 i o ^ 2 x i- z> 5 5 ' g 0.5 IT

o 0.2 Li IN Bi -Th FRO o ^ *— 1 zzrr 0 0.1 ^T o Li IN_ Bi-Th T BY 4 NALYSIS —j^

0.05 1 100 200 300 400 500 600 VOLUME OF LiCl CIRCULATED

Ffc. 173. VJ km of 0.01 MTE-2B. KX) 2O0 300 400 500 600 VOLUME OF LiCl CIRCULATED

Ffc. 17.4. Vntioa of Nd aad Th MTE-2B. show tower equilibrium lithium concentrations in the LiCl in contact with the 5 at. % U-Bi solution than the present limit of about 0.3 wt ppm of lithium.

173 DEVELOPMENT OF MECHANICALLY compartment, and lithium chloride wul be circulated AGITATED SALT-METAL CONTACTORS through the other compartment. An agitator having a. H. 0. Weeren L. E. McNeese paddle in each phase will be plactd in each of the compartments. The paddles wfll be located at a consid­ Mechanically agitated salt-metal contactors are being erable distance away from the interface, and die phases dveloped as an alternative to packed columns for wul be agitated as vigorously as possible without MSBR processing systems. This type of contactor is of actually causing dispersion of one phase in tM other. particular interest for use in the metal transfer process The hydrodynamic performance of una type of since designs can be envisioned in which the bismuth in contactor has been investigated using water and mer­ the contactor would be a near-isothermal, internally cury to simulate molten salt and bismuth in order to circulated captive phase. It is believed that contactors determine favorable operating conditions. Test of sev­ of this design may be easier to fabricate than packed eral sizes of contactors with different agitator arrange­ column contactors. The proposed contactor, shown ments estabtisiied that the common factor that limits schematically in Fig. 17.5, consists of a vessel that is the agitator speed is entrainment of water in the divided into two compartments by a central partition mercury circulating between the twr halves of the that does not extend to the bottom of the vessel. A seal contactor. Entrainment of watfr was fount to begin at between the two compartments is provided by a pool of a definite agitator speed; below the limiting speed, no bismuth that win contain reductant. In operation, fuel entrainment was observed. The limiting agitator speed carrier salt containing rare earths will flow through one was found tc be relatively independent of the size and 208

~OWG 74-9544A

AGITATORS

LiCI

PARTITION BETWEEN FLUORIDE SALT CELL HALVES

BISMUTH C0NTAINM6 REOUCTANT

4-BLAOED PAOOLE

GAP FOR BISMUTH FLOW

Hf.17.5.

shape of the contactor w\ael but «» strongly depend­ mercury-water interface. It is believed that the entrain- ent on agitator diameter, as shown in Fij. 17.6. roent at water in the mercury phase results from flow Consideration of these data, along with data from the of water down the agitator shaft to a point below the literature,2 on mass transfer coefficients in this type of water-mercury interface, where it is then dispersed into contactor suggest that optimum mast transfer perform­ the mercury phase. The limiting agitator speed with ance will be obtained by use of the largest possible canted blades was decreased significantly when the agitator diameter. This will also result in the lowest contactor contained baffles or other items such as possible agitator speed, which should facilitate main- thermoweOs or sampling tubes. In all cases, however, a taining a go-tight seal on the agitator shaft. higher limiting agitator speed was obtained with canted It was found that the distance between the lower edge blades than with vertical ones. of the partition and the bottom of the contactor newel A test was also carried out to observe the effect on could be increased from % to % in. without appreci­ contactor performance of the difference in densities of ably affecting the limiting agitator speed. However, the the two phases. The test was made in a heated limiting agitator speed was reduced as the separation contactor with Cerrotow-lOS (42.9-21.7-183-8 0-5.0- dfetance was increased above % in. Considerably higher 4.0 wt % Bi-Pb-In-Sc*Cd-Hg) and watt The metal Hmiting agitator speeds could be obtained when the phase has a density of 8.1 a/cm* and a hquidus agitator blades were canted at a 45° angle instead of temperature of about 38°C. At the operating tempera­ being vertical and the direction of rotation was such ture of 60°C, the limiting agitator speed was nearly that the agitator lifted the mercury phase toward the identical to that obtained with mercury and water in the same contactor. Thus, it appears that the perform­ ance of the contactor will not depend significantly upon the difference in the densities of molten salt and 2. 1. •. Uwk, Om. E*£ ScL 3,148-59 (1954). bismuth. 209

ORML-OBC 1-9MH The three carbon sted vessels required for the experiment are shown in Fig. 17.7. The fluoride salt met von is on the left, die compartmented salt-metal contactor is m the center, and the rare-earth stripper vessel is on the right. The fluoride salt pump, which has been fabricated, wffl be inserted m the large flange on the fluoride snh reservoir. Both the pump discharge Mne to die salt-metal contactor and the retae stream from the contactor pass through the upper horizontal 3-in.- dnun pipe between the two vessels. The lower pipe is a structural mnnber. The agitators for promoting contact 20 SO 100 200 500 WOO of tue salt and bismuth wnl be mounted on the two LOOTING AGITATOR SPEED («•*) nangec nozzies on the salt-metal contactor vessel (only one nozzle can be seen s this vier,) and on the vertical flanged nozzL en the rare-earth ttrir per. The hthuun chloride wffl be pumped back and forth between the salt-metal conr-jctor and the tare-earth stripper vessel by varying the gas pressure in the stripper vessd. Figure 17 A shows a delated view of the top of the rare-earth The rate at which mercury circulated between the stripper vestd with the agitator shaft seal housing and two halves of a !0in.-diain contactor havinfc a 3-ia.- shaft cooler JmtaaVd m the agitator nozzle. The vessd is dbm agitator was determined by iwr awing the rate of return of the Equids to a common temperatnre on resumptkM of mercury flow after one side of the eel had been doled and the other side of the cefl had been heated. The mercury flow rate was found to be about IS Mters/min acd deputed, to some extent, on propeller configuration. A bismuth circulation rate of 0.5 Mter/min or greater is desired in the contactor for metal transfer experiment MTE-3, which uses a 10-in.- duun contactor. Thus, it appears mat circulation of the bismuth phase wiil be more than adequate.

17.4 DESIGN OF THE THIRD METAL TRANSFER EXPERIMENT E. L. Nicholson W. F. SchafTer, Jr. LEMcNeese E. L. Youngblood H.O.Weeren

The design of tht third engineering experiment MTE-3 for devdopnent of the metal transfer process for removing rare earths from MSBR fuel carrier salt has been completed. Most of the equipment has been fabricated, and the main process vessels are now being installed. This experiment vffl use salt flow rates that are 1% of the estimated MOW rates required for processing a IOOO-MW(e) reactor. The planned experi­ ment and equipment have been described previously.3

3. E. L. NidttUM «t aL, MSR /topun Stmkimu. Aqr Up. Ftk 28.19" ~-UIL-4*7t, pp. 245-55. Fh> 17.7. W|il|iiT tar n**3 uauste maid in ill MI**, 210

:iJS*^*5JT^&'- MOTO «30-7l

1%. 17A Top

electricaily insulated from the other equipment to nickel aluminide coating that was applied to the minimize the rate of transfer of lithium between the carbon-steel parts of the vessel. two bismuth pools (which have different lithium We are still testing the agitator drive unit and the concentrations) in the experiment. The UC1 transfer nonlubricated shaft seal assembly, which is water- line is constructed of %-in. sched 80 pipe and is cooled and buffered with inert gas. The assembly insulated from the rare-earth stripper vessel by the contains two standard graphite-impregnated Teflon water-cooled, Teflon-gasketed flange assembly shown Bal-Seab (product of BaJ-Seal Engineering Co.). Figure on the right side of the figure. The portion of the 17.9 shows the test equipment prior to completion of carbon-steel pipe located adjacent to the cooled flanges the piping and installation of the electrical heater* and is heated by a nickel jacketed copper sleeve on which a thermal iuscdstion. Two seals were tested initially for Calrod heatc. will be mounted. The method uW for 820 hr at shaft speeds of 1 SO to 750 rpm while salt and mounting the heater will facilitate replacement of the bismuth were agitated at 650°C in the 3-in.-diam test heater in the event that this becomes necessary. The vessel. The seals were buffered with argon at 16 psig. heater will be wound in the grooves in the enla.ged After an initial run-in period, the seal leak rate was threaded part of the nickel-dad copper sleeve. This about 8.6 cm3 of gas per hour. After 700 hr of figure rJso shows the flame-sprayed, oxidation-resistant operation, the leak rate increased rapidly up to the time 211

n* 17.9.

'.i2r) and the *"Zr con­ the scatter in *7Zr counting results was centration in the bismuth leaving the column. Since the low. The fraction of tracer transferred fromti e sak was quaity of the data improved from run to run, the 030 and the calculated HTU was 2 ft, based on %DjM calculated HTU values are not directly comparable. of 1.9. The postrun aiiunium distribution coefficient, Samples of bismuth exiting from the after a 2-hr tqugbntion of the salt and the second '7Zr tracer experiment, ZTR-2, i in the treatment vessel, was 077. that about 30% of the tracer had transferred to the salt; to remove saspected oxidaats from Ihe however, analyses of salt samples indicated that only system, the bismuth and the salt were tounsmuruaily 15% of the tracer had transferred- The postrjn zirco­ contacted in the cotuon about 20 hr prior to experi­ nium distribution ratio (determined from the *7Zr ment ZTR-S. Tracer was then added to the activity) was found to be 0.034. This is in excenent •ad run ZTR-5 was carried out with agreement with the value of 0.038 ± 0.020, which was a nonanal How rate of 150 ml/nun calculated from postrun uranium dhtributjon data. results for five of seven bissnuth sasnples (Fig. 17.11) Since the observed '7Zr transfer could not have were wftlun ±7% of their average, fsowever, oat occurred with such a low zirconium distribution coef­ counting rates for the two remaaangsaarpk s were 2 ficient, it is apparent that some loss of reductant must and 170 times the average of the other snajnles. have occurred between the packed column and die Fonowing a 3*r equilibration period in the treatmeat bismuth and salt receivers. vessel, both phases were returned to the seed ranks, and

In order to increase DZk before the next experiment, ran ZTR-6 was carried out Counting results for salt U-Bi alky containing 038 g-equhr of Mthium was added samptfs were comparable wim recurs obtained onmag to the treatment vessel; the addition of *7Zr tracer run ZTR-5. However, the tracer concentrations m bismuth samples were generally a factor of 2 to 3 times indicated a DZr of 0.25. An additional 0.7S g-equrv of

t7 Taste 17J. & Salt (72-16-12 ante % UF-ntfrTW^) and at 600* C at m OJmmAD by 244n.-touf sacaad

Salt Flow avjuatli Fncttoa DOV/IStt, rate 7 HIU of* Zr - ratio. (ft) (uWuua) (aaVana) *>2> ZTR-2 232 70 3.3 0J2 ais* ~4 ZTlt-3 93 It* 055 1.90 0.30 2 ZTk-5 147 15S 0.93 0J4 0.14 1 214

stream samplers. SoJt a contaminant could have re­ sulted in U* accumulation of *7Zr,as •'ZrOj.at the bismuth surface in the sampler; subsequently, some of mis material might have been drawn into the sample capsule since the samples were taken from near the bismuth surface. We are presently replacing several bismuth and salt transfer hues in which leaks have occurred. We are preparing for additional *7Zr tracer mass transfer expe^menss that wal use an improved technique for obtaining bismuth and salt samples.

17.6 DFVELOnftKTOFAHWZEN^ALL FLUORINATOR: INDUCTION HEATING

J. R. laghtower, Jr.

An experiment to demonstrate protection against corrosicn in a continuous fluorinator by use of a frozen nan wal wffl use high-frequency mducrion heating to serve mt-J. Salt flow ate, 168 te,*3ajft/i i>Zr»I3. as a heat source m the molten salt. Heat generation rates were measured with four induction coil designs in

a system that used 31 wt % HN03 as a substitute for molten salt With these measured heat generation rates, correction factors could be computed for use in equations for calculating the amount of heat that is induced in sinmar, but idealized, geometries. The equations were then used to design equipment for a molten-salt induction heating experiment for testing (I) the operation of the proposed heating system and (2) the means by which power leads are introduced into the fluoiisator. The results of measurements with the nitric acid system and the design of equipment for the molten-salt induction heating test a*? summarized in the remainder at mis section. Results of experiments with a ammfeted flsxmnator. The equipment for measuring heat generation rates in a system that uses 31 wt % HNO-, as a substitute for •»« molten salt has been described previously.4 Twenty- ElaVS and ZIftV*. ,7ZrOj tracer was added to the salt feed nine rum were made to determine heat generation rates took pwnwdhn ZTR-5; tracer was s^wawraled in TS pvecedis* in the acid, in the pipe surrounding the scfcl, and in Zllt-6. Feed to* dmjpiUnai- Tl (Mravstfc), T3 (salt), each of four induction coils. The length cf each ask dfripi.vros: T2 (MmBtb), T4 (tail).Timbaeat induction coil assembly was 5 ft, and each coil assembly TS. was made of a number of smaller coil sections con­ nected electrically in parallel. Each small section had an inside diameter of 5.6 in. The characteristics for each of the coil assemblies are given in Table 17.4. heftier man in the previous experiment. Suspected oontamirjatk» of the bismuth sample* with salt was ruled out by visual inspection of several of the samples. A review of the sampling procedure indicited mat small 4. J. R. Hifhtower, Jr., HSRP SemUnnu. Jvojr. Rep. Feb. amounts of air might possibly be entering the flowing 29.1971, ORNL4676, pp. 262-64. 215

17.4. of co* i

Length No. Diameter Na Winding of of of of of Col Material snail conductor adjacent sections (in.) sections sections (in.)

I Moae! 17 % 3 6* Opposing

U Stainless steel 18 % 3 6 Assisting

m Stainless steel 18 % 3 6 Opposng

IV Copper 10 % 4 H% Oppos-g

The measured heat generation rates were used to where calculate correction factors for idealized design equa­ tions that had been derived previously. The design Pp = heat generated in pipe, W, equations (which define the correction factors) are /tot, if. A,, and L are as defined for Eq. (1), given below. The equation for heat generation within g = specific conductivity of pipe material, SI"1 nf *, the fluid zone inside die coil is: p

op = inside radius of pipe, m,

1 2 Pp=(2*fgpVpr ' , P, = k 03818 (i) k = correction factor, dimensionless, fe)m p Up = magnetic permeability of pipe material, NA"J. where

This equation is valid for (ap/pp) > 10. The equation Pi = heat generation rate, W, for the heat generated in the induction cofl is: n = average turns per meter over length of coil assembly, / 2 L, (3) Ns - nunioer of small cofl sections, 'tot a = radius of fluid zone, m, where L - length of coil assembly, m, 7 , L, and N are as defined in Eqs. (1) and (2), P/^ir/gYMf)-1'2, tot s

-l Pc * heat generation rate in coil, W, gt ~ specific conductivity of fluid, ft nf *, Hi - magnetic permeability of fluid, N K1, b - inside diameter of cofl, in., d ~ conductor diameter, in., /-fre

tota nTO l - length of a small section of coil, in., hot~ ' °°^ current, A, c N = number of turns in a small ceil section, k - correction factor, dimensionless. T o - specific resistivity of coil material, ft 12* cm, Equation (1) is an approximate equation and is valid for c (a/pi) 5 1.4. llie equation for the heat generation in ft « frequency, kHz, the pipe surrounding the coil is: Kx - proportionality constant having dimensions de­ fined by Eq. (3). The effect of bubbles in the nitric acid on heat e,-*p generation rate was investigated with coib HE and TV. W®*1- - Seven runs with coil III and two runs with coil TV were 216 tank *£& *i flow rates up to 2.16 scfm, which decrease in the axial component of the field. It is the peodttosd bufe?^ volttme fractiom in the acid as high as axial component that provides the proper ecdy currents f#A>. in tlie f-srjQ of bubble volume fractiom examined, for heat generation. tke «*fue tflttfmed by Eq. (I), varied approximately Although any one of the four coils couki be used to >*.jf*v wifW&tdble volume fraction. The effect can be generate heat in the proposed fluorinator. coil IV wouM +spK**rl by (IK following relation: require the lowest coil current to perform the require*! heating and, for this reason, would be the most

k*ko0 !.079e). (4) desirable. Calculations have shown that, for a 5-in.-dtam

molten-salt zone, a 5.56-in.4D coil made from V4-in. where nickel tubing (using a coil IV design in which each small section has 9V, turns over a 3%-in. length, with a k0 * the value of it with no bubbles present, 2V44n. space between small sections), and a 6% «-in.-lD € * bubble volume fraction. nickel fluorinator vessel, an efficiency of heating the salt (with no bubbles) of about 49% would be achieved Values for k0, kp (see Eq. (2)|, and Kt (see Eq. (3)) for the four work coils tested are given in Table 17.5. with a total current of less than 140 A. With coil III, the efficiency of heating the salt would be shout 58%, but a coil current of 267 A would be required. Morten-salt BadaKfJon beating test The experimental TaMt I7.S. Comctios factoo Cor heat results obtained with the simulated fluorinatot indicate that sufficient heat can be produced is the molten salt by induction heating. However, before a fluorinator Coi *0(aob«bbktt) tp £,« experiment is designed, a number of factors require X 10"5 further study. These include: (1) verifying the predicted I 0.130 0.624 1.915 coil performance, (2) demonstratug a means for intro­ II 0.089 0.447 1.7SS ducing the if power leads into the fluorinator vessel, II! 0.178 0.623 1.885 and (3) checking the general operabihty of a system that contains molten salt. Equipment has been designed IV 0.216 0.586 2.15 and installed for inductively heating molten salt in a vessel similar in design to that expected for the •n* caaeaskMtof K, are defined by Eq. (3). fluorinator experiment. The test vessel, essentially a short version of the proposed frozen-***!! fluorinator, is a S-ft-krag by The values for aD constants for coil II are smaller than 6*i«-in.-ID nickel column having two conduits for the the corresponding constants for the other coils. This v induction coil electrical leads that extend along the apparently the result of winding all of the small cofl vessel wall from the top to within I ft of the bottom of sections in the same direction, since other character the vessel. The conduits are made from 1-in. sched 40 istks are similar to those of coils I, HI, and IV. Coil II nickel pipe. The gas inlet nozzle near the bottom of the requires the largest current to produce the required beat column is made from 2%-in. sched 40 nickel pipe and generation rate in the molten salt but might have a high enter* at a 45° angle to the axis of the test vessel. The efficiency for heating the salt if the molten diameter is test section in which the frozen-salt layer will be sufficiently large. formed is 3 ft long and begins I ft from the bottom of

The value for k0 was largest for coil IV. This is the vessel. Figure 17.12 shows the installed vessel with probably due to the difference in spacing between the Cahod heaters and thermocouples in place. The induc­ small coil sections. Coil IV had 4-in.4ong small coil tion coil to be used for tins test is of a design similar to sections with 11% turns per section, and the coil coil IV. The coil, shown in Fig. 17.13, consists of six section* were separated by a space of 2 in. The smaller small coil sections connected electrically in parallel to sections in the other coils were placed dote together so leads that are made of %-in. nickel tubmg. Each small f hat the coil turns were spaced evenly over the length of section is 3% in. long and 5% in. ID and consists of the acid column; the total number of turns was iixxit 9% turns of %-in. nickel tubing. Adjacent coi sections the same for each coil. In the case of coils I awl II, this are wound in opposite directions and are separated by a closer spacing compressed the magnetic field between distance of 2% in. The leads to the smaQ coal sections each of the smalt coH sections, thereby effecting a fit into the conduits on the vessel wafi cad sSow the coil tc be located very dose to the wall. Quartz insulators on the %-in. leads and on tfc* inside walls of the vessel prevent the coil from making electrical contact with the vessel when frozen salt b not present.

17.7 PREDICTED PERFORMANCE OF CONTINUOUS FLUORINATORS J. S. Watson UEMcNeese Thus far, most of the flowsheet* considered for use in processing molten-salt reactor fuel salt require fluarina- tioa of molten salt for removal of uranium at one or more points m the flowsheet These include: (1) re­ moval of trace quantities of uranium from relatively small salt streams prior to discard. (2) removal of uranium from a captive salt volume in which 2,3Pa is accumulated and held for decay to "*U, (3) le-uoval of most of the uranium from relatively large fuel salt streams prior to isolation of protactinium and removal of rare earths, and (4) nearly quantitative removal of unaram from a salt stream rnnlaawng "*Pa a order to produce isotopicaly pure 2,*U. Not al of these operations would require cononuoas fluorinaton. hi fact, the use of batch fluotmaton has definite anV*n- taaes in certain cases. However, m the onantities of suit and uranium to be hsnrlcd increase, the use of continuous fluorinaton becomes mandatory in order to avoid undesirably large inventory charges on uranium and molten salt, as wefl as the detrimental increaae hi reactor doubhng time that is associated with an increstisd fissile inventory. /Jthough the Iterative contains many references to the removal of uianiuni from molten salt by batch fluorination, information on continuous fluorinators, particularly on fluorinators capable of ttaadung salt flow rates on the order of 100 ft'/day. is rather meager. A mathematical analysis for predicting continuous lions were niade for fraorinator operating condrtfama interest for MSBR proceating. ftiirinatiJi. Consider a differential hdght of a con- Unuous fluorinator in which fluorine and rartltan ask containing eranhun are In countercwrent flow, if the rate of ranarnl of waussm from tte aaft b aavanmd to ae nrst oruar wwn respect to tns utaanem coawmmuon in the aaH, a material balancr on the flfleiential an* %Hmm yiaids the relation: 218

PHOTO M69-74

IV 17.13.

The boundary conditions chosen for use with 5q. (1) 3 D * *ud dispersion coefficient, cm /sec, assume that the diffusive flux across the fluorinator C* conceb^stion of uianjum in salt, rooks/cm3, boundaries is negligible: at X ~ 0 (top of fluorinator), X*position in column measured from top of col­ umn, cm, dX\ ^'D{Ct-d'C^h (2) V* superficial salt velocity, cm/sec, x * * reaction rate constant, sec- i and at X */ (bottom of fluorinator), The terms in Eq. (1) represent the transfer of uranium in the salt by axial diffusion, the transfer of uranium in (3) the sah by convection, and the removal of uranium lx\»jr« -°f ' from the silt by reaction with fluorine respectively. The •wimptinn of a first-order reaction does not imply a where particular rate-liaarJnt reaction mechanism; however, it CU%A » concentration of uranium in salt fed to the is consistent with the assumption that the rate-faming fluorinator, step is diffusion of uranium in the salt to the gat-liquid interface. In this case, the first-order expression would CQ+ * concentration of uranium in salt at the top of the fluorinator. hnpiy that the concentration in the sah at the interface k negMgibk m comparison with the uramum concen­ Note that C^ is not equal to CfMd since there u. a tration in the salt at points a short distance from the discontinuity in uranium concentration in the salt at interface. the top of the column where the salt enters. 219

The solution of Eq. (1) with the stated boundary -•••75 _-#*4VS JVPe * 18.0tfR.' " *Ar -••os N< conditions yields the following expression for the ratio s. of the uranium concentration in salt leaving the column and at high gas flow rates (slug flow), (at X~ I) to the concentration in the feed sah:

N,S a n=

VL 'Ar' 1 =

Application of Eq. (4) to the design and evaluation of Vg continuous fluorinators requires information on the rate constant it and the axial dispersion coefficient A fij« density of the liquid, Values of the dispersion coefficient were obtained from correlations resulting from studies in which air and ti§ * viscosity of the liquid, aqueous solutions were contacted countercaneaUy hi « * surface tension of the fraud, open bubble columns, as indicated below. A value for g m acceleration of gravity, the rate constant was calculated using data obtained previously during a study of the performance of a n «immhff of gas inlets in l-m.-diam continuous fluorinator. to Dispersm coefficient values. Studies m which air and of axial dnpt-iiton hi aqueous solutions were contacted countercurrentry in fluorinators for the range ot open bubble columns having diameters of 1,1.5,2, 3, and 6 in. were carried out previously. The viscosity of the aqueous solutions was varied between 1 and 15 cP reaction ate constant «*s evaluated from by the use of water-gjycerol mixtures. The viscosity of Eq. (4) using piukwdy obtained data on the perform­ molten salt under conditions of interest u sbout 15 cP. ance of a 1-oL-diam opea-column continaona Unorir The effect of the surface tension of the aqueous phase nator* and the axial ^jspertion cfwffkient data dh> was determined by varying the surface tension from6 8 cussed above. The fiuudaator performance data were to 27 dynes/cm, using v/aterHSopropano! mixtures. The obtained in studies with two difleient uranhnn concen' surface tension of molten salt is much higher than these tratiom m the salt feed (035 and 0.13 mote 9t) at values; however, the data allow estimates of the effect 6XXfCandoneuiaimnnconceiitnuion(0J5mole99st of surface tension on the dispersion coefficient. Data 52? C. Three data points coneapondang to duTeiant from studies were correlated5 by use of dhnen- sah flow rates were obtained for each set of umpera- skHdess groups in the following manner: for low gas tures and hurt ccvyosirJons. The fluorine flow rate was how rates (bubbly flow), different for each data point; however, according to Eq.

5. A. t~ T»m, G.E. Umbo,mi*.H.Ud**,AxMMixing 6. L. E. in Open Bubble Cohume, MIT ReportCEPS-X-121 (to] Ma 6, OtML-TM-3141 0n tioo). 220

(1), which defines the present modd, the fluorine flow 174 ErvGtNEERING STUDIES fate ooJy affects the restate by changing the xxial OFUIUNnMOXlOEnUCartTATION e%*ersion coefficient. The data obtained at 525*C were M. J. Bell D.D.Sood «sed to evaluate the rate constant kt since the operating temperature of the proposed frozen-waft tWorinators L. c. McNeese wnl be 10 to !5*C above the sah tknudus temperature The fabrication and mstanation of equipment7 for a of S05*C. Application of Eq. (4) to the three data angi?-stage experiment to study the predpitation of points obtained at 525*C produced the results shown in UO^ ThOj solid solutions from molten fluoride salts TaMe 17.6. The scatter in the calculated values for k n have been completed. In the two experiments carried acceptably anal, and no trend with salt or fluorine out thus far, the major equipment items operated flow rates is observed. Although these data do not satisfactorily. Several minor difficulties rhat were en­ confirm the validity of the model, they do not countered, including the freezing of sah and the fe­ condensation of water m several lines in the system, have been aleviated- A thud expcrisiss! s si progress. et In the fast experiment (OP-1), a gas stream con- rhtorinatars was estimated from Eq. (4) taniing 15% wacer-85% argon was fed to the precinita- 1 the previously discussed estimates of the reaction tor vessel ai the rate of 0.5 sdh for a period of 4 hr rate constant * and the axial dispersion coefficient tk whh the s»rt at 600°C. The gas flow was interrupted T«* required ftnorinatorheigh t is shown in Figs. 17.14 periodical) during the run. and flhered salt 1 ampler and 17.15 for a range of mtt flow rates for two were obtained. The precipitate and the sah were

* (0.95 and 0,99). The alovKdtoeqiaibraufc<64hrtafwvdakhasanyteof concentration in the inlet salt was aananed to the oxide phase was obtained for analysis by x-ray be 0.0033 mole taction in al cases, and the fluorine duTraction. The sah was then slowly transferred from to be equal to 1-5 thnes the the precipitator vassal to the tieatment vessel in order to ktve most of the precipitate in the precipitator. ing since they suggest thttsmnle fmoriantion vessels of SulMMueutiv the sah was hvdrolluorinated in the moderate size wifl snffioe tor removing urnahtm from n^w^r*rw^nw^*wv*e>j g, ww« eawi ^v/unw m v wa wvfwwi awn ^MI awa www vessel and aamphd again ia order to deter- mma^wevm% nnwwm nmmv> nwui wa^ mv# un^nwnnsvapm) ^^v wa w^sj^nxjpujmnjmmnmi flat amount of precipitated uranium that bad by reductive extraction. The reference flowsheet for transferred to the treatment veatet Finely, the sah was testing protactininm by fluormatioo~ieductjve ex- returned to the precipitator vessel, where it was IrydroOttormated for 12 hr using a 20% HF-80% H, 170 ft*/day, which h eqnivaleot to a ten-day plowing gat mixture at the rate of 3 scth in order to ridiieorw cyde. A 64L-dfcn fluormator having a height of 10.2 ft v/fl be required for a uranhan removal efficiency of 95%, and an S-m.-dmn traormator having a height of

17.S ft wul be required for a uranium removal *• M* J» uV4M MM L* C* eWJCVMwnTn% *"W3B™4 a*v^ efficiency of 99%. AOF. Rtp-FtkTi, J971. 0ftNL4e7t, p. 247.

174.

Satti CO) 4 1 (sse" ) 0.0625 0.0257 6t 174 aootos 0.0445 041096 5.0 0.01033 0.0223 0J00457 342 104 Avenue: 0.0090S 221

present in the salt was precipitated «o ancmct. <&% daring the run. However, the analyses show consider­ able scatter, sad the nrsnhim concentration in the salt so r rmo—g rc£D Mtrc oo% or does not decrease asonotonicsMy with tine. The analy­ r ses indicate a water ntifczatioa of about 15%, afthonpji is sow* uncertainty in thai vaJnc Decease of with the condensation of water it- Analysis ot~«*e onJde colected at the end of the peecajMUtioa period revealed that a UOs-TM), sowd eolation having a UO, concentration of 054 ante traction was forssed, and that 5 to 15% of the precfcnmate was 110,. The itrafjon of BeO in the aatxasitaie was jdow the of deteciion (< i wi %). The presence of ThO» the tact that the artniaw cowteat of the anwi shandy lower than the vasse expected at (056 arte fraction UO,) iadkilr that the salt and the pseceaaafe was in an da- ifbaad tone flat u thai ttbtVaid fw Iht flunnl Jl nwaph tsJian the wedptate had been atoned to settle for 64 in- hr. This lateen that it aony be poaa>k to separate the 900 :~L_J. i ~T- r I J i from the seat with relatively M.EFFK asset: ai IVLC1 aaaae < RAHOJta Iathest»MkJejVerawac:t(0rv2), FLOO EFffD IMC: «0%0FS T eMSmac was again held at 600"C m* the ofthn £ 400 =*= = = W—"IV< - -"H"- =F : 11 iT>- safe ps aaxtast was IS%1 * 90 11 J IILXJ ^^*>«h In this exearaetat, the salt was first crjetacted wMi tat 11 jjf^X pa arixta* at a rale of 05 scfli for 9 hr; than the gas ¥ • 1 iL _ •n j flow rate was inceeased to 1.5 sdb for an addWoaal 5 20 FLUOftNArOft ll*£gJPJ 5-hr period. The total peecipitafJoa tana (14 hr) DUUBiTfJt „ extended over a neriodofaaoat eeadav*.aaawMwafcb i ** ^•^••^••^•WI^PJ w»^^ n» wisaww ^P» wpnvw^aww WMV anwweny w#wawaaaaa ^waaaajaas §i the ran was iaterrapved several tanas in order to aaodhy -I r v jt i fd r'--- i gas aaes and add heaters aad thenaal aaanatioa tc a t2ta_ Y • aaaaber of Maes where roadrasstion of water was 2 nw^^wpaas*e^pna» ataaa> waoaaananannBe ^Mpava^pwawooMnap^n ^^aaawaB v^aasi ana laieiea salt sasanes oataaaea oaring tae •!• ana tae I expected aranaaa concentration based oa the asBoant 9 fO* 2 9 10* 2 of HF evolved dariag the ma are shown hi Fsj. 17.16. 9 SALT FLOW RATE (ft /**) The discoataasiry hi the carve based oa HF cvosstsoa at 6.7 hr rented from the Cast that loaaaasslf was Ffc 17JS. obeerved hi aeon-gas Mae between periods of precjajta- rJon. The rnadaassti wa

the pvacipitatioQ phase of the experaaaat was coa* the uranium and thortan oxides. Salt samples were tinned. Tat areater nst of HF evoawJoa observed after withdrawn at intervals during this hydrofloprination •••W^^^^B** e> aaw aawwvwv aeaawF ww *aw w/v^pwenwwnpwe WFWPepww WW asw www period. Analysis of samples taken during the precipitation Salt seasons taken early hi the (shortly phase of the experiment indicated that 17% of the tfUr the ^rtripitatiffn had been djaconraaaid, i

f~" tU

ONNL-MC 71-M4M pleted. Preliminary drawings for the molybdenum piping arrangement inside the containment vessel have also been completed; however, further work on these drawings will be deferred until the piping can be analyzed for thermal expansion stresses and a full-size mockup of at system can be completed to investigate fabrication and field assembly problems. The overall height of the molybdenum components of the loop (from the underside of the containment vessel flange to the lowest point) is about 17 ft. Both the sah and the bismuth gas-lift pumps are rtftignrd to operate with a minimum submergence of 50%, which should provide the msxhsum flow rate desired for either phase (i.i hters/mm). Final tests were completed with the revised design of 024 6 8W12W the full-scale transparent plastic mockup of die bismuth PREOPITATON TUC (art head pot and the top portion of the extraction column. Mercury and water were used to simulate molten bismuth and salt. Problems with internal flow restric­ daring tMani wanfe* eeani pradptottM m (OT-2). Salt tions and gas venting noted previously were solved by wapwaiwiwweotfC the revised design. Fntrainmcnt of liquid in the exit gas was reduced to very low levels by routing the gss through a settling chamber and Raschig-ring packing in the top of the head pot. after an extended eouffibration period) were found to The design of die probe for determining die position have essentially the same uranium concentration (It., of die sah-btenuth interface in die disengagement within the range of analytical error). However, analyses section below the extraction column was completed, of s*npks taken later in the experiment showed brie and a prototype probe has been bult for testing. Work variations between samples taken shortly after precipi­ associated with the development of liquid-level probes tation had been discontinued and those taken after a Is discussed in the followingsection . long eaufibratfon time. This behavior is not currently understood. Several samples of the oxide phase ob- 17.10 DEVELOPMENT OF A BBMUTH^ALT tained during the run may be helpful in interpreting the INTERFACE DETECTOR results. H.O.Weeren EL. Nicholson 175 DESIGN OF A IttOCESSra MATERIALS C.V.Dodd CC.Lu TEST STAND AND THE MOLYBDENUM J. Roth REDUCTIVE EXTRACTION EQUIPMENT An eddy current type of detector1• is being devel­ ELNichobon W. F. SchafTer, h. oped to aflow detection and control of die bismuth-salt J. Roth interface in salt-metal extraction columns or mechani­ cally agitated salt-metal contactors. The probe consists A report describing the conceptual design and fabrica­ of a ceramic form on which h!f. M. W. Roaratlui et aL, HSR FfOftm MMMMML ttof. are reported in Sects. 14.1-14.4. **p.F*h.28,J970,O*NL4S4*,ft.m-UH. The detailed designs of the extraction column and the 9. M. W. Koaanthal ft aL, MOH ftofim SIMMMML ttogf. salt and bismuth head pots have been completed, and Rtp. Aug. 31.1470, ORNL-4622, pp. 212-13. 10. M. W. ftomuMl «t aL, »GK fn>0tm Semkmm. Avar. fabrication has begun. Conceptual design sketches for Rep. Feb. 28.1971, ORNL-4676, pp. 267-61. the equipment supports in the containment vessel, 11. H W. RoemttjaJ tt aL, HSR hoyem Strntumm Prow mr***-1 tees, and the freeze valve have been com­ Rep. F«». 28.1970, ORNL-4S4S, pp. 300-301. 223 secondary coils are wound. Contact of the cois with these calculations revealed the manter in which the molten salt or bismuth s prevented by enclosing the nunjnituae of the signal in the secondary col and the coib in a molybdenum tube. In operation, a high- difference in phase between die steals in the primary frequency alternating current is passed through the and secondary cois varied as tut* stae, tube wal primary cofl and it induces a current in the secondary thickness, and frequency of the signal anpressedon the coil. The induced current is dependent on the conduc­ primary coi were changed. The results indicated that an tivities of the materials located adjacent to the primary adequate phase shift (a change of approxiamteiy 11* and secondary cols; since the conductivities of sakaiMl from the condition in which no bismuth %m present to bismuth are quite different, the induced current reflects the condition in which the tube was mtmirnti in die presence or absence of bismuth. The principal bismuth) should be obtained with a morybefenum tube psobiem associated with this type of detector stems having an outside diameter of 0.785 in. and a wal from the low permeability of molybdenum, the fabrica­ tion materci of the protective sheath. Two approaches carried out with a tare coswk;tor model, which for obtaining an output from the detector are being allowed consideration of the effect of the toniufrrr in pursued. The first is based on measuring changes in the which the bawjnfh and the probe are located. It was magnitude of the induced current; the second is based determined that the phase shift technique would have on measuring the phase shift that occurs between the about the same sensitivity at any frequencyi n the range voltage impoaed on the primary col and that which is of 20 to 34 kHz. The maximum change in nmmatudeof induced in the secondary col the voltage induced m the secretary col was about Initial tests in which measurements were made of 30%mthembnurmncimbwmumiaKw variations in the induced current caused by changes in 100%; the ripHnmm operating frequency was ft to 12 the bismuth interface position showed that the probe ktfe. was quite sensitive to drift in the electronic circuit, to After we had rtriirmmii the ma^inm aaiii whirh minor variations in line voltage, and to changes in the nufldamm seasftMtv could he achieved for the two tenmeratttre of the electronic components. To drcunv awuwjntmnmswvue nmnnwmwsrvemw wmjswjnma m>n> esmjnamwwvmf srmm wmun> u>uw vent this problem, an improved electronic circuit, which amde to find the irondhlnnt that would smahujsn the n relatively insensitive to amplifier drift and to changes change in probe output lusniting from a variation in in the temperature of the electronic coumontnts, was probe trnmentuw from 600 to 700*0. The fofrratng devised. DtfBculties caused by Hne T oh age variations affects were cosuaawjoau were avoided by use of a consttat*ofcan? power supply. A rulscale respond of about 1.5 mV was 1. The cnculateJ tharmai ixpsnstoa of the nmtyb- obtained at die optimum frequency for the primary con dsnum tube is appeoxima^ 0.05%; the phew shift (35 kHz) for a 9-ta. change in the bismuth interface due to this effect v* ca ,nmUd to be less than position at 600*C. 0.01 , which is conssdered asghgMe. During this reporting period, calculations were made for predicting the performance of interface detectors. 2. The resistivity of the bismuth mcieawi from 145.7 These calculations were based oa either measurements Ocn to 151J Oca, and the uahlliity of the of the magnitude of the todocedcurren t or the shift in mp*yt Jrnum meseaaea from 17.7 Q

phase between the primary end the secondary voltages. ™wm* •Jav^v«pV> waWmnawflaw/ WsW^aamnj^saBj nj 9^^LrJmTfl|nwsVs> B^mnWnw Optimum operating conditions were defined, and a shift over most of the frequency range, it was found prototype probe for use in the morybdenum reductive that a minimum change of about 0.1* occurred at extraction CO!*HUI was fabricated. Tests for confemiag 252 Mb when no bmnuth was present and at 302 the predicted perfotmince of die probe were carried klfe whan the probe was tunsjlsiily lufcmii^sd in out at room temperature. Equipment for final testing of bsmttth.Onth»besaKttwM* the probe at dOO*C with molten bismuth has been voukJ be least sensitive to these effects at a installed. Detain of this work are dmmased fe the frequency of 27.7 kHz with the ssft bmnuth later- femainder of this section. h-x A the midpoint of the detector. CaleaawJuna far ewtBrndnma awhe serfnrmnnee and swtnanai onanrflag cwnestinns, ^Tuttmittary cavensstions 3. The dc resinanceof the primary aa)d secondary cosss ware performed usteg a two-conductor niooVI consisting increases from 69.4 to 792 Q m the tiaapiratuia of a Wfilar cot inside a morybdenum tube that was mxwva! conanereu, nowevrr, oy aunenmg ma na> surrounded with either liquid bwmuth or sir. Results of 224

the cable capacitance, it was poeaMe to eseentfafly for use in the molybdenum reductive extraction system. aaMaate tins eflect (a pt*!» aMft of less than The probe, shown in Fig. 17.17, consists of a high- 0001*). density 99 J%f«e ahnaina core tube (0.720 to. 0D) on which brfitor OjOIO^dtom plattotajn wire cons are 4. fhaae shift changes of tees than 0.01* wound in 0.022-m.-wtde grooves having a depth of feted for changes of 1% m the operating frequency, 0.020 to. The active length of the probe is 13.5 to.;th e the aeaaetede of the signal hnfmstsd on the primary primary and secondary cols contain about 189 turns cot, the oatpnt impedance of the primary signal, the each. The probe was designed for insertion in a of the secondary signal, or the O-785-m.-OD, 0.72S-ta.-ID molybdenum tube on which nvivvoenum eno cap was weanea oy an csecuon beam technique (aae F*. 17.17). The toweren d of the The remits ob> probe is fitted rith an adapter that fastens the probe to from dee the probe mounttog boat and holds the hto> derig£ a prototype eiectricai connector ping for the aujtru*

PMQffO ttt*>7«

I7J7. The 22S nent cabte. The lower end of the probe tube was test chamber. The enlarged lower section, which sumi- brazed into a carton-steel adapter to attow insertion of btes the interior of the high-temperature containment the probe in a carbon-steel test vessel. When the probe vessel for the inorybdemim reductive extraction equip­ tube is installed in the molybdenum reductiveextrac ­ ment, will be filled with as inert gas. Space is provided tion system, it wftl be welded, via an electron beam for the I Mt length of hjejHeniperatnre electrical cable technique, into the diwiigagmg section below the (maximum rated service temperature, 2000*F) and for comma without u*tag an adapter. the nozzle that tfypjeetys the electrical and service penetration on the containment vessel flange. The dieted pmht performance. Experimental measurements probe wtl be installed in die test vessel as soon as have been made at room temperature to vrify the difficulties with shorting in the lugjHemperatute elec­ predicted performance of the probe. These measure- trical cable and connector plug assembly have been menu were maoe usmg me cos ano mo*yooemim roue corrected. described above. Incoaei disks 1 in. thick with s diameter of 4 m. we*e stacked on the probe to simulate increase* m the bismuth level. Difficulties were en- co*4 I7.lt, Cariea awe! vanttfst twa^snjlaejpo lunula wddmg the carbon-sted adapter to the bottom of the nit hmn».i iiamui. 18. Continuous Salt Purification

R.B. Lmdauer

Studies w*» carried out to determine the cause of the molten alt with hydrogen were continued after the %4nh iron concentrations reported for iron fluoride concentration in the salt (72-14.4-13.6

obftfcwd (taring the previously reported experi­ mole % LiF-BeF2-ThF4) was increased to about 1000 ments1 on ta* reduction of iron fluoride in molten salt ppm (which should be sufficiently high to allow by covnteicuffsnt contact with hydrogen in a packed accurate iron analysis). The pressure drop across the cotoana. Poaribk causes for the hajh iron concentration column increased significantly due to a partial restric­ art. (1) byuaartin of suspended iron particks around tion and limited the gas flow rate to about 20* of that the poorly sealed ampler filter and (2) contamination used previously with a comparable salt flow rate. Five of sah samptes with iron from tools used during iron fluoride reduction runs were carried out at the removal of salt fnav, the nickel sampler. The presence reduced gas flow rate; however, the extent of iron of suspended iron pat tides in the filtered sab appears to fluoride reduction averaged only 6% per run (see Table be ruled out by low iron concentrations (average, 68 18.1) rather than 27%, as had been observed with pom) reported for four huge (4-g), unfihered samples higher gas flow rates. With the lower gas flowrates , the taken from the system. Abo, leaching of nickel speci­ HF concentration in the exit gas stream was about 60% mens that had been exposed to the salt in the system of the equitibrium value, based on the concentration of with aqueous HCI showed only a negligible amount of iron in the exit salt stream, instead of about 27%, which iron deposited on the specimens. Therefore, it is has been noted with higher gas flow rates. During run believed that the samples are being contaminated during IS, a hydrogen flow rate of only 300 cm3/min was the removal of salt from th* nickel samplers. In order to used, and the extent of iron fluoride reduction was nriirimiie such contamination, the samplers were rede­ about 100% of that which would have been obtained if signed to obtain a larger (4-g) sample and were the salt and gas streams had been brought to equilib­ constructed of copper, which will facilitate removal of rium at the operating temperature of 700°C. The the silt. The larger alt staple should also provide average mass transfer coefficient measured in this run unproved sensrrJvrty in the analysis for iron at low was only 0.002 ft/hi as compared with about 0.018 ft/hr measured in previous runs. Experiments for measuring the rate at which iron Following these runs, the column was removed and duoride is reduced during the countercurrent contact of cut into sections in order to determine the cause of the restriction. Most of the Raschig-ring packing in the column contained salt that had not drained from the 1. R. B. LtodaMr, MSR /Vugvwn SdNfnMt. AtJgr. Rep. Feb. packing. In addition, a considerable amount of salt 28,1971, ORNL-4676, pp. 269-70. could be seen between rings in the upper part of the

226 L 227

Table 18.1. Data fr jm iron fluoride redaction rem

Iron Reduction Mass transfer Hj flow rate Salt flow rate concentration in run coefficient (bters/min) (ciii3/min) salt (ppm) No. (ft/hr) Feed Product

12 2.6 50 911 885 0.0007 13 3.5 80 88S 752 0.0056 14 3.8 78 762 740 0.0011 15 0J« 8? 740 705 0.0020 16 4.7 77 705 661 0.0028

'10% hydrogen in heMum.

column, and a bbck deposit was noted on the rings in packing (Fig. 182). Several of the salt globules from this area (see Fig. 18.1). In contrast, very little material the upper part of the column remained white after appeared to be deposited on the packing in the lower exposure to moist air; however, some of the globules part of the column; also, less salt was noted in the became rust-colored after exposure. Subsequent analy-

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•**. 18.1. View of Rasdug-ring packing mar top of packed column, tbowmg metaOfc deports nd aA tl^ dU no^ dcata how tbo packing. 228

ses of the salt for ma indicated the expect*! amcen* eJmoM uniformly throughout the column. The total nation of iron (640 pom) for the malarial (kit did not PUMUU of iron contained on the packing, based on the change color, whie two samples that bacaibe rust- average iron depoatoson, it about I? g. Idat amount of colored in appearance contained 890 and 205$ pptn of iron behaved to have been reduced in the system thus iroo.lt appeal* that ton* of the snhghibtBm contented tar h> Jbott 24 g. Therefore, it appaais that naoat of the damersed fcoa particles which oxidized on expoearr ic Iran is deposited on the cotemn packing as the FaFj is a*r. Analysis of the black deposit in the upper part of reduced. the column (afier the ineteriel had btt» exposed to air) A column of stathUv modified deafen was fabricand \mdte*A*& a nfcktl content of 49 2 wt * aad aa iron wm w^ipwwaweBWB ^aw wwegup^www BWWJB^^P^WB^F^B ^^^paiwmwa ^aio v^em^v^sv ^^p and inrtalfcd. The crosi-aactioaal ana of the lojuid costamt of 3 wi *. Analyses of packing removed »i dasntrahmiant section at the lop jf the .toaaam was • e»^nne# ewnwni* wajmn njmtavmK tjnam> nj^*^H^8elenel •••newe'egWB) gMnvni V£Se ajnn aKrnatat by T$% and was packed with a S4n. depth of Atac da t^j amr ant of daooattad iron: the deposition on teschfc rings. The wal thickness of the %4n. ttaachig. the packing ha* an avarnat thickness of 0J05 nnX The ring packing a the cohnna was dacwaaai from %« to obawad «yftsefencae in the aamnar in whack nickel and %% in., tiwikh shonM inmate the throanhmji and hon eVposiNd on iht parking nit cjnfcie reasonable since kngtheri the optrating tint before flow n mklion dm MSF* h) Hsach neon? aanllv stdnosd bv Iridranan than to reducea BBttals attceeaeattt reaeoval of e?ou from the FaPf. Mawa one «*£& expect the ticket to deport in

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