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An Improved Aqueous Process for Zirconium Alloy Nuclear Reactor Fuels Part 1

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An Improved Aqueous Process for Zirconium Alloy Nuclear Reactor Fuels Part 1 ,327 t& rir qv- , r 3' AN IMPROVED AQUEOUS PROCESS FOR ZIRCONIUM ALLOY NUCLEAR REACTOR FUELS PART 1. PRELIMINARY LABORATORY STUDIES K, L. Rohde, et a1 1- DISCLAIMER This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency Thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof. DISCLAIMER Portions of this document may be illegible in electronic image products. Images are produced from the best available original document. Available from the Office of Technical Services U. S. Department of Commerce - Washington 25, D. C. ILEGAL NOTICE Thir report wu prepand as an wrsunt of Government sponsored work. Neitbar the United I States, nor the Commission, nor any person acting on behalf of the Commirrion: A. Makes any warranty or representation, express or implied, with respect to the accuracy, oompletcnets, or uscfuhsa uf the infamdaa contained in this report, or that the w of any infortnation, apparatus, method, or procur disclosed in this report may not infringe privately owned rights; or B. Assumer any liabilities with reapt to the use of, or for damages resulting from the use I d QY ic~furrmlltr~~,atwmtr*, tntthd, or psecea direlos~dIn this rsjxigt. As used in the above, "pcraon acting on behalf of the Commission'' includes any employee or contractor of the Commission, or employee of such contractor, to che extent that such &nployte or contractor of the Commission, or employee of such contractor prepares, dtruninates, or provides access to, iuiy information' pursuant to hh employment or contract with the Commission. or his employment with such contractor. Printed in USA - ,1~0-14594 .AEC Research and Development Report chemical Separations .Processes for .Plutonium and Uraniuy TID-4500 (18th Ed. ) Issued: October 30, 1962 v \ AN IMPROVED AQUEOUS PROCESS IKIR ZIRCONIUM ALLOY NUCLEAR REACTOR FUELS PART I. PRELIMINARY LABORATORY STUDlES "Y', K. L. Rohde A. P. Roeh B. J. Newby T. L. Hoffman B. E. .Paige . L. A. ~e'cker . (K. L. Rohde, ~dftor) PHILLIPS PETROLEUM COMPANY Atomic Energy Division Contract AT ( 10- 1 ) -205 Idaho .Operations Office U. S. ATOMIC ENERGY ' COMMISSION THIS PAGE WAS INTENTIONALLY LEFT BLANK AN IMPROVED AQUEOUS FBOCESS FOR ZIRCONIUM ALLOY NUCLEAR REACTOR FUELS K. L. Rohde A. P. Roeh B. J. Newby T. L. Hoffman B. E. Paige L. A. Decker (K. L. Rohde, ~ditor) ABSTRACT The expanding use,of.Zircaloy-clad zirconium-enriched uranium alloy fuel has suggested a need for higher capacity reprocessing facilities. The most urgeri-k requirement is for continuous dissolution equipment to match the solvent extraction capacity already'available at Idaho Chemical Processing Plant. Because of the rapid dissolution ra.tes possible with aqueous hydrofluoric acid on clean metal as well as.on oxidized fuels, and subsequent flow~heeteconamics, it is the reagent.of choice. Laboratory measurements and a survey of the properties of uranium tetrafluoride indicated highest solubility in the dissolver effluent was obtained at higher total fluoride concentrations and lower fluoride- to-zirconium mole ratios. Since zirconium salts have been shown to be susceptible to precipitation at higher fluoride and zirconium concen- trations, an optimum dissolver effluent composition was selected for a Dilute Flowsheet at about 5M- total fluoride and a 1.1M- zirconium. The uperation of two bench-scale dissolvers verified the feasibility of a continuous process, 'and Monel and carpenter-20(Cb) were confirmed as suitable materials of construction for the dissolver... .Using the Dilute Flowsheet, uranium solubility equivalent to the dissolution of f'uels containing 2 per cent uranium, over.-all, was' achieved. Correlations of dissolver effluent flow rate with effluent cmpos- ition andwith total zirconium dissolved are given for guidance in .engineering scale-up .. THIS PAGE WAS INTENTIONALLY LEFT BLANK AN IMPROVED AQUEOUS PROCESS FOR ZIRCONIUM ALLOY NUCLEAR REACTOR FUELS PART I . PRELIMINARY LABORATORY STUDIES TABm OF CONTENTS Page I . SUMMARY ........................... 9 INTRODUCTION I11 • BASIC'DISSOLUTION STUDIES ................. 12 A . ..Zirconium Dissolution Rates .............. 12 1. Kinetics in Hydrofluoric Acid and Zirconium Fluoride Solutions ..................12 a . Exper~ental ..........; ........ 12 b . Results ..................... 12 2; Initiation of Reaction at Low Temperatures and . on Oxidized Surfaces ................. 16' B . Chemical Forms and . Properf ies of .Uranium Tetcafluoride . 16 1. Anhydrous Uranium Tetrafluoride........... 16 2 . Low Hydrates of Uranium Tetrafluoride ..........48 3 . Uranium ~etrafluoridiHydrate (UF~-~&~O)..... 18 . 4 . Control of Hydrate Formation ............ 18 C . Solubility of Uranium Tetrafluoride in t is solver Product Solution ........................ 19 N . SCOPING STUDIES WITH BENCH SCALF: CONTINUOUS DISSOLVERS . 19 A . Description of Equipment .................20 1. One-half-Inch-Diameter Continuous Dissolver .... 20 2 .. One-Inch-Diameter Continuous Dissolver ....... 22 B . Primary Chemical Material Balances ............ 24 C . Process Chemistry Results ............... 24 1. Variation of Effluent -zirconium Concentration with Reagent Flaw ................... 28 2 . Solution Stability with Respect to Zirconium Precipitation ................... 30 Page 3. Behavior of Uranium . 30 . a. In ~ydrofluoricAcid Alone. '. .... 30 b. In Hydrofluoric Acid with Oxidants. 31 4. Camposition of Solids in the Dissolver Effluent . 32 V. PRELIMINARY CORROSION RESULTS . 32 A. Preparation of Materials. 32 B. RE3ul.t~of Evaluation . 3 5 C. CvncPuslOns or Corrosion Studies. 42 VI. CORRELATION OF DISSOLUTION RATE DATA. 42 VII. CONCLUSIONS LIST OF'TABLES Table 1 Dissolution Rates of Zircaloy-2 at 95'~ . 14 2 .. Dissolution of Zirconium,:FueT.. .. .. .. .. ... 17 3 Conceritrated Continuous Dissolution Flawsheet for ZirconiumAlloyF'uel. 25 4 Dilute ~ont'inuobsDissolution Flawsheet for zirconium Alloy Fuel . .' . 25 5 Up-Floy Operation of $-1hch-~iamete? DiSsolvei- at 90°C 26 6 Up-Flow Operation of 1-Inch-Diameter Dissolver at 90"~27 7 Effect of Oxidizing Agents. with Hydrofluoric Acid. 33 . 8 Solids am position -Dissolution ~uniof able 5 . 34 ' 9 Corrosion of Monel and carpenter--20(Cb) During Dissolution of zirconium-uranium Fuel in Run Number 1. 36 LIST OF TABUS ( Continued) Table- Page 10 Corrosion of Monel and carpenter-20(~b)During Dissolution of Zirconium Alloy in Run Number 2 .........'... 37 11 Corrosion of Monel and carpenter-20(~b)During Dissolution of Zirconium-Uranium Fuel in Run Number 3 .......... 38 12 Corrosion of Monel and carpenter-20(~b)During Dissolution of Zircaloy-2 in Run Number 4 ............... 39 13 Corrosion of Monel and carpenter -20(~b)During Dissolution of Zircaloy-2 in Run Number 5 ............... 40 14 Corrosion of Monel and carpenter -20(~b) During Dissolution of Zirconium-Uranium Fuel in Run Number 6 ............41 LIST OF FIGURFS Figure 1 Dissolution Rate of Zircaloy-2 as a Function of Hydrofluoric Acid Concentration and as Influenced by Total Fluoride and Zirconium Content of the Solution ............. 13 2 Dis.solution Rate Constants of Zircaloy-2 as Fwnctions of Total Fluoride Concentrat ion arid Fluoride -t o-Zir conium Mole Ratio. ........................ 15 3 Solubility of Uranium ~etrafluoridein Zirconium-Hydrofluoric Acid Solutions as a Function,of Fluoride Concentration and Fluoride -to-Zir conium Mole Ratio. .............. 20 4 ~iniatureZirconium Dissolver Equipment Flow Diagram. ... 21 5 Miniature Zirconium Dissolver Details ............ 22 7 Continuous Laboratory Dissolver .............. 23 8 Continuous Dissolution of Zirconium, Effluent Camposition as a Function of SolutionVelocity ............... 28 9 Continuous Dissol'utioa of Zirconium, Correlation of Dissolution with Reagent Flow ..................... 29 LIST OF FIGURES ( ~ontinued) Page ... .10 Continuous Dissolution of uranium-~irconium, Uranium. Solubility ..........................;..31' 11 Continuous Dissolution of zirconium, correlation of . Dissolution Rate Data. ...............,-.-... ...... 44 - AN IMPROVED AQUEOUS PROCESS FOR ZIRCONIUM ALLOY NITCLEAR REACTOR FUELS PART I. PRELIMINARY LABORATORY STUDIES I. SUMMARY The continued acceptance of Zircaloy-clad zirconium-uranium alloy fuels for military propulsion reactors has suggested that a high ca- pacity process for the recovery of the fully enriched uranium fuel from this source would be required. Since a high capacity solvent extraction system is already available at the Idaho Chemical Processing Plant, the primary equipment and'process need for greater zirconium fuel repro- - cessing rates is a continuous dissolver. The well-established hydro- fluoric acid dissolution process and its assocdated solvent extraction flowsheet are preferred over other aqueous processes for this fuel.fl4) For the development of the
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