AECL-7918
ATOMIC ENERGY ^£53 L'ENERGIE ATOMIQUE OF CANADA LIMITED W^^W DU CANADA LIMITEE
EXPERIMENTS PERFORMED IN ZED-2 IN SUPPORT OF THE IRRADIATION OF (Th,Pu)O2 FUEL (BDL-422) IN NRU
Experiences effectuees dans I'installation ZED-2 pour faciliter I'irradiation du combustible (Th, Pu)O2 (BDL-422) dans le NRU
by
R.T. JONES
Chalk River Nuclear Laboratories Laboratoires nucleaires de Chalk River
Chalk River, Ontario
January 1984 Janvier ATOMIC ENERGY OF CANADA LIMITED Atomic Energy of Canada Research Company
EXPERIMENTS PERFORMED IN ZED-2 IN SUPPORT OF THE IRRADIATION OF (Th,Pu)O2 FUEL (BDL-422) IN NRU
by
R.T- Jones
Reactor Physics Branch Chalk River Nuclear Laboratories Chalk River, Ontario, KOJ 1J0 1984 January
AECL-7918 L'ENERGIE ATOMIQUE DU CANADA, LIMITEE Société de recherche de L'Energie Atomique du Canada
Experiences effectuées dans l'installation ZED-2 pour faciliter Tirradiation du combustible (Th, Pu)0p (BDL-422) dans le NRU
par
R.T. Jones
Résumé
Une boucle du NRU contenant cinq grappes de 36 éléments de combustible (Th, Pu)0? ayant un contenu fissile de 1,4% en pds a été simulée dans l'installation ZED-2. On a pu effectuer, entre autres, les mesures suivantes: (a) valeur de la rëactivité de la boucle et de son eau (H2O) de refroidissement; (b) perturbations de flux causées par la boucle; et (c) taux de réaction détaillés â l'intérieur et aux abords du combustible se trouvant dans la boucle, y compris une étude du pic de flux causé par les intervalles entre les grappes.
Laboratoires nucléaires de Chalk River Chalk River (Ontario) KOJ 1J0 Janvier 19&4 AECL-7918 ATOMIC ENERGY OF CANADA LIMITED Atomic Energy of Canada Research Company
EXPERIMENTS PERFORMED IN ZED-2 IN SUPPORT OF THE IRRADIATION OF (Th,Pu)02 FUEL (BDL-422) IN NRU
by
R.T. Jones
ABSTRACT
An NRU loop containing five 36-element bundles of (Th,Pu)02 fuel with 1.4 wt% fissile content has been simulated in ZED-2. Measurements made included:
(a) reactivity worth of the loop and its H2O coolant,
(b) flux perturbations caused by the loop, and
(c) detailed reaction rates within and about, the loop fuel including an investigation of end flux peaking caused by the inter-bundle gaps.
Chalk River Nuclear Laboratories Chalk River, Ontario KOJ 1J0 1984 January AECL-7918 - 11 -
TABLE OF CONTENTS ?age
1. INTRODUCTION 1
2. DESCRIPTION OF LATTICE, LOOP SITE AND FUEL 1
2.1 Lattice Configuration 1 2.2 The Simulated NRU Loop 1
2.3 (Th,Pu)O2 Fuel 2
3. REACTIVITY MEASUREMENTS 2
4. MACROSCOPIC FLUX DISTRIBUTION MEASUREMENTS 3
4.1 General Comments 3 4.2 Location of Detectors 3 4.3 Copper Activity Distributions 4 4.4 In/Cu Activity Ratios 4 4.5 Comments on the Results 4 5. DETAILED LOOP FINE STRUCTURE MEASUREMENT , 5
5.1 General -. 5 5.2 Loading the Removable Fuel Elements 5 5.3 Copper Activity Measurements 5 5.4 Lutetium-Manganese, Indium-Manganese Activity Measurements 6 5.5 Fission Rete Measurements . 7 5.6 Thorium Capture Measurements 7 5.7 Comments on the Results 7
6. END FLUX PEAKING MEASUREMENTS 8
6.1 Introduction 8 6.2 Geometry of the End Regions 8 6.3 Loading of Flux Detectors < 9 6.4 Results 9 6.5 Discussion of Results 9
7. ACKNOWLEDGEMENTS 11
8. REFERENCES 11 - iii -
LIST OF TABLES
Page
Table 1: Composition of BDL-422 (Th,Pu)02 Fuel 12
Table 2: Reactivity Measurements 12
Table 3: Details of the Activation Foils Used 13 Table 4: Copper Foil Activities (Reference Lattice) 14
Table 5: Copper Foil Activities (Loop H2O Cooled) 15
Table 6: Copper Foil Activities (Loop Air Cooled) 16
Table 7: Summary of Cosine Least Squares Fits to Axial Activity Distributions .... 17
Table 8: In-116/Cu-64 Activity Ratios (Reference Core) 18
Table 9: In-116/Cu-64 Activity Ratios (Loop H20 Cooled) * 19
Table 10: In-116/Cu-64 Activity Ratios (Loop Air Cooled) 20
Table 11: Copper Activities, Fine Structure Measurement
(Loop H20 Cooled) 21
Table 12: Copper Activities, Fine Structure Measurement (Loop Air Cooled) 22
Table 13: Normalized Copper Wire Activities (H20 Cooled Fine Structure) 23
Table 14: Normalized Copper Wire Activities (Air Cooled Fine
Structure) 24
Table 15: Fine Structure Activities (Loop H20 Cooled) 25
Table 16: Fine Structure Activities (Loop Air Cooled) 26
Table 17: End Flux Peaking Copper Activities (Loop H20 Cooled).. 27
Table 18: End Flux Peaking Copper Activities (Loop Air Cooled) . 28 - iv -
LIST OF FIGURES
Page
Figure 1: Plan View of the ZED-2 Lattice 29
Figure 2: Vertical Section of the Experimental Fuel String .... 30
Figure 3: Horizontal Section of the Experimental Fuel 31
Figure 4: Radial Distribution of Perturbation Factors at Elevation 1.25 m 32
Figure 5: Location of Foils in Fuel Stack for Fine Structure Measurements 33
Figure 6: Location of Copper Wires on the Aluminum Frame 34
Figure 7: Copper Activity Distribution in and around the H2O- Cooled Loop 35
Figure 8: Copper Activity Distribution in and around the Air- Cooled Loop 36
Figure 9: Azimuthal Copper Activity Distribution on the Loop Calandria Tube Outer Surface 37
Figure 10: Comparison of the Cross Sections of Lul76 amj Pu239 38
Figure 11: Fuel Bundle Construction in the Region of the Bundle- End Gaps and Location of External Flux Detectors 39
Figure 12: End Flux Peaking for the I^O-Cooled Fuel 40
Figure 13: End Flux Peaking for the Air-Cooled Fuel 41
Figure 14: Azimuthal Flux Variation and End Flux Peaking as Indicated by Longitudinal Copper Strips on an Outer Element in an Air-Cooled Bundle 42
Figure 15: Propagation of the End Flux Peaking Perturbation into the Lattice: H20-Cooled Loop 43
Figure 16: Propagation of the End Flux Peaking Perturbation into the Lattice: Air-Cooled Loop 44 1. INTRODUCTION
As part of the program to develop an advanced fuel cycle for the reactor, the Recycle Fuel Fabrication Laboratory (RFFL) at Chalk River Nuclear Laboratories has produced six 36-element bundles of (Th,Pu)02 fuel for irradiation in an NRU loop. The elements of these bundles were made available for experiments in ZED-2 prior to the irradiation. Six bundles are insufficient to allow reliable measurement of lattice parameters for this fuel. Therefore, the only experiments done were to simulate the NRU loop and its environment to provide a benchmark test for the computer codes used in NRU calculations.
The following studies were made:
(a) the reactivity effect of replacing the centre rod of a reference core with a simulation of the loop, and of voiding the light water coolant of the loop,
(b) the flux perturbation in the core caused by inserting the loop and voiding the coolant,
(c) detailed reaction rate measurements, including and U^33 fission rates, within and about the loop fuel, and
(d) end flux peaking caused by the gap between fuel bundles.
2. DESCRIPTION OF LATTICE, LOOP SITE AND FUEL
2.1 Lattice Configuration
The reference lattice used in the heavy water moderated ZED-2 reactor is illustrated in Figure 1. It consisted of 64 ZEEP rods in a non-uniform hexagonal array having the NRU pitch of 196.85 mm. This lattice was an attempt to represent a typical NRU lattice in the region of a loop.
Each ZEEP rod consisted of natural uranium metal cylinders, 32.5 mm diameter and 150 mm long stacked in a 2S aluminum alloy tube of 1 mm wall thickness. The fuel length in the rods was 2.85 m and they were suspended so that the bottom of the fuel was 150 mm above the ZED-2 calandria floor, which was the reference point for all height measurements.
The method of designating locations in the lattice is also given in Figure 1. The centre rod is thus at location K0. This was the location of the loop when it was installed.
2.2 The Simulated NRU Loop
The simulated loop and its contents are illustrated in Figure 2 (vertical section) and Figure 3 (plan). It consisted of concentric aluminum "pressure" and "calandria" tubes separated by an air gap. Five fuel
CANDU™* - CANada Deuterium Uraniuim - 2 -
bundles supported on an aluminum central support tube (CST), which was a snug fit in the holes in their end plates, were placed in the loop. To ensure that the bundles and the "pressure" tube were coaxial large aluminum washers 1.6 mm thick, which fitted snugly around the CST and into the pressure tube, were placed at the top and bottom of the stack. For some irradiations two more washers were placed at the top and bottom of the middle bundle in the stack (#3) to ensure that, in particular, it and the pressure tube were coaxial. The loop was suspended in the reactor so that the bottom of the lowest fuel bundle was 150 mm from the calandria floor. Other relevant dimensions of the loop are given in Figures 2 an<" 3.
2.3 (Th,Pu)0? Fuel
This fuel had the nominal composition (Th, 1.4 wt% Pu fissile)02. Full details of its manufacture and final composition are given in Reference 1 and are summarized in Table 1.
For these experiments the elements were assembled into 36-element bundles using special hardware. This consisted of a pair of Zircaloy end-plates 3.18 mm thick spaced apart by tie-rods of 6.55 mm diameter Zircaloy rod. The tie-rods were connected to the end-plates by countersunk aluminum screws. Holes in the end-plates located the elements by the welding nipple at each end while a central hole accommodated the CST. The geometry and some of the dimensions of the resulting bundle are given in Figure 3. Five of these bundles were assembled.
One special demountable bundle was also constructed for use in the detailed reaction-rate or fine-structure measurements. This allowed the removal of the six elements, designated Al, A2, Bl, B2, Cl and C2 in Figure 3, without completely dismantling the bundle. To achieve this the bundle was assembled using only 30 elements, the remaining 6 removable ones being inserted through large holes in one end-plate. A special extra end-plate, attached with screws, held the 6 removable elements in their correct positions.
3. REACTIVITY MEASUREMENTS
In these experiments reactivity differences are expressed as differences in critical heavy water height. To measure a critical height for a given core loading the reactor was run at a constant low power for 20 minutes before measuring the moderator height and temperature. Measurements were made with K0 empty, with a ZEEP rod at K0, and with the loop both light-water and air-cooled at K0. During the serias of measurements the core temperature and H content of the D2O moderator did not sensibly change. No correction to the measured heights has been made for buildup and decay of long lived photoneutron sources. Previous experience, and the excellent reproducibility of the repeated measurements, indicate that such corrections are very small. The estimated accuracy of a measured height change is +0.1 mm. - 3 -
The results, shown in Table 2, indicate that the light water cooled loop is slightly less reactive than a ZEEP rod but that voiding the coolant considerably increases its reactivity worth.
4. MACROSCOPIC FLUX DISTRIBUTION MEASUREMENTS
4.1 General Comments
Experiments were performed to compare axial and radial flux distributions throughout the reference lattice (ZEEP rod at KO) with those obtained with air and light-water cooled loops at KO. Activation of 11.3 mm diameter by 0.25 mm thick copper foils was used as the flux indicator. The 12.74 h Cu64 activity was counted with Nal(Tl) counters.
Tc obtain some information about the neutron spectrum and to enable the copper activities to be corrected for spectral effects, 11.3 mm diameter by 0.13 mm thick 1.0 wt% indium in aluminum foils were irradiated with some of the copper foils. In this case the activity counted was that of 54 minute ll6
Using the Westcott convention (2) to describe the neutron spectrum, the effective neutron capture cross section of Cu63 ±s given by
a = a (G g + G r/T/T s ) o r oo
1 where a0 is the cross section for 2200 m.s" neutrons, G and Gr are self shielding factors for thermal and resonance neutrons respectively, g and so are the Westcott cross section parameters, r is the epithermal index (approximately the fraction of epithermal neutrons), and T is the temperature of the Maxwellian distribution of thermal neutrons (To = 293.6 K is the neutron temperature corresponding to 2200 m.s""1). Dividing the measured relative activity by cr yields a quantity proportional to the
Westcott flux. For the copper foils used g, s0, G and Gr are given in 116 Table 3. r/T/To can be derived from the measured In /Cu64 ratios provided the Westcott and foil parameters are known for the indium activity (see Table 3) and provided r/ T/To is independently known at a reference location. Measurement of an indium cadmium-ratio gives the reference r / T/To. In these experiments symmetric lattice locations K12E and E6W were used as the reference sites. The methods for deriving r/ T/To values are given in (3).
4.2 Location of Detectors
Copper foils were located at various elevations in thin walled aluminum thimbles hung in the D2O moderator at lattice locations K4W, K1W, K1E, K2E, K4E, K6E, K10E, K12E, F5W, E6W and P5W as indicated in Figure 1. They were also taped to the N, S, E and W sides of ZEEP rods at K10W, K8W, K6W, K2W and K8E and to the loop or ZEEP rod at KO. Precise locations of all foils used are given in the tables of measured activities (Tables 4, 5 and 6). - 4 -
Indium/copper ratios were measured across the core at the above locations at elevation 1.25 m.
4.3 Copper Activity Distributions
The copper activities obtained in the three situations—ZEEP rod, light water cooled loop and air-cooled loop at KO—are given in Tables 4, 5 and 6 respectively. In each case the activities are normalized to that at elevation 1.35 m in the thimble at K12E.
Full axial distributions were measured at 0.1 m intervals in thimbles at K1W, K6E and P5W and on the loop calandria tube at KO. The function A(z) = A(z0) cos a(z-zo) was least squares fitted to these data yielding the square root of the axial buckling, a , and the elevation above the calandria bottom of the maximum flux, z0. From these and the critical moderator height, Hc, upper, lower and total extrapolation lengths were obtained:
-( V15)
where H = -g— is the extrapolated height. It should be noted that
Sz±t as defined above, is measured from the bottom of the fuel not the calandria floor.
The data obtained from the axial fits are summarized in Table 7.
4.4 In/Cu Activity Ratios
The measured ratios for the three cores are given in Tables 8, 9 and 10. Indium cadmium-ratios and derived W T/To values for the reference location and for the other locations are also given.
4.5 Comments on the Results
As an illustration of the flux perturbation due to the insertion and voiding of the loop, perturbation factors have been calculated and plotted in Figure 4. The factors are calculated for data at elevation 1.25 m and are defined as
A(K12E) A(K12E) * A(R) reference „ 5 -
where R is radial position in the core and A is copper activity. Figvre 4 shows that the loop causes a large perturbation and so does voiding the coolant. The perturbation is so large that the assumption that the flux is unperturbed at K12E, implied by normalizing to that position, is in doubt. Perhaps the most surprising result is the magnitude and extent of the additional perturbation caused by voiding the loop.
T The Westcott rV /To values derived from the In/Cu ratios indicate a pronounced hardening of the spectrum in the region extending one to two lattice pitches from the loop compared to the reference case. The hardening is greater with the coolant voided. If the ry^T/T^ values were used to correct copper activities to fluxes the largest ry/T/To value measured (0.052) would correspond to a correction of 2.4%.
5. DETAILED LOOP FINE STRUCTURE MEASUREMENT
5.1 General
These measurements represent a fairly detailed study of the neutron distribution in space and energy in and around the loop fuel. Measurements were made with the loop "cooled" by light water and by air. The special demountable bundle was used in position #3 with the element designated Cl in Figure 3 oriented to the N. The special washers were placed at the top and bottom of the bundle to ensure that it was centralized in the pressure tube. Each of the six removable elements contained one foil of each of the following materials Lu-Mn-Al, In-Al, U233-A1, Pu-Al, Th and Cu. Details of the foils are given in Table 3. In addition, foils of each type were irradiated on a rotating aluminum wheel at a reference location. This was chosen to be at the extreme W-side of the reactor, at least 0.4 m from the nearest fuel rod, where the neutrons were well thermalized and assumed to be at the temperature of the moderator. The r-value of the neutron spectrum of the reference location was found by indium-cadmium ratio to be 3.1 x 10~4.
5.2 Loading the Removable Fuel Elements
Because of the toxicity of plutonium the removable elements were loaded in the RFFL. The foils were all wrapped in at least one layer of 0.03 mm thick aluminum foil to reduce contamination and were placed between special flat ended fuel pellets. The balance of the fuel stack was standard pellets with dished ends. The foils were located one pellet length apart (typically 11 mm) around the mid-plane of the bundle as shown in Figure 5. After welding on the end plugs the elements were shipped to ZED-2 for bundle assembly and irradiation.
Within two hours of the end of the irradiation they were returned to the RFFL to be opened and have the foils removed. The alumimum wrappers were discarded before placing the foils in Lucite counting trays. The trays were checked for contamination before removal for counting. - 6 -
5.3 Copper Activity Measurements
In addition to the foils in the fuel elements, 11.3 mm diameter foils were placed at various elevations in thimbles at K4W, K2E, K4E, K6E, K10E and F5W and on the west side of the calandria tube of the .loop. These measurements duplicated some of those made in the macroscopic flux distribution measurements and enable those measurements to be normalized to these. The full axial distributions measured at K6E and KO were fitted with the function described in Section 4.3. The derived parameters are given in Table 7.
Detailed activity distributions in the moderator around the loop were made with 10 mm long, 0.76 mm diameter, copper wires taped to the arms of an aluminum frame. The geometry and orientation of the frame is illustrated in Figure 6. It was taped to the loop calandria tube at elevation 1.4m.
To check the azimuthal variation of the flux at the calandria tube a copper band, 5 mm wide by 0.13 mm thick was taped around it at elevation 1.3 m. After irradiation the band was cut into 42 pieces which were counted two at a time to give activities at 21 equally spaced positions.
All copper activities were internormalized by irradiating examples of each indicator type on the reference wheel.
The results from the circular foils are given in Tables 11 and 12 for the H2O- and air-cooled cases respectively. The normalization is such that the sum of all activities at elevation 1.35 m is the same as the sum of the equivalent activities from the corresponding macroscopic flux distribution measurement. Copper wire activities are given in Tables 13 and 14 and are plotted with some other activities in Figures 7 and 8. The normalization is the same as above. The azimuthal variation of the flux around the calandria tube is illustrated in Figure 9 which shows the thermal flux depression caused by the nearest neighbour ZEEP rods, and that no unexpected flux tilts are present.
5.4 Lutetium-Manganese, Indium-Manganese Activity Measurements
In addition to the Lu-Mn-Al foils in the fuel elements and on the reference wheel two were attached to the N and S sides of the loop calandria tube. The measured activities are given in Tables 15 and 16 for the H2O and air cooled cases respectively. Normalization is to the activities measured on the reference wheel. Also given in the tables are the Lu /Mn (R,,U) and _ _, - - T Mn and In /Mn (Rj, ) activity ratios. These have been converted to the Westcott spectral indices r and T using the method detailed in Reference 3. The cross section data required to do this in the form of Westcott g and s values as a function of T were obtained from Reference 2 excepting s0 for indium for which the value 18.8 (Reference 3) was used. - 7 -
5.5 Fission Rate Measurements
Fission product gamma-ray activities were integrally counted in a pair of 102 mm diameter by 31 mm thick Nal(Tl) counters with discriminator levels set at 1.25 MeV. As the fission products have a range of half-lives, radioactive decay cannot be explicitly corrected for. A simple correction was made by counting from first to last foil for a fixed time and then in reverse order. This constitutes one full count cycle. After correcting the counts for room and natural backgrounds and for counter dead-time the two counts of each foil were summed- This method of decay correction is equivalent to assuming that the activity decay is linear over the count cycle. Each foil was counted for many full count cycles. The activities of the U233-A1, Pu-Al and Th foils, so measured, are given in Tables 15 and 16 for the H20-cooled and air-cooled cases respectively. For the 17^33 ancj Pu-Al foils the normalization is to the reference wheel location activity. Also given is Ry", the ratio of Pu to U233 fission product activity. It should be noted that the U233_AI foils were rather smaller in diameter than the fuel pellets (11.53 mm cf. 12.07 mm). They were, however, concentrically located.
The thorium fission activity is, of course, caused by fast neutrons and is unnormalized.
5.6 Thorium Capture Measurements
The thorium foils were counted with a Ge(Li) detector to measure neutron capture rates in thorium in the fuel elements relative to that at the reference wheel location. Decays of Pa233 (the daughter of Th^33) to U233 Were measured using the prominent 311.9 keV gamma ray peak which accompanies this decay. The results are given in Tables 15 and 16.
5.7 Comments on the Results
The activities measured in the fuel bundle indicate that there were net thermal neutron flux gradients across the bundle. For instance the ratio of activity measured in pin Cl to that in C2 is typically 1.02 in the air cooled case and 0.98 in the water cooled case. These differences are significant when compared with the estimated counting error which is typically ;f0.2%. It is believed that they arise because of a combination of steep flux gradients and difficulty in controlling the geometry of the fuel bundle and pressure-tube calandria-tube assembly sufficiently well.
The derived r and T values show the expected variation with position in the bundle. It is interesting that the highest r value (0.203) is measured in the inner elements with the H2O coolant. This high r value corresponds to a copper activity to flux correction factor of about 0.93. Another effect of the high r value is that resonance activation of Mn55 becomes significant ("» 12% for r = 0.2). Proper accounting for this is necessary if accurate values of the neutron temperature are to be derived from R|£. - 8 -
Indeed it is likely that the Westcott representation of the neutron spectrum as a Maxwellian of some temperature coupled to a 1/E tall is inadequate for a highly absorbing fuel bundle containing large amounts of plutoniura. In particular the Pu^39 absorption resonance at 0.3 eV will cause a flux depression around that energy which will deepen as the centre of the bundle is approached. The measurements show that this effect predominates over hardening of the thermal neutron spectrum since U R£ decreases as the bundle centre is approached. U233 j,as a 1 Pu — cross section in the thermal region so that one would expect R to increase (this is still true when epithermal fission is accounted for using the r-values generated from In-Mn ratios). It is also important to realize that the flux depression caused by the Pu^39 absorption resonance may also influence the measured Lul?6 activations. This is qualitatively illustrated in Figure 10 which compares the absorption cross sections of the two isotopes. Any reduction in Lu^?? activity would lead to an underestimate of the derived neutron temperature. However, as already pointed out the Westcott convention probably gives an inappropriate description of the neutron spectrum. Derived values of r and T should therefore be used very cautiously.
6. END FLUX PEAKING MEASUREMENTS
6.1 Introduction
There are axial gaps between the fuelled regions of the bundles in the string. The gaps contain materials of low neutron absorption cross section compared with that of the fuel. Such an arrangement causes the neutron flux to peak in the gaps and hence at the end of the fuel stacks. To avoid overrating the fuel It is important to be able to estimate the end flux peaking. The degree of end flux peaking depends on the bundle geometry, the size of the Inter fuel gaps, the neutron interaction cross sections of the materials in the gap and those of the fuel materials. Previous measurements (4, 5, 6) have covered various bundle geometries, gap sizes and gap materials but have been limited to uranium fuels (mostly natural uranium). The present fuel has a much higher neutron absorption cross section than natural uranium (~3.7 times that of natural oxide) and may therefore be expected to exhibit more severe end flux peaking.
6.2 Geometry of the End Regions
Details of the bundle construction are given in Figure 11. The ends of each element are different; one has a resistance welded end cap 3.00 mm thick, which is in place before the pellets are loaded, while the other has a TIG welded cap 12.70 mm long. The bundles were assembled with all the TIG welds at the same end which was arranged to be the top of each bundle in the vertical string of five bundles. Thus the additional gap between pellet stack and end plug (typically 2.5 mm) was assumed to always be at the TIG welded end. Extra spaces between the pellet stack and end plugs were provided in the outer ring of elements by zirconium plenum-definers and graphite discs as shown in Figure 11. — Q •-•
The measurements were made on the gap between bundles number 2 and 3 in Figure 2, the flux detectors being placed in the special demountable bundle number 3. To centre the bundle in the channel the 1.50 mm thick aluminum spacer washer was used and must be included in the gap. For the outer ring fuel elements the gap is 54.2 mm wide while for the inner rings it is 26.2 mm.
6.3 Loading of Flux Detectors
The main flux detectors used were copper foils 12.01 mm in diameter (see Table 3) wrapped in 0.03 mm thick aluminum foil placed between pellets in the 6 removable elements of the demountable bundle. The loading procedure is described in Section 5.2 and foil positions are given in the tables of results (Tables 17 and 18). Thin zirconium discs were placed at the bottom of the stacks to facilitate removal of the adjacent foil. They added 0.51 mm to the gap for the removable elements.
The foils placed between pellets provide the best measurement of the end flux peaking. It is, however, often inconvenient to have to open elements to install them; therefore it was decided to also make measurements by attaching detectors to the outside of the sheaths and to compare the results. To this end copper bands 5 mm wide were attached with adhesive tape around the removable elements at the locations indicated in Figure 11. In one further irradiation witn the air-cooled loop, longitudinal strips were attached to the elements at four azimuthal locations as shown in Figure 11.
6.4 Results
Measurements were made for both the light water and air-cooled loop. The measured activities and locations of the detectors are given in Tables 17 and 18 respectively. Normalization is such that the average activity of two foils near the middle of the bundle in the inner ring of elements (Al and A2) is unity.
Before counting, the azimuthal bands were cut into four equal pieces. The activities given in Tables 17 and 18 are the total of the four pieces normalized in a similar way to the foils.
The axial strips were cut into pieces 5 mm long which were counted separately. These were only irradiated in the air-cooled case and the activities given in Table 18 are the sum of the four pieces at each elevation normalized to unity at the middle of the pin.
6.5 Discussion of Results
A measured axial flux distribution in ZED-2, *$> (z), may be considered to be separable into two parts: a global flux,
©
where 4>e(z) is assumed to have the form cos Ct(z-z0) as described in Section Z.3.
The results of the end flux peaking measurements for the H2O- and air- cooled loops are illustrated in Figures 12 and 13 respectively. The copper activities have been corrected for a cosine global flux variation using parameters for the cosine obtained from the fit to the measured activities on the ZEEP rod at K2W (see Table 7). Normalization to unity for measurements on the inner pins at the bundle centre has been maintained. Because the measurements were made over a small axial region near the axial flux peak the global flux correction was small (-^1.8%).
Considering the results obtained from the foils in the fuel stacks and defining end flux peaking as the ratio of copper activity at the stack end to the asymptotic value at its centre a value of 1.65 is obtained for the H2O cooled outer elements. For the middle and inner rings the ratios are even higher (2.70 and 3.10 respectively), so much so that the flux at the end of the middle ring pins is some 33% higher than, that at the centre of the outer elements. In the air-cooled case values for the end flux peaking are lower: 1.41, 2.08 and 2.24 for the outer, middle and inner fuel rings.
The results obtained from the copper strips are also shown in Figures 12 and 13. These show that measurements made on the outside of the fuel sheath can give a measure of end flux peaking that compares well with that derived from foils in the fuel stack. They also allow information about the azimuthal variation of the flux around a fuel pin to be obtained. This is indicated by the error bars in Figures 12 and 13 which actually show the spread in activity of the four pieces into which each azimuthal band was cut. A further illustration of this is given in Figure 14 where the activities obtained from the axial copper strips on an outer element in an air-cooled irradiation are shown. These indicate a peak to average activity ratio of 1.37 at the centre of the pin. For the H20-cooled case the ratio (1.24) is lower but still significant.
In Figures 15 and 16 the propagation of the end flux peaking perturbation into the lattice is illustrated for the H20-cooled and air-cooled loops. The data are copper activities from Tables 5 and 6 corrected for the global flux variation using the cosine parameters derived from the fit to the data for the ZEEP rod at K2W. The three curves for each case represent the fine structure flux on the west side of the loop calandria tube, at the cell boundary (K1WJ, and on the east side of the nearest neighbour ZEEP rod at K2W. The perturbation is largest for the air-cooled case and is readily detectable, in both cases, at the cell boundary. In neither case is it readily detectable at the nearest neighbour fuel rod where the scatter of the points indicates that it is ^ 1% for the H2O case and ~< 2% for the air. - 11 -
7. ACKNOWLEDGEMENTS
The performance of these experiments and their reporting involves the timely and much appreciated efforts of many people- This is particularly true of the fine structure measurements where, in one day, foils previously loaded into elements at the RFFL are irradiated in ZED-2, shipped to the RFFL for unloading and returned to building 145 for counting to begin. This involves close liaison between the staffs of: the ZED-2 Reactor, the RFFL, Radiation and Industrial Safety Branch, Transportation Branch and the Reactor Physics Data Acquisition Laboratory. The author extends his thanks and appreciation to all those involved, in particular to P.D.J. Ferrigan, E.J. Pleau and D.J. Roberts of the ZED-2 Reactor, to L.R. Norlock, R.J. Stack and the rest of the staff of the RFFL under the direction of A.M. Ross, and to D.A. Kettner and G.A. Doncaster for most valuable assistance during all phases of the experiment in particular with foil handling and counting.
In the production of this report I wish to acxnowledge the help of D.E. Goldberg, who drew the figures, and S. Prenger who typed the text.
8. REFERENCES
1. Norlock, L.R. and R.J. Stack. Private communication.
2. Westcott, C.H. Effective Cross Section Values for Well-Moderated Thermal Reactor Spectra. Atomic Energy of Canada Limited, Report AECL-1101 (1960).
3. Bigham, C.B., Chidley, B.G. and R.B. Turner. Experimental Effective Fission Cross Sections and Neutron Spectra in a Uranium Fuel Rod: Part II, CANDU Type Uranium Oxide Clusters. Atomic Energy of Canada Limited, Report AECL-1350 (1961).
4. Robertson, L.P. and R.E. Green. Some "Flux Peaking" Experiments in Cluster Type Fuel Rods. Atomic Energy of Canada Limited, Report AECL 925 (1959).
5. French, P.M. Measurements of Bundle End Flux Peaking in 37-Element CANDU PHW Fuel. Atomic Energy of Canada Limited, Unpublished Internal Report CRNL-1378 (1975).
6. Kay, R.E. NRX Analysis Support Experiments Performed in ZED-2: Description of Experiments and Results. Atomic Energy of Canada Limited, Report AECL-6208 (1978). - 12 -
Table 1
Composition of BDL-A22 (Th,Pu)02 Fuel
Isotopic Composition Nuclide wt%
Th-232 86.051 Pu-238 .002 Pu-239 1.181 Pu-240 .303 Pu-241 .045 Pu-242 .008
0 12.410 •
Pellets
Density 9.46 g.cn Diameter 12.115 + 0.012 mm
Table 2
Reactivity Measurements
D20 Date Time Core Power Temperature Purity He (W) (wt X) (m)
82-01-26 14:31 K0 empty 5 21.15 99.495 2.65394
82-01-26 16:04 Air cooled 5 21.18 99.495 2.43961 Loop K0
82-01-27 09:44 K0 empty 5 21.14 99.495 2.65411
82-01-27 11:01 ZEEP K0 5 21.12 99.495 2.52376
82-01-27 13:24 Air-cooled 5 21.11 99.495 2.43968 Loop K0
82-01-27 15:03 H20~Cooled 21.10 99.495 2.56209 T ~~m vn Table 3
Details of the Activation Foils Used
Foil Material wt% Diameter Thickness Self Shielding Factors Westcott Parameters Comments (mm) (mra) Gr g so
Cu 100 11.3 0.257 0.975 0.51 1.00 0.89 Flux Plots Cu 100 12.01 0.257 0.975 0.51 1.00 0.89 Fine Structures
In-Al 1.0 In 11.3 0.13 0.999 0.944 1.019 18.8 Flux Plots In-Al 1.0 In 12.01 0.127 0.998 0.932 * 18.8 Fine Structures l Lu-Mn-Al 3.0 Lu 0.987 Lu 0.984 * ** 12.01 0.25 t—• 4.932 Mn Mn 0.888 1.00 ** LO 1 Pu-Al 3.0 PU 12.01 0.127 Pu isotopic atom % 239 Pu 94.4 Pu240 5.4 Pu241 0.2 233 U -Al 2.47 11.53 0.254
Th 100 12.01 0.120
* g(T) polynomial from Westcott, AECL-1101 (2). ** s(T) polynomial from Westcott, AECL-1101 (2). Table 4
Copper Foil Activities (Reference Lattice)
Elevation Above Thimbles ZEEP Rods Calandria Floor (cm) K4W K1W K1E K2E K4E K6E K10E K12E ]F5W E6W P5W K2W-E K10H K8W 1<6U K2W K0 K8E
265 0.0429 0.0395 0.0286 0.0333 255 0.0615 0.0559 0.0393 0.0375 245 0.3426 0.3177 0.2024 0.2090 235 0.609 0.567 0.3586 0.3686 225 0.871 0.803 0.510 0.523 215 1.114 1.035 0.651 0.666 205 1.348 1.243 0.788 0.812 195 1.550 1.439 0.909 0.940 185 1.748 1.621 1.017 1.047 175 1.914 1.772 1.110 1.144 165 2.037 1.902 1.192 1.231 155 2.164 2.009 1.260 1.302 145 2.251 2.085 1.306 1.348 135 2.377 2.296 2.386 2.545 2.383 2.136 1.301 1.000 1 .346 0.994 1.344 1.390 N 0.744 0.954 1 .187 1.381 1 .412 0.920 125 2.401 2.315 2.410 2.554 2.413 2.155 1.327 0.998 1 .335 1.003 1.353 1.399^—S 0.735 0.967 1 .161 1.385 1 .425 0.951 115 2.411 2.302 2.384 2.551 2.415 2.152 1.338 0.995 I .313 0.997 1.347 1.396 N^-E 0.771 0.993 1 .217 1.399 1 .423 0.952 105 2.279 2.115 1.3U 1 .276 1.326 1.371 X W 0.706 0.933 1 .141 1.383 1 .412 1.002 95 2.196 2.054 1.288 1.324 85 2.104 1.960 1.232 1.271 75 1.973 1.834 1.159 1.192 65 1.821 1.679 1.065 1.098 55 1.647 1.528 0.961 0.991 45 1.444 1.334 0.838 0.870 35 1.217 1.131 0.718 0.742 25 0.998 0.920 0.586 0.603 15 0.806 0.701 0.446 0.587 Table 5
Copper Foil Activities (Loop HjO Cooled)
Elevation Above Thimbles Fuel Rods Loop Calandria Floor (cm) K4W K1W K1E KZE K4E K6E K1OE KI2E K10W K8W ]K6W K2W 1 K8E K2W-E K0-W
255 0.13<>4 0.1605 0.1043 0.0953 245 0.3434 0.4131 0.2637 0.2430 0.2775 235 0.540 0.654 0.4155 0.3882 0.4308 225 0.737 0.,883 0.559 0.522 0.582 215 0.935 1.102 0.698 0.648 0.790 205 1.091 1.305 0.824 0.773 0.861 195 1.227 1.,489 0.943 0.880 0.974 185 1.371 1.,657 1.045 0..972 1.,091 175 1.504 1.,798 1.141 1.,065 1.,198 I 165 1.645 1..919 1.218 1.136 1.393 155 1.690 2..013 1.275 1..197 1..352 145 1.736 2,.084 1.320 ,N 0.742 0.962 1.186 1,.291 1.426 0.948V 1.,233 1..390 135 2.364 1.769 1.855 2.364 2.363 2..126 1.339 1.000 1.342 0.994 1.351 /> 0.738 0.970 1.168 1,.292 1.449 0.964A 1..248 1..411 125 2.387 1.787 1.872 2.391 2.377 2,.137 1.345 1.002 1.350 0.997 1.355 ^-E 0.769 0.996 1.214 1..268 1.455 0.920-%...268 1..428 115 2.364 1.815 1.900 2.376 2.368 2,.123 1.337 0.994 1.342 0.988 1.352 XW 0.708 0.933 1.139 1..329 1.428 1.002 "'1,,266 1,.532 105 1.747 2,.080 1.309 1.314 1.325 1.228 1,.394 95 1.685 2.014 1.282 1,.231 1,.326 85 1.601 1.918 1.219 1,.131 1,.257 75 1.504 1.803 1.,149 1.072 1.184 65 1..416 1.652 1.,058 0.978 I.191 55 1.253 1.490 0.950 0.883 0.988 45 1..087 1.309 0.,832 0.777 0.858 35 0..918 1.101 0.,708 0.656 0.727 25 0.,763 0.897 0..575 0.537 0.602 15 0.,656 0.687 0..440 0.536 0.569 Table 6
Copper Foil Activities (Loop Air Cooled)
- Elevation Above Thimbles Fuel Rods Loop Calandria Floor (cm) K4W K1W K1E K2E K4E K6E K10E K12E F5W E6W P5W K10W K8H ]!C6U K2W 1•CO K8E •12W-E KO-W
245 0.0830 0.1051 0.0687 0.0666 0.0631 235 0.2835 0.3869 0.2417 0.2271 0.1849 225 0.4778 0.651 0.4062 0.3797 0.3085 215 0.681 0.909 0.562 0.526 0.4768 205 0.830 1.147 0.713 0.665 0.534 195 0.976 1.369 0.847 0.79? 0.624 185 1.119 1.568 0.969 0.908 0.714 175 1.253 1.747 1.078 1..014 0.811 l—• 165 1.413 1.905 1.177 1.,112 1.001 155 1.468 2.024 1.262 1..186 0.950 J 145 1.513 2.124 1.316 1..235 0.967 135 2.471 1.559 1.672 2.,432 2.470 2.191 1.341 1.000 1.346 0.999 1.356 /N 0.754 0.975 1.192 1.338 1.028 0.983-~^ 1.,278 0.999 125 2.504 1.594 1.707 2..469 2.506 2.223 1.364 1.012 1.366 1.018 1.380^-S 0.753 0.982 1.212 1.352 1.030 0.994 —5a.,296 1.033 115 2.518 1.654 1.769 2..488 2.510 2.230 1.369 1-015 1.371 1.014 1.388 N>E 0.782 1.006 1.248 1.296 1.047 0.936
Summary of Cosine Least Squares Fits to Axial Activity Distributions
a Fitted Region He 6z0 6*u 6zi T D2O Purity Experiment Location (m) (m) (m (m) (m) (a) rC) wt X
Flux Plot (H2O) Thimble K1W 0.45 2.05 2.5915 .147 1.247 0.297 0.025 0.272 20.2 99.488 Thimble K6E 0.45 2.05 .142 1.250 0.309 0.034 0.275 Thimble P5W 0.45 2.05 .143 1.246 0.307 0.029 0.278 ZEEP Rod K2W-E 0.45 2.05 .146 1.246 0.300 0.025 0.275 Loop KO 0.45 2.05 .158 1.252 0.271 0.019 0.252
Flux Plot (Air) Thimble K1W 0.45 1.95 2.4665 .192 1 186 0.319 0.037 0.282 20.3 99.489 Thimble K6E 0.45 1.95 .196 1 189 0.310 0.036 0.274 Thimble P5W 0.45 1.95 .195 1 184 °0.312 0.032 0.280 ZEEP Rod K2W-E 0.45 1.95 .195 1.184 0.312 0.032 0.280 Loop KO 0.45 1.95 .203 1 191 0.295 0.030 0.265
Flux Plot (Ref) Thimble K1W 0.45 2.05 2.5505 .156 1 227 0.317 0.035 0.282 21.1 99 491 Thimble K6E 0.45 2.05 .164 1 227 0.29R 0.026 0.272 Thimble P5W 0.45 2.05 .157 1 226 0.315 0.033 0.282 ZEEP Rod K2W-E 0.45 2.05 .158 1 226 0.312 0.032 0.280
Fine Structure (H20) Thimble K6E 0.45 2.05 2.5830 .155 1 246 0.287 0.023 0.264 20.0 9S 489 Loop KO 0.45 2.05 .165 1 265 0.264 0.030 0.233
Fine Structure (Air) Thimblfi K6E 0.45 2.05 2.4658 .194 1 186 0.315 0.036 0.280 20.5 99 488 Loop KO 0.35 2.05 .191 1 191 0.322 0.044 0.278 - 18 -
Table 8
In-116/Cu-64 Activity Ratios (Reference Core)
In-116 In/Cu 1 Location Activ- -/ Activity Ratio r/~T/To
K4W 2.5212 1.050 0.0095 K1W 2.6122 1.128 0.0146 K1E 2.6931 1.117 0.0139 K2E 2.7413 1.073 0.0110 K4E 2.5444 1.054 0.0098 K6E 2.1852 1.014 0.0071 Thimbles K10E 1.4289 1.077 0.0113 K12E 1.0000 1.002 0.0064 F5W 1.4439 1.082 0.0116 E6W 0.9997 1.003 0.0064 P5W 1.4656 1.083 0.0117
K10W-E 0.9529 1.236 0.0218 K8W-E 1.2006 1.209 0.0200 ZEEP K6W-E 1.3976 1.148 0.0160 Rods K2W-E 1.7551 1.255 0.0231 KO-E 1.8117 1.273 0.0243 K8E-W 1.1718 1.169 0.0174
Average Cd-Ratio (Thimbles K12E, E6W) = 10.79 + 0.13. Corresponding r / T/To = 0.00639. Activities measured at elevation 1.25 m. - 19 -
JTable 9
In-116/Cu-64 Activity Ratios (Loop H2O Cooled)
In-116 In/Cu Location Activity Activity Ratio r / TVT'O
K4W 2.4887 1.043 0.0093 K1W 2.2681 1.269 0.0243 K1E 2.3277 1.243 0.0226 K2E 2.6533 1.110 0.0137 K4E 2.5043 1.054 0.0100 K6E 2.1837 1.022 0.0079 Thimbles K10E 1.4477 1.076 0.0115 K12E 1.0000 0.998 0.0063 F5W 1.4435 1.069 0.0110 E6W 0.9906 0.994 0.0061 P5W 1.4682 1.084 0.0120
K10W-E 0.9509 1.237 0.0222 K8W-E 1.1932 1.198 0.0196 ZEEP K6W-E 1.4094 1.161 0.0171 Rods K2W-E 1.7009 1.341 0.0291 K8E-W 1.1898 1.195 0.0194
KO-N 1.9556 1.371 0.0312 Loop S 1.9394 1.338 0.0289 E 1.9593 1.347 0.0295 W 1.9443 1.362 0.0306
Average Cd-Ratio (Thimbles K12E, E6W) = 11.07 + 0.16. Corresponding r /T/To = 0.00621. Activities measured at elevation 1.2 5m. - 20 -
Table 10
In-116/Cu-64 Activity Ratios (Loop Air Cooled)
In-116 In/Cu Location Activity Activity Ratio r^
K4W 2.6081 1.042 0.0103 K1W 2.2164 1.390 0.0338 K1E 2.3405 1.371 0.0325 K2E 2.8555 1.157 0.0180 K4E 2.5897 1.033 0.0097 K6E 2.2600 1.017 0.0086 Thimbles K10E 1.4467 1.061 0.0115 K12E 1.0000 0.988 0.0067 F5W 1.4665 1.074 0.0124 E6W 0.9991 0.981 0.0062 P5W 1.4598 1.058 0.0113
K10W-E 0.9653 1.234 0.0232 K8W-E 1.2068 1.200 0.0209 ZEEP K6W-E 1.4053 1.126 0.0159 Rods K2W-E 1.8514 1.429 0.0365 K8E-W 1.2212 1.181 0.0196
KO-N 1.6721 1.627 0.0502 Loop S 1.6801 1.631 0.0505 E 1.6967 1.621 0.0498 W 1.7004 1.646 0.0515
Average Cd-Ratio (Thimbles K12E, E6W) = 10.76 + 0.21. / Corresponding r V T7T0 = 0.00642. Activities measured at elevation 1.25 m. Table 11
Copper Activities, Fine Structure Measurement (Loop H2O Cooled)
Elevation Thimbles Loop (cm) K4W K2E K4E K6E K10E F5W K0-W Cl C2 Bl B2 Al A2
255 0.1396 245 0.3926 0.2676 235 0.633 0.4263 225 0.870 0.585 215 1.095 0.789 205 1.292 0.872 195 1.475 0.978 I 185 1.653 1.088 175 1.794 1.196 165 1.924 1.380 155 2.018 1.339 145 2.320 2.309 2.311 2.100 1.309 1.302 1.377 135 2.362 2.378 2.369 2.140 1.338 1.328 1.411 0.532 0.549 0.2692 0.2751 0.1816 0.1831 125 2.393 2.388 2.368 2.149 1.350 1.340 1.426 115 2.137 1.527 105 2.106 1.377 95 2.040 1.301 85 1.917 1.224 75 1.810 1.131 65 1.660 1.149 55 1.493 0.956 45 1.313 0.833 35 1.106 0.709 25 0.897 0.593 15 0.691 0.570 Table 12
Copper Activities, Fine Structure Measurement (Loop Air Cooled)
Thimbles Loop K4W K2R K4E K6E K10E F5W KO-W Cl C2 Bl B2 Al A2
245 0.1053 0.0607 235 0.3845 0.1837 225 0.648 0.3066 215 0.902 0.4735 205 1.142 0.535 195 1.363 0.623 185 1.559 0.714 175 1.736 0.809 IS3 165 . 1.897 1.003 I 155 2.021 0.942 145 2.400 2.373 2.390 2.116 1.302 1.310 0.963 135 2.466 2.450 2.468 2.180 1.345 1.348 0.993 0.6065 0.5967 0.3846 0.3794 0.3032 0.3017 125 • 2.506 2.501 2.512 2.220 1.365 1.370 1.023 115 2.229 1.165 105 2.196 1.025 95 2.137 0.974 85 2.045 0.931 75 1.931 0.888 65 1.784 0.930 55 1.619 0.749 45 1.421 0.644 35 1.201 0.548 25 0.980 0.469 15 0.752 0.538 - 23-
Table 13
Normalized Copper Wire Activities H2O Cooled Fine Structure
Radial Radial Direction Position Activity Direction Position Activity (cm) (cm)
N 30°E 6.5 1.415 N 20.0 2.217 N 30°E 7.0 1.515 N 21.0 2.247 N 30°E 8.0 1.639 N 30°W 6.5 1.461 N 30 °E 9.0 1.737 N 30°W 7.0 1.541 N 30°E 10.0 1.807 N 30°W 8.0 1.698 N 30°E 11.0 1.865 N 30 °W 9.0 1.815 N 30°E 12.0 1.879 N 30°W 10.0 1.911 N 30°E 13.0 1.891 N 30 °W 11.0 1.998 N 30°E 14.0 1.872 N 30°W 12.0 2.080 N 30°E 15.0 1.818 N 30°W 13.0 2.139 N 30°E 16.0 1.738 N 30°W 14.0 2.196 N 30°E 17.0 1.604 N 30 °W 15.0 2.263 N 6.5 1.434 N 30°W 16.0 2.308 N 7.0 1.507 N 30°W 17.0 2.326 N 8.0 1.637 N 30°W 18.0 2.362 N 9.0 1.753 N 30°W 19.0 2.367 N 10.0 1.843 N 30°W 20.0 2.419 N 11.0 1.914 N 30 °W 21.0 2.429 N 12.0 1.985 Cell Boundary N 30°W to N 1.916 N 13.0 2.028 1.933 N 14.0 2.077 •• 1.939 N 15.0 2.103 Cell Boundary N to N 30°E 1.910 N 16.0 2.141 1.862 N 17.0 2.167 1.803 N 18.0 2.196 N 19.0 2.209 - 24 -
Table 14
Normalized Copper Wire Activities Air Cooled Fine Structure
Radial Radial Direction Position Activity Direction Position Activity (cm) (cm)
N 30°E 6.5 1.011 N 20.0 2.299 N 30°E 7.0 1.141 N 21.0 2.303 N 30 °E 8.0 1.353 N 30°W 6.5 1.045 N 30°E 9.0 1.515 N 30°W 7.0 1.188 N 30°E 10.0 1.628 N 30 °W 8.0 1.401 N 30°E 11.0 1.728 N 30°W 9.0 . 1.594 N 30 °E 12.0 1.766 N 30 °W 10.0 1.736 N 30°E 13.0 1.818 N 30°W 11.0 1.851 N 30°E 14.0 1.829 N 30 °W 12.0 1.975 N 30°E 15.0 1.799 N 30°W 13.0 2.075 N 30°E 16.0 1.685 N 30C W 14.0 2.161 N 30°E 17.0 1.627 N 30°W 15.0 2.236 N 6.5 1.000 N 30 °W 16.0 2.294 N 7.0 1.126 N 30 °W 17.0 2.339 N 8.0 1.321 N 30 °W 18.0 2.395 N 9.0 1.506 N 30 °W 19.0 2.441 N 10.0 1.641 N 30 °W 20.0 2.457 N 11.0 1.756 N 30 °W 21.0 2.500 N 12.0 1.888 Cell Boundary N 30°W to N 1.734 N 13.0 1.974 •• 1.762 N 14.0 2.041 •• 1.802 N 15.0 2.094 Cell Boundary N to N 30°E 1.755 N 16.0 2.138 •• 1.679 N 17.0 2.195 •• 1.620 N 18.0 2.230 N 19.0 2.271 Table 15
Fine Structure Activities (Loop H2O Cooled)
In 233 Pu R R U R Location Mn Lu Hn Pu ,,233 Th Th KMn Fission Fission Fission Pa-233
Inner Element Al 2.102 0.4885 0.5634 4.303 1.1533 0.202 120 0.5434 0.4876 0.8974 2.97 0.4659 0.633 A2 2.114 0.4846 0.5647 4.362 1.1653 0.203 130 0.5472 0 .4785 0.8744 3.10 0.4698 0.634 Average 2.108 0.4866 0.5641 4.332 1.1593 0.203 125 0.5453 0 .4830 0.8858 3.04 0 .4679 0.634 Intermediate Element Bl 2.363 0.7100 0.8500 3.328 1.1972 0.138 106 0.7595 0 .7216 0.9501 2.97 0 .6906 0.856 B2 2.363 0.7231 0.8561 3.268 1.1839 0.136 98 0.7743 0 .7214 0.9352 2.94 0.7057 0.865 Average 2.363 0.7166 0.8531 3.298 1.1905 0.137 102 0.7669 0 .7229 0.9426 2.96 0 .6982 0.861 I
Outer Element Cl 3.080 1.3789 1.6013 2.2337 1.1613 0.0731 70 1.4635 1.4146 0.9666 3.04 1.3637 1.530 Ln C2 3.094 1.4004 1.6316 2.2094 1J651 0.0714 71 1.4632 1.4522 0.9925 3.12 1.4086 1.572 Average 3.087 1.3897 1.6165 2.2213 1.1632 0.0723 71 1.4633 1.4334 0.9706 3.08 1.3862 1.551
Fuel Average 2.683 1.0148 1.1866 2.644 1.1693 0.0980 79 1.0782 1.0382 0.9629 3.03 1.0038 1.168
Calandrla Tube N 3.689 3.868 1.0485 0.0312* 32 S 3.685 3.874 1.0513 0.0289* 33
Reference Wheel 1 1.001 1.002 1.005 1.000 1.005 1.005 1.005 2 0.999 0.998 0.995 0.995 0.995 0.995 Average 1.000 1.000 1.000 1.000 1.000 1.000 1.000 1.000 1.000 1.000
Reference wheel cadmium-ratio • 203 +_ 10 Reference wheel r-value 3.06 x 10~4 Reference wheel temperature • 20.0°C
* From Table 9 Table 16 Fine Structure Activities (loop Air Cooled)
Location Lu R, U233 Pu RPu Th Th Fission Fission ,,233 Fission Pa-233
Inner Element Al 2.A821 0.7688 0.9207 3.229 1.198 0.132 104 0.8301 0.7301 0.8796 4.17 0.7641 0.899 A2 2.4721 0.7662 0.9154 3.226 1.195 0.132 103 0.8302 0.7212 0.8686 4.08 0.7602 0.893 Average 2.4771 0.7675 0.9181 3.227 1.196 0.132 104 0.8302 0.7257 0.8741 •4.13 0.7622 0.896
Internediate Element Bl 2.7125 0.9770 1.1649 2.776 1.192 0.105 91 1.0430 0.9481 0.9090 3.81 0.9692 1.115 B2 2.7013 0.9706 1.1494 2.783 1.184 0.106 88 1.0343 0.9271 0.8964 2.31 0.9560 1.101 Average 2.7069 0.9738 1.1572 2.780 1.188 0.105 89 1 .0387 0.9377 0.9027 3.06 0.9626 1.108
Outer Element Cl 3.3731 1.5282 1.7680 2.207 1.157 0.0716 69 1.5972 1.5525 0.9720 3.74 1.5284 1.709 C2 3.3430 1.4964 1.7262 2.234 1.154 0.0734 68 1.5628 1.5013 0.9606 3.74 1.5036 1.669 Average 3.3581 1.5123 1.7471 2.211 1.155 0.0725 69 1.5800 1.5270 0.9664 3.74 1.5160 1.685
Fuel Average 2.9942 1.2087 1.4123 2.477 1.168 0.0877 77 1.2746 1.1969 0.9390 1.2059 1.363
Calandria Tube N 2.6132 2.8639 1.096 0.0502* 47 S 2.6491 2.8977 1.094 0.0505* 46
Reference Wheel 1 0.996 1.007 1.001 1.003 1.000 1.001 1.001 2 1.004 0.993 0.999 0.997 1.000 0 .999 0.999 Average 1.000 1.000 1.000 1.000 1.000 1.000 1.000 1.000 1.000 1.000
Reference wheel cadmium-ratio 195 _+ 5 Reference wheel r-value 3.19 x 10"* Reference wheel temperature : 20.5°C
* From Table 10 Table 17
End Flux Peaking Copper Activities (Loop H20 Cooled)
Distance from Distance from Distance from Distance from Distance from Distance from end of fuel Al end of fuel A2 end of fuel Bl end of fuel B2 end of fuel Cl end of fuel C2 (mm) (mm) (ram) (mm) (mm) (mm)
Foils In Fuel Stack
0 3.095 0 3.101 0 3.999 0 4 .030 14.0 4 .905 14.0 4 .896 11.0 1.787 11.0 1.794 11.5 2 .533 12.5 2 .502 25.5 3 .536 27.0 3 .496 24.5 1.349 23.0 1.374 23.0 1.890 24.0 1.885 37.0 3 .213 38.0 3 .254 50.5 1.066 47.5 1.094 46.0 1.574 50.0 1.562 62.0 3 .081 61.5 3 .119 100.0 1.013 98.5 1.017 97.5 1.487 101.0 1.511 114.0 3 .038 110.0 3 .057 200.0 1.002 199.0 0 .998 198.0 1 .470 201.0 1.487 200.0 2 .915 198.5 2 .986 255.0 0.990 254.0 0 .998 252.0 1.468 254.0 1.500 255.0 2 .898 253.0 2 .994 Azimuthal Bands
1.3 2.698 2.721 • 3.617 3.659 11.5 4 .712 4 .726 51.3 1.065 1.064 1.519 1.536 51.3 3 .118 3 .085 221.3 1.006 0 .994 1.447 1.468 221.3 2 .939 2 .966 Table 18
End Flux Peaking Copper Activities (Loop Air Cooled)
Distance from Element Distance from Element Distance from Element Distance from Element Distance from Element Distance from Element end of fuel Al end of fuel A2 end of fuel Bl end of fuel B2 end of fuel Cl end of fuel C2 (mm) (mm) (mm) (ran) (mm) (mm)
Foils In fuel Stack
0.0 2.266 0.0 2.257 0.0 2.679 0.0 2.662 14.5 2.884 14.5 2.852 13.0 1.538 10.5 1.576 10.5 1.994 11.0 1.972 26.0 2.265 24.5 2.267 26.0 1.289 23.0 1.334 22.0 1.641 23.0 1.621 39.0 i.182 37.5 2.169 51.0 1.122 45.5 1.135 46.5 1.388 46.0 1.399 62.5 2.115 - 63.0 2.075 102.5 1.038 93.5 1.039 96.5 1.312 97.5 1.301 113.0 2.051 114.0 2.023 200.5 1.004 196.5 0.996 196,0 1.263 197.5 1.254 199.0 1.982 199.5 1.970 255.0 0.991 250.5 0.986 250.5 1.257 253.0 1.240 253.0 1.983 252.5 1.951 NJ 30
Azimuthal Bands
1.3 2.134 2.548 11.5 2.992 51.3 1.125 1.376 51.3 2.164 221.3 1.000 1.239 221.3 2.026
Axial Strips
1.3 2.107 2.572 1.3 3.243 6.3 1.771 2.258 6.3 3.136 11.3 1.590 2.047 11.3 2.946 16.3 1.454 1.832 16.3 2.638 230.5 1.001 1.284 21.3 2.401 235.5 0.999 1.282 26.3 2.281 230.5 1.933 233.0 1.892 _ 29 -
o ZEEP RODS THIMBLE SITES
Fig. 1: Plan View of the ZED-2 Lattice - 30 -
•CENTRAL SUPPORT TUBE
SPACER ^ 262.8 WASHER
213.2
ELEVATIONS (cm)
163.5
SPACER WASHERS \ 113.8
FUEL BUNDLE!
64.1
SPACER 15. WASHER
7 7777 7 f 7 / 7 7/7 0.0 ZED-2 CALANDRIA FLOOR
Fig. 2: Vertical Section of the Experimental Fuel String -3 1-
AIR PuO2-ThO2 FUEL ZIRCALOY-4 SHEATH DIAMETER 12.115 mm
I.D. 12.19 mm O.D. 13.03 mm
IS ALUMINUM 'PRESSURE' TUBE ALUMINUM CENTRAL 105.9 mm SUPPORT TUBE M4.3 mm
I.D. 13.5 mm O.D. 14.7 mm ALUMINUM CALANDRIA1 TUBE 1.0. 123.9 mm ZIRCALOY TIE RODS 0.0. 127.0 mm DIAM. 6.55 mm AIR ANNULUS
FUEL PIN GEOMETRY:
OUTER RING, 18 PINS ON 88.61 mm PCD MIDDLE RING, 12 PINS ON 57.51 mm PCD INNER RING , 6 PINS ON 29.77 mm PCD
Fig, 3: Horizontal Section of the Experimental Fuel - 32 -
1 1 • 1 1 1 1 1 ' I I i
X X X x x X X I 1.0 • • • • • •
X X
• •
o 5
x AIR COOLANT
< • H20 COOLANT CD is Q. 1.8 o < o
X
X
1 1 1 I 1 1 1 | 1 1 1 6543210123456 W E RADIAL POSITION IN UNITS OF PITCH (198.4 mm)
Fig. 4: Radial Distribution of Perturbation Factors
at Elevation 1.25 m - 33 -
— Cu and In-AI
— Lu-Mn-AI
- Pu-AI
- Th
U233-A«
Fig. 5; Location of Foils in Fuel Stack for Fine Structure Measurements ALUMINUM FRAME
(ZEEF^ (K2WL
CELL BOUNDARY |
Fig. 6: Location of Copper Wires on the Aluminum Frame ~1
N30°W o © © O • • N
2.0 O • X o * o N30°E x
O © FOIL ON ZEEP ROD
PRESSURE- LJ 0. TUBE CALANDRIA a. OI.0 TUBE
ZEEP ROD
0.0 _L 10 15 20 25 RADIAL POSITION (cm)
Fig. 7: Copper Activity Distribution in and Around the HpO-Cooled Loop N30°W o
• N
* x x 0 5 x N30°E
©
O tf FOIL ON ZEEP ROD or LU Q. PRESSURE Q. TUBE O O
CALANDRIA TUBE
• ZEEP ROD
B QO 10 15 20 25 RADIAL POSITION (cm)
Fig. 8: Copper Activity Distribution in and Around the Air-Cooled Loop - 37 -
1.46-
COOLED LOOP 1.45-
1.44-
1.43-
1.42-
COPPER ACTIVITY
1.04- AIR COOLED LOOP
1.03-
1.02-
1.01-
1.00. W S N
AZIMUTH
Fig. 9: Azimuthal Copper Activity Distribution on the Loop Calandria
Tntw Outer Surface - 38 -
CO s b"
NEUTRON ENERGY (eV)
Fig. 10: Comparison of the Cross Section of Lu17^ and Pu239 - 39 -
LONGITUDINAL STRIPS
AZIMUTHAL Cu BANDS INTER BUNDLE GAP (6 mm 777//
220 mm
228 mm
LOWEST 50 mm BAND OUTER \ 40 mm RINDI MrG. * 7777/ I2.'5mm| iir TZMHL
LOWEST BAND INNER RING o
KEY THICKNESS (mm)
GRAPHITE DISC 2.0 PLENUM (gas+Zr) 12.0 RESISTANCE WELDED END 3,,0 CAP (Zr) END PLATE (Zr) 3. 2 SPACER (AD 1. 6 TI6 WELDED END CAP (Zr) 12.7 GAP 2.5 (TYPICAL)
Fig. 11: Fuel Bundle Construction in the Region of the Bundle-End
Gaps and Location of External Flux Detectors - 40 -
a (VI a> a (VI (V) 55 CO CD a
(VI £ 3
IP S (VI
CO CO CO CO z z >—« K H oO a. a. _1 a o z z X o co (VI CO CO 2 ui 4J 5 IS/ i u.
UJ w o s * oc u. - co M UJ o *-*-* \ I CO 5
i o q o in q
AltAllOV «3ddOD 30-
2.8- • FOILS IN PINS Al Bl Cl x FOILS IN PINS A2 B2 C2 >- o AZIMUTHAL STRIPS A AXIAL STRIPS T £ 2.4-
£ 2.2- £L Q. O • A ° 2.0-
1.8-
1.6-
1.4- I
1.2- x •- 1.0- ~T —f- T" —r —i— 0 4 8 12 16 20 24 28
DISTANCE FROM END OF INNER FUEL STACKS (cm)
Fig. 13; End Flux Peaking for the Air-Cooled Fuel - 42 -
4.0
3.5-
•o LOCATION OF AXIAL STRIPS *2 > 3.0H \ u a. a. o 2.5- w B AVERAGE
X 0 2.0"
• C
1.5-
PLENUM
1.0-
2 3 4 23 24
DISTANCE FROM END OF PLENUM (cm) Fig. 1A: Azimuthal Flux Variation and End Flux Peaking as Indicated by Longitudinal Copper Strips on an Outer Element in an Air-Cooled Bundle 1.02
1.00
0.98 ZEEP ROD (K2W)
4
1.04-
1.02-
i.oo- A AK AN A *—' * THIMBL*VE KIW 0.98-
/
LOOP I-10- or CALANDRIA TUBE • 1.08- Io W-SIOE o 1.06-
«.04-
1.02-
1.00- \ 0.98. 20 60 100 140 180 220 260
AXIAL POSITION (cm) Fig. 15; Propagation of the End Flux Peaking Perturbation Into the Lattice; H^O-Cooled Loop - 44 -
1.02-
1.00-
0.98- ZEEP ROD (K2W)
1.06-
1.04- > 1.02- AC T 1.00- 'I ATHIMBLE KIW
COPPE R LOOP Ul 1.1 4- CALANDRIA cc TUBE
LJ I.I 2- W-SIDE 1H1 S —^ 1.10-
UJ 1.08-
1.06-
1.04-
1.02- 1.00- J \J .98 20 60 100 140 180 220 260 AXIAL POSITION (cm)
Fig. 16: Propagation of the End Flux Peaking Perturbation Into
the Lattice: Alr-Cooled Loop ISSN 0067 - 0367 ISSN 0067 - 0367
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