Edited by Amy F&on-Stout, Group CIC-1
Contents
1. 4 IN LIS a dde da 4 A 4 r N a iN CIS Gs PI An gl P TN e de 4 CES y NI e 4 8 4 e LIN 4 13 4 4 PN de 4 4 6 c I A e 4 4 4 e aw My on FONS X IN SN X IN Zh IN tr ee gt D support UJ pa PWR 15 MOX pins removed from Row 7 Appendix B UWCC Measurements of Fresh PWR MOX Fuel in Unborated Water Multiptica UWCC Measurements of PWR Fuel Nine fles Melo MOX fuel in unborated water TYP us Pereisa Nes PWR Full Array 264 pins 50 Rod leng mor 26 3677 680 64 sol 400 791 209 29 _ 025 PWR 17 MOX pins removed from Row G 0 14 PWR33 MOX pins removed from Row G Column 7 Ma zu 3218 sss 64 6 968 som 29 1081 1 PWR 215 Pins 33 pins removed from Row G Col 7 Mol 215 2995 534 s eof 34679 _ 281 imss __ 032 ns placed in row mol 24 344 636 5ss 249 mens 277 18725 055 204 148 _ 12876 150 163695 717 osa 158 485 _2. COINCIDENCE ELECTRONICS INCC MEASUREMENT PROGRAM analysis provides fuel assembly 78 5 PSR B mult Commercial shift register products meeting the requirements for UWCC neutron multiplicity coincidence measurements with the INCC program are the Advanced Multiplicity Shift Register from Ortec and the PSR and PSR B modules from Aquila Technologies The PSR B module is shown in Fig 5 The UWCC functions with older coincidence shift register electronics such as the JSR 11 and JSR 12 Measurements of the neutron singles S and doubles D are provided by these units A two parameter dies iplicity shift register flags Triples measurements are obtained from multiplicity measurements These also provide information indicating whether measurement conditions are appropriate to declared conditions The UWCC is operated using the Integrated Neutron Coincidence Counting INCC software program The program communicates with a shift register through the serial port of a PC computer The INCC program controls the shift register sets UWCC operational parameters and receives neutron singles doubles and multiplicity signals These signals are collected by the shift register The INCC program analyzes the UWCC measurement data and displays the results within a few seconds from the time each measurement is completed Count rates are corrected for detector dead time The neutron doubles D are corrected for multiplication usin
3. imo 8 mol panl m sa is 5 ES E 72 zr E 9 5 e e 65 S 87 LANL 163 5372216 72216 nas 85 58183 100 3 age 6 29347 4 nu MOX Boron e Width Measure Totals Rate Totals Rate Rods ppm us c s Gul sr a eel mot 267 cx 20 e e aa vo mos 15527 041 32 18 5 95 2250 21342 2 5 181 8 135 99 372 15 29 95 neal 109 8 8 a el 7 c al 4203 4 382 0 m aso seed smmsl cmd od 59386 aa al snd Mol 215 Appendix D UWCC Measurements of Fresh PWR MOX Fuel in Air Air Measurement Multip Muttip LANL amp Mol Fuel Array of Rate Gorrect corrected PWR MOX fuel Rate c s Error c s PWR Full Array 264 MOX pins 50 Rod length Mol 264 36 77 680 64 600 18064 57 3435 _ 91 82 68 1802 13 PWR 17 MOX pins removed from Row G Mol 247 3441 636 64 5580 16441 3097 27 7 6 19 1644104 PWR 33 MOX pins removed from Row Col 7 Mol 231 3218 595 64 4620 15242 12 2852 27 100 19 1327 04 PWR 204 pin ful array _ rANL 204 6723 1483 64 1050 6107 74 7820 220 8 375 4937 41 PWR 15 MOX pins removed from Row LANL 189 6229
4. 204 10883 128791 150 30634 1257 oss 139 e229 1378 6 3360 iosas 75 156413 3so 28807 04 ws ls1se ea 117868 140 144349 ame 1056 _ 4093 ose 163 66 135 133303 s amp o ana __ Increase Mol Measurements based 240Pustt Mutip M CN f M l Fuel Linear Gate Totals Rate Doublea Triples Rate Triples Rate Corrected on ratio of Mo Type X Density Width e s Rate Error Error Doubles Rate Doubles Rate PWR 204 pin full PWR 204 full array PWR 29 MOX pins removed from Row 7 G PWR 41 MOX pins removed from rows 7 amp 10 Col g om 130cm 50cm Fuel length gom 4 p Error os PWR Full Array 264 MOX pins 130cmRodlength Mol 264 3677 680 64 90 4869 79 s1992 209 2131800 oso 22221 __ PWR 17 pins removed from Row 130 Redleng Mol 247 3441 636 64 asol 46745 39 seega _ 101 20535 28900 PWR 33 pins removed from Row G Col7 130cmRd Mol 231 3218 595 64 60 4433 96 73727 239 1824 261 20828 __ 034 PWR 215 MOX Pins 33 pins removed from Row Col Mol 215 2995 554 64 600 42166 6686 226 170358 241 19889 032 PWR204 pin full array _ LANL 204 6723
5. Cn 00000 CIN An EN 0 IN 4 4 PIN IXY cS de gt Ji T e I sh de eg 0 dr 4 de BRAD LN de Au sh CIS LI JJ Ar An 4 EIN ee 4 ES du ah CES de de PIS CL T AM a CIS 4 2 CES AN de de AN CI TII P eS eT A GN LIE A mut a at at mat S QPONMLK JIH GF 4 de L3 LIN 4 a AN 4 r y 4 ei a PI D 4 de 4 PIS r 4 a e 3 EI CIN D de Si 3 gt 4 E IS da D e 4 4 4 4 A 4 4 aL 4 PI C CIS NY CIN 4 4 L3 y 4 CES PEN 4 e a d AD Pis 9 9 a d b IE En ai A IN y d NJ d de x dl de a 4 4 N 4 4 PE r AS r d ALS 4 PN ET P Bi d 4 5 4 4 de y 4 4 A e dl e AN 4 4 EIN 4 PIN
6. The doubles gate ratios D D confirm the boron concentrations as shown in Fig 14 The doubles gate ratio is expected to be approximately 0 79 for a boron concentration of 2200 ppm Double Gate Ratio 64 128 usec jg 0 77 a AN EN 0 75 0 73 lt 2 c E 264 irod MOSS WA 0 71 o 0 500 1000 1500 2000 2500 Boron Concentration ppm Fig 14 Doubles gate ratio D D vs boron concentration Figure 15 shows the UWCC positioned around the PVR MOX fuel array in Mol Belgium The active length of the plutonium in the Mol fuel rods is 50 cm The isotopics for the fuel are given in Table VIT 16 Jan 1998 233Pu 239Pu 249 pu Pu 24 24Pu Pu 0 054 81 218 17 582 0 689 0 456 2 432 0 02575 g cm pin MOX Array 15x 15 204 pins 6 798 g cm array Fig 15 Mol PWR MOX fuel array positioned underwater in the UWCC Two rows of fuel pins are removed from the array 14 LANL FUEL DESCRIPTION CALIBRATION MOX PIN REMOVAL The Los Alamos PWR MOX fuel assembly is a 15 pin X 15 pin array shown in Fig 16 Refer also to Appendix A The isotopic specifications for the MOX rods are listed in Table VIII below For the full 204 rod array 204 fuel rods and 21 empty control rod channels the linear plutonium loading is 14 83 g Pu cm The UWCC is 17 3 cm tall and it is sensitive to the fuel for about 10 cm
7. calibration curves are sufficient for the UWCC to Measured Singles Cd Count Rate cps i Measured Multiplication cover unborated Corrected Doubles Cd and borated 0 500 1000 4500 2000 ponds Boron Concentration ppm Figure 13 is a plot Figure 13 MCNP simulation of UWCC measurements on a 17 X 17 of the correlation MOX PWR fuel assembly with and without a cadmium between the boron cover concentration and the doubles coincidence ratio 64 L1s 128 Us gates mea sured by the UWCC on a 17 X 17 PWR fuel assembly For MOX fuel assemblies stored underwater the boron content can be con CONCENTRATION firmed from a dieaway time t ratio measurement when a fuel assembly is MEASUREMENT located in the UWCC The boron concentration in parts per million is deter mined with the UWCC by measuring a fuel assembly at two shift register gate settings This is possible since the boron concentration affects the die away time and not the efficiency of the UWCC shift register gate settings are changed in the INCC program in the Measurement Parameters located under the Settings file menu The normal doubles rate measurement D takes place with a 64 us gate setting If a second doubles rate measurement D x of approximately 5 minutes is made with a second shift register gate setting of 128 us then the boron concentration can be determined 13 MOL FUEL DESCRIPTION Table Vil Mol MOX Fuel Isotopics
8. recommendation or favoring by The Regents of the University of California 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 Regents of the University of California the United States Government or any agency thereof The Los Alamos National Laboratory strongly supports academic freedom and a researcher s right to publish therefore the Laboratory as an institution does not endorse the viewpoint of a publication or guarantee its technical correctness LA 13574 M Manual ISPO 375 UC 706 Issued May 1999 USER S MANUAL The Underwater Coincidence Counter for Plutonium Measurements in Mixed Oxide Fuel Assemblies G W Eccleston H O Menlove M Abhold M Baker J Pecos International Atomic Energy Agency Wagramerstrasse Vienna A 1200 AUSTRIA Los Alamos NATIONAL LABORATORY Los Alamos New Mexico 87545 TABLE OF CONTENTS ABSTRAC di 1 INTRODUCTION iecit RARE i ER iub uoce teneas t ente tat 2 MVS DESIGN nin 3 PREAMPEIEIER PD E210 cias 4 COINCIDENCE ELECTRONIC 5 5 INCC MEASUREMENT PROGRAM ccsccsssssssssssessessecssesesscssessssseserssesssssssassusaucnesaueassaesaeenseasenecneesess 5 HIGEFVOLTAGE PLATEAU ctia de Mb S tut deem edu 6 DEAD TIME GS eden idm
9. us 32 Singles cps 17898 Doubles cps Dor 076 T us Boron in the pool affects the multiplication of the MOX fuel assembly which in turn affects the dieaway time of the system Measurements at two dieaway time gate settings can confirm the boron content in a pool Figure 8 shows the doubles rate versus the gate width for a 22 source in air bottom curve and a PWR assembly in unborated water top curve Singles cps Doubles cps D 5 T us Singles cps Doubles cps Derr 0 us In addition to the measurements for a Cf source in air the dieaway time was measured for a PWR MOX fuel assembly in pure water at Los Alamos This information is provided in Table IV The dieaway time increases from approximately 38 us for Cf in air to approximately 78 us for a MOX assem bly in pure water The reason for the increase is the long neutron multiplica Table IV UWCC Dieaway Time Measurements for a PWR MOX Assembly in Water Singles cps 100490 Doubles cps 5995 D 6 1 264 1 uS 100540 10137 1 144 86 Singles cps Doubles cps D 076 t us Singles cps Doubles cps Derr 696 T us tion fission chains that occur when a MOX fuel assembly is placed underwa ter The induced fissions from multiplication add several neutron thermaliza tion time intervals to the dieaway time Figure 8 shows a graph of the normalized double
10. 1374 64 1050 550 94 665 0 214 153 304 45101742 PWR 29 MOX pins r moved from Row 7 Col G 1272 50602 60 6007 18 253 189 41551 356 5372 11 85 NOTE Rod count on the measurements in rows 11 and 12 was off There are 41 rods out with row 7 10 and col pulled MOX rod in one position in col G PWR 42 MOX Pins removed Rows 7 and 10 Col G LANL Appendix E UWCC Cross calibration Data Note Cross calibrations in air should be performed with the UWCC unit sitting on a cart and away from surfaces that would bias the cross calibration measurements caused by neutron reflections UWCC measurements 1500 ppm boron on the LANL PWR 204 MOX Fuel Array eg Dead PWR fuel Boron idi FEE awe ue ae e Dum 49 cam ET Lace Peti Ta Tertia a Ta ae a ETT NITET MET Tal sel nal The UWCC received an ud preamp PDT210 A RUPEE to the cr model to increase es and allow the high voltage HY to be lowered from 1740 volts to the standard 1680 volts used for coincidence counting measurements UWCC 1 that was delivered to the IAEA corresponds to the cross reference data for Cf 8 in air 240Pueff Linear Density g cm UWCC measure wood benchtop b usi 252 Cf source number 8 Exc quls EA O E Cross calibrations are biased if performed on different benchtops or benchtop
11. 1883 66 9o 125791 150 162750 715 _ 30634 1257 48920 0 85 PWR 15 MOX pins removed from Row 7 LANL 189 9 1374 64 336 119546 15 sool 628 PWR 29 MOX pins removed from Row 7 Col G 175 sol 112868 1401 144349 c30 1564 _ 44093 PWR 41 pins removed from rows 7 amp 10 ColG LANL 163 s372 e 9 1351 133303 s amp o 2007 osal Appendix C UWCC Measurements of Fresh PWR MOX Fuel in Borated Water fuel at 1500 and 2200 ppm Boron Concentrations MCNP REN Calculations and Extrapolations Borated water PWR MOX fuel Mol Array 264 pins 130 Rod Length Extend to 130cm 17 MOX pins removed from Row Extend to 130cm 33 MOX pins removed Row G Col 7 Extend to 130cm 48 MOX p UWCC Measurements of PWR MOX m Boron 17 MOX pins removed from Row 29 s3 zo a m Boron 33 MOX pins removed Row G Col m 4 MOX pins removed Row G Col ins removed Row G Col 7 11 Measurement to 2200 Boron n b ron 15 MOX pins removed Ro 2 nt boron 29 pins removed Row 7 eal m boron 41 pins removed Row 7 C piste m Measure Totals Rate Totals Rate ppm Time sec c s le du mI 1820 00 134 239 8 146 50 Mol 231 32 18 2250 amp a 21185 1557 0 181 8 137 03 Mel 215 29 95 oss ms e 19351 13293 139 9 128 30 LANL
12. 2227 15 the parts per million boron content in the water 0000 pure water 0500 500 ppm 1000 1500 2000 2500 Using this convention the measurement id name P1826F148B2200 would represent a PWR MOX fuel assembly with serial number 1826 containing 14 8 g cm of Pu stored in a pond containing 2200 ppm boron This report has been reproduced directly from the best available copy Itis available to DOE and DOE contractors from the Office of Scientific and Technical Information P O Box 62 Oak Ridge TN 37831 Prices are available from 615 576 8401 Itis available to the public from the National Technical Information Service US Department of Commerce 5285 Port Royal Rd Springfield VA 22161 Los Alamos NATIONAL LABORATORY Los Alamos New Mexico 87545
13. The contents in the electronic shipping container include e the JSR 12 electronics shift register connection cable between the JSR 12 and computer e computer containing the INCC software program and e power supply and cables for the computer and printers if used UWCC ASSEMBLY 1 Open the box containing the detector pipe sections and lay out the AND CHECKOUT necessary lengths of pipe to reach the fuel assemblies PROCEDURES 2 Open the fiberglass case that contains the UWCC detector head box and remove the UWCC measurement head OR sum coupling box signal cables and fork protective fabric sleeves 3 Carefully set the UWCC on a foam pad or piece of plastic Note that the welds on the thin stainless steel SS cladding of the UWCC could crack if the UWCC is not handled carefully If these welds are damaged and or cracked the UWCC could leak and the unit would be inoperable 4 Check the UWCC configuration to ensure that the fork positions and the nylon bumper are set in the correct positions for the type of fresh MOX fuel PWR or BWR to be verified 5 Pull the 20m signal cable bundle through the SS pipe segments and then clamp the pipe segments together to form a 6 to 7m long tube that has the cable bundle threaded inside the tube 6 Pull about 1m of extra signal cable out of the pipe end and attach the cable connectors to the identified locations at the top of the UWCC signal A signal B 5 and the HV Attach t
14. Us and the deadtime parameters a b 1 The measurement parameters required for the INCC program under the Setup heading are listed in Table II Table Il UWCC Measurement Parameters Setup 64 64 64 Gate Length High Voltage 1680 1680 1680 Dieaway Time air 38 38 38 Efficiency Multiplicity Dead Time Deadtime Coefficient Deadtime Coefficient Deadtime Coefficient Doubles Gate Fraction Triples Gate Fraction MULTIPLICITY DEAD TIME NEUTRON DIEAWAY TIME For multiplicity analysis the deadtime corrections are done with the equations derived by Dytlewski using a constant deadtime value d The value of d was determined by measuring several Cf sources with different neutron source strengths The triples doubles multiplicity ratio should be independent of the neutron source strength after deadtime correction The value of d that gave the best agreement was the maximum value d z 500 ns A multiplicity dead time of 500 ns requires a shift register gate setting of 64 Hs or larger The additional multiplicity deadtime coefficient C was required for units UWCC1 and UWCC2 The neutron dieaway time of the UWCC was measured using source Cf 7 Table III lists the gate widths and the doubles rates and errors The resulting dieaway time in air is approximately 37 us for a gate setting of 64 us Table Californium Cf7 UWCC Dieaway Time Measurements in Air Gate Length Parameter
15. a 6 MULDTIPEICIEY DEAD TIME dla 7 NEUTRON DIEAWAY TIME ss cbe tuto ote Y mem 9 MULTIPLICATION CONS TANT RH 10 CROSS CALIBRATION itte m s TE eM EA 11 BORON EF REGUS uiid eonim cr Ea LR E LC 12 BORON EFFECTS ON UWCC MEASUREMENTS 13 BORON CONCENTRATION MEASUREMENT ccccccscsssescsesssssscscsssssssssssscssusesscstsnsecneeesensesesens 13 MOE FUEL DESCRIPTION das 14 LANL FUEL DESCRIP TION aa ia 15 GALIBRA TION E TRIN 15 MOX PIN TEMOVAL ni aan 15 UWCC AIR MEASUREMENTS sese tntnte rtt 18 CALIBRATION RESULTS iet rt 18 SUMMARY aac 19 ACKNOWLEDGMENT S eate te 19 REFERENCES osea dai 19 APPENDICES APWR Fuel Array MOGKUD oue eae LUE 1 B UWCC Measurements of Fresh PWR MOX Fuel in Unborated Water B 1 C UWCC Measurements of Fresh PWR MOX Fuel in Borated C 1 D UWCC Measurements of Fresh PWR MOX Fuel in Air sees D 1 E UWCC Cross Calibratiori Data voti oett io E 1 E WCC User POCONOS m F 1 G INCC Setup and Operation
16. The same p must be used for calibration and subsequent assay and its absolute value is important only where the multipli cation M must be correctly determined 6000 LANL MOX 294 Fuel Pins Multiplication Corrected Doubles 0 37 24 4 Doubles 000 4000 va 264 pins 9247 pins Mol MOX 9231 pins 215 elite Fuel 0 2 4 6 8 10 12 14 16 240Pu g cm 3000 Doubles and Corrected Doubles cps Fig 19 Neutron doubles D and multiplication corrected neutron doubles D for PWR MOX fuel arrays in Mol Belgium and Los Alamos 2200 ppm borated water Multiplication Corrected Doubles cps 0 2 4 6 8 10 12 14 16 18 20 22 24 26 240Pueff g cm Fig 20 Multiplication corrected neutron doubles calibration for a PWR MOX fuel array in Mol Belgium Los Alamos and inspection field measurements in 2200 ppm borated water 17 UWCC AIR UWCC can measure MOX fuel in air to verify the Pu content in a MEASUREMENTS manner similar to the passive neutron coincidence collar We calibrated the CALIBRATION RESULTS UWCC in air using the Mol and Los Alamos MOX fuel assemblies The Mol fuel pins are 50 cm in active length and show an end effect compared to the 177 8 cm active length fuel rods at Los Alamos The neutron doubles and D from air measurements are shown in Fig 21 The precision is better than 1 in 10 min The line has a negative intercept because
17. along the length of the UWCC CIPIT RN En 10 UWCC cross calibration geometry and 7 Cf source holding fixture 11 The UWCC gate fraction vs dieaway time for gates of 64 and 128 ys 12 MCNP simulation of UWCC measurements on a 17 x 17 MOX PWR fuel assembly with and without a cadmium 22 4000 13 Doubles gate ratio Ds4 D 28 vs boron 14 Mol PWR MOX fuel array positioned underwater in the UWCC Two rows of fuel pins are removed from the array essere UT 14 UWCC calibration geometry with the Los Alamos 15 pin x 15 pin MOX fuel assembly aiite cone acts oS 15 Figure 17 Figure 18 Figure 19 Figure 20 Figure 21 Multiplication corrected neutron doubles Dmc for PWR MOX fuel arrays in Mol Belgium and Los Alamos in unborated 16 Neutron triples and doubles 10 versus PPu for PWR MOX fuel in 2200 ppm els i o Wai MEE 16 Neutron doubles D and multiplication corrected neutron doubles for PWR MOX fuel arrays in Mol Belgium and Los Alamos in 2200 ppm borated water 17 Multiplication corrected neutron doubles calibration for a PWR MOX fuel array in Mol Belgium Los Alamos and inspection field measurement
18. beyond the top and bottom of the detector arms The mea sured fuel region extends over a height of about 37 cm In the case of the Los Alamos MOX fuel assembly this corresponds to approximately 2 5 kg of plutonium Table Los Alamos MOX Fuel Isotopics 15 Jan 1998 Pu 0 673 Pu 77 580 Pu 17 799 Pu 2 367 MPu 1 581 4 734 Pu r 0 0727 g cm pin MOX Array 15 X 15 204 pins Pu 14 83 g cm array Fig 16 UWCC calibration geometry with the Los Alamos 15 pin X 15 pin MOX fuel assembly Calibration of the UWCC was obtained from measurements of MOX fuel rods located at the SCK CEN facility in Mol Belgium and at Los Alamos These measurements provide calibration data for two different types of MOX fuel rods and fuel arrays The calibrations at Mol were performed in pure water and for five boron concentrations 530 909 1540 2160 and 2250 ppm Both PWR 17 pin X 17 pin array and BWR 9 pin X 9 pin array fuel arrays were used for the measurements at the VENUS facility Borated and unborated calibrations were performed at Los Alamos The Los Alamos PWR MOX fuel array is a 15 X15 configuration and the fuel contains more than twice the plutonium 14 83g Pu cm compared to the Mol fuel array 6 80g Pu cm The effects of plutonium loss through pin removal load were determined starting with full MOX arrays The full MOX fuel arrays in Mol Belgium 17 X 17 264 pins and in Los Alamos
19. care is not taken in developing a unique and clear naming convention for the measurement ids One example occurs in reanalysis of measurement data For example take the case of measurement id PWRMOX1 that was collected on date 98 07 22 and time 15 45 40 and was then later reanalyzed twice using different deadtimes that were changed using the measurement parameters file for each reanalysis In this example there would now be three files called PWRMOXH in the database and under the INCC program Reanalyze option what would be seen is listing of three files each with the same name tand the only difference would be in the times which would be 15 45 40 15 45 41 15 45 42 Tn this case it is difficult to tell which deadtime was used with which file and what their differ ences are We therefore recommend that a naming convention be established prior to verification measurements to establish unique measurement id names thatwill allow the measurement data from past inspections to be easily identified and located for post analysis print out plotting etc G 3 Listed below is a possible naming convention SxxxFyyyBzzzz where S indicates the fuel serial number follows where xxxx is the fuel serial number F indicates the type of MOX fuel where F is replaced by P for PWR and by B for BWR yyy is the declared 240Pueff loading in grams per cm For example a loading of 14 8 g cm of 240Pueff would be F148 B is the boron loading in the fuel pond
20. pin substitu tion Additionally the measurement uncertainties required for two parameter analyses can be obtained within about one order of magnitude reduction of counting time compared to the time needed to measure the triples 18 SUMMARY ACKNOWLEDGMENTS REFERENCES The UWCC can be used to measure the per unit length in PWR and BWR MOX fuel assemblies stored under water or in air Verifica tions are based on calibration curves of D versus Pu unit length This correction produces a straight line calibration curve and has been determined from measurements on two different MOX fuel arrays The statistical precision for D is better than 1 for a two minute count The UWCC can detect the removal of approximately 1 of the plutonium for a relative measurement and 2 346 of the plutonium for an absolute mea surement depending on how closely the unknown matches the calibration assembly The D calibration makes the measurements relatively insensitive to differences between the calibration condition and the field condition The calibration is insensitive to the number of fuel rods diameter pitch cladding and LEU content Separate calibrations are required for pure water and borated water If separate p values corresponding to pure and borated water measurements are used then the calibrations will overlap To limit the potential for error in measurements and reduce the chance of an inconsistent p value the sam
21. prior to field measurements If the INCC program has not been configured and set up refer to Appendix F for detailed proce dures on setting INCC measurement parameters etc 16 Turn on the computer and the JSR 12 and review the INCC measurement parameter settings under the Setup Measurement Parameters option Check that the correct shift register type is selected JSR 12 or other shift register if used BACKGROUND MEASUREMENT FRESH MOX FUEL VERIFICATION 17 Using the Acquire Rates Only option collect 3 measurements of 10 seconds each to check the operation of the UWCC Following the measure select the Reports Rates Only option and review the output file to check that the predelay gate length high voltage dieaway time and deadtimes are all correctly set Review the singles doubles and triples counts to check that the UWCC is correctly counting 18 Check and select the correct facility type MBA and detector ID i e UWCCI under the Setup Facility Inspection option 19 Select or input the isotopics information under the Setup Isotopics option for the MOX fuel assemblies to be verified 20 Set the calibration analysis method for the verification Under the View option select Maintain Under the Maintain Calibration option select Analysis methods then select the Material type and Calibration curve for the passive analysis method 21 Check the passive calibration curve parameters and curve
22. resulting changes e in the fg values NE change the effective NE S m Po by approximately Borated wator el 37 Unborated water 40 60 80 100 Die Away Time usec Gate 128 usec Load Gate Fraction Fig 12 The UWCC gate fraction vs dieaway time for gates of 64 and 128 us 12 BORON EFFECTS Spent fuel storage ponds have boron contents that range from zero to several ON UWCC thousand ppm with most ponds containing approximately 2200 ppm Increas MEASUREMENTS ing the boron concentration in a spent fuel pond increases the neutron absorp BORON tion rate reducing the number of neutrons emitted from a MOX fuel assem bly that reach the UWCC and resulting in a lower counting rate This rate change causes a calibration change that is a function of the boron concentra tion Surrounding the UWCC with a cadmium layer removes thermal neu trons that are similar to boron as they enter the UWCC reducing the effect of varying boron concentrations Figure 13 shows the UWCC neutron singles rate as a function of boron concentration from a 17 pin X 17 pin MOX PWR fuel assembly The MCNP results are plotted for the UWCC with and without cadmium Cadmium covering the UWCC flattens the efficiency response compared to no cadmium and it reduces the efficiency changes due to chang ing boron concen tration The AS UWCC measured D in Fig 13 is relatively flat between 1000 and 2250 ppm boron indicating that two
23. rod removal de creases both the plutonium source term and the efficiency from neutron back scattering from the ends of the fuel rods The triples rate air is low 8 7 so the T measurement would require very long counting times so is generally not useful Doubles and Corrected Doubles cps 0 2 4 6 8 10 12 14 16 240 g cm Figure 21 Neutron doubles and multiplication corrected doubles calibration for PWR MOX fuel in air The UWCC measures full arrays of MOX rods and is able to verify if MOX rods have been removed Calibration results for full arrays of MOX rods in 2200 ppb boron go through origin and have a linear line of D 24 1 x In most of the calibration configurations where pins were removed water replaced the space from a rod removal However for two of the configura tions low enriched uranium rods 3 3 5U were substituted for the MOX rods The effects of these pin changes are detected by UWCC measurements The plutonium verification measurements are normally based on the D calibration and the counting precision for D is better than 1 in 1 to 2 minutes Two parameter analysis using the known alpha correction technique removes multiplication effects from the doubles measurements For cases where LEU fuel pins are substituted for MOX fuel pins the known alpha correction removes the multiplication effect created by the LEU pins and permits verification of assemblies even in the presence of LEU
24. 15 X 15 204 pins were measured Pins were then removed from selected interior rows to reduce the plutonium content Measurements were made for the case where water replaced the MOX rods One set of measurements were collected with UO fuel rods containing a depleted uranium content of 0 2 replacing the MOX rods The neutron singles and neutron doubles rates are dependent on the specific 15 configurations The multiplication correction removes this dependence The multiplication corrected neutron doubles rate versus the Pu effective con tent is a straight line Figure 17 shows the the D rate versus the Pu effective linear loadings unborated water The same p 0 19 was used for the fresh water and calibration mea Mol MOX Mol MOX 600 500 400 surements This value of p is required for verifi cation measure ments when using the calibration curve in Fig 17 300 200 100 Multiplication Corrected Doubles D__ cps The limited length zie of the Mol MOX Ae STR fuel 50 cm shows Fig 17 Multiplication corrected neutron doubles D for an end effect that PWR MOX fuel arrays in Mol Belgium and Los has been corrected lamos unborated water using MNCP calculations that extend the fuel to a length of 130 cm The end effect is negligible for the borated water case Figure 18 compares the triples with doubles for the Los Alamos MOX fuel array which was measured in
25. 1500 ppm boron and extrapolated to 2200 ppm boron The triples precision is 2 4 in 10 minutes Counting periods of about 10 minutes might be required to make quantitative use of the triples count The triples rate as a function of the Pu effective mass is shown in Fig 18 The ratio of T D and T S could be used to resolve anomalous results or differences between the calibration condition and the field condition The ratio of T D 700 approximately equaltoeand T gt S 500 MT equal to isa i Q 400 oo a size and S 2 the fuel assem p 100 E bly that could be A E these ratios g cm Fig 18 Neutron triples and doubles 10 versus y Sor PWR MOX fuel in 2200 ppm borated water 16 Plutonium calibration measurements are based on results shown in Fig 17 for pure water and Figs 19 and 20 for borated water The LANL MOX fuel array was measured in 500 1000 and 1500 ppm boron and the data were extrapolated to the 2200 ppm boron values shown in Fig 19 Figure 20 contains measurement data for field inspection trials of PWR MOX fuels which have much larger loadings plutonium compared to the Mol and LANL MOX calibration pins The calibration data in Fig 20 provide a straight calibration line through the origin 24 1 x which is dependent on the multiplication constant p We estimated the p listed in Table V for PWR assemblies to be 0 19
26. LA 13574 M ISPO 375 Manual The Underwater Coincidence Counter for Plutonium Measurements in Mixed Oxide Fuel Assemblies Manual UNITED STATES PROGRAM FOR TECHNICAL ASSISTANCE TO IAEA SAFEGUARDS DEPARTMENT OF STATE DEPARTMENT OF ENERGY ARMS CONTROL AND DISARMAMENT AGENCY NUCLEAR REGULATORY COMMISSION NATIONAL LABORATORY Los Alamos National Laboratory is operated by the University of California for the United States Department of Energy under contract W 7405 ENG 36 Edited by Amy Fulton Stout Group CIC 1 This work was supported by the U S Department of Energy Office of Nonproliferation and National Security International Safeguards Division and Program for Technical Assistance to IAEA Safeguards An Affirmative Action Equal Opportunity Employer This report was prepared as an account of work sponsored by an agency of the United States Government Neither The Regents of the University of California the United States Government nor any agency thereof noranyof their employees makes any warranty express or implied orassumesany 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
27. ON TENT CONFIR MATION MEASUREMENT DECONTAMI NATION AND REPACKING 25 Keep the MOX fuel assembly in position in the UWCC The boron concentration in the pool can now be easily confirmed with a second measurement using a gate width of 128 us on the MOX assembly that was measured in step 23 Select the Setup Measurement Parameters option and check that the Gate length microseconds was set at 64 for the measurement in step 23 Change the gate length to 128 and repeat the mea surement performed in step 10 26 Determine the doubles gate ratio D D by taking the ratio of doubles counts for the 64 us gate measurement D to the doubles count for the 128 15 gate measurement D Using this ratio and referring to Fig 14 confirm the boron concentration in ppm in the pool and check it against the operator information 27 Select the Setup Measurement Parameters option reset the gate length microseconds back to 64 and then continue MOX fuel confirmation measurements 28 Once all verification measurements are complete the UWCC can be decontaminated by the operator if necessary and removed from the pond and disassembled and packed for shipment The decontamination of the equip ment would follow the operator s normal procedures however the fabric covers for the arms are to be discarded after use Appendix INCC Setup and Operational Steps for UWCC Measurements Load the INCC Program 1 Click on Start in lo
28. WR Fuel Array Mockup UWCC Measurements of Fresh PWR MOX Fuel in Unborated Water UWCC Measurements of Fresh PWR MOX Fuel in Borated Water UWCC Measurements of Fresh PWR MOX Fuel in Air UWCC Cross Calibration Data UWCC User Procedures INCC Setup and Operational Steps for UWCC Measurements 20 Appendix A PWR Fuel Array Mockup Los Alamos 15 X 15 PWR Fuel Array y sos de de SOS e 22 P Vid D de Y 4 IN A No E Ld ad bh LA 4 CIN dr 4 d y 4 de p J 4 B LA s PIN 7 A 22 UWCC Positioning Bumper e Gis 4 M 4 4 ea see AN 4 4 sscecece de AS YA 909000 15 ZN 4 qai I LIN 69 DD amp AS de PIN de NY x Sw 45 AX ONMLKJIHGFEDCBA dr 4 Ge iN 4 dh CES 0 E d CES PIN 4 e de 4 y ee 4 4 Y 4 VD da M 4 mew gt SUPPORT Appendix A PWR Fuel Array Mockup em pd dl A E UO O m Nw BN HA YV CI IJ TI ye Y Y e de As de eA GE A CICI T T ae CIN 2 CIN 060000 En de AN de 000 D de d CES
29. al Steps for UWCC Measurements G 1 Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 Figure 11 Figure 12 Figure 13 Figure 14 Figure 15 Figure 16 LIST OF FIGURES UWCC positioned around the Los Alamos PWR MOX fuel assembly to provide plutonium verification measurements underwater eee 2 Underwater Coincidence Counter UWGCO sess 3 UWCC forks showing polyethylene and the cabling to the neutron detectors 4 Wiring from He tubes to the PDT 210A Amplifier 4 PSR B multiplicity shift register connected to the UWCC signal summer box 5 Calibration curve for PWR MOX fuel verifications in borated water using INCC corrected doubles measurement 0 0825 5 UWCC detector high voltage bias plateau 6 Doubles rate versus the coincidence gate width for the UWCC in air with a 220 source and in water from PWR MOX fuel assembly 8 Relative statistical error for the doubles rate versus gate setting for 2526f in air and for a PWR MOX fuel assembly in water eese eene tnnt 9 UWCC neutron singles doubles and multiplication corrected doubles response vs position cm of the PWR MOX fuel assembly
30. ce shift register electronics and assay software and e compatible size and weight for transportation field setup and use The selected design for the UWCC shown in Fig 2 consists of eight 7 5 atmosphere He neutron detectors embedded in polyethylene with 2 5 cm of polyethylene in front and 3 8 cm behind the detectors Four detectors are located in each of the UWCC forks The polyethylene is wrapped in cadmium and located in a watertight stain less steel enclo sure stainless steel bellows allows signal cables to be connected be tween the detec Fig 2 Underwater Coincidence Counter UWCC tors and the UWCC pipe and preamplifier A stainless steel backplate contains a pipe holding the PDT 210A dual AMPTEK preamplifier Stainless steel is used on all external components for decontamination In addition to providing improved decontamination the stainless shell also protects the cadmium liner which is positioned around the high density polyethylene on the inside of the shell The stainless shell is watertight and sealed with standard stainless steel screws and O rings permitting measure ments to be performed underwater To decrease the UWCC sensi tivity to varying boron concen trations in the water we placed a 0 5 mm liner of cadmium inside the stainless steel forks which completely surrounds the polyethylene containing the detectors For gamma ray shielding and neutron absorp tion
31. e in the center of the active zone measured efficiency in air was 3 6 PWR mode for a Cf point source centered in the UWCC For the BWR geometry the efficiency for a Cf source in air increases because the two forks are moved closer together compared to the PWR configuration resulting in an efficiency of 5 1 Because of the extended geometry and the neutron absorption in the water the average efficiency for spontaneous fission neutrons emitted over the geometry of a fuel assembly will be considerably less than this value The He tubes in the UWCC have active lengths of 280 mm compared with 152 mm for the modified fork The extra length was designed to provide more efficiency and to make the counting rate less sensitive to the movement of the fuel assembly relative to the fork during the measurement The primary drawback to these larger fork arms is the increased weight for the UWCC The nylon bumper on the back of the UWCC is used to position fuel assem blies in the center of the maximum counting profile The bumper has two positions which are determined by a set screw The bumper is extended for BWR assemblies and retracted for PWR assemblies 9 Tests were performed to determine the change in counting rate as a function of moving the fuel assembly away from the bumper and out of the measurement area of the forks see Fig 10 A 2 cm gap between the fuel and the bumper results in an approximately 1 change in the D rate Both
32. e value Table V is recommended for all measurements The appropriate calibration curve borated versus unborated is selected based on the operator s boron declaration The boron loading can be verified by calculating the doubles ratio see Fig 14 from a measurement on a fuel assembly with two gate settings of 64 to 128 us The work reported in this manual was supported by the United States De partment of Energy International Safeguards Division DOE NN 44 and the United States Program of Technical Assistance POTAS to the Interna tional Atomic Energy Agency IAEA 1 Precision Data Technology Corporation Everett Washington 2 D Reilly et al Passive Nondestructive Assay of Nuclear Materials ISBN 0 16 0332724 5 March 1991 3 N Ensslin A Simple Self Multiplication Correction for In Plant Use in Proc 7th ESARDA Annual Symposium on Safeguards and Nuclear Material Management Liege Belgium 1985 L Stanchi Ed Vol 19 pp 222 238 4 N Dytlewski Dead time Corrections for Multiplicity Counters Nucl Instrum Methods A305 pp 492 494 1991 5 R Charcon et al Measurement of Fresh MOX LWR Type Fuel Assemblies Underwater SCK CEN Blg 766 Mol Belgium May 1998 6 Menlove Passive Active Coincidence Collar for Total Pluto nium Measurement of MOX Fuel Assemblies Los Alamos National Laboratory report LA 9288 MX ISPO 170 May 1982 19 APPENDICES MO Aw gt P
33. f p for air pure water and borated water for a given fuel type to provide consistency during setup of the INCC program and for field measurements Actually p increases as the boron in the water increases because the boron shortens the dieaway time and results in a larger fraction of neutrons appearing within the gate width The MCNP REN MOX en Parameter Pw MOX fuel assembly provides values for p in air 0 026 Po that vary from f in air 0 75064 us 0 75 64 ps 0 014 for unborated 2200 ppm of boron oe ES The boron concentra 2200 ppm B tion can be checked f in 2200 ppm B 0 73964 us 0 73964 us and estimated using the doubles ratio from two gate measurements when a MOX fuel assembly is being measured We have selected a single p value corresponding to 2200 ppm boron concentration The p is selected to give the true M for the assem bly in borated water Since the majority of fresh MOX fuel assemblies are stored in approximately 2200 ppm borated water the borated water value of p was used Calibrating the UWCC using a MOX fuel assembly allows other UWCCs to be cross calibrated using Cf source positioned in the center of the UWCC reference count rate for cross calibration is obtained by placing a 2 Cf source with a calibrated neutron emission rate at the center of the UWCC active zone see Fig 11 The rates are listed in Table VI for both PWR and Fig UWCC c
34. g the known alpha method The UWCC mea surements provide underwater verification of the Pu effective rate of fresh MOX fuel based on a calibration curve shown in Fig 6 Multiplication Corrected Doubles D cps 0 2 4 5 10 12 14 16 1 20 22 24 26 240Pueff g cm Fig 6 Calibration curve for PWR MOX fuel verifications in borated water using INCC corrected doubles measurement data 5 HIGH VOLTAGE Before measuring the high voltage plateau for the UWCC the two PLATEAU DEAD TIME PDT 210A channels were matched to have the same gain Figure 7 shows the plateau curves for channels A and B for the He tubes RS P4 0811 105 The PDT 210A preamplifier allows the UWCC high voltage operating bias to be the standard 1680 volts TT used for 7000 safeguards 6000 neutron 2 522 measurement C 4000 systems 5 3000 5 2000 1000 1600 1700 1800 1900 Detector High Voltage Bias volts Fig 7 UWCC detector high voltage bias plateau curve The counting rates for the UWCC are high approximately 100 kHz for MOX fuel assemblies which causes a significant electronic deadtime effect The dead time was measured using two Cf sources that had a known absolute ratio of neutron emission rates The ratio for sources Cf 10 to Cf 4 is 55 6 The deadtime equations for corrected rates for the singles and doubles are given by as S corr S meas e D corr DX meas e where a be S 10
35. he other end of the cable connectors to the identified locations on the OR coupling box F 2 INCC PROGRAM SETUP 7 Attach the two fork protective fabric sleeves to the arms of the UWCC 8 Make sure that the detector head is on a padded surface to avoid damaging the welds on the SS cladding Carefully tip the UWCC on its side so that the long SS pipe can be attached to the top flange of the detector head 9 Have the facility operator attach lifting straps to the detector head and the long pipe so that it can be lifted into the water Have several in spectors or facility staff help guide the system into the water Keep the open end of the SS pipe and cable bundle on the side of the pool 10 Observe that there are no air bubbles coming from the detector head or the pipe joints Air bubbles would indicate a leak 11 After the SS pipe is vertical attach the clamps that will support the UWCC to the side rail or to the bridge crane 12 Extend the signal cable bundle to the location of the JSR 12 and computer Attach the cables to the OR box and the OR box to the JSR 12 using the labels on the cables and OR box 13 Turn on the JSR 12 in the manual mode and repeat step 6 however in this case the neutron signal will approach zero because of the water shielding around the UWCC 14 Attach the JSR 12 to the computer using the RS 232 cable 15 The UWCC is operated with the INCC program The INCC program should be configured
36. induced fission rates in the fuel assembly Measurements can be made on MOX fuel assemblies in air or underwater The neutron counting rate is analyzed for singles doubles and triples time correlations to determine the Pu effective mass per unit length of the fuel assembly The system can verify the plutonium loading per unit length to a precision of less than 1 in a measurement time of 2 to 3 minutes System design components performance tests and opera tional characteristics are described in this manual L R P DeBaere Euratom G Eccleston LANL I Cherradi IAEA and Menlove LANL with the UWCC INTRODUCTION use of fresh uranium plutonium mixed oxide MOX fuel in light water reactors is increasing in Europe and Japan and it is important for inspectors to verify the plutonium content in the fuel for international safeguards purposes Therefore an improved underwater coincidence counter UWCC shown in Fig 1 has been developed to verify fresh MOX fuel subassemblies in air or underwater at reactor storage ponds The UWCC can be configured to mea sure either boiling water reactor BWR or pressurized water reactor PWR fuel assemblies Fig 1 UWCC positioned around the Los Alamos PWR MOX fuel assembly to provide plutonium verification measurements underwater The UWCC uses high efficiency He neutron detectors to measure the sponta neous fission and induced fission rates in the fuel assembly The neu
37. positions where the neutron reflection is changed UWCC measurements in air on a metal Cart using A source number 8 UWCCS meliora pam Cross calibrations were performed with the UWCC on a cart and away from adjacent walls to minimize neutron reflections UWCC USER PROCEDURES Appendix F UWCC User Procedures There are two operational modes that use the UWCC A Portable mode in which the UWCC is shipped to the inspection site and configured inserted then removed from the reactor pool after each inspection visit and B Fixed installation in the fuel storage pool The user procedure described below covers operational mode A Opera tional mode B is a subset of mode A The UWCC is operated using the IAEA neutron coincidence counting soft ware INCC program The electronics to support the UWCC are the same as those used for the HLNC 2 and the AWCC i e a JSR 12 and a PC Any of the shift register or multiplicity electronics units may be used with the UWCC The particular unit used is specified in the INCC setup program Also this program contains the setup information for the gate predelay HV deadtime constants etc These can be entered into the INCC program or set on the electronics unit if manual setup is required prior to the field exercise The first step in collecting UWCC verification measurements is to configure the mechanical pieces connect the wiring to the shift regi
38. ross calibration geometry and 22 source holding fixture 11 BWR geometries The data in Table VI are also corrected for dead time The UWCC parameters used for the measurements are listed in Table IV When performing a cross calibration care must be taken to avoid neutron reflection from the table or floor supporting the UWCC The UWCC should be positioned about one meter above the floor and at least a meter away from the walls A metal pushcart was used to support the UWCC when collecting the cross calibration data shown in Table VI A special fixture shown in Fig 11 is supplied with the UWCC to hold the Cf source in the center of the active zone The fixture adjusts to both BWR and PWR geometries Table VI UWCC Configuration 2Cf Cf 8 Reference Rates for Cross Calibration Singles S Doubles D cps cps 4092 178 3 0 05 5800 350 6 2 9 BORON EFFECTS The multiplication constant p is dependent on the boron in the water because the boron decreases the die away time for neutrons in the fuel assembly This decrease in t results in an increase in the gate fraction fg given by f et e7 where PD pre delay 3 us G gate length 64 us and t die away time Figure 12 shows a plot of fg versus t for the UWCC for gate lengths of 32 64 and 128 us The t values for pure water and borated water were measured for a PWR MOX assembly and the values are indicated in Fig 12 The
39. s in 2200 ppm borated water d ok PO 17 Neutron doubles and multiplication corrected doubles calibration for PWR MOX PGW rpm 18 Table l Table Il Table lll Table IV Table V Table VI Table VII Table VIII LIST OF TABLES UWCC Helium 3 Detector Specifications sese 4 UWCC Measurement Parameters Setup eese eene 6 Californium Cf7 UWCC Dieaway Time Measurements in Air 7 UWCC Dieaway Time Measurements for PWR MOX Assembly in Water 8 UWCC Multiplication Constants esses esee eene nennen nennen tnn 11 2520 f Cf 8 Reference Rates for Cross Calibration ee 12 Mol MOX Fuel SOTO PICS 2 2 RUEDA SR EX 14 Los Alamos MOX Fuel Isotopics eese eese ee eren eene nn nennen nennt ntn 15 USER S MANUAL THE UNDERWATER COINCIDENCE COUNTER FOR PLUTONIUM MEASUREMENTS IN MIXED OXIDE FUEL ASSEMBLIES by G W Eccleston H O Menlove M Abhold M Baker and J Pecos ABSTRACT This manual describes the Underwater Coincidence Counter UWCC that has been designed for the measurement of plutonium in mixed oxide MOX fuel assemblies prior to irradiation The UWCC uses high efficiency He neutron detectors to measure the spontaneous fission and
40. s rate as a function of gate width for a Cf source in air and a MOX assembly in pure water with the data normalized to unity for at the 32 is gate width UWCC Measurement Jan 20 1998 Neutron Doubles versus Gate Width Fig 8 Doubles rate zi versus the PWR MOX in E Unborated Water coincidence gate width for the UWCC in air with a Cf source and in water from a PWR MOX fuel assembly Normalized Neutron Doubles 20 40 60 80 100 120 140 Gate Width usec Fig 9 Relative statisti cal error for the doubles rate versus gate setting for Cf in air and for a PWR MOX fuel assembly in water EFFICIENCY Figure 9 shows the relative counting statistical error versus the gate length for the same cases air and water The error is a minimum for a gate setting at approximately 80 us in water For the case of MOX fuel in borated water the dieaway time is slightly higher than for air approximately 40 us Since most MOX fuel assemblies are stored in borated water we have chosen gate setting of 64 us for applications of the UWCC to MOX fuel assemblies A gate increase to 128 us would result in a doubling of the counting time needed to obtain the same counting statis tics obtained statistics obtained for the 64 5 gate UWCC Relative Error versus Gale Width January 20 1998 Relative Error 9 Gate Width usec The efficiency of the UWCC was measured by placing a calibrated 2Cf sourc
41. ster electronics and then to the computer Following system configuration electronic tests are performed and the UWCC can be placed into the pool In the case of fixed installations the system would be maintained in the pool and all electronic wiring would be in place Once the UWCC is in the pool electronics checks and observations are performed so that verification measurements can cor rectly ensure that the unit is operating properly and hasn t been damaged The UWCC detector head and cables are shipped in a reusable fiberglass case with rolling wheels The detector pipe sections that clamp together to reach the appropriate depth in the water are shipped in tubes or boxes that are about 2 m long The detector head contains the dual PDT 210A preamplifier and is pre assembled and sealed up to the point of the cable disconnect to the exten sion pipes The contents in the detector shipping container include the UWCC detector head configured to the PWR or BWR measurement geometry the protective fabric sleeves for the arms of the fork e the approximately 20 m of cable run to reach between the head and the OR sum coupling box surface electronics the OR box to combine the two signal lines from the PDT 210A amplifier to feed into the JSR 12 e the approximately 40 cm cable extension between the OR box and the JSR 12 e aclamp to attach the UWCC pipes to the side rail or bridge rail and e all necessary tools for assembly
42. t2ype by select ing Maintain Calibration Passive Calibration Curve The curve type should be of the form D atb mtc m 2td m 3 The UWCC calibration is a linear relationship with a zero intercept between the multiplication corrected doubles D and Pu g cm loading of a full MOX fuel assembly Therefore the calibration constants a c d 0 0 and only the constant b has a value which is dependent on the type of MOX fuel assembly PWR or BWR and the boron content in the pool 0 or 2200 ppm The calibration constant for PWR MOX fuel shown in Fig 20 in a pond containing 2200 ppm boron is b 25 1 c s g cm 22 Using the Acquire Background option collect 10 cycles of 30 sec background counts The data source for this measurement should be Shift register The UWCC should be under the water in the measurement configu ration with no fuel assembly inserted in the unit 23 Have the operator center a fresh MOX fuel assembly into the UWCC and position it up against the polyethylene bumper 24 Using the Acquire Verification option input the item id material type declared mass and then collect 6 cycles of 30 sec verification counts Note that the item id must clearly identify the particular measurement and assembly because it is the key identifier that will be used to reanalyze report and review verification measurements Appendix F provides guidance on defining item id names BORON C
43. the cadmium liner thick ness was increased to 1 0 mm gt in the location directly between Fig 3 UWCC forks showing polyethylene and the the fuel assembly and the He cabling to the He neutron detectors tubes The cadmium Table I UWCC Helium 3 Detector Specifications covered polyethyl Model number RS P4 0811 105 ene con Number of tubes EER eee tains the Tube cladding He detec tors as shown in Fig 3 Each of the UWCC forks contain four He tubes with the specifica tions listed in Table I PREAMPLIFIER The UWCC uses a dual channel PDT 210A amplifier with one AMPTEK PDT 210A channel for four He detectors Figure 4 shows the wiring between the He tubes and the PDT 210A amplifier The detectors are cross wired between the two forks and each AMPTEK channel collects signals from two detectors in each fork The cable length between the tubes and the PDT 210A ampli fier is approximately 45 mm The amplifier output pulse is set for 50 ns The distance between the PDT 210A and the shift register should be 20 m or less A signal summer box shown Fig 4 Wiring from in Fig 5 connects the PDT 3 2 A 210A to the shift register amplifier electronics The summer box passes HV and 5V from the shift register module to the PDT 210A and ORs the Dual Arapteks output of the two digital pulses to produce one pulse stream which is then fed into the shift register
44. the totals and the doubles rates have larger variations with position than the The plutonium calibration is based on the D rate Singles Doubles and cps 5 4 3 2 1 0 1 2 3 4 5 6 7 MOX Fuel Position in the UWCC Fig 10 UWCC neutron singles doubles and multiplication corrected doubles response vs position cm of the PWR MOX fuel assembly along the length of the UWCC arms MULTIPLICATION For the conventional two parameter known alpha analysis of neutron coinci CONSTANT dence data the constant p represents a nonmultiplying sample and is defined as R 2 1 Po T where is the calculated ratio of alpha particle induced neutrons to spontane ous fission neutrons Because R is directly proportional to the gate fraction for the doubles rate we have p at an approximate efficiency of f We cannot measure p because we do not have a nonmultiplying fuel assembly with the geometry of a PWR or BWR fuel assembly The value of p is di rectly proportional to the efficiency therefore the higher efficiency of the BWR configuration will result in a higher p for BWRs than for PWRs The value of p can be determined using MCNP calculations to obtain the neutron leakage multiplication M of the assembly in water The p is se lected to give agreement between the MCNP value of M and the two param eter analysis of M 10 CROSS CALIBRATION 222 Cf source In Table V we have used the same value o
45. tron counting rate is analyzed for singles S doubles D and triples T time correlations to determine the Pu effective mass as well as the reactivity of the fuel assembly The UWCC can verify the plutonium loading per unit length to a precision of under 1 in a measurement time of 2 to 3 minutes Calibration of the UWCC was determined through measurements of MOX fuel in Mol Belgium and in Los Alamos The Mol fuel array allowed calibra tion measurements up to Pu effective loadings of 6 8 g cm The Los Alamos MOX fuel allowed the calibration to be extended up to a effec tive loading of 14 83 g cm This manual provides the design specifications performance tests operational parameters and preliminary calibration information for the UWCC UWCC DESIGN The UWCC design was based on MCNP calculations These calculations attempted to determine the effects of cadmium and to specify the front and back dimensions of polyethylene located around the detectors which optimize efficiency while reducing the effect of boron concentration The goals of the UWCC development were e underwater partial defect verifications 696 1 sigma on fresh MOX fuel assemblies stainless steel cladding for improved decontamination measurement time less than 5 minutes per assembly configurable for measurements of BWR and PWR MOX fuel subas semblies insensitivity to detector positioning around a fuel assembly use of standard neutron coinciden
46. unt time secs type 30 Use number of cycles Select Dot Number of cycles Select 10 QC tests Select X in box Data source Select Shift register Select OK Select Acquire Verification Collecting Verification Data for PWR MOX fuel in 2200 ppm boron MBA Select P2 Pond with 2200 ppm B Item id type Measurement Material type Select POX Select Isotopics Isotopics id Select ISO1 Select OK Select OK Declared mass 2 type 240Pueff g cm number Comment type PWR MOX Fuel ID Count time secs type 30 Use number of cycles Select Dot in circle Number Cycles type 6 Data source Select Shift register QC tests Select X in box Select OK refer to the end of this Appendix for suggestions on defining clear id names 2 Repeat the step above to collect additional verification measurements for different PWR and fuel assemblies Change the Measurement id and Comment for each new verification Suggested Measurement id Names The INCC program stores measurement filesin a database and each file is identified with a measurement id 12 characters plus the date and time when the measurement occurred or when the data was reanalayzed It is possible therefore to have a number of different measurements or a measurement with a number of reanalysis that all have the same name and the only difference would be in the date and time of each measurement or reanalysis For this reason confusion may occur in locating and identifying individual files if
47. up two material types for PWR MOX PMOX and BWR MOX BMOX 8 Select Maintain Material Type Add Delete 9 Select Add material type Material type type PMOX Select OK 10 Select Add material type Material type type BMOX Select OK Select OK Select facility and measurement parameters for UWCC verifications at a PWR facility which has fresh MOX fuel in a pond containing 2200 ppm boron 1 Select Setup Facility Inspection Facility Select PWR Reactor Select P2 Pond with 2200 ppm B Detector id Select UWCC3 Select OK Setup UWCC Calibration parameters to verify PWR MOX fuel in 2200 ppm Boron 1 Select Maintain Calibration Passive Calibration Curve Material type Select PMOX Curve type Select D a b mtc m 2rd m 3 a type 0 0 b type 25 1 0 0 d type 0 0 Select OK Specify analysis methods for the verification measurement of PWR MOX 2 Select Maintain Calibration Analysis Methods Material type Select PMOX Passive Calibration curve Select X in box Passive Known alpha Select X in box Select OK Normal analysis method Select Dot calibration curve Backup analysis method Select X Known alpha Select OK 3 Select Maintain Calibration Known Alpha Material type Select PMOX Alpha weight type 1 0 Rho zero type 0 014 k check 2 166 Select OK Collecting background data prior to verification measurements 1 Select Acquire Background Comment type PWR background data Co
48. wer left corner of screen 2 Mouse select Programs INCC 3 XY INCC 3 XY XY INCC version number Setup UWCC Measurement Parameters Set the INCC to allow access to Maintenance mode parameters 1 Mouse select View Maintain 2 Check that Maintain appears on the bar menu at the top of the screen File View Setup Maintain Acquire Reanalyze Report Tools Window Help Setup Measurement Parameters for Detector UWCC3 unit 3 1 Select Maintain Detector Add Delete 2 Select Add Detector Shift register serial port Select 1 Detector id type UWCC3 Select OK Shift register type Select JSR 12 Predelay type 3 0 Gate length type 64 0 High voltage type 1680 Die away time type Die away time type Efficiency type 0 0 Deadtime coefficient A type 2 18 Deadtime coefficient B type 2 18 Deadtime coefficient C type 0 0 Doubles gate fraction type 0 7 Triples gate fraction type 0 49 Select OK Select OK Input facility type and two MBAs for a borated and an unborated fuel pond 3 Select Maintain Facility Add Delete 4 Select Add Facility Facility type PWR Facility description type Reactor Select OK 5 Select Maintain MBA Add Delete 6 Select Add material balance area Material balance area type P1 Material balance area description type Pond unborated Select OK p Select Add material balance area Material balance area type P2 Material balance area description type Pond with 2200 ppm B Select OK Select OK Set
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