ML17289B147
| ML17289B147 | |
| Person / Time | |
|---|---|
| Site: | Columbia  |
| Issue date: | 02/02/1993 |
| From: | Sorensen G WASHINGTON PUBLIC POWER SUPPLY SYSTEM |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| GO2-93-024, GO2-93-24, IEB-90-002, IEB-90-2, TAC-M76354, TAC-M82920, NUDOCS 9302120132 | |
| Download: ML17289B147 (22) | |
Text
ACCELERATE'D DOCUMENT DIS'103BUTION SYSTEM REGULATORY INFORMATION DISTRIBUTION SYSTEM (RIDS)ACCESSION NBR:9302120132 DOC.DATE: 93/02/02 NOTARIZED:
YES FACIL:50-397 WPPSS Nuclear Project, Unit 2, Washington Public Powe AUTH.NAME AUTHOR AFFILIATION
, SORENSEN,G.C.
Washington Public Power Supply System RECIP.NAME RECIPIENT AFFILIATION Document Contxol Branch (Document Control Desk)DOCKET N 05000397
SUBJECT:
Suppls listed responses to NRC Bulletin 90-002,"Loss of Thermal Margin Caused by Channel Box Bow," effect on Cycle 9 operation.
Requests NRC approval for plan to reuse channel boxes during Cycle 9.DISTRIBUTION CODE: IE38D COPIES RECEIVED:LTR ENCL SIZE: TITLE: NRC Bulletin 90-002, Loss of Thermal Margin Caused by Channel Box Bow NOTES: RECIPIENT ID CODE/NAME.PD5 LA CLIFFORDF J INTERNAL: AEOD/DOA NRR FIENO,D NRR/DET/EMEB 7E NRR/DOEA/OGCBll NRR/Dggf 8E2 GREG FILED 02 RGN5 FILE 01 EXTERNAL: NRC PDR COPIES LTTR ENCL 1 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 RECIPIENT ID CODE/NAME PD5 PD AEOD/DSP/TPAB NRR LONGFW PD31 NRR/DOEA/OEAB11 NRR/DREP/PEPB9D NRR/PMAS/ILRB12 RES/DSIR/EIB NSIC COPIES LTTR ENCL 1 1 1-1 1 1 1 1 1 1 1 1 1 1 1 1 NOTE TO ALL"RIDS" RECIPIENTS PLEASE HELP US TO REDUCE WASTE!CONTACT THE DOCUMENT CONTROL DESK, ROOM Pl-37 (EXT.504-2065)TO ELIMINATE YOUR NAME FROM DISTRIBUTION LISTS FOR DOCUMENTS YOU DON'T NEED!TOTAL NUMBER OF COPIES REQUIRED: LTTR 18 ENCL 17 A WASHINGTON PUBLIC POWER SUPPLY SYSTEM P.O.Bax 968~3000 George Wasbtngton Way~Rtcbland, Wasbtngton 99352496'8
~(509)372-5000 February 2, 1993 G02-93-024 Docket No.50-397 U.S.Nuclear Regulatory Commission Attn: Document Control Desk Washington, D.C.20555
Subject:
%NP-2, OPERATING LICENSE NPF-21 RESPONSE TO NRC BULLETIN NO.90-02: "LOSS OF THERMAL MARGIN.CAUSED BY CHANNEL BOX BOW", EFFECT ON CYCLE 9 OPERATION (TAC No.M82920)
References:
1.NRC Bulletin No.90-02, March 20, 1990,"Loss of Thermal Margin Caused by Channel Box Bow" 2.Letter, G02-90-075, April 13, 1990, GC Sorensen (SS)to USNRC,'Modification of WNP-2 Cycle 6 Reload Submittal and Response to NRC Bulletin No.90-02: Loss of Thermal margin Caused by Channel Box Bow" 3.ANF-524(P)(A), Rev.2, Supplements 1 and 2, November 1990,"Advanced Nuclear Fuels Corporation Critical Power Methodology for Boiling Water Reactors" 4.Letter, G02-90-162, September 28;1990, GC Sorensen (SS)to USNRC,"Final Response to NRC Bulletin No.90-02: Loss of Thermal Margin.Caused by Channel Box Bow" 5.Letter, G02-91-037, February 25, 1991, GC Sorensen (SS)to USNRC,"Request for Additional Information Regarding NRC Bulletin 90-02, Loss of Thermal Margin Caused by Channel Box Bow" 6.Letter, April 22, 1991, PL Eng (NRC)to GC Sorensen (SS),"Evaluation of Response to NRC Bulletin No.90-02: Loss of Thermal Margin Caused by Channel Box Bow (TAC No."'76354)" 7.Letter, G02-92-048, February 25, 1992, GC Sorensen to USNRC,"Response to NRC Bulletin No.90-02: Loss of Thermal Margin Caused by Channel Box Bow, Effect on Cycle 8 Operation" 8.Letter, June 15, 1992, WM Dean (NRC)to GC Sorensen,"Evaluation of Response to NRC Bulletin No.90-02: Loss of Thermal Margin Caused by Channel Box Bow (TAC No.M82920)" g)Oc;t h 9302i20l32 930202 PDR ADOCK 0500039'7 PDR Page Two RESPONSE TO NRC BULLETIN NO.90-02: "LOSS, OF THERMAL MARGIN CAUSED BY CHANNEL BOX BOW", EFFECT ON CYCLE 9 OPERATION (TAC No.M82920)Reference,1 requested that licensees reusing channel boxes verify that current Minimum Critical Power Ratio (MCPR)Technical Specification operating and safety limits are met.All affected licensees were requested to advise the NRC of the number and location of such channel boxes and to describe the methods and associated data base used to account for the effects of channel box bow during reuse of channel boxes to ensure conformance with the CPR limits.The Supply System responded to this bulletin in References 2, 4, 5 and 7.Reference 6 provided WNP-2 the NRC evaluation of the issues for Cycle 7, and Reference 8 for Cycle 8.Reference 6'required that the reuse of channel boxes in future cycles be evaluated on a cycle specific basis.This letter responds to those requirements for WNP-2 Cycle 9.The effect of potential channel box bow on CPR limits was evaluated in the Cycle 9 design.WNP-2, a C-lattice BWR, is less susceptible than a D-lattice BWR to the phenomena of and effects from channel box bow.The Supply System, aware of the potential problems associated with channel box bow, has had a channel management program in place since initial operation of WNP-2.The WNP-2.channel management program consists of data collection on channel operating history and actual measurement of channel distortion as a function of channel.operation.
The current goal of the channel management program is to use a channel box for a single assembly lifetime.To achieve this goal, the Supply System is currently putting new channels on new fuel.During the transition the Supply System will discharge channels predicted , to achieve a target burnup of approximately 50 GWd/MTU in a cycle or perform an analysis to justify continued use.Reference 4 discusses the basis for the selection of the exposure target and analytical methodology.
In Cycle 8, 291 of the 764 channels in the WNP-2 core were reused channels.In Cycle 9 there will be 232 reused channels.Twenty-four (24)channels will be replaced at the end of Cycle 8 because their exposures at the end of Cycle 9 are expected to exceed 50 GWd/MTU.These channels will be replaced with less exposed channels from the spent fuel pool.Each of the 24 replacement channels has been measured for channel box bow and bulge and meets the pre-determined acceptance criteria of Reference 4.At the end of Cycle 9, the peak reused channel exposure is predicted to be less than 49 GWd/MTU.EXPOSURE RANGE~d/UANTITY 27-34 34-41 41-48 42-42 148
~~Page Three RESPONSE TO NRC BULLETIN NO.90-02: "LOSS OF THERMAL MARGIN CAUSED BY CHANNEL BOX BOW", EFFECT ON CYCLE 9 OPERATION (TAC No.M82920).Beginning with Cycle 7, the effects of channel box bow were addressed in WNP-2 reload design using the approved Siemens Power Corporation (SPC)methodology for determining the Safety Limit Minimum Critical Power Ratio (SLMCPR)(Reference 3).The SPC data incorporated in the SPC methodology has been reviewed previously by the NRC (including WNP-2 measured data)and along with the methodology has been approved by the NRC (Reference 3).The SLMCPR established for Cycle 9 operation of WNP-2 will include the effects of channel box bow as analyzed by this methodology.
During Cycle 9, 232 reused channels will be in the WNP-2 core, The planned location coordinates for each reused channel for Cycle 9 are given in Table 1.The location of each reused channel is also indicated on the attached Figure 1 (core map)by assembly number.The appropriate channel number for each assembly number can be determined from Table 1.A total of 76 of the reused channels will be located face adjacent to new fuel assemblies.
Experience has'shown that limiting assemblies are almost always once burned assemblies and, potentially at the end of a long cycle, fresh assemblies can be limiting.However, the precise location of limiting assemblies during Cycle 9 will be dependent upon the actual operating experience.
A reused channel could, therefore, be adjacent to a limiting assembly at some ti'me during Cycle.9 operation.
The probability of this occuring is recognized and taken'into account in calculation of the SLMCPR using the SPC methodology.
Channel distortion (bow+bulge), magnitude and direction, is directly dependent upon the location history of the channels.The channels that will have the largest estimated exposure at end of cycle are channels 60890 and 73399.The channels will reside in core location 23,2 and 23,29 respectively (row and column coordinates from the upper left corner as shown in Figure 1).The Supply System analytical model predicts a maximum calculated total distortion for these channels to be less than 105 mils.Total distortions for the other reused channels in WNP-2 shown in Table 1 are predicted to be less than this value.The anticipated effect of maximum channel bow is accounted for in the MCPR operating limit by modification of the SLMCPR, which is a part of the MCPR operating limit.The WNP-2 SLMCPR is established through statistical consideration of measurement and calculational uncertainties associated with the thermal hydraulic state of the reactor using design basis radial, axial and local power distributions and considering fuel channel bow.Reference 3 discusses vendor MCPR safety limit methodology and describes in detail how channel bow effects are incorporated irito, the MCPR safety limit.The effects of channel bow increase the WNP-2 Cycle 9 MCPR safety limit by about 0.02, P Page Fqur RESPONSE TO NRC BULLETIN NO.90-02: "LOSS OF THERMAL MARGIN CAUSED BY CHANNEL BOX BOW", EFFECT ON CYCLE 9 OPERATION (TAC No.M82920)In accordance with the requirements of IEB 90-02 and Reference 6, the Supply System is requesting NRC approval for this plan for the reuse of channel boxes during Cycle 9.The channels are to be loaded into the core during the spring 1993 refueling outage, scheduled for 45 days beginning in April.Therefore, prompt NRC approval of this submittal would be appreciated.
Sincerely, G.C.Sorensen, Manager Regulatory Programs (Mail Drop PE20)JDF:bw Attachments:
1;2.Table 1;Reused Channels, Assemblies And Projected Exposure Figure 1;Cycle 9 Load Pattern Showing Assemblies with Reused, Channels CC: JB Martin-NRC RV NS Reynolds-Winston&Strawn JD Clifford-NRC DL Williams-BPA/399 NRC Site Inspector-901A STATE OF WASHINGTON
))COUNTY OF BENTON)
Subject:
Res onse to IEB 90-02 I.G.C.SORENSEN, being duly sworn, subscribe to and say that I am the Manager, Regulatory Programs for the WASHINGTON PUBLIC POWER SUPPLY SYSTEM, the applicant herein;that I have the full authority to execute this oath;that I have reviewed the foregoing; and that to'he best of my knowledge, information, and belief the statements made in it are true.DATE Z HWMdyd'C/Ayy&
, 1993 G.C.Sor nsen, Manager Regulatory Programs On this date personally appeared before me G.C, SORENSEN, to me known to be the individual who executed the foregoing instrument, and acknowledged that he signed the same as his free act and deed for the uses and purposes herein mentioned.
GIVEN under my hand and seal this~tday of 1993~M(otary Public in and for the STATE OF WASHINGTON Residing at Kennewick Washin ton My 2 y y 2*Ay~A'I 2 I Reused Table 1 Channels, Assemblies', and Projected EOC 9 Exposures Row Column Current Assembly Channel ID Proj.EOC 9 Exposure 1 1 1 1 1 1 1 1 1 1 1 1 1 1 2 2 3 3.3 3 3 3 4 4 4 4 4 4 5 5 5 5 5 6 6 6 6 6 6 6 6 6 6 6 9 10 11 12 13 14 15 16,, 17 18 19 20 21 22 8 23 6 7 9, 16 24 25 6 7 10 14 24 25 5 11 13 20 26 3 4 5 6 8 9 10 22 25 26 27 AN3042 AN3075 AN3033 AN3067 AN3066 AN3036 XN2087 XN2095 AN3008 AN3095 AN3098 AN3021 AN3107 AN3025 AN3068 AN3096 AN3040 XN2091 UD4034 XN2108 XN2099 AN3126 AN3099 AN3064 UD4115 UD4032 AN3028 AN3045 AN3031 AN3074 UD5066 AN3090'N3029 AN3038 AN3051 AN3133 AN3043 UD5071 AN3092 UD5064 AN3089 AN3083 AN3134 AN3119 71970 73079 73130 61769 73366 63602 71965 70104 71758 5938D 5900D 71458 71808 63257 70287 70257 73367 71387 72009 73379 61638 71933 71956 72035 70190 62686 72474 71914 71389 73425 71780 73390 72439 71756 63949 71927 6450D 71938 63572 71198 62513 71809 73384 63442 46918 47612 46740'7193 44038 44649 39247 39371 44586 37527 38424 46740 44849 46819 45588 45296 44748 36125 41880 40563 42632 47186 47126 41718 30912 30303 41533 47621 44510 47607 43637 47681 43969 47099 47120 45963 37847 37852 44270 45818 44359 46523 45177 47161 Table 1 (Cont.)Row Column Current Assembly Channel ID Proj.EOC 9 Exposure 6 7 7 7 7 7 7 8 8 8 8 8 8 8 9 9 9 9 10 10 10 10 10 10 11 11 11 11 11 12 12 12 12 12 12 13 13 13 14 14 14 14 15 15 15 15 28 3 8 12 19 27 28 2 8 10 11 12 21 29 1 6 25 30 1 4 8 23 27 30 1 5 23 26 30 1 7 15 16 24 30 1 8 30 1 23 25 30 1 8 12 15 AN3130 XN2086 UD5070 AN3039 AN3125 AN3124 XN2094 AN3034 UD5072 AN3070 UD4025 UD5063 AN3027 AN3022 AN3032 AN3104 AN3085 AN3030-AN3076 UD4024 AN3079 AN3084 UD4022 AN3097 AN3100 AN3053 UD4031 AN3103 AN3049 AN3052 AN3069 AN3035 AN3007 AN3081 AN3120 AN3054 UD5065 AN3082 AN3080 UD4029 UD5013 AN3001 XN2084 UD5030 AN3041 UD5069 6012D 71300 71945 71789 71755 71376 71761 71757 70238 5881D 70279 71817 71437 72027 71942 72039 73394 71443 5809D 73124 63445 71391 73386 71400 73120 5898D 72038 73154 72024 71958 73116 71986 5960D 73111 73226 63427 61550 71447 5866D 73117 70110 71790 71936 71848 73108 63492 35556 36550 45874 45729 45584 41594 35989 45307 46115 37854 43736 44770 46213 47311 43959 47033 46329 44097 39001 31375 46813 47052 37823 47663 46830 39081 44572 39070 46828 46391 46028 45280 36559 37074 46857 45912 40884 34336 36350 30712 46305 45294 39297 45400 44889 46029 Table 1 (Cont.)Row Column Current Assembly I'Channel ID Proj.EOC 9 Exposure ,, 15 15., 15 16 16 19 23 30 1=4 16 16 16 16 16 16 16 16 16 17 17 17 17.17 17 17 18 18 18 18 18 19 19 19 19 19 19 19 19 19 19 19 20 20 20 20 20 12 15 16 19 20 21 24 25 30 1 10~12 19 21 29 30 1'22 23 30'10 11, 14 15 16 17 20 21 24 30 1 5 9 ll 12 16 6 16 7-16 10 16 11 AN3026 UD5035 XN2067 XN2066"UD5040 UD4016 UD4021 UD4143 UD5036 AN3020 UD5028 UD5025 AN3060 UD5022 UD4140 UD4003 UD4139 XN2100 AN3002 UD4144-UD4012 UD4134 UD4142 UDS026 AN3122 AN3058 UD5039 UD5031 UD5021 AN3112 AN3019 UD4005 UD5010 UD4039 AN3056 AN3078 UD4007 UD5024 UD4014 AN3023 AN3063 AN3086 AN3057 UD4033 UD4041 UDS004 72001 71983 73582 61972 62522 71904 73232 72042 73238 63956 71962 71141 71268 70252 71801 63953 73132 71959 62283 71434 71950 70167 6028D 61750 71928 73388 70011 73415 71799 71990 71852 73089 72034 71835 61741 71967 73426 61529 72018 5850D 62937 70047 5802D-71795 71923 71908 45348 45006 39887 33095 43137 32845 47418 32464 42577 45756 45397 46076 45592 42717 29988 47417 30540 33173 36432 30213 33116 30230 36462 42583 42349 45791 43890 43998 43411 45473 47231 33984 44953 32198 45434 45621 31688 44728 29767 37057 47021 44381 39070 30131-33693 45676 Table 1 (Cont.)Row Column Current Assembly Channel ID Proj.EOC 9 Exposure 20 20 20 20 20 20 20 20 21 21 21 21 21 21 21 21 21 21 21 21 21 21 22 22 22 22 2.2 22 22 23 15 16 20 22 24 26 29 30 1 2 8 10 12 14 15 16 17 19 21 23 29 30 1 6 11 13 20 25 30 23 23 23 23 23 24 24 24 24 24 24 24 24 15 17 21 25 29 3 4 7 8 11 12 16 19 23,8 23 10 23 14 UD5016 UD5037 UD4036 UD4023 UD5033 AN3111 UD5023 AN3091 AN3073 UD4042 AN3128 UD4038 UD4015 UD4027 UD4040 UD4035 UD4008 UD4013 UD4083 AN3016 UD4135 AN3116 AN3123 AN3050 UD4026 UD5014 UD4037"AN3093 AN3048 AN3011 UD5011 AN3131 UD4116 UD5018 UD4004 AN3121 UD5029 AN3061 XN2056 AN3037 UD4138 UD5017 UD5009 AN3055 UD4030 AN3077 71356 71830 73441 73614 70158 73135 73069 73112 72036 71943 72021 73403 5912D 71393 71786 71957 71907 71770 71953 71448 71975 63947 71991 71449 71778 71759 61931 73420 70272 60890 71930 72041 71392 61538 73444 71444 61773 73399 72023 72037 71334 63943 71913 73171 71308 71812 42790 42962 34195 39187 45086 47628 42591 46828 47663 46205 47002 31013 34227 30450 32216 47804 30224 27878 31549 46513 43694 47633 46059 35546 30170 44377 31023 47024 43959 48146 45838 46552 31006 45268 38303 46808 44513 47943 42227 41502 30007 45859 45563 46086 47347 45669 Table 1 (Cont.)Row Column Current Assembly Channel lD Proj.EOC, 9 Exposure'24 24 24 25 25 25 25 25 25 25 25'25 25 25 25 26 26 26 26 26 27'27 27 27 27 27 27 27 27 28 28 28 28 28 29 29 30 30 30 ,30 30 30 30 30 30 30 24 27 28 4 5 6 8 9 14 15-22 25 26 27 28 5'1 18 20 26 6 7 10 12 14 16 19.21 25 7 15 16 24 25 20 23 9 10 ll 12 13 14 15 16 17 18 UD4 13 6 AN3129 XN2068 AN3013 AN3102 AN3012 UD5020 AN3088 UD5008 UD4028 AN3094 AN3059 AN3065 AN3005 AN3006 AN3044 AN3087 UD5034 AN3105 AN3047 AN3101 AN3018 UD4011 UD4137 UD4006 UD5038 UD4141 UD4132 AN3108 XN2081 XN2073 XN2060 XN2078 AN3017 UD5032 AN3109 AN3127 AN3071 AN3132 AN3072 AN3114 AN3014 XN2065 XN2052 AN3015 AN3106 70103 71442 61682 71838 71753 5999D 71791 5905D 71377 73368 5852D 5868D 71976 73 15'3 71912 73422 61578 71771 70206 73133 61523 71431 71792 62501 71954 71960 71369 63950 71994 71390 71964 73416 61673-73139 70243 73121 70102 73131 71981 71788.5805D 71985 71921 61526 72014 5932D 30045 41286~42817 47089 36910 37819 44261 35518 46817 30426 38237 35158 39663.47029 47221.44510 47363 44582 47141 41869~47454 41309 30625 30375 31509 43 602.30376 ,30900 47321 36125 40563 33610.42327 47186 42458 47750 46819 35907 46882 47029 34826 44707 32884.32863 44802-37651 Table 1 (Cont.)Row Column Current Assembly Channel ID Proj.-EOC 9 Exposure 30 19 30 20 30 21 30 22 AN3110 AN3024 AN3115 AN3062 71773 71445 73227 71890 46884 47032 47512 46812 6 Figure 1 Cycle 9 Load Pattern Showing Assemblies with Reused Channels 1 2 4 5 6 7 8 9 10 11 12 13 14 15 2 3 4 5.'7 8 9 AH3032*10 AN3076>>11 AH3100*12 AH3052*13.AH3054*14 AN3080*15 XH2084>>16 XN2066>>17 AN3002" 18 AN3058*19 AN3019*20 AN3086*21 AH3073*22 AH3123*23 24 25 26 27 28 29 30 AH3034*UD6052.UD41'11 UD 5121 UD6057 UD6114 UD5054 UO6115 UD6002 UD5075 UD6012 UD6078 UD5085 UD4042*UD6079 AN3011*AN3038*XN2086>>UD6058 UD4122'MPS UD6041 WPS UD7068 WPS XH2024 XH2071 WPB UD7053 WPB UD 6015 WPB UD4071 UD6077 XH2056*AN3009 AH3051*AN3046 UD6053 WPB UD4024>>UD7005 UD4017 UD511'I UD4054 UD 5130 UD5040*UD4097 UD5086 UD4077 l$7031 UD4076 WPB UD6110 AH3037*AN3013*AH3031>>AH3133*UD6056 WPB UD7024 WPS AH3053*WPS UD 5127 WPS UD 7019 UD 7011 WPS UD5080 WPS AH3057*WPB UD7065 WPS UD6072 AH3102*AH3044*AN3040*AN3099*UD4146 AH3043*UD6112 UD5129 AN3104*LYV153 UD6037 UD6060 UD6036 UD5087 UD4062 UD 4016*UD 5134 UD6034 UD6080 UD6100 LYV156 AN3050*UD5078 UD6001 AN3012>>UD4145 AH3101*AN3118 XH2091*AN3064*UD6054 UD6120 UD4112 UD 5135 UD7089 WPS UD5126 Ak3069*UD7090 WPS UD4088 UD4021>>WPB UD7072 AN3010 UD5094 WPB UD7046 UD5102 un4138*UD6017 UD6067 AN3018*XH2081*AH3042*AN3068*uo6038 uo6113 uo4034*UD6075 WPB MPB UD7078 UD5071*AH3092*UD5070*UD7021 UD5072>>UD6061 UD6062 UD4128 AN3079*WPS UD4121 UD4117 UD5132'WPS UD5065*uo5055 UD4052 WPB UD5030*UO5007 UD5042 UD5019 UD4091'WPS UD5095 UD5039*UD5103 WPB UO4072 UD4033*AH3128*'WPS UD6021 UD4131 UD5011*UD6029 UD5017*UD7060 UD5020*AN3088*WPS UD7080 UD6111 WPB UD6073 UD4094 AN3113 UD6014 AH3127" AH3075>>AH3033*UD4018 UD5124 WPB UD6068 UD4115*UD7095 WPB AH3074*uo5o64>>uo6os7 WPB UD5058 AH3070>>UD4025*WPS UD4108 UD4045 WPS WPS UD4100 UD4047 UD5123 UD7020 UD7023 UD4113 WPB UD4061 UD5056 UO4143>>un5036*UD4144>>WPS UD7062 UD7047 UO4005*UD5010*WPB UO4041*UD4038*WPB'WPB UD4026*AH3131*UD4087'WPB UD5009*UD5076 UD6105 WPS AN30S7*UD4011*UD7054 WPS UD6055 UD4078 UD5081 AH3071*AH3132*Ak3067*AH3066*UD6069 UD6059 WPB UD7030 UD4114 WA6003'WPB UD5066*UD6013 UD6028 AN3039*UD7064 UD5063*UD5125 WPB UD5062 UD4048 UD7087 UD5131 UD7093 UO4043 UD6108 UD6103 UD4053 UD4104 WPB AN3041*UD6094 AH3020*UD6117 UD4012*WPB UD6022 UD4095 UD4101 UD6016 UD5004>>UD7001 UD4015*UD7010 WPS UD5014*UD5084.UD5079 AN3055*UD7083 UD6071 UD6035 WPS UD5082 UD4137*WA6001 WPS UD7013 UD6070 UD6076 AH3072*AH3114*AH3036*UD5093'WPB UD4032*WPB UD5061 WPB UD4118 WPS UD4107 WPB UD4099'WPB UD7079 UD4046 UD4102 UD7063'WPB UD4039*WPB UD4027*WPB UD4116*WPS I$5008*WPS UD4006*WPB UD5120 AH3Q'l4>>XH2087*UD6039 XH2025 UD5128 UD7075*UD4082 UD4051-UD5122 UD5005 UD4103 UD5057 AH3035*UD6026 UD4044 UD5069*UD5028*UD4098 UD6102 AH3056*UD5016*UD4040*UD5003 UD5018*UD4092 UD4028*UD7004 UD5077 Xk2073*UD6018 XH2065*1 2 16'17 18 4 5 6 19 20'1 22 8 9 10 11 23 24 25 26 12 13 27 28 14 29 15 30 1 XH2095*2 UD6066 3 XH2108*4 UD5068 5 UD7103 6 UD4093 7 UD4065.8 UD5116 9 UD5015 10 UD4119 11 UD5041 12 AH3007>>13 UD6020 14 UD4063 15 UD5112 16 UD5025*17 UO4080 18 UD61'16 19 AN3078*20 UD5037>>21 UO4035*22 UD5006 23 UD5002 24 UD4030*25 UD4049 26 UD7081 27 un5038*28 XN2060*29 UD6031'0 XH2052*16 AN3008*UD5083 WPS UD4055 WPS UD5044 WPS UD4126 WPB UD4129 WPB UD4120 WPS UD7033 UD4057 UD4084 UD7088 WPB UD4007*WPS uo4008*WPB UD4004>>WPB UD5096 WPB UD4002 WPB UD5059 AN3015*17 AN3095*UD6050 UD7027 WA6004 UD5115 UD6049 UD7077 UD5108 UD5045 UO7091 UD7105 UD6042 UD4070 WPS UD6074 UD6081 WPS UD4068 UD6009 UD7084 UD7097 UD5100 UD5107 UD7050 UD6005 UD5034" WA6002 UD7035 UD6091 AH3106*.18 AH3098*AH3021*UD6063 UD5052 WPB UD6019 UD4127 UD7067 WPS AN3090*UD6047 UD6010 AN3125*UD5109 UD5049 UD4073 WPS UD4124 UD4010 WPS UD5117 UD4001 UD4064 UD5051 UD6107 UD7032 UD4106 WPB AN3026*UD5074 AN3060*UO5022*UD4134*WPB UD6027 UD7100 UD4079 UD5024*UD5106 UD4036>>UD4013*WPB.WPB UD4037*UD5001 UD4090 AH3077" UD5104 UD6024 UD6082 WPB AH3105*UD4141*UD7052 WPB UD6090 uo6033 UD5032>>AN3110>>AH3024*19 20 AN3025*UD6065 UD4059 WPS UD7082 AN3089*UD7043 UD6064 UD 4130 WPB UD4123 WPS UD5053 WPS UD5012 UD5027 WPS uo5031*WPB UD4023*WPB UD 4133 UD6023 UD7055 AH3094*UD7026'WPB UD4074 UD6004 AN3062*AN3107*UD4058 WPS UD4105 WPS UD5073 WPS AN3027*WPS UD4020 WPS UD4019 UD7099 UD4050 UD4009 UD 4140*UD 4142*UD7056 UO4014*WPB uo4083*WPB AN3121*WPB UD5097 WPB UD 4132*WPS UD4085 AN3115*AH3096>>UD6119 XH2099>>UO6096 AH3028*WPS UO6046 UD5043 UD6101 UD5050 ,UD4109 UD5091 UD5046 UO6044 UD7025 AN3084*WPS" uo4031*Uo5118 UD5119 AH3081*UD5067 UD7022 UD4029*WPS UD5035*UD4125 UD5060 UD4003*UD4081'WPB UD5021*UD7016 UD5090 AN3023*UD4075 UD5033>>AH3016>>WPB UD6032 UD7096 UD5089 UD5088 UD5099 UD4136*UO5098 UD6007 WPS UD6083 UD6051 AN3117 UD6095-XH2078*AN3109*21-22 23 24 AN3126*AH3045*UO4147 AH3029*Ak3083*AN3134*UD6099 UD6040 UD5048 WPS AN3085>>UD7018 LYV155 WPS UD6011 AN3103*UD6045 WPB UD6104 UD5113 UD5013*WPB UD4056 UD7102 UD4139", UD7066 UD5136'WPB UD6006 UD5105 UD6093 WPB UD6118 AN3111*LYV154 WPB AN3093*UD7058 UD5029*WPB UD6003 UD6084 AH3059*AH3065*UD4148 AN3047" AN3108*AN3017*25 26 AN3119*AN3130*AH3124*XN2094*UD6097 UD6109 WPB UD4096 UD4022*WPB UD7040 UD6048 UD4066'WPB UD5133 UD7094 UD4069 WPS UD5114 XH1090 UD5101 XH1141 UD4067 WPS UD5092 UD7057 UD4086'MPS UD7106 UD6085 UD4060 WPS WPS UD4089 UD6086 l$6089 AN3129*XN2068*AH3005*AN3006*27 28 Ak3022*UD6043 UD4110 UD5047 UD6025 UD 6106 UD 5110 UD6098 UD6030 UD5026>>UD6008 UD6088-UD5023*UD 4135*UD6092 AH3061*AN3030*AN3097>>AH3049*AH3120*AN3082*AN3001*XN2067*XH2100*AH3122*AN3112*AH3063*AN3091*AH3116*AH3048*30 WPS are fresh 9x9-9X assemblies loaded in Cycle 9>>Assemblies with Reused Channels
UNITED STATES NUCLEAR REGULATORY COMMISSION OFFICE OF NUCLEAR REACTOR REGULATION WASHINGTON, D.C.20555 November 10, 1992 NRC INFORMATION NOTICE 92-74: POWER OSCILLAT 8NS AT WASHINGTON NUCLEAR POWER~'NIT,.2 Addressees All holders of operating licenses or construction permits for boiling-water reactors (BWRs).~Pur ose The U.S.Nuclear Regulatory Commission (NRC)is issuing this information notice to alert addressees to a recent event involving power oscillations in an operating region where instability had not been specifically predicted.
It is expected that recipients'will review the information for applicability to their facilities and consider actions, as appropriate, to avoid similar problems.However, suggestions contained in this information notice are not NRC requirements; therefore, no specific action or written response is required.~Back round On March 9, 1988, a thermal hydraulic instability event occurred at LaSalle Unit 2.The NRC discussed this event in Information Notice 88-39,"LaSalle Unit 2 Loss of Recirculation Pumps with Power Oscillation Event," and Bulletins 88-07 and 88-07, Supplement 1,"Power Oscillations in Boiling Water Reactors." In the first bulletin, the NRC requested licensees to establish procedures and give training to reactor operators to enable them to recognize oscillations and to take appropriate actions.In the supplement, the NRC requested licensees.
to implement the General Electric (GE)Interim Recommendations for Stability Actions, designated the Interim Corrective Actions (ICA).GE defined the exclusion regions on the power/flow map in which, with varying probability, instability might be expected.Three regions were defined in which operation was to be avoided (immediate exit if entered)or limited (e.g., when required during startup).These regions were based on'operating or test experience for reactors with GE fuel.The exclusion regions for new fuel designs were to be reevaluated and justified based on any applicable operating experience, calculated changes in core decay ratio using NRC-approved methodology, and/or core decay ratio measurements.
Since.the LaSalle event in 1988, the NRC and the BWR Owners'roup (BWROG)have conducted extensive analyses and reviews of various aspects of stability while developing long-term solutions to augment or replace the ICA.On March 18, 1992, the BWROG sent a letter (BWROG-92030) to BWROG members 9211040206 IN 92-74 November 10, 1992 Page 2 of 5 transmitting"Implementation Guidance for Stability Interim Corrective Actions." In this letter, the BWROG emphasized the need for caution when operating near the exclusion regions.The BWROG also recommended reexamining procedures and training to reflect uncertainties in the definition of exclusion region boundaries.
'l~Descri tion of Circumstances
~g On August 15, 1992, Washington Nuclear Power Unit 2 (WNP-2)experienced power oscillations during startup.The event occurred early in cycle 8 operation.
During, cycle, 8, the licensee had two previous startups without incident.The reactor core consisted primarily of Siemens fuel, with about 74 percent of this fuel in 8x8 fuel assemblies and about 25 percent in 9x9 fuel assemblies,.and with the remainder of the core consisting of various lead test assemblies.
The 9x9 fuel assembly used in WNP-2, designated 9x9-9x, has a higher flow-resistance-than the 8x8 fuel assembly with a difference of about 10 percent in pressure drop..These 9x9 fuel assemblies were loaded during cycles 7 and 8.J About 33 hours3.819444e-4 days <br />0.00917 hours <br />5.456349e-5 weeks <br />1.25565e-5 months <br /> before the event, the licensee commenced a controlled power reduction from full power to 5-percent power to repair a valve packing leak in the drywell.After completing the repairs, the licensee began'a return to full power: The licensee increased reactor power to about 34 percent and then held it at that level for 3 hours3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br /> to perform turbine bypass valve tests and control rod drive system timing tests.The recirculation syst'm was operated with flow control valves (FCVs)full open and pumps at slow speed.After completing the tests, the operators continued the restart up the (approximately) 30-percent flow line to about 36-percent power (Figure 1).This is at a power above the recirculation pump cavitation region.The operators then began closing one of the two FCVs in preparation for shifting the associated recirculation pump to fast speed.During this change, in which power and flow decreased along the 76-percent rod.line to a power/flow of about 34/27 percent, the operators observed power oscillations first on the average power range monitors (APRHs)and then by local power range monitors (LPRHs)downscale indications.
Upon recognizing the power oscillations, the plant operators manually initiated a reactor scram.Post-event review indicated that the 2-second-period oscillations were in-phase (core-wide) and had grown to a peak-to-peak ampl'itude of about 25 percent of rated power.Host of the oscillation amplitude'iricrease occurred in an interval of about 1 minute with the oscillations continuing at the limiting (maximum)amplitude for an additional minute before scram.The,oscillations occurred while the reactor was operating at a power about 4'percent of rated power below the lower.exclusion region boundary line (the nominal 80-percent rod line).During later review, the licensee found no indication that fuel had failed because of the event.
IN 92-74 November 10, 1992 Page 3-'of 5 The NRC sent an Augmented Inspection Team (AIT)to the site to determine the possible causes and relevant facts of this event.The AIT concluded that the primary cause of the oscillations was very skewed radial and bottom peaked axial power distributions in the reactor (1.92 radial peaking factor and 1.62 core average axial peaking factor).These power distributions resulted from (1)the control rod pattern that the shift technical advisor selected for increasing the power and shifting the recirculation pump, speed, and (2)the relationship of this control rod pattern to the specific WNP-2 cycle 8 core fuel loading configuration.
These rod patterns were primarily directed towards achieving the target full power configuration and did not consider stability concerns.The AIT also found, by analyses using the LAPUR code, that a contributor to the oscillations was the core loading, consisting of a mixed core with unbalanced flow characteristics between the new 9x9-9x fuel and the old 8x8 fuel: The analyses indicated that a full core of the 9x9-9x fuel would be significantly less stable than the old 8x8 fuel, and that the mixed.core was.less stable'than a fully loaded core of either fuel type.The analyses also indicated that while the oscillations would be in-phase (core-wide), as observed in the event, the out-of-phase (regional) instability boundary would be very close to the in-phase boundary (Figure 1).The AIT found that small changes in operating conditions could have resulted in out-of-phase oscillations, which would have been more difficult for the APRH system to detect.WNP-2 has a Siemens Advanced Neutron Noise Analysis (ANNA)monitor, a stability monitor required by technical specifications only if the licensee intends to enter the lower exclusion region.Since the licensee did not intend to enter the exclusion region during this startup, the ANNA monitor was not put into the observation mode, although it was gathering data which was used later to confirm stability calculations performed after the event.The licensee successfully restarted the unit after implementing the following restrictions for maintaining the limits on rod withdrawal patterns and power distribution in the low flow regions of concern.0 The licensee analyzed the control rod patterns for stability before startup, and the operator could not.change these patterns without analysis and review.The calculated maximum total peaking factor.was less than 3.4.
IN 92-74 November 10, 1992 Page 4 of 5 The calculated core average axial peaking factor was less than 1.45.~The Hinimum Critical Power Ratio was greater than 2.2.The licensee analyzed the conditions at FCV closure and found a decay ratio of less than 0.5.The recirculation pump was shifted to fast speed with the reactor power less than 33 percent and the feedwater temperature greater than 146.I'C-(295'F).The licensee continuously used the ANNA monitor when the reactor was operating above 25 percent power and below 50 percent flow.Further detailed description of the event can be found in the AIT Inspection Report No.50-397/92-30.
Discussion The WNP-2 power oscillation event indicates that the boundaries of the ICA regions, or modifications approved for various reactor technical specifications, do not necessarily encompass all stability limits Instability may occur beyond these boundaries if the reactor is operated with configurations outside those used to define the boundaries.
This event presented direct evidence that the following factors can be significant contributors to the possibility of unstable operation.
Power distributions involving extremely skewed radial and axial peaking factors can induce unstable operation even in regions or with operating conditions not otherwise considered susceptible to oscillations.
Core loading patterns involving a mixture of fuel types with differing flow resistances can contribute to instability.
0 Reactors with two-speed recirculation pumps and FCVs can hinder stability because of the narrow range of operation between pump cavitation regions and possible instability regions.The event also indicates the value of operating a stability monitor.The ANNA monitor could have given the operators information that instability was iqminent, prompting them to alter operations to avoid the oscillations.
IN 92-74'November 10, 1992 Page 5,of 5 This information notice requires no specific action or written response.If you have any questions about the information in this notice, please contact one of the technical contacts listed below or the appropriate Office of Nuclear Reactor Regulation (NRR)project manager.II~Brian K.Grimes, Director Division of Operating.
Reactors Support Office of Nuclear Reactor Regulation Technical contacts: Howard Richings, NRR (301)504-2888 Peter C.Wen, NRR (301)504-2832 Attachments:
1.Figure 1.Best-Estimate Lines of Constant Decay Ratio=l.0 for Actual Conditions of WNP-2 8/15/1992 Event, Assuming Constant Power Distribution 2.List of Recently Issued NRC Information Notices Attachment 1 IN 92-74 November 10, 1992 Page 1 of 1 WNP-2 8/15 STARTUP CONDITIONS LAPUR-consta est i ma%nt out-ed lin of-pha e of se DR=70 60 100$rod line+50 45 40~sos rod line:----t APU¹est-i.constant in maCeci--I-'I-ne--of-
-phase DR=1 6%rod one 25 20 20 25 30 35 40 45 Core Flow ($of Rated)55 60 Figure L,, Best-estimate lines of constant decay ratio 1.0 for actual conditions of 8/15 event, assuming constant power distribution Attachment 2 IN 92-74 November 10, 1992 Page 1 of 1 LIST OF RECENTLY ISSUED NRC INFORMATION NOTICES n ormatlon Notice No.Subject ate o Issuance Issued to 92-61, Supp.1 92-73 Loss of High Head Safety Injection Removal of A Fuel Element from A Re-search Reactor Core While Critical 11/06/92 11-04/92 All holders of OLs or CPs for nuclear power reactors.All holders of OLs or CPs for nuclear power reactors.92-59, Rev.1 Horizontally-Installed Motor-Operated Gate Valves 11/04/92-All holders of OLs or CPs for nuclear power reactors.92-72 Employee Training and Shipper Registration Requirements for Trans-porting Radioactive Materials 10/28/92 All U.S.Nuclear Regulatory Commission Licensees.
91-64, Supp.1 92-71 Site Area Emergency Resulting from A Loss of Non-Class lE Uninterruptible Power Supplies Partial Plugging of Suppression Pool Strainers At A Foreign BWR 10/07/92 09/30/92 All holders of OLs or CPs for nuclear power reactors.All holders of OLs or CPs for nuclear.power reactors: 92-70 Westinghouse Motor-Operated 09/25/92 Valve Performance Data Supplied to Nuclear Power Plant Licensees All holders of OLs or CPs for nuclear power reactors.92-69 91-'29, Supp.1 Water Leakage from Yard Area Through Conduits Into Buildings Deficiencies Identified During Electrical Dis-tribution System Func-tional Inspections 09/22/92 09/14/92 All holders of OLs or CPs for nuclear power reactors.All holders of OLs or CPs for nuclear power reactors.perat>ng 1cense CP=Construction Permit UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C.20555-0001 FIRST CLASS MAIL POSTAGE AND FEES PAID USNRC PERMIT NO.G-67 OFFICIAL BUSINESS PENALTY FOR PRIVATE USE,$300.120555, p pg9-56 I US fgR CO I R-g=.l...1.C.O I CY1FB11$1.CH IE'F".OI V...OF INFO SUP SVCS u~F-P'=r'*-""'"'"""'-'"--'---
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