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 DOCKET N FACIL:50-397 WPPSS Nuclear Project, Unit 2, Washington Public Powe 05000397 AUTH. NAME AUTHOR AFFILIATION
, SORENSEN,G.C. Washington Public Power Supply System RECIP.NAME RECIPIENT AFFILIATION Document Contxol Branch (Document Control Desk)
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 COPIES RECIPIENT COPIES ID CODE/NAME LTTR ENCL ID CODE/NAME LTTR ENCL
. PD5 LA 1 0 PD5 PD 1 1 CLIFFORDF J 1 1 INTERNAL: AEOD/DOA 1 1 AEOD/DSP/TPAB 1 -1 NRR FIENO,D 1 1 NRR LONGFW PD31 1 1 NRR/DET/EMEB 7E 1 1 NRR/DOEA/OEAB11 1 1 NRR/DOEA/OGCBll 1 1 NRR/DREP/PEPB9D 1 1 NRR/Dggf 8E2 1 1 NRR/PMAS/ILRB12 1 1 GREG FILED 02 1 1 RES/DSIR/EIB 1 1 RGN5 FILE 01 1 1 EXTERNAL: NRC PDR 1 1 NSIC 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 ELIMINATEYOUR 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 BULLETINNO. 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 of WNP-2 Cycle 6 Reload Submittal and Response to NRC USNRC,'Modification 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 9302020500039'7 PDR ADOCK PDR
Page Two RESPONSE TO NRC BULLETINNO. 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.
~d/
EXPOSURE RANGE UANTITY 27 - 34 42-34 - 41 42 41-48 148
Page Three
~ ~
RESPONSE TO NRC BULLETINNO. 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 BULLETINNO. 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; Table 1; Reused Channels, Assemblies And Projected Exposure
- 2. 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 )
Subject:
Res onse to IEB 90-02
)
COUNTY OF BENTON )
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
Table 1 I
Reused Channels, Assemblies', and Projected EOC 9 Exposures Current Proj. EOC 9 Row Column Assembly Channel ID Exposure 1 9 AN3042 71970 46918 1 10 AN3075 73079 47612 1 11 AN3033 73130 46740'7193 1 12 AN3067 61769 1 13 AN3066 73366 44038 1 14 AN3036 63602 44649 1 15 XN2087 71965 39247 1 16,, XN2095 70104 39371 1 17 AN3008 71758 44586 1 18 AN3095 5938D 37527 1 19 AN3098 5900D 38424 1 20 AN3021 71458 46740 1 21 AN3107 71808 44849 1 22 AN3025 63257 46819 2 8 AN3068 70287 45588 2 23 AN3096 70257 45296 3 6 AN3040 73367 44748
- 3. 7 XN2091 71387 36125 3 9, UD4034 72009 41880 3 16 XN2108 73379 40563 3 24 XN2099 61638 42632 3 25 AN3126 71933 47186 4 6 AN3099 71956 47126 4 7 AN3064 72035 41718 4 10 UD4115 70190 30912 4 14 UD4032 62686 30303 4 24 AN3028 72474 41533 4 25 AN3045 71914 47621 5 5 AN3031 71389 44510 5 11 AN3074 73425 47607 5 13 UD5066 71780 43637 5 20 AN3090'N3029 73390 47681 5 26 72439 43969 6 3 AN3038 71756 47099 6 4 AN3051 63949 47120 6 5 AN3133 71927 45963 6 6 AN3043 6450D 37847 6 8 UD5071 71938 37852 6 9 AN3092 63572 44270 6 10 UD5064 71198 45818 6 22 AN3089 62513 44359 6 25 AN3083 71809 46523 6 26 AN3134 73384 45177 6 27 AN3119 63442 47161
Table 1 (Cont.)
Current Proj . EOC 9 Row Column Assembly Channel ID Exposure 6 28 AN3130 6012D 35556 7 3 XN2086 71300 36550 7 8 UD5070 71945 45874 7 12 AN3039 71789 45729 7 19 AN3125 71755 45584 7 27 AN3124 71376 41594 7 28 XN2094 71761 35989 8 2 AN3034 71757 45307 8 8 UD5072 70238 46115 8 10 AN3070 5881D 37854 8 11 UD4025 70279 43736 8 12 UD5063 71817 44770 8 21 AN3027 71437 46213 8 29 AN3022 72027 47311 9 1 AN3032 71942 43959 9 6 AN3104 72039 47033 9 25 AN3085 73394 46329 9 30 AN3030- 71443 44097 10 1 AN3076 5809D 39001 10 4 UD4024 73124 31375 10 8 AN3079 63445 46813 10 23 AN3084 71391 47052 10 27 UD4022 73386 37823 10 30 AN3097 71400 47663 11 1 AN3100 73120 46830 11 5 AN3053 5898D 39081 11 23 UD4031 72038 44572 11 26 AN3103 73154 39070 11 30 AN3049 72024 46828 12 1 AN3052 71958 46391 12 7 AN3069 73116 46028 12 15 AN3035 71986 45280 12 16 AN3007 5960D 36559 12 24 AN3081 73111 37074 12 30 AN3120 73226 46857 13 1 AN3054 63427 45912 13 8 UD5065 61550 40884 13 30 AN3082 71447 34336 14 1 AN3080 5866D 36350 14 23 UD4029 73117 30712 14 25 UD5013 70110 46305 14 30 AN3001 71790 45294 15 1 XN2084 71936 39297 15 8 UD5030 71848 45400 15 12 AN3041 73108 44889 15 15 UD5069 63492 46029
Table 1 (Cont.)
Current Proj. EOC 9 Row Column Assembly 'Channel ID Exposure I
,, 15 19 AN3026 72001 45348 15 23 UD5035 71983 45006
., 15 30 XN2067 73582 39887 16 1 = XN2066 61972 33095 16 4 "UD5040 62522 43137 16 6 UD4016 71904 32845 16 7- UD4021 73232 47418 16 10 UD4143 72042 32464 16 11 UD5036 73238 42577 16 12 AN3020 63956 45756 16 15 UD5028 71962 45397 16 16 UD5025 71141 46076 16 19 AN3060 71268 45592 16 20 UD5022 70252 42717 16 21 UD4140 71801 29988 16 24 UD4003 63953 47417 16 25 UD4139 73132 30540 16 30 XN2100 71959 33173 17 1 AN3002 62283 36432 17 10 ~ UD4144 71434 30213 17 12 -UD4012 71950 33116 17 .
19 UD4134 70167 30230 17 21 UD4142 6028D 36462 17 29 UDS026 61750 42583 17 30 AN3122 71928 42349 18 1' AN3058 73388 45791 18 UD5039 70011 43890 18 22 UD5031 73415 43998 18 23 '
UD5021 71799 43411 18 30 AN3112 71990 45473 19 AN3019 71852 47231 19 10 UD4005 73089 33984 19 11, UD5010 72034 44953 19 14 UD4039 71835 32198 19 15 AN3056 61741 45434 19 16 AN3078 71967 45621 19 17 UD4007 73426 31688 19 20 UD5024 61529 44728 19 21 UD4014 72018 29767 19 24 AN3023 5850D 37057 19 30 AN3063 62937 47021 20 1 AN3086 70047 44381 20 5 AN3057 5802D- 39070 20 71795 30131-20 20 ll 9
12 UD4033 UD4041 UDS004 71923 71908 33693 45676
Table 1 (Cont. )
Current Proj . EOC 9 Row Column Assembly Channel ID Exposure 20 15 UD5016 71356 42790 20 16 UD5037 71830 42962 20 20 UD4036 73441 34195 20 22 UD4023 73614 39187 20 24 UD5033 70158 45086 20 26 AN3111 73135 47628 20 29 UD5023 73069 42591 20 30 AN3091 73112 46828 21 1 AN3073 72036 47663 21 2 UD4042 71943 46205 21 8 AN3128 72021 47002 21 10 UD4038 73403 31013 21 12 UD4015 5912D 34227 21 14 UD4027 71393 30450 21 15 UD4040 71786 32216 21 16 UD4035 71957 47804 21 17 UD4008 71907 30224 21 19 UD4013 71770 27878 21 21 UD4083 71953 31549 21 23 AN3016 71448 46513 21 29 UD4135 71975 43694 21 30 AN3116 63947 47633 22 1 AN3123 71991 46059 22 6 AN3050 71449 35546 22 11 UD4026 71778 30170 22 13 UD5014 71759 44377 2.2 20 UD4037 61931 31023 22 25 "AN3093 73420 47024 22 30 AN3048 70272 43959 23 AN3011 60890 48146 23,8 UD5011 71930 45838 23 10 AN3131 72041 46552 23 14 UD4116 71392 31006 23 15 UD5018 61538 45268 23 17 UD4004 73444 38303 23 21 AN3121 71444 46808 23 25 UD5029 61773 44513 23 29 AN3061 73399 47943 24 3 XN2056 72023 42227 24 4 AN3037 72037 41502 24 7 UD4138 71334 30007 24 8 UD5017 63943 45859 24 11 UD5009 71913 45563 24 12 AN3055 73171 46086 24 16 UD4030 71308 47347 24 19 AN3077 71812 45669
Table 1 (Cont.)
Current Proj . EOC, 9 Row Column Assembly Channel lD Exposure
'24 24 UD4 13 6 70103 30045 24 27 AN3129 71442 41286 ~
24 28 XN2068 61682 42817 25 4 AN3013 71838 47089 25 5 AN3102 71753 36910 25 6 AN3012 5999D 37819 25 8 UD5020 71791 44261 25 9 AN3088 5905D 35518 25 14 UD5008 71377 46817 25 15- UD4028 73368 30426 25 22 AN3094 5852D 38237
'25 25 AN3059 5868D 35158 25 26 AN3065 71976 39663.
25 27 AN3005 73 15'3 47029 25 28 AN3006 71912 47221.
26 5 AN3044 73422 44510 61578 47363
'1 26 AN3087 26 18 UD5034 71771 44582 26 20 AN3105 70206 47141 26 26 AN3047 73133 41869 ~
27 6 AN3101 61523 47454
'27 7 AN3018 71431 41309 27 10 UD4011 71792 30625 27 12 UD4137 62501 30375 27 14 UD4006 71954 31509 27 16 UD5038 71960 43 602.
27 19 UD4141 71369 30376 27 .21 UD4132 63950 ,30900 27 25 AN3108 71994 47321 28 7 XN2081 71390 36125 28 15 XN2073 71964 40563 28 16 XN2060 73416 33610.
28 24 XN2078 61673- 42327 28 25 AN3017 73139 47186 29 20 UD5032 70243 42458 29 23 AN3109 73121 47750 30 9 AN3127 70102 46819 AN3071 73131 35907 30 30
,30 ll 10 12 AN3132 AN3072 71981 71788.
46882 47029 30 13 AN3114 5805D 34826 30 14 AN3014 71985 44707 30 15 XN2065 71921 32884 .
30 16 XN2052 61526 32863 30 17 AN3015 72014 44802 30 18 AN3106 5932D -
37651
Table 1 (Cont.)
Current Proj . -EOC 9 Row Column Assembly Channel ID Exposure 30 19 AN3110 71773 46884 30 20 AN3024 71445 47032 30 21 AN3115 73227 47512 30 22 AN3062 71890 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 AH3042* AH3075>> AH3033* Ak3067* AH3066* AH3036* XH2087*
2 AN3068* uo6038 UD4018 UD5124 UD6069 UD6059 UD5093 UD6039 3 AN3040* XH2091* uo6113 uo4034* WPB UD6068 WPB UD7030 'WPB XH2025 4 AN3099* AN3064* UD6075 WPB UD4115* UD7095 UD4114 WA6003 UD4032* UD5128
- 5.' AH3031>> UD4146 UD6054 MPB UD7078 WPB AH3074* 'WPB UD5066* WPB UD7075 AN3038* AH3051* AH3133* AH3043* UD6120 UD5071* AH3092* uo5o64>> uo6os7 UD6013 UD6028 UD5061 UD4082 7 XN2086>> AN3046 UD6056 UD6112 UD4112 UD5070* UD7021 WPB UD5058 AN3039* UD7064 WPB UD4051-8 AH3034* UD6058 UD6053 WPB UD5129 UD 5135 UD5072>> UD6061 AH3070>> UD4025* UD5063* UD5125 UD4118 UD5122 9 AH3032* UD6052 . UD4122 WPB UD7024 AN3104* UD7089 UD6062 UD4128 WPS UD4108 WPB UD5062 WPS UD5005 10 AN3076>> UD41'11 'MPS UD4024>> WPS LYV153 WPS AN3079* WPS UD4045 WPS UD4048 UD7087 UD4107 UD4103 11 AH3100* UD 5121 UD6041 UD7005 AH3053* UD6037 UD5126 UD4121 UD4117 WPS UD4100 UD5131 UD7093 WPB UD5057 12 AH3052* UD6057 WPS UD4017 WPS UD6060 Ak3069* UD5132 'WPS UD4047 UD5123 UO4043 UD6108 UD4099 AH3035*
- 13. AH3054* UD6114 UD7068 UD511'I UD 5127 UD6036 UD7090 UD5065* uo5055 UD7020 UD7023 UD6103 UD4053 'WPB UD6026 14 AN3080* UD5054 WPS UD4054 WPS UD5087 WPS UD4052 WPB UD4113 WPB UD4104 WPB UD7079 UD4044 15 XH2084>> UO6115 XH2024 UD 5130 UD 7019 UD4062 UD4088 UD5030* UO5007 UD4061 UD5056 AN3041* UD6094 UD4046 UD5069*
16 XN2066>> UD6002 XH2071 UD5040* UD 7011 UD 4016* UD4021>> UD5042 UD5019 UO4143>> un5036* AH3020* UD6117 UD4102 UD5028*
17 AN3002" UD5075 WPB UD4097 WPS UD 5134 WPB UD4091 'WPS UD4144>> WPS UD4012* WPB UD7063 UD4098 18 AN3058* UD6012 UD7053 UD5086 UD5080 UD6034 UD7072 UD5095 UD5039* UD7062 UD7047 UD6022 UD4095 'WPB UD6102 19 AN3019* UD6078 WPB UD4077 WPS UD6080 AN3010 UD5103 WPB UO4005* UD5010* UD4101 UD6016 UD4039* AH3056*
20 AN3086* UD5085 UD 6015 l$ 7031 AH3057* UD6100 UD5094 UO4072 UD4033* WPB UO4041* UD5004>> UD7001 WPB UD5016*
21 AH3073* UD4042* WPB UD4076 WPB LYV156 WPB AH3128* 'WPS UD4038* WPB UD4015* UD7010 UD4027* UD4040*
22 AH3123* UD6079 UD4071 WPB UD7065 AN3050* UD7046 UD6021 UD4131 'WPB UD4026* WPS UD5014* WPB UD5003 23 AN3011* UD6077 UD6110 WPS UD5078 UD5102 UD5011* UD6029 AH3131* UD4087 UD5084 . UD5079 UD4116* UD5018*
24 XH2056* AH3037* UD6072 UD6001 un4138* UD5017* UD7060 'WPB UD5009* AN3055* UD7083 WPS UD4092 25 AN3009 AN3013* AH3102* AN3012>> UD6017 UD5020* AN3088* UD5076 UD6105 UD6071 UD6035 I$ 5008* UD4028*
26 AH3044* UD4145 UD6067 WPS UD7080 WPS AN30S7* WPS UD5082 WPS UD7004 27 AH3101* AN3018* UD6111 WPB UD4011* UD7054 UD4137* WA6001 UD4006* UD5077 28 AN3118 XH2081* UD6073 UD4094 WPS UD6055 WPS UD7013 WPB Xk2073*
29 AN3113 UD6014 UD4078 UD5081 UD6070 UD6076 UD5120 UD6018 30 AH3127" AH3071* AH3132* AH3072* AH3114* AH3Q'l4>> XH2065*
1 2 4 5 6 8 9 10 11 12 13 14 15 16 '17 18 19 20 '1 22 23 24 25 26 27 28 29 30 1 XH2095* AN3008* AN3095* AH3098* AH3021* AN3107* AN3025*
2 UD6066 UD5083 UD6050 UD6063 UD5052 UD4058 UD6065 AH3096>>
3 XH2108* WPS UD7027 WPB UD6019 WPS UD4059 UD6119 XH2099>> AN3126*
4 UD5068 UD4055 WA6004 UD4127 UD7067 UD4105 WPS UO6096 AH3028* AH3045*
5 UD7103 WPS UD5115 WPS AN3090* WPS UD7082 WPS UO6046 UO4147 AH3029*
6 UD4093 UD5044 UD6049 UD6047 UD6010 UD5073 AN3089* UD5043 UD6101 Ak3083* AN3134* AN3119* AN3130*
7 UD4065. WPS UD7077 AN3125* UD5109 WPS UD7043 UD5050 ,UD4109 UD6099 UD6040 AH3124* XN2094*
8 UD5116 UD4126 UD5108 UD5049 UD4073 AN3027* UD6064 UD5091 UD5046 UD5048 WPS UD6097 UD6109 Ak3022*
9 UD5015 WPB UD5045 WPS UD4124 WPS UD 4130 UO6044 UD7025 AN3085>> UD7018 WPB UD4096 UD6043 AN3030*
10 UD4119 UD4129 UO7091 UD4010 WPS UD4020 WPB AN3084* WPS " LYV155 WPS UD4022* WPB UD4110 AN3097>>
11 UD5041 WPB UD7105 UD5117 UD4001 WPS UD4123 uo4031* Uo5118 UD6011 AN3103* UD7040 UD6048 UD5047 AH3049*
12 AH3007>> UD4120 UD6042 UD4064 UD5051 UD4019 WPS UD5119 AH3081* UD6045 WPB UD4066 'WPB UD6025 AH3120*
13 UD6020 WPS UD4070 UD6107 UD7032 UD7099 UD5053 UD5067 UD7022 UD6104 UD5113 UD5133 UD7094 UD 6106 AN3082*
14 UD4063 UD7033 WPS UD4106 WPB UD4050 WPS UD4029* WPS UD5013* WPB UD4069 WPS UD 5110 AN3001*
15 UD5112 UD4057 UD6074 AN3026* UD5074 UD4009 UD5012 UD5035* UD4125 UD4056 UD7102 UD5114 XH1090 UD6098 XN2067*
16 UD5025* UD4084 UD6081 AN3060* UO5022* UD 4140* UD5027 UD5060 UD4003* UD4139", UD7066 UD5101 XH1141 UD6030 XH2100*
17 UO4080 UD7088 WPS UD4134* WPB UD 4142* WPS UD4081 'WPB UD5136 'WPB UD4067 WPS UD5026>> AH3122*
18 UD61'16 WPB UD4068 UD6027 UD7100 UD7056 uo5031* UD5021* UD7016 UD6006 UD5105 UD5092 UD7057 UD6008 AN3112*
19 AN3078* UD4007* UD6009 UD4079 UD5024* UO4014* WPB UD5090 AN3023* UD6093 WPB UD4086 'MPS UD6088- AH3063*
20 UD5037>> WPS UD7084 UD5106 UD4036>> WPB UD4023* UD4075 UD5033>> UD6118 AN3111* UD7106 UD6085 UD5023* AN3091*
21 UO4035* uo4008* UD7097 UD4013* WPB. uo4083* WPB AH3016>> WPB LYV154 WPB UD4060 WPS UD 4135* AH3116*
22 UD5006 WPB UD5100 WPB UD4037* WPB UD 4133 UD6032 UD7096 AN3093* UD7058 WPS UD4089 UD6092 AH3048*
23 UD5002 UD4004>> UD5107 UD5001 UD4090 AN3121* UD6023 UD5089 UD5088 UD5029* WPB UD6086 l$ 6089 AH3061*
24 UD4030* WPB UD7050 AH3077" UD5104 WPB UD7055 UD5099 UD4136* UD6003 UD6084 AN3129* XN2068*
25 UD4049 UD5096 UD6005 UD6024 UD6082 UD5097 AH3094* UO5098 UD6007 AH3059* AH3065* AH3005* AN3006*
26 UD7081 WPB UD5034" WPB AH3105* WPB UD7026 WPS UD6083 UD4148 AN3047" 27 un5038* UD4002 WA6002 UD4141* UD7052 UD 4132* 'WPB UD6051 AN3117 AN3108*
28 XN2060* WPB UD7035 WPB UD6090 WPS UD4074 UD6095 - XH2078* AN3017*
29 UD6031 UD5059 UD6091 uo6033 UD5032>> UD4085 UD6004 AN3109*
'0 XH2052* AN3015* AH3106*. AN3110>> AH3024* AN3115* AN3062*
16 17 18 19 20 21 -22 23 24 25 26 27 28 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.
The licensee analyzed the control rod patterns for stability before startup, and the operator could not.change these patterns without analysis and review.
0 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.
'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-est i ma% ed line of consta nt out- of-pha se DR=
70 60 100$ rod line 50
~
+
sos rod line 45 40 :----t APU¹ est-i. maCeci-- I-'I-ne--of-constant in phase DR=1 6% rod one 25 20 20 25 30 35 40 45 55 60 Core Flow ( $ of Rated )
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 ate o Notice No. Subject Issuance Issued to 92-61, Loss of High Head 11/06/92 All holders of OLs or CPs Supp. 1 Safety Injection for nuclear power reactors.
92-73 Removal of A Fuel 11-04/92 All holders of OLs or CPs Element from A Re- for nuclear power reactors.
search Reactor Core While Critical 92-59, Horizontally-Installed 11/04/92 -
All holders of OLs or CPs Rev. 1 Motor-Operated Gate for nuclear power reactors.
Valves 92-72 Employee Training and 10/28/92 All U.S. Nuclear Regulatory Shipper Registration Commission Licensees.
Requirements for Trans-porting Radioactive Materials 91-64, Site Area Emergency 10/07/92 All holders of OLs or CPs Supp. 1 Resulting from A Loss for nuclear power reactors.
of Non-Class lE Uninterruptible Power Supplies 92-71 Partial Plugging of 09/30/92 All holders of OLs or CPs Suppression Pool for nuclear. power reactors:
Strainers At A Foreign BWR 92-70 Westinghouse Motor-Operated 09/25/92 All holders of OLs or CPs Valve Performance Data for nuclear power reactors.
Supplied to Nuclear Power Plant Licensees 92-69 Water Leakage from Yard 09/22/92 All holders of OLs or CPs Area Through Conduits for nuclear power reactors.
Into Buildings 91-'29, Deficiencies Identified 09/14/92 All holders of OLs or CPs Supp. 1 During Electrical Dis- for nuclear power reactors.
tribution System Func-tional Inspections perat>ng 1cense CP = Construction Permit
UNITED STATES FIRST CLASS MAIL NUCLEAR REGULATORY COMMISSION POSTAGE AND FEES PAID WASHINGTON, D.C. 20555-0001 USNRC PERMIT NO. G-67 OFFICIAL BUSINESS PENALTY FOR PRIVATE USE, $ 300
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