ML17290B189

Responds to NRC Bulletin 90-002, Loss of Thermal Margin Caused by Channel Box Bow, Which Responds to Questions on Cycle 10 Operation

ML17290B189
Person / Time
Site:	Columbia
Issue date:	05/20/1994
From:	Parrish J WASHINGTON PUBLIC POWER SUPPLY SYSTEM
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
GO2-94-123, IEB-90-002, IEB-90-2, NUDOCS 9405270121
Download: ML17290B189 (5)

Text

ACCELERATED DIy~RIBUTION DEMONSTRATION SYSTEM REGULATORY INFORMATION DISTRIBUTXON SYSTEM (RXDS)

ACCESSION NBR:9405270121 DOC.DATE: 94/05/20 NOTARIZED: NO DOCKET FACIL:50-397 WPPSS Nuclear Project, Unit 2, Washington Public Powe 05000397 AUTH. NAME . AUTHOR AFFILIATION PARRISH,J.V. Washington Public Power Supply System RECIP.NAME RECIPXENT AFFILIATION Document Control Branch {Document Control Desk)

SUBJECT:

Responds to NRC Bulletin 90-002, "Loss of Thermal Margin Caused By Channel Box Bow," which responds to questions on Cycle 10 Operation.

D DISTRIBUTION CODE: IE11D COPIES RECEIVED:LTR ENCL SIZE:

TITLE: Bulletin Response (50 DKT)

NOTES:

RECIPIENT COPIES RECIPIENT COPIES ID CODE/NAME LTTR ENCL ID CODE/NAME LTTR ENCL PDIV-3 PD 1 1 CLIFFORD,J 1 1 INTERNAL: AEOD/DOA 1 1, NRR/DE/EMEB 1 1 NRR/DORS/OGCB 1 1 NRR/DRPW 1 1 NRR/DRSS/PEPB 1. 1 NRR/DSSA 1 1 NRR/DSSA/SRXB 1 1 1 1 NRR/SCSB 1 1 1 1 RES/DSIR/EIB 1 1 1 1 EXTERNAL: NRC PDR 1 1 NSIC 1 1 D

D D

NOTE TO ALL "RIDS" RECIPIENTS:

PLEASE HELP US TO REDUCE KYASTE! CONTACf THE DOCUMENT CONTROL DESK, ROOM Pl-37 {EXT. 20079) TO ELIMINATEYOUR NAME FROM DISTRIBUTION LISTS FOR DOCUMENTS YOU DON'T NEED!

TOTAL NUMBER OF COPIES REQUIRED: LTTR 16 ENCL 16

WASHINGTON PUBLIC POWER SUPPLY SYSTEM P.O. Box 968 ~ 3000 George 1Vasblngton 1Vay ~ Rtcbland, 1Vasbtngton 99352-0968 ~ (509) 372-5000 May 20, 1994 G02-94-123 Docket No. 50-397 U.S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, D.C. 20555

Subject:

WNP-2, OPERATING LICENSE NPF-21 RESPONSE TO NRC BULLETIN90-02: "LOSS OF THERMALMARGIN CAUSED BY CHANNEL BOX BOW," RESPONSE TO QUESTIONS ON CYCLE 10 OPERATION

References:

1. NRC Bulletin 90-02, dated March 20, 1990, "Loss of Thermal Margin Caused by Channel Box Bow"

2. Letter G02-94-074, dated March 29, 1994, JV Parrish (SS) to USNRC, "Response to NRC Bulletin 90-02: 'Loss of Thermal Margin Caused by Channel Box Bow,'ffect on Cycle 10 Operation" INTR DUCTION NRC Bulletin (NRCB) 90-02 (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 also requested to advise the NRC of the number and location of reused 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. Several letters have been exchanged between the NRC and the Supply System regarding this matter. The most recent correspondence (Reference 2) updated the Supply System response to NRCB 90-02 for-WNP-2 Cycle 10.

9405270121 940520 PDR ADOCK 05000397 9 PDR

Page 2 Response to NRC Bulletin 90-'02: "L'oss of Thermal Margin Caused by Channel Box Bow", Response to Questions on Cycle 10 Operation On Tuesday, April 26, 1994, a telephone call was held between NRC and Supply System personnel to discuss Reference 2. The NRC requested some additional information. The Supply System response is provided below.

R PONSE TO RE VEST F R ADDITIONALINF RMATI N NR R uest I Provide information regarding the effect of channel box bow on the MCPR Safety Limit for the Cycle 10 design.

Su l S em Res onse As indicated in Reference 2, page 3, the effect of channel box bow is addressed in the Siemens Power Corporation (SPC) methodology for determining the MCPR Safety Limit. The Cycle 10 MCPR Safety Limit is 1.07 for two recirculation loop operation and 1.08 for single loop operation. The Cycle 10 MCPR Safety Limit, unchanged from Cycle 9, is consistent with WNP-2 Technical Specification 2.1.2. The effects of channel bow increase the Cycle 10 MCPR Safety Limit by about 0.02, Provide an estimate of the maximum expected distortion for the reused channels in Cycle 10.

u I stem Res onse As discussed in Reference 2, page 5, the reused channels with the largest estimated exposure at the.end of Cycle (EOC) 10 are channels 71848 and 61550. The EOC.10 maximum distortion for these channels is predicted to be less than 105 mils. However, as discussed on page 4 of Reference 2, some reused channels in Cycle 10 will experience a second cycle of irradiation on the core edge. This practice has been implemented for Cycle 10 to help minimize the number of fuel shuffles during the refueling outage.. Twenty reused channels will reside in the same core edge locations for a second cycle. Sixteen of the twenty reused channels meet the acceptance criteria for reuse. The four channels (listed in Reference 2, page 4) do not meet the acceptance criterion for distortion towards the in-core instrumentation. However, the Supply System has

, concluded that reuse of the four channels is acceptable because there is no in-core instrumentation adjacent to them. The four channels meet the Supply System requirement that reused channels not interfere with in-core instrumentation. The maximum EOC 10 distortion for the 20 channels, is predicted to be less than 113 mils, on channel 61972. Of all the reused channels in the Cycle 10 core, channel 61972 is predicted to have the largest distortion at EOC 10,

Pag 3 Response to NRC Bulletin 90-02: "Loss of Thermal Margin Caused by Channel Box Bow", Response to Questions on Cycle 10 Operation CONCLUSI N In summary, the effects of channel bow increase the Cycle 10 MCPR Safety Limit by about 0.02, and the maximum reused channel distortion is predicted to be less than 113 mils. As stated in Reference 2, the Supply System will continue to use its channel bow methodology to assure that reused channels will not interfere with control blades or in-core instrumentation.

NRC approved methods for accounting for channel bow effects in the MCPR Safety Limit will also continue to be used.

Should you have any questions or desire additional information regarding this matter, please contact me or H. E. Kook at (509) 377-4278.

. Parrish (1023)

Assistant Managing Director for Operations JDF CC: LJ Callan - NRC RIV JW Clifford - NRC KE Perkins, Jr. - NRC RIV, Walnut Creek Field Office NRC Sr. Resident Inspector - 927N NS Reynolds - Winston 8c Strawn DL Williams - BPA/399

STATE OF WASHINGTON )

Subject:

Response to NRC Bulletin 90-02

)

COUNTY OF BENTON )

I. J. V. PARRISH, being duly sworn, subscribe to and say that I am the Assistant Managing Director, Operations 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 the best of my knowledge, information, and belief the statements made in it are true.

DATE g4 4 , 1994 J Parrish, Assistant Managing Director erations On this date personally appeared before me J. V. PARRISH, 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 ~/day of 1994.

Notary Public in and or the STATE OF WASHINGTON Residing at ' ~

My Commission Expires '.>'7 V