ML17289A772

Interim Part 21 Rept Re Discrepancy in Procedure Used by Siemens Nuclear Power Corp to Analyze Feedwater Controller Failure Event w/COTRANSA2 Computer Code.Initially Reported on 920709.Analysis for Cycle 8 Revised & Incorporated

ML17289A772
Person / Time
Site:	Columbia
Issue date:	08/06/1992
From:	Sorensen G WASHINGTON PUBLIC POWER SUPPLY SYSTEM
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
REF-PT21-92 GO2-92-190, NUDOCS 9208100187
Download: ML17289A772 (11)

Text

h.CCELERATED DISTRIBUTION DEMONSTPA.TION SYSTEM REGULSTL INFORMATION DISTRZBUTIONOZSTEM (RIDE)

ACCFSBION NBR:9208100187 DOC.DATE: 92/08/06 NOTARIZED: NO DOCKET PACIL: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 Control Branch (Document Control Desk)

SUBJECT:

Part 21 rept re critical power ratio calculation. Initially reported on 920617.Feedwater Controller Failure analysis &

MCPR limits revised.

DISTRIBUTION CODE: IE19D TITLE: Part 21 Rept (50 DKT)

COPIES RECEIVED:LTR Q ENCL I SIZE:

NOTES:

RECIPIENT COPIES RECIPIENT COPIES ID CODE/NAME LTTR ENCL ID CODE/NAME LTTR ENCL PD5 LA 1 0 PD5 PD 1 1 DEAN,W. 1 1 INTERNAL: AEOD/DSP/ROAB 1 1 NRR/DOEA/OGCBll 2 2 NRR/DRIS/RVIB9D 1 1 I.BM 01 1 1 RES/DSIR/EIB 1 1 RGNl 1 1 RGN2 1 1 RGN3 1 1 RGN4 1 1 RGN5 1 1 SECY VANDERMEL 1 1 EXTERNAL: INPO RECORD CTR 1 1 NRC PDR 1 1 NSIC SILVER,E 1 1 NOTE TO ALL "RIDS" RECIPIENTS:

PLEASE HELP US TO REDUCE WASTE! CONTACT 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 18 ENCL 17

WASHINGTON PUBLIC POWER SUPPLY SYSTEM P.O. Bocc968 ~ 3000 George Wasbtngton Way ~ Richland, 1Wasbtngton 993524968 ~ (509) 372-5000 August 6, 1992 G02-92-190 Docket No. 50-397 U.S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, D.C. 20555 Gentlemen:

Subject:

WNP-2, OPERATING LICENSE NPF-21 10 CFR PART 21 REPORT A CRITICAL POWER RATIO (CPR) CALCULATION This is' 10 CFR Part 21 report submitted in accordance with the requirements of 10 CFR 21.21. Verbal notification of this condition was made to NRC Operations on July 9, 1992. The information required by the regulations is provided below:

Re uirement 1 Identification of the firm constructing the facility or supplying the basic component which fails to comply or contains a defect.

~Res onse 1 Siemens Nuclear Power Corporation 155 108th Avenue NE, PO Box 90777 Bellevue, WA 98009-0777 Siemens Nuclear Power (SNP) provides the nuclear fuel and the supporting transient analysis for WNP-2. SNP discovered a discrepancy in the procedure used to analyze the Feedwater Controller Failure (FWCF) event with the computer code COTRANSA2. This discrepancy impacted the analysis supporting Cycles 7 and 8 and involved an error in the input to the model which represents core pressurization during the FWCF event. The transient analysis for the fuel is considered a basic component since it analyzes the capability to shutdown the reactor and maintain it in a safe shutdown condition. The safety analysis guarantees cladding integrity in response to transient conditions. It provides assurance that fuel cladding failure due to lack of cooling caused by the onset of transition boiling is limited and complies with licensing requirements.

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Page Two 10 CFR PART 21 REPORT h CRITICAL POWER RATIO (CPR) CALCULATION The cladding is one of the first barriers necessary to'rovide the capability to prevent or mitigate the consequences of accidents. Thus, the reactor fuel and its supporting analysis meet the definition of a basic component as defined in the regulations.

Re uirement 2 Nature of the defect or failure to comply and the Substantial Safety Hazard (SSH) which is created or could be created by such defect or failure to comply.

Res onse 2 One of the definitions of a defect is a condition or circumstance involving a basic component that could contribute to the exceeding of a safety limit, as defined in the WNP-2 Technical Specifications. Technical Specification paragraph 2. 1 defines the safety limits for WNP-2.

Paragraph 2. 1.2 defines the THERMAL POWER safety limit which reads in part, "The MINIMUM CRITICAL POWER RATIO (NCPR) shall not be less than 1.07 up to 4500 NWD/NTU cycle exposure and 1. 11 for cycle exposure greater than 4500 NWD/MTU to EOC." As the h CPR is used to determine the MCPR the situation described by SNP falls within this definition of a defect.

A SSH exists if there is a loss of safety function to the extent that there is a major reduction in the degree of protection provided to public health and safety. This includes exceeding a safety limit as defined in the WNP-2 Technical Specifications. The determination of a SSH for this case is aided by the attached Figure 1. The fuel and its supporting analysis was delivered with the normal design/operating margin to allow for fuel burnup and flexible rod patterns. The plant is allowed to operate at the Operating Limit Minimum Critical Power Ratio (OLNCPR) which is established by the h CPR calculation. However, Plant operation is normally well above the OLNCPR. The severity of FWCF transients is af,ected by cycle exposure. Actual plant operation during cycle 7 was limited to a cycle exposure well below the exposure of concern. However, if Cycle 7 had operated to the licensing basis energy with the licensing basis axial exposure distribution, and if the power level was between approximately 80 and 92 percent, and if assemblies were at the OLMCPR, and if a licensing basis FWCF transient had occurred, then the error in the analysis could have allowed the CPR to drop below the Safety Limit Minimum Critical Power Ratio (SLMCPR). The Supply System believes this meets the definition of a Potential Defect that could create a SSH as defined above.

This situation is highlighted by the fact that the FWCF transient actually occurred at WNP-2 during cycle 7 on November 19, 1991. Because of the design margin, low fuel burnup, and the fact that the transient occurred from 100 percent power the minimum CPR was well above the SLNCPR as shown in Figure 2. The calculated minimum CPR during the transient was 1.35 compared to the SLNCPR of 1.07.

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.'Page Three 10 .CFR PART 21 REPORT b, CRITICAL POWER RATIO (CPR) CALCULATION Re uirement 3 The date on which the information of such defect or failure to comply was obtained.

Res onse 3 June 17, 1992 Re uirement 4 In the case of a basic component which contains a defect or fails to comply, the number and location of all such components in use at, supplied for, or being supplied for one or more facilities or activities subject to the regulations of this part.

Res onse 4 WNP-2 does not have the information to respond to this question as it was the purchaser, not the supplier, of the basic component. However, SNP has stated that they have notified all of their affected customers.

Re uirement 5 The corrective action which has been, is being, or will be taken; the name of the individual or organization responsible for the action; and the length of time that has been or will be taken to complete the action.

Res onse 5 Corrective action to address this concern at WNP-2 has been completed. At the time of notification of the defect, June 17, 1992, SNP had completed their evaluation of the non-conservatism in the FWCF analysis and had established input changes to correct the modeling of core pressurization during FWCF analysis performed with the COTRANSA2 code. Supply System reviews of the non-conservatism concluded the procedural change implement-ed by SNP was acceptable for FWCF analysis performed with COTRANSA2. SNP was requested to revise the FWCF analysis for Cycle 8 and provide revised HCPR limits for incorporation into the Core Operating Limits Report (COLR). The revised limits were also incorporated into the core monitor-ing system (POWERPLEX) for use in monitoring thermal operating limits.

These actions were completed prior to plant restart in early July 1992.

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"Page Four 10 CFR PART 21 REPORT h CRITICAL POWER RATIO (CPR) CALCULATION

~Ri 66 Any advice related to the defect or failure to comply about the facility, activity, or basic component that has been, is being, or will be given to purchasers or licensees.

Res onse 6 WNP-2 is the purchaser and licensee and does not have any advice to relate.

Any questions concerning this report should be referred to Mr. C.L. Fies, Compliance Engineer, (509) 377-4147.

Sincerely, G. C. gorensen, Manager Regulatory Programs (Mail Drop 280)

CLF/bk Attachments cc: JB Martin - NRC RV NS Reynolds - Winston 5 Strawn RR Assa - NRC DL Williams - BPA/399 NRC Site Inspector - 901A U. Fresk - SNP

FIGURE 1 TYPICAL CRITICA PQMER RATIQ (CPR) APPLICATION QPERATING 1,'18-1,78 CPR DESIGN/OPERATING MARGIN 1,18-1,39 QPERATING LIMIT MCPR (QLMCPR)

MARGIN FQR TRANSIENT EVENT (F4'CF)

MCPR 1,85-1,87 SAFETY LIMIT MCPR (SLMCPR)

MARGIN FQR UNCERTAINTIES 1,88 MEAN QF CPR CQRRELATIQN

FIGURE 2 CRITICAL PQMER RATIQ (CPR)

DURING FWCF EVENT NQV 19, 1991 1,'j2 PESIGNyQP ERA TING MARGIN OPERATING MINIMUM CPR ~

DURING EVENT 1,35 1,23 MARGIN FQR TRANSIENT M CPR = 8.16 FOR BOUNDING CREE M CPR = 8,87 FOR FWCF 1,87 SAFETY LIHIT HCPR (S LMCPR)

MARGIN FQR UNCERTA'INTIES 1,88 HEAN OF CPR CORRELATION