L-12-438, Davis-Besse, Unit 1, Response to Request for Additional Information on 10 CFR 50.46 Report of Changes or Errors in ECCS Evaluation Models

Davis-Besse, Unit 1, Response to Request for Additional Information on 10 CFR 50.46 Report of Changes or Errors in ECCS Evaluation Models

ML12353A601
Person / Time
Site:	Davis Besse
Issue date:	12/18/2012
From:	Lieb R A FirstEnergy Nuclear Operating Co
To:	Office of Nuclear Reactor Regulation, Document Control Desk
References
L-12-438, TAC ME8411
Download: ML12353A601 (3)

Text

R r s t E n ergy N uc l ea r Opera ting C omp a ny Raymo n d A Li eb Vice President, Nuclear December 18, 2012 L-12-438 ATTN: Document Control Desk U.S. Nuclear Regulatory Commission Washington, DC 20555-0001

SUBJECT:

Davis-Besse Nuclear Power Station, Unit No.1 Docket No. 50-346, License No. NPF-3 5501 North State Route 2 Oak Harbor, Ohio 43449 419-321-7676 Fax. 419-321-7582 10 CFR 50.46(a)(3)(ii)

Response to Request for Additional Information on 10 CFR 50.46 Report of Changes or Errors in ECCS Evaluation Models (TAC No. ME8411) By letter dated March 16,2012 (Accession No. ML 12076A237), FirstEnergy Nuclear Operating Company (FENOC) submitted a notification of a significant change and error to the large-break loss-of-coolant accident emergency core cooling model in accordance with Title 10 of the Code of Federal Regulations, Section 50.46(a)(3) for the Davis-Besse Nuclear Power Station, Unit No.1. On November 16,2012, the Nuclear Regulatory Commission (NRC) staff requested additional information regarding this report (Accession No. ML 12310A012).

FENOC's response to the request, as discussed with NRC staff on October 29, 2012, is attached.

There are no regulatory commitments contained in this letter. If there are any questions or if additional information is required, please contact Mr. Thomas A. Lentz, ManagerFleet Licensing, at (330) 315-6810. Raymond A. Lieb

Attachment:

Response to Request for Additional Information on the Notification of Significant Change to the Large-Break Loss-of-Coolant Accident Emergency Core Cooling Model cc: NRC Region III Administrator NRC Resident I nspector Nuclear Reactor Regulat i on Project Manage r Utility Radiological Safety Board Attachment L-12-438 Response to Request for Additional Information on the Notification of Significant Change to the Large-Break Loss-of-Coolant Accident Emergency Core Cooling Model Page 1 of2 By letter to the U.S. Nuclear Regulatory Commission (NRC) dated March 16, 2012, FirstEnergy Nuclear Operating Company (FENOC), sent a notice reporting a change or error discovered in an evaluation model, or in the application of such a model, that affects the peak cladding temperature (PCT) calculation for Davis-Besse Nuclear Power Station (DBNPS). On November 16, 2012, the NRC requested additional information regarding this notice. The NRC staff's request is presented in bold type, followed by FENOC's response.

1. There are two changes to PCT for large-break loss-of-coolant accident (LBLOCA) analysis discussed in the report submitted by the licensee.

The first change is an Evaluation Model (EM) application error in the determination of the end of emergency core cooling system (ECCS) bypass, which resulted in an 80 of decrease in PCT. The second change is an EM modeling change to include the effects of the' upper plenum column weldments, which resulted in an 80 of increase in PCT. Provide the analysis that lead to each change having an 80 of change in PCT. Response Details of the analyses performed by AREVA, the fuel vendor in evaluating the two EM changes, (in non-proprietary report ANP-3180, Revision 000, "177 Fuel-Assembly Plant RAI Responses to a 30-Day 50.46 Report of Significant PCT Change," December 2012) were submitted to the NRC by AREVA letter, "Generic RAI Response to a 30-Day 10 CFR 50.46 Report of Significant PCT Change," on December 6,2012. FENOC has reviewed ANP-3180, Revision 000, and has determined that the conclusions are applicable to DBNPS. 2. 10 CFR 50.46(a)(3)(ii) states: II *** If the change or error is significant, the applicant or licensee shall provide this report within 30 days and include with the report a proposed schedule for providing a reanalysis or taking other action as may be needed to show compliance with 50.46 requirements

• • • " The PCT for LBLOCA for DBNPS has changed by an absolute value of 160 OF since the analysis was performed.

Simply reporting the changes and errors in the methodology does not satisfy the intent of the regulation.

Justify not providing a schedule for reanalysis or taking other action to show compliance with 10 CFR 50.46 Attachment L-12-438 Page 2 of2 Response In accordance with 10 CFR 50.46(a)(3)(ii), on May 27,2011 (Accession No. ML 111510642), FENOC submitted a Report of Changes or Errors for the current PCT for a large-break LOCA at DBNPS as being 2,119°F. By letter dated February 13,2012 (Accession No. ML 120440609)

FENOC discussed the basis for this value. This was the last reported value prior to the identification of these errors. The AREVA report referenced in the response to Question 1 provides additional details regarding the analytical bases for the PCT error estimates, which were based upon explicit RELAP5/Mod2-B&W code runs for a Babcock & Wilcox (B&W)-designed nuclear steam supply systems (NSSS). The error that was corrected in the evaluation models was specific to the determination of the end of emergency core cooling system (ECCS) bypass. A separate change to the ECCS evaluation model was made based on the effects of the upper plenum column weldments.

As evidenced by the information provided by AREVA's response to Question 1, both of the EM items have been analyzed in detail. Furthermore, the impact on the ECCS evaluation model does not result in any challenge to the 10 CFR 50.46(b) acceptance criteria.

As the individual items have been analyzed and there are no other known errors or changes to be evaluated at this time, the overall evaluation model is considered acceptable.

In summary, the responses to the NRC staff requests establish the following:

• The error-adjusted PCT for a large-break LOCA at DBNPS remains below the 10 CFR 50.46(b) acceptance criteria and is considered to be adequate.

• The SBLOCA analyses are not affected by the reported ECCS evaluation model errors.

• The AREVA response referenced in Question 1 provides additional information regarding the nature of the PCT change evaluations, which are supported by explicit analyses using the B&W plant ECCS evaluation model. Based on the above, there are no adverse impacts to safety. Revision of the EM or design basis analysis-of-record for DBNPS is not warranted.