BVY 05-099, Technical Specification Proposed Change No. 263 - Supplement No. 39 Extended Power Uprate - Risk Analysis of Containment Overpressure

Technical Specification Proposed Change No. 263 - Supplement No. 39 Extended Power Uprate - Risk Analysis of Containment Overpressure

ML053060323
Person / Time
Site:	Vermont Yankee File:NorthStar Vermont Yankee icon.png
Issue date:	10/26/2005
From:	Thayer J Entergy Nuclear Northeast, Entergy Nuclear Operations
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
%dam200601, BVY 05-099, TAC MC0761
Download: ML053060323 (4)

Text

Entergy Entergy Nuclear Northeast Entergy Nuclear Operations, Inc.

Vermont Yankee P.O. Box 0500 185 Old Ferry Road Brattleboro, VT 05302-0500 Tel 802 257 5271 October 26,2005 Docket No. 50-271 BVY 05-099 TAC No. MC0761 ATTN: Document Control Desk U.S. Nuclear Regulatory Commission Washington, DC 20555-0001

Subject:

Vermont Yankee Nuclear Power Station Technical Specification Proposed Change No. 263 - Supplement No.39 Extended Power Uprate - Risk Analysis of Containment Overpressure

Reference:

1) Entergy letter to U.S. Nuclear Regulatory Commission, "Vermont Yankee Nuclear Power Station, License No. DPR-28 (Docket No. 50-271), Technical Specification Proposed Change No. 263, Extended Power Uprate," BVY 03-80, September 10, 2003

2) Entergy letter to U.S. Nuclear Regulatory Commission, "Vermont Yankee Nuclear Power Station, License No. DPR-28 (Docket No. 50-271), Technical Specification Proposed Change No. 263 Supplement No. 38, Extended Power Uprate -

Containment Overpressure Credit," BVY 05-098, October 21, 2005

3) U.S. Nuclear Regulatory Commission, "An Approach for Using Probabilistic Risk Assessment in Risk-Informed Decisions on Plant-Specific Changes to the Licensing Basis," Regulatory Guide 1.174, Rev. 1, November 2002

4) Entergy letter to U.S. Nuclear Regulatory Commission, "Vermont Yankee Nuclear Power Station, License No. DPR-28 (Docket No. 50-271),

Technical Specification Proposed Change No. 263 Supplement No. 8, Extended Power Uprate - Response to Request for Additional Information," BVY 04-058, July 2, 2004 This letter provides additional information regarding the application by Entergy Nuclear Vermont Yankee, LLC and Entergy Nuclear Operations, Inc. (Entergy) for a license amendment (Reference 1) to increase the maximum authorized power level of the Vermont Yankee Nuclear Power Station (VYNPS) from 1593 megawatts thermal (MWt) to 1912 MWt.

As part of the extended power uprate (EPU) submittal for VYNPS, Entergy proposed taking credit for containment accident pressure to provide adequate net positive suction head (NPSH)

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BVY 05-099 Docket No. 50-271 Page 2 of 3 to the emergency core cooling system (ECCS) pumps during the large break loss-of-coolant accident and anticipated transients without scram.

In Reference 2 Entergy supplemented the analyses crediting containment accident pressure that were performed in accordance with traditional engineering methods, with risk-informed evaluations of the impact of the proposed change in licensing basis. Attachment 1 to this letter provides the quantitative risk assessment that was not complete at the time Reference 2 was submitted.

Regulatory Guide 1.174 (Reference 3) provides guidance for determining the risk impact of plant-specific licensing basis changes. The metrics that have been adopted in Regulatory Guide 1.174 for the characterization of risk are core damage frequency (CDF) and large early release frequency (LERF). Acceptability is predicated on there being small changes in CDF and LERF.

Results of the risk assessment of plant internal events for VYNPS demonstrate that the risk impact of the proposed change to credit containment overpressure is very small (approximately 5.78E-7/reactor-year (ry) increase in CDF, and approximately 4.50E-8/ry increase in LERF). These risk estimates meet the acceptance criteria of Regulatory Guide 1.174 to be considered very small changes in risk (i.e., < 1E-6/ry ACDF and < 1E-7/ry ALERF).

Entergy made appropriate changes to the probabilistic safety assessment model to enable the performance of cases which address the impact of crediting containment overpressure.

The risk assessment examined event sequences in which containment integrity is necessary for success of the low pressure emergency core cooling system pumps. The steps taken to perform the risk assessment are included in Attachment 1. In addition, as a result of these changes, Attachment 1 supersedes the response to NRC's request for additional information SPSB-C-1 that was provided in Attachment 1 of Reference 4.

The common conclusion from the analyses, using both traditional engineering and risk-informed approaches, is that the proposed crediting of containment accident pressure represents a small change in risk and meets NRC's policy statement for safety goals.

There are no new regulatory commitments contained in this submittal.

This supplement to the license amendment request provides additional information to clarify Entergy's application for a license amendment and does not change the scope or conclusions in the original application, nor does it change Entergy's determination of no significant hazards consideration.

If you have any questions or require additional information, please contact Mr. James DeVincentis at (802) 258-4236.

BVY 05-099 Docket No. 50-271 Page 3 of 3 I declare under penalty of perjury that the foregoing is true and correct.

Executed on October 26, 2005.

Sincerely, 44y KIl To~yer w~iice President Vermont Yankee Nuclear Power Station Attachments (1) cc:

Mr. Samuel J. Collins (w/o attachment)

Regional Administrator, Region 1 U.S. Nuclear Regulatory Commission 475 Allendale Road King of Prussia, PA 19406-1415 Mr. Richard B. Ennis, Project Manager Project Directorate I Division of Licensing Project Management Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission Mail Stop 0 8 B1 Washington, DC 20555 USNRC Resident Inspector (w/o attachment)

Entergy Nuclear Vermont Yankee, LLC P.O. Box 157 Vernon, Vermont 05354 Mr. David O'Brien, Commissioner VT Department of Public Service 112 State Street - Drawer 20 Montpelier, Vermont 05620-2601

BVY 05-099 Docket No. 50-271 Vermont Yankee Nuclear Power Station Proposed Technical Specification Change No. 263 - Supplement No. 39 Extended Power Uprate - Risk Analysis of Containment Overpressure Engineering Report No. RPT-05-001IO, Rev. 0 Total number of pages in Attachment 1 (excludina this cover sheet) Is 303.