NOC-AE-08002328, Response to NRC Request for Information Regarding STPNOC Request to Extend Implementation Date for ECCS Sump Design Basis

Response to NRC Request for Information Regarding STPNOC Request to Extend Implementation Date for ECCS Sump Design Basis

ML081890190
Person / Time
Site:	South Texas
Issue date:	06/26/2008
From:	Gerry Powell South Texas
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
NOC-AE-08002328
Download: ML081890190 (4)

Text

Nuclear Operating Company CX7EW~

South Texas Pro/ectElectic GeneratingStation PO.Box 289 Wadsworth. Texas 77483

• /AA -

June 26, 2008 NOC-AE-08002328 IOCFR50 U. S. Nuclear Regulatory Commission Attention: Document Control Desk One White Flint North 11555 Rockville Pike Rockville, MD 20852-2738 South Texas Project Units 1 and 2 Docket Nos. STN 50-498, STN 50-499 Response to NRC Request for Information Regarding STPNOC Request to Extend Implementation Date for ECCS Sump Design Basis

References:

Letter from G. T. Powell, STPNOC, to NRC Document Control Desk, dated June 19, 2008, "Request for Extension for Final Response to Generic Letter 2004-02 and Implementation of Revised Design Basis for ECCS Sump" (TAC Nos. MC4719 and MC4720, NOC-AE-08002316)

On June 24, 2008, a conference call was held between the Nuclear Regulatory Commission (NRC) and STP Nuclear Operating Company (STPNOC) regarding the referenced correspondence. The NRC requested clarification on the completion of actions being proposed to resolve Generic Letter (GL) 2004-02 and Generic Safety Issue (GSI)-191. Thisjetter provides the requested clarification regarding potential contingency actions for the testing of the STP Emergency Core Cooling System (ECCS) sump strainers.

Additional strainer head loss and chemical effects testing is scheduled to be performed at Alden Research Laboratory July 28-30, 2008. The debris load on the strainers will be reduced from an overly conservative debris load used in the testing earlier this year. The planned testing is expected to demonstrate the capability of the STP sump strainer design to mitigate a conservative debris load from a design basis accident with STP's current configuration. To facilitate the planning of contingency actions should the strainer testing not demonstrate satisfactory performance for STP's current configuration, the test will be structured to determine one or more debris load combinations that can be mitigated by the STP sump strainers. The contingency actions that STPNOC is considering include analysis and/or modifications.

Analytical contingencies would be the preferred approach and include further reduction of conservatism in the debris loading and transport calculations and implementation of the option to risk-inform the maximum break size for debris generation. Depending on the test results, the modifications could include one or more of the following: modification of insulation to reduce fiber load, installing debris interceptors, installing additional strainers, and elimination of the automatic start of containment spray.

The December 12, 2008, completion date in the referenced letter does not allow for a significant contingency and may need to be extended if a contingency is needed. However, STPNOC believes the testing plan and contingency options provide assurance that the GSI-191 and GL2004-02 issues will be resolved for STP Units 1 and 2 by December 31, 2009.

STI: 32332374

NOC-AE-08002328 Page 2 Commitments in this letter are listed in the attachment.

If you have any questions, please contact Mr. A. W. Harrison at 361-972-7298 or me at 361-972-7566.

G. T. Powell Vice President, Engineering awh/

Attachments: Commitments

NOC-AE-08002328 Page 3 cc:

(paper copy) (electronic copy)

Regional Administrator, Region IV A. H. Gutterman, Esquire U. S. Nuclear Regulatory Commission Morgan, Lewis & Bockius LLP 612 East Lamar Blvd, Suite 400 Arlington, Texas 76011-4125 Mohan C. Thadani U. S. Nuclear Regulatory Commission Mohan C. Thadani Thad Hill Senior Project Manager Catherine Callaway U.S. Nuclear Regulatory Commission Jim von Suskil One White Flint North (MS 7 D1) NRG South Texas LP 11555 Rockville Pike Rockville, MD 20852 Ed Alarcon Senior Resident Inspector J. J. Nesrsta U. S. Nuclear Regulatory Commission R. K. Temple P. 0. Box 289, Mail Code: MN116 Kevin Polio Wadsworth, TX 77483 City Public Service C. M. Canady Jon C. Wood City of Austin Cox Smith Matthews Electric Utility Department 721 Barton Springs Road C. Kirksey Austin, TX 78704 City of Austin Richard A. Ratliff Bureau of Radiation Control Texas Department of State Health Services 1100 West 49th Street Austin, TX 78756-3189

Attachment NOC-AE-08002328 Commitments

1. CR02-5326-1 11: The test will be structured to determine one or more debris load combinations that can be mitigated by the STP sump strainers. (Complete by test completion date, currently July 30, 2008)

2. CR02-5326-112: STP will consider contingencies listed in the cover letter should strainer testing not demonstrate satisfactory performance. (Complete by test completion date, currently July 30, 2008)

3. CR02-5326-113: Testing plan and contingency options provide assurance that the GSI-191 and GL2004-02 issues will be resolved for STP Units I and 2 by December 31, 2009.