ML071380412

Request for Additional Information Regarding Generic Letter 96-06 (TAC No. M96872)

ML071380412
Person / Time
Site:	Summer
Issue date:	08/01/2007
From:	Martin R NRC/NRR/ADRO/DORL/LPLII-1
To:	Archie J South Carolina Electric & Gas Co
Martin R, NRR/DORL, 415-1493
References
GL-96-006, TAC M96872
Download: ML071380412 (6)

Text

August 1, 2007 Mr. Jeffery Archie Vice President, Nuclear Operations South Carolina Electric & Gas Company Virgil C. Summer Nuclear Station Post Office Box 88 Jenkinsville, South Carolina 29065

SUBJECT:

VIRGIL C. SUMMER NUCLEAR STATION REQUEST FOR ADDITIONAL INFORMATION REGARDING GENERIC LETTER 96-06 (TAC NO. M96872)

Dear Mr. Archie:

The Nuclear Regulatory Commission Generic Letter (GL) 96-06, Assurance of Equipment Operability and Containment Integrity During Design-Basis Accident Conditions, dated September 30, 1996, included a request for licensees to evaluate cooling water systems that serve containment air coolers to assure that they are not vulnerable to waterhammer, two-phase flow conditions, and thermally induced overpressurization. The South Carolina Electric and Gas Companys (SCE&Gs) most recent response to the GL was a letter dated November 11, 2006, (Agencywide Documents Access and Management System accession number ML063190303).

SCE&Gs letter provided additional information concerning the few items that remained to be addressed, including technical specification considerations, the consequences of postulated single active failures, inservice test provisions for monitoring boundary valve leakage, and clarification of regulatory commitments relative to planned plant modifications related to this issue. We have determined that additional information is required in order to fully resolve the GL 96-06 issues, as discussed in the enclosure.

Except for the request to update your response on the need for Technical Specifications, this request for additional information (RAI) was discussed with your staff on May 30 and July 24, 2007. Please contact me at 301-415-1493, if you have any questions.

Sincerely,

/RA/

Robert E. Martin, Senior Project Manager Plant Licensing Branch II-1 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-395

Enclosure:

RAI cc: See next page

ML071380412 NRR-088 OFFICE LPL2-1/PM LPL2-1/LA EEEA/BC LPL2-1/BC NAME RMartin:nc CSola JSegala (by memo dated) EMarinos DATE 7/31/07 8/3/07 05/15/07 8/1/07

REQUEST FOR ADDITIONAL INFORMATION CONCERNING THE RESOLUTION OF GENERIC LETTER 96-06 VIRGIL C. SUMMER NUCLEAR STATION (VCSNS)

1. South Carolina Electric & Gas Companys (SCE&Gs) response to Question 2, as provided in its November 11, 2006, letter to the Nuclear Regulatory Commission (NRC), is incomplete as it does not fully address single active failure considerations. Of particular concern is a single failure of a component in the system that results in excessive system voiding and subsequent waterhammer that could cause a loss of piping and/or valve integrity. Should this occur, the service water being pumped into containment may invalidate the containment analytical assumptions and compromise the service water system flow balance; and a loss of service water pipe and/or valve integrity due to a severe waterhammer event could provide a direct leakage path from the containment to the outside environment, thereby compromising one of the three fission product barriers.

Please address the issues in the two following paragraphs:

SCE&G provided a licensee commitment to modify valves 3107A(B) to be fast acting in order to trap water in the high points above these valves and in its letter fo October 8, 2006, revised the schedule for implementing that commitment to refueling outage 17 in the spring of 2008. This modification would prevent void formation from gravity drain-down of the water to the service water pond, thereby preventing the consequential rapid void collapse and waterhammer event that would have otherwise occurred upon re-energizing the service water booster pumps (SWBPs) as explained on page 16 of the December 12, 2005, submittal. The scenario detailed on page 15 of the same submittal describes the situation which will occur if a single failure of valve 3107A(B) were to occur, which states: This will form a large void in the piping. Upon SWBP re-start and the commencing of fluid flow, the void will rapidly collapse creating a significant waterhammer. Because a requirement has not been established to restrict use of the service water system for cooling the reactor building cooling units during normal plant operation, this appears to be the most limiting scenario for GL 96-06 waterhammer considerations. Therefore, with respect to this scenario, please explain how a failure of fast acting valves 3107A(B) to close is mitigated such that system design limitations will not be exceeded. Also, to the extent that additional modifications are necessary to address single failure considerations, an updated response to Question 3 of the NRC staffs RAI dated August 22, 2006, concerning the need for additional Technical Specification requirements is necessary.

The single failure analysis that was discussed in the licensees response dated October 30, 1998, was performed before the plant modifications referred to in the December 12, 2005 and October 8, 2006, letters were proposed for the service water system. Therefore, please confirm that this comprehensive and bounding set of operational transients and single active failure scenarios continue to be valid and bounding relative to the plant modifications that were described.

2. The licensees resolution of the Generic Letter 96-06 thermal overpressurization issue preceded the plant modifications that are referred to in 1(b). Therefore, please confirm that the thermally induced overpressurization analyses that were previously completed remain valid relative to the plant modifications that were described.

Virgil C. Summer Nuclear Station cc:

Mr. Jeffrey B. Archie Ms. Kathryn M. Sutton Vice President, Nuclear Operations Morgan, Lewis & Bockius LLP South Carolina Electric & Gas Company 111 Pennsylvania Avenue, NW.

Virgil C. Summer Nuclear Station Washington, DC 20004 Post Office Box 88 Jenkinsville, SC 29065 Mr. R. J. White Nuclear Coordinator S.C. Public Service Authority c/o Virgil C. Summer Nuclear Station Post Office Box 88, Mail Code 802 Jenkinsville, SC 29065 Resident Inspector/Summer NPS c/o U.S. Nuclear Regulatory Commission 576 Stairway Road Jenkinsville, SC 29065 Chairman, Fairfield County Council Drawer 60 Winnsboro, SC 29180 Mr. Henry Porter, Assistant Director Division of Waste Management Bureau of Land & Waste Management Dept. of Health & Environmental Control 2600 Bull Street Columbia, SC 29201 Mr. Thomas D. Gatlin, General Manager Nuclear Plant Operations South Carolina Electric & Gas Company Virgil C. Summer Nuclear Station Post Office Box 88, Mail Code 300 Jenkinsville, SC 29065 Mr. Bruce Thompson, Manager Nuclear Licensing South Carolina Electric & Gas Company Virgil C. Summer Nuclear Station Post Office Box 88, Mail Code 830 Jenkinsville, SC 29065