NOC-AE-09002379, Response to Request for Additional Information Regarding a Proposed One-Time Exigent Change to Technical Specification 3.7.1.7, Main Feedwater System

Response to Request for Additional Information Regarding a Proposed One-Time Exigent Change to Technical Specification 3.7.1.7, Main Feedwater System

ML090130093
Person / Time
Site:	South Texas
Issue date:	01/07/2009
From:	Bowman C Southern Nuclear Operating Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
NOC-AE-09002379, STI: 32417990, TAC ME0271
Download: ML090130093 (4)

Text

Nuclear Operating Company South Texas Pro/ect Electric GeneratingStation P.O Box 289 Wadsworth. Texas 77483 -

January 7, 2009 NOC-AE-09002379 10 CFR 50.90 10 CFR 50.91 U. S. Nuclear Regulatory Commission Attention: Document Control Desk One White Flint North 11555 Rockville Pike Rockville, MD 20852-2738 South Texas Project Unit 2 Docket No. STN 50-499 Response to Request for Additional Information Regarding a Proposed One-Time Exigent Change to Technical Specification 3.7.1.7, "Main Feedwater System" (TAC No.' ME027 1)

Reference:

Letter from Charles T. Bowman, STPNOC, to NRC Document Control Desk dated December 19, 2008, "License Amendment Request Proposed One-Time Exigent Change to Technical Specification 3.7.1.7 "Main Feedwater System" (NOC-AE-08002378)

In the referenced letter, STP Nuclear Operating Company (STPNOC) submitted a license amendment request to support a one-time exigent change to Technical Specification 3.7.1.7, "Main Feedwater System". This submittal responds to NRC questions regarding this request received by phone conversation on December 31, 2008. The responses were previously provided by electronic mail on December 31, 2008.

There are no new commitments in this submittal. If you have any questions, please call Ken Taplett at 361-972-8416 or me at 361-972-7454.

I declare under penalty of perjury that the foregoing is true and correct.

Executed on _4uc704 4 /Z-.Lc Charles T. Bowman General Manager, Oversight

Attachment:

STPNOC Response to Request for Additional Information STI: 32417990

NOC-AE-09002379 Page 2 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 Senior Resident Inspector Kevin Howell U. S. Nuclear Regulatory Commission Catherine Callaway P. 0. Box 289, Mail Code: MN116 Jim von Suskil Wadsworth, TX 77483 NRG South Texas LP C. M. Canady Ed Alarcon City of Austin J. J. Nesrsta Electric Utility Department R. K. Temple 721 Barton Springs Road Kevin Pollo Austin, TX 78704 City Public Service Richard A. Ratliff Jon C. Wood Bureau of Radiation Control Cox Smith Matthews Texas Department of State Health Services 1100 West 49th Street C. Kirksey Austin, TX 78756-3189 City of Austin Mohan C. Thadani Senior Project Manager U.S. Nuclear Regulatory Commission One White Flint North (MS 7 D1) 11555 Rockville Pike Rockville, MD 20852 STI:32417990

NOC-AE-09002379 Attachment Page 1 of 2 STPNOC RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION South Texas Project Unit 2 Docket No. STN 50-499 Response to Request for Additional Information Regarding a Proposed One-Time Exigent Change to Technical Specification 3.7.1.7, "Main Feedwater System" (TAC No. ME0271)

The following information was requested by Mohan Thadani, NRC, Senior Project Manager, during phone conversations conducted with Ken Taplett, STPNOC, on December 31, 2008. The responses below were provided by electronic mail on December 31, 2008.

NRC Request for Information #1: Discuss the containment isolation valve function of the feedwater isolation valves (FWIV) and provide further justification of the one-time extension of the allowed outage time of an inoperable but open FWIV from 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> to 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />.

STPNOC Response: The feedwater isolation valves are containment isolation valves that meet General Design Criterion (GDC) 57 of Appendix A to 10 CFR 50. The feedwater isolation valves are in piping that is neither part of the reactor coolant pressure boundary nor connected directly to the containment atmosphere. The proposed one-time 24-hour action completion time is reasonable, based on operating experience and the low probability of an event occurring during this time period that would require isolation of the main feedwater flow paths to the steam generators.

Although South Texas Project TS 3.6.3, "Containment Isolation Valves", is not applied to an inoperable feedwater isolation valve because this valve has its own TS, the one-time request to extend the allowed outage completion time to 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> is consistent with the Completion Time allowed in TS 3.6.3. South Texas Project TS 3.6.3 allows with one or more isolation valves inoperable, at least one isolation barrier must be maintained operable in the affected penetration that is open and within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> (if the valve is not restored to an operable status) the affected penetration must be isolated by use of the deactivated automatic valve (in this case, the FWIV) secured in the isolation position. A GDC 57 closed system meets the requirement of an isolation barrier. In addition, the proposed one-time 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> allowed outage time is more conservative than ITS Condition C of TS 3.6.3, "Containment Isolation Valves", for one or more penetrations inoperable (applicable to penetration flow paths with only one containment isolation valve and a closed system) that allows a 72 hour8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> allowed outage time for an inoperable valve in this type of penetration.

NOC-AE-09002379 Attachment Page 2 of 2 NRC Request for Information #2: STP-2 relies upon stopping the SG Feedwater Pump and the feedwater control valve as compensatory action for a failure of the feedwater isolation valve.

The accident analysis indicates the feedwater isolation valve is required to close in 13 seconds to limit the maximum containment pressure for a main steamline break in containment.

We cannot determine from the UFSAR whether the stopping time for the SG feedwater pumps and the closing of the feedwater control valve is within the 13 seconds assumed in the accident analysis. If they are not, we cannot find any reference to a containment pressure accident analysis for a main steamline break in containment with feedwater isolation times based on the control valve and feedwater pump closing and stopping times. We would expect the analysis has already have been performed as part of their single failure analysis.

Two questions:

1) Is the isolation of feedwater to the steam generators using the stopping of the steam generator feedwater pumps and the closing of the feedwater control valves within the 13 second closing time assumed for the feedwater isolation valve as used in the accident analysis discussed in UFSAR Section 6.2?

2) If the isolation of feedwater to the steam generators by the stopping of the steam generator feedwater pumps and the closing of the feedwater control valves is greater than the 13 second closing time assumed for the feedwater isolation valve, what is the peak containment pressure for a main steamline break in containment?

Note: The 72 hour8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> AOT for containment isolation valves as listed in the WOG standard technical specifications appears to be based on minimizing radiological leakage from containment. We haven't found any discussion in the bases on restricting feedwater inventory to the steam generators during a main steamline break in containment to limit maximum containment pressures.

STPNOC Response: The accident analysis, discussed in UFSAR Section 6.2, credits feedwater isolation within 13 .seconds of feedwater isolation signal initiation to limit the maximum containment pressure for a main steamline break in containment. The feedwater control valves receive a feedwater isolation signal and are designed to close in sufficient time to meet the 13 seconds assumed in the accident analysis. The closure time of the feedwater control valves are verified every refueling cycle by plant surveillance procedures. Therefore, the feedwater control valves function as a backup feature to limit the maximum containment pressure for a main steamline break in containment.

The accident analysis discussed in UFSAR Section 6.2 does not credit the stopping of the steam generator feedwater pumps.