ML090080487

South Texas Project, Unit 2 - E-mail #2, Licensee'S Response to Request for Additional Information, Exigent License Amendment Request, Revise Technical Specification 3.7.1.7, Main Feedwater System, to Allow One-Time Allowed Outage Time

ML090080487
Person / Time
Site:	South Texas
Issue date:	12/31/2008
From:	Taplett K South Texas
To:	Thadani M C Plant Licensing Branch IV
Thadani, M C, NRR/DORL/LPL4, 415-1476
References
TAC ME0271
Download: ML090080487 (3)

Text

From: Taplett, Kenneth [kjtaplett@STPEGS.COM] Sent: Wednesday, December 31, 2008 4:55 PM To: Mohan Thadani Cc: Bruce Heida; Stanley Gardocki; Harrison, Albon

Subject:

RE: TWO MORE Qs FOR EXIGENT AMENDMENT Mohan, The STP reply is below. This should address both questions.

Ken "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."

From: Mohan Thadani [1] Sent: Wednesday, December 31, 2008 12:44 PM To: Taplett, Kenneth Cc: Bruce Heida; Stanley Gardocki

Subject:

TWO MORE Qs FOR EXIGENT AMENDMENT Ken:

Reviewer's two additional questions follow:

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.

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Subject:

RE: TWO MORE Qs FOR EXIGENT AMENDMENT

Sent Date: 12/31/2008 4:55:05 PM Received Date: 12/31/2008 4:55:05 PM From: Taplett, Kenneth

Created By: kjtaplett@STPEGS.COM

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