ML18153C978

Forwards Supplemental Info to Address Questions Identified During an 920401 Conference Call Re Proposed Increase/ Statistical DNBR Methodology TS Change

ML18153C978
Person / Time
Site:	Surry
Issue date:	04/15/1992
From:	Stewart W VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
91-374A, NUDOCS 9204270018
Download: ML18153C978 (3)

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e e VIRGINIA ELECTRIC AND POWER COMPANY RICHMOND, VIRGINIA 23261 April 15, 1992 United States Nuclear Regulatory Commission Serial No. 91-374A Attention: Document Control Desk NL&P/CGL R1 Washington, D. C. 20555 Docket Nos. 50-280 50-281 License Nos. DPR-32 DPR-37 Gentlemen:

VIRGINIA ELECTRIC AND POWER COMPANY SURRY POWER STATION UNITS 1 AND 2 SUPPLEMENTAL INFORMATION FOR FAh INCREASE/STATISTICAL DNBR METHODOLOGY TECHNICAL SPECIFICATION CHANGES The attached supplemental information is provided to address the questions identified during an April 1, 1992 conference call regarding our proposed FAh increase/statistical DNBR methodology technical specification changes, which were submitted in a July 8, 1991 letter (Serial No.91-374). Specifically, the supplemental information provides:

• the magnitude of the DNBR reduction due to the FAh increase from 1.55 to 1.62 and

• a listing of the most limiting accident by fuel type and DNB correlation.

We understand that this information addresses the outstanding questions associated with the NRC's review of our proposed FAh increase/statistical DNBR methodology technical specification changes.

Very truly yours,

\~

W. L. Stewart Senior Vice President - Nuclear Attachment - Supplemental Information for FAh Increase/Statistical DNBR Methodology Technical Specification Changes 1 9204270018 920415 *~

PDR ADOCK 05000280 l ~ \ 11 P PDR I

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" cc: U. S. Nuclear Regulatory Commission Region II 101 Marietta Street, N. W.

Suite 2900 Atlanta, Georgia 30323 Mr. M. W. Branch NRC Senior Resident Inspector Surry Power Station

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• SUPPLEMENTAL INFORMATION FOR F8h INCREASE/

STATISTICAL DNBR METHODOLOGY TECHNICAL SPECIFICATION CHANGES Magnitude of the DNBR Reduction due to the F8h Increase from 1.55 to 1.62 The magnitude to the DNBR reduction is 7.3% for the limiting statepoint conditions of the accidents which were not specifically reanalyzed for this submittal.

Listing of the Most Limiting Accident by Fuel Type and DNB Correlation For the LOPAR fuel, the W-3 DNB correlation is used. Only standard deterministic methods will be used on this fuel type.

• The most limiting overtemperature delta-T (OT8T) event is the Rod Withdrawal at Power. As discussed on page 34 of the attachment to our July 8, 1991 letter (Serial No.91-374), this accident was not reanalyzed since the current OT8T setpoints were shown to be bounding for a 1.62 F8h (refer to Section 4.3 of our previous submittal).

• The most limiting DNB event that does not trip on OT8T is the Loss of Flow event.

As discussed on page 35 of our previous submittal, the existing Loss of Flow analysis for LOPAR included a 1.62 F8h.

For the SIF fuel, the WRB-1 correlation will be used for any reanalysis (within the range of the correlation). In addition*, the accidents listed in Table 3.3-3 of our previous submittal will be performed using statistical methods.

• The most limiting OT8T event is the Rod Withdrawal at Power. The existing analysis used the W-3 correlation and deterministic methods. As discussed on page 34 of our previous submittal, this accident was not reanalyzed since the current OT8T setpoints were shown to be bounding for a 1.62 F8h (refer to Section 4.3 of our previous submittal). Until such time as reanalysis is required, deterministic methods using either W-3 or WRB-1 are conservative.

• The most limiting statistical DNB event that does not trip on OT8T is the Loss of Flow event. Even though the existing analysis was based on a 1.62 F8h using WRB-1, this event was reanalyzed using the statistical DNB methods (as discussed on page 35 of our previous submittal) to regain analysis margin and as a demonstration of the Statistical DNB Methodology.

• The Locked Rotor event is the most limiting DNB event for SIF where deterministic methods apply. A detailed core thermal-hydraulics analysis was performed (as discussed on page 36 of our previous submittal) to verify that the UFSAR locked rotor analysis assumption of no more than 5% failed fuel will continue to remain valid for a peak F8h of 1.62 for both LOPAR and SIF.