ML19095A438

Response to IE Bulletin 77-04, Advising, Surry Utilize Addition of Naoh to Containment Spray & Post LOCA Sump Ph Is within Limits for All Operating Conditions

ML19095A438
Person / Time
Site:	Surry
Issue date:	01/19/1978
From:	Stallings C Virginia Electric & Power Co (VEPCO)
To:	O'Reilly J NRC/RGN-II
References
IEB-77-004, Serial No. 507A/110477
Download: ML19095A438 (2)

Text

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e VIRGINIA ELECTRIC AND POWER COMPANY e

RICHMOND,VIROINIA 23261 January 19, 1978

¥.r. James f. O'Reilly, Director Serial No. 507A/110477 Office of Inspection and Enforcement PO&M/DLB:d.as U. S. Nuclear Regulatory Commission Docket Nos. 50-280 Region II - Suite 818 50-281 230 Peachtree Street, Northwest License Nos. DPR-32 Atlanta, Georgia 30303 DPR-37

Dear Mr. O'Reilly:

This is in response to IE Bulletin 77-04, *.;calculational Error Affecting the Design Performance of a System for Controlling pH of Containment Sump Fol-lowing a LOCA". The bulletin discussed a design error at a station which uti-lizes baskets of trisociium phosphate dodecahydrate (TSP) for sump pii control.

Our Surry Power Station Unit Nos. 1 and 2 utilize the addition of NaOH to containment spray for iodine removal and sump pH control. The ultimate sump pn following a LOCA is dependent on the volume and boron concentration in the Boron Injection Tank, the Accumulators, the Reactor Coolant System and the Refueling Water Storage Tank and on the volume and 1~aOH concentration in the Chemical Ad-dition Tank. Among the bases for the selection of these volumes and concentra-tions is a desired ultimate sump pH of 7.0 to 9.0. This range is considered acceptable based on the following criteria:

1. The lower bound of 7.0 is established to inhibit stress corrosion cracking of austenitic stainless steel components, as required by Standard Review Plan (SRP) 6.1.1 and Branch Technical Position HTEB-6-1.

2. The upper bound of 9.0 is established based on the following:

a. SRP 6.5.2 requires a minimum pH of 8.5 for the equilibrium sump pH to prevent a significant evolution of iodine.

b. Branch Technical Position NTEB-6-1 states that the higher the pH (7.0 to 9.5), the greater the assurance that no stress corrosion cracking will occur. The upper bound of 9.0 meets these criteria.

A conservative evaluation of the pH extremes of the sump water subsequent to a LOCA yields upper and lower pH values of 8.8 and 7.9 respectively for Surry Unit Nos. 1 and 2. The minimum slllilp pii is based on the maximum boron concentra-tion and volume in the accumulators, boron injection tank, refueling water stor-age tank and the reactor coolant system combined with the minimum NaOH concentra-tion and volume in the chemical addition tank. The maximum sump pH is based on the reverse extremes of volume and concentration.

Mr. James P. O'Reilly e Page No. 2 It is concluded that the design limits for post LOCA sump pH of 7.0 to 9.0 are appropriate. Surry Unit Nos. 1 and 2 containment post LOCA sump pH is with-in these limits for all operating conditions.

Very truly yours, C. 11. Stallings~

Vice President - Power Supply and Production Operations