ML20077D182

Provides Addl Info Re Proposed Change 101 to Tech Specs Proposing to Raise Current Full Power Torus Temp Limit. Rev 1 to Figure 3 Encl Correcting Improper Factoring of Submergence Elevation of Tee Quencher

ML20077D182
Person / Time
Site:	Vermont Yankee File:NorthStar Vermont Yankee icon.png
Issue date:	07/20/1983
From:	Sinclair J VERMONT YANKEE NUCLEAR POWER CORP.
To:	Vassallo D Office of Nuclear Reactor Regulation
References
FVY-83-76, NUDOCS 8307260408
Download: ML20077D182 (3)

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- VERMONT YANKEE NUCLEAR POWER CORPORATION 2.C.2.1 FVY 83-76 RD 5, Box 169 Ferry Road, Brattleboro, VT 05301

. g ENGINEERING OFFICE 1671 WORCESTER ROAD FRAMiNGHAM, MASSACHUSETTS 01701 July 20, 1983 TELEPHONE 6174724100 United States Nuclear Regulatory Commission Washington, D. C. 20555 Attention:

Office of Nuclear Reactor Regulation Mr. Domenic B. Vassallo, Chief Operating Reactors Branch No. 2 Division of Licensing

References:

(a) License No. DPR-28 (Docket No. 50-271)

(b) Letter, VYNPC to USNRC, FVY 82-86, Proposed Change No.101 to Vermont Yankee Technical Specifications, dated July 22, 1982

Subject:

Suppression Chamber Temperature Limit

Dear Sir:

The purpose of this letter is to provide you with additional information with regard to Reference (b), Proposed Change No.101 to the Vermont Yankee Technical Specifications. This change, which proposes to raise the current full power torus temperature limit from 900F to 1000F, takes advantage of improved margin to steam quenching instability resulting from the installation of Monticello-type tee quenchers at our facility.

As discussed in a telecon on July 15, 1983 with Mr. V. Rooney of your staff, we have recently become aware that the submergence elevation of our tee quencher was not properly factored into the development of Figure 3 of Reference (b), " Comparison of Tee Quencher Bulk Suppression Pool Temperature Limit to Stuck Open S/RV from 100% Power Transient Responses". The actual submergence of our tee quencher is 7.75 feet. Assuming an overall pool tcaperature of 2100F and a nominal submergence of 7 feet, the pressure at these conservative conditions is 14.7 psia + 2.9 psia or 17.6 psia. This reprecents the minimum pressure at the tee quencher elevation. The saturation pressure at 17.6 psia is 221.20F.

Subtracting the 200F subcooling allowed leaves 201.20F or nominally 2000F. Thus, the NUREG-0783 local temperature limit, Figure 3 - Curve 1, has been redrawn on the enclosed revised figure as a constant value of 2000F.

Taking this factor into account alters the tee quencher bulk pool temperature limit, Figure 3 - Curve 2, for the case with Residual Heat Removal (RHR) off and with RHR on, as shown. However, ample margin still exists between the transient response (Figure 3 - Curve a and b) and the redrawn bulk pool temperature limits, as shown on the revised figure.

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U. S.: Nuclear Regulatory Commission July 20, 1983

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Attention:

Mr. D. B.- Vassallo Page 2 Based on the above, we are requesting that you replace the existing Figure 3 'of Reference (b) with the enclosed Figure 3, Revision 1.

We trust-that this submittal will not impact the timely review of our proposed change; however, should you have any questions, please contact us.

Very truly yours, VERMONT YANKEE NUCLEAR POWER CORPORATION

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Y J. B. Sinclair Licensing Engineer-JBS/ds v

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