ML20082F032

Supplemental Info to Application for Amend to Licenses NPF-9 & NPF-17,changing Tech Spec to Allow Conditional Increase in Containment Lower Compartment Temp to 125 F. Supplemental Justification Encl

ML20082F032
Person / Time
Site:	Mcguire, McGuire
Issue date:	11/14/1983
From:	Tucker H DUKE POWER CO.
To:	Adensam E, Harold Denton Office of Nuclear Reactor Regulation
References
NUDOCS 8311280408
Download: ML20082F032 (2)

Text

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DUKE POWER GOMPANY P.O. BOX 33180 CHARLOTTE, N.C. 28242 HAL B. TUCKER TELEPHONE' vw= = == ' November 14, 1983 (*) Ne pf00 LEAR PROBUCT90N Mr. Harold R. Denton, Director Office of Nuclear Reactor Regulation U. S. Nuclear Regulatory _ Commission Washington, D. C. 20555 Attention: Ms.' E. G. Adensam, Chief Licensing Branch No. 4 Re: McGuire Nuclear Station Docket Nos. 50-369, 50-370

Dear Mr. Denton:

Elinor G. Adensam's letter of November 1, 1983 requested confirmatory information regarding a license amendment authorized via telephone on October 26, 1983. The license amendment involved a change in Technical Specification 3.6.1.5 to allow a conditional increase in the containment lower compartment temperature. Attached is a report of an analysis which provides the requested information. Please advise if there are additional questions.

Very truly yours, ,

Y /c Hal B. Tucker GBS/REH/j fw Attachment cc: Mr. James P. O'Reilly, Regional Administrator U. S. Nuclear Regulatory Commission

. Region II 101 Marietta Street, NW, Suite 2900 l

Atlanta, Georgia 30303

{ Mr. W. T. Orders NRC' Resident Inspector l McGuire Nuclear Station faa N^

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! 8311280408 831114 PDR ADOCK 05000369 P PDR l

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}. -s Supplemental Justification for Raising the Lower Containment Temperature from 120*F to 125*F The original justification for raising the lower containment temperature from 120*F to 125'F was provided in H. B. Tucker's October 26, 1983 letter to Harold R. Denton. By letter dated November 1, 1983, the NRC requested additional confirmatory information:

". . . provide either (1) confirmatory calculations utilizing the highet lower compartment air temperature, demonstrating conformance to 10 CFR 50.46 or (2) justification that the containment backpressure used in the LOCA analysis contains sufficient margin in excess of statisti-cal uncertainties'such that this margin is more than sufficient to bound the backpressure resulting from the higher compartment temperature."

This supplemental justification will demonstrate per option (2) above, that the effects of an increase in lower containment temperature are bounded by the existing LOCA analysis.

The original justification utilized a conservative hand calculation based on the difference in the initial containment air mass (120*F vs. 125'F), and the resulting difference in the partial pressure of the air mass following a LOCA.

This pressure difference, -0.15 psi, was then evaluated by a graphical comparison with the FSAR lower containment pressure response (FSAR Figure 15.4.1-62). This simple approach was followed since Duke Power considered that the very small pressure difference would be recognized by the NRC as insignificant. Since additional confirmatory information has been requested, the hand calculation has been refined, and the exact numerical results of the lower containment pressure response, rather than a graphical estimate, have been utilized.

The analysis documentation has been reviewed to determine exactly the contain-ment backpressure previously calculated by the LOTIC code when assuming initial containment lower compartment temperature to be 120*F. The pressure response included only a 2 second time interval below 1.85 psia and a minimum pressure of 1.84 psia. The LOCA analysis assumed a constant backpressure of 1.7 psia' which, therefore, included a minimum margin of 0.14 psi. Note that no credit was taken for the time (all except 2 seconds) that the LOCA backpressure was greater than 1.7 psia.

The original calculation of the effect of the 5'F temperature increase on back-pressure (-0.15 psi) was based upon the simple assumption that the entire containment free volume initial temperature increased from 120*F to 125*F.

In fact, only a change in the lower containment temperature need be evaluated.

A revised calculation based on the spatial post-LOCA containment temperatures shown in FSAR Figure 15.4.1-65 was performed. The result of this calculation is a potential containment backpressure reduction of -0.04 psi, rather than the -0.15 psi previously calculated. Since this value is less than the +0.14 psi margin which exists in the LOCA analysis, the existing LOCA analysis bounds the proposed increase in lower containment temperature.

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