ML20065T584

Responds to NRC Re Adequacy of Station Electrical Distribution.Failure of Both Low Voltage Station Auxiliary Transformers Is Condition Described in Fsar,Chapter 7, Electrical Sys

ML20065T584
Person / Time
Site:	Point Beach
Issue date:	10/29/1982
From:	Fay C WISCONSIN ELECTRIC POWER CO.
To:	Clark R, Harold Denton Office of Nuclear Reactor Regulation
References
TAC-12955, TAC-12956, TAC-46522, TAC-46523, NUDOCS 8211020588
Download: ML20065T584 (2)

Text

o lHsconsin Electnc macoumr 231 W. MICHIGAN, P.O. BOX 2046, MILWAUKEE, WI 53201 October 29, 1982 Mr. H. R. Denton, Director Office of Nuclear Reactor Regulation U. S. NUCLEAR REGULATORY COMMISSION Washington, D. C. 20555 Attention: Mr. R. A. Clark, Chief Operating Reactors, Branch 3 Gentlemen:

DOCKET NOS. 50-266 AND 50-301 ADEQUACY OF STATION ELECTRICAL DISTRIBUTION POINT BEACH NUCLEAR PLANT, UNITS 1 AND 2 In a letter dated August 13, 1982, Wisconsin Electric was requested to show that a fire or similar catastrophe in or near one of the Point Beach Nuclear Plant low voltage station auxiliary transformers (lX04 or 2X04) and causing that transformer to be forced out of service could not cause the failure of the second low voltage station auxiliary transformer. The request was prompted by the resident inspector's observation that the 1X04 and 2X04 transformers are located in relatively close proximity to each other.

We have reviewed this situation and have concluded that the failure of both low voltage station auxiliary transformers is a condition that is bounded by the considerations and analyses presented in the Point Beach Nuclear Plant Final Safety Analysis l Report (FSAR) , Chapter 7, " Electrical Systems". The low voltage station auxiliary transformers are described in the FSAR as the first source of emergency power for each unit. No credit, however, is taken for these transformers as a safety-related power supply.

Since they are located outside the plant building and are not, I for example, specifically missile or seismically protected, the FSAR safety analyses do not assume the availability of these trans-( formers. The safety-related backup sources of emsrgency power l at the Point Beach Nuclear Plant are the two emergency diesel generator sets. Each emergency diesel generator is capable of sequentially starting and supplying the power requirements of one l

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Mr. H. R. Denton October 29, 1982 complete set of. safeguards equipment for one unit that is supplying the engineered safety features for the hypothetical design basis accident in that unit, and providing sufficient power to permit the second unit to be placed in a safe shutdown condition. These diesel generator requirements assume the loss of off-site electrical power.

We believe, therefore, that it is not necessary to show that a fire or similar catastrophe in one low voltage station auxiliary transformer cannot affect the other unit's low voltage station auxiliary transformer. In fact, because of their locations, we consider it unlikely that a complete analysis of potential accidents which might affect 1X04 or 2x04 would show that the same accident could not affect the other transformer.

However, as stated in the NRC (then AEC) Safety Evaluation Report for the Point Beach Nuclear Plant, we conclude that the AC auxiliary power system has adequate capacity and physical and electrical separation and no modifications regarding the 1X04 and 2X04 transformers are required or necessary.

Very truly yours, i

C Assistant Vice President l C. W. Fay Copy to NRC Resident Inspector i

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