ML19312C615

Notifies That Facility Emergency Power Sys Uses Two hydro-electric Generating Units & Single Unit Failure Will Have No Effect on ECCS Performance.Conclusions of 750709 Ansalysis Remain Valid

ML19312C615
Person / Time
Site:	Oconee
Issue date:	03/10/1976
From:	Parker W DUKE POWER CO.
To:	Purple R, Rusche B Office of Nuclear Reactor Regulation
References
NUDOCS 7912190809
Download: ML19312C615 (3)

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DATE OF DOCUMENT B.C. Rusche Charlotte, N.C.

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Corrinents on the re-evaluation of the ECCS Cool ing 1

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37F4053 March 10, 1976 Mr. Benard C. Rusche Director of Nuclear Reactor Regulation U. S. Nuclear Regulatory Commission Washington, D. C.

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Attention:

Mr. R. A. Purple, Chief Operating Reactors Branch No. 1 .,

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Re:

Oconee Nuclear Station Docket Nos. 50-269, -270, -287 g:

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Dear Sir:

- s; My letter dated July 9, 1975 described a re-evaluation of the ECCS cooling performance which had been accomplished for the Oconee Nuclear Station, Units 1, 2 and 3.

The model utilized in the performance of this re-evaluation is described in Babcock and Wilcox (B&W) non-proprietary Topical Report BAW-10104, "B&W's ECCS Evaluatica Model".

In non-proprietary Topical Report BAW-10103, "ECCS Evaluation of B&W's 177 FA Lowered Loop NSS", a description of the results of the re-eval-untion for a generic B&W unit of the Oconee class was presented. This analysis showed that Oconee Units 2 and 3 were conservative in relation to the generic analysis provided in BAW 10103.

In the case of Oconee 1, portions of the analysis presented in BAW 10103 were also performed utilizing specific Oconee 1 parameters and was included as attachment 2 to the July 9, 1975 submittal.

In Section 4.6 of BAW 10103 and Section 3.5 of the specific Oconee 1 analysis, the worst single failure postulated is the loss of a diesel, following loss of off-site power, which results in the operation of only one LPI and one HPI pump. The Oconee emergency power system uses two hydro-electric generating units instead of diesels and a single failure of one of these sources will have no effect upon ECCS performance.

However, failure of a 4160 volt switchboard could cause the loss of one HPI and one LPI pump, but there is no possibility of a common mode failure which will result in the loss of more than one 4160 volt switchboard.

Therefore, although the failure mechanism for the Oconee i

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. March 10, 1976 Page 2 units is different from that described in BAW 10103 and the specific Oconee 1 analysis, the worst case single failure still results in the operation of only one HPI and one LPI pump, and the conclusions of the analyses remain valid.

Ve truly yours, s.n L lb

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William O. Parker, Jr.

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