ML19317F574

Final Deficiency Rept Re Safety Features Actuation Sys Diesel Overload.Manual Trip Buttons Replaced by seal-in Mechanical Trip Buttons to Provide Manual Trip Signal & Allow Sequencer to Properly Load Diesel

ML19317F574
Person / Time
Site:	Davis Besse
Issue date:	03/23/1977
From:	Roe L TOLEDO EDISON CO.
To:
References
244, NUDOCS 8001150895
Download: ML19317F574 (2)

Text

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Fec%es Devemornent March 23, 1977 moi nss s 42 Serial No. 244 Docket No. 50-346 Mr. James G. Keppler Regional Director, Region III Directorate of Regulatory Operations U.S. Nuclear Regulatory Commission 799 Roosevelt Road Glen Ellyn, Illinois 60137

Dear Mr. Keppler:

This letter is submitted in accordance with 10 CFR 50.55(e) as a final report regarding the Davis-Besse Nuclear Power Station Unit 1 Safety Features Actuation System (SFAS) manual initiation / emergency diesel generator sequencer design deficiency, which was reported by telecon between our Mr. E. C. Novak and your Mr. D. Hayes, on February 24, 1977.

Description of the Deficiency During the conduct of preoperational testing it was found that if the Safety Features Actuation System is manually initiated, and sometime later of f site power is lost, the emergency diesel generator loads would be applied all at one time and not sequentially loaded. This condition arose in part from the recently added loss of bus voltage reset signal supplied to the sequencer logic (re: 1/21/77 letter, Serial No. 189, Roe to Keppler) . With the emergency diesels running but not loaded from manual initiatien of SFAS, a loss of bus voltage resets the logic for the sequencer. The diesels would remain rucning in response to the low bus voltage condition but the sequencer vruld not be initiated because the momentary manual trip button no longer provides an SA signal to the sequencer. Thus, the diesel would close en the bus and all loads would be simultaneously connected which would everload the diesel.

Corrective Action Taken The momentary manual trip buttons are being replaced by mechanical seal-in type trip buttons. This will provide the necessary manual trip signal to allow the sequencer to properly load the diesels.

THE TOLEGO ECISON COMPANY EDISON PLAZA 3I w'WJ AVENUE TOLEDC. OHIO 43652 CAR 2 41977 (.9

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- Safety Implications The correction of the deficiency as described above prior to the operation of the facility assures that the health and saf ety of the public are not jeopardized.

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