ML20147A484

Final ASP Analysis - Calvert Cliffs 1 (LER 317-83-046)

ML20147A484
Person / Time
Site:	Calvert Cliffs
Issue date:	08/16/1983
From:	Christopher Hunter NRC Region 1
To:
Littlejohn J (301) 415-0428
References
LER 1983-046-00, LER 1983-049-00
Download: ML20147A484 (1)

Text

LERs 317/83-046 and -049 Event

Description:

One EDG and One AFW Turbine-Driven Pump Inoperable Date of Event: August 16, 1983 Plant: Calvert Cliffs 1 Summary On August 16, 1983 during normal operation, emergency diesel generator (EDG) 12 shut down on a loss of fuel oil during the performance of a surveillance test. It was determined that this condition existed from August 10-16, 1983. The cause of the fault was a personnel error which occurred on August 10. Procedures were not followed, which resulted in the lower level switch isolation valve being left shut after testing. On August 18, 1983 while post maintenance testing was being carried out on the flow path from the condensate storage tank, auxiliary feedwater (AFW) pump 11 was found to be inoperable due to bound-up stage piece and shaft piece balances.

Since it is not known how long the AFW pump was inoperable, and the EDG was determined to have been faulty for six days, this event was modeled as an unavailability of the turbine-driven AFW pump 11 and , EDG 12 with a postulated loss of offsite power (LOOP) for six days (144 hours0.00167 days <br />0.04 hours <br />2.380952e-4 weeks <br />5.4792e-5 months <br />).

All associated system trains that rely on EDG 12 for emergency power were set to unavailable.

Since the motor-operated AFW pump does not rely on EDG 12 but relies on EDG 11, it was assumed to be operable. The increase in core damage probability (CDP), or importance, over the duration of the event is 5.8x10-6. The base-case CDP over the duration of the event is 7.1x10-7 resulting in an estimated conditional core damage probability of 6.5x10-6. The dominant sequence involved a postulated LOOP with failure of emergency power (station blackout) and failure of AFW given the loss of emergency power.