ML20149K481

Final ASP Analysis - North Anna 2 (LER 339-82-061)

ML20149K481
Person / Time
Site:	North Anna
Issue date:	05/28/2020
From:	Christopher Hunter NRC/RES/DRA/PRB
To:
Littlejohn J (301) 415-0428
References
LER 1982-061-00
Download: ML20149K481 (1)

Text

LER 339/82-061 Event

Description:

Transient with One Low-Pressure Safety Injection Pump Inoperable Date of Event: September 5, 1982 Plant: North Anna 2 Summary On September 5, 1982 during normal operation, the containment sump suction valve of low-pressure safety injection (LPSI) pump 1A failed to open during a periodic surveillance test. The valve hand wheel, which is connected to the valve with a flexible extension from the first level of the safeguards area to the bottom of the valve pit, could not be moved. Investigation revealed that the flexible extension had been wrapped with a power cord by maintenance personnel, which prevented the extension's rotation. A plant trip occurred on August 22, 1982, 14 days prior to the discovery of the valve fault (NUREG-0020).

This event was modeled as a transient with one LPSI pump residual heat removal (RHR train) assumed to be failed. Since high-pressure recirculation (HPR) relies on these pumps as well, one train of HPR was also set to failed. The estimated conditional core damage probability for this event is 1.1x10-6. The dominant sequence was not affected by the branch probability modifications. The dominant sequence involved the failure of auxiliary feedwater, main feed water, and feed and bleed.