ML20156A223
| ML20156A223 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 06/04/2020 |
| From: | Christopher Hunter NRC/RES/DRA/PRB |
| To: | |
| Littlejohn J (301) 415-0428 | |
| References | |
| LER 1983-077-00 | |
| Download: ML20156A223 (1) | |
Text
LER 327/83-077 Event
Description:
Reactor Trip with Train A of Auxiliary Feedwater Unavailable Date of Event:
May 31, 1983 Plant:
Sequoyah 1 Summary Two days after a reactor trip, automatic control valve 1-PCV-3-122 in train A of the auxiliary feed water (AFW) system was declared inoperable due to failure to operate correctly. The failure was due to a clogged hydraulic valve and a worn hydraulic pump, which caused the motor to fail due to excessive current. Valve 1-PCV-3-122 is located in the discharge line of the motor-driven pump (MOP) in train A. Since this was inoperable, the train A MOP could not supply water to the steam generators.
The analysis assumed the valve was inoperable at the time of the trip, and train A was modeled in the analysis as failed. The analysis showed that the dominant accident sequence was the result of AFW failure. The conditional core damage probability was 9.8x10-6. The dominant accident sequence comprised 4.9x10-6 of this total, with four other sequences contributing an additional 4.9x10-6.