ML20156A130
| ML20156A130 | |
| Person / Time | |
|---|---|
| Site: | Pilgrim |
| Issue date: | 06/04/2020 |
| From: | Christopher Hunter NRC/RES/DRA/PRB |
| To: | |
| Littlejohn J (301) 415-0428 | |
| References | |
| LER 1980-079-00 | |
| Download: ML20156A130 (4) | |
Text
PRECURSOR DESCRIPTION AND DATA NSIC Accession Number:
160926 Date:
October 31, 1980
Title:
Stuck Open Relief Valve at Pilgrim 1 The failure sequence was:
- 1. With the reactor at full
- power, a scram occurred due to main steam line high radiation.
- 2.
To control pressure, "C"
relief valve opened for 1 minute and closed successfully.
HPCI and RCIC were placed in full flow test.
- 3.
The MSIVs had closed during the event when the reactor depressurized beyond the MSIV closure set point of 880 psig.
The "D" relief valve was opened to reduce the reactor pressure enough to be able to reset the scram and reopen the MSIVs.
- 4.
The "D" relief valve stuck open.
- 5.
Repeated attempts to energize/deenergize the relief valve solenoid valve from the control room failed to close the "'D" relief valve and the plant depressurized to 20 psig.
Corrective action:
- 1.
The plant was shutdown and the valve assembly removed and tested.
The utility concluded that the probable cause of the failed valve was scoring on the main piston.
- 2.
A spare valve assembly and solenoid were installed and the unit was returned to service.
- 3.
The damaged valve was repaired.
Design purpose of failed system or component:
The pressure relief system provides overpressure protection for the RCS.
Reactor trip from Relief valves opened "D" relief valve sticks steam line radia-for RCS pressure open, resulting in RCS tion signal control depressurization to 20 psig Potential Severe Core Damage d
No - safety systems available for core cooling if required
'No No NSIC 160926 - Acutal Occurrence for Stuck-Open Relief Valve at Pilgrim 1
Potential Severe Core Damage Sequence No.
No Yes No Yes Yes Yes No Yes Yes Yes 1
2 3
4 5
6 7
8 9
10 NSIC 160926 -
Sequence of Interest for Stuck Open Relief Valve at Pilgrim 1
CATEGORIZATION OF ACCIDENT SEQUENCE PRECURSORS NSIC ACCESSION NUMBER:
160926 LER NO.:
80-079 DATE OF LER:
October 31, 1980 DATE OF EVENT:
October 1, 1980 SYSTEM INVOLVED:
Pressure relief system COMPONENT INVOLVED:
Relief valve CAUSE:
Mechanical failure in valve operator SEQUENCE OF INTEREST:
Main steam line break ACTUAL OCCURRENCE:
Stuck open relief valve REACTOR NAME:
Pilgrim 1 DOCKET NUMBER:
50-293 REACTOR TYPE:
BWR DESIGN ELECTRICAL RATING:
655 MWe REACTOR AGE:
8.3 years VENDOR:
General Electric ARCHITECT-ENGINEERS:
Bechtel OPERATORS:
Boston Edison Co.
LOCATION:
4 miles SE of Plymouth, Massachusetts DURATION:
N/A PLANT OPERATING CONDITION:
Full power TYPE OF FAILURE:
Inadequate performance DISCOVERY METHOD:
Operational event COMMENT: