ML20156A129

Final ASP Analysis - Pilgrim (LER 293-80-069)

ML20156A129
Person / Time
Site:	Pilgrim
Issue date:	06/04/2020
From:	Christopher Hunter NRC/RES/DRA/PRB
To:
Littlejohn J (301) 415-0428
References
LER 1980-069-00
Download: ML20156A129 (4)

Text

Accession Number: 160497

October 20, 1980 Inadvertent Opening of Safety Relief Valve at Pilgrim 1 failure sequence was:

Operating pressure in the nitrogen supply line to the solenoid valve that operates the safety relief valve was in excess of the design specifications for the solenoid valve, resulting in leakage through the solenoid valve seat into the diaphragm of the safety relief valve.

The reactor was operating at steady state at 95% power. At the associated high reactor pressure, the leakage through the valve seat was enough to lift the relief valve.

The reactor was manually scrammed.

Attempts were made to close the relief valve, per operating procedures, which entailed switching the valve to the open position (which opens the nitrogen supply valve) and then to the closed position.

The high nitrogen pressure (160 psi) delivered when the nitrogen supply valve opened, was above the set point (135 psi) at which the solenoid valve could respond to a "close" signal when the reactor is pressurized.

The relief valve remained open until the reactor depressurized.

The unit was successfully taken to cold shutdown.

rective action:

Operation at reduced nitrogen supply pressure (110 psi) was to be implemented.

Station procedures were to be revised to require an operator verification check of nitrogen pressure once per shift.

gn purpose of failed system or component:

The nitrogen system provides control gas to actuate the opening and ing of reactor relief valves upon automatic control demands as well manual demands.

The reactor relief system provides overpressure protection for the

er opens due to N2 system manually to close the valve Severe pressure exceeding tripped results in valve Core design specs for stuck open Damage relief valve operators No - reactor success-fully shut down No No - auto scram and safety injection available No 60497 - Actual Occurrence for Inadvertent Opening of Safety Relief Valve at Pilgrim 1

Coolant Control Cooling zation Response Core Core Accident Initiated Provided System Adequate Cooling Damage j Operates No 1 Yes 2 No 3 Yes 4 Yes 5 Yes 6 No 7 Yes 8 Yes 9 Yes 10 NSIC 160497 - Sequence of Interest for Inadvertent Opening of Relief Valve at Pilgrim 1

O.: 80-069 F LER: October 20, 1980 OF EVENT: October 7, 1980 INVOLVED: Pressure relief system ENT INVOLVED: Relief valve Excessive nitrogen pressure to valve operator CE OF INTEREST: Main steam line break OCCURRENCE: Stuck open relief valve R NAME: Pilgrim 1 NUMBER: 50-293 R TYPE: BWR ELECTRICAL RATING: 655 MWe R AGE: 8.3 years

General Electric ECT-ENGINEERS: Bechtel ORS: Boston Edison Co.

ON: 4 miles SE of Plymouth, Massachusetts ON: N/A OPERATING CONDITION: Full power F FAILURE: Design basis event ERY METHOD: Operational event T: All safety systems were available. See Accession No. 160559 for a similar event at Pilgrim 1 (50-293, LER 80-080, Nov. 14, 1980) but with a different cause.