Pilgrim Nuclear Power Plant SRV inoperable due to suspected leakage in first stage

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Pilgrim Nuclear Generating Station is currently the only nuclear power plant operating in the United States Commonwealth of Massachusetts. It is located in the Manomet section of Plymouth on Cape Cod Bay, south of the tip of Rocky Point and north of Priscilla Beach. Like many similar plants, it was constructed by Bechtel, and is powered by a General Electric boiling water reactor and generator — a General Electric Mark I reactor of the same type and design as the Fukushima I Nuclear Power Plant.

On April 11, 1986 a recurring equipment problems force emergency shutdown of the plant. The resulting issue cost $1.001 billion.

Pilgrim keeps its spent nuclear fuel in an on-site storage pool, waiting for federal direction on the correct disposal process. The Yucca Mountain site in Nevada was being considered for this purpose until its deselection in 2009.

Pilgrim’s license to operate expires in 2012. An application for an extended operating license (until 2032) is under consideration by the Nuclear Regulatory Commission as of 2010.

Attorney General Martha Coakley is asking the US Nuclear Regulatory Commission to review the refusal of its licensing board to consider the impact of the recent nuclear disaster in Japan on relicensing procedures for the Pilgrim Nuclear Power Station in Plymouth.

During the Pilgrim plant’s relicensing process in 2006, Coakley said that an accident involving the spent fuel pool at Pilgrim could pose a significant risk to public safety and the environment and that the NRC should revise its regulations to address these risks, Coakley’s office said yesterday.

The Nuclear Regulatory Commission refused, saying the risks posed by spent fuel pools were insignificant, officials said.

Source: The Boston Globe

Power Reactor Event Number: 47553
Facility: PILGRIM
Region: 1 State: MA
Unit: [1] [ ] [ ]
RX Type: [1] GE-3
Notification Date: 12/26/2011
Notification Time: 16:00 [ET]
Event Date: 12/26/2011
Event Time: 12:50 [EST]
Last Update Date: 12/26/2011
Emergency Class: NON EMERGENCY
10 CFR Section:
50.72(b)(2)(i) – PLANT S/D REQD BY TS
Person (Organization):
Unit SCRAM Code RX CRIT Initial PWR Initial RX Mode Current PWR Current RX Mode
1 N Y 100 Power Operation 100 Power Operation

Event Text


“On Monday, December 26, 2011, at 1250 hours, with the reactor at 100% core thermal power, the station entered a 24-hour action statement to initiate a controlled shutdown and be less than 104 psig reactor pressure due to suspected leakage across the first stage of safety relief valve (SRV) RV-203-3D and subsequent declaration of the SRV inoperable due to criteria specified in Pilgrim plant procedure 2.2.23.

“As background; the Pressure Relief System includes four (4) SRVs and two (2) spring safety valves (SSVs). The SRVs discharge through their individual discharge piping, terminating below the minimum suppression pool (torus) water level. The four SRVs and the two SSVs are installed on the Main Steam piping in containment between the reactor pressure vessel and the flow restrictors.

“While at full power, indication of a steam leak across the first stage pilot of RV-203-3D was determined in accordance with criteria specified in procedure 2.2.23. Specifically, the SRV is inoperable if the pilot stage thermocouple temperature is 35 degrees F below its baseline temperature (with a lower decrease at the 2nd stage thermocouple) and cannot he explained by a corresponding downpower. The safety relief valve was subsequently declared inoperable and the Limiting Condition for Operation (LCO) for Technical Specification (TS) 3.6.D was entered. Due to the valve being declared inoperable, the station is required to be shutdown and reactor coolant pressure below 104 prig within 24 hours per T.S. 3.6.D.2.

“Currently, preparations are being completed to conduct the reactor shutdown and to initiate safety relief valve repairs.

“This event had no impact on the health and/or safety of the public.

“The USNRC Senior Resident Inspector has been notified.”

The safety-relief valves at Pilgrim are designed to be supplied, with other drywell instrumentation, from either the compressed air system or containment atmosphere control system (CACS). The CACS uses nitrogen for containment inerting. The supply for the safety-relief valves is provided from the CACS through an ambient air vaporizer and then through one of two parallel pressure regulators or a parallel bypass line.

The S/R valves at Pilgrim are two-stage, pilot-operated, dual-purpose valves designed by Target Rock Corporation in accordance with GE criteria for service application in the GE BWR main steam system. The two-stage S/R valve has been designed to replace the TR three-stage S/R valve that had a tendency to leak at the pilot valve and thereby keep the main disk from reseating. The replacement of the three-stage valves at Pilgrim was accomplished during the refueling outage that was completed in May 1980. The Pilgrim reactor has four of the two-stage S/R valves installed plus two spring-loaded safety valves.

Source: NRC Event Notifications

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