Five valves involved in the Lacey Township, NJ, Oyster Creek Generating Station’s cooling system are undergoing an examination from federal regulators.
“The Oyster Creek nuclear power plant was shut down last night (Monday) in response to degradation of electromatic relief valves (ERVs) that has been identified,” said Nuclear Regulatory Commission (NRC) spokesman Neil A Sheehan said. “Five such valves are involved.”
Oyster Creek personnel replace the solenoid-operated valves that operate the plant’s five electromagnetic relief valves (EMRVs) during each refueling and maintenance outage. The solenoid valves then undergo testing in the maintenance shop to determine their condition.
“In late June, Oyster Creek staff tested five solenoid-operated valves that had been removed from the plant previously and determined that two of the five valves did not operate properly,” Sheehan said. “Oyster Creek staff disassembled the valves and identified more than expected wear on the solenoid-operating valve springs and support parts.”
Oyster Creek operators decided they needed a plant shutdown on July 7, to inspect the status of the currently installed solenoid operated valves associated with the EMRVs, Sheehan said.
The EMRVs and their associated solenoid valves are not accessible when the plant is in operation, he said.
NRC inspectors will independently assess the condition of the installed EMRV solenoid-operated valves once they are accessible during the current plant outage, Sheehan said.
The ERVs are part of the plant’s automatic depressurization system (ADS), which supports the emergency core cooling system. The ADS should depressurize the reactor during a small (pipe) break loss-of-coolant accident to permit the low-pressure core spray system to inject water into the reactor core, Sheehan said.
“Our resident inspectors assigned to Oyster Creek on a full-time basis have been closely following developments involving the evaluation of the valves and the decision to take the reactor off-line to address the issue,” Sheehan said. “They will continue to do so until the problem is satisfactorily resolved.”
The shutdown listed on the NRC’s “current events notification” page said:
“On July 7, 2014 at approximately [2040 EDT], an issue was discovered with currently removed Electromatic Relief Valves (EMRVs) that calls the operability of the currently installed EMRVs into question. Based on this new information, all 5 of the currently installed EMRVs were conservatively declared inoperable. With the potential of 5 EMRVs inoperable a Technical Specification shutdown is required under Technical Specification 3.4.b, whereby reactor pressure shall be reduced to 110 psig or less within 24 hours.”