It appears that the Exelon (NYSE:EXC) Oyster Creek nuclear plant and the Public Service Enterprise Group (NYSE:PEG) Salem 2 unit are both returning to service.
Oyster Creek was listed at 40% generating capacity and Salem 2 was listed at 45% generation on the Nuclear Regulatory Commission (NRC) daily reactor status report on July 15.
Both nuclear units are located in New Jersey. Oyster Creek is a single-unit 630-MW boiling water reactor (BWR) commissioned in 1969. Salem 2 is a roughly 1,150-MW pressurized water reactor (PWR) that was commission in 1981. There are two twin PWRs at the PSEG Salem station. Salem 1 was commissioned in 1977.
Salem 2 has been down for a scheduled refueling and maintenance outage that started April 12. It ended up running longer-than-expected.
During the outage, eight reactor coolant pump (RCP) turning vane bolt heads were recovered from the reactor coolant system (RCS), the primary system of water that cools the reactor core. Several bolt heads had previously been recovered during the prior two refueling outages, PSEG said in a statement. Salem Unit 2 has four RCPs that pump water to the reactor core with each pump having a turning vane attached by 20 turning vane bolts for a total of 80 bolts.
Based on the operating history of the four pumps, there had been no change in performance indicating potential degraded performance of the RCPs and their ability to pump water through the reactor coolant system. However, based on the accumulated number of bolts found during this outage, PSEG Nuclear management made a decision to extend the outage to further examine and make repairs as needed to the four RCPs.
Working with nuclear vendors Areva and Westinghouse, the four pumps were removed and shipped offsite for inspection and repairs. During the inspection, it was determined that bolting on all four pumps had experienced inter granular stress corrosion cracking which had led to the broken bolt heads. Per the recommendation of original RCP manufacturer Westinghouse, a different grade stainless steel bolt that is less susceptible to this type of failure was installed as part of repairs.
By comparison, Salem 1 has not identified any loose bolt heads to date. That unit’s four RCPs are a slightly different design with 24 turning vane bolts (compared to 20 bolts in Salem 2) measuring one and a half inches in diameter (compared to one inch in Salem 2). Due to this design difference, the Salem 1 bolts were initially torqued to a lower value thereby reducing the stress and susceptibility to inter granular stress corrosion cracking, PSEG said.
“The past several weeks have been a trying time for our employees and I could not be more proud of their efforts,” said Bob Braun, senior vice president and chief operating officer for PSEG Nuclear. “Removing, repairing and successfully returning four reactor coolant pumps to service is unprecedented.”
Exelon’s Oyster Creek was taken offline July 7 to support inspections and replacement of a piece of safety equipment that operates valves located inside the drywell.
Exelon plans to close Oyster Creek by the end of 2019.
V.C. Summer should be back up later in the month
Meanwhile in South Carolina, the SCANA (NYSE:SCG) V.C. Summer unit 1 is listed at zero generation.
“On Sunday afternoon [July 13], plant operators and monitoring systems at V.C. Summer Nuclear Station detected that a relief valve was not working properly,” a company spokesperson told GenerationHub in an email.
“Although still within operating limits, management made the conservative decision to shut down the plant to inspect and replace the valve. The timeframe for returning the plant to power operation is under review but is expected to be 14 days or less. This issue poses no threat to public safety or the environment,” the spokesperson said.
V.C. Summer is a 1980s vintage BWR with a capacity of about 1,000 MW. SCANA is targeting 2017 for replacement of the reactor vessel head at the V.C. Summer 1 nuclear unit in Fairfield County, S.C. Two new nuclear units are also under construction at the Summer nuclear station.