The Oyster Creek Nuclear Generating Station in Lacey was forced to shut down for the second time in less than a week during the process of restarting after scheduled maintenance.
Officials with the federal Nuclear Regulatory Commission told Patch that workers at the plant manually shut it down at about 11:30 a.m. Sunday after observing that the main condenser was losing vacuum.
According to NRC officials, the condenser is operated in a vacuum condition to maximize heat transfer and efficiency.
The plant was being returned to service following scheduled maintenance last week and was about 20 percent powered when the shutdown occurred, the NRC said.
troubleshooting by Exelon Nuclear, the plant's operator, identified a 1-inch hole in an expansion
joint on piping from a relief valve for a reheater connected to the
main condenser, officials said. That defect allowed air to leak in, causing the vacuum condition in the condenser to degrade.
A resident NRC inspector visited the site after the shutdown and did not identify any concerns with the manner in which the operators responded to the condition or handled the shutdown, the NRC said.
Inspectors will continue to follow up on the event, "including the thoroughness of the repairs and the company’s root-cause evaluation," officials said.
The plant was first shut down last Monday to perform planned maintenance on a turbine speed controller, said plant spokeswoman Suzanne D'Ambrosio.