Unit 2 at Nine Mile Point in upstate New York is back online after the failure of an uninterruptible power supply prompted operators to shut it down last week.
The Valley News reported that the reactor returned to full power on Sunday afternoon following repairs and testing. It had been offline since March 4.
According to a report filed with the Nuclear Regulatory Commission, the reactor reduced its power output automatically when the UPS failed. Operators shut the unit down completely six minutes later when systems indicated a loss of cooling water to reactor recirculation pumps. During the event, a reactor building ventilation radiation monitor also stopped working when the building isolated in response to the failed UPS, according to the NRC, and a standby gas treatment system restored the reactor building differential pressure.
Constellation Energy, majority-owned by Exelon, runs two General Electric boiling water reactors that generate 1,990 megawatts at the plant near Syracuse, N.Y. On Feb. 16, an off-site event caused the loss of a 115 kilovolt line to the plant and resulted in the startup of emergency diesel generators at unit 2. The event preceded a feedwater level control lockup and affected gas and water monitoring systems, but the unit did not need to shut down while they were restored.