Unrelated mechanical problems shut down three U.S. reactors over the past weekend.
Late on Friday, workers at Florida Power and Light's St. Lucie plant isolated a small leak in a safety injection tank outlet vent valve at unit 2, according to a report filed with the Nuclear Regulatory Commission. With the tank out of service, the unit was powered down per the plant's technical specifications shortly after midnight on Saturday.
That afternoon, operators at Dominion's Millstone plant in Connecticut shut down its no. 2 unit because of an issue with a turbine-driven auxiliary feedwater pump. The plant reported to the NRC that the reactor's technical specifications required the outage when troubleshooting could not determine the cause of low pump recirculation flow.
Then, on Sunday, operators manually tripped unit 1 at Southern Co.'s Plant Vogtle in Georgia. The plant reported to the NRC that operators noted a drop in steam generator water levels and the speed of a main feed pump during testing of the pump's trip mechanism.
All three shutdowns proceeded normally, and the units remained offline as of Monday morning, according to the NRC.