BUCHANAN, N.Y. - A problem with Indian Point Unit 2's main electrical generator caused the plant to automatically shut down at about 6 a.m. Wednesday.
The automatic shutdown did not cause any release of radioactive material, meaning there is no health hazard to area residents. The plant's other unit remains active, meaning there will be no disruption in power service either.
Plant officials said operators are addressing the problem, the cause of which had yet to be determined as of midday. The main electrical generator is powered by the pressurized water reactor's turbine, which produces electricity when the turbine is propelled by steam.
If there is a problem with the plant's turbine, reactor or generator, a shutdown is triggered by the plant's computer systems. Indian Point spokesperson Jerry Nappi said a timeline for when the plant will return to service will be available once operators determine what caused the shutdown.
"They're troubleshooting the generator to find out exactly what caused it to shut down; after they determine that, then they can estimate how long it would take to repair it," he said.
Neil Sheehan, a spokesperson for the Nuclear Regulatory Commission, said: "It's not a normal occurrence. These plants are designed to operate from one refueling outage to another, and those refueling outages generally occur every 18 months to two years."
"That's a significant part of the power production part of the plant," said Sheehan, who added more regulatory oversight is triggered by multiple unplanned shutdowns of nuclear power plants.
The NRC uses a running average to determine if a plant has had enough unplanned shutdowns to require more oversight. Each unplanned shutdown is counted as "one" in an ongoing, running average of 7,000 hours. During the course of those 7,000 hours, the whole number "one" gradually decreases toward zero.
This means the cumulative average of unplanned shutdowns would have to cross the "three" threshold before more regulatory oversight was triggered, Sheehan said.
Indian Point Unit 2's performance indicator, the average used to trigger regulatory oversight, was "0.0" before Wednesday's shutdown, which means Indian Point Unit 2 will not receive increase regulatory oversight as a result of Wednesday's unplanned shutdown.
Sheehan said a senior NRC inspector was on-site at the time of the shutdown, and the inspector "didn't identify any immediate concerns."
Indian Point Unit 2 has been in service 67 days since its most recent refueling, during which about one-third of its nuclear assemblies were replaced. Indian Point Unit 3 still is operating at full power.
Sheehan said Indian Point Unit 2's most recent unplanned shutdown occurred Nov. 7, 2010, when one of the plant's main transformers exploded.