When the polar vortex's ultra-cold air moved into Pennsylvania Monday afternoon and plummeted to zero degrees, one of two nuclear reactors shut down at FirstEnergy Corp.'s Beaver Valley Nuclear Power Station in Shippingport and remains shut down.
Beaver Valley Nuclear Power Station is approximately 25 miles northwest of Pittsburgh.
"There are many potential reasons this could happen and the cold weather is one of them," FirstEnergy spokeswoman Jennifer Young said. "But there are hundreds of other causes we're considering."
Western Pennsylvania temperatures were in the mid-20s Monday and then dipped after noon.
Winter Storm Ion hit Pittsburgh bringing record low temperatures since Monday. It was minus-7 degrees there late Monday night, a record low for that date. It continued falling to minus-9 on Tuesday, another record.
The previous record low for Jan. 7 was minus-5, in 1884 and the all-time low of 22 degrees below zero was on Jan. 19, 1994.
The reactor shut down around 5 p.m. Monday when temperatures fell to about zero, according to the National Weather Service.
“It's too early to determine if the weather contributed to the transformer problem," Young said. "The plant remains offline as the team assesses the issue.”
'Safe and reliable'
Nuclear Regulatory Commission (NRC) spokesman Neil Sheehan called the shutdown "uneventful" and safe, but a fire suppression system was activated, dousing an electrical transformer with water, he said.
The transformer, that converts the reactor's power to electrical voltage, failed, so the reactor shut down and remains shut down.
This transformer is part of the generation part of the plant, not the nuclear portion, according to Young.
An investigation into the cause continues. The NRC's inspector at the plant is overseeing the FirstEnergy investigation, repairs, and the reactor's eventual return to service.
Sheehan said it could take several days, if the transformer needs replacing.
A spare transformer is on site in case a replacement is required, Young said, adding that replacement of the transformer would require a relatively short outage.
The company policy is to not disclose when the unit is expected to be back online due to competitive reasons.
The nuclear station shut down on Sept. 30 went off line for refueling and maintenance and did not go back online until Nov. 4.
"During the outage, 60 of the plant’s 157 fuel assemblies were exchanged," Electric Light and Power reported. "Numerous inspections and preventative maintenance and improvement projects were completed to ensure continued safe and reliable operations, including replacement of the unit’s two low-pressure turbines.
"The new, approximately 153-ton turbine rotors feature an enhanced blade design that is expected to increase plant efficiency."
Last year, Beaver Valley's Nuclear Station's on-site inspectors reported that the plant's security forces failed at least a portion of a force-on-force mock paramilitary attack on the plant in April. That was appealed and the company escaped citation.
In 2007, radioactive groundwater was detected at Beaver Valley Nuclear Power Station.
Sources: Elwood City Ledger, Electric Light and Power