BERWICK - Backup power generation systems at nuclear plants in the United States are similar to those at the Fukushima Daiichi nuclear plant in Japan that were overwhelmed or exhausted by the combined catastrophes of an earthquake and tsunami, but officials say additional safety redundancies at plants here help prevent a disaster.
Like the Japanese plant, most U.S. plants rely on diesel generators and then battery power to run cooling systems in the event that the primary power source is cut off.
Because the crisis at the Japanese plant is still unfolding, it is difficult to say exactly what failed and why - information that is necessary to determine any similar vulnerabilities in U.S. reactors. Reports suggest the twin natural disasters knocked out power in the main grid running the Japanese plant, the tsunami swamped the backup diesel generators and then battery power, meant only as a temporary measure, ran out leaving workers to scramble to keep the nuclear fuel submerged in cooling water.
A spokesman for PPL Susquehanna, the PPL Corp. nuclear plant in Salem Township Luzerne County, about seven miles north of Berwick, said the plant has a different design than the Japanese plant and too many unknowns about the crisis
make it difficult to compare the two plants' backup systems.
"I don't know what they lost and why they lost
it," spokesman Joe Scopelliti said. "There are no details out there."
PPL Susquehanna uses two, separate off-site power sources to run the plant, so if one is interrupted the other will still function, he said. If both off-site power sources failed, five diesel generators - one more than is required by regulators - would automatically switch on. Those generators operate independently of one another and are housed in a separate, hardened building to protect against earthquakes, tornados and floods. If the diesel generators failed, the plant has battery backup and a portable generator to recharge batteries.
The plant also has multiple sources of cooling water and a variety of differently powered pumps - steam, electrical and diesel-driven - to ensure cooling water surrounds the fuel, he said.
The diesel generators are tested monthly and operating crews train regularly on what to do if there is a loss of power to the system.
"They are trained to manage that," he said.
PPL has applied to the U.S. Nuclear Regulatory Commission for a license to build a third reactor near the two it operates near Berwick. A decision on the design of the reactor is not expected until 2013 and PPL will evaluate whether to build it only after its license is approved.
"We're still years away from a final decision on that," he said.
Diane Screnci, a spokeswoman for the Nuclear Regulatory Commission, said it is "too soon to say" if the events in Japan will have any impact on nuclear power plant applications that are currently under review by the agency.
More needs to be known about the causes of the problems in Japan to determine whether regulatory changes are necessary for U.S. plants.
"When the crisis is over, this will be studied extensively," she said.