The nation's top nuclear regulator cast doubt Thursday on whether reactors in the United States are prepared for the type of days-long power outage that struck a nuclear power plant in Japan.
The Nuclear Regulatory Commission has only required plants in this country to cope without power for four to eight hours. After that time, it assumes some electrical power will be restored.
NRC chairman Gregory Jaczko on Thursday questioned whether four to eight hours is enough time, even though it's unlikely a nuclear power plant would lose power from both the grid and emergency diesel generators as the Japan plant did. Requirements put in place after the Sept. 11 terrorist attacks could lengthen plants' ability to withstand a blackout.
"Four hours doesn't seem to be a reasonable time to restore offsite power if you lost the diesels immediately," Jaczko said at a commission meeting at the NRC's Rockville, Md., headquarters. "In the event there is a station blackout that is externally driven, I'm not convinced that in that situation four hours" is enough time to restore offsite power.
An Associated Press investigation last month examined the risk to the nation's 104 nuclear reactors to a complete loss of electrical power. In the United States, such a "station blackout" has only happened once, at the Vogtle Electric Generating Plant in eastern Georgia in 1990. There, power was restored in 55 minutes.
The Japan disaster showed that it could be days before the electricity needed to pump water and keep the radioactive core from melting can be turned back on. In Japan's case, the plant operator found other ways to cool the cores without onsite or offsite power.
Of the 104 nuclear reactors in the United States, 87 can cope for four hours in a blackout. Another 14 can cope for eight hours, and three can last for 16 hours.
Meanwhile, a top staffer told NRC commissioners Thursday that the Japan situation "has definitely improved" in recent weeks.
Bill Borchardt, NRC's executive director for operations, said that while there are still many unanswered questions about equipment failures and other problems at the facility, the situation is "certainly not as highly dynamic" as it was.