NRC Questions Nuke Blackout Plans

Monday, May 2, 2011 @ 04:05 PM gHale


Of the 104 nuclear reactors in the United States, 87 can cope for four hours in a blackout, while another 14 can cope for eight hours, and three can last for 16 hours.

Those times were once acceptable, now, it may not be enough.

That thought process now comes into play after the nuclear crisis that is ongoing in Japan where there was a long-term power outage after an earthquake and tsunami struck and the reactors started to melt down.

The head of the Nuclear Regulatory Commission (NRC) late last week questioned whether reactors in the U.S. are ready for the type of days-long power outage that struck the Fukushima plant in Japan.

The NRC has only required plants in this country to cope without power for four to eight hours. After that time, it assumes the plant will be able to get electrical power restored. Not anymore.

NRC chairman Gregory Jaczko questioned whether four to eight hours is enough time, even though it’s unlikely a nuclear power plant would lose power from the grid and emergency diesel generators as the Japan plant did. Requirements put in place after the September 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.

The Japan disaster showed it could be days before anyone could turn the electricity on needed to pump water and keep the radioactive core from melting. In Japan’s case, the plant operator found other ways to cool the cores without onsite or offsite power.

As part of a review initiated after the Japan incident, the commission is looking at whether the blackout rule needs updating. At the time the NRC wrote the rule in the 1980s, the commission assumed a plant could get electrical power restored in 50 minutes to 2 hours. The NRC added an additional two hours to that time as a safety buffer.

Since then, plants have lost offsite power for longer periods of time. In every case, diesel generators kicked on and supplied electrical power, sometimes for days. There also are agreements with power grid operators that nuclear power plants get first priority in a restored power scenario.

“We have a high expectation you will restore offsite power, restore emergency diesels or use alternate sources,” said Pat Hiland, director of the NRC’s reactor regulation engineering division.

Jaczko pointed out that the blackout regulation should deal with a situation where even diesel generators don’t work, as in the case of the Fukushima Dai-ichi plant in Japan.



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