U.S. Reactors Unprepared for Total Power Loss, Report SuggestsBy MATTHEW L. WALD
Nuclear safety rules in the United States do not adequately weigh the risk of a single event that would knock out electricity from the grid and from emergency generators, as a quake and tsunami recently did in Japan, officials of the Nuclear Regulatory Commission said Wednesday.
A crucial reason for the extensive damage to the Fukushima plant’s reactors was the loss of electricity needed to run water pumps and to reposition valves. The American nuclear industry has argued in recent months that its reactors are better prepared to cope with that kind of emergency.
But Charlie Miller, the chairman of the task force, said that studies by safety experts in the United States had analyzed the risk of losing electricity from the grid or from on-site emergency generators, but not both, conducting separate studies on those scenarios.
Steve Kraft, an executive of the Nuclear Energy Institute, the industry’s trade association, who was in the audience on Wednesday, said that in the past, it was “not considered credible” that a single event could knock out both supplies. In view of recent events in Japan, he said in an interview, it was time to prepare for the possibility of an extended blackout.
One of the commissioners, George Apostolakis, pointed out that existing safety analyses also assume that electricity would be restored within four or eight hours after a power cutoff, but that blackouts on the grid often last far longer. “Why do we still assume things that are now, in retrospect, unrealistic?’’ he asked.
The task force, appointed in April, is supposed to complete its investigation in August, but is periodically updating the commission. In another finding, it warned that emergency vents that have been added to American reactors m to protect against a hydrogen explosion after an accident might not function, just as they proved inoperable in Fukushima.
“It may be a challenge to open the vent path in a scenario like the Fukiushima accident,’’ said Mr. Miller, who said that the types of valves used, and their accessibility in the event that they had to be operated manually, needed further evaluation.
Another challenge is that the commission’s inspectors have not been trained to evaluate the condition of a variety of hardware or review procedures that were adopted as extra precautions after the 9/11 attacks. “We do not have the same kind of regulatory oversight on those enhancements,’’ said R. William Borchardt, the commission’s executive director for operations.
The commission’s staff, which has been trying to obtain information about the Fukushima reactors, has also revised its view of the condition of a pool of spent fuel at the plant’s Unit 4 reactor, Mr. Borchardt said Wednesday.
An assumption that that pool was dry or nearly dry, raising the possibility of a massive release of radioactive materials, led the United States ambassador to Japan to recommend that Americans stay 50 miles away from the plant. The Japanese authorities had ordered evacuations of people within about 12 miles of the plant.
“It’s unlikely that the pool ever went completely dry,’’ Mr. Borchardt told the commissioners.
“The staff welcomes this as very good news, as it’s one indication that the event may not have been as serious as previously believed for Unit 4.” He said the conclusion was based on a recent video of the pool.
The commission has never revealed why its chairman, Gregory B. Jaczko, stated this spring that the pool was empty or nearly empty. But since the March 11 accident at Fukushima, the plant’s owner, Tokyo Electric Power Company, has reported a variety of instrument readings that later came into question.