LANL: The Corporate Story

Accident info must be shared
Suppressing details of reactor mishaps imperils workers, facilities

by Kyoichi Sasazawa, Yomiuri Shimbun Staff Writer (Mar. 30, 2007)

Following the revelation of a criticality accident at Hokuriku Electric Power Co.'s Shika nuclear power station in Shikamachi, Ishikawa Prefecture, it was brought to light recently that a criticality accident likely occurred at Tokyo Electric Power Co.'s Fukushima No. 1 nuclear power plant in November 1978.

The accident at the TEPCO plant occurred when control rods became dislodged, but the accident did not have any effect outside the plant, as was the case with similar control rod problems at other nuclear power plants.

Japan is the only country where two criticality accidents have been reported since the 1970s, when nuclear power generation was put into commercial use. Why were these extraordinary accidents covered up for such a long time?

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In addition to the two accidents in Japan that recently came to light, 60 criticality accidents have occurred here and in eight other countries, killing 21 people, according to a report by Los Alamos National Laboratory in the United States. These 21 victims include two who were killed in the criticality accident at JCO Co.'s nuclear fuel plant in Tokaimura, Ibaraki Prefecture, in September 1999.

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In one case, a criticality accident lasted for 37 hours. Why did a criticality accident last for so long at a light water reactor that was supposed to be very safe?

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Past criticality accidents include many that happened at nuclear development facilities such as Los Alamos National Laboratory and Oak Ridge National Laboratory, both in the United States, where secrecy is paramount. Even these organizations have disclosed details of accidents to prevent recurrence, ensure safety for workers and share information with others, according to a report from Los Alamos National Laboratory.

At a news conference last Thursday, TEPCO stressed its response to the accident was appropriate. "There was no institutional obligation to report such an accident at that time," an official said. But there remains a problem from the perspective of engineering ethics on sharing information on accidents with others.

According to a report by the Nuclear and Industrial Safety Agency, accidents and problems at Japan's nuclear power plants, which are supposed to be reported to the government, total about 30 a year. As many as 200 minor accidents that are not required to be reported occur each year--about 10 percent of the figure recorded in the United States.

"Regulation was different than it is today," said Prof. Kazuo Furuta of Tokyo University's graduate school, an expert in system quantum engineering. "They thought they were performing their jobs without problem, but actually they might have made a mistake inadvertently. We must consider the issue by stepping into the mind-set of engineers in those days."