TEPCO exec says he knew standards for judging meltdown before Fukushima disaster

An acting general manager at Tokyo Electric Power Co. (TEPCO), owner of the crippled Fukushima No. 1 Nuclear Power Plant, said April 11 that he was aware of standards in a company manual for ascertaining meltdowns before the outbreak of the Fukushima disaster in 2011 -- conflicting with the company's statement that no one noticed the existence of standards.

The disclosure was made by Yuichi Okamura, an acting general manager with TEPCO's on-site nuclear power division. TEPCO announced in February, almost five years after the outbreak of the disaster, that a manual containing criteria for judging nuclear reactor core meltdowns had been discovered. The company is likely to face criticism now that an official at the utility has acknowledged he was earlier aware of the standards.

The standards define a core meltdown as a situation in which over 5 percent of the core of a reactor has been damaged.

At a regularly scheduled news conference on April 11, Okamura said, "I learned the standards while working for around 20 years within the company." He said that at the time of the disaster, he was handing restoration work, including at a water processing facility, and wasn't in a position to determine that there had been a core meltdown.

Okamura said he realized that the issue over whether standards existed or not was being viewed as a problem in the company after he took charge of news conferences in August last year. This conflicts with TEPCO's explanation that "Over a period of five years until February this year, no one was aware of the standards."

Going by the standards, TEPCO could have judged that there had been core meltdowns three days after the outbreak of the March 2011 disaster. But following simulations, it was not until two months later that the company admitted the meltdowns.

The company is probing the matter with a third-party committee, focusing on the handling of the manual and how it was "discovered."