Tokyo Electric Power Co. said Friday that it had concealed an emergency shutdown of a reactor at its Fukushima Daiichi nuclear plant in 1984.
The utility also reported to the government that a criticality accident occurred in a separate reactor at the plant in 1978, changing its earlier claim that such an accident was “likely to have happened.”
Tepco is the second power company in recent days to acknowledge the occurrence of a self-sustaining nuclear chain reaction. Hokuriku Electric Power Co. did so on March 15.
Along with Tepco, 11 other power companies also reported to the Nuclear and Industrial Safety Agency, an arm of the Ministry of Economy, Trade and Industry, all the irregularities they have found in their probes since November under an order by Economy, Trade and Industry Minister Akira Amari.
According to a report by Tokyo Electric, the No. 2 reactor of the utility’s Fukushima Daiichi plant shut down in 1984 when a buildup of neutrons in the reactor was discovered as workers were preparing to start it.
Tokyo Electric claimed there were no injuries to workers or damage to the surrounding environment.
The utility said it deliberately chose not to report the incident to the nuclear safety watchdog.
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