It was revealed last week that Hokuriku Electric Power Co. failed to report a "criticality accident" at a nuclear-power plant in Shiga, Ishikawa Prefecture, eight years ago. The accident involved a 15-minute uncontrollable fission chain reaction.
The company's omission is outrageous. The accident in June 1999 could have led to an even more serious situation if some unlucky events had accompanied it. The revelation came after the government's Nuclear and Industrial Safety Agency called on power companies to complete by the end of this month an in-house investigation of power plant incidents involving possible data falsification and attempts to hide trouble or accidents.
The agency's action followed a series of revelations of irregularities since last year. This week, it was also reported that control rods slipped in Tohoku Electric Power Co.'s Onagawa plant in Miyagi Prefecture in July 1988, Chubu Electric Power Co.'s Hamaoka plant in Shizuoka Prefecture in May 1991, and Tokyo Electric Power Co.'s Fukushima plant in June 1993 and its Kashiwazaki Kariwa plant in Niigata Prefecture in April 2002. Still earlier similar accidents at three TEPCO plants also surfaced, one of them a criticality accident. What has been happening in the power industry further deepens people's distrust of nuclear-power plant operations.