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HOME  > Past issues  > 2007 March 28 - April 3  > Electric power companies report 97 of irregularity cases at N-plant operations
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2007 March 28 - April 3 [SOCIAL ISSUES]

Electric power companies report 97 of irregularity cases at N-plant operations

March 31 & April 1, 2007
Electric power companies on March 30 submitted to the Nuclear and Industrial Safety Agency of the Ministry of Economy, Trade, and Industry the result of their internal investigation over concealing problems and data rigging at their power plants.

Concerning nuclear power plants, it was revealed that 97 cases of irregularity and concealment, including serious accidents endangering the public safety, had occurred.

On March 22, Tokyo Electric Power Co. disclosed a 7.5-hour criticality accident had occurred in the No. 3 reactor at its Fukushima No. 1 Nuclear Power Station on November 2, 1978.

TEPCO’s report on this accident stated that at that time its operator failed to realize for five hours what was actually happening and left it as it was.

At around 3 a.m., the operator on night shift noticed that the neutron detector showed an abnormally high number. But he did not imagine that the control rods had come off, and did nothing about it.

It was around 8 a.m. when the next shift team’s sub leader came in, read the neutron detector, and checked the position of the control rods. This is how they came to realize that the reactor had reached criticality. Around 10:30 a.m., they finally put back the control rods.

The operators falsified data by rewriting the plant’s day book to conceal the accident.

It was newly revealed that at the No. 2 reactor of the same nuclear power plant an emergency shut down device was activated during the regular inspection on October 21, 1984. Although the reactor was not operating at that time, it is believed that it temporarily reached criticality.

The daybook had no mention of the emergency shutdown.

With respect to a criticality accident that occurred at the Hokuriku Electric Power Co.’s Shika Nuclear Power Plant No. 1 reactor on June 18, 1999, the company failed to make public the accident because it was concerned about a possible delay in the start of construction of the No. 2 reactor scheduled for two months later.

The company also rigged records to conceal the accident.
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