The government ordered Tokyo Electric Power Co. on Thursday to reinvestigate 199 cases of data falsification and other irregularities at its nuclear plants in connection with state inspections.
Japan’s largest power utility will have to identify the causes of the irregularities and compile preventive measures by March 1 under the order based on related laws, the Nuclear and Industrial Safety Agency said.
The order follows Tepco’s admission Wednesday that it falsified data at its nuclear power plants to cover up problems during government inspections on 199 occasions between 1977 and 2002.
In one of the most serious cases, Tepco covered up a defect that emerged in 1992 in an emergency pump designed to cool down a reactor core during accidents at its Kashiwazaki-Kariwa plant in Kashiwazaki, Niigata Prefecture. It falsified data to make it look like the pump functioned properly so the plant would pass regular inspection.
Tepco reported the coverups Wednesday to the Nuclear and Industrial Safety Agency, which had ordered utilities last year to launch investigations following allegations that the firm and other power companies had falsified inspection data.
The 199 cases had been missed during a previous comprehensive check that followed Tepco’s 2002 admission that its inspection reports had been faked. That revelation forced the shutdown of all of the utility’s nuclear plants until their defects were repaired, a process that for some plants lasted more than a year.
Tepco claimed measures have been taken to address all the problems and they no longer pose any operational or safety risks.
According to the nuclear safety watchdog, a three-year statute of limitations has expired on all the coverups for criminal action to be taken against Tepco for obstructing inspections under the law governing the power industry.
The safety agency, a body under the Ministry of Economy, Trade and Industry, ordered Tepco to look into further details of the cases and submit a report on steps to prevent further coverups by March 1.
According to Tepco, the coverup at the Kashiwazaki plant took place in May 1992. A pump that comprises the emergency core cooling system failed on the evening of May 11, the day before the regular inspection by government officials.
Because inspectors usually check only the indication panels at the central control room, utility used a test-run mode for the inspection where a pump does not activate even if a switch is turned on and it passed the inspection, Tepco said.
Tepco operated the reactor for two days before it finally repaired the emergency pump, it added.
Other problems reported by Tepco included those at its Fukushima No. 1 and No. 2 nuclear plants. The utility also said data had been falsified at its thermal plants in Sodegaura, Chiba Prefecture, and in Kawasaki.