Regulators plan to shut down a nuclear reactor run by Tokyo Electric Power Co. for one year due to the company’s manipulation of safety checks in the early 1990s, government officials said Friday.
It would be the longest suspension imposed on a commercial reactor and the most severe administrative penalty available other than nullification of an operating license.
The Nuclear and Industrial Safety Agency has found that the nation’s largest power utility manipulated checks on the airtightness of the No. 1 reactor at the Fukushima No. 1 nuclear plant in 1991 and 1992 and falsified reports.
The falsification of the checks on a critical safety element of reactor operations violates the Nuclear Reactor Regulation Law, and government sources said the way in which it was done was malicious.
But because a three-year statute of limitations already expired years ago, the nuclear agency will not file a criminal complaint against Tepco.
The suspension will be the first administrative punishment for Tepco after a string of scandals surfaced in August that during the 1980s and 1990s it falsified safety reports and covered up defects found in voluntary safety checks.
Authorities said covering up the results of the checks is more serious than the falsification of problems found during Tepco’s own checks because it involved a critical element of the reactor and was done during a regular inspection, where government inspectors are also present.
The nuclear regulatory agency will formally decide on the punishment after questioning of Tepco officials begins on Nov. 22.
Hitachi Ltd., which conducted the airtightness checks for Tepco, is investigating the matter and was expected to submit a report admitting wrongdoing to the agency, the sources said. The agency is also considering slapping Hitachi with an administrative punishment.
In the routine pressure check conducted at the No. 1 reactor of the Fukushima No. 1 nuclear plant in 1991 and 1992, nitrogen was injected into the container and air pressure was measured over a six-hour period to determine how airtight the unit was.
The container plays an important role in preventing radioactive materials from being leaked in the event of an accident.
On the two occasions in question, the pressure readings were unstable, so workers injected air into the container, which is 32 meters high and has a maximum diameter of 18 meters, to make it appear that pressure was being maintained, the sources said.
Tepco and Hitachi are at odds over who ordered the falsification and who actually injected the air, the sources said, adding the agency is looking into the details.
According to the nuclear agency, about 10 employees of Tepco and Hitachi were involved in the matter and all have admitted manipulating the tests and submitting falsified reports.
Harsh criticism arising from local communities in response to the latest scandal is expected to further delay Tepco’s program to build new reactors at the Fukushima No. 1 plant.
The firm’s plan to build the No. 7 reactor in 2008 and the No. 8 reactor the following year would be delayed by at least a year, according to a Tepco executive. It already has been postponed several times.