It has surfaced that Tokyo Electric Power Co. provided misleading information to the Diet investigation committee tasked to determine the causes of the March 11, 2011, nuclear catastrophe at Tepco’s Fukushima No. 1 nuclear power plant, thus preventing the examination of critical components of the No. 1 reactor, one of three Fukushima reactors that suffered meltdowns.

It is impossible to believe Tepco’s explanation that it had no intention of obstructing the committee’s work. The Diet should restart its investigation and Tepco should fully cooperate.

The committee had learned from eyewitness accounts by subcontract workers that, shortly before the reactor was hit by the March 11, 2011, tsunami, water was leaking on the fourth floor, where two isolation condensers (ICs) are located, of the building housing the No. 1 reactor. Isolation condensers turn steam vapor into water without using electricity and inject water into reactors to cool them by utilizing gravity in emergencies. The ICs in question stopped functioning shortly after the plant was hit by the 3/11 earthquake.

Suspecting that quake tremors might have broken the ICs and related piping, the committee scheduled an on-site inspection of the fourth floor for early March 2012. But in late February, the then head of Tepco’s corporate planning department showed Mr. Mitsuhiko Tanaka, a former reactor designer and a member of the investigation committee, a video taken during Tepco’s inspection of the ICs on Oct. 18, 2011. The planning department head explained that because the building was later encased to prevent radioactive materials from leaking, the inside of the building was dark enough to cause panic and that there was risk of injury from debris and of exposure to high radiation levels of 60 to 70 milisieverts per hour. As a result, the committee shelved the idea of conducting the on-site inspection.

Recently, however, it was found that the building’s encasement had been completed four days before the Tepco inspection video was made, that the encasement cover lets through some sunlight and that Tepco installed powerful mercury lighting on the fifth floor 10 days after the video footage was made. Thus it is clear that Tepco lied to the committee about the amount of light available inside the building. It seems fair to say that not only did Tepco treat the committee with derision, as Mr. Tanaka stated, but actively sought to disrupt the committee’s investigation.

While a government investigation committee ruled out the possibility that earthquake tremors had damaged the ICs, the Diet investigation committee has not. If it is found that quake tremors indeed damaged important components of the Fukushima nuclear power plant, the Nuclear Regulation Authority will be required to strengthen relevant post-Fukushima safety standards for nuclear power plants, which it is now in the process of writing.

Although the Diet investigation committee was disbanded in July 2012, the former committee members should proceed with their on-site inspection. If Tepco refuses to cooperate, the Diet should exercise its legal authority and reactivate the committee, then force Tepco to allow the inspection to take place.

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