The operator of the Fukushima Daiichi nuclear power plant says extensive damage recently found in a support structure of the No.1 reactor would not cause the reactor to collapse, even in the event of a major earthquake.
A probe by the Tokyo Electric Power Company in March found that the pedestal, a cylindrical concrete structure supporting the reactor, had been severely damaged and that its steel reinforcing rods were exposed.
The finding prompted the Nuclear Regulation Authority to request the operator to study possible risks if the pedestal became unable to support the reactor.
The No.1 reactor and two others suffered meltdowns in the 2011 earthquake and tsunami.
At a meeting on Monday, the utility briefed NRA officials on its assessment of the risks, which was based on a simulation of a major earthquake with tremors measuring 900 gals.
TEPCO said the steel plate embedded in the damaged pedestal has enough strength to support the weight of the reactor, even if deterioration from the 2011 nuclear accident is taken into account.
The utility also said a structure designed to enclose the upper part of the reactor offers sufficient support against horizontal shaking.
But the NRA pointed out that details of the situation around the reactor remain unknown, and much of the assessment is based on assumed data. The nuclear watchdog plans to urge TEPCO to present more detailed data.