TOKYO (AP) – A nuclear watchdog has asked the operator of Japan’s wrecked Fukushima nuclear power plant to assess potential risks from damage found in a key supporting structure inside the worst-hit of the three melted reactors.
A robotic probe inside the Fukushima Daiichi nuclear power plant’s Unit 1 primary containment chamber found its pedestal – a main supporting structure right underneath the core – was largely damaged. The thick concrete exterior was missing almost all the way around, exposing the internal steel reinforcement.
About 880 tonnes of highly radioactive melted nuclear fuel remain inside the plant’s three reactors. Robotic probes have provided some information, but the status of the melted debris is still largely unknown.
Based on data collected from earlier probes and simulations, experts have said most of the melted fuel inside Unit 1, believed to be the worst hit, fell to the bottom of the primary containment chamber, but some might have fallen through into the concrete foundation – a situation that makes the already daunting task of decommissioning extremely difficult.
At a meeting on Wednesday of the Nuclear Regulation Authority, its commissioners agreed to order operator Tokyo Electric Power Company Holdings to urgently assess the risks from the pedestal damage, including possible leaks of radioactive substances from cracks and holes caused by the meltdown. The authority also requested that TEPCO assess potential risks if, in the event of another disaster, the pedestal fails to support the reactor.
“We need to think about responses in case of an accident,” watchdog commissioner Shinsuke Yamanaka told reporters. “TEPCO has a responsibility to make the risk assessment as soon as possible.”
TEPCO has said that, even though the concrete exterior is largely missing, the steel reinforcement remains intact and there is little safety risk.
If the pedestal fails, its surrounding structures can prevent the reactor from collapsing.
