Japan nuclear watchdog ask Fukushima plant operator to assess risk from reactor

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 tons 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.