TOKYO (AP) – A draft investigation report on the 2011 Fukushima nuclear meltdown, adopted by Japanese nuclear regulators on Wednesday, says it has detected dangerous levels of radioactive contamination at two of the three reactors, adding to concerns about the challenges decommissioning.
The interim report showed that the data collected by investigators showed that the sealing plugs placed above the isolation vessels of reactors no. 2 and 3 were contaminated as fatally as the remnants of nuclear fuel that had melted and fallen to the bottom of the reactors after the tsunami and earthquake of March 2011..
Experts said the bottom of the watertight stopper, a 12-meter (39-foot)-diameter triple-layered concrete disc-shaped lid placed above the main insulation vessel, is covered with high levels of radioactive Cesium 137.
Reactor cover no. 1 was less contaminated, probably because the plug was slightly removed and disfigured due to the impact of the hydrogen explosion, the report said.
Experts measured radiation levels at several locations inside the three reactor buildings and examined how radioactive materials moved and how safety equipment worked during the crash. They also said that the attempt to ventilate Unit 2 to prevent damage to the reactor never worked and that safety measures and equipment design have yet to be examined.
Contamination of the lid does not affect the environment, as the isolation vessels are closed inside the reactor buildings. The report did not provide further details on how the contamination of the cover would affect the progress of decommissioning or how it will affect.
The chairman of the Nuclear Regulatory Commission, Toyoshi Fuketa, called the findings “extremely serious” and said it would make it more difficult to dispose of molten fuel. He said figuring out how to remove the caps would be a major challenge.
Disposing of about 900 tons of molten fuel from three reactors is a daunting task that is expected to take decades, and officials have not been able to describe exactly when or how it could end.
The Fukushima plant was to begin removing the molten fuel from Unit 2, the first of three reactors, later this year before the crash’s 10th anniversary. But in December, Tokyo Electric Power Co.’s central operator. and the government have announced a delay until 2022. They said the development of a robotic arm to remove debris – a joint project with the UK – has been delayed due to the pandemic.
According to the current plan, a remote-controlled robotic arm will be inserted from the side of the reactor to reach the molten fuel mixed with the molten parts and the concrete floor of the reactor. Finally, lids should also be removed, but their contamination is a major obstacle.
The team of experts entered the areas inside the three reactors that were previously highly contaminated and inaccessible after the radiation level dropped significantly. They look for data and evidence before getting lost in the cleanliness.
Massive radiation from the reactors caused the evacuation of approximately 160,000 people around the plant. Tens of thousands are still unable to return home.
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