TOKYO (AP) – A draft investigation report on the 2011 crash in Fukushima, approved by Japanese nuclear regulators, says it has detected dangerously high levels of radioactive contamination at two of the three reactors, adding to concerns about the dismantling challenges.
The interim report states that the data collected by investigators showed that the seal plugs on top of the reactor safety vessels no. 2 and 3, were just as deadly contaminated as nuclear fuel debris that melted and fell to the bottom of the reactors after the March 2011 tsunami and earthquake.
According to experts, the bottom of the sealed stopper, a triple concrete disc-shaped lid with a diameter of 12 meters (39 feet) on top of the primary container, is covered with high levels of radioactive Cesium 137.
The number 1 reactor lid was less polluted, presumably because the plug was slightly knocked out of place and disfigured due to the impact of the hydrogen explosion, the report said.
The experts measured radiation levels at different locations in the three reactor buildings and investigated how radioactive materials move and safety equipment functions during the accident. They also said that the attempt at unit 2 to prevent damage to the reactor never worked and that safety measures and design of equipment have yet to be investigated.
The lid pollution does not affect the environment, as the containers are enclosed inside the reactor buildings. The report did not provide further details on whether or not the lid contamination would affect the dismantling progress.
The chairman of the Commission on Nuclear Regulation, Toyoshi Fuketa, called the findings “extremely serious” and said it would “make the removal of molten fuel” more difficult. ” He said figuring out how to remove the lids is a big challenge.
Removing an estimated 900 tons of molten fuel residues from three reactors is a daunting task that is expected to take decades, and officials could not describe exactly when or how it could end.
The Fukushima plant would begin removing molten fuel debris from Unit 2, the first of three reactors, later this year, ahead of the tenth anniversary of the crash. But in December, the plant company Tokyo Electric Power Co. and the government announced a delay until 2022. They said the development of a robot arm for debris removal – a joint project with Britain – has been delayed due to the pandemic.
Under the current plan, a remote-controlled robotic arm will be placed from the side of the reactor to access the molten fuel, mixed with molten parts and concrete floor of the reactor. Eventually the lids also need to be removed, but its contamination is a major setback.
The team of experts entered areas within the three reactors that were previously highly contaminated and inaccessible after radiation levels dropped significantly. They search for data and evidence before getting lost in the cleanup.
Massive radiation from the reactors caused about 160,000 people to evacuate from all over the plant. Tens of thousands still cannot return home.
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