By NORIHIKO KUWABARA/ Staff Writer
Exceedingly high radiation levels found inside crippled reactor buildings at the Fukushima No. 1 nuclear plant were labeled by nuclear regulators as an “extremely serious” challenge to the shutdown process and overall decommissioning of the site.
The Nuclear Regulation Authority (NRA) said a huge amount of radioactive materials apparently had attached to shield plugs of the containment vessels in the No. 2 and No. 3 reactors.
Radiation levels were estimated at 10 sieverts per hour, a lethal dose for anyone who spends even an hour in the vicinity, according to experts.
The finding would make it exceptionally difficult for workers to move the shield plugs, raising the prospect that the plan to decommission the reactors will have to be reassessed.
Toyoshi Fuketa, chairman of the NRA, noted that removing the highly contaminated shield plugs added to the enormous difficulty of retrieving nuclear fuel debris, the most daunting part of the decommissioning process.
“It appears that nuclear debris lies at an elevated place,” he said at a news conference earlier this month. “This will have a huge impact on the whole process of decommissioning work.”
TEPCO announced Dec. 24 that the removal of nuclear fuel debris will be postponed to 2022 or later, rather than the initially scheduled 2021, due to a delay in the development of equipment to carry out the work.