Radiation levels at Fukushima plant far worse than was thought（12/30/2020 The Asahi Shimbun日本朝日新聞）
最新測量解果顯示，日本福島一號核電廠受損反應爐的廠房放射性輻射濃度遠比原先估計的來得更高，工作人員只要在接近反應爐附近區域待一個小時，就會立即致命！原本預期在今年展開的反應爐廢爐清汙除役作業再度向後延遲。
日本朝日新聞專題報導指出，最新的現場輻射濃度測量解果顯示，福島一號核電廠因發生氫爆導致核燃料熔燬而嚴重毀損的２號及３號反應爐所在的核島區環境中的放射性輻射濃度，即便是在核災發生十年之後，依舊高得驚人，輻射濃度甚至遠比原先估算的還要高出許多，人類只要在鄰近反應爐廠房的附近區域待超過一個小時，就會立即喪命。
福島核災十年了, 福島核電廠2,3號機輻射遠高過預期, 人員難以接近，即便是使用機械手臂也因超高的輻射線影響，使得機械工具的使用壽命異常短暫，根本無法正常作業，想要拆除反應爐並清除廠房內的高放射性污染廢棄物以及融化的核燃料棒殘渣，比原先預測的來得困難太多。
日本政府的原子力規制委員會（Nuclear Regulation Authority (NRA) ）指出最新量測到的反應爐廢墟周遭存在的超高濃度放射性輻射線對於福島一號核電廠廠區整體的除役以及除污復原工作造成“極端嚴重的挑戰”。
日本政府的原子力規制委員會（Nuclear Regulation Authority (NRA) ）指出在如此巨量的放射性輻射污染環境到附近待超過一個小時，人類就會因接觸過量輻射而致死，因此日本原子力規制委員會認為反應爐廢墟現場的實際狀況比早先擬定的除役清污計畫所想訂的還要還要艱困許多，因此原先擬定的廢爐除役清污計畫勢將需要重新評估重擬。
基於最新測得的環境輻射濃度測量結果，以及廢爐除汙機械設備開發的進度比原先預估的時程發生延誤，日本東京電力在去年（2020）12月24 日宣布原先預定要在今年（2021）展開的反應爐廢墟清除熔燬的核燃料棒殘骸、碎片的除汙工程，將再度順延到2022年甚至更晚的時程。
Radiation levels at Fukushima plant far worse than was thought（12/30/2020 The Asahi Shimbun日本朝日新聞）
（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.”
A shield plug, made of reinforced concrete, is circular in shape and measures about 12 meters in diameter.
It has a triple-layer structure, with each layer about 60 centimeters thick. It is placed above the containment vessel like a lid on the top floor of a reactor building.
The shield plug blocks radiation from the reactor core at normal times.
When nuclear fuels need to be replaced, workers remove a shield plug to gain access to the interior of the containment vessel.
In a study that resumed in September after about a five-year hiatus, the NRA carried out fresh measurements of radiation levels in the vicinity of the shield plugs of the No. 2 and No. 3 reactors.
The study was undertaken following investigations by Tokyo Electric Power Co., operator of the plant, and other entities, which had shown extraordinary levels of radiations there.
The NRA’s study found that the amount of radioactive cesium 137 was estimated at 20-40 petabecquerels between the space between the top and middle layers of the shied plug of the No. 2 reactor.
That works out to more than 10 sieverts per hour based on readings of radiation levels nearby. Radiation at such levels can kill a person if they are exposed for an hour, according to experts.
The estimated figure was 30 petabecquerels for the No. 3 reactor.
In the triple meltdown triggered by the 2011 earthquake and tsunami disaster, the shield plug of the No. 1 reactor slipped out of place and was damaged by a hydrogen explosion that occurred at the reactor building.
As larger amounts of cesium 137 leaked from the No. 1 reactor through the damaged plug, the amount of the radioactive material attached to its shield plug was estimated at 0.16 petabecquerels, considerably lower than for the No. 2 and No. 3 reactors.
In contrast, the shield plugs for the No. 2 and No. 3 reactors remained relatively unscathed, blocking a huge amount of radioactive substances that leaked from their containment vessels from escaping into the atmosphere, according to the NRA.
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.
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Radiation levels at Fukushima plant far worse than was thought（12/30/2020 The Asahi Shimbun日本朝日新聞）
http://www.asahi.com/ajw/articles/14071742
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