The Deposition densities of radiocesium and the air dose rates in undisturbed fields around the Fukushima Dai-ichi Nuclear Power Plant; Their temporal changes for five years after the accident
| Autor: | Satoshi Mikami, Hideo Matsuda, Masaki Andoh, Takeo Suzuki, Shoji Sato, Hiroyuki Tanaka, Naotoshi Okuda, Ryuichi Sakamoto, Kimiaki Saito, Yoshifumi Hoshide |
|---|---|
| Jazyk: | angličtina |
| Rok vydání: | 2019 |
| Předmět: |
Water Pollutants
Radioactive 010504 meteorology & atmospheric sciences Health Toxicology and Mutagenesis 010501 environmental sciences Atmospheric sciences 01 natural sciences law.invention Japan law Radiation Monitoring Nuclear power plant Environmental Chemistry Fukushima Nuclear Accident Humans Soil Pollutants Radioactive Temporal change Waste Management and Disposal 0105 earth and related environmental sciences Background radiation General Medicine Human decontamination Pollution Original data Cesium Radioisotopes Deposition density Nuclear Power Plants Environmental science Dose rate Radioactive decay |
| Zdroj: | Journal of Environmental Radioactivity. 210:105941_1-105941_12 |
| ISSN: | 0265-931X |
| Popis: | The deposition densities of radiocesium and the air dose rates were repeatedly measured in a large number of undisturbed fields within the 80km zone that surrounds the Fukushima Dai-ichi Nuclear Power Plant site between 2011 and 2016, and features of their temporal changes were clarified. The average air dose rate excluding background radiation in this zone decreased to about 20\% of the initial value during the period from June 2011 to August 2016, which was essentially a result of the radioactive decay of $^{134}$Cs with a half-life of 2.06y. The air dose rate reduction was faster than that expected from the decay of radiocesium by a factor of about two, with most of this reduction being attributed to the penetration of radiocesium into the soil. The average deposition densities of $^{134}$Cs and $^{137}$Cs in fields that were not decontaminated were found to have decreased nearly according to their expected radioactive decay, which indicated that the movement of radiocesium in the horizontal direction was relatively small. The effect of decontamination was apparently observed in the measurements of air dose rates and deposition densities. Nominally, the average air dose rates in the measurement locations were reduced by about 20\% by decontamination and other human activities, of which accurate quantitative analysis is and continue to be a challenge. 2011年から2016年にかけて福島第一原子力発電所から80km圏内の撹乱のない多数の測定点で放射性セシウムの沈着量と空間線量率を繰り返し測定し、それらの経時変化の特徴を明らかにした。この地域のバックグラウンド放射線量を除いた平均空間線量率は、2011年6月から2016年8月までの期間中に初期の約20\%に減少した。これは主に$^{134}$Cs(半減期2.06y)の壊変の結果である。空間線量率の減少は放射性セシウムの壊変から予想されるものよりも約2倍早く、この減少の大部分は放射性セシウムの土壌への浸透によるものである。除染されていない土壌における$^{134}$Csと$^{137}$Csの平均沈着量は、ほぼ放射性壊変から予想されるペースで減少していた。すなわち水平方向の放射性セシウムの移動が比較的小さいことを示した。空間線量率と沈着量の測定結果では除染の効果が明らかに観察された。測定点の平均空間線量率は、その詳細な定量分析は今後の課題だが、除染やその他の人間の活動によって約20\%減少した。 |
| Databáze: | OpenAIRE |
| Externí odkaz: |
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