福岛核事故向环境释放的Pu研究进展

福岛核事故向环境释放的放射性核素中包含了锕系元素Pu,其中以极毒组的239Pu、240Pu和高毒组的241Pu为主。本文总结并分析了针对福岛核事故向环境释放的Pu的相关研究。据估计,福岛核事故向环境中排放的239+240Pu总量约为109 Bq,是切尔诺贝利核事故排放量的万分之一。此次事故排放的Pu同位素原子比(240Pu/239Pu和241Pu/239Pu)及活度比(A(238Pu)/A(239+240Pu))明显异于全球沉降值,可作为事故中Pu溯源的判定依据。事故所排放的Pu全部来源于核电站1~3号反应堆堆芯而非乏燃料池。现有研究报道的数据表明,在福岛核电站周围30km范围内的陆地环境中存在来自核事故排放的Pu污染,污染相对严重的"热点"区域和该地区与核电站的相对位置没有明显关联,主要是受地形和降水的影响。而对于人们关心的海洋环境,来自福岛核事故的Pu污染非常小。核事故向海洋中排放的Pu相对于核事故前海洋环境中的Pu污染水平可忽略不计。

Plutonium Isotopes Released from Fukushima Daiichi Nuclear Power Plant Accident into Environment

On March 11, 2011, a catastrophic tsunami induced by a magnitude 9.0 earthquake caused the terrible Fukushima Daiichi Nuclear Power Plant (FDNPP) accident, leading to the release of a large amount of radionuclides into the environment. The published studies on plutonium isotopes in the environment after the FDNPP accident were reviewed in this paper. The total atmospheric released amounts of Pu from the FDNPP accident were estimated to be 10⁹ Bq, that is only 1/10 000 of that released from the Chernobyl accident. The Pu isotopes were released from the damaged reactors, not from the spent fuel pools in the FDNPP. The Pu isotopic ratios (²⁴⁰Pu/²³⁹Pu, ²⁴¹Pu/²³⁹Pu) and activity ratios of A(²³⁸Pu)/A(^239+240Pu) were significantly different from that of global fallout, serving as powerful fingerprints for Pu source identification. To date, the plutonium isotopes from the accident in the terrestrial environment within the 30 km zone around the FDNPP site have been widely observed and there are no strong positive correlations between the Pu isotopes contamination levels and the distances from the FDNPP site. The influence of the FDNPP accident on Pu distributions in the marine environment is limited. No detectable Pu contamination from the accident is observed even in the near coastal (5 km off the FDNPP site) marine sediments.