@article{oai:repo.qst.go.jp:00058659,
 author = {Zheng, Jian and Tagami, Keiko and Aono, Tatsuo and Uchida, Shigeo and 鄭 建 and 田上 恵子 and 青野 辰雄 and 内田 滋夫},
 journal = {Actinide Research Quarterky},
 month = {Nov},
 note = {The Fukushima Daiichi Nuclear Power Plant (FDNPP) accident led to the release of large amounts of radionuclides into the environment. In addition to the atmospheric releases, the release of highly contaminated water from the damaged reactor buildings resulted in the direct discharges of radionuclides into the sea. It has been estimated that the total amount of 137Cs released from the FDNPP accident ranged from 15-35 PBq, while for the refractory actinides, in particular, Pu isotopes, tiny amount (2x10-5% of the core inventory) was released into the environment.1-4 Released radioactive materials posed radiation threat to human society and ecosystems. Thus, source identification of radioactive contamination and long-term environmental behavior of released radioactive materials are important issues of study after the FDNPP accident. 
For Pu isotopes, it is difficult to estimate the contamination caused by the FDNPP accident if only Pu activity measurement is conducted due to the fact that only tiny amount of core Pu was released. Experience obtained from studies on Pu contamination in the Chernobyl accident and other global and/or regional Pu contamination events indicated that accurate determination of Pu isotopic composition (in particular 240Pu/239Pu and 241Pu/239Pu atom ratios) is essential for reliable source identification. This study will focus on the distribution of Pu isotopes in the terrestrial environment and the marine environment following the Fukushima nuclear accident and identification of the contamination sources of Pu isotopes.},
 pages = {9--12},
 title = {Plutonium isotopes enter the environment as a result of the accident at the Fukushima Daiichi nuclear power plant},
 year = {2016}
}