Isotopic compositions of transuranic nuclides released by the Fukushima Dai-ichi Nuclear Power Plant accident: with emphasis on Cm isotopes

Isotopic composition of transuranic nuclides, with emphasis on Cm isotopes, were measured for environmental samples such as dust samples (black substances) from the roadsides and litter samples heavily contaminated by the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident. Low levels of ²³⁸Pu, ^239,240Pu, ²⁴¹Am, ²⁴²Cm and ^243,244Cm were determined by α-spectrometry after radiochemical separation. These results, including radioactive Cs, provided an isotopic data set. When the activity ratios among these transuranic nuclides were compared with those of core inventories (Units 1–3) in the FDNPP estimated by the JAEA group, fairly good agreement was found, indicating that traces of transuranic nuclides, probably in the forms of fine particles, were released into the environment without their large fractionations. The obtained data may lead to more accurate information about the on-site situation (e.g., burn-up, conditions of fuel during the release phase, etc.), which would be difficult to receive otherwise, and on the dispersion and deposition processes of transuranic nuclides and the behavior of these nuclides in the environment.