Abstract

Symposium Sessions

Day 2, June 11（Tue.）　10:30-10:45　Room A (Convention Hall 300)

Uranium in nature consists mainly of three radionuclides: a radiogenic isotope 234U and two primordial nuclides 235U and 238U. Among them, 235U is a fissile isotope that has been used in nuclear bombs and nuclear reactors. When uranium is used for these purposes, 236U is produced by the 235U (n, γ) 236U reaction and the 238U (n, 3n) 236U reaction. Because the amount of anthropogenic 236U is significantly larger than that of natural 236U, 236U/238U has been used as an environmental tracer to investigate the contamination of anthropogenic uranium released from nuclear weapons tests, fuel reprocessing, nuclear power plant accidents, and the decommissioning of nuclear power plants. In this study, we examined the historical changes of 236U/238U and 235U/238U in environmental samples collected in Japan and elucidated the anthropogenic sources of uranium in the 1960s–2000s. In this presentation, I will discuss the possible sources of anthropogenic uranium in Japan.

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