@article{oai:repo.qst.go.jp:00043023,
 author = {Yoshida, Satoshi and Muramatsu, Yasuyuki and Tagami, Keiko and 吉田 聡 and 村松 康行 and 田上 恵子},
 journal = {Environmental Science & Technology},
 month = {},
 note = {In order to evaluate the impact of the 1999 criticality accident in Tokai-mura on the U isotope composition in soils, U isotopes (235U and 238U) were determined with inductively coupled plasma-mass spectrometry (ICP-MS) for soil core samples collected on the JCO grounds after the accident. The 235U/238U ratios were higher than the natural ratio in most samples. The highest ratio observed was 0.0262. Although vertical profiles of the 235U/238U ratio differed among the soil cores, the ratios tended to be high at the surface and decreased with depth. The U concentration also changed with depth. The percentages of 235U in the excess U, estimated from the positive correlation between U concentration and the 235U/238U ratio in soil samples, were less than 4 % by mass (mostly 1 - 3 %), and were much lower than the enrichment of the U used in the uranium conversion building at the time of the criticality accident (18.8 %). These findings indicate that enriched U had been released before the criticality accident during the U processing at JCO in connection with the reconversion of light water reactor fuel. Since the range of the U concentrations found was comparable to the range of uncontaminated Japanese surface soils, the amount of U added to the soil was judged negligible from a radiation protection viewpoint.},
 pages = {4174--4179},
 title = {Determination of uranium isotopes in soil core samples collected on the JCO grounds after the criticality accident.},
 volume = {35},
 year = {2001}
}