Detection of 236U and variation of uranium isotope composition in the soil samples affected by the JCO criticality accident

Uranium affected by criticality accident which occurred at the JCO in Japan was chemically separated and its isotopic composition was measured using a thermal ionisation mass spectrometer. Chemical separation of uranium was carried out by anion exchange resin and UTEVA extraction chromatography. Radioactive dis-equilibrium of 234U/238U and enrichment of 235U/238U were noticed in some soil samples. Presence of 236U produced by the accident was detected in the samples examined.