Isotopic composition of Uranium in soil and ground water samples collected around 30 km Chernobyl Exclusion Zone

Precise and accurate measurement of uranium isotope ratio is essential in environmental monitoring of any contamination in nuclear safeguards. 234U, 235U and 238U are naturally occurring alpha-emitting long-lived radionuclides, which are taken up daily at low levels with food and drinking. IUPAC has established natural isotopic composition of 235U/238U to be 0.00725. Therefore, isotope ratio measurements are important to provide information on the origin of uranium. The isotope ratios of uranium, 234U/238U, 235U/238U and 236U/238U were measured using a VG Sector 54 thermal ionization mass spectrometer (TIMS) as well as high resolution inductively coupled plasma mass spectrometry (ICP-MS) in soil samples as well as in some water samples collected in the exclusion zone of Chernobyl nuclear power plant. The isotopic composition of Chernobyl soil samples showed significant deviation from the natural uranium and presence of 236U is quite noticeable. The 234U/238U activity ratio varies in the range 1.06 to 2.1 and 1.42 to 5.75 for soil and water samples, respectively. Enrichment of 235U was also noticeable for soil as well as ground water samples.