Isotope ratios determination of uranium in soil samples affected due to Chernobyl accident using thermal ionisation mass spectrometer

¹ National Institute of Radiological Sciences, Environmental Radiation Protection Research Group, 4-9-1 Anagawa, Inage-ku, Chiba 263-8555, Japan
² Department of Chemistry, University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan
³ Research Centre for Radiation Medicine, 53 Melnikova, 254050 Kiev, Ukraine

Abstract

A rapid and highly precise method was developed for the separation of uranium from soil samples for thermal ionisation mass spectrometry. The chemical separation procedure is based on the use of anion exchange resin and UTEVA extraction chromatography column. The isotope ratios of uranium, ²³⁴U/²³⁸U, ²³⁵U/²³⁸U and ²³⁶U/²³⁸U were measured by using a VG Sector 54 TIMS equipped with a Wide Aperture Retardation Potential (WARP) energy filter with a precision of better than 0.2% at two standard deviations (sd). The use of a WARP energy filter improves abundance sensitivity by an order of magnitude over a conventional VG Sector TIMS. Replicates of standard reference materials showed excellent analytical agreement with established values, supporting the reliability and accuracy of the method. Uranium isotopic compositions have been determined in soil samples in the exclusion zone of Chernobyl nuclear power plant. The isotopic composition of Chernobyl soil samples showed significant deviation from the natural uranium and the ²³⁶U/²³⁸U ratio varied from 10^-5 to 10^-4.