Mass spectrometric analysis of uranium and plutonium and its applications in nuclear fuel cycle

Mass spectrometric analysis of uranium and plutonium which is of great importance at various stages in the nuclear fuel cycle is discussed. The measurement of isotopic abundances of uranium and plutonium isotopes by thermal ionisation mass spectrometry is found to be reliable in the abundance range of 0.01 - 100%. The precision and accuracy achievable are functions of the isotopic abundance and vary from 5% at 0.01% abundance to better than 0.2% at 50% abundance. Isotope dilution analysis using mass spectrometric techniques being highly sensitive, selective, accurate and free from diverse ion effects is universally accepted for concentration measurement of uranium and plutonium especially in irradiated fuels. To achieve the precision and accuracy commensurate with the capability of this technique, various critical steps like sampling at the input point of a reprocessing plant, spiking procedures and chemical exchange between the sample and spike isotopes are discussed. Various international intercomparison experiments are being conducted from time to time to evaluate the various procedures and the overall precision and accuracy achievable in actual practice. Typical results of such experiments done at the Radiochemistry Labs in BARC, India are presented. (auth.)