Development of Isotopic Dilution Mass-Spectrometry in Russia in Support of MC&A

Isotope dilution mass spectrometry (IDMS) is widely used to accurately determine U and Pu isotope and elemental concentrations in impure samples. The method is free from interferences causing systematic uncertainty of conventional titration methods and is the only accurate method for the assay of such complex mixtures as spent reactor fuel. However, IDMS requires special reference materials with certified isotopic composition and mass fraction of the element. V.G. Khlopin Radium Institute (KRI) being a member of the International Atomic Energy Agency’s (IAEA’s) Network of Analytical Laboratories (NWAL) has been using IDMS since the 1970s for determination of U and Pu in the IAEA inspection samples - both nuclear and environmental. For these purposes KRI has elaborated a number of reference materials (RM) with certified isotopic composition and/or element concentrations. Taking into account the experience gained at the KRI, the Program of Nuclear Material Control and Accounting (MC&A) sponsored by the U.S. Department of Energy has set the following tasks for the KRI: (a) to fabricate, certify and distribute a new batch of the Pu-242 isotopic spike, and (b) to formulate, test and certify the general IDMS procedure for measuring contents of U and Pu, to be applied at the analytical laboratories in Russia. This presentation will describe these two tasks providing detailed technical information about the Pu-242 spike and how the IDMS procedure is being developed and tested. Special attention is paid to the errors propagation and to their quantitative estimation.