An inter-calibration campaign using selected uranium isotopic reference materials

Abstract

Isotope dilution mass spectrometry (IDMS) is one of the most widely applied techniques for the measurement of uranium and plutonium amount content in nuclear safeguards, especially when accurate results with small uncertainties are required. Intrinsic to IDMS is the use of certified isotopic reference materials; so-called spike CRMs. Reference materials with certified amount content and isotope ratios are indispensable for instrument calibration and method validation. Their fundamental role is to establish traceability of the measured value to a unit of measurement as defined in the International System of Units (SI), and further to estimate properly the measurement uncertainty. At the Institute for Reference Materials and Measurements of the Joint Research Centre of the European Commission (EC-JRC-IRMM) various plutonium and uranium spike CRMs are available. From 2010-2012, the JRC-IRMM performed successfully an inter-calibration campaign on selected plutonium spike CRMs, not only to confirm their long-term stability but also to demonstrate the JRC-IRMM's measurement capabilities. The next logical step was to carry out a similar approach on a number of uranium spike CRMs on a metrological basis applying state-of-the art measurement procedures. This enabled the setup of an inter-calibration campaign inter-linking selected 233U, 235U and 236U spike CRMs. The aim of this campaign was to confirm their certified values for quality control purposes and to demonstrate the measurement capabilities for uranium analysis via external quality tools. This was achieved by using some of these uranium CRMs for IDMS measurements of EQRAIN certified test samples and IAEA large-size dried spikes. In this paper the obtained results will be presented and discussed.JRC.D.4-Standards for Nuclear Safety, Security and Safeguard