News about certified nuclear isotope reference materials at Joint Research Centre – Unit G.2 - METRO group in Geel

Abstract

At the Joint Research Centre (JRC), Directorate G (Nuclear Safety and Security), Unit G.2 (Standards for Nuclear Safety, Security and Safeguards, SN3S), in Geel (Belgium), formerly called IRMM (Institute for Reference Materials and Measurements), the so-called METRO (metrological tools for nuclear safeguards) group is engaged in the preparation and certification of nuclear isotopic reference materials. Within the several recent and the current year, the focus was on renewals of two Pu spike reference materials, namely IRMM-042a (244Pu spike) and IRMM-049e (242Pu spike), and in particular on the certification of the first Am spike isotope reference material, certified for the 241Am/243Am isotope ratio using TIMS (total evaporation) and the 241Am and 243Am amount concentrations. The certification of the 243Am amount concentration was performed by reverse IDMS due to the use of a highly enriched 241Pu material, which served to create a special in-house spike of 241Am grown in from the decay of the 241Pu. The new Am spike isotope reference material is very useful for age dating using the 241Pu/241Am clock in nuclear forensics. In terms of uranium, the re-certification of the IRMM-019-029 series of UF6 reference materials will be used for the preparation of new uranium solution reference materials suitable for TIMS and MC-ICPMS instruments, the IRMM-2019-2029 series, and furthermore for the preparation of micrometer size uranium particles certified for the isotopic composition and the uranium amount per particle. The certified isotopic composition of the uranium solutions as well as for the uranium particle reference materials will be identical to the certified ratios of the UF6 reference materials IRMM-019-029. These were (previously) determined using state-of-the art TIMS methods such as MTE (modified total evaporation) and DS (Double Spike) and using gravimetrically prepared isotope mixtures for instrument calibration, and were confirmed by a second method, in this case UF6-gas source mass spectrometry, as required by the ISO 17034. Using various types of "process control measurements" it will be ensured that the isotopic composition is not changed during the preparation of the solutions (e.g. by diluting and dispensing), and due to the preparation of the particles using the particle generator.JRC.G.2-Standards for Nuclear Safety, Security and Safeguard