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

摘要

At the Joint Research Centre of the European Commission (EC-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), 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 (~(244)Pu spike) and IRMM-049e (~(242)Pu spike), and in particular on the certification of the first Am spike isotope reference material, certified for the n(~(241)Am)(~(243)Am) isotope ratio using Thermal Ionisation Mass Spectrometry (TIMS) with total evaporation (TE) and the ~(241)Am and ~(243)Am amount concentrations. The certification of the ~(243)Am amount concentration was performed by reverse IDMS due to the use of a highly enriched ~(241)Pu material, which served to create a special in-house spike of ~(241)Am grown in from the decay of the ~(241)Pu. The new Am spike isotope reference material is applied for age dating in nuclear forensics using the «(~(241)Pu)(~(241)Am) clock. In terms of uranium, the re-certification of the 1RMM-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 the uranium particle reference materials will be identical to the certified ratios of the UF_6 reference materials 1RMM-019-029. These were (previously) determined using state-of-the-art TIMS methods such as MTE (modified total evaporation) and DS (Double Spike), using gravimetrically prepared isotope mixtures for instrument calibration, and were confirmed independently by UF_6 -gas source mass spectrometry, in compliance with 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 with a particle generator.