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The Joint Research Centre (JRC) is the European Commission's science and knowledge service which employs scientists to carry out research in order to provide independent scientific advice and support to EU policy.
Measurements of isotope ratios are performed on uranium bearing micro-particles collected in nuclear facilities during the regular inspections by safeguards authorities, for the purpose of verifying the absence of undeclared nuclear material and activities.
These measurements are subjected to a strict quality management system, for which certified reference materials at particle level are needed for instrument calibration and quality control.
About one year after the release of the first uranium oxide (U3O8) micro-particle reference material IRMM-2329P, recently the second of such reference materials, the IRMM-2331P, has followed. In comparison to the first one, which has a 235U enrichment of 3% and a 236U abundance of 30ppm, the new IRMM-2331P has a 235U enrichment of 5% and a 236U abundance of 60ppm.
The IRMM-2331P was produced by the JRC at the laboratory in Geel/Belgium – in collaboration with the Forschungszentrum Jülich (FZJ, Jülich/Germany) and the International Atomic Energy Agency-Safeguards Analytical Service (IAEA-SGAS, Seibersdorf/Austria) and has been certified for the uranium isotope ratios.
In order to prepare the micrometer sized uranium oxide particles starting from a uranium nitrate base solution certified at JRC, a vibrating orifice aerosol generator (VOAG) was utilized at the FZJ. The certified isotope ratios were confirmed by complementary measurements on the same particles at the FZJ.
The preparation and certification of the new IRMM-2331P reference material are described in detail in the certification report found at the JRC publication repository.
The IRMM-2331P and IRMM-2329P can be ordered from the JRC online catalogue.