New certificates for the series of uranium hexafluoride reference materials
Scientists from the JRC-Institute for Reference Materials and Measurements (IRMM) recharacterised and issued new certificates for the entire series of uranium hexafluoride certified reference materials (IRMM-019 to IRMM-029). These CRMs represent a unique set of reference materials to be used in process control, nuclear material accountancy and safeguards verification measurements in enrichment plants.
Enrichment is one of the proliferation sensitive stages of the nuclear fuel cycles. Gaseous uranium hexafluoride (UF6) is one of the primary forms of uranium in the nuclear fuel cycle. Safeguards authorities require for accurate measurements of uranium hexafluoride samples, CRMs with small uncertainties, not only for the major isotope ratio n (235U)/n(238U) but now also, for the minor ratios n(234U)/n(238U) and n(236U)/n(238U). To meet these demands, the JRC-IRMM recharacterised and issued new certificates for the entire IRMM-019 to IRMM-029 series, originally dating from the 1980s-1990s. This series covers the enrichment range from depleted uranium (IRMM-019 to IRMM-021) to enriched uranium (IRMM-023 to IRMM-029) via natural uranium (IRMM-022). The series has been certified using a new set of calibrants in the form of gravimetrically prepared uranium nitrate solutions, in combination with recently developed measurement methods for Thermal Ionisation Mass Spectrometry (TIMS). The CRMs in the form of uranium hexafluoride (UF6) gas represent a unique set of its kind and are available from the JRC-IRMM. They are used for instrument calibration, method validation, quality control, and the assessment of method performance for uranium hexafluoride gas source mass spectrometry (UF6 GSMS).
On request by the International Atomic Energy Agency (IAEA), a new project has recently been started to make reference materials available in the form of uranium nitrate solutions (IRMM-019S to IRMM-029S) for direct TIMS or ICP-MS measurements.