Gaseous uranium hexafluoride (UF6) is one of the primary forms of uranium in the nuclear fuel cycle and it is important in order to monitor the isotopes during the enrichment process. The JRC-IRMM has recently developed and validated in-house, a new method for the accurate isotopic measurement of UF6 that allows measuring not only the major isotopes but also the minor isotope ratios ("U-minors"). Requests for reference measurements of "U-minors" have increased as they give an indication to safeguard authorities on the type of "feed" materials or on the enrichment process. Accurate measurements of the major and minor isotopes ratios are therefore of utmost importance to draw correct safeguards conclusions on operator's declarations.
The new JRC-IRMM method fulfils these requests. Its relevance has led to the recent invitation of the JRC-IRMM by the standardisation body ASTM* International to revise the existing uranium measurement standards and to develop a new standard based on the new methodology. The minor isotope ratio capability of this new method is also important to facilitate the preparation of tailor-made uranium mixtures as reference samples. For better safeguard measurements, a larger variety of isotopic reference materials certified with high accuracy may become necessary for which the JRC-IRMM is well prepared to produce upon request.
*American Society for Testing and Materials