REIMEP 18 inter-laboratory comparison for the measurement of uranium isotopic ratios in nitric acid solution

The REIMEP 18 (Regular European Inter-laboratory Measurement Evaluation Programme) campaign was started in October 2005. For this campaign 4 samples of depleted to low-enriched uranium were chosen. Certification measurements were carried out using a Varian MAT511 UF6-gas source mass spectrometer (GSMS) for the 235U/238U ratio and using a Triton thermal ionisation mass spectrometer (TIMS) for the minor isotope ratios 234U/238U and 236U/238U. Verification measurements of ampouled samples were performed successfully and showed good agreement with the certified ratios. REIMEP 18 has become one of the largest nuclear measurement campaigns organized by IRMM so far. Samples were shipped in March 2006 to ca. 80 registered participants. The participating laboratories are expected to submit their results until May 31st, 2006. This report describes the planning of the REIMEP 18 campaign, including the selection of campaign samples and the certification measurements.