Preparation and Certification of IRMM-3660, IRMM-3660a and IRMM-3660b

Isotope reference materials IRMM-3660 was prepared by dissolution of highly enriched 99.97% 236U in nitric acid. IRMM-3660a and IRMM-3660b were prepared from IRMM-3660 by gravimetrical dilution. The certified isotope content values for IRMM-3660 of 4.23651(43)*10-6 mol U per g of solution, IRMM-3660a of 4.22498(44)*10-7 mol U per g of solution and for IRMM-3660b of 4.2655(11)*10-8 mol U per g of solution have been established by mass metrology. The methodology used in the preparation and certification was similar to that of comparable uranium reference materials made in the past. The certified amount ratios were established by a TRITON TIMS using Faraday collectors and a secondary electron multiplier in combination with an RPQ energy filter for improved abundance sensitivity. Verification of the isotope amount content of IRMM-3660 was performed by IDMS using the TRITON TIMS. The uncertainties contributing to the final uncertainties of the isotopic ratios are the weighing errors, the measured impurities in the starting material, the stoichiometry of the oxide and the isotopic abundances of the primary base materials. The method for the preparation is described and the certification procedure is reported. The Isotopic Reference Materials IRMM-3660, IRMM-3660a and IRMM-3660b are part of a systematic IRMM programme to supply Isotopic Reference Materials of various isotopes at different concentrations. The Isotopic Reference Material is supplied in a sealed quartz ampoule containing 1 mL of a 1 M nitric acid solution.JRC.D.4-Isotope measurement