A replacement series for IRMM-072 of uranium isotopes 233U, 235U and 238U has been prepared and is being certified. The new series, IRMM-074, follows the design of IRMM-072: the isotopic ratio n(235U)/n(238U) was held constant and the ratio n(233U)/n(235U) was varied from 1 to approximately 10-6. The isotopically enriched isotopic uranium materials were purified using identical methods involving separation on anion and cation columns followed by a precipitation as peroxide. Each of the three materials were treated in separate clean glove-boxes to eliminate cross-contamination. The oxides were sintered to convert them to U3O8 in parallel in an oven installed in a glove-box that provided a controlled low-humidity environment. 235U and 238U oxides were then weighed together and dissolved in nitric acid. The 233U oxide was dissolved to form a separate solution with the same concentration and from this primary solution 3 dilutions were made by weighing. Weighed amounts of the 235U/238U solution and weighed amounts of the original or the diluted 233U solutions were mixed and made up to a concentration of 0.1 mg·g-1. The final solutions were dispensed into individual quartz ampoules that were subsequently flame-sealed. The uncertainties contributing to the final uncertainties of the isotopic ratios are the weighing errors, the measured impurities in each isotopic material, the stoichiometry of the oxides and the isotopic abundances of each. The main uncertainty is expected to be the measurement of the chemical impurities and for this reason a number of measurement techniques are being employed. The methods for the preparation and mixing are described and the progress towards certification reported.

VERBRUGGEN Andre;  ALONSO MUNOZ Adolfo;  EYKENS Roger;  HENDRICKX Frans;  RICHTER Stephan; 

WELLUM Roger; 

2006-11-09

EC JRC Ispra (ESARDA)

JRC34139

https://publications.jrc.ec.europa.eu/repository/handle/JRC34139,