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Abstract

A set of 6 new synthetic mixtures with n(236U)/n(238U) isotope ratios varying from 10-4 to 10-9 has been prepared and certified. Natural uranium with low 236U isotope abundance and enriched 236U were both purified using well proven chemical methodology extensively tested in the preparation of other uranium synthetic mixtures such as IRMM-074. The purification involved separation on anion and cation columns followed by precipitation as peroxide. Manipulations were carried out in separate new glove-boxes to avoid cross contamination. The oxides were sintered into U3O8 in an oven installed in a glove-box with controlled humidity. Primary solutions of the same concentration were prepared by dissolving the oxides of 236U and natU. From the 236U solution four dilutions were made by weighing. Weighed amounts of the dilutions of 236U and weighed amounts of natU were mixed to form a set of n(236U)/n(238U) mixtures at a concentration of 1 mg U-g-1. The final solutions were dispensed into quartz ampoules which were subsequently flame sealed. Verification of the mixtures IRMM-075/1-6 was performed by TRITON TIMS measurements using Faraday collectors and secondary electron multipliers in combination with an RPQ energy filter for improved abundance sensitivity. The results agreed well with the certified values obtained from the mixing calculations. The uncertainties contributing to the final uncertainties of the isotopic ratios are the weighing errors, the measured impurities in each starting material, the stoichiometry of the oxides and the isotopic abundances of each. The method for the preparation and mixing is described and the certification and verification procedures are reported.

Additional information

Authors: VERBRUGGEN A, European Commission, Joint Research Centre, Institute for Reference Materials and Measurements, Geel (BE);ALONSO A, European Commission, Joint Research Centre, Institute for Reference Materials and Measurements, Geel (BE);EYKENS R, European Commission, Joint Research Centre, Institute for Reference Materials and Measurements, Geel (BE);KEHOE F, European Commission, Joint Research Centre, Institute for Reference Materials and Measurements, Geel (BE);KÜHN H, European Commission, Joint Research Centre, Institute for Reference Materials and Measurements, Geel (BE);RICHTER S, European Commission, Joint Research Centre, Institute for Reference Materials and Measurements, Geel (BE);WELLUM R, European Commission, Joint Research Centre, Institute for Reference Materials and Measurements, Geel (BE);AREGBE Y, European Commission, Joint Research Centre, Institute for Reference Materials and Measurements, Geel (BE)
Bibliographic Reference: EUR 22924 EN (2007), 20 pp. Free of charge
Availability: Katalogue Number: LA-NA-22924-EN-C The PDF version can be downloaded from: http://bookshop.europa.eu
ISBN: ISBN 978-92-79-06960-4
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