International Comparison of the Chemical Assay of Uranium and Thorium and of the Precision and Accuracy of the U-235 Isotopic Analysis of High Enriched Uranium in THTR Fuel for Safeguards Purposes

Interlaboratory tests on the assay of U and Th and of the U-235 isotopic abundance determination in HEU fuel of the German THTR prototype reactor have been completed within the framework of the German support programm for the IAEA. The applied sampling techniques ensure a representativity of the sample of 0.05 %. The precision (1 a) and accuracy of uranium and thorium assay are better than or equal to 0.1 %. The separation and measurement errors of the U-235 isotopic determination are below 0.02 %. These results fulfill safeguards requirements.