Uncertainty measurement evaluation of WDXRF and EDXRF techniques for the Si and U_total determination in U₃Si₂ nuclear fuel

Abstract

Uranium silicide (U₃Si₂), 20% ²³⁵U enriched powder, is an intermetallic compound used as nuclear fuel material, which is the state-of-the-art among nuclear fuel materials used in modern research reactors. It is produced by IPEN and used as nuclear fuel of the IEA-R1 reactor (IPEN/CNEN, São Paulo, Brazil); U₃Si₂ has 92.3 wt% U_total and 7.7 wt% Si. The qualification of this material requires chemical and physical tests such as Si and U_total content, isotope ratio, impurities, density, specific surface area and particle size determination. The Si and U_total were determined by gravimetric and volumetric procedures. Usually, these classical methods require a long time for analyses and are expensive. The objective of this study was to establish a fast and efficient analytical method to meet ISO/IEC 17025:2005 requirements in the Si and U_total determination. The X-ray fluorescence techniques (XRF) were chosen to allow a direct and non-destructive analysis, what is the main advantage compared to other instrumental techniques, since previous chemical treatments are not necessary. In this study, the performance of the wavelength dispersive (WDXRF) and energy dispersive (EDXRF) X-ray fluorescence techniques was evaluated. Furthermore, two different sample preparation procedures, plain powdered and pressed powdered, were evaluated. Statistical tools were used to evaluate the results and a comparison between these results and the conventional methods was done.