Feasibility study on evaluating uranium enrichment with the High Resolution Gamma-Ray Spectrometry and X-ray fluorescence

Highlights: • The uranium enrichment of the environmental sample is analyzed to verify the declared information for the nuclear safeguards. • The HRGS and MMXRF could analyze samples with short detection time, and high reproducibility. • The enrichment could be evaluated with γ-ray counts of ²³⁵U and uranium counts detected by the HRGS and MMXRF, respectively. • Calculated results are overestimated, however, they provides enough information for the screening. - Abstract: The uranium enrichment of the environmental sample should be analyzed to verify the declared information for the nuclear safeguards. The High-Resolution Gamma Spectrometry (HRGS) and Monochromatic Micro X-ray Fluorescence (MMXRF) is able to analyze the sample with a short detection time and high reproducibility. These are the advantage to measure the samples for screening before laboratory analysis. This study concentrated on uranium enrichment evaluation with the gamma-ray emission counts of ²³⁵U isotope (@185.7 keV) detected with the HRGS and counts of total uranium elements detected by MMXRF. As a result, the measured data were calculated for the uranium enrichment in three different ways: (i) Activity of ²³⁵U with the HRGS and mass of total uranium with the MMXRF, (ii) counts ²³⁵U with the HRGS and counts of total uranium, and (iii) activity of ²³⁵U and ²³⁸U with the HRGS. Based on the comparison with the mass spectrometry, method (iii) is able to derive the uranium enrichment the most accurately. However, method (ii) provides enough information for the screening to sort the sample for which laboratory analysis is necessary, when the sample's equilibrium status is not guaranteed.