An approach to measure the enrichment of 235U by enrichment meter principle without knowing the thickness of intervening matter

Abstract

Abstract The enrichment measurement of 235U is an important issue in the applications of nuclear material accounting and nuclear nonproliferation etc. The nondestructive assay (NDA) method based enrichment meter principle is a robust and direct measuring approach. At the same time, there are some limits, such as the infinite thickness approximation condition and the wall thickness correction, in comparison with the self-calibration relative ratio methods. According to the Klein–Nishina equation, the small-angle Compton scattering events can be used to estimate the attenuation due to the intervening matter between uranium material and gamma spectrometer. At State Nuclear Security Technology Center (SNSTC) we used three high-enrichment U3O8 samples to perform the 235U enrichment measurement experiment by the enrichment meter approach. When shielding plates of iron are added, the measurement results deviate further from the certified value as the shield increases. Employing the small-angle Compton scattering events to estimate the attenuation, we accomplished the thickness correction for the iron-plate shield varying from one layer to four layers (with each thickness of 3.1 mm).