Study on the effects of heterogeneity of objects placed in storage containers on simple radioactivity evaluation

Abstract

The clearance system regulation in Japan was amended to expand the scope of objects as “solid material”. The cable and control panel which consist of metal and organic materials are expected to be new candidates as clearance objects. In Japan, the radioactivity of the objects placed in the storage containers has been evaluated by assuming that the density in the container is uniform and radioactivity exists as a point source in the center of the container. These assumptions are applied to a specific material type such as a metal. It is necessary to confirm the availability of new candidates for clearance objects because they consist of metal and organic materials. The heterogeneity of cable placement was evaluated quantitatively using a reconstructed image from CT-scan. Experiment and simulation confirmed the applicability of the quantitative evaluation of the heterogeneity using reconstructed images. It is possible to avoid radioactivity underestimation or know the degree of the radioactivity overestimation.