Pre-analyses of SS316 and SS316/Water Bulk Shielding Experiments

摘要

As one of the '93 ITER/EDA emergency tasks, JA-3 (Bulk Shielding Experiments) was authorized. This report compiled the pre-analyses for the SS316 and SS316/Water experiments. The pre-analysis of SS316 experiment was performed to determine the size and configuration of the experimental assembly using the discrete ordinate code DOT3.5 and the FUSION-40 nuclear data library. The calculation suggested that the assembly should be a cylindrical shape, the diameter and thickness of which were 1.2 m and 1.1 m, respectively. The 0.2 m thick SS316 source reflector was also necessary to simulate fusion reactor neutron environment and to decrease room returned background neutrons. In the SS316/Water experiment, the volume ratio of SS316 to water was adopted to be 4:1, which was recommended in ITER/CDA. The basic size of the SS316/water experimental assembly was set to be the same as the SS316 experimental assembly. The heterogeneity effect on the shielding performance due to the layered structure of SS316 and water was not so large in the water layer up to 30 mm in thickness. The method how to reduce background by room returned neutrons was examined. In order to calculate neutron reflection by the wall of the experimental room precisely, the S(sub N) code DOT-DD and the multigroup double-differential form cross section library DDXLIB3 were used instead of the DOT3.5 code. The calculation pointed out the following results. (1)The S/N (Signal to Noise ratio) was 0.5 at the depth of 0.9 m if there was no additional shield. (2)A 0.1 m thick additional polyethylene layer decreased background neutrons to 1/10. (3)A 0.4 m thick source reflector was not so effective since it reduced background by only a half. The additional shield of the polyethylene thicker than 0.1 m was found to be the most preferable. The final experimental configurations of the SS316 and SS316/Water experiments were determined according to these pre-analyses. (author). (ERA citation 20:011859)