Abstract: Neutron attenuation ratios of four different structural gaps on two kinds of spectrum neutrons were calculated using SuperMC (Super Monte Carlo Program for Nuclear and Radiation Simulation). The structural gaps were made of boron polyethylene (B-PE) materials. In order to study the effect of different gaps on neutron shielding performance, they were compared with seamless materials and the relative reductions of neutron attenuation ratios were obtained. Some simulation results were verified by the experiments under the same conditions. The results showed that, for the B-PE materials with a thickness of 6 cm, the relative reduction of neutron attenuation ratio is 1/8 on fast neurons by comparing of oblique gap with straight gap. That is 1/3 on slowing down neutrons. Oblique gap is proved to have the least negative effect on neutron shielding.

Key words: structural gap, neutron spectrum, attenuation ratio, SuperMC program