Improvement in radiation shielding property by the multi-layered structure with narrow gaps due to reflection and absorption before and behind the gaps

摘要

A new type of radiation shield structure with narrow gaps is proposed and its shielding property is shown to he improved by taking the effects of reflection and absorption before and behind the gaps into considerationThe present shield structure consists of the multi layered structure of shield materials. The thickness of one unit shield layer is about one mean free path of the incident X-ray in the shielding material. Three basic elements are applied to the presentshield structure as follows. The first element is to equip narrow gaps between the shield layers. The second element is to use scattering absorbing composite materials. The third element is to enclose the outside of multi layered shield structure withabsorbing materials.In the present paper the basic concept for the present shield structure is proposed as the X-ray shielding design and simplified equations are derived by considering X-ray energy flow. Using the derived equations, shielding calculations are made as to asimple multi layered structure model. Furthermore, the fundamental X-ray penetration experiments and calculations by the Monte Carlo code EGS4 are performed in order to prove the improvement in shielding property due to the present multi layered structure with gaps. From these investigations, we obtained the result that the present multi layered structure with narrow gaps can improve effectively shielding property.