Design method of compensational shield for straight duct in concrete wall for gamma radiation, and measurement and analysis of dose rate behind wall

Abstract

A design method is described for the Fe compensational shield which is located around a straight duct in concrete shield wall against γ radiation to compensate the lowering of shielding efficiency caused by the duct. The method has been applied to the configuration, where the source area is not viewed through the duct from the detector point at the duct exit. The form of the compensational shield was determined depending on the wall thickness, the duct diameter, the incident angle of γ-ray beam to the wall, and the densities of the concrete and Fe. An experiment for the compensational shield was performed in the Dry Shielding Facility at JRR-4. The measured dose rates behind the wall were reduced effectively by the compensational shield, so that the maximum dose rates became only slightly higher than that of the bulk shield wall and the dose rates higher than the maximum dose rate for bulk shield wall were restricted only in the area near the duct exit. The experimental results have been analyzed using a multigroup γ-ray single scattering code G33YSN. © 1987, Atomic Energy Society of Japan. All rights reserved.