Duct effects on the distribution of γ-rays from a mixed radiation field in an ilmenite-concrete shield

The effects of ducts on the dose distribution of γ-rays in an ilmenite-concrete shield have been investigated using a collimated beam of neutrons and γ-rays from a reactor. Measurements were performed in a homogeneous concrete medium and repeated in a medium containing cylindrical air-filled ducts having different lengths and diameters. The γ-ray doses were measured using 7LiF in Teflon matrix discs. The results show that the presence of ducts increases the γ-ray doses in the regions surrounding the ducts except for thicknesses less than 20 cm. This increase has a maximum value at positions located approx. 10 cm after the duct ends. The observed increase at peak positions depends on the duct diameters and vertical distances. (author)