Attenuation of 14 MeV neutrons in shields of concrete and paraffin wax

This work describes the measurements made in determining the attenuation of 14 MeV neutrons in shields of concrete and paraffin wax. Measurements were made for fast and thermal neutrons using activation detectors and the results compared with calculations based on 2-group diffusion theory. Good agreement was obtained considering the limitations of the theory. Removal cross-sections and build-up factors were also measured using a different attenuation model. Values obtained for the removal cross-sections in concrete were lower than those reported by other authors. Other measurements are described in which neutron relaxation lengths are determined using a fixed source-detector geometry with different neutron detectors. Results agree reasonably well with those obtained by other authors.