Thermal neutron albedo and diffusion parameter measurements for monolithic and geometric voided reflectors

Abstract

Experimental measurements of thermal neutron albedo ( β th ) and diffusion parameters have been carried out for monolithic as well as for water reflectors having spherical and cylindrical voids using Am–Be neutron source and BF 3 -detector. The measured saturation values of β th for monolithic water reflector has been found be 0.80 ± 0.024 , which is in good agreement with the corresponding value 0.81 quoted in the literature. In this case, the values of diffusion coefficient ( D ) and diffusion length ( L ) have been found to be 0.142 ± 0.021 and 2.57 ± 0.032 cm which are in good agreement with the standard values 0.144 and 2.755 cm, respectively. For water reflectors with spherical voids having 3.9 cm diameter, the saturation value of β th has been found to be 0.74 ± 0.018 and the values of D and L have been found to be 0.32 ± 0.043 and 4.39 ± 0.059 cm , respectively. In the case of a water reflector with cylindrical voids having diameter 2.54 cm and length 48 cm, the saturation value of β th and the values of D and L have been found, respectively, to be 0.74 ± 0.019 , 0.41 ± 0.034 , 5.79 ± 0.067 cm for parallel configuration and 0.78 ± 0.018 , 0.347 ± 0.028 , 4.22 ± 0.056 cm for the perpendicular configuration, respectively.