The thermal neutron sensitivities of SEI and Toshiba FD-P10-7 radiophotoluminescent glass dosimeters

Abstract

The thermal neutron sensitivities of SEI and Toshiba FD-P10-7 radiophotoluminescent silver activated metaphosphate glass dosimeters have been measured and studied theoretically. The graphite thermal neutron column attached to the AEEW reactor NESTOR was utilised as a source of thermal neutrons with minimal fast neutron and gamma-ray contamination. Both the neutron removal and gamma correction measurement techniques were applied and these gave consistent results. It was found that the thermal neutron sensitivity of the Toshiba dosimeters is comparable to the most neutron insensitive thermoluminescent materials available. Because of their larger size and higher silver concentration, however, SEI dosimeters are an order of magnitude more neutron sensitive. The neutron sensitivity of FD-7 glass has not been reported previously, whereas in the case of SEI glass, there exists a modest body of previous work on dosimeters of nominally identical composition. The present results are in reasonable agreement with these earlier determinations. A simple physical model was constructed in order to interpret the measured responses. The model takes into account neutron-capture recoil energy, neutron-capture gamma-rays and the beta- and gamma-ray emissions from neutron induced radionuclides created within the dosimeters. The calculated and experimental values are in excellent agreement indicating that the response of these dosimeters in mixed thermal neutron/gamma-ray fields is sufficiently well understood to be applied with confidence.