An Examination of the Time-Dependent Background Counts of the Delayed Neutron Counting System at the Royal Military College of Canada

Abstract

A delayed neutron counting (DNC) system for the analysis of special nuclear materials (SNM) has been constructed and calibrated at the Royal Military College of Canada. The polyethylene vials used to transport SNM samples have been found to contribute a time-dependent count rate, B(t), far above the system background. B(t) has been found to be independent of polyethylene mass and shows a dependence on irradiation position in the SLOWPOKE-2 reactor and irradiation time. A comparison of B(t) and the theoretical delayed neutron production from the fission of small amounts of ²³⁵U has indicated that trace amounts of uranium may be present in the DNC system tubing.