Efficiency modeling for neutron detectors

Abstract

Neutron detectors are used for various applications, such as for workplace monitoring in a neutron field, during nuclear incidents, and for the detection of contraband nuclear material. The Remote Sensing Laboratory has developed and employed several neutron detector designs, and characterization data have been collected with these detectors under varying environmental conditions. Using MCNP/MCNPX the neutron fluence rate and dose rate were evaluated during open-field deployment as a function of moisture content in air and soil, barometric pressure, and varying pavement and soil composition. The focus of this analysis was on the incident neutron spectra, detector efficiency and count rate at the detector location. The most prevalent parameters directly contributing to scattered neutrons into the active detector volume were evaluated. Experimentally observed functional dependence on the source-detector distance was compared to MCNP/MCNPX simulation data. This study provides detector efficiency data for a wide range of operational conditions beyond the current capacity for experimental detector characterization.