Review of Scattering Corrections for Calibration of Neutron Instruments

Abstract

In this paper we consider scattering corrections that must be made when neutron personnel instruments are calibrated with a point source of neutrons near the centre of a calibration room. We consider three basic types of scatter: (1) scattering from a plane slab, (2) scattering from walls of an enclosed room, and (3) air scatter. In each case we proceed from an idealised situation, where the correction can be predicted analytically, to an actual calibration room, where predictions must be checked by Monte Carlo calculations or experiment. Calculations show that the postulation of an image source provides a good model for predicting the fluence of neutrons scattered from aluminium and concrete slabs. Calculations also show how the fluence of neutrons scattered from the walls of an enclosed room relates to the case of neutron fluence in a spherical cavity and how the neutron fluence is increased by scattering in the air around source and detector. Finally, calculations are compared with experiments on the response of a neutron dose equivalent monitor.