Monte Carlo estimates of neutron backscatter from an infinite slab of standard man composition have been arrived at, in the incident neutron energy range of 0.025 eV-10 MeV, for normal and isotropic incidence. The information obtained includes (i) the total and thermal components; (ii) the spectrum; and (iii) the angular distribution of the backscatter component. As the thermal neutron component of the backscatter would be recorded by thermal neutron personnel monitoring devices, the thermal backscatter response of such devices for various incident energies has been estimated, and appropriate correction factors recommended. This correction is negligible at higher incident neutron energies (it is of the order of 0.5% in the range 1–10 MeV) whereas it increases to 50–60% in cases where thermal and intermediate energy neutrons are incident. Further, the secondary gamma dose resulting from (n, gamma) capture in tissue was considered. This dose was estimated at the surface of an infinite slab of standard man composition, and was found to agree with reported experimental values. This gamma dose would be recorded in the gamma radiation personnel monitoring device, as a superfluous dose. The relevant correction factor has therefore been estimated. This correction is negligible in the neutron energy range 1–10 MeV and reaches a steady value of about 10% in the neutron energy range of 10 keV to thermal. A composite personnel monitoring device for both thermal and intermediate energy neutrons, is suggested. © 1969 Health Physics Society.
