First-Collision Doses Produced by Fast Neutron Fluxes of Wide Energy Distributions

Analytic methods for evaluation of the ratios of firstcollision dose to fast neutron flux for five classes of neutron spectra were developed. Results in terms of rads in tissue and bone have been calculated for examples of each distribution and in terms of rems for all but one distribution. Doses for several other hydrogenous materials may be obtained by multiplying tissue doses by stated factors. The neutron distributions describe fission spectra, evaporation spectra, multigroup spectra, and spectra resulting from cosmic rays. Vagaries in this method of dosimetry are discussed briefly. The rntio of dose in bone to that in tissue is found to be 0.44 in every case examined. A fast neutron dose rate of 10 to 20 millirems/day in the upper atmosphere is estimated. (auth)