Equivalent dose versus dose equivalent for neutrons based on new ICRP recommendations

Recent ICRP recommendations include changes in the concept of radiation quality and weighting factors. This justifies new calculations of primary limiting quantities. The male (ADAM) and female (EVA) phantoms, based on MIRD specifications, seem to be well suited standards for this purpose. 3-D Monte Carlo calculations of radiation transport throughout the ADAM phantom and of energy release in particular organs have been performed for neutrons of energies from thermal up to 20 MeV, and for different irradiation geometries. Energy transfer by neutron-induced charged secondaries has been described using the continuous slowing down approximation (csda). Resulting LET spectra are the physical measure of radiation quality. They differ considerably from organ to organ and depend on irradiation geometry, especially for low energy neutrons. Newly introduced quantities, i.e. equivalent doses in organs and the effective dose in man, assessed without taking into account these variations, do significantly overestimate the dose equivalent values evaluated using LET based quality factors. (author)