Fluence to dose equivalent conversion data and effective quality factors for high energy neutrons

Calculations of conversion coefficients from fluence to ambient dose equivalent and from fluence to maximum dose equivalent, along the principal axis of the ICRU sphere, have been performed for neutron energies up to 10 TeV, using the Monte Carlo transport code FLUKA. The results obtained are compared with those of other authors. An attempt is made to analyse the values of the radiation weighting factors recommended in ICRP Publication 60 in relation to several effective qualify factors. Three main conclusions can be reached: the ambient dose equivalent, H*(10), gives a conservative estimate of the effective dose in a limited neutron energy range; a single value of depth, d, which would make H*(d) an appropriate operational quantity irrespective of incident neutron energy cannot be specified; the value of 5, recommended for the radiation weighting factor of high energy neutrons, is expected to lead to an overestimate up to a factor 3 of the risks of exposure to the higher neutron energies.