Total neutron dose rate distributions in two shield layers

The total neutron dose rate distributions in each layer of a ''two-layers'' shield arrangement are theoretically determined. Each layer is composed of a certain hydrogeneous shield material, since the shield arrangement is supposed to be a fast neutron attenuator. A three-energy group model is used, fast, intermediate and thermal neutron groups. The flux density distributions are expressed using the ''diffusion theory '' in addition to the ''Removal-Cross-Section'' method. There are two arbitrary constants for each of the intermediate and thermal flux density distributions in each shield layer, which may be determined from the corresponding boundary conditions of the given shield arrangement. Analytical expressions are then obtained for each pair of arbitrary constants for the two energy groups for each of the two shield layers. After the determination of these arbitrary constants, the neutron flux density distributions are then completely expressed in terms of the usual diffusion-parameters, in addition to some special ''removal'' parameter. The dose rate distributions are then obtained by a corresponding average ''dose-rate to flux density'' conversion factor. The required total dose rate distributions are the summation over the corresponding energy group dose rate distributions