SPECTRA AND FLUXES ATTENUATION OF 14 MEV NEUTRONS IN IRON GRAPHITE SHIELDS

Twenty-two group calculations were made to study the attenuation and energy degradation of rast neutrons in homogeneous and laminated shields of iron-graphite, in the form of a sphere having a monoenergetic point neutron source of 14 MeV produced from T(D, n)He reaction at its centre. Calculations were performed with the multigroup diffusion and removal diffusion equations in one dimension. The multigroup cross-section set was taken from the ENDF/B-IV cross-section library. Results were presented only for neutrons of energies from 14 to 0.4 MeV. The relaxation lengths for fast neutrons of different energy groups were determined from the attenuation curves by the ''least square fit''.