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

Twenty-two group calculations were made to study the attenuation and e nergy degradation of rast neutrons in homogeneous and laminated shield s of iron-graphite, in the form of a sphere having a monoenergetic poi nt neutron source of 14 MeV produced from T(D, n)He reaction at its ce ntre. Calculations were performed with the multigroup diffusion and re moval diffusion equations in one dimension. The multigroup cross-secti on set was taken from the ENDF/B-IV cross-section library. Results wer e presented only for neutrons of energies from 14 to 0.4 MeV. The rela xation lengths for fast neutrons of different energy groups were deter mined from the attenuation curves by the ''least square fit''.