A treatment of medium-energy particle induced fission for spallation-systems' calculations

A method for including medium-energy fission into neutronic calculations for spallation systems is described and discussed. The basis is a semi-empirical evaporation plus fission model able to treat a wide range of nuclear states in the mass region above about 100 amu with nuclear excitation energies up to 1000 MeV. In combination with suitable nuclear physics models describing the entrance channels and a suitable evaporation algorithm, this is able to give a full description of the de-excitation of the intermediate nuclear states formed in interactions with target nuclei from Ag to Cf by (i) medium energy (up to a few GeV) nucleons and pions, (ii) thermal and fast neutrons and (iii) light ions with energy up to several 100 MeV/A.