Calculation code system for fission and spallation products

It is important to use computer codes with high precision for analyzing the physical process in the intense neutron source induced by the high energy proton beam. A brief description is given for the spallation and fission reactions and the particle transport codes which have been developed and upgraded at JAERI. The simulation code for High Energy Nuclear Reaction Process in the energy range of 15 MeV to 3 GeV, NMTC/JAERI, is a JAERI version of NMTC which was developed at ORNL and revised later at LANL and BNL. In this version the high energy fission reaction can be calculated, using the statistical model, in competition with the particle evaporation reaction. The mass number A of nuclides which can be dealt in the spallation calculation has been extended from [A=1;8<A<239] to [A=1;6<A<250]. A simulation code NUCLEUS for the spallation reaction of one nucleus without taking into account the internuclear cascade, was also developed to evaluate the computational model for spallation reaction and analyze effectively the data measured in thin foil experiments. For the whole energy range less than 3 GeV, two simulation code systems had been developed by connecting NMTC/JAERI with the neutron transport codes MORSE-DD and TWOTRAN-II respectively. The code SPCHAIN for calculating the time evolution process of spallation products has been developed on the base of the depletion code DCHAIN2, which had been made for the calculations of decay and built-up of fission products in a nuclear reactor. The new nuclear data have been compiled in SPCHAIN data file for about 1100 nuclides needed for TRU spallation calculation. These codes are used to calculate reaction products measured in the spallation experiment using 500 MeV protons in the booster facility of the synchrotron at KEK and to perform the conceptual design study of TRU transmutation system driven by an intense proton accelerator. (author)