Preliminary development of multi-group cross sections for full deterministic ADS calculations

As an alternative to the expensive Monte Carlo calculation for the neutronics analysis of accelerator-driven systems, it had been suggested that the spallation-source computation be incorporated directly into the deterministic transport calculation. To estimate the feasibility of developing a full deterministic coupled calculation system in conjunction with the variational nodal transport code VARIANT, the efforts to generate the multi-group cross section libraries for high-energy spallation calculations were evaluated. Using the MCNPX code and its post-processing code XSEX3, the important particles to be considered for ADS neutronics analyses were first identified and the high-energy cross sections of these particles were investigated. From this preliminary study, it was found that in addition to neutron and proton, two charged pions need to be taken into account for ADS neutronics analyses. The calculated high-energy production cross sections showed that the high energy cross sections above 150 MeV can be represented accurately by multi-group cross sections with a reasonable number of groups (∼30). These cross sections depend on incident particle energy slightly, and are almost independent of the emitting angle. However, because of the dependency of the production particle spectrum on the incident particle energy, the production cross sections need to be represented as transfer matrices in a multi-group library.