抄録
Japanese demonstration and commercialized FBR assemblies are planed to adopt the inner duct for severe accident through which melted fuel goes out of core. It is seemed that the traditional nuclear calculation scheme which generates nuclear constants with homogeneous assembly calculation cannot be adopted. From this view point, new lattice physics code for hexagonal geometry GALAXY-H has been developed based on GALAXY, which is a two dimensional transport calculation code for LWR assemblies. The methodology of flux calculation for GALAXY-H is based on the method of characteristics (MOC). For both resonance and neutron transport calculations, GALAXY can exactly treat heterogeneity of calculated configuration. GALAXY-H is a hexagonal version of GALAXY, and can exactly treat the inner duct and wrapper tube in assemblies. In this study, by using GALAXY-H, heterogeneous effect of Japanese demonstration FBR assembly on effective cross sections for inner duct is evaluated. For the first time, position dependence background cross section is calculated by MOC in assembly configuration which contains both of the inner duct and the wrapper tube. It is confirmed that the effect of this difference is not small.
