Study on group structure in DORT calculations for decommissioning activation estimation

Konno, Chikara  ; Kochiyama, Mami 

Activation estimation results in reactor decommissioning depend on neutron fluxes used in the estimation. Thus we studied how neutron fluxes changed in DORT calculations corresponding to neutron group structures; 200, 56, 49, 47 and 44 group structures adopted in the SCALE 6.2 ORIGEN library and a 48 group structure used in JAEA previous JPDR analysis. The calculated DORT neutron flux with JENDL-4.0 were compared with those by using MCNP. The comparison showed that the thermal neutron flux of the 200 group agreed with the MCNP one, while that of the 48 group underestimated by 20%, that of the 47 group underestimated by 30% and those of the 56, 49 and 44 groups underestimated by 50%.