AbstractCell homogenization methods for the neutronics analysis of the blanket region of a plate-type liquid-metal fast breeder reactor critical assembly are investigated, and an improved method is proposed, which calculates cell-averaged cross sections so as to preserve groupwise reaction rates in each cell in a multidrawer cell model. The present homogenization method has been applied to the analysis of the heterogeneous fast critical assembly ZPPR-13. It was found that the keffdifference between homogeneous and heterogeneous fast critical assemblies was reduced from 0.4 to 0.2%Δk/k by using the present method.