Research on Ring Reactivity-Equivalent Physical Transformation Method for Homogenization of Double-Heterogeneous Systems

Because of the double heterogeneity of the dispersed particle-type fuel and the burnable poison, the traditional volumetric homogenization method (VHM) on double-heterogeneous (DH) systems will bring unacceptable calculation deviation. The reactivity-equivalent physical transformation (RPT) method applied to the DH systems with particle-type dispersed fuel has the features of simplicity and high calculation accuracy. In this paper, the traditional RPT and IRPT methods have been analyzed and verified, and it suggests that for some DH systems with dispersed particle-type burnable poison with large absorption cross section, these two methods are with relatively large calculation deviation. Ring RPT (RRPT) method and Two-step ring RPT (TRRPT) method are proposed to deal with the DH systems of one and two types of particles. Results of depletion calculations for different types of dispersed particle-type fuel and burnable poisons and the comparison with Mote Carlo results of grain models prove the validity of RRPT method and TRRPT method. The preliminary conclusion can be obtained that Ring RPT method has wider scope of usage and higher accuracy than the traditional RPT method.