Validation of a nuclear code system for prismatic high temperature gas-cooled reactors based on the Very High Temperature Reactor Critical Assembly benchmark

The inherent safety characteristic of high temperature gas-cooled reactor (HTGR) is universally acknowledged. On account of the double-heterogeneity of the coated fuel and the irregular core pattern of the prismatic HTGR, a code system based on Monte-Carlo homogenization and deterministic transport concept was used as a nuclear design code system for prismatic HTGR. An investigation on homogenization model and preliminary validation of this code system is conducted based on VHTRC benchmark which is a prismatic HTGR criticality assembly. The validation results indicate that group constants generation based on Monte-Carlo homogenization and appropriate energy group, then modified by super homogenization (SPH) method further, ensures high precision of homogeneous core calculation.