Group condensation method for the transport calculation of PWR with dispersed-particle fuel

A new group condensation method for pressurized water reactor (PWR) with dispersed-particle fuel is proposed. This method utilizes the neutron current method to evaluate Dancoff correction factors for different pin-cells, after which equivalent 1-D models are built by preserving the Dancoff correction factor. The Hébert model is employed to calculate the energy spectrum of fuel particles and matrix based on the equivalent model to condense the 69-fine-group cross-sections to ∼ 20 groups. This new method can accurately evaluate the double heterogeneity effect which originates from the macro heterogeneity between fuel rods and the micro heterogeneity between particles. Verification calculations for fuel assembly and JRR-3 plate-type reactor show that this group condensation method can cut the CPU time spent on transport calculation by about 60 % while ensuring that the reactivity error is less than 65 pcm and the maximum error in assembly powers is within 1.10 % with a proper broad-group structure.