VERIFICATION OF ASYMMETRIC FUEL ASSEMBLY TREATMENT IN STREAM/RAST-K 2.0

Abstract

This paper presents the treatment of asymmetric fuel assemblies in the deterministic two-step STREAM/RAST-K 2.0 code system developed by the COmputational Reactor physics and Experimental group of Ulsan National Institute of Science and Technology. Few group constants are generated separately as 2×2 sub-assemblies through calculations of a single fuel assembly with full 2D geometry in the neutron-transport lattice code, STREAM. The nodal diffusion code, RAST-K 2.0, reads the generated FGC and perform the neutron-diffusion whole-core simulation. The in-house Monte Carlo code, MCS, makes a reference solution for verification. The paper presents two kinds of asymmetric fuel assembly treatment: one-node nodal simulation without sub-assemblies and four-node nodal simulation with four types of FGC generated by the newly implemented method described above. Verification results include the critical boron concentration and radial assembly power distributions for Cycle 1 of the Benchmark for Evaluation And Validation of Reactor Simulations (BEAVRS) core benchmark.