Validation of the Newly Implemented 3D TDT-MOC Solver of APOLLO3 Code on a Whole 3D SFR Heterogeneous Assembly

Abstract : A three-dimensional (3D) axial capabilities have been recently implemented in the TDT-MOC solver (Method of Characteristics solver), module of the French deterministic core physics analysis code APOLLO3 currently under development. This solver has already been validated on a two plans hexagonal sub-assembly test-case and showed quite good performances. In the framework of the ASTRID project, the CFV core presents strong heterogeneities, on both radial and axial directions, that are not treated correctly with the usual 2D solvers. The aim of this paper is to quantify the approximation made with non-fully-representative 2D cluster geometries by using the 3D TDT-MOC solver on a whole 3D heterogeneous CFV sub-assembly. Results obtained with 3DTDT-MOC are compared and validated using the continuous energy Monte-Carlo TRIPOLI-4 code and are discussed. Improvements, mainly focus on the homogenization and energy-collapsing methods, are also pointed out.