Accurate reactivity effects of pwr control rods using apollo3 advanced solvers
Résumé
In this paper, the most advanced features of the APOLLO3 new deterministic neutron transport code are being used to calculate accurately control rod reactivity effects. In order to illustrate the advantage of the proposed scheme, two models are being used a model in which the control rod assembly is surrounded by standard assemblies, calculated using 2D TDT-MOC solver and fine structure self-shielding method with 281 groups at the lattice calculation level; and a semi-heterogeneous model (3x3 zones) of the control rod assembly at the core calculation level. Compared to the traditional single assembly and homogeneous core calculation usually associated with an equivalence method such as SPH, these new models take advantage of the possibility of subdividing an assembly with the MINARET transport core solver through unstructured conforming triangular spatial mesh (Discontinuous Galerkin Finite Elements), to represent explicitly the control rod shadowing effects within the control rod assembly. Tests to demonstrate the ability of such an approach have been carried out on a standard UOX fuel PWR reactor. The new APOLLO3 scheme has been checked against TRIPOLI-4 Monte-Carlo calculation and has been found extremely accurate without requiring any equivalence method. This calculation scheme lays down the foundations for a new upgrading approach for deterministic calculations to study PWR cores.
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