Validation of an advanced APOLLO3® deterministic scheme for characterizing of the Jules Horowitz irradiation reactor core

Abstract

International audienceJHR is a new material testing reactor under construction at CEA Cadarache. Currently, the neutronic characteristics of the core are calculated thanks to the HORUS3D/N deterministic scheme. The industrial route of this scheme follows a two steps approachwith first the APOLLO2 MOC lattice calculation and then the CRONOS2 core calculation based on diffusion theory. APOLLO3®is the new deterministic calculation platform at CEA, which incorporates advanced computation methods. In this paper, a new reference calculation scheme for JHR is being set up using the new methods brought by APOLLO3®. The calculation scheme is validated against reference stochastic simulations performed by TRIPOLI4®. Improvements at the lattice step allow a significant reduction of biases on absorption rates for fuel elements and Hf control rods when compared to results of a scheme that mimics, within APOLLO3®, the HORUS3D/N scheme. The main changes in the new scheme are coming from the use of the subgroup self-shielding method instead of the Fine-structure equivalence method. These changes are associated to refined geometrymeshes and to the 383 energy group structure. Condensed cross-sections from the lattice step are used to compute the neutron balance of a 2D JHR core configuration with five Hf control rods inserted. Core-reflector super cell has been added in the new calculation scheme to produce refined reflector cross sections. The MOC 2D core calculation performed with a coarser 41-group structure preserves the lattice calculation improvements and gives better predictions on reactivity and reactions rates. Next steps will use a 3D Sn MINARET full-core calculation with depletion including in-core experimental devices