A deterministic against Monte-Carlo depletion calculation benchmark for JHR core configurations

The Jules Horowitz Reactor (JHR) is the next international Material-Testing Reactor (MTR) under construction in the south of France at CEA Cadarache research center. Its first criticality is foreseen by the end of the decade. The innovative character of the JHR led to the development of a specific neutronic calculation scheme called HORUS3D/N for performing design and safety studies. HORUS3D/N is based on the deterministic codes APOLLO2 and CRONOS2 and on the European nuclear data library JEFF-3.1.1. Up to now, the biases and uncertainties due to the HORUS3D/N calculation scheme in depletion have been assessed by comparing HORUS3D/N deterministic calculations with 2D APOLLO2-MOC reference route calculations. The recent development of the Monte-Carlo code TRIPOLI-4^R in its depletion mode (TRIPOLI-4^RD) offers the opportunity to study the JHR 3D core configurations under fuel depletion conditions. This paper presents the first CRONOS2/TRIPOLI-4^RD benchmark results obtained for 3 core configurations of interest including control rods and experimental devices up to a burnup value of 60 GWd/tHM. The main parameters of interest are the reactivity and the isotopic concentrations as functions of burnup. This first study of actual JHR configurations in depletion demonstrates that CRONOS2 underestimates the reactivity for burnups lower than 8 GWd/t_HM and overestimates it for higher burnups, with respect to the TRIPOLI-4^RD predictions. A good agreement between the two codes is observed concerning the ²³⁵U consumption with discrepancies values less than -0.5% at 60 GWd/t_HM. Nevertheless, a global CRONOS2 overestimation of the plutonium inventory can be noticed. Compared with 3D assembly calculation in an infinite lattice, this overestimation was tracked down to the condensation of the nuclear constants provided by APOLLO2, showing the limits of a two steps calculation. (authors)