Neutronics Experimental Validation of the Jules Horowitz Reactor Fuel by Interpretation of the VALMONT Experimental Program—Transposition of the Uncertainties on the Reactivity of JHR With JEF2.2 and JEFF3.1.1

Abstract

The new European material testing Jules Horowitz Reactor (JHR), currently under construction in Cadarache center (CEA France), will use LEU (20% enrichment in 235 U) fuels (U 3 Si 2 for the start up and UMoAl in the future) which are quite different from the industrial oxide fuel, for which an extensive neutronics experimental validation database has been established.The HORUS3D/N neutronics calculation scheme, used for the design and safety studies of the JHR, is being developed within the framework of a rigorous verification-numerical validation-experimental validation methodology. In this framework, the experimental VALMONT (Validation of Aluminium Molybdenum uranium fuel for NeuTronics) program has been performed in the MINERVE facility of CEA Cadarache (France), in order to qualify the capability of HORUS3D/N to accurately calculate the reactivity of the JHR reactor.The MINERVE facility using the oscillation technique provides accurate measurements of reactivity effect of samples. The VAL- MONT program includes oscillations of samples of UAl Al andUMo/Al with enrichments ranging from 0.2% to 20% and Uranium densities from 2.2 to 8 g cm 3 . The geometry of the samples and the pitch of the experimental lattice ensure maximum representativeness with the neutron spectrum expected for JHR. By comparing the effect of the sample with the one of a known fuel specimen, the reactivity effect can be measured in absolute terms and be compared to computational results. Special attention was paid to the rigorous determination and reduction of the experimental uncertainties.The calculational analysis of the VALMONT results was performed with the French deterministic code APOLLO2. A comparison of the impact of the different calculation methods, data libraries and energy meshes that were tested is presented. The interpretation of the VALMONT experimental program allowed the experimental validation of JHR fuel UMoAl8 (with an enrichment of 19.75% 235 U) by the Minerve-dedicated interpretation tool: