International program REBUS - French comparisons of the experimental data with the results of various criticality codes
Congress title :ICNC 2007
Congress location :Saint-Petersbourg
Congress date :28/05/2007
In criticality studies, considering the loss of reactivity due to burnup may result in significant optimisation in the management of spent fuel materials, as well as a decrease of the radioactivity burden. This concept, known as "burnup credit " (BUC), has motivated EDF to carry out R&D programmes in this field. To this end, the REBUS-PWR (Reactivity test for a direct Evaluation of the Burnup-Up credit on Selected irradiated LWR fuel bundles) International Programme was initiated by BELGONUCLEAIRE and SCK-CEN and partially supported by EDF. The main purpose of this programme was to contribute to the validation of computer codes devoted to burnup credit and criticality calculations. Neutronics calculations were performed by EDF and its technical partners CEA and IRSN with the DARWIN depletion code and the criticality codes MCNP, TRIPOLI and APOLLO-MORET (from the French criticality package CRISTAL). This article aims at providing a comparison between the results obtained with the various criticality codes and the experimental data. Calculations were performed in two critical configurations, either with a fresh Uox fuel bundle, or with an irradiated one, at the critical water level determined by the experiment. In each case, the keff was computed with each of the three different criticality codes. In addition to the reactivity measurements and calculations, the axial buckling and the fission rate distributions on the main axes were computed and compared with the measurements. Studies carried out by EDF, CEA and IRSN focused on: -analysing the consistency between the computed results and the experimental measurements; -comparing the reactivity weight of the experimental bundle with the feeding core bundle's; -studying the effect of material balance disturbances on the reactivity level; -evaluating the impact on the keff of some of the various experimental uncertainties.