APPLICATION OF THE EPRI DEPLETION REACTIVITY BENCHMARKS

摘要

The EPRI measured-based depletion reactivity benchmarks intend to facilitate the validation of burnup credit by validating the combined effect of changes in isotopic content and cross-sections. In the framework of burnup credit implementation for PWR fuels, this paper proposes to study the application of the EPRI benchmarks for a spent fuel pool criticality evaluation using the French tools: the DARWIN 2.2 depletion package and the CRISTAL VI criticality safety package, both based on cross-section libraries from the JEF2.2 evaluation. For that purpose, the benchmarks are analyzed using the connection of DARWIN 2.2 with APOLLO2-MORET 4, allowing the determination of the bias for the reactivity decrement. Then, these results are used to define a bias to take into account in the criticality evaluation of a spent fuel pool. In addition, the benefit of the EPRI depletion reactivity benchmarks is assessed through a comparison with the validation approach adopted in France until now. The bias resulting from this latter approach is evaluated by 1) applying, to the calculated nuclides concentrations, isotopic penalizing factors derived from the comparison between calculated values of nuclide concentrations and experimental values obtained from used fuel chemical analyses from French reactors, 2) analyzing representative critical experiments. Additional analysis of the benchmarks using the connection of VESTA 2.1 with MORET 5 is performed as these codes allow calculations of complex 3D geometrical configurations and the use of various nuclear data libraries.