Abstract
JEFF-3.1.1 is the reference nuclear data library in CEA for the design calculations of the next nuclear power plants. The validation of the new neutronics code systems is based on this library and changes in nuclear data should be looked at closely. Some new actinides evaluation files at high energies have been proposed by CEA/Bruyeres-le-Chatel in 2009 and have been integrated in JEFF3.2T1 test release. For the new release JEFF-3.2, CEA will build new evaluation files for the actinides, which should be a combination of the new evaluated data coming from BRC-2009 in the high energy range and improvements or new evaluations in the resolved and unresolved resonance range from CEA-Cadarache. To prepare the building of these new files, benchmarking the BRC-2009 library in comparison with the JEFF-3.1.1 library was very important. The crucial points to evaluate were the improvements in the continuum range and the discrepancies in the resonance range. The present work presents for a selected set of benchmarks the discrepancies in the effective multiplication factor obtained while using the JEFF-3.1.1 or JEFF-3.2T1 library with the deterministic code package ERANOS/PARIS and the stochastic code TRIPOLI-4. They have both been used to calculate cross section perturbations or other nuclear data perturbations when possible. This has permittted to identify the origin of the discrepancies in reactivity calculations. In addition, this work also shows the importance of cross section processing validation. Actually, some fast neutron spectrum calculations have led to opposite tendancies between the deterministic code package and the stochastic code. Some particular nuclear data (MT=5 in ENDF terminology) seem to be incompatible with the current MERGE or GECCO processing codes.
Highlights
Different units are involved at CEA in the production of nuclear data for the neutronics simulation codes
This article first presents the selected set of benchmarks. It details the different methods used in the reactivity effect breakdown analysis. It shows some results in reactivity dicrepancies to illustrate the main findings of this work and the choices to which they have led in the new evaluation files, which will be proposed in JEFF-3.2 library
The standard deviation for JEFF-3.1.1 or BRC-2009 calculations is close to 10 pcm. These results shows that the JEFF-3.1.1 tends to underestimate the experimental values, and that BRC-2009 corrects this underestimation
Summary
Different units are involved at CEA in the production of nuclear data for the neutronics simulation codes. As a first step in the collaborative work, the impact of the nuclear data change from JEFF-3.1.1 to BRC-2009 [2] for some U, Pu and Am actinides only (proposed in JEFF-3.2T1 library released in 2011) is invertigated. This article first presents the selected set of benchmarks It details the different methods used in the reactivity effect breakdown analysis. It shows some results in reactivity dicrepancies to illustrate the main findings of this work and the choices to which they have led in the new evaluation files, which will be proposed in JEFF-3.2 library
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