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Validation of JEFF-3.1.1 Thermal and Epithermal Neutron-Induced Capture Cross Sections Through MELUSINE Experiment Analysis

David Bernard, Olivier Fabbris, Romain Gardet

Nuclear Science and Engineering / Volume 179 / Number 3 / March 2015 / Pages 302-312

Technical Paper /

First Online Publication:December 23, 2014
Updated:February 26, 2015

Three similar experiments performed in the 8-MW(thermal) MELUSINE experimental power pool reactor aimed at analyzing 1 GWd/tonne HM spent fuel pellets doped with several actinides and fission products. The goal was to measure the energy-integrated neutron-induced capture cross section in three different neutron spectra (from pressurized water reactor–like to undermoderated ones). This paper summarizes the combined deterministic APOLLO2 and stochastic TRIPOLI4 analysis using the JEFF-3.1.1 European nuclear data library. Very good agreement is observed for most neutron-induced capture cross sections of actinides except for a clear underestimation of 241Am(n,γ). An accurate value of its associated isomeric branching ratio is also suggested. A resonant fluctuation (factor of 2.7 between the two available excited levels regarding the l = 0 total orbital momenta) is suggested for this isomeric branching capture ratio. Finally, a precise value (more accurate than the reported JEFF-3.1.1 one) of the decay branching ratio of 242gAm(β+/ε) is deduced: 0.171 ± 0.001.

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