Validation of actinide nuclear data based on reactivity worth experiments in a MOX-LWR spectrum

•Unique set of experimental data regarding separated actinides from 232Th to 245Cm.•Reference calculation methodology based on an exact perturbation method in TRIPOLI4®.•Integral trends for improving future nuclear data libraries for future. OSMOSE was a CEA/DOE collaborative experiment dedicated to the improvement of actinide nuclear data. Based on reactivity worth measurements of pure isotopic samples of various actinides from 232Th to 245Cm, it represents a unique set experimental data to validate evaluated nuclear data. This paper presents the analysis of the experiments conducted in a MOXLWR-type core configuration, with TRIPOLI-4® Monte-Carlo calculations. The comparison between calculated and measured reactivity worth shows a good agreement with JEFF-3.1.1 for all the actinides, except 241Am. The combination of the C/E results with the sensitivity coefficients and prior covariances in a re-estimation process suggests that some improvement is required on the 241Am (n,g), towards an increase of +6% of the JEFF-3.1.1 thermal capture cross section. Based on the same reestimation process, improvements in the nuclear data covariances are pointed out, with posterior uncertainties on the reactivity worth significantly reduced for 238Pu, 239Pu, 241Am, 237Np and 244+245Cm.