Bayesian Based Uncertainties of Neutron-Induced Reaction Cross Sections of Mn-55

Bayesian Based Uncertainties of Neutron-Induced Reaction Cross Sections of Mn-55

The extreme conditions in a future fusion reactor require a careful selection of materials with regard to activation and aging. Of particular interest for a proper choice is the availability of high quality evaluated nuclear cross section data files for structural materials which comprise reliable covariance matrices and cover the energy range up to at least 60 MeV, the envisaged end of the relevant spectrum of the future IFMIF facility. In this contribution emphasis is given to the generation of cross section covariance matrices for a new evaluated data file for neutron-induced cross sections of Mn-55 between 1 and 150 MeV. The evaluated file takes into account experimental data of the EXFOR data base and is generated by Bayesian statistics via the code GENEUS. Due to the scarcity of experimental data beyond 20 MeV, the prior, based on the nuclear model set of TALYS-1.0, plays an essential role for the reliability of the file in this energy regime. Therefore much effort was devoted to an optimized choice of the model parameters for the range 20 ≤ Z ≤ 28. Employing the recent formalisms a prior including parameter uncertainties and model defects was evaluated by GENEUS and used as a starting point of the evaluation process. In addition a careful analysis of experimental data was performed to estimate the covariance matrices of the experiments, which are used by GENEUS in the Bayesian procedure. The quality and the specific features of the evaluated data file and associated uncertainties are discussed.

The extreme conditions in a future fusion reactor require a careful selection of materials with regard to activation and aging. Of particular interest for a proper choice is the availability of high quality evaluated nuclear cross section data files for structural materials which comprise reliable covariance matrices and cover the energy range up to at least 60 MeV, the envisaged end of the relevant spectrum of the future IFMIF facility. In this contribution emphasis is given to the generation of cross section covariance matrices for a new evaluated data file for neutron-induced cross sections of Mn-55 between 1 and 150 MeV. The evaluated file takes into account experimental data of the EXFOR data base and is generated by Bayesian statistics via the code GENEUS. Due to the scarcity of experimental data beyond 20 MeV, the prior, based on the nuclear model set of TALYS-1.0, plays an essential role for the reliability of the file in this energy regime. Therefore much effort was devoted to an optimized choice of the model parameters for the range 20 ≤ Z ≤ 28. Employing the recent formalisms a prior including parameter uncertainties and model defects was evaluated by GENEUS and used as a starting point of the evaluation process. In addition a careful analysis of experimental data was performed to estimate the covariance matrices of the experiments, which are used by GENEUS in the Bayesian procedure. The quality and the specific features of the evaluated data file and associated uncertainties are discussed.