Inner barrier shape symmetries in 237Np neutron data evaluation up to 40 MeV incident energy

Abstract

The 237Np neutron induced cross-section evaluation up to 40 MeV incident energy is made in consistent way, based on models with all parameters in agreement with experimental data, theoretical and statistical considerations. The resulted cross-sections describe very well the existing experimental data without any re-normalization and adjustments. The shape symmetry change at the inner fission barrier for the Np isotopes is determined on the basis of an original systematic, the fission level density and the fission barrier parameters being obtained according with these symmetries. The prompt fission neutron multiplicity and spectra of n + 237Np are calculated with a refined model that takes into account the entire fission fragment range with a point-by-point treatment. In the incident energy range where multiple fission chances are involved the average values of the model parameters are determined by point-by-point treatment. The prompt fission neutron multiplicity and spectra, as well as the average prompt gamma-ray energy are obtained in very good agreement with the existing experimental data. The systematic behaviours of the model parameters as function of quantities in connection with the respective Np fissioning nuclei are also obtained in the frame of this work.