Improved Los Alamos model applied to the neutron induced fission of 235U and 237Np

The Los Alamos model, with multiple ®ssion chances, was upgraded to include the linear rela- tion between the average prompt gamma ray energy and the average prompt neutron multiplicity. A global, model-free parameterization of this relation versus the charge and mass number of ®s- sioning nuclei is obtained. The average ®ssion fragment kinetic energy dependence on the incident neutron energy is also taken into account. Employing this model for the n+235U and n+237Np reactions, the prompt ®ssion neutron spectra, the average prompt neutron multiplicity and the average prompt gamma ray energy are obtained in very good agreement with the experimental data, proving a better predictive power