Improved Los Alamos model applied to the neutron induced fission of 239Pu and 240Pu and to the spontaneous fission of Pu isotopes

The Los Alamos model with multiple ®ssion chances upgraded with (a) the linear relation between the average prompt gamma ray energy and the average prompt neutron multiplicity and (b) the dependence of the average ®ssion fragment kinetic energy on the incident neutron energy, is used for the n+239Pu and n+240Pu reactions, and also for the spontaneous ®ssion of 237-241Pu isotopes. In the case of 240Pu ®ssioning nucleus the variation of the average energy released versus the incident neutron energy is also taken into account. The calculated prompt ®ssion neutron spectra and average prompt neutron multiplicity well represent the experimental data, proving a better predictive power of the improved Los Alamos model.