Prompt fission neutron multiplicity and spectrum evaluations for n+U-238 reaction

The prompt fission neutron multiplicity and spectra for n+U-238 reaction ar e calculated using an improved Los Alamos model which includes the linear r elation between the average prompt gamma ray energy and the prompt neutron multiplicity and also the average fission fragment kinetic energy dependenc e on the incident neutron energy. The coefficients describing the quadratic variation of the fission fragment kinetic energy versus the incident energ y are obtained by extrapolation of the data and procedure used for n+U-235 reaction. The inverse process compound nucleus cross-section of the fission ing nucleus is calculated using the coupled channel method. In the incident energy range where only the first fission chance is involved the compariso n of present spectrum evaluation with spectrum calculation using multi-moda l model is made too. The calculated prompt neutron multiplicity and spectra of U-238 neutron induced fission are in good agreement with the experiment al data for the entire incident energy range required in evaluations, provi ng the validity of the used procedure. (C) 2001 Elsevier Science Ltd. All r ights reserved.