Evaluation of Prompt Neutron Spectra from Fission of Americium Isotopes

Abstract

With the development of extended burnup of nuclear fuel and incineration of long-lived actinide nuclides, the need for accurate nuclear data for transplutonium isotopes has been rising. The prompt neutron spectra, among others, are required for shielding calculation of transportation casks and reprocessing facilities as well as reactor core calculation. The authors have proposed a method of calculation of the prompt neutron spectra based on the Madland-Nix model extended to consider the multimodal nature of the fission process. This method was applied to U, Np, and plutonium isotopes with satisfactory results. The method was applied to americium isotopes (Am, Am, Am) to obtain the spectra for incident neutron energies up to 5 MeV. Difficulties in applying the method to Am isotopes lay in the fact that detailed multimodal analyses of fission have not been made for these nuclides. We solved these problems by making the best use of systematics. The calculated spectra were compared with experimental data when possible.