Prompt fission neutron spectra in fast-neutron-induced fission of 238U

Prompt fission neutron spectrum (PFNS) measurements for the neutron-induced fission of ²³⁸U are carried out at incident neutron energies of 2.0, 2.5, and 3.0 MeV, respectively. The time-of-flight technique is employed to determine the energy of fission neutrons. The prompt fission neutron energy spectra so obtained are analysed using Watt parametrization to derive the neutron multiplicity and average prompt fission neutron energy. The present experimental PFNS data are compared with the evaluated spectra taken from the ENDF/B-VII.1 library and the predictive calculations carried out using the EMPIRE-3.2 (Malta) code with built-in Los Alamos (LA) and Kornilov PFNS models. The sensitivity of the EMPIRE-3.2 LA model–calculated PFNS to the nuclear level density parameter of the average fission fragment and to the total kinetic energy is investigated. EMPIRE-3.2 LA model PFNS calculations that use Madland 2006–recommended values [D. G. Madland, Nucl. Phys. A 772, 113 (2006)] of the total kinetic energy and the level density parameter a = A/(10 ± 0.5) compare very well to measured data at all incident neutron incident energies.