INELASTIC NEUTRON-SCATTERING BY U-235 AND U-238 NUCLEI

Inelastic scattered neutron spectra and fission neutron spectra for U- 235 and U-238 at incident neutron energies of 1.17, 1.79, and 2. 19 Me V were measured by the neutron time-of-flight spectrometer at the Inst itute of Physics and Power Engineering. A solid tritium target was use d as the neutron source. The experimental data were simulated by a Mon te Carlo code. The interaction of beam protons inside the target, the reaction kinematics, and multiple scattering in the samples were taken into account. The data were normalized, with respect to the C(n,n) an d U-235(n,f) standard reaction cross sections. The experimental result s were verified against absolute fission spectrum measurements by usin g well-known fission cross-section and v values. The Maxwell distribut ion parameters for the fission spectra, the fetal inelastic scattering cross sections, and the inelastic scattered neutron spectra were deri ved. The results of this work confirm the ENDF/B-VI evaluations for U- 235. The total inelastic cross sections for U-238 are very close to th ose of ENDF/B-V/I. However, substantial discrepancies exist between ou r experimental data for U-238 and the ENDF/B-V/I and JENDL-3 evaluatio ns concerning the excitation functions for levels between 0.5 and 1.2 MeV and continuum spectra.