Group constants and characteristics of the neutron cross-section structure for 232Th, 240Pu and 242Pu in the unresolved resonance region

Using the latest evaluations of mean resonance parameters for 232Th, 240Pu, 242Pu, group constants are obtained in the region of unresolved resonances (mean cross-sections and resonance self-shielding factors). The results obtained are consistent with the Breit-Wigner formula and the systematics of mean resonance parameters from the optical model. There is lack of experimental data on transmission, which are necessary in order to make a more clearly defined choice of mean resonance parameters and a more accurate definition of resonance self-shielding factors