The Investigation of the Resonance Self-shielding Effect in the α-Value of 235U, 239Pu over the 4.65-2150 eV Energy Range

Abstract

The time-of-flight spectra from the 1-st to 15-th multiplicities were measured on the 122 m flight path of the IBR-30 pulsed neutron booster using the 16-section liquid scintillation detector with the 80 I total volume1) for thin metallic 235U and 239Pu radiator-samples at the presence of 235U filter-samples with three thicknesses and 239Pu filtersamples with four thicknesses in the neutron beam and without them.Multiplicity distribution spectra, average multiplicities and alpha values α = αγ / σf were obtained from time-offlight spectra after subtracting background components for resolved resonances over the energy range of 7-170 eV and in the energy group within the range of 4.65-2150e V with and without filter samples of 235U and 239Pu.The decreasing of a resonance self-shielding effect in the alpha value by 5-50% and an increase in an average multiplicity by 10-35% with the increasing thickness of a filter sample are observed.