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 = α_γ / σ_f 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.

Keywords:

• time-of-flight spectra
• multiplicity of gamma ray
• scintillation detector
• alpha value
• neutron
• fission and capture cross section
• uranium 235
• plutonium 239
• resonance self-shielding effect