Measurement of Cross Sections for the ²³Na(n, n′γ)²³Na Reaction near Threshold

Cross-section ratios for production of 0.439-MeV gamma rays near 55 deg by the ²³Na(n, n′y)²³Na reaction relative to fast-neutron fission of ²³⁵U have been measured with an error of ±8% at intervals of 0.05 MeV from threshold up to ∼2 MeV, with an average neutron energy resolution of ∼0.07 MeV. Gamma-ray angular distributions were measured at E_n = 0.644, 0.793, 1.093, 1.245, 1.499, 1.799, and 2.044 MeV. The measured ratios and ENDF/B-IV fission cross sections were used to compute gamma-ray production cross sections. The experimental results are compared with data from the literature, and implications for liquid-metal fast breeder reactor technology are discussed.