Neutron-Absorption Cross Sections of Some Radioactive Nuclides

We describe a simple method for determining the neutron-absorption cross sections of radioactive nuclides and its application to ²²Na and ¹²⁶I. These nuclides are produced by fast-neutron reactions in cadmium-wrapped and unshielded samples simultaneously irradiated with cobalt flux wires. Values for the thermal cross section, σ₀, the resonance integral, Σ′, and s₀ are calculated from the data using the Westcott convention. The results are as follows: for ²²Na, σ₀ = (5.11 ± 0.31) × 10⁴ b, s₀ = 2.3 ± 0.1, and Σ′ = (1.0 ± 0.1) × 10⁵ b; for ¹²⁶I, σ₀ = (9.0 ± 5.0) × 10³ b.