Resonance Absorption of Neutrons by Uranium Cylinders

Abstract

The integrated effective resonance neutron absorption cross section of uranium‐238 cylinders has been experimentally investigated in the Hanford Test Pile. The results of reactivity measurements were interpreted to yield the effective resonance integral as a function of the surface‐to‐mass ratio of the uranium cylinders. The experiments were extended to determine the Doppler coefficients resulting from heating the uranium in a constant neutron spectrum in the reactor. The effective resonance integral, ${\displaystyle \int }{\mathrm{(\sigma }}_{\text{a0}}{)}_{\mathrm{eff}}\mathrm{dE\prime /E\prime }$ , can be approximated as a function of the surface‐to‐mass ratio by $${\displaystyle \int }{\mathrm{(\sigma }}_{\text{a0}}{)}_{\mathrm{eff}}d\frac{\mathrm{E\prime }}{\mathrm{E\prime }}\text{=6.0}\left\{\text{1+15.6}\frac{S}{M}\left[\text{1−2.18}\frac{S}{M}\text{+2.19}{\left(\frac{S}{M}\right)}^2\right]\right\}$$ . The Doppler coefficient of resonance escape probability for the reactor is $$\frac{1}{p}\frac{\mathrm{\partial p}}{\mathrm{\partial T}}{\text{=(−2.14±0.16)10}}^{\text{−5}}{/}^{\circ }\mathrm{C}$$ , and the value assigned to the coefficient of the volume absorption of the resonance integral is $$\frac{1}{A}\frac{\mathrm{\partial A}}{\mathrm{\partial T}}{\text{=(1.56±0.12)10}}^{\text{−4}}{/}^{\circ }\mathrm{C}$$ .