Nonfission Inelastic Events in Uranium and Thorium Induced by High-Energy Protons

Activation cross sections for about thirty products of high-energy proton-induced disintegration of ${\mathrm{U}}^{238}$ and ${\mathrm{Th}}^{232}$ have been measured by the radiochemical method. These products range from polonium ($Z=84\mathrm{}$) to neptunium ($Z=93\mathrm{}$). The energy dependence of some of these cross sections has been determined for formation from ${\mathrm{U}}^{238}$. Because of fission competition, the spallation cross section of ${\mathrm{U}}^{238}$ is considerably less than that of ${\mathrm{Th}}^{232}$. The data suggest that light isotopes of uranium are primarily responsible for the fission generally associated with high-energy particle bombardment of ${\mathrm{U}}^{238}$.