Nuclear explosion experiments to determine nuclear properties of heavy isotopes

Abstract

Results of experiments to determine the properties of heavy isotopes from studies of heavy-element yield curves obtained in nuclear explosions, which cannot be performed in the laboratory, are reported. In most cases, 238U was used as the target element. Measurements of uranium neutron capture cross sections around 20 keV neutron energy in the mass range 242–249 reveal a decrease at mass 244 corresponding to 152 neutrons, presumably due to the “shell effect”. These results agree well with original calculations. No fission competition from mass 242–248 is evident, but a fission-to-capture ratio of 5 for mass 249 appears probable. There is some evidence of thermal fission in the uranium capture chain at 239, 241U and strong evidence of thermal fission in the plutonium capture chain. Strong thermal fission competition is indicated in the neptunium capture chain.