Nuclear Photofissility at Intermediate and High Energies

The nuclear photofissility of actinides, at intermediate and high energies, was studied by means of a formalism which makes salient the aspects of preequilibrium emissions, compound nucleos formation, and fission decay of the equilibrated system. This formalism was applied in the interpretation of the recently measured photofissilities of 232Th and 238U, in the energy range 300-1200 MeV, using (a) an intranuclear cascade Monte Carlo calculation to describe the preequilibrium and thermalization processes, and (b) the statistical model for the fission decay of the compound nucleos. It was found that the nonsaturation of the 232Th photofissility, even at energies up to 1200 MeV, could be explained as a consequence of its higher nuclear trasparency, when compared with heavier actinidies. Also, the question about a possible competition between statistical and direct fission in 232Th and 238U was addressed.