Long-term variation in nuclide activities under laser ablation of metallic targets in aqueous solutions of uranium salt

Abstract

The long-term variation in the activities of nuclides belonging to the uranium series after laser irradiation of metallic targets (Au, Be, Al, Ti) in aqueous solutions of UO2Cl2 has been experimentally investigated. It is found that the activity of 234Th, in contrast to unirradiated solution, continues to increase for 50 to 60 days after laser irradiation and, having reached a stationary level, remains at it for a long time (about 1 yr). The activity dynamics is modeled theoretically on the assumption that a fraction of 238U in the irradiated solution is under peculiar conditions, so that its half-life ismuch shorter than that of spontaneous α decay of this nuclide under normal conditions. Possible mechanisms of variation in the shape of the potential barrier for α-particles in the presence of nanoparticles formed by laser ablation of targets are discussed.