Fission-Product Release from Monogranular UC₂ Particles

The fission-product release of spherical monogranular UC₂ particles is studied by postirradiation annealing of neutron-activated samples and by exposing samples to a steady rate of photofission. The release of the several fission products studied appears to follow the kinetics and temperature-dependence of an activated diffusional process. The anomalous fast release of a portion of the Xe¹³³ in annealing experiments may be interpreted as being due to release of attached or trapped xenon atoms by a process not following Fick's law. Analysis of the data obtained gives the following diffusion coefficients for krypton, tellurium, iodine, xenon and barium in UC₂ (in cm²/sec): The diffusion coefficient for xenon in UC₂ shows agreement with the diffusion coefficient for xenon in UO₂. A negative activation entropy (-13 eu) for diffusion is indicated.