Release of Fission Cesium from Irradiated UO₂ Powder

Abstract

The amount of Cs released from irradiated UO² powder in a range of temperature between 820°and 980°C was measured by sweeping with H²-1%HCL mixture.This mixed gas proved effectively to carry off the released Cs from the UO² surface, as verified by observation of the characteristics of CsCl adsorption on UO² and desorption therefrom. In addition, the amount of Cs released by knock-out during irradiation was measured. The chemical form of Cs adsorbed on the UO² surface after release by knock-out, is considered to be elemental. The activation energy for Cs migration in UO² is discussed, with account taken of the difference in behavior between single-crystals and poly-crystals.