Temperature dependence of Cs release during oxidation of Cs-loaded graphite

As one of potential treatments for irradiated graphite (i-graphite) waste, the oxidation method has been attracting more concern due to features of high treating efficiency and significant volume reduction. The release of fission products during oxidation is of great significance for further off-gas decontamination procedures. Focusing on the release behavior of volatile cesium (Cs), Cs-loaded graphite was prepared by impregnation in this work followed by definite distribution and chemical speciation analyzing. Results showed that the increasing temperature and humidity during the oxidation were evidenced to promote the release of Cs compounds, and the chemical speciation of released compounds was prominently dependent on oxidizing temperature. When the oxidation temperature was around 700 °C, Cs 2 O was predominately released with the morphology of spherical particles. When the oxidation temperature was increased to 900 °C, the predominant releasing composition turned to Cs 2 CO 3 with morphologies of both spherical particles and nanorod-like shapes. The different predominant releasing chemical compositions at different temperatures mainly resulted from the kinetics of graphite oxidization and temperature synergistically. These findings will provide theoretical foundations to the environmental evaluation of i-graphite thermal oxidation .