ABSTRACT
This chapter presents a summary of ruthenium behaviour, measured in experiments at the Chalk River Nuclear Laboratories. The importance of the study of ruthenium release behaviour in accidents is twofold. First, the toxicity of the volatile Ru oxides and the radiation hazards of the two radioactive Ru isotopes must be considered in accident-evaluation studies. Secondly, the Ru release characteristics in oxidizing environments are so specific that understanding the kinetic behaviour of ruthenium releases will be most useful for post-accident management analysis. The release characteristics and kinetics of ruthenium isotopes, their dependence on oxygen partial pressure, and the comparison with the release of other fission products are discussed. In steam and air environments, since uranium oxides are thermodynamically more stable, ruthenium oxides should only form in an oxidizing atmosphere after some local oxidation of UO2 has occurred. In an air atmosphere, ruthenium releases have been measured at temperatures above 970 K.
