During a hypothetical severe accident in a pressurized water reactor (PWR), fission products (FPs) are released from the nuclear fuel and may reach the reactor containment building. Among the FPs, ruthenium is of particular interest due to its ability to form volatile oxide compounds in highly oxidizing conditions. In addition, ruthenium is a very hazardous compound because it is chemically toxic and also because of its radiotoxicity.

The topic of ruthenium is examined in terms of nuclear safety issues. A review of the literature regarding ruthenium oxides properties, gaseous and aqueous chemistry is compiled. The study focuses on ruthenium tetroxide (RuO4), which is highly reactive and volatile and is the most likely gaseous chemical form under the conditions prevailing in the containment. The interactions between ruthenium oxides and containment surfaces, which could be most important in overall ruthenium behavior, are also discussed. Finally, an evaluation of the possible revolatilization phenomena of ruthenium adsorbed on PWR containment surfaces or dissolved in the sump under superoxidizing conditions (radiolysis) is also presented. In this case, ruthenium dioxide (RuO2) must also be considered.

Knowledge of all these phenomena is required to accurately predict ruthenium behavior and to make a best-estimate assessment of the potential ruthenium source term.