Oxidation of ruthenium oxide deposits by ozone
Résumé
During a hypothetical severe accident on a nuclear Pressurized Water Reactor (PWR), the formation of highly radiotoxic RuO4(g) may occur in the reactor containment building, resulting from the interactions of ruthenium oxide deposits with the oxidising medium induced by air radiolysis. Consequently, there is a risk that the gaseous ruthenium tetroxide could be dispersed into the environment through containment leakages; therefore data concerning the behaviour of ruthenium oxide deposits is of primary importance for safety studies. An experiment has been designed to study the interactions of ruthenium oxide deposits with ozone, formed by air radiolysis. Experimental results have shown that the oxidation reaction leading to the formation of RuO4(g) occurred to a large extent. An oxidation kinetic rate law has been determined, in dry and moist air, for ruthenium deposited onto painted substrates, representative of the inner surfaces of PWR's. This law, combined with tetroxide stability data [1], will allow a first evaluation of ruthenium revolatilisation phenomenon, possibly occurring in the containment during a severe accident. © by Oldenbourg Wissenschaftsverlag.