Corrosion of Austenitic Stainless Steels Exposed to Mixtures of Plutonium Oxide and Chloride Salts

Pitting and stress corrosion cracking have been observed in 304L and 316L stainless steels exposed to mixtures of plutonium oxide and chloride salts containing small concentrations of water.  Pit depths and areal densities were measured in metal that was in contact with the solid mixture as well as in metal in contact with the helium headspace gas.  The stress corrosion cracking had the familiar transgranular character along with an intergranular morphology associated with the heat-affected zone of an autogenous weld.  The cation of the chloride salts significantly affected the presence and extent of corrosion, with calcium chloride being the more aggressive.  The nature of this influence is not well understood, but is evidently based on the compounds’ affinity for water.  The growth of radiolytic products in the headspace gas was extensively analyzed, and some of these results will be presented