Oxidative dissolution of ruthenium deposits onto stainless steel by permanganate ions in alkaline medium

During spent nuclear fuel reprocessing ruthenium is liable to form black ruthenium deposits oil the stainless steel walls of process equipments. These deposits promote corrosion and can eventually obstruct the off-gas lines. The results of decontamination of 304L stainless steel test specimens covered with RuO(OH)(2)center dot xH(2)O deposits by permanganate ions in alkaline medium are described. The ruthenium deposits were dissolved by oxidation of RUO(OH)(2) to RUO42- ions, while the permanganate ions were reduced to MnO42- ions and then to manganese dioxide MnO2. The parameters affecting the kinetics of oxidative dissolution of these deposits were examined. The results indicate that the oxidative dissolution kinetics depends on the instantaneous surface area of the deposit, and that the dissolution rate increases with the concentrations of MnO4- and OH- ions.