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Ouchi, Kazuki; Otobe, Haruyoshi; Kitatsuji, Yoshihiro; Yamamoto, Masahiro
ECS Transactions, 75(27), p.51 - 57, 2017/01
Times Cited Count：1 Percentile：38.46(Electrochemistry)We investigated the deposition of U(IV) following a valence change of U as electrodeposition using an electrochemical quartz crystal microbalance (EQCM). When measurements of the reduction of U(VI) in a weak acid solution were performed, deposits of U(IV) were observed on the electrode surface. From deposition rates, pH dependence of them, and oxidation potentials of deposits, we proposed the following deposition mechanism. The deposition is divided into the three phases; First, in the induction phase, U(IV) produced by the disproportionation forms U(IV) hydroxide nucleus. Next, in the growth phase, U(IV) deposits begin to grow. In this phase, the deposits catalyze the reduction of U(V) to U(IV), resulting an increase of the reduction current. Finally, in the transformation phase, U(IV) hydroxide species transform into U dioxide having more stable state.
Yamamoto, Masahiro; Kato, Chiaki; Motooka, Takafumi; Irisawa, Eriko; Ban, Yasutoshi; Ueno, Fumiyoshi
no journal, ,
Stainless steels used in nuclear fuel reprocessing plant occur intergranular corrosion by boiling nitric acid solution containing some cations. Reduction reaction of these cations accelerates corrosion rate of stainless steel, and then, they are re-oxidized to initial state in bulk nitric acid solution. These re-oxidized cations repeatedly concern corrosion reaction of stainless steel. The re-oxidation rates of typical cations were analyzed in the present work. As the result, Np ion accelerates corrosion of stainless steel in a little amount because it has both large reduction reaction rate and re-oxidation rate.
