Influence of plutonyl ion on electrochemical characterization of zirconium in plutonium nitrate solutions

Abstract

Abstract With the aim of evaluating the corrosion behavior of a Pu evaporator made from Zr in the Rokkasho Reprocessing Plant (RRP), the electrochemical characterization of Zr was investigated in Pu nitrate solutions. Before and after experiments, spectra of Pu nitrate solutions were recorded, and Pu4+ was oxidized to PuO2 2+ by heating these solutions. The ratio of PuO2 2+ in 3 mol dm−3 HNO3 was higher than that in 7 mol dm−3 HNO3 in our experiments. The maximum open circuit potential of Zr in the Pu nitrate solution was approximately 1 V in the Pu nitrate solution containing 7 mol dm−3 HNO3. However, there were no significant changes at high PuO2 2+ concentrations, and this value remained below the passivity breakdown potential under our experimental conditions. In this study, Zr showed high corrosion resistance, even though many PuO2 2+ ions existed in the Pu nitrate solution containing 7 mol dm−3 HNO3.