Electrochemical properties of zirconium in highly concentrated plutonium nitrate solution

To evaluate the corrosion resistance of a Pu evaporator made of Zr in the Rokkasho Reprocessing Plant (RRP), the electrochemical properties of Zr were evaluated in highly concentrated aqueous Pu nitrate solutions. The open circuit potential of Zr in the Pu nitrate solution increased with increasing temperature, and with increasing HNO3 and Pu concentrations. At the boiling point, Pu and PuO2 co-existed in the Pu nitrate solution. To evaluate the influence of PuO2 on the corrosion potential of Zr, the polarization curve of the Pu nitrate solution containing a high concentration of PuO2 with 5 mol dm HNO3 and 250 g dm Pu was measured. The corrosion potential of Zr stayed in the passive region. The influence of PuO2 was not significant in highly concentrated Pu nitrate solution. These results suggest that Zr shows high corrosion resistance, even in highly concentrated Pu nitrate solution.