Electrochemical properties and dissolution of U-5 wt % Zr Alloy in HNO3 solutions

Abstract

The main parameters of dissolution of U-5 wt % Zr alloy in HNO3 solutions were determined by linear voltammetry. Without applying external potential, the electrode potential E 0 in 0.5–6.0 M HNO3 solutions increases. Its value is determined by the formation of a film containing hydrated Zr(IV) and U(IV) oxides and by the cathodic reduction of the acid. The reduction of NO3 — ions on the surface of U-5 wt % Zr alloy in 0.5–6.0 M HNO3 occurs with high overvoltage. In experiments without applying external potential, an increase in the HNO2 yield in accordance with this reaction leads to an increase in the alloy dissolution rate with an increase in the HNO3 concentration in the electrolyte from 0.5 to 6.0 M. At potentials higher than 450 mV vs. Ag/AgCl electrode, the U-5 wt % Zr electrode undergoes transpassivation. Data on the electrolysis at controlled potential in the region close to the transpassivation potential showed that an increase in the electrode potential at the given HNO3 concentration leads to an increase in the alloy dissolution rate.