Abstract
The anodic dissolution behaviours of Cu, Zr and Cu–Zr alloy were analysed in LiCl–KCl at 500°C by anode polarization curve and potentiostatic polarization curve. The results show that the initial and fast-dissolving potentials of Cu are −0.50 and −0.29 V, and Zr are −1.0 and −0.88 V, respectively. But, in the Cu–Zr alloy, the initial and fast-dissolving potentials of Cu are −0.52 and −0.41 V, and Zr are −0.96 and −0.92 V, respectively. The potentials satisfy the selection dissolution principle that Zr in the alloy dissolves first, while Cu is left in the anode and is not oxidized. The passivation phenomenon of Zr is observed in the quick dissolution of Zr, while it is not observed in the Cu–Zr alloy. Moreover, from the above anodic dissolution results, potentiostatic electrolysis of Cu–Zr alloy was carried out at −0.8 V for 40 min, and the anodic dissolution mechanism and kinetics of Zr in Cu–Zr alloy were also discussed. In the initial stage, Zr dissolves as Zr4+ ions from the alloy surface and enters into the molten salt, leaving a Cu layer called ‘dissolving layer’ on the surface of the alloy. After that, another layer between the matrix and ‘dissolving layer’ called ‘diffusion–dissolution layer’ appears. Zr diffuses in the alloy matrix and dissolves as Zr4+ ions on the surface of the ‘diffusion–dissolution layer’ continuously, and Zr4+ ions diffuse through the ‘dissolving layer’ and enter into the molten salt finally. In addition, the factors affecting the dissolution of Cu–Zr alloy, such as time and potential, were also investigated. The dissolution loss increases with the increasing dissolution potential and time, while the dissolution rate increases with the increasing dissolution potential and declines with the prolonging dissolution time.
Highlights
Nuclear energy, as a kind of clean energy, has the characteristics of high efficiency, safety and economy
The dissolution loss increases with the increasing dissolution potential and time, while the dissolution rate increases with the increasing dissolution potential and declines with the prolonging dissolution time
Steady-state anode polarization curve and potentiostatic polarization curve of Cu were performed for determining the anode dissolution potential of Cu
Summary
As a kind of clean energy, has the characteristics of high efficiency, safety and economy. A low-melting point Cu –Sn–Zr alloy or Cu–Zr alloy serving as a liquid anode is proposed by our research group, while the highly pure zirconium can be deposited on the cathode, and the electrorefining process preformed in in situ prepared LiCl– KCl– ZrCl4 molten salt, which has been reported in our further works [10 –12]. A few papers [13,14,15,16,17,18,19] have been published earlier on the anodic dissolution of spent nuclear fuels, such as U–Pu –Zr, U–Zr fuels, and the dissolution potentials of U, Pu, Zr and U–Pu– Zr alloy were analysed. We have not come across any literature where anode polarization curve and potentiostatic polarization curve have been used to study the kinetics of dissolution of Cu –Zr alloy in the molten salt. The anodic dissolution mechanism and kinetics of Zr in Cu –Zr alloy were discussed
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