抄録
The effects of polarization in the electrorefining of spent nuclear fuel were analytically studied through electrotransport experiments with uranium. When the uranium concentration in molten salt was set at 0.5wt%, polarization caused the measured cell resistance to increase from 0.16 to 0.33Ω as the cell voltage was raised from 0.1 to 0.7V. At 2.0wt% uranium concentration in salt, on the other hand, the resistance was almost independent of cell voltage. A code named DEVON has been developed to estimate the effects of polarization on the electro- refiner operating condition. The Laplace equation is solved in the bulk salt region by finite element method. In the calculation, the effects of polarization are taken into account by adopting the diffusion layer model on defining the boundary conditions. The result of calculations agreed well with the measured resistance data at two sample concentrations for a diffusion layer thickness of 0.025cm on the solid cathode. The calculations indicated that significant polari- zation at the cathode could be avoided by maintaining the uranium concentration in salt above 1 to 2wt%. When it was held at 5wt%, which is a typical level for normal operation, polarization proved to exert little influence on the cell resistance, but it was indicated to contribute appreciably toward flattering the current distribution along the cathode surface.
