Abstract:

The growth of uranium dendrites is a potential threat factor that leads to accidental short circuit in the electrolytic refining unit of spent fuel reprocessing，and at the same time，it will incline a lot of molten salt in the uranium product，which will affect the purity of the product.In order to better understand the microscopic mechanism of uranium dendrite growth and grasp the control method of cathode deposition morphology，an electrodeposition model of uranium in cathode was established based on the phase field method.The dependence of topography parameters such as bottom deposition width，main dendrite height and total deposition area on the change of flow field velocity was studied.It was found that the introduction of external flow field could reduce the bottom deposition width of uranium dendrites by 37.18%，the main dendrite height was lowered by 30.5%，and the total deposition area was decreased by 49.3%.The results showed that the applied flow field could inhibit the growth of uranium dendrites and improve the morphology of uranium deposition，but at the same time，the broken dendrites would be redissolved into the molten salt system，and the efficiency of uranium electrolytic refining would be reduced.In addition，through the analysis of the phase diagram of uranium dendrite morphology under the coupling effect of deposition conditions such as flow field，electrolytic voltage and initial concentration，it could be seen that in the actual electrolytic refining process，a higher initial concentration and a lower electrolytic voltage should be selected as far as possible on the basis of ensuring the efficiency of electrolytic refining，and a reasonable flow field velocity should be set to obtain an ideal uranium dendrite deposition morphology.

Key words: uranium dendrite growth, phase field method, flow field