Effect of Deposit on the Evaporation Rate of Adhered Salt in Uranium Dendrite

Sang Woon Kwon,Sung Jai Lee,Si Woo Park

doi:10.1155/2020/8866234

Abstract

Electrorefining is a key step in pyroprocessing. The solid cathode processing is necessary to separate the salt from the cathode of the electrorefiner since the uranium deposit in a solid cathode contains electrolyte salt. Moreover, it is very important to increase the throughput of the salt separation system due to the high uranium content of the spent nuclear fuel and high salt fraction of uranium dendrites. Therefore, in this study, the effect of deposit on the evaporation of the adhered salt in a uranium deposit was investigated by using the samples of salt in the uranium deposit and salt in the deposit of the surrogate material for the effective separation of the salt. It was found that the salt evaporation rate is dependent on the deposit type and bulk density in the crucible. Additionally, the evaporation rate was found to be lower when the deposit structure is complex; the rate also decreases as the bulk density of the deposit is increased owing to the retardation of the salt vapour transport process. It was concluded that the mass transfer of the salt vapour is an important parameter for the achievement of a high throughput performance in the salt distillation process.

Highlights

Pyroprocessing is a promising way for the recovery of actinide elements from the used nuclear fuel [1,2,3,4]
Surrogate deposits were used for the investigation of type effect because the uranium deposits with various morphologies were difficult to prepare in the electrorefiner. e samples were prepared with LiCl-KCl eutectic salt powder and/or surrogate deposits to examine the effects of the deposit type on the evaporation rate under the condition of a 59/41 mole fraction ratio of lithium to potassium
It was found that the salt evaporation rate is dependent on the deposits in the crucible because the evaporation rate of the adhered salt influences the expulsion of the salt vapour. us, it could be concluded that the mass transfer of the evaporated salt is an important parameter needed to enhance the throughput of the distilled salt adhered to cathode deposits. erefore, the distiller geometry must be designed to optimize mass transfer such that high throughput performance can be achieved in the salt separation process

Summary

Introduction

Pyroprocessing is a promising way for the recovery of actinide elements from the used nuclear fuel [1,2,3,4]. Electrorefining, which is a key process in pyroprocessing, generally comprises two recovery steps: (1) deposition of uranium onto a solid cathode and (2) the recovery of actinide elements by a liquid cathode. E cathode deposit in pyroprocess is uranium dendrites coated by eutectic salt loaded with fission product chlorides. E purpose of the solid cathode processor is to remove entrained salt from the uranium electrodeposited and to consolidate the dendritic deposits. E cathode process has two separate steps of a salt separation and a consolidation of uranium deposits at the Korea Atomic Energy Research Institute. In vacuum distillation separation, which is possible because of the difference in vapor pressures between salt and uranium, a solid cathode deposit is heated in a predetermined heating region, thereby vaporizing the salt and leaving behind the nonvolatile uranium

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Results

Conclusion