Electrochemical Behavior of CsI in LiCl Molten Salt

Sung-Wook Kim,Min Ku Jeon,Sang-Kwon Lee,Eun-Young Choi,Peter Ivanov

doi:10.1155/2020/8852351

Sung-Wook Kim, Min Ku Jeon + Show 3 more

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https://doi.org/10.1155/2020/8852351

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Abstract

The electrochemical behavior of CsI in LiCl molten salt was investigated to identify its impact on the electrolytic oxide reduction of oxide-phase spent nuclear fuels by combined electrolysis and cyclic voltammetry experiments of LiCl-CsI in comparison with LiCl, LiCl-CsCl, and LiCl-LiI. It was found that Cs+ ions were hardly involved in the cathode reaction, and reduction of Li+ ions occurred dominantly in the cathode. In contrast, incorporation of I− ions induced low-potential anode reaction compared with the I− ion-free cases. Such additional electrochemical reaction resulted in the generation of I2 and/or ICl gases, which would increase a process burden for treating 129I with exceptionally long lifetime. In this respect, separating CsI from spent nuclear fuel before the electrolytic oxide reduction is recommended for the purpose of efficient waste management.

Highlights

Electrolytic oxide reduction (EOR) has been developed as a technical option of oxide reduction in pyroprocessing [1,2,3]
For the cyclic voltammetry (CV) investigation, the Ni wire working electrode and the graphite rod counterelectrode were used, and an additional Ni wire was employed as a quasi-reference electrode (QRE). e electrolysis experiment was controlled by a power supply (E3633A, Keysight), and the CV experiment was conducted using a potentiostat (PGSTAT362N, Autolab). e electrolysis product recovered from the cathode was dissolved into deionized water for chemical analysis
It means that the existence of I− ions in the LiCl electrolyte induces the additional electrochemical reaction during the EOR process

Summary

Introduction

Electrolytic oxide reduction (EOR) has been developed as a technical option of oxide reduction in pyroprocessing [1,2,3]. E EOR process generally utilizes LiCl molten salt (at 650°C) as an electrolyte [4,5,6]. Due to the nature of electrochemical reactions, the EOR process can be divided into two parts: the reduction of SNFs at the cathode and the gas evolution at the anode. Several fission products (e.g., Cs, Ba, and Sr) in SNFs are highly soluble in LiCl molten salt, and they are thought to accumulate in the electrolyte during the EOR process [4, 5]. It was reported that that the dissolution of Ba and Sr in the LiCl electrolyte has little effect on the EOR process [5, 10]. Because the dissolution of CsI to the LiCl electrolyte provides I− ions, the impact of I− ions on the EOR reaction needs to be identified

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