Pyrochemical processing and molten-salt reactors have recently garnered significant attention as they are promising options for future nuclear technologies, such as those for recycling spent nuclear fuels and the next generation of nuclear reactors. Both of these technologies require the use of high-temperature molten salt. To implement these technologies, one must understand the electrochemical behavior of fission products in molten salts, lanthanides, and actinides. In this study, a rotating-disk-electrode (RDE) measurement system for high-temperature molten salts is constructed and tested by investigating the electrochemical reactions of Sm3+ in LiCl–KCl melts. The results show that the reduction of Sm3+ presents the Levich behavior in LiCl–KCl melts. Using the RDE system, not only is the diffusion-layer thickness of Sm3+ measured in high-temperature molten salts but also various electrochemical parameters for Sm3+ in LiCl–KCl melts, including the diffusion coefficient, Tafel slope, and exchange current density, are determined.

Molten salt reactor (MSR) is one of the non-pressurized-water fourth-generation reactors that uses liquid nuclear fuel that integrates coolant and nuclear fuel, so it is a safe reactor that can fundamentally prevent severe accidents caused by coolant loss. MSR uses NaCl-MgCl2 as a coolant salt, which is considered a promising diluent that can dissolve the fuel salt by forming an eutectic mixture. In this study, a zone-melting system was used to remove impurities from the NaCl-MgCl2 used in MSR. The system was designed in detail to control eutectic salt impurities by traversing long charges into a small molten zone.

A new method for chemical separation of light rare-earth elements (LREEs) using gas-pressurized extraction chromatography (GPEC) is described. GPEC is a microscale column chromatography system that features a constant flow of solvents (0.1 mL/min), which is created by pressurized nitrogen gas. The separation column with a Teflon tubing was packed with LN resin. We evaluated the separation of Ba, La, Ce, and Nd using various elution solvents. Here, we applied the natural isotopes of LREEs (La-139, Ce-140, and Nd-144) and barium (Ba-138) instead of radioactive isotopes for the preliminary test and reducing unnecessary radioactive waste. The column reproducibility of the proposed GPEC system ranged from 2.4% to 4.9% with RSDs of recoveries, and the column-to-column reproducibility ranged from 3.1% to 6.3% with RSDs of recoveries. This proposed GPEC method provides robust analysis and facilitates production of lesser chemical wastes and faster separation owing to the use of low solvent volume compared to traditional column chromatography.

An important property of glass and ceramic solid waste forms is processability. Tellurite materials with low melting temperatures and high halite solubilities have potential as solid waste forms. Crystalline TiTe3O8 was synthesized through a solid-state reaction between stoichiometric amounts of TiO2 and TeO2 powder. The resultant TiTe3O8 crystal had a three-dimensional (3D) structure consisting of TiO6 octahedra and asymmetric TeO4 seesaw moiety groups. The melting temperature of the TiTe3O8 powder was 820℃, and the constituent TeO2 began to evaporate selectively from TiTe3O8 above around 840℃. The leaching rate, as determined using the modified American Society of Testing and Materials static leach test method, of Ti in the TiTe3O8 crystal was less than the order of 10-4 g·m-2·d-1 at 90℃ for durations of 14 d over a pH range of 2-12. The chemical durability of the TiTe3O8 crystal, even under highly acidic and alkaline conditions, was comparable to that of other well-known Ti-based solid waste forms.