Work

Removing oxygen-derived impurities from molten chloride fuel salts with aluminium chloride: Effectiveness and limitations

Year: 2026

Type: article

Abstract: Growing electricity demand has renewed interest in chloride-based molten salt reactors. However, oxygen ingress during operation can raise the redox potential, accelerating corrosion and promoting fuel loss through uranium oxide formation, while removal methods for operating reactors remain underdeveloped. In this study, aluminium chloride is investigated for removing oxygen-derived impurities and inhibiting uranium oxide formation during operation. Within the salt, aluminium chloride was effective: the oxide ion removal efficiency exceeded 93%, UO 2 was effectively converted to UCl 4 after 24 h at 700 °C, while U 3 O 8 also underwent conversion to soluble uranium species. However, its ability to restore the redox state was limited. Using the Sm 2+ /Sm 3+ couple as an analogue for the U 3+ /U 4+ system, once the redox state had been disturbed by oxygen, it could not be recovered even after the oxo-species were removed. These results indicate that oxygen is better removed in the cover gas before it reacts with the molten salt. Given its high volatility, gaseous aluminium chloride is well suited to this purpose, as supported by thermodynamic calculations, although experimental verification remains future work. Some Al 2 O 3 inevitably remains in the salt, and its possible effects on the thermochemical properties of the molten salt require further study.

Source: Nuclear Engineering and Technology

DOI: 10.1016/j.net.2026.104629