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Glass cell provides glimpse inside molten salt reactors

Tuesday, 6 August 2024

A custom-made glass test cell created by Oak Ridge National Laboratory has enabled researchers to observe how gases behave inside a molten salt reactor and investigate the complex chemistry that can occur in the molten salt solution.

Glass cell provides glimpse inside molten salt reactors — Scientific glassblower Carlos Rodriguez Flores is seen fabricating the glass cell (Image: ORNL)

Some of the reactors that are currently being designed will operate on liquid fuel, where the fissile materials are directly dissolved in a molten salt solution that also acts as the reactor's coolant. But nuclear and chemical reactions can result in gases that bubble out of the molten salt, which can impact reactor neutronics and thermal hydraulic performance.

The glass test cell fabricated to visualise noble gas behaviour in a molten salt column (Image: ORNL)

To help investigate these effects, ORNL researchers designed and developed a customised glass test cell that can hold up to a litre of liquid molten salt. They injected small helium and krypton bubbles into the cell to observe how they moved through the column of molten salt, and were able to measure gas bubble velocity, size distribution, and interactions with neighbouring bubbles using high-speed cameras. The insights provided from the experiment will be used to help improve and validate simulation tools for molten salt-fuelled systems.

"Understanding gas generation and transport in molten salt reactors is essential to optimising their performance and safety," said Daniel Orea, ORNL lead R&D associate. "This unique glass test cell allows us to overcome certain engineering challenges caused by the high temperature and composition of salt and its two-phase liquid glass system."

The research project was supported through the US Department of Energy's Molten Salt Reactor Program.