UC Berkeley’s New Molten Fluoride Salt Testbed Takes on Fission and Fusion Energy Challenges
The HEAT Lab’s newly commissioned forced-flow FLiNaK facility provides a versatile experimental platform for high-temperature thermal-fluid research relevant to advanced reactors.
A new high-temperature experimental facility at UC Berkeley is giving researchers the ability to study key thermal-fluid challenges facing next-generation fission and fusion energy systems.
The Forced-Flow Molten Fluoride Salt Testbed was established by Professor Guanyu Su in the HEAT Lab within UC Berkeley’s Department of Nuclear Engineering. The facility has been successfully commissioned and is now supporting its first systematic experimental campaign, led by Nuclear Engineering Ph.D. student Beau Walsh.
The facility circulates molten FLiNaK under conditions representative of many molten-salt nuclear energy applications. It can operate between 500 and 700 degrees Celsius, reach flow rates of up to 60 liters per minute, and maintain a temperature difference of up to 100 kelvin between its hot and cold legs.
Commissioned at Representative Molten-Salt Conditions
The research team successfully commissioned the loop earlier in 2026, demonstrating forced-flow operation at temperatures above 600 degrees Celsius.
With the testbed now operational, researchers can conduct controlled high-temperature experiments and generate data that directly support the development of molten-salt technologies.
First Campaign Focuses on Heat Transfer
The facility’s first systematic research campaign examines heat transfer between molten salt and air using a mini-channel compact heat exchanger. The work is intended to support the development of high-efficiency heat exchangers for molten-salt small modular reactors and microreactors.
Testing compact heat exchangers under flowing-salt conditions will provide experimental data for evaluating high-temperature component performance and validating simulation models for future reactor systems.
Supporting Emerging Fission and Fusion Research
Beyond the initial heat-transfer campaign, the testbed is expected to support several emerging research areas:
- Tritium transport and recovery for fusion blanket systems
- High-temperature, latent-heat thermal energy storage
- Additively manufactured compact heat exchangers for advanced reactors
- Thermal sensors for measuring velocity profiles in molten-salt flows
These research areas position the facility as a flexible experimental platform connecting fundamental thermal-fluid research with component and system development.
By establishing a forced-flow molten-salt capability at reactor-relevant temperatures and flow conditions, the HEAT Lab is building an experimental foundation for advancing heat transfer, tritium recovery, thermal energy storage, heat exchanger design, and flow diagnostics across advanced fission and fusion technologies.