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A key argument against Molten Salt Reactors has been corrosion. Now researchers from the University of Liverpool and Copenhagen Atomics have proven that corrosion is practically eliminated when using purified salts, and that is a major breakthrough on the path towards commercially viable MSR’s.
A groundbreaking study published in the Journal of Nuclear Materials reveals that salt purity is the critical factor in preventing corrosion of 316L stainless steel – a widely used, cost-effective material – in molten salt reactors (MSRs). This discovery paves the way for more affordable, durable, and scalable next-generation nuclear energy systems.
Maulik Patel, PhD, Professor of Nuclear Materials, University of Liverpool, supports the results:
Salt purity is absolutely central to corrosion control in molten salt reactors. These results confirm what decades of research, including work at Oak Ridge during the MSRE era, have pointed toward: if you remove the reactive impurities, molten salts can become a stable and manageable environment for reactor materials. This is a major step forward for the field.
Maulik Patel is co-author of the study.
The challenge: Corrosion in Molten Salt Reactors
Molten salt reactors are a promising technology for clean, affordable, and efficient nuclear energy. However, the harsh, high-temperature environment of molten fluoride salts has historically caused rapid corrosion of structural materials, limiting their commercial viability. Previous solutions relied on expensive, high-nickel alloys, which drove up costs and complicated manufacturing.
Thomas Steenberg, co-founder & VP Critical Materials, Copenhagen Atomics, says:
Hopefully, this study will once and for all silence the 'corrosion myth' that MSR is unfeasible due to corrosion. Using engineering controls is highly preferable to the use of exotic unobtanium alloys.
Maulik Patel is co-author of the study.
The solution: Purified salts extend material lifespan
Researchers from Copenhagen Atomics and the University of Liverpool conducted long-term corrosion tests on 316L stainless steel in both purified and untreated molten salts (FLiNaK and LiThF) at temperatures up to 700°C. The results were striking:
- Untreated salts – containing moisture and oxides – caused severe corrosion, with metal loss, surface degradation, and structural weakening after just 1,000 hours.
- Purified salts, with impurities removed, resulted in negligible corrosion even after 3,000 hours. The steel retained its integrity, with only a thin, protective chromium carbide layer forming on its surface.
Purified salts, with impurities removed, resulted in negligible corrosion even after 3,000 hours. The steel retained its integrity, with only a thin, protective chromium carbide layer forming on its surface.
Why this matters for commercialization
- Cost-Effective Materials: 316L stainless steel is significantly cheaper and more accessible than high-nickel alloys, reducing construction and maintenance costs.
- Enhanced Durability: Purified salts minimize corrosion, extending the lifespan of reactor components and improving operational reliability.
- Scalability: The use of standard industrial materials and proven purification processes makes it easier to scale MSR technology for widespread energy production.
- Safety and Sustainability: Reduced corrosion risks enhance reactor safety, a critical factor for regulatory approval and public confidence.
The path forward
While this study establishes a strong foundation, further research is needed to assess the impact of radiation, fission products, and dynamic reactor conditions on long-term material performance. Optimizing salt purification methods will also be essential to eliminate even trace impurities.
A step closer to clean energy
This breakthrough demonstrates that purified molten salts and 316L stainless steel offer a practical, economical solution for building durable molten salt reactors. By addressing one of the biggest technical hurdles, this research brings us closer to realizing the full potential of thorium MSRs as an affordable, efficient, and scalable source of clean energy.
Read the full study: https://www.sciencedirect.com/science/article/pii/S0022311525007913