Molten salt nuclear reactors: A review of challenges and promises

As the demand for sustainable, low-carbon energy continues to intensify, Molten Salt Reactors (MSRs) have re-emerged as a viable Generation IV nuclear technology, characterised by inherent safety, high fuel utilisation efficiency, and improved waste-management potential. MSR development was first demonstrated in the 1960s (e.g., the Oak Ridge MSRE) and slowed down through decades. This technology recently came roaring back, driven by highly innovative approaches, the climate imperatives and advances in materials and chemistry. This review presents a synopsis of the current state of MSR research, outlines the potential advantages of the technology and provides a critical assessment of the major barriers to its implementation. It spotlights MSRs’ appealing features – like passive safety, flexible fuel cycles (including thorium utilisation), and superb thermal efficiency – as well as the key problems that need to be solved. Top among these are the management of complex fuel salt chemistry, in particular the on-line reprocessing, the challenges of materials corrosion and radiation damage in reactor components, and uncertainties in safety analysis, licensing, and economics. In this regard, major steps forward have been taken place in the past years, for instance, new corrosion-resistant alloys and a recent prototype reactor achieving criticality, supported by steady development in the associated fuel cycle techniques, which have all been very productive, but many aspects are still in the R&D stage. The review concludes that the promise of advanced MSRs will only be realised through strictly directed and coordinated multidisciplinary research efforts, prototype demonstrations, and the evolution of regulatory and market structures. These efforts are important to make MSR concepts a valid element of a future low-carbon energy mix.