The expanded compositional freedom afforded by high-entropy alloys (HEAs) represents a unique opportunity for the design of alloys for advanced nuclear applications, in particular for applications where current engineering alloys fall short. This review assesses the work done to date in the field of HEAs for nuclear applications, provides critical insight into the conclusions drawn, and highlights possibilities and challenges for future study. It is found that our understanding of the irradiation responses of HEAs remains in its infancy, and much work is needed in order for our knowledge of any single HEA system to match our understanding of conventional alloys such as austenitic steels. A number of studies have suggested that HEAs possess ‘special’ irradiation damage resistance, although some of the proposed mechanisms, such as those based on sluggish diffusion and lattice distortion, remain somewhat unconvincing (certainly in terms of being universally applicable to all HEAs). Nevertheless, there may be some mechanisms and effects that are uniquely different in HEAs when compared to more conventional alloys, such as the effect that their poor thermal conductivities have on the displacement cascade. Furthermore, the opportunity to tune the compositions of HEAs over a large range to optimise particular irradiation responses could be very powerful, even if the design process remains challenging.

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The success of fusion power requires alloys with good mechanical properties and the ability to withstand extreme thermal and irradiation conditions without prohibitive levels of activation or structural degradation. Body-centred cubic multi-principal component alloys, V–Cr–Mn and Ti–V–Cr–Mn have shown promising high-temperature stability at [Formula: see text]. For the alloys to be suitable for use in nuclear fusion reactors, they must be stable across a wide range of temperatures relevant to fusion applications. Here, we assess alloy microstructural stability in these systems following long-term heat treatments at various temperatures. Encouragingly, most of the alloys showed no significant change in microstructure across all temperatures. This contrasts with many other multi-principal component alloys, which develop complex microstructures after exposure to intermediate temperatures.

Making fusion power viable both technologically and commercially has been a challenge for decades due to the great complexity of the science and engineering challenges. In recent years, changes in both government policies and the emergence of private fusion companies have ushered a newfound push to accelerate fusion energy development. Kyoto Fusioneering (KF) is a privately funded fusion engineering start-up, founded to accelerate the development of high performance, commercially viable technologies that will be required for a fusion power plant, specifically those associated with heating and current drive systems, power generation, and the tritium fuel cycle. The company is focused on supporting the rapid expansion of the budding fusion industry. This paper provides a high-level description of some of the technical and industrial challenges it is tackling in developing a commercial fusion reactor, in particular in relation to: plasma heating with gyrotrons, tritium handling and breeding, energy conversion, and fusion materials. It provides an overview of KF's activities in finding solutions to challenges in each of these areas, including via its new testing facility now under construction, UNITY (Unique Integrated Testing Facility). KF’s core capabilities and areas of R&D focus are discussed, with reference to how they benefit the development of a new fusion industry as a whole and bring the technology closer to industrialisation, including via UNITY and through collaboration with external partners. The importance of industrialisation and subsequently commercialisation is also discussed, through KF’s assessment of the newly emerging fusion ecosystem, and where KF as a company sits within it.

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