Preliminary assessment of high-entropy alloys for tritium storage

Tritium is the key fuel in nuclear fusion reactors. With the development of the international thermonuclear experimental reactor (ITER) project, the annual requirement of tritium has increased up to several kilograms. The candidate materials for tritium storage have many shortcomings such as insufficient kinetic performance, disproportionation effect, poor oxidation resistance, and poor helium (He) retaining ability. Therefore, it is urgent to develop a novel material system which satisfies all the requirements of tritium storage materials. High-entropy alloys (HEAs) have a unique structure of severe lattice distortion and have attracted much attention as hydrogen storage materials due to their high storing capacity and great hydrogenation performance. The distorted lattice helps to provide more interstitial sites for accommodating H atoms and enhance the He retaining ability by slowing down the He diffusion in the HEA lattice. In this work, the current research status of tritium storage materials, including the background and the basic criterion of tritium storage materials, as well as the disadvantages of the current materials, has been reviewed. Moreover, the theoretical and experimental studies of HEAs, focusing on the hydrogenation properties and the defect evolution in the distorted lattice, have been summarized. The HEAs may have great potential as tritium storage materials due to their potential hydrogenation performance and He retaining ability. Finally, the existing challenges and future development directions are also proposed.