Vol:.(1234567890) Tungsten (2020) 2:34–71 https://doi.org/10.1007/s42864-020-00042-w 1 3 REVIEW PAPER A review of surface damage/microstructures and their efects on hydrogen/helium retention in tungsten Yong‑Gang Li 1,2  · Qi‑Rong Zheng 1,2  · Liu‑Ming Wei 1,2  · Chuan‑Guo Zhang 1,2  · Zhi Zeng 1,2 Received: 26 January 2020 / Revised: 20 February 2020 / Accepted: 2 March 2020 / Published online: 17 June 2020 © The Nonferrous Metals Society of China 2020 Abstract The change in surface damage/microstructures and its efects on the hydrogen (H) isotope/helium (He) dynamic behavior are the key factors for investigating issues of tungsten (W)-based plasma-facing materials (PFMs) in fusion such as surface erosion, H/He retention and tritium (T) inventory. Complex surface damage/microstructures are introduced in W by high- temperature plasma irradiation and new material design, typically including pre-damage and multi-ion co-deposition induced structures, solute elements and related composites, native defects like dislocations and interfaces, and nanostructures. Sys- tematic experimental and theoretical researches were performed on H isotope/He retention in complex W-based materials in the past decades. In this review, we aim to provide an overview of typical surface damage/microstructures and their efects on H/He retention in W, both in the experiment and multiscale modeling. The distribution/state, dynamics evolution, and interaction with defects/microstructures of H/He are generally summarized at diferent scales. Finally, the current difculties, challenges and future directions are also discussed about H/He retention in complex W-based PFMs. Keywords Surface damage/microstructures · Hydrogen/helium retention · Tungsten · Plasma-facing materials 1 Introduction The successful implementation of the International Ther- monuclear Experimental Reactor (ITER) project [1] and the latest progress on next-generation devices such as the China Fusion Engineering Test Reactor (CFETR) [2] and a demonstration fusion reactor (DEMO) [3] promote the development of nuclear fusion energy to a new historical period. In magnetic confnement fusion devices, plasma- facing materials (PFMs) endure the strong impact of high- temperature plasma, which will produce a large number of radiation defects and further lead to serious macroscopic damage in materials, making material problems become one of the most challenging issues for nuclear fusion energy [4]. Among them, the most critical one is the selection and design of PFMs as well as their radiation degradation and long-term service performance [5]. PFMs are the armor materials that directly face high-tem- perature plasma to protect the frst-wall (FW) and divertor in Tokamak fusion devices, which straightly determine the stability of plasma and the safety and lifetime of the struc- tural components [6]. In the ITER device [1], the PFMs must be able to simultaneously withstand three conditions: (1) the efects of surface sputtering, blistering and erosion under the interaction of escaping particles from plasma, without exces- sive contamination of the core plasma; (2) the relatively high surface steady-state heat load of ~ 10 MW·m −2 and transient heat load of ~ 20 MW·m −2 by rapid deposition of energy during plasma rupture events; (3) 14.1 MeV neutron radiation damage, hydrogen (H) isotope (deuterium (D) and tritium (T))/helium (He) embrittlement and gas swelling. Their comprehensive performances should also be compat- ible with the operating lifetime, reliability and maintenance of the reactor [6]. Finally, they should be environmentally friendly, with enough long half-life radioactive products and low T retention (with quantity design requirements < 300 g [7], and limit quantity of ~ 700 g [8]). Thus, the performance demands on plasma-facing components (PFCs) of future fusion power plants are beyond the capability of current materials [9]. Tungsten www.springer.com/42864 * Yong-Gang Li ygli@theory.issp.ac.cn 1 Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences, Hefei 230031, China 2 Science Island Branch of Graduate School, University of Science and Technology of China, Hefei 230026, China