A review of modelling and simulation of hydrogen behaviour in tungsten at different scales

Abstract

Tungsten (W) is considered to be one of the most promising plasma-facing materials (PFMs) for next-step fusion energy systems. However, as a PFM, W will be subjected to extremely high fluxes of low-energy hydrogen (H) isotopes, leading to retention of H isotopes and blistering in W, which will degrade the thermal and mechanical properties of W. Modelling and simulation are indispensable to understand the behaviour of H isotopes including dissolution, diffusion, accumulation and bubble formation, which can contribute directly to the design, preparation and application of W as a PFM under a fusion environment. This paper reviews the recent findings regarding the behaviour of H in W obtained via modelling and simulation at different scales.

Retention and release of hydrogen isotopes in tungsten plasma-facing components: the role of grain boundaries and the native oxide layer from a joint experiment-simulation integrated approach

“…We note that the experimental diffusion parameters (D H and E diff ) are the ones extracted from Frauenfelder [25], which are considered to be the best available in the literature [26]. For the detrapping energy E detrap , we extracted its value from our experimental dataset considering that the storage time dependency of deuterium retention in figure 2(a) is actually an isothermal desorption experiment and using a first-order desorption kinetic analysis [11] with the attempt frequency v detrap 0 calculated by Fernandez et al within DFT [19].…”

First-principles investigation of the orientation influenced He dissolution and diffusion behaviors on W surfaces

“…Vacancies as He trapping sites play an important role in the formation of He bubbles. 2,38 The vacancy formation ability is probed by the vacancy formation energy, which is dened as…”

“…Previous studies based on density functional theory (DFT) calculations for He behaviors in W bulk have been reported, which showed a strong attraction between He-He and a low diffusion barrier in the bulk. 2,10,11 The interactions between He projectiles and pre-existing He bubbles on W surfaces were reported using molecular dynamics (MD) simulation under low energy He ion irradiation, which indicated that He projectiles can be trapped by pre-existing bubbles. 12 Moreover, many theoretical studies at different scales found surface orientation effects on He diffusion and depth distribution on W surfaces.…”

Effect of hydrogen on grain boundary migration in tungsten

“…The behaviors of H in W as well as other structural materials have been widely investigated with various computational approaches [16][17][18][19][20][21][22][23][24][25][26][27] and experimental techniques [7,[28][29][30][31][32][33][34][35][36]. The defects in W, such as vacancies [20,37], dislocations [38] and GBs [18,19], have been shown to be responsible for the H bubble formation, which have systemically been reviewed from modeling and simulation point of view [24]. In addition, H atoms are shown to prefer to segregate into the GB region, instead of staying in the bulk, and H bubbles are most likely to form at GBs [39].…”