The influence of high grain boundary density on helium retention in tungsten

Temperature dependence of underdense nanostructure formation in tungsten under helium irradiation

“…These results are in very good agreement with the experimentally reported temperature window for fuzz growth (900-2000 K) [17][18][19]. It is noteworthy that our modeling uses a general parameterization for He irradiation in W, which was previously employed to reproduce very different irradiation conditions [31,48,49]. Moreover, in our simulations the mean diameter of HenVm clusters at a fluence of 1.5 × 10 23 m -2 is 0.36 and 0.44 nm at 700 and 900 K, respectively.…”

“…Our simulations have been performed using the open-source code MMonCa [30], parameterized with in house Density Functional Theory (DFT) calculations (see Table 3 of Ref. [31]), as well as values from literature [32,33], with the exception that pure He clusters (Hen) are assumed immobile and cannot emit He atoms. Although small clusters can migrate [34,35], the assumption is justified by cluster diffusion being slowed down with the cluster size and strongly suppressed by impurities and interstices [22,23,36].…”

“…This limit is based on theoretical calculations [42,43] as well as on experimental observations [44]. As DFT calculations are only possible for small clusters, we have approximated the DFT values to a power law for large HenVm clusters [31]:…”

Recent advances in modeling and simulation of the exposure and response of tungsten to fusion energy conditions

“…As was discussed in Section 2.1, helium is also attracted to grain boundaries [147] and prefers to occupy larger spaces. Recent OKMC simulations parameterized with DFT calculations suggest that nanocrystalline W might display a higher resistance to irradiation than single crystal tungsten because He bubbles inside the nanograins are less pressurized [148], a fact that can be inferred from recent He irradiation experiments [149].…”

Object kinetic Monte Carlo simulations of irradiated tungsten for nuclear fusion reactors

“…In the case of mixed He-SIA clusters (He n I m ), the binding energies proposed by Becquart et al [66] have been used, i.e., single He atoms bind to SIA (I) and SIA clusters (I n ) with a binding energy of 0.94 eV. Regarding binding energies for He-vacancy clusters (He n V m ), they were calculated by means of ab initio calculations [54]. The calculations were carried out using the Vienna Ab initio Simulation Package (VASP) [86][87][88].…”