A coupled rate theory-Monte Carlo model of helium bubble evolution in plasma-facing micro-engineered tungsten

Gao, Edward; Ghoniem, Nasr M.

doi:10.1016/j.jnucmat.2018.04.051

Cited by 16 publications

(4 citation statements)

References 37 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…[34] Based on these DFT results as input, many efforts have been made to determine the evolution of He and defects in W via using molecular dynamics (MD) and kinetic Monte Carlo (KMC) methods. [35][36][37][38][39] However, previous large-scale simulations are mainly focused on the behaviors of He in W (e.g., He retention and He bubble formation), and thus the influence of He on the evolution of irradiation-induced defects is not still clear.…”

Section: Introductionmentioning

confidence: 99%

Influence of helium on the evolution of irradiation-induced defects in tungsten: An object kinetic Monte Carlo simulation*

Hou¹,

Li²,

Li³

et al. 2021

Chinese Phys. B

View full text Add to dashboard Cite

Understanding the evolution of irradiation-induced defects is of critical importance for the performance estimation of nuclear materials under irradiation. Hereby, we systematically investigate the influence of He on the evolution of Frenkel pairs and collision cascades in tungsten (W) via using the object kinetic Monte Carlo (OKMC) method. Our findings suggest that the presence of He has significant effect on the evolution of irradiation-induced defects. On the one hand, the presence of He can facilitate the recombination of vacancies and self-interstitial atoms (SIAs) in W. This can be attributed to the formation of immobile He-SIA complexes, which increases the annihilation probability of vacancies and SIAs. On the other hand, due to the high stability and low mobility of He-vacancy complexes, the growth of large vacancy clusters in W is kinetically suppressed by He addition. Specially, in comparison with the injection of collision cascades and He in sequential way at 1223 K, the average sizes of surviving vacancy clusters in W via simultaneous way are smaller, which is in good agreement with previous experimental observations. These results advocate that the impurity with low concentration has significant effect on the evolution of irradiation-induced defects in materials, and contributes to our understanding of W performance under irradiation.

show abstract

Section: Introductionmentioning

confidence: 99%

Influence of helium on the evolution of irradiation-induced defects in tungsten: An object kinetic Monte Carlo simulation*

Hou¹,

Li²,

Li³

et al. 2021

Chinese Phys. B

View full text Add to dashboard Cite

show abstract

“…However, it also presents certain drawbacks, particularly regarding the retention of light species, mainly hydrogen and helium [9,10]. This leads to a series of detrimental effects such as surface blistering, exfoliation and cracking [5,11]. In order to avoid or at least to minimise these effects, one of the proposed strategies consists in scaling down the grain size from micrometre dimensions to tens to hundreds of nanometres (nanostructuration), as it has been reported that nanostructured materials present a higher resistance against radiation than their coarse-grained counterparts [12][13][14][15][16].…”

Section: Introductionmentioning

confidence: 99%

Direct observation of hydrogen permeation through grain boundaries in tungsten

et al. 2022

View full text Add to dashboard Cite

In this paper, we report on an enhanced hydrogen permeation effect along grain boundaries in tungsten. Sputtered nanocolumnar tungsten layers (column lateral dimensions 100–150 nm and layer thickness 2 μm) were analysed by hydrogen permeation measurements in the temperature range 520–705 K. The experiments constitute a direct observation of this effect, previously postulated by means of a combination of indirect experiments and simulations and considered controversial due to the lack of direct measurements. DFT results support this observation since (i) the hydrogen binding energy to the grain boundary is 1.05 eV and (ii) the migration energies along the grain boundary and along the bulk are 0.12 eV and 0.20 eV, respectively. OKMC simulations, parametrized by DFT data, were used as a supporting tool to attain a better understanding of the involved phenomena. The OKMC results are also compatible with the observations. Indeed, they show that the fraction of hydrogen flux along grain boundaries in the steady-state permeation regime increases when decreasing the ratio of lateral dimensions to length of the nanocolumns, rapidly approaching unity when this ratio is < 2. Therefore, grain boundaries act as preferential migration pathways for H atoms at the studied temperature range in the studied samples. This behaviour has interesting implications to reduce the retention of hydrogen in several applications, in particular, fusion materials exposed to plasma discharges.

show abstract

“…Owing to its high melting point, high thermal conductivity, low activation, low physical sputtering yields, and small fuel retention, tungsten is the chosen plasma-facing material for ITER, the world's largest fusion experiment [2]. However, tungsten undergoes a variety of microstructural changes under fusion plasma loads, such as hydrogen-induced blistering [3][4][5][6][7], helium-induced fuzz [8][9][10][11][12][13][14], recrystallization [15,16], and thermal fatigue [17][18][19][20][21]. Moreover, a strong interplay between these nano-and microscale mechanisms is expected because ITER will be operated in a staged approach [2].…”

Section: Introductionmentioning

confidence: 99%

Influence of porosity and blistering on the thermal fatigue behavior of tungsten

Li¹,

Vermeij²,

Hoefnagels³

et al. 2022

Nucl. Fusion

View full text Add to dashboard Cite

Tungsten is the leading plasma-facing material (PFM) for nuclear fusion applications. It faces severe operating conditions, including intense hydrogen plasma exposure and high-cycle transient heat loading, which create various defects in tungsten. Additionally, defects have often already been introduced during manufacturing. Little is understood regarding the synergistic effect of such defects on the lifetime of tungsten so far. Here, we investigate the influence of porosity and blistering on the thermal fatigue behavior of tungsten. The pores resulted from powder metallurgy whereas the blistering was induced by hydrogen plasma exposure. Both conditions were subjected to transient heat loading by a high-power pulsed laser. The exposure was performed in the linear plasma generator Magnum-PSI, which closely mimics the expected particle and heat flux in the world’s largest fusion experiment, ITER. Both porosity and blistering degraded the fatigue resistance of tungsten. Pores tended to aggregate at high-angle grain boundaries (HAGBs) and assisted crack initiation therein, as revealed by focused ion beam (FIB) cross-sectioning and electron backscatter diffraction (EBSD) analysis. The blisters were characteristic of subsurface cavities, which were located at a depth close to the surface roughness induced by transient heat loading. The stress concentration at the tip of the cavities is considered to promote crack initiation. The results highlight the necessity of a ‘life cycle assessment’ of the tungsten PFM for nuclear fusion reactors.

show abstract

A coupled rate theory-Monte Carlo model of helium bubble evolution in plasma-facing micro-engineered tungsten

Cited by 16 publications

References 37 publications

Influence of helium on the evolution of irradiation-induced defects in tungsten: An object kinetic Monte Carlo simulation*

Influence of helium on the evolution of irradiation-induced defects in tungsten: An object kinetic Monte Carlo simulation*

Direct observation of hydrogen permeation through grain boundaries in tungsten

Influence of porosity and blistering on the thermal fatigue behavior of tungsten

Contact Info

Product

Resources

About