Hydrogen diffusion and vacancies formation in tungsten: Density Functional Theory calculations and statistical models

Fernández, Nicolás; Ferro, Y.; Kato, Daiji

doi:10.1016/j.actamat.2015.04.052

Cited by 191 publications

(257 citation statements)

References 64 publications

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“…This is an extended experimental program in itself and it is not the subject of the present study. However our results can be discussed in view of the recent theoretical investigations at the ab initio level for the interaction of deuterium with natural bulk defects in tungsten such as single vacancy [22][23][24][25][26][27], grain boundary [28,29], and dislocation [29]. All these defects can accommodate several deuterium atoms in their vicinity.…”

Section: Discussionmentioning

confidence: 99%

Dynamic fuel retention in tokamak wall materials: An in situ laboratory study of deuterium release from polycrystalline tungsten at room temperature

Bisson

Markelj

Mourey.

et al. 2015

Journal of Nuclear Materials

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Section: Discussionmentioning

confidence: 99%

Dynamic fuel retention in tokamak wall materials: An in situ laboratory study of deuterium release from polycrystalline tungsten at room temperature

Bisson

Markelj

Mourey.

et al. 2015

Journal of Nuclear Materials

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“…Binding energies for H atoms to V m and H n V m clusters are summarized in Table 3.8. In the case of H trapped in a single vacancy (H n V), the results [128] are in good agreement with previously published data [122,[130][131][132][133] as observed in Figure 3.4. [128]) are compared to those obtained by Johnson et al [131], Heinola et al [132], Ohsawa et al [133], Liu et al [130] and Fernandez et al [122].…”

Section: Hydrogen In Tungstensupporting

confidence: 81%

“…Johnson et al [131], Heinola et al [132], Ohsawa et al [133], Liu et al [130] and Fernandez et al [122] The region between 0 and 150 nm (in blue) has been taken into account neither in the results nor in the discussion because it is highly influenced by surface contamination [49] is divided into small boxes, called "mesh elements". The "mesh element"…”

Section: Acknowledgementsmentioning

confidence: 99%

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

Alberdi¹

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“…Considering an 88% reduction in D retention for the HCC sample after 6 h of baking, τ for the sample is estimated as 2.83 h (10188 s). Using this value and ν = 1 × 10 13 s −1 [10], the activation energy of detrapping, E, is estimated as 1.24 eV; this activation energy is in the range of the energy required for hydrogen isotopes to detrap from a helium bubble, 1.2 -1.8 eV, and from a vacancy ≤ 1.43 eV (depending on the number of D in a vacancy) [11]. This estimation indicates that the long-term release of D from such trap sites during baking may cause the large reduction of D in the case of the HCC sample.…”

Section: Doi: 101585/pfr121302048mentioning

confidence: 99%

Effects of Mild Baking on Hydrogen Removal from the Modified Surface of the First Wall in the LHD

Nobuta

Masuzaki

Tokitani

et al. 2017

Plasma and Fusion Research

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An additional deuterium irradiation was performed for long-term samples mounted on the first wall in the large helical device (LHD) to investigate the effect of mild baking (at 368 K) on fuel hydrogen removal from the modified surface. The efficiency of baking strongly depended on the surface conditions. In the erosion dominant area, almost all the retained deuterium was removed by baking, whereas only 17% and 13% of the retained deuterium were removed from the boron and carbon deposition areas, respectively. The results suggest that the erosion dominant area in the first wall can act as a pumping wall during the main discharge, and, in contrast, the fuel hydrogen retention can continuously increase in boron and carbon deposition areas owing to the low removal efficiency of fuel hydrogen given that the deposition continues during the plasma discharge. Removal of fuel hydrogen from the plasma-facing wall in fusion devices is necessary for reducing fuel hydrogen recycling and tritium inventory. Isothermal heating of the wall, which is baking, is widely applied as one of the primary techniques for fuel hydrogen removal. This technique will be used in the ITER as well [1]. In the large helical device (LHD), baking is performed during intervals between the LHD plasma discharges, and the baking temperature is set below 368 K because the wall is close to a superconducting magnet coil [2]. This mild baking is effective for removing adsobates on the surface [2]. However, it is unclear whether this baking is effective for removing the fuel hydrogen retained on the wall during the main discharge. The plasma-facing wall receives energetic particles, leading to the erosion of the wall material, redeposition of the eroded material, and irradiation damage. These phenomena can modify the fuel hydrogen retention and desorption behavior of the wall surface [3]. A longterm sample mounted on plasma-facing surface is useful for evaluating the fuel hydrogen retention and desorption behavior of the modified surface. As fuel hydrogen in the plasma-facing material exists not only near the surface region but also in the deep region owing to hydrogen diffusion into the bulk [4], the thermal desorption spectroscopy (TDS) analysis of long-term samples obtained after the plasma operation hardly provides information on fuel hydrogen desorption from the top of the surface region. In the present study, an additional deuterium (D) irradiation was performed for the long-term sample mounted on the author's e-mail: y-nobuta@eng.hokudai.ac.jp first wall in the LHD. Then, the samples were heated at the LHD baking temperature of 368 K to investigate the effectiveness of mild baking in the removal of fuel hydrogen retained in the modified surface. These results also provide information to understand the wall-pumping capability after baking.Positions of the long-term samples mounted on the first wall in the LHD are shown in Fig. 1. At each position, several stainless steel samples, which are made of the same material as the LHD first wall, with dimensio...

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Hydrogen diffusion and vacancies formation in tungsten: Density Functional Theory calculations and statistical models

Cited by 191 publications

References 64 publications

Dynamic fuel retention in tokamak wall materials: An in situ laboratory study of deuterium release from polycrystalline tungsten at room temperature

Dynamic fuel retention in tokamak wall materials: An in situ laboratory study of deuterium release from polycrystalline tungsten at room temperature

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

Effects of Mild Baking on Hydrogen Removal from the Modified Surface of the First Wall in the LHD

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