Changes in the fine structure of grain boundaries, induced by the absorption of helium, and helium embrittlement

Gerasimenko, V. I.; Mikhailovskii, I. M.; Neklyudov, I. M.; Parkhomenko, A. A.; Velikodnaya, O. A.

doi:10.1134/1.1259076

Cited by 9 publications

(9 citation statements)

References 3 publications

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“…As expected, the ν c He estimates are higher in the present study, leading to correspondingly higher G c He and t c He values. Note that in both studies, the ν c He , appear to be in reasonable agreement with experimental findings -particularly for W. Gerasimenko et al [21] found that GBs in helium-irradiated W came apart at He concentrations of the order of 10 14 -10 15 cm −2 .…”

Section: Compares the Critical Boundary ν Csupporting

confidence: 85%

Neutron-induced dpa, transmutations, gas production, and helium embrittlement of fusion materials

Gilbert¹,

Dudarev²,

Nguyen-Manh³

et al. 2013

Journal of Nuclear Materials

131

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In a fusion reactor materials will be subjected to significant fluxes of high-energy neutrons. As well as causing radiation damage, the neutrons also initiate nuclear reactions leading to changes in the chemical composition of materials (transmutation). Many of these reactions produce gases, particularly helium, which cause additional swelling and embrittlement of materials. This paper investigates, using a combination of neutron-transport and inventory calculations, the variation in displacements per atom (dpa) and helium production levels as a function of position within the high flux regions of a recent conceptual model for the 'next-step' fusion device DEMO. Subsequently, the gas production rates are used to provide revised estimates, based on new density-functional-theory results, for the critical component lifetimes associated with the helium-induced grain-boundary embrittlement of materials. The revised estimates give more optimistic projections for the lifetimes of materials in a fusion power plant compared to a previous study, while at the same time indicating that helium embrittlement remains one of the most significant factors controlling the structural integrity of fusion power plant components. * Corresponding author email: mark.gilbert@ccfe.ac.uk 1 lethargy interval is a commonly used measure for spectra of this type, and is equal to the natural logarithm of the ratio of a given energy-interval's upper bound to its lower bound.

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Section: Compares the Critical Boundary ν Csupporting

confidence: 85%

Neutron-induced dpa, transmutations, gas production, and helium embrittlement of fusion materials

Gilbert¹,

Dudarev²,

Nguyen-Manh³

et al. 2013

Journal of Nuclear Materials

131

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“…Despite its apparent simplicity, our critical boundary densities appear to be in reasonable agreement with experiment. For example, in experiments performed by Gerasimenko et al [27] bicrystalline W was bombarded with relatively low-energy helium ions, resulting in the accumulation of helium at grain boundaries and sudden increase in grain-boundary width observed at certain critical ion fluxes in the range 10 14 -10 15 ions cm −2 , which is exactly the range into which our estimate for grain-boundary failure in W (and in other materials) falls. In fact, considering figure 1 in [27], we note that our estimate is slightly higher, which can be explained by removing the assumption that the He atoms form a uniform layer across the entire interfacial area of a grain-in reality, the He will preferentially segregate at pre-existing sites at the interface leading to enhanced destabilization and lower critical boundary densities.…”

Section: Modelling Of He Accumulation At Grain Boundariessupporting

confidence: 61%

An integrated model for materials in a fusion power plant: transmutation, gas production, and helium embrittlement under neutron irradiation

et al. 2012

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The high-energy, high-intensity neutron fluxes produced by the fusion plasma will have a significant life-limiting impact on reactor components in both experimental and commercial fusion devices. As well as producing defects, the neutrons bombarding the materials initiate nuclear reactions, leading to transmutation of the elemental atoms. Products of many of these reactions are gases, particularly helium, which can cause swelling and embrittlement of materials. This paper integrates several different computational techniques to produce a comprehensive picture of the response of materials to neutron irradiation, enabling the assessment of structural integrity of components in a fusion power plant. Neutron-transport calculations for a model of the next-step fusion device DEMO reveal the variation in exposure conditions in different components of the vessel, while inventory calculations quantify the associated implications for transmutation and gas production. The helium production rates are then used, in conjunction with a simple model for He-induced grain-boundary embrittlement based on electronic-structure density functional theory calculations, to estimate the timescales for susceptibility to grain-boundary failure in different fusion-relevant materials. There is wide variation in the predicted grain-boundary-failure lifetimes as a function of both microstructure and chemical composition, with some conservative predictions indicating much less than the required lifetime for components in a fusion power plant.

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“…Although the transmutation rates into He and H are seen to be small, particularly when compared to fusion candidate steels (and, comparatively, relative to the role that He and H play in plasma-facing material surface evolution), their impact on bulk material response should not be minimized. Helium gas, for example, can lead to grain-boundary embrittlement [101], especially when complemented by direct He implantation from the fusion plasma, as has been observed experimentally [107]. Obviously, this change in chemical composition must be taken into account when formulating higher-level damage models of microstructural evolution.…”

Section: Physical Insight From Transmutation Calculationsmentioning

confidence: 94%

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

Marian

Becquart

Domain³

et al. 2017

Nucl. Fusion

122

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Under the anticipated operating conditions for demonstration magnetic fusion reactors beyond ITER, structural and plasma facing materials will be exposed to unprecedented conditions of irradiation, heat flux, and temperature. While such extreme environments remain inaccessible experimentally, computational modeling and simulation can provide qualitative and quantitative insights into materials response and complement the available experimental measurements with carefully validated predictions. For plasma facing components such as the first wall and the divertor, tungsten (W) has been selected as the leading candidate material due to its superior hightemperature and irradiation properties, as well as for its low retention of implanted tritium. In this paper we provide a review of recent efforts in computational modeling of W both as a plasmafacing material exposed to He deposition as well as a bulk material subjected to fast neutron irradiation. We use a multiscale modeling approach-commonly used as the materials modeling paradigm-to define the outline of the paper and highlight recent advances using several classes of techniques and their interconnection. We highlight several of the most salient findings obtained via computational modeling and point out a number of remaining challenges and future research directions.

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Changes in the fine structure of grain boundaries, induced by the absorption of helium, and helium embrittlement

Cited by 9 publications

References 3 publications

Neutron-induced dpa, transmutations, gas production, and helium embrittlement of fusion materials

Neutron-induced dpa, transmutations, gas production, and helium embrittlement of fusion materials

An integrated model for materials in a fusion power plant: transmutation, gas production, and helium embrittlement under neutron irradiation

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

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