Multi-scale modeling of hydrogen isotope transport in porous graphite

Deuterium and tritium will be the fuel used in a fusion reactor in equal mixtures.It is important to study the recycling and mixing of these isotopes of hydrogen in graphite from several points of view: (i) impact on the ratio of deuterium to tritium in a reactor, (ii) continued use of graphite as a first wall and divertor material, (iii) reaction with carbon atoms and the transport of hydrocarbons will provide insight into chemical erosion. Dynamic Monte-Carlo techniques are used to study the reactivediffusive transport of hydrogen isotopes and interstitial carbon atoms in a 3-D porous graphite structure irradiated with hydrogen and deuterium and is compared with published experimental results for hydrogen re-emission and isotope exchange.

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“…Later, this concept was extended our simulations to the macroscales (1 cm, up to a few s), thereby having a truly multi-scale capability. [20].…”

Section: Modelmentioning

confidence: 99%

Dynamic Monte-Carlo modeling of hydrogen isotope reactive–diffusive transport in porous graphite

Schneider

Rai

Mutzke

et al. 2007

Journal of Nuclear Materials

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“…In the present work we simulate the physics at meso-scales where a 100 nm × 100 nm × 300 nm sized granule of graphite is taken and Kinetic Monte-Carlo (KMC) is used. In KMC scheme all the thermally activated processes taking place in the system are parametrized in terms of the jump attempt frequency ω j o , the migration energy E j m , and the jump distance L j [4][5][6][7]. The jump distance L j corresponds to the distance jumped by an atom or molecule in a specified direction after overcoming the j th energy barrier with migration energy E j m .…”

Section: Description Of the 3d Kmc Modelmentioning

confidence: 99%

“…The model is a hierarchical multi-scale model, wherein simulations at the lower scales or experimental results wherever available are used as inputs to the simulations at higher scales. In other words, the idea is to use the insights gained from the microscopic (up to nanometers) models (MD or ab-initio methods) for modeling the transport at the meso-scale (up to micrometers) and further at the macro-scale (up to cms) in order to understand the physical processes contributing to macroscopic transport [4][5][6][7]. Fig.…”

Section: Introductionmentioning

confidence: 99%

“…For samples having less internal porosity mixing is very low. Therefore the internal structure of graphite, which affects the diffusion coefficient [4][5][6][7] and consequently molecule formation and atomic re-emission [8,9], plays the most crucial role for the H,D mixing. A new mechanism based on the KMC and SDTrimSP simulation is proposed to explain the experimental data.…”

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Modeling of hydrogen isotope exchange from porous graphite

Rai

Schneider

Mutzke

et al. 2012

Nuclear Instruments and Methods in Physics Research Section B:

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A 3D Kinetic Monte Carlo (KMC) model has been used to study the hydrogen isotope exchange from porous graphite at a single granule length scale (micrometers).The present KMC model is part of a previously reported multi-scale model developed by the authors [1]. SDTrimSP [2,3] simulations have been carried out and the results have been used to get some of the input parameters for the KMC where the diffusive-reactive aspect of H and D are studied. These SDTrimSP calculations show that the incident energetic ion beams lead to the development of inter-connected pores in the graphite sample. In the presence of these connected pores hydrogen molecule formation is not a local process. It takes place throughout the implantation zone and not only at the end of the ion range. For samples having less internal porosity mixing is very low. Therefore the internal structure of graphite, which affects the diffusion coefficient [4][5][6][7] and consequently molecule formation and atomic re-emission [8,9], plays the most crucial role for the H,D mixing. A new mechanism based on the KMC and SDTrimSP simulation is proposed to explain the experimental data.

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“…The transport simulation has been carried out by extending the previously developed multi-scale model for hydrogen isotope diffusion and reactive-diffusive processes in porous graphite [14,15]. It is seen from this simulation that atomic hydrogen diffusion through the porous co-deposits and subsequent trapping at trap sites can be a major contribution to the high density of hydrogen in these soft films.…”

Section: Introductionmentioning

confidence: 99%

Dynamic Monte-Carlo modeling of hydrogen isotope diffusion in co-deposited layers

Rai

Maya

Schneider

et al. 2007

Journal of Nuclear Materials

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Reactive-diffusive transport of hydrogen in the porous, 3-dimensional structure of codeposited films is simulated using a kinetic Monte Carlo (KMC) method. The simulations are carried out on samples generated from the film growth Monte Carlo (FGMC) code which simulates the film-growth process in remote regions of fusion devices. It is seen that the steric repulsion between the incoming hydrocarbon and the surface atoms is an important parameter which affects the structure and trap concentrations of these soft films. Initial results indicate that diffusion of hydrogen through pores in the co-deposited films could be a major contributor to the high density of hydrogen in co-deposits seen at remote locations of fusion devices.

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Multi-scale modeling of hydrogen isotope transport in porous graphite

Cited by 15 publications

References 22 publications

Dynamic Monte-Carlo modeling of hydrogen isotope reactive–diffusive transport in porous graphite

Dynamic Monte-Carlo modeling of hydrogen isotope reactive–diffusive transport in porous graphite

Modeling of hydrogen isotope exchange from porous graphite

Dynamic Monte-Carlo modeling of hydrogen isotope diffusion in co-deposited layers

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