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Title: Multi-scale modelling to relate beryllium surface temperature, deuterium concentration and erosion in fusion reactor environment

Abstract

Beryllium (Be) has been chosen as the plasma-facing material for the main wall of ITER, the next generation fusion reactor. Identifying the key parameters that determine Be erosion under reactor relevant conditions is vital to predict the ITER plasma-facing component lifetime and viability. To date, a certain prediction of Be erosion, focusing on the effect of two such parameters, surface temperature and D surface content, has not been achieved. In this paper, we develop the first multi-scale KMC-MD modeling approach for Be to provide a more accurate database for its erosion, as well as investigating parameters that affect erosion. First, we calculate the complex relationship between surface temperature and D concentration precisely by simulating the time evolution of the system using an object kinetic Monte Carlo (OKMC) technique. These simulations provide a D surface concentration profile for any surface temperature and incoming D energy. We then describe how this profile can be implemented as a starting configuration in molecular dynamics (MD) simulations. We finally use MD simulations to investigate the effect of temperature (300–800 K) and impact energy (10–200 eV) on the erosion of Be due to D plasma irradiations. The results reveal a strong dependency of the D surfacemore » content on temperature. Increasing the surface temperature leads to a lower D concentration at the surface, because of the tendency of D atoms to avoid being accommodated in a vacancy, and de-trapping from impurity sites diffuse fast toward bulk. At the next step, total and molecular Be erosion yields due to D irradiations are analyzed using MD simulations. The results show a strong dependency of erosion yields on surface temperature and incoming ion energy. The total Be erosion yield increases with temperature for impact energies up to 100 eV. However, increasing temperature and impact energy results in a lower fraction of Be atoms being sputtered as BeD molecules due to the lower D surface concentrations at higher temperatures. Finally, these findings correlate well with different experiments performed at JET and PISCES-B devices.« less

Authors:
 [1];  [2];  [3];  [1]
  1. Univ. of Helsinki (Finland)
  2. Technical Univ. of Madrid (Spain). Inst. of Nuclear Fusion
  3. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Publication Date:
Research Org.:
Univ. of Helsinki (Finland); Technical Univ. of Madrid (Spain); Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org.:
USDOE; European Commission (EC)
OSTI Identifier:
1376422
Grant/Contract Number:  
AC05-00OR22725; 633053
Resource Type:
Accepted Manuscript
Journal Name:
Journal of Physics. D, Applied Physics
Additional Journal Information:
Journal Volume: 50; Journal Issue: 20; Journal ID: ISSN 0022-3727
Publisher:
IOP Publishing
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; 36 MATERIALS SCIENCE

Citation Formats

Safi, E., Valles, G., Lasa, A., and Nordlund, K.. Multi-scale modelling to relate beryllium surface temperature, deuterium concentration and erosion in fusion reactor environment. United States: N. p., 2017. Web. https://doi.org/10.1088/1361-6463/aa6967.
Safi, E., Valles, G., Lasa, A., & Nordlund, K.. Multi-scale modelling to relate beryllium surface temperature, deuterium concentration and erosion in fusion reactor environment. United States. https://doi.org/10.1088/1361-6463/aa6967
Safi, E., Valles, G., Lasa, A., and Nordlund, K.. Mon . "Multi-scale modelling to relate beryllium surface temperature, deuterium concentration and erosion in fusion reactor environment". United States. https://doi.org/10.1088/1361-6463/aa6967. https://www.osti.gov/servlets/purl/1376422.
@article{osti_1376422,
title = {Multi-scale modelling to relate beryllium surface temperature, deuterium concentration and erosion in fusion reactor environment},
author = {Safi, E. and Valles, G. and Lasa, A. and Nordlund, K.},
abstractNote = {Beryllium (Be) has been chosen as the plasma-facing material for the main wall of ITER, the next generation fusion reactor. Identifying the key parameters that determine Be erosion under reactor relevant conditions is vital to predict the ITER plasma-facing component lifetime and viability. To date, a certain prediction of Be erosion, focusing on the effect of two such parameters, surface temperature and D surface content, has not been achieved. In this paper, we develop the first multi-scale KMC-MD modeling approach for Be to provide a more accurate database for its erosion, as well as investigating parameters that affect erosion. First, we calculate the complex relationship between surface temperature and D concentration precisely by simulating the time evolution of the system using an object kinetic Monte Carlo (OKMC) technique. These simulations provide a D surface concentration profile for any surface temperature and incoming D energy. We then describe how this profile can be implemented as a starting configuration in molecular dynamics (MD) simulations. We finally use MD simulations to investigate the effect of temperature (300–800 K) and impact energy (10–200 eV) on the erosion of Be due to D plasma irradiations. The results reveal a strong dependency of the D surface content on temperature. Increasing the surface temperature leads to a lower D concentration at the surface, because of the tendency of D atoms to avoid being accommodated in a vacancy, and de-trapping from impurity sites diffuse fast toward bulk. At the next step, total and molecular Be erosion yields due to D irradiations are analyzed using MD simulations. The results show a strong dependency of erosion yields on surface temperature and incoming ion energy. The total Be erosion yield increases with temperature for impact energies up to 100 eV. However, increasing temperature and impact energy results in a lower fraction of Be atoms being sputtered as BeD molecules due to the lower D surface concentrations at higher temperatures. Finally, these findings correlate well with different experiments performed at JET and PISCES-B devices.},
doi = {10.1088/1361-6463/aa6967},
journal = {Journal of Physics. D, Applied Physics},
number = 20,
volume = 50,
place = {United States},
year = {2017},
month = {3}
}

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    Molecular dynamics simulation of beryllium oxide irradiated by deuterium ions: sputtering and reflection
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    ERO modeling and sensitivity analysis of locally enhanced beryllium erosion by magnetically connected antennas
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