Title: Thermal gradient effect on helium and self-interstitial transport in tungsten

Abstract

First-wall materials in a fusion reactor are expected to withstand harsh conditions, with high heat and particle fluxes that modify the materials microstructure. These fluxes will create strong gradients of temperature and concentration of diverse species. Besides the He ash and the hydrogenic species, neutron particles generated in the fusion reaction will collide with the material creating intrinsic defects, such as vacancies, self-interstitials atoms (SIAs), and clusters of such point defects. These defects and the He atoms will then migrate in the presence of the aforementioned gradients. In this study, we use nonequilibrium molecular dynamics to analyze the transport of He and SIAs in the presence of a thermal gradient in tungsten. We observe that, in all cases, the defects and impurity atoms tend to migrate toward the hot regions of the tungsten sample. The resulting species concentration profiles are exponential distributions, rising toward the hot regions of the sample, in agreement with irreversible thermodynamics analysis. For both He atoms and SIAs, we find that the resulting species flux is directed opposite to the heat flux, indicating that species transport is governed by a Soret effect (thermal-gradient-driven diffusion) characterized by a negative heat of transport that drives species diffusion uphillmore » (from the cooler to the hot regions of the sample). We demonstrate that the steady-state species profiles obtained accounting for the Soret effect vary significantly from those where temperature-gradient-driven transport is not considered and discuss the implications of such a Soret effect on the response to plasma exposure of plasma-facing tungsten.« less

Authors:

Martínez, Enrique  ^[1];

• Search DOE PAGES for author "Martínez, Enrique"
• Search DOE PAGES for ORCID "0000-0002-2690-2622"

Mathew, Nithin ^[2]; Perez, Danny  ^[2];

• Search DOE PAGES for author "Perez, Danny"
• Search DOE PAGES for ORCID "0000-0003-3028-5249"

Blondel, Sophie ^[3]; Dasgupta, Dwaipayan  ^[3];

• Search DOE PAGES for author "Dasgupta, Dwaipayan"
• Search DOE PAGES for ORCID "0000-0001-9405-922X"

Wirth, Brian D.  ^[4];

• Search DOE PAGES for author "Wirth, Brian D."
• Search DOE PAGES for ORCID "0000-0002-0395-0285"

Maroudas, Dimitrios  ^[5]

• Search DOE PAGES for author "Maroudas, Dimitrios"
• Search DOE PAGES for ORCID "0000-0001-9297-8839"

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+ Show Author Affiliations

1. Clemson Univ., SC (United States)
2. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
3. Univ. of Tennessee, Knoxville, TN (United States)
4. Univ. of Tennessee, Knoxville, TN (United States); Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
5. Univ. of Massachusetts, Amherst, MA (United States)

Publication Date:

Fri Dec 03 00:00:00 EST 2021

Research Org.:

Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)

Sponsoring Org.:

USDOE Office of Science (SC), Fusion Energy Sciences (FES); USDOE Office of Science (SC), Advanced Scientific Computing Research (ASCR)

OSTI Identifier:

1868296

Alternate Identifier(s):

OSTI ID: 1833870

Report Number(s):

LA-UR-21-28937
Journal ID: ISSN 0021-8979; TRN: US2306580

Grant/Contract Number:  

89233218CNA000001; SC0008875; SC0018421

Resource Type:

Accepted Manuscript

Journal Name:

Journal of Applied Physics

Additional Journal Information:

Journal Volume: 130; Journal Issue: 21; Journal ID: ISSN 0021-8979

Publisher:

American Institute of Physics (AIP)

Country of Publication:

United States

Language:

English

Subject:

36 MATERIALS SCIENCE; Material Science; Fusion; Helium; Thermal gradients; Concentration gradients; Crystallographic defects; Molecular dynamics; Thermodynamic states and processes; Thermal conductivity; Transition metals; Irreversible thermodynamics; Fusion reactors; Thermophoresis; Computer simulation; Nuclear fusion