Journal
JOURNAL OF NUCLEAR MATERIALS
Volume 557, Issue -, Pages -Publisher
ELSEVIER
DOI: 10.1016/j.jnucmat.2021.153306
Keywords
Helium; Tungsten; Bubbles; Diffusion
Funding
- plasma surface interactions project of the Scientific Discovery through Advanced Computing (SciDAC) program
- Fusion Energy Sciences (FES)
- Advanced Scientific Computing Research (ASCR) programs within the U.S. Department of Energy (DOE) Office of Science [DE-SC000661]
- Clemson University startup funds
- National Nuclear Security administration of the U.S. DOE [89233218CNA0000001]
- U.S. Department of Energy Office of Science User Facility located at Lawrence Berkeley National Laboratory [DE-AC02-05CH11231]
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This research describes the diffusion mechanism of high-pressure bubbles in fusion reactor environments, revealing that bubbles are most mobile under specific conditions. Bubbles experience peak diffusivity, and the calculated diffusion coefficients can improve predictions of plasma-surface interactions.
Fusion reactor environments inevitably lead to the formation of high-pressure helium bubbles whose nucleation, growth, and diffusion strongly impact the performance of plasma-facing components. This research describes a diffusion mechanism of over-pressurized bubbles via a sequence of Frenkel pair nucleation, self-interstitial migration, and Frenkel pair annihilation. Molecular dynamics was used to simulate the diffusion of small bubbles in tungsten at 2000 K with helium-per-vacancy ratios in the range of 4.5 to 7. The diffusion coefficients are calculated and their dependence on helium content, number of vacancies, and number of attached self-interstitials is characterized. It is found that bubbles are most mobile when the nucleation/annihilation rates of Frenkel pairs are nearly equal and when the bubbles nucleate and annihilate a single self-interstitial. All bubbles experience a peak diffusivity, which can be as high as 10(-11) m(2)/s decreasing with bubble size. The calculated diffusion coefficients provide valuable insight into the mobility of small, high-pressure bubbles, and can be used as input parameters in mesoscale models to improve predictions of plasma-surface interactions. (LA-UR-21-21881) Published by Elsevier B.V.
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