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Title: Liquid Metals as Plasma-facing Materials for Fusion Energy Systems: From Atoms to Tokamaks

Abstract

The objective of our studies was to advance our fundamental understanding of liquid metals as plasma-facing materials for fusion energy systems, with a broad scope: from atoms to tokamaks. The flow of liquid metals offers solutions to significant problems of the plasma-facing materials for fusion energy systems. Candidate metals include lithium, tin, gallium, and their eutectic combinations. However, such liquid metal solutions can only be designed efficiently if a range of scientific and engineering issues are resolved that require advances in fundamental fluid dynamics, materials science and surface science. In our research we investigated a range of significant and timely problems relevant to current and proposed engineering designs for fusion reactors, including high-heat flux configurations that are being considered by leading fusion energy groups world-wide. Using experimental and theoretical tools spanning atomistic to continuum descriptions of liquid metals, and bridging surface chemistry, wetting/dewetting and flow, our research has advanced the science and engineering of fusion energy materials and systems. Specifically, we developed a combined experimental and theoretical program to investigate flows of liquid metals in fusion-relevant geometries, including equilibrium and stability of thin-film flows, e.g. wetting and dewetting, effects of electromagnetic and thermocapillary fields on liquid metal thin-film flows, andmore » how chemical interactions and the properties of the surface are influenced by impurities and in turn affect the surface wetting characteristics, the surface tension, and its gradients. Because high-heat flux configurations produce evaporation and sputtering, which forces rearrangement of the liquid, and any dewetting exposes the substrate to damage from the plasma, our studies addressed such evaporatively driven liquid flows and measured and simulated properties of the different bulk phases and material interfaces. The range of our studies included (i) quantum mechanical calculations that allow inclusion of many thousands of atoms for the characterization of the interface of liquid metals exposed to continuous bombardment by deuterium and tritium as expected in fusion, (ii) molecular dynamics studies of the phase behavior of liquid metals, which (a) utilize thermodynamic properties computed using our quantum mechanical calculations and (b) establish material and wetting properties of the liquid metals, including relevant eutectics, (iii) experimental investigations of the surface science of liquid metals, interacting both with the solid substrate as well as gaseous species, and (iv) fluid dynamical studies that incorporate the material and surface science results of (ii) and (iii) in order to characterize flow in capillary porous materials and the thin-film flow along curved boundaries, both of which are potentially major components of plasma-facing materials. The outcome of these integrated studies was new understanding that enables developing design rules useful for future developments of the plasma-facing components critical to the success of fusion energy systems.« less

Authors:
 [1];  [1];  [1];  [1];  [1];  [1]
  1. Princeton Univ., NJ (United States)
Publication Date:
Research Org.:
Princeton Univ., NJ (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Fusion Energy Sciences (FES) (SC-24)
OSTI Identifier:
1389595
Report Number(s):
DOE-PU-0008598-3
DOE Contract Number:
SC0008598
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 70 PLASMA PHYSICS AND FUSION TECHNOLOGY; 37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; 42 ENGINEERING

Citation Formats

Stone, Howard A., Koel, Bruce E., Bernasek, Steven L., Carter, Emily A., Debenedetti, Pablo G., and Panagiotopoulos, Athanassios Z. Liquid Metals as Plasma-facing Materials for Fusion Energy Systems: From Atoms to Tokamaks. United States: N. p., 2017. Web. doi:10.2172/1389595.
Stone, Howard A., Koel, Bruce E., Bernasek, Steven L., Carter, Emily A., Debenedetti, Pablo G., & Panagiotopoulos, Athanassios Z. Liquid Metals as Plasma-facing Materials for Fusion Energy Systems: From Atoms to Tokamaks. United States. doi:10.2172/1389595.
Stone, Howard A., Koel, Bruce E., Bernasek, Steven L., Carter, Emily A., Debenedetti, Pablo G., and Panagiotopoulos, Athanassios Z. Fri . "Liquid Metals as Plasma-facing Materials for Fusion Energy Systems: From Atoms to Tokamaks". United States. doi:10.2172/1389595. https://www.osti.gov/servlets/purl/1389595.
@article{osti_1389595,
title = {Liquid Metals as Plasma-facing Materials for Fusion Energy Systems: From Atoms to Tokamaks},
author = {Stone, Howard A. and Koel, Bruce E. and Bernasek, Steven L. and Carter, Emily A. and Debenedetti, Pablo G. and Panagiotopoulos, Athanassios Z.},
abstractNote = {The objective of our studies was to advance our fundamental understanding of liquid metals as plasma-facing materials for fusion energy systems, with a broad scope: from atoms to tokamaks. The flow of liquid metals offers solutions to significant problems of the plasma-facing materials for fusion energy systems. Candidate metals include lithium, tin, gallium, and their eutectic combinations. However, such liquid metal solutions can only be designed efficiently if a range of scientific and engineering issues are resolved that require advances in fundamental fluid dynamics, materials science and surface science. In our research we investigated a range of significant and timely problems relevant to current and proposed engineering designs for fusion reactors, including high-heat flux configurations that are being considered by leading fusion energy groups world-wide. Using experimental and theoretical tools spanning atomistic to continuum descriptions of liquid metals, and bridging surface chemistry, wetting/dewetting and flow, our research has advanced the science and engineering of fusion energy materials and systems. Specifically, we developed a combined experimental and theoretical program to investigate flows of liquid metals in fusion-relevant geometries, including equilibrium and stability of thin-film flows, e.g. wetting and dewetting, effects of electromagnetic and thermocapillary fields on liquid metal thin-film flows, and how chemical interactions and the properties of the surface are influenced by impurities and in turn affect the surface wetting characteristics, the surface tension, and its gradients. Because high-heat flux configurations produce evaporation and sputtering, which forces rearrangement of the liquid, and any dewetting exposes the substrate to damage from the plasma, our studies addressed such evaporatively driven liquid flows and measured and simulated properties of the different bulk phases and material interfaces. The range of our studies included (i) quantum mechanical calculations that allow inclusion of many thousands of atoms for the characterization of the interface of liquid metals exposed to continuous bombardment by deuterium and tritium as expected in fusion, (ii) molecular dynamics studies of the phase behavior of liquid metals, which (a) utilize thermodynamic properties computed using our quantum mechanical calculations and (b) establish material and wetting properties of the liquid metals, including relevant eutectics, (iii) experimental investigations of the surface science of liquid metals, interacting both with the solid substrate as well as gaseous species, and (iv) fluid dynamical studies that incorporate the material and surface science results of (ii) and (iii) in order to characterize flow in capillary porous materials and the thin-film flow along curved boundaries, both of which are potentially major components of plasma-facing materials. The outcome of these integrated studies was new understanding that enables developing design rules useful for future developments of the plasma-facing components critical to the success of fusion energy systems.},
doi = {10.2172/1389595},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Fri Jun 23 00:00:00 EDT 2017},
month = {Fri Jun 23 00:00:00 EDT 2017}
}

Technical Report:

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  • The Unites States-Japan Workshop P-165 brought together approximately 60 scientists and engineers to discuss critical topics of plasma facing materials and components for the next-step fusion device. In addition to the United States and Japanese participants, there were several guest attendees from Europe. The international makeup of the participants greatly enhanced the success of the workshop. The author jointly chaired a workshop session entitled Impact of Neutron Effects to Plasma Facing Materials and Plasma Facing Component (PFC) Feasibilities for the International Thermonuclear Experimental Reactor (ITER),'' and presented an overview paper on neutron effects and materials selection for the next-step plasmamore » facing devices. The author presented his work on the effects of neutron irradiation on graphites and carbon-carbon (c/c) composite materials, which are strong candidate materials for PFC's in ITER. The workshop addressed many issues of current concern to the PFC/PFM community including: plasma erosion of PFM's; trapping/detrapping of hydrogen isotopes; large machine operating experience; and extent of the materials database.« less
  • The goal of the 2014 Joint Research Target (JRT) has been to conduct experiments and analysis to investigate and quantify the response of tokamak plasmas to non-axisymmetric (3D) magnetic fields. Although tokamaks are conceptually axisymmetric devices, small asymmetries often result from inaccuracies in the manufacture and assembly of the magnet coils, or from nearby magnetized objects. In addition, non-axisymmetric fields may be deliberately applied for various purposes. Even at small amplitudes of order 10 -4 of the main axisymmetric field, such “3D” fields can have profound impacts on the plasma performance. The effects are often detrimental (reduction of stabilizing plasmamore » rotation, degradation of energy confinement, localized heat flux to the divertor, or excitation of instabilities) but may in some case be beneficial (maintenance of rotation, or suppression of instabilities). In general, the magnetic response of the plasma alters the 3D field, so that the magnetic field configuration within the plasma is not simply the sum of the external 3D field and the original axisymmetric field. Typically the plasma response consists of a mixture of local screening of the external field by currents induced at resonant surfaces in the plasma, and amplification of the external field by stable kink modes. Thus, validated magnetohydrodynamic (MHD) models of the plasma response to 3D fields are crucial to the interpretation of existing experiments and the prediction of plasma performance in future devices. The non-axisymmetric coil sets available at each facility allow well-controlled studies of the response to external 3D fields. The work performed in support of the 2014 Joint Research Target has included joint modeling and analysis of existing experimental data, and collaboration on new experiments designed to address the goals of the JRT. A major focus of the work was validation of numerical models through quantitative comparison to experimental data, in order to gain confidence in their ability to predict the performance of ITER and other burning plasmas. An important element of this effort was also to verify experimentally the limits of validity of the models. The rest of this overview will summarize the key results of the work.« less