Design integration of liquid surface divertors

Abstract

The US Enabling Technology Program in fusion is investigating the use of free flowing liquid surfaces facing the plasma. We have been studying the issues in integrating a liquid surface divertor into a configuration based upon an advanced tokamak, specifically the ARIES-RS configuration. The simplest form of such a divertor is to extend the flow of the liquid first wall into the divertor and thereby avoid introducing additional fluid streams. In this case, one can modify the flow above the divertor to enhance thermal mixing. For divertors with flowing liquid metals (or other electrically conductive fluids) MHD (magneto-hydrodynamics) effects are a major concern and can produce forces that redirect flow and suppress turbulence. An evaluation of Flibe (a molten salt) as a working fluid was done to assess a case in which the MHD forces could be largely neglected. Initial studies indicate that, for a tokamak with high power density, an integrated Flibe first wall and divertor does not seem workable. We have continued work with molten salts and replaced Flibe with Flinabe, a mixture of lithium and sodium fluorides, that has some potential because of its lower melting temperature. Sn and Sn-Li have also been considered, and the initial evaluations on heat removal with minimal plasma contamination show promise, although the complicated 3-D MHD flows cannot yet be fully modeled. Particle pumping in these design concepts is accomplished by conventional means (ports and pumps). However, trapping of hydrogen in these flowing liquids seems plausible and novel concepts for entrapping helium are also being studied. 1 Sandia is a multi-program laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the NNSA United States Department of Energy under Contract DE-AC04-94AL85000.

Structural and dynamic properties of liquid tin from a new modified embedded-atom method force field

“…4 Liquid metals, including liquid tin and lithium-tin alloys [5][6][7] are currently being considered as alternative plasma-facing materials in tokamak fusion reactors for several reasons, such as the fact that liquid walls can self-replenish and they offer easier means of remote maintenance. 6,8 An understanding of the properties of these liquid metals is also needed in order to properly assess their potential use as plasma-facing materials. Relevant liquid metal properties include viscosities, diffusivities, hydrogen solubilities, and wetting properties.…”

Liquid metals as alternative solution for the power exhaust of future fusion devices: status and perspective

“…Liquid metals have long been suggested to partly ameliorate life-time and power-exhaust issues by allowing for a self healing, self replenishing surface with no susceptibility to neutron damage. Several studies were dedicated to this topic [3,4,5,6] as several tokamak facilities have established liquid metal related research. Typically the research focuses on liquid Li due to its low melting point and beneficial behavior on plasma performance [7,8,9,10,11].…”

Modeling of dust-particle behavior for different materials in plasmas

“…17 Lithium is considered as one of basic materials in the liquid first wall concept. 40,41 Injection of dust particles has been proposed as a tool for plasma diagnostics. In Ref.…”