Reactor plasma facing component designs based on liquid metal concepts supported in porous systems

Abstract

The use of liquid metals (LMs) as plasma facing components in fusion devices was proposed as early as 1970 for a field reversed concept and inertial fusion reactors. The idea was extensively developed during the APEX Project, at the turn of the century, and it is the subject at present of the biennial International Symposium on Lithium Applications (ISLA), whose fourth meeting took place in Granada, Spain at the end of September 2015. While liquid metal flowing concepts were specially addressed in USA research projects, the idea of embedding the metal in a capillary porous system (CPS) was put forwards by Russian teams in the 1990s, thus opening the possibility of static concepts. Since then, many ideas and accompanying experimental tests in fusion devices and laboratories have been produced, involving a large fraction of countries within the international fusion community. Within the EUROFusion Roadmap, these activities are encompassed into the working programs of the plasma facing components (PFC) and divertor tokamak test (DTT) packages. In this paper, a review of the state of the art in concepts based on the CPS set-up for a fusion reactor divertor target, aimed at preventing the ejection of the liquid metal by electro-magnetic (EM) forces generated under plasma operation, is described and required R+D activities on the topic, including ongoing work at CIEMAT specifically oriented to filling the remaining gaps, are stressed.

Observation of Flat Electron Temperature Profiles in the Lithium Tokamak Experiment

“…Liquid Li PFCs would continuously flow out of a reactor for fuel extraction (and possibly heat removal, with fast flow) before being returned. Several concepts for extraction of tritium from lithium have been proposed [8,9], though large scale extraction from liquids remains an open challenge perhaps larger than trace retention in solids [9][10][11].…”

Proton impact charge exchange and excitation cross sections for liquid Sn divertor studies

“…In Tables 1 and 2, we show the singlet and triplet states on Sn included in our expansion basis and their binding energies calculated with the potentials (9). In Tables 1 and 2, we show the singlet and triplet states on Sn included in our expansion basis and their binding energies calculated with the potentials (9).…”

“…where the constants Z i for the singlet and triplet case have the values 0.83081, 6.6042, 4.1831, 0.4862 and 1.0845, 6.4134, 5.7392, 0.5666, respectively. In Tables 1 and 2, we show the singlet and triplet states on Sn included in our expansion basis and their binding energies calculated with the potentials (9). They are compared with the average energies of 5 states derived from the NIST tables and, except for the singlet 5p6d singlet and 5p8p triplet states, have an accuracy within 7%.…”

“…Thus, in the present study of the H + + Sn[4d 10 5s 2 5p 2 ] collision system, only the two 5p electrons will be considered "active." The main motivation for the study of inelastic processes in this collision system stems from the current interest of their cross sections in the liquid metal divertor research, based on Sn [4][5][6] and LiSn alloys, [7][8][9] for reduction of excessive heat loads on plasma-facing components (PFC) in fusion reactors. During the transient plasma events (edge-localized instability modes and discharge disruptions), the release of material from the liquid metal PFC surfaces into the plasma maybe be excessively large, resulting in the formation of a relatively cold, dense secondary plasma region in front of the irradiated PFC surface.…”

First principles study of the static arrangement of a plasma facing component in the form of a capillary porous system (CPS)

“…Capillarity is expected to provide the necessary driving force to replenish the depleted liquid metal/plasma interface, as a result of evaporation, by drawing liquid from a reservoir. Tabarés [46] noted that the pore size for flow in the supply passages is not always the same as that for retaining the liquid on the surface of the PFC, which further complicates modelling of the CPS arrangement. Lyublinski et al [18] indicated the possibility of PFC protection from the high power load related to cooling of the tokamak boundary plasma by radiation of non-fully stripped lithium ions, an effect supported by experimental results.…”