Upgrades toward high-heat flux, liquid lithium plasma-facing components in the NSTX-U

Abstract

Liquid metal plasma-facing components (PFCs) provide numerous potential advantages over solid-material components. One critique of the approach is the relatively less developed technologies associated with deploying these components in a fusion plasma-experiment. Exploration of the temperature limits of liquid lithium PFCs in a tokamak divertor and the corresponding consequences on core operation are a high priority informing the possibilities for future liquid lithium PFCs. An all-metal NSTX-U is envisioned to make direct comparison between all high-Z wall operation and liquid lithium PFCs in a single device. By executing the all-metal upgrades incrementally, scientific productivity will be maintained while enabling physics and engineering-science studies to further develop the solid-and liquid-metal components. Six major elements of a flowing liquid-metal divertor system are described and a three-step program for implementing this system is laid out. The upgrade steps involve the first high-Z divertor target upgrade in NSTX-U, pre-filled liquid metal targets and finally, an integrated, flowing liquid metal divertor target. Two example issues are described where the engineering and physics experiments are shown to be closely related in examining the prospects for future liquid metal PFCs.

Hydrogen retention in lithium on metallic walls from “in vacuo” analysis in LTX and implications for high-Z plasma-facing components in NSTX-U

“…As an intermediate step prior to the implementation of a fully-flowing liquid lithium divertor, tiles that are prefilled with candidate liquid metals are under consideration for high-Z PFCs in NSTX-U. [17] The liquid metal would be transported from the interior of the tile by a wick in contact with a prefilled reservoir. Like the Capillary Porous System (CPS) [18], the PFC surface would be textured to enable wetting.…”

Comparative Analysis of Lithium First Wall Concepts for Tokamak with Reactor Technologies

“…Based on the existing analytical reviews and our own experience [3][4][5][6][7][8]15], we believe that the most reasonable scheme consists in using the slow drift of liquid metal over the CPS porous surface or directly inside its structure. This scheme provides for the selfrenewal of the ICE surface of any shape and orientation and the LM stabilization in relation to the effect of the electromagnetic forces due to the capillary forces acting in the CPS.…”

“…The main ideas of the alternative ICE concept can be formulated based on the comprehensive analysis of the problems and requirements arising during the development of ICEs of the stationary reactor, for example, the DEMO-type reactor [1,2]. It is also necessary to take into account the modern experience and achievements in the fields of design, material science and technology of structural materials, as well as the distinctive features of using LMs in the fusion facilities with magnetic plasma confinement [3][4][5][6][7][8]. The article presents the analysis of possible design of the lithiumcoated ICEs and discusses the main ideas of the lithium first wall concept for the tokamak with reactor technologies (TRT) [9].…”

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

“…Moreover, International Symposia on Lithium Applications in Fusion have extensive information on Li R&D [11][12][13][14]. Jaworski [15,16] and Nygren and Tabarés [17] have provided reviews of liquid surfaces with an emphasis on Li, as have Lyublinski et al [18] but with a focus on capillary pore systems. In addition, Coenen summarized considerations for several liquid metals for power exhaust systems in future fusion devices [19].…”

“…4. 16 illustrates the anticipated static arrangement as well as the interplay of the different forces acting on the liquid metal "drop". The surface tension forces, in the vicinity of the three phase contact line, tend to "pin" the liquid metal onto the solid substrate and, thus, stabilize it against pressure forces.…”