Active Radiative Liquid Lithium Divertor for Handling Transient High Heat Flux Events
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ORIGINAL RESEARCH
Active Radiative Liquid Lithium Divertor for Handling Transient High Heat Flux Events M. Ono1
•
R. Raman2
Accepted: 7 September 2020 Ó Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract The extreme heat flux anticipated in fusion reactor divertor plasma facing components (PFCs) is perhaps the most challenging technology issue for fusion energy development. Most divertor PFCs are designed based on the maximum steady-state operational limits. Application of lithium (Li) in NSTX resulted in improved H-mode confinement, H-mode power threshold reduction, and reduction in the divertor peak heat flux while maintaining essentially Li-free core plasma operation even during H-modes. These promising Li results in NSTX and related modeling calculations motivated the passive and active radiative liquid lithium divertor concepts (RLLD and ARLLD) (Ono et al. in Nucl Fusion 53:113030, 2013; Fusion Eng Des 89:2838, 2014). This radiative process has the desired effect of spreading the localized divertor heat load to the rest of the divertor chamber wall surfaces, facilitating divertor heat removal with relatively small amount of lithium * few moles/s to handle the expected steady-state high divertor heat load. However, in addition to the high steadystate heat flux, the fusion reactor divertor PFCs could also experience significant transient heat flux such as ELMs and/or other magnetic reconnection events which can deposit large transient heat flux onto the divertor PFCs. If unprotected, it could damage the divertor PFC surfaces which could lead to a highly undesirable unplanned shutdown for PFC repair and/ or replacement. In this paper, we explore feasibility of LLD and ARLLD concepts in handling such transient heat flux to protect the divertor PFCs from the extreme transient heat flux while maintaining the normal plasma operations. We also suggest a possible implementation technique using inductive pellet injector for the reactor PFC protection from transient heat flux which can be tested on NSTX-U. Keywords Transient heat flux Divertor Liquid lithium Active injection
Introduction The extreme heat flux anticipated in fusion reactor divertor PFCs is perhaps the most challenging technology issue for fusion energy development [3, 4]. While tungsten has been identified as the most attractive solid divertor material, many challenges including possible surface melting and cracking were identified. Such deleterious modification of the PFC surfaces by the plasma must be prevented to develop reliable plasma facing components (PFCs) [5].
& M. Ono [email protected] 1
Princeton Plasma Physics Laboratory, PO Box 451, Princeton, NJ 08543, USA
2
University of Washington, Seattle, USA
Most divertor PFCs are designed based on the maximum steady-state operational limits. In a steady-state situation, quite aggressive active cooling is necessary to remove large PFC heat flux and the heat removal limit is determined by the heat conduction from the maxi
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