New approach to cleaning the inner walls of a fusion system removes another obstacle to near-endless energy
Fusion systems need inner walls that can withstand extreme heat. One promising solution uses liquid lithium to protect the walls, held like water in a sponge made of the exceptionally strong metal tungsten. An advanced manufacturing process can be used to make tungsten into sponge-like wall tiles with lots of pores for flowing liquid lithium. But this process also leaves the tungsten contaminated…
Researchers at the U.S. Department of Energy's Princeton Plasma Physics Laboratory, Princeton University, and Pennsylvania State University have discovered a novel method to clean porous tungsten tiles used in fusion systems after they have been installed inside the system. The contamination issue stems from carbon, oxygen, or nitrogen impurities that react with liquid lithium, causing the lithium to fail in flowing properly.
Traditional cleaning methods were ineffective, but the new approach uses heat in combination with particles from a neon plasma to remove the contaminants from the tungsten tiles in vacuum chambers, where air exposure is not an issue. The process was tested in the Lithium Tokamak Experiment-Beta fusion system at PPPL. The results showed a significant increase in clean, metallic tungsten surface, from 0% to 87%, and a sharp drop in carbon content.
This in situ cleaning method avoids recontamination from air exposure and could help future fusion systems run more efficiently with liquid lithium.
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