Lithium takes the heat in fusion reactorsS. Himmelstein | February 07, 2021
The extreme heat that could impact exhaust systems in reactors poses a design challenge in current fusion energy systems. Heat flux can damage divertor plasma facing components in exhaust systems and stall fusion reactions in tokamaks. A solution advanced by researchers from the U.S. Department of Energy's Princeton Plasma Physics Laboratory (PPL) focuses on radiative liquid lithium divertors to remove excessive heat from these components and allow continued core plasma operation.
The injection of lithium pellets injected into the divertor would liquify and radiate strongly, diffusing much of the extreme heat escaping from the core of the plasma and minimizing the amount striking the divertor wall. Lithium is currently injected into tokamaks with simple, gas gun injectors that tend to inject a load of gas into the vacuum chamber housing the core plasma, which could cause problems. The gas guns could be replaced with newly engineered high-speed electromagnetic particle injectors designed to remain in stand-by mode until needed and inject a radiative payload on a fast timescale.
Extreme heat flux is signaled by sudden flashes of light that heat bursts produce at the edge of the plasma. Such bursts could reach the divertor in about 10 milliseconds, but the electromagnetic particle injector would rapidly fire a high-speed projectile into the divertor region to radiate away the onrushing heat flux.
The researchers plan to test the lithium injection system at the National Spherical Torus Experiment-Upgrade fusion facility at PPPL.
A paper on this study is published in the Journal of Fusion Energy.