Princeton Plasma Physics Laboratory (PPPL) scientists have been working to sprinkle boron powder using an injector as part of a tokamak design to promote heat retention and protect the walls of the reactor. Physicist Robert Lunsford said the main goal of the recent experiment was to see if they could use a powder injector to coat the walls of the tokamak as part of a boronization process. The possible major upside shown was that boron could be added to the plasma while the machine is running in a steady state. This is something that was not thought possible but will be required in a commercial reactor to protect the walls of the tokamak.
Great article with images: https://www.asiatimes.com/2019/12/article/powder-could-solve-explosive-gas-mix-in-fusion/