>the entire first wall is thick flowing liquid lithium Yeah, I agree on the liquid walls. I think the optimum might be to have a thin Li first surface flow tha

>the entire first wall is thick flowing liquid lithium Yeah, I agree on the liquid walls. I think the optimum might be to have a thin Li first surface flow that is relatively cool, then a shell of SiC, and behind it a PbLi breeding blanket that can be at higher temperature. There's a trade-off because the first-surface can't be made too hot or the evaporation will pollute the plasma, but getting high thermodynamic efficiency means using higher coolant temperature. The thickness of the liquid first-surface plays into the lifetime of the SiC shell -- more shielding in front of it means longer life (so lower maintenance costs & higher reactor up-time, and less radwaste), but lower thermal conversion efficiency on average. There are problems of course -- corrosion by Li, splashing of droplets into the plasma, MHD drag & pump power requirements, incompatibility of lithium with many forms of sensors & actuators for plasma control.... (OTOH, most sensors and actuators can't tolerate radiation anyway, so fancy control techniques just don't stand a chance in a reactor anyway. We need boring, stable plasma configurations that just sit there and work.) >What is the other reason? Some people think they can make a fortune :D