What is the Future of Nuclear Energy? 

The only fluid fuel reactor mentioned was fusion or plasma fluid reactor. Nuclear Fission also can be done using fluid fuel reactors. There are 3 liquid fuel reactor concepts that got tested at US national labs during1950-60s 1. Molten salt reactor (Oak Ridge National Lab) 2. Aqueous Homogeneous Reactor. (Oak Ridge National Lab) 3. Liquid-metal fueled reactor (liquid uranium metal). (Brookhaven National Lab) Liquid Fuels can be moved quickly using pipes and pumps. The main advantage of using fluid fuel reactors is the liquid-fuel reprocessing can be done while the reactor is running. With online reprocessing, a closed fuel cycle can be achieved as a continuous flow process.Also there is absolutely no structural damage to the liquid-fuel. The liquid fuel can stay inside the reactor until it is fully spent. Among the three liquid fuel reactors, the molten salt reactors were considered more practical.

even smaller reactors can be used for district heating. remote locations like RTG on mars Curiocity

Cool!