what is the most promising gen 4 or 5 nuclear reactor design? i heard bill gates wants to invest in traveling wave reactor. to limit the field, it has to use uranium, must be economical, must produce very little waste, must be safe, and it can be built with current technology. built in a nuclear friendly nation (not sure which nations are nuclear power friendly - germany has a moratorium) or what is your personal preference if you are a nuclear engineer 1 Reactor types 1.1 Thermal reactors 1.1.1 Very-high-temperature reactor (VHTR) 1.1.2 Molten-salt reactor (MSR) 1.1.3 Supercritical-water-cooled reactor (SCWR) 1.2 Fast reactors 1.2.1 Gas-cooled fast reactor (GFR) 1.2.2 Sodium-cooled fast reactor (SFR) 1.2.3 Lead-cooled fast reactor (LFR) Liquid-core reactor. A closed loop liquid-core nuclear reactor, where the fissile material is molten uranium or uranium solution cooled by a working gas pumped in through holes in the base of the containment vessel. Gas-core reactor. A closed loop version of the nuclear lightbulb rocket, where the fissile material is gaseous uranium-hexafluoride contained in a fused silica vessel. A working gas (such as hydrogen) would flow around this vessel and absorb the UV light produced by the reaction. This reactor design could also function as a rocket engine, as featured in Harry Harrison's 1976 science-fiction novel 'Skyfall'. In theory, using UF6 as a working fuel directly (rather than as a stage to one, as is done now) would mean lower processing costs, and very small reactors. In practice, running a reactor at such high power densities would probably produce unmanageable neutron flux, weakening most reactor materials, and therefore as the flux would be similar to that expected in fusion reactors, it would require similar materials to those selected by the International Fusion Materials Irradiation Facility. Gas core EM reactor. As in the gas core reactor, but with photovoltaic arrays converting the UV light directly to electricity. Fission fragment reactor Hybrid nuclear fusion. Would use the neutrons emitted by fusion to fission a blanket of fertile material, like U-238 or Th-232 and transmutate other reactor's spent nuclear fuel/nuclear waste into relatively more benign isotopes.