I was reading lately about fast reactors, breeders, and desirable high-temp reactors; and it seemed most new reactor concepts being studied today are more difficult than existing reactors in at least one way. Supercritical water reactors need to battle with ever more hot and high pressure water (for one, Zr cladding won't work); Reduced moderation reactors have such narrow passages for water around fuel rods (about 1mm) that I imagine there are concerns about local overheating and rod damage if anything goes just a little bit not as planned. Heavy water reactors seem to be easier than above, but they produce more tritium (a bit of PR nuisance) and also they need heavy water on the order of $1 billion per reactor. Also, same problems attempting to go to higher temps as with ordinary water. Molten lead-cooled reactors seem to be nice, but (1) lead is corrosive, (2) breeding is hard to achieve (barely reaches 1.0), (3) lead is heavy (problems with seismic resistance). Molten sodium is fire hazard (empirically proven by Japanese). Etc... Which made me thinking. Aren't there ways to dodge these problems, instead of attacking them head-on ("we will make even better cladding from super stable grade of stainless steel" etc)? Also, won't KISS principle be good in nuclear engineering too? As an example, liquid fluoride thorium reactor, or aqueous homogeneous reactor. On one hand, I'm far from thinking nuclear engineers are less clever than me, and didn't think about it before. So my ideas are likely to be already considered and deemed not viable. OTOH, if I will not ask, I will not find out, right? So, here is my (likely stupid) question: Is it possible to construct a high temperature, fast breeder reactor where the fuel is in the form of molten uranium (possibly with plutonium)? Akin to molten lead fast reactor, but... without lead. Pros: * cladding problems are gone because there is no cladding :) * excellent neutron economy :) * near-atmospheric pressure * naturally high-temperature (above 1405 K, wow) * homogeneous active zone (no hot spots, local overheating damage hardly possible) Cons: * Needs refractory reactor vessel (Mo? W?) * Is molten uranium corrosive? * Is it safe (is temperature coefficient negative)? * If it freezes, may be hard (impossible?) to restart * Will it damage reactor vessel when melt freezes? * Others?