Because of the recent events, I came across molten salt reactors
. Never heard of those before, but apparently, they are much safer, cheaper and basically better. There is for example not the risk of a reactor meltdown because of their architecture. The only apparent reason that they are not in use is political: The companies building the current types of reactors simply didn't want to switch, since they had all work done already for building the types of reactors currently in use. Interesting stuff.