Thorium is an element 4 times more abundant than uranium that is basically the holy grail of nuclear reactors, I have been making multiple types of reactors in the game recently and I was dissapointed at the impossibility of making a Thorium based LFTR or similar types of reactors, Thorium is a fertile element that given neutrons will eventually decay into uranium 233 and if a flow of neutrons is stopped the reaction also stops, hence why I always wanted this to be able to make a nuclear reactor that can autoshutdown in case of an emergency.