Its the frontier of reactors-that-don't-explode. In the short term, our laws were written with light water reactors in mind, so anybody who wants to build a thorium reactor is going to have to build all the same expensive safety features that light water reactors need, plus the special metallurgy that molten salt reactors need. So basically it doesn't make sense until something changes.
> In the short term, our laws were written with light water reactors in mind, so anybody who wants to build a thorium reactor is going to have to build all the same expensive safety features that light water reactors need, plus the special metallurgy that molten salt reactors need.
It always annoys me that laws on safety requirements go into implementation details rather than stating the desired result. If the requirements simply said that "an independent audit must show that the safety exceeds the following thresholds: ...", safer technologies wouldn't incur the additional overhead you describe.
Thorium reactors are often MSR designs too. But if this offers the possibility of reducing our existing waste supplies, it might make it more publicly palatable.
80% of the cost of nuclear energy is building the reactor. With around $500B worth of existing reactor infrastructure worldwide, which runs on Uranium, don't expect that to go away too soon.
I do not think they are simply attempting to replace existing reactors. I know in many countries governments have slowed down building reactors because of environmental concerns and costs. With the dwindling oil deposits and increasing energy need, safe and reliable nuclear reactors will be in high demand.