The problem is that you can't say that 'the regulations are not the issue' because its regulation that prevent all research in that direction. The way the regu

The problem is that you can't say that 'the regulations are not the issue' because its regulation that prevent all research in that direction. The way the regulation works at the moment makes building a test reactor basically impossible for a company to do that's why pretty much every single nuclear company produces directly to a production model. Thorium breeding was proven, but not in the MSR. So that does not necessarily need validation. The 2-fluid reactor design would need a test reactor, but there are other reactor designs, like the IMSR that really would not need much further research. However, if you don't go to a fuel breeder with online refueling thorium does not buy you much. Uranium is fine and does everything you want and that's why most MSR companies use Uranium.