I believe you're getting confused with a Liquid Floride Thorium reactor. That tech has been done and is proven already (during the cold war), but is very hard to use to make nuclear weapons. Travelling wave reactors are purely theoretical at this point and although they are also non-weaponisable, there are still many technological hurdles to overcome to make it actually work. The fact that all this research is going on is great though. We still need more.