Re: Just the beginning
As a matter of fact, you are misinformed. From your statement I'm betting that you're referring to the Oak Ridge National Laboratory Molten-Salt Reactor Experiment (MSRE). Most thorium proponents who haven't read up much do. The US ran molten salt reactors in the 1960s (a type of reactor that is the most likely candidate for Thorium use today), however, the MSRE didn't actually use thorium during the experiments.
Now, there have been many Thorium reactors built and run over the years. A smallish Thorium reactor actually isn't that hard to build, and they don't technically have to be molten salt reactors. (That's just the sanest way to do it at any scale.) The ticket here is that you can't just shove Thorium into a reactor, wave a magic wand and poof have power.
So here's the deal: the Thorium you can pull out of the ground on Earth is Th232. In order to get Th232 to split you need to modify it, generally into u233 via the absorption of a Neutron. In order to do that you need a neutron donor. This mean feeding the thing materials that barf neutrons.
Back in oldentimes, that was easy. We cranked that stuff out of breeder reactors all the time. Today, we do this a lot less. What's more, while you can technically crank a Thorium reactor with just about anything that will emit neutrons, in reality only a few isotopes are ever going to be okay for civilian use. This is because, for one reason or another, they're considered really, really stupid for people to try to steal for nuclear proliferation purposes.
The big problem we have today is that we just don't make a lot of those isotopes any more. (Consider, for example, that we're almost out of Plutonium for RTGs.) What we do make has everyone under the sun - from existing Thorium burners to researchers - clamoring for it. Also, in case you hadn't noticed, but international politics have become pretty xenophobic and awful of late, which doesn't help.
So, if you really want to go Thorium in a big way, you're going to have to build a Thorium program. That means building non-Thorium reactors to provide your jump-start isotopes, the security apparatus around their use and transport etc. etc.
You are also most likely to try to use Thorium in a molten salt reactor these days (for various practicality reasons), which means additional investment in facilities which clean impurities from the salts. Oh, and you have to figure out what to do with all the Neptunium.
The other alternative is you just wait around and hope to your deity that the proposed experiments to modify a CANDU reactor to burn Thorium work and are considered generally safe. Almost everyone has CANDU reactors, so if we can just stuff Thorium in there maybe we can run a hybrid facility with one reactor that's not Thorium and the rest that are.
It's important to note here that the big drivers behind the CANDU Thorium cycle are the Chinese. This is because they're not batshit crazy about nuclear waste like the Americans (and their empire of lacky nations) are. The Americans think piling up a bunch of highly radioactive nuclear waste (almost all of which could be refined and used to build bombs) without any long term storage facility is a really great idea an everyone should do that.
The Chinese, on the other hand, think that's raw lunacy and said "hey, can we take this pile of highly radioactive slag and burn it?" (Answer: yes, you can do that in a Thorium reactor. They're great for that.)
But the Chinese are rational about such things and basically the entire rest of the world (except India) isn't. The Chinese are perfectly willing to take their 300+ nuclear reactors worth of waste, drive the waste via heavily armed whatever on a shoot-first-and-take-questions-never approach to a giant Thorium facility and burn the whole thing until all that's left is a bunch of Neptunium and some decay products that have half lives so long they're not a threat.
There is no way you get a western nation to make that kind of decision. "Nuclear" is a boogyman and some group somewhere will terrify the populace into screaming their heads off. So meanwhile, we all live with giant piles of insanely radioactive material for the next several thousand years and expensive electricity whilst the Chinese build a way to dispose of nuclear waste, drive down electricity costs and, oh yeah, figure out how to turn a really small amount of naturally neutron-emitting material into something that can power humanity for the next million years.
That's why it takes 50 years to build a proper full-scale Thorium program. (See: India.) Because the US won't give you what you need to start burning Thorium today even though they are literally sitting on metric tonnes of it that they don't have a long term facility for.
Because politics. Because humans are morons. Because we live in the darkest possible timeline and everything is awful forever.