Thorium is a naturally-occurring element that is so safe you can hold it in your bare hand, that’s four times more abundant than uranium, and that’s so dense and highly efficient, a ball bearing-sized amount could provide all the power an average person will consume in their lifetime.
I assume it would cost a lot in R&D although other nations are currently experimenting LFTR. Beside that, I don't think the cost-benefit is at a point where it would make sense. It's one thing to produce energy but it's another entirely to distribute it. We need to develop both source and distribution.
There is a great video on thorium reactor that was posted here or on reddit a while ago.
One rather important thing about thorium vs. uranium that is never spelled out in most texts but is very essential- thorium is what they call a "fertile" material, whereas uranium is a "fissile" material. Fertile materials can produce nuclear energy, but they require fissile material to get the reaction started.
In theory Thorium's economics are far better than those of Uranium, but the above factoid makes a full switchover complicated.