Funding is the biggest issue. No lending company will front billions for a pay off in 10 years. Thorium hits the same barrier.
And then it spends the next 30 years paid off and operating. With potentially a 20 year extension beyond that. At least with current regs.
But, regardless of that part of it, how do you propose we provide baseline power? Especially to replace the 104 nuclear plants in operation today throughout the US when they go offline in ~15-20 years. Coal is worse than nuclear as far as contamination byproducts are concerned. LNG is possible, but has other issues (although it's the best non-nuclear baseline power option out there at present). Hydro is tapped out. Wind/Solar don't provide baseline power at present, are still expensive, and take up a lot of land mass. So if you remove nuclear, how do you propose we power the nation with present technology?
People talk about how bad nuclear is. About various releases from different reactors throughout the country. Think about it this way, when some of these reactors were built we hadn't even landed on the moon yet. Two of the entire Space Shuttle programs could have happened during the time that some of these plants have been active. These are mainly gen 2 plants, they are old, and old things break. Replace them with Gen 4 reactors at minimum, or better yet use LFTR's. In either case you get passive safe systems that can self regulate down to safe levels so you don't get meltdowns (or the risk is mostly eliminated anyways). Allow for reprocessing spent fuel which can help to reduce our current crap ton of high level waste. Hell with LFTR's you can even burn that in the reactor. Oh and LFTR's don't provide weapons grade material so you can reduce/remove proliferation concerns.