> Isn't thorium also pretty abundant?

Yes. Even more so! But that doesn't mean it's easy to get. Everything has to be processed at the end of the day.

The reason I brought up uranium is that it is easier to fissile. So sure, there's more thorium but it requires more processing. Why use it when we aren't concerned about uranium access? Uranium is already "cheap". (We could get into an analogy with different types of oil if that helps. Like why the US produces so much, exports it, then buys a different type)

> I've also never really gotten the proliferation concern.

There's two issues here:

1) sure, the US doesn't care if California gets a bomb, but Russia and China sure do.

2) Breeder reactors are reactors that make higher elements.

Discussion of thorium are often extremely over simplified. Proliferation always ALWAYS must involve international relationships. When we get into that the logic changes. You need to consider a lot of higher order effects/connections since everything is always being used as leverage for other things.

Breeding is also a very complicated topic. Just like enrichment. Look at the Iran deal. They can do enrichment but only do much, right?[0]. Often fine because it's hard to scale and generally noticeable. But the same is true for breeding. Instead of turning one atom into a different isotope (e.g U238 -> U235) you change an atom to a different atom (e.g. Th233 -> Pa233 -> U233). This all happens in the reactor. It's hard to separate but hard to track. You can also keep breeding (fast reactor = more/high energy neutrons), where do you think plutonium comes from? The reason it is better for proliferation concerns is it increases the difficulty. At worst, you need to start earlier. But what I wanted to combat is the misinformation that thorium __can't __ be used for proliferation, making it safe for.., idk, Iran? It's good to add more barriers.

I'll also add waste. This is often discussed too. This is again fraught with nuance. We can dramatically reduce waste but we don't. There just isn't much of it and doing more fission is less economical. That is, unless you don't have lots of uranium laying around. That's the case with France, so they "recycle" their waste and in the process this dramatically reduces it. You can fit over 50 years of waste in a Costco and they do. You also can use similar technologies as thorium would need with uranium and still reduce waste. So that points us back to the opening: yes, thorium is abundant, but why go through all that effort when we got plenty of uranium which is cheap and efficient?

I recommend poking around AcidBurn's website. He has a lot of good information and I think he's written well in a way that's fairly approachable (it is nuclear, it's by default not approachable and easy to think you understand much more than you do. If you went through a physics degree this is often a confusing class taken at the upper level).

[0] When they broke the agreement and made more they suspiciously only made a small amount more which would take a long time to get enough for weapons. But they were also loud. Great strategy because public gets afraid, it's a threat, but they also signal that they're willing you deal but want to renegotiate (only experts would know this though). The interesting part is how their best weapon was our own fear and ignorance.