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Comment by adrian_b | Hacker News Reader

Thorium is more abundant than uranium and as said in the article China already has huge amounts of extracted thorium as a waste product from the extraction of rare-earth metals.

Thorium must not be enriched and it cannot be enriched like uranium, because it has only one isotope with a long life, thorium 232, which is the only natural isotope.

Natural thorium is not usable as a fission fuel, but it can be transformed into uranium 233, which is a fission fuel, by another nuclear reactor.

The extraction of uranium 233 from thorium has nothing to do with uranium isotopic enrichment. It is a process orders of magnitude simpler, because it is just a normal separation of distinct chemical elements.

This is actually the reason why thorium reactors have been avoided, because it has been considered that it is too easy to separate the uranium 233 from the fuel, which can be used for making nuclear weapons.

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You're right that thorium can't be enriched because there's only one isotope. It needs to be bred to Uranium-233 to work. However, breeding has been more expensive and costly than enrichment, and this is the crux of why thorium use wasn't expanded in the past. To breed thorium to uranium-233, you need a breeder reactor, and you need a chemical separation facility. Together, these are more expensive to build and operate than a centrifuge and simpler non-breeder reactor.

In this sense, I disagree that the process is orders of magnitude simpler. I'd argue that it's the opposite!

The idea that thorium-derived material can't be easily used to make nuclear explosives is an unfortunately persistent myth. You can easily make very nice weapons material from thorium. As the Livermore weapons designers once said:

"If today's weapons were based on U-233, [we] would have no interest in switching to plutonium" [1]

[1] https://www.osti.gov/biblio/79078

> This is actually the reason why thorium reactors have been avoided, because it has been considered that it is too easy to separate the uranium 233 from the fuel, which can be used for making nuclear weapons.

This is absolutely not the reason thorium reactors have been avoided at all.

The reality is that uranium enrichment infrastructure existed and fuel isn't a huge part of the cost.

Most of the funding happened in the early days and they were of course using uranium, people back then figured that uranium would run out and were interested in breedres. But pretty quickly, uranium was found to be pretty common.

Uranium is also just better unless you are doing a thorium thermal breeder. And that design only really works well with a pretty complex reactor setup that most people were simply not interested in.

  > Thorium is more abundant than uranium

I don't disagree. What I said is that uranium is __also__ abundant.

  > Thorium must not be enriched and it cannot be enriched like uranium

You're right. I was trying to use language that people would generally understand. Mixing breeding and enriching. They are quite similar words, differing in protons. Enrich = changing isotope (adding/subtracting neutrons), breeding = changing atoms (adding/subtracting protons). I thought this would be fine, sorry. Yes, you are right.

  > The extraction of uranium 233 from thorium ... is a process orders of magnitude simpler

You are oversimplifying things. There's plenty of "simple chemical separation processes" that are very expensive. And sure, you can get 233 from this and use it for weapons but you still want some other elements if you're going to build a weapon. There's a lot to this and acidburn would be the better person to explain all that nuance.

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