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Comment by HorstG | Hacker News Reader

It is useless to make claims about a particular fuel without looking at a concrete reactor design. Leftover isotopes for example are very dependent on neutron flux and neutron energy as well as general breeding properties of the reactor. This in turn decides the waste to be dealt with, proliferation risk and possible reuse of leftover fuels from previous generation reactors (which the submission didn't even discuss).

Also, the answers lack nuance. E.g. proliferation risk is present through U233, however, U233 seems very difficult to deal with in bombmaking. So at least it's less of a problem maybe.

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Its easy to make bombs from U-233. In fact it is better than plutonium in some rare circumstances. Check out the discussion and cool declassified letter from the Livermore bomb letters here: https://whatisnuclear.com/thorium-myths.html#myth3

Yes, making the bombs themselves seems to be easy. The difficulty comes from U232-contamination which decays into strong gamma emitters, making handling difficult. However, there seem to be paths for the production of pure U233 from chemically separated Pa233, which one might be doing anyways in a thorium reactor. That would mean a significantly higher proliferation risk, because one would get pure bomb fuel form the normal operations of the reactor. However, I don't know enough about how easy or likely that would be to judge.

But in all, you are right, I think. And maybe even more than right.

I mean to say that making clean U-233 (with very little U-232 and daughters) is easy. Certainly assembling a bomb given pristene weapons material is particularly easy.

I'm a reactor designer and study this kind of thing. It's really just a question of how fast you move your Th-232 through a neutron cloud. If you move it relatively quickly and then do your Pa separation you can get very nice U-233 from Thorium.

The nice thing here about low-pressure fluid fuel reactors is that you can move material in and out fairly readily.

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