Australia's export of uranium to India.

India has made an explicit decision not to sign the nuclear non-proliferation treaty (NPT). As a member of the Nuclear Suppliers Group, Australia is supposed to export only to countries that have signed the NPT. An exemption has been granted to India. This means India is receiving uranium from Australia, but its facilities are not subject to the full range of inspections required under the NPT. It's reasonable to assume that India will go as far as it can in its role as a non-signatory to the NPT.

Essentially India said "trust us", and Australia said "show us the money."

Not only do we have low assurance that Australian uranium won't end up in weapons, but indigenous sources of uranium can now be dedicated 100% to weapons, instead of being shared with energy production. There is also the use of neutrons from 'energy uranium' being used to produce tritium from lithium-6, which is essential for producing fusion boosted and thermonuclear weapons.

http://isis-online.org/isis-reports/detail/north-koreas-lith...

India has been a nuclear power since 1974.

I guess you're right under the definition of proliferation being a new nation gaining nuclear weapons. I was thinking of proliferation, in the sense of their being more nuclear weapons, even if it doesn't involve a new nation.

I don't see any reason why countries committed to nuclear non-proliferation should endeavour to make weapon production cheaper. In fact, they should have to decide between peaceful uses and weapons of mass destruction.

Speaking only about U233, produced in the thorium fuel cycle: it's been used in composite fission cores in several tests by USA and (then-) USSR. There may have been one small test of an unmixed U233 device by India. [1]

So maybe U233 could be used to make a weapon. I don't know whether that possibility makes it a big proliferation risk or not.

[1] https://en.wikipedia.org/wiki/Uranium-233

https://en.wikipedia.org/wiki/Nuclear_proliferation ? Thorium/breeder reactors don't work for large booms, but would be fine for small booms and dirty bombs.

>Thorium/breeder reactors don't work for large booms

Thorium breeder reactors in fact will work just fine for big booms by selectively producing protactinium-233 and then running it through a couple of decay and chemical separation cycles.

What I mean to say is:

Consider that the world's first commercial nuclear power station, Calder Hall at Windscale, England, was opened in 1956¹, has there ever been a nuclear material used as a weapon other than the obvious two and conventional depleted uranium armour piercing projectiles?

1. https://en.wikipedia.org/wiki/Nuclear_power#Early_years

If you're going to count DU shells as nuclear proliferation, you should also count Po-210 poisoning (Litvinenko, and perhaps others) and that guy who poisoned his gf with I-131.

Though, when talking of nuclear proliferation, we almost always mean just the proliferation of nuclear and thermonuclear explosive devices.

North Korea used a power reactor to produce all of the Plutonium for its nuclear explosive devices, some of which were supposedly of a weapon form-factor have been used. If by "used" you mean "used in anger", then of course, there are only the two instances. (It also should be noted that in the context of nuclear reactors and proliferation, Little Boy is only tangentially related. Nuclear reactors weren't used in the production of Little Boy.)

That didn't happen by accident, but was the result of caution (and probably lowish number of attempts).

I would be curious to hear how/if thorium presents a qualitatively different proliferation problem.