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