This is a nit-pick, and as much a physics question a dictionary one. The newspaper noted that Iran can now enrich uranium sufficiently that it becomes fissile.

The dictionaries define 'fissile' as 'able to undergo nuclear fission' (or, chiefly of rock, 'easily split'). But are the dictionaries wrong? As I understand it, any uranium will on its own (spontaneously) undergo fission, very slowly; that is what it means to be radioactive. That is, any uranium is 'fissile' within the dictionary definition. In fact any element at all meets the dictionary's definition (because it will divide if bombarded by sufficiently energetic neutrons).

I'd think the paper is using 'fissile' properly. It's the dictionaries that are mistaken, not the paper.

Thoughts and comments?

I would imagine that they're using the word to mean explosively fissile, as pure enough for a bomb

I agree with Dale, but feel that the newspaper writer doesn't know enough about the subject to be writing about it. It's like someone saying, "I've got a gun and six bullets." A bullet is only the projectile; one needs the cartridge, or round of ammunition, not just the bullet, unless one plans to kill by throwing the gun at someone. We hear this error constantly in news reports, thanks to TV writers who know nothing about firearms.

Asa, I'm not following your analogy. What's wrong with the newspaper account?

On the original matter: my suggestion is that the newspaper has it right and the dictionaries have it wrong. That is, that fissile does not mean "able to undergo nuclear fission", but rather means "radioactive and sufficiently pure that, if brought together in sufficient mass [critical mass] and triggered, it will undergo a self-sustaining chain reaction of nuclear fission".

I can't argue either way, but as an engineer-writer I have noted that most writers are not technically inclined; and conversely, most engineers are only semi-literate. It's as if one ability precludes the other