What does '%' mean in nuclear?

[hunter_hunted]

Enriched uranium is a type of uranium in which the percent composition of uranium-235 has been increased through the process of isotope separation. Natural uranium is 99.284% 238U isotope, with 235U only constituting about 0.711% of its mass. 235U is the only nuclide existing in nature (in any appreciable amount) that is fissile with thermal neutrons.

So you are saying we can't eat it right? Only sniff it

 

[Dante80]

It is generally beneficial to not come near anything sporting the combination of words "enriched" and "uranium".