system
Given the following post, respond as if you're commenting on Reddit:
human
What is meant by "weapons grade" uranium/plutonium?

I'm not sure if it's just common slang or military talk. Is there an actual difference? Does the uranium and such used in weapons actually differ from that which naturally occurs or is used in energy. Also, tag on question - what is depleted uranium used in weapons such as artillery shells?
gpt
There is an actual difference. The difference is that "weapons grade" material is highly enriched with the fissile isotopes of the uranium/plutonium.

Natural uranium has less than 1% concentration of the naturally-occurring fissile isotope (uranium-235). For a uranium fission bomb, you need at least 80-90% uranium-235. So "weapons grade" material has to be highly enriched in order to remove a lot of the uranium-238 and increase the concentration of uranium-235.