system
Given the following post, respond as if you're commenting on Reddit:
human
Can nuclear power plants be used to create nuclear weapons?

I think I heard something like that in a video from Kurzgesagt but I don't understand why and how.
gpt
Nuclear reactors which use natural or enriched uranium as fuel will automatically breed plutonium-239 and to a lesser extent plutonium-241, which are both fissile isotopes.

So any country or organization that has control of a nuclear reactor theoretically has the ability to produce weapons grade plutonium. But that doesn’t mean that they’ll automatically have a nuclear weapon. Many countries have nuclear power industries, but have not produced nuclear weapons.

Typical power reactors are not optimized for plutonium production. It turns out that to optimize the production of plutonium-239, you only want the fuel to reach relatively low burnups before doing the chemical separation. A typical LWR power reactor might refuel every two years or so, so the burnups get higher. There will still be plutonium-239 in the spent fuel, just not as much as there could’ve been.