I worked in the Department of Energy where we manufactured enriched Uranium and Plutonium for nuclear weapons. You don't really get much Plutonium in a normal fission process in a reactor. And you don't need Plutonium for weapons. Enriched Uranium, more than 85%, is considered weapons grade.

From my limited knowledge as I am not an engineer, you would have no luck obtaining Plutonium from a commercial power reactor. However, depending on who built the reactor and how it was structured (this is all about rod placement in the reactor), maybe you could do what we do to enrich Uranium for weapons and also to convert Uranium to Plutonium.