Up until quite recently, nuclear has been decently economical as it is - but indeed, a lot of nuclear investments of the previous century were made with obtaining weapon-grade plutonium in mind. It's one part of why countries went with uranium cycle to begin with.

Modern research into thorium-based reactors that could be cheaper, safer and not produce nuclear weapon material is too little too late. Renewables already took over the game.

Anyway, I added this to the original response, as I think it is a vital part I forgot to mention.