isn't it both? It's valuable fuel and radioactive waste? I see 2 immediate problems though: 1. you don't know when the fuel is exhausted or if you can reuse it

isn't it both? It's valuable fuel and radioactive waste? I see 2 immediate problems though: 1. you don't know when the fuel is exhausted or if you can reuse it in the future so you stockpile it; 2. the contamination is much worse than the local radioactivity, so it's hard to manage correctly.