If you stack spent fuel bad things occur. And no, I don't agree. The volume and mass of PV panels in the world is already negligible and making the waste stream

If you stack spent fuel bad things occur. And no, I don't agree. The volume and mass of PV panels in the world is already negligible and making the waste stream smaller is not important or relevant to anyone. Even in an extreme case nobody would pursue, it doesn't take any space. In a sane case it is a high quality silicon feedstock.