Terrorists willing to blow themselves up at a time of their choosing is the key there. With nuclear waste hot enough to be a menace, the window between getting

Terrorists willing to blow themselves up at a time of their choosing is the key there. With nuclear waste hot enough to be a menace, the window between getting the material and being painfully incapacitated and/or dead by the material is pretty damn small. Especially since nuclear plants tend to have things like lots of checkpoints and security.