Can the radioactive material from a nuclear energy plant be used in an atomic bomb?
Basically, NO. The spent fuel from a conventional water-cooled power plant reactor does not contain uranium of sufficient enrichment to make a weapon. The small amount of plutonium in a used fuel rod cannot be used because of its isotopic mixture. To make a uranium-based weapon, centrifuges are used for enrichment. To make a plutonium-based weapon, special defense department reactors are used to ensure that the plutonium is almost entirely plutonium-239. The plutonium-239 in a used fuel rod is mixed with plutonium-240 which makes the mixture useless for a weapon and impossible to separate.
In addition, the more radioactive fission products present in used fuel rods make them deadly to handle without special, heavy, shielded equipment, and spent fuel storage facilities are heavily secured. If someone were to somehow obtain some of this material it would take an elaborate facility to separate the materials for extraction of uranium or plutonium. The idea of a rogue terrorist stealing any of this material to make a bomb is preposterous.