Board Thread:Questions and Answers/@comment-5602817-20140610201854/@comment-8505655-20140619025725

Speaking roughly, nuclear energy is energy obtained from a nuclear process. The energy itself is not radioactive, though radiation may be present from the same process. Not unlike how one can receive energy from a nuclear power plant without necessarily getting radiation poisoning. So if we assume that Atomix either does not produce very much radiation or that he has a highly effective containment system (both of which seem possible, especially for Ben 10 physics), then it is possible to conclude that he does not present a danger of radiation poisoning. This seems especially true when one considers the flak that NRG gets for being dangerously radioactive, whereas Atomix does not.

Of course, it also merits note that Atomix has, for the most part, only channeled enough energy to cause relatively small explosions; not nearly as much as would come from an atomic bomb or from a power plant engineered to power an entire city. (The one exception being when he created a miniature sun, but that's an entirely different can of worms.)

Correct me if I'm mistaken anywhere, but I hope this helps.