[Spoiler]
Hey all fan of these Wikia's and wanted to comment on Nuclear Man Prime Earth page. Tho his only appeared in the one issue and I hope that it's not the last time, there isn't a lot of info on him yet. But what is is that this Nuclear Man was created by the House of El (maybe way his wearing their cap) and hadn't met Superman yet, it seems to me that he had been in the Phantom Zone for some time? Like Zaar said this is where Krypton threw away their terrible secrets.
That given there's no sun nor anything similar for him to feed on, I think he was using what energy he had saved up to move around and well he looked to me with those things on his skin ill or weakened but still strong enough to put up a fight.