Earlier on the reactor floor.
Jake had no trouble getting down there. The humongous Hunter he had just frozen to death had made his way up to his floor, leaving a ridiculously large hole in his wake. While the chamber containing the radioactive fusion material was still holding together, its temperature had already reached a critical level.
Not to mention ending up charred, peeking at the reactor walls, even from a distance, was a sure way to end up severely irradiated. Without a special constitution, the victims would at first suffer superficial burns reminiscent of a sunburn. But deep down, the DNA of their cells would already have been irreversibly damaged. Their organs would eventually rot and then liquefy as their vital functions deteriorated.