For the past couple of years, a young woman known only as “Bionerd23” has been making strange, dangerous videos in and around one of the most infamous nuclear zones on Earth—the Chernobyl Exclusion Zone. Nothing is too radioactive or risky for her. She has shown herself getting injected with the radionuclide technetium, eating radioactive apples from a tree in Chernobyl, being chased by a possibly rabid fox, and picking up fragments of the nuclear plant’s reactor fuel with her bare hands. When a freakishly large catfish appears on camera, she calmly explains that it’s probably not a mutant—“They are just...