Appeal To Ignorance
Assertions based on what we do NOT know: "No one knows precisely what would happen if a core was to melt down." And the compounding of arbitrarily asserted possibilities.
What COULD happen is what is possible. The burden of proof is on the skeptic to provide some specific reason to doubt a conclusion that all available evidence supports. It is not true that "coulds" and "maybes" are an epistemological free lunch that can be asserted gratuitously. The case against the skeptic is that doubt must always be specific, and can only exist in contrast to things which cannot properly be doubted.