So according to your logic, it must have happened first to worry about the possibility of a GAU?

Not exactly sure what a GAU is.

If an event has never happened, and the risks have been adequately mitigated, no, I don’t see the need to worry.

GAU = "Grösster Anzunehmender Unfall" roughly translates to "maximum conceivable accident", almost exclusively used for nuclear accidents (or sarcastically for lesser problems, like accidentally deleting a database without a backup at hand).

The fact that this is a very common German word should tell you something about the complicated relationship of the Germans to nuclear energy ;)

That’s simply an oversimplified view of risk, mitigation adequacy, and the dynamic and often unpredictable nature of real-world events.

By the very definition somebody already worried about the GAU. https://en.wikipedia.org/wiki/Design-basis_event https://de.wikipedia.org/wiki/Auslegungsst%C3%B6rfall