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.