First there's the scram system, it automatically ejects the control rods into the core and shuts the plant down.
1928, U.S. slang, either a shortened form of scramble (v.) or from German schramm, imperative singular of schrammen "depart." Related: Scrammed; scramming.
: I got ready for a sudden scram
To leave quickly; flee; beat it: Customers scrammed screaming when the trailer went on/ Scram, you kids (1928+)