Another ex-Navy nuke here. When I went through nuclear power school (the West Coast one at Mare Island) in the 1970s, the version we heard was "Safety Control Rod Axe Man."
Was there really a rope, and you really cut it with an axe?
What did this do to the life expectancy of the ax operator?
Does any of this have anything to do with your HN username? If there's a story, would you tell?
There was a backup to the backup: people with a solution of something (borate?) to pour into the pile to soak up surplus neutrons. This was a really bad thing to do, for the future use of the pile: the carbon would be soaked, useless, the reactivity of the pile would be next to impossible to get back without completely re-constructing it so the Scram by lowering rods, was the preference, and was done by a counter for accellerated scaling aside from the guy with the axe after a while.
https://patents.google.com/patent/US3721462A/en https://patents.google.com/patent/US8811561B2/en
For my username: I actually started using this name before I was involved in nuclear power, and that’s the first time that’s been asked!
The acronym/story we were told regarding SCRAM was “Super Critical Reactor Axe Man”; as in the guy who would cut the rope to drop the control devices into the fission pile if they detected its reactivity going TOO super critical.
Interestingly this usage doesn’t seem well known outside of those circles. It is/was, however, directly printed in rather old publications I used (60s perhaps?).