Scram as the original and mostly likely accurate basis for the use of scram in the technical context. A persistent alternative explanation posits that scram is an acronym for 'safety control rod axe man', which was supposedly coined by Enrico Fermi when the world's first nuclear reactor was built under the spectator seating at the University of Chicago's Stagg Field. It could also stand for "Safety Control Rods Activation Mechanism" or "Control Rods Actuator Mechanism". Both of these are probably backronyms from the original, non-technical usage. In any reactor, a SCRAM is achieved by inserting large amounts of negative reactivity mass
Enrico Fermi down once more a few hours later. The problem was traced to neutron poisoning from xenon-135, a fission product with a half-life of 9.2 hours. DuPont had deviated from the Metallurgical Laboratory's original design in which the reactor had 1,500 tubes arranged in a circle, and had added 504 tubes to fill in the corners. The scientists had originally considered this over-engineering a waste of time and money, but Fermi realized that if all 2,004 tubes were loaded, the reactor could reach the required power level and efficiently produce plutonium. In mid-1944, Robert Oppenheimer persuaded Fermi to join his Project