page_title: Scram
hierarchical_section_title: Scram
caption_attribution_description: Visit to the Experimental Breeder Reactor No. 1 (EBR-I) Atomic Museum. This was where the first generation of usable electricity by nuclear power was done back in 1951.
context_page_description: A scram or SCRAM, also known as AZ-5, is an emergency shutdown of a nuclear reactor effected by immediately terminating the fission reaction. It is also the name that is given to the manually operated kill switch that initiates the shutdown. In commercial reactor operations, this type of shutdown is often referred to as a "SCRAM" at boiling water reactors, a "reactor trip" at pressurized water reactors and EPIS at a CANDU reactor. In many cases, a SCRAM is part of the routine shutdown procedure, which serves to test the emergency shutdown system.
  The etymology of the term is a matter of debate. United States Nuclear Regulatory Commission historian Tom Wellock notes that scram is English-language slang for leaving quickly and urgently, and cites this as the original and mostly likely accurate basis for the use of scram in the technical context.
context_section_description: A scram or SCRAM, also known as AZ-5 (Russian: АЗ-5), is an emergency shutdown of a nuclear reactor effected by immediately terminating the fission reaction. It is also the name that is given to the manually operated kill switch that initiates the shutdown. In commercial reactor operations, this type of shutdown is often referred to as a "SCRAM" at boiling water reactors (BWR), a "reactor trip" at pressurized water reactors (PWR) and EPIS at a CANDU reactor.  In many cases, a SCRAM is part of the routine shutdown procedure, which serves to test the emergency shutdown system.
  The etymology of the term is a matter of debate. United States Nuclear Regulatory Commission historian Tom Wellock notes that scram is English-language slang for leaving quickly and urgently, and cites this 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, which had an actual control rod tied to a rope, with a man with an axe standing next to it. It could also stand for "Safety Control Rods Activation Mechanism" or "Safety Control Rod Actuator Mechanism". Both of these are probably backronyms from the original, non-technical usage.
  The Russian name, AZ-5 (АЗ-5, in Cyrillic), derives from Аварийная Защита 5-й категории (Avariynaya Zashchita 5-y kategorii), 'Emergency Protection of the 5th Category'.
caption: SCRAM button at the Experimental Breeder Reactor I in Idaho, USA. Sometimes the switch will have a flip cover to prevent inadvertent operation
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