Scram

thumb|SCRAM button at the Experimental Breeder Reactor I|Experimental Breeder Reactor I in Idaho. Sometimes the switch will have a flip cover to prevent inadvertent operation.

A scram or SCRAM is an emergency shutdown of a nuclear reactor effected by 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 and a "reactor trip" at pressurized water reactors. In many cases, a scram is part of the routine shutdown procedure which serves to test the emergency shutdown system.