National Geographic : 1962 Aug
Man-made rat's nest of pipes, tubing, and electric cables controls the reactor. To ensure trouble-free operation, workmen set up the sys tem for tests, dismantled it for cleaning, and then rebuilt it. Here an inspector squeezes into the support structure. Phalanx of shafts lifts or lowers control rods in the reactor chamber below. Pulling the cross shaped rods out of the core steps up the chain reaction; pushing them in shuts it off. An elec tric motor and hydraulic unit drive each shaft. SCRAM button shuts down the reactor in less than a second by ramming in the control rods. Operators push this switch only in an emer gency. Scientists trace their use of the word to the early days of the atomic industry, when they had orders to clear out-scram-in case of a nuclear mishap. KODACHROME(UPPER) AND HS EKTACHROMESBY NATIONAL GEOGRAPHIC PHOTOGRAPHERJOHN E. FLETCHER© N.G .S .