Friday, November 18, 2011


SCRAM.    Do I mean “scat” or “go away”?   No, I mean the acronym which stands for Safety Control Rod Axe Man (S.C.R.A.M.).  
In modern terms it means to immediately shut down a nuclear reactor by “dropping” the control rods into the reactor to shut down the nuclear reaction.   A SCRAM is usually only done during times of emergency or unusual occurrences.   This is done by hitting the "SCRAM" button on the control panel of the reactor.   But what a funny sounding acronym "SCRAM" is.  
What on earth is a Safety Control Rod Axe Man?   Well, here he is, Norman Hillberry.  
One of the scientists of the Manhattan Project in the development of the atomic bomb during World War II.   During the war a nuclear reactor was built on the campus of the University of Chicago to see if a chain reaction of uranium was possible.   This was headed by Enrico Fermi.
This reactor would be controlled by a series of control rods being either pulled out of the reactor or pushed into the reactor.   To go faster, you pull the rods out.  To go slower, you push the rods in.  To stop, you push the rods all the way in.   Some of the rods were motor driven, some were moved by hand, while others were suspended above the reactor held by a rope and if the rope were cut they would drop into the reactor under their own weight.   The rope was attached to a railing on a balcony overlooking the reactor.    This is where Norman Hillberry came in.   When the reactor was started for the very first time, he was given an axe and stood by the rope tied to the railing.  
Can you see him?   He is at the railing and bent over in this painting.
In an emergency he was to cut the rope and the control rods would be pulled into the reactor shutting it down.   Primitive but effective.   I got to meet Norman Hillberry on a number of occasions when I worked for the Arizona Atomic Energy Commission and attended the monthly dinner meetings of the Arizona Chapter of the American Nuclear Society.   He would tell stories of the early days of nuclear energy including how the acronym SCRAM came about.   A very interesting fellow and a pleasure to listen to.  So the next time you hear about a nuclear reactor being “scrammed” you will know the origins of the term.   Have a great day wherever you may be.    Lew 

1 comment:

Barry R. Bainton, PhD, MBA said...


I met Norman back in 1979 when I enrolled in his Research Administration seminar at the University of Arizona. It was the time of Three Mile Island and the American Atomics incident in Tucson. Norman was a very interesting and impressive individual.
I was finishing my dissertation in Anthropology and needed to be enrolled in a course to be "in residence". I found his course by accident and he was kind enough to let me enroll. I found him to be a natural "anthropologist" as well as a nuclear engineer.