U.S. NRC Blog

Transparent, Participate, and Collaborate

Putting the Axe to the ‘Scram’ Myth

The NRC glossary defines a “scram” as “the sudden shutting down of a nuclear reactor usually by rapid insertion of control rods.” But where did the word come from? One deeply engrained legend about the origin of the word dates to the first sustained chain reaction on December 2, 1942, at the Chicago Pile (CP-1), the first atomic reactor developed for the Manhattan Project. According to the legend, Enrico Fermi created the acronym, Safety Control Rod Axe Man, for Norman Hilberry. It was Hilberry’s assignment that day to kill a possible runaway reaction by using an axe to cut a rope to allow the backup safety control rod to drop into the pile.

The axe-man story now has a life of its own. A search on Google for “scram” and “axe” yields 124,000 hits. Even the NRC’s glossary attributes scram’s etymology to the axe man story. Eleven years ago, Oak Ridge National Laboratories reported a fanciful variation of this story where Fermi, presumably unimpressed with the physical prowess of his fellow physicists, recruited a lumberjack from the Pacific Northwest to do the job. That version has now spread on the internet, and the acronym itself has mutated into Super-Critical Reactor Axe Man and Start Cutting Right Away, Man.

Hilberry, as it turns out, only learned the story second-hand years later, which lends doubt to the axe-man version, and Hilberry’s own recollection of the event didn’t accord with the memories of several other participants. Leona Marshall Libby, the only female physicist present that day, wrote in her memoir that it was Volney “Bill” Wilson who called the safety rods “scram rods.” She didn’t explain why, but her crediting the term’s invention to Wilson was supported by others involved in CP-1, including Warren Nyer.

I contacted Nyer recently, and he was eager to tell the “scram” story, one that squares well with Wilson’s reported version of events. Nyer’s job that day was to be Hilberry’s backup. If all safety systems failed, he and the other members of the “suicide squad” were to dump a liquid cadmium solution on CP-1 to poison the reaction. The axe-man story is, he recalls, “a bunch of baloney.” But he did offer another explanation for the word. His recollection was that Wilson was assembling a panel that included a big red button. According to Nyer, someone asked Wilson the reason for the red knob. Wilson replied you’d hit it if there was a problem. “Well, then what do you do?” he was asked. Wilson reportedly replied “You scram … out of here.” The word appears to have stuck.

And so it seems likely that scram switches all over the world owe their names not to the nuclear industry’s later penchant for acronyms, but to the slang of twentieth-century America.

Tom Wellock
NRC Historian

15 responses to “Putting the Axe to the ‘Scram’ Myth

  1. Anonymous January 4, 2014 at 9:26 am

    So if Nyer was the backup man, instead of ATWS, we should call it NYER.

  2. Daniel J. Robbins January 3, 2014 at 9:28 pm

    Let me see if I understand the debunking correctly.

    It is undisputed that Dr. Hiberry was present and part of the project. It is undisputed that “SCRAM” was used in reference to an emergency shut down of Chicago Pile No. 1. Wilson and Nyer each state that they were assisting Dr. Hiberry by backing him up as a “suicide team” to dump a solution of cadmium on the pile in the event of an emergency. What was Dr. Hiberry doing that they were “backing up” if he was not wielding an axe to cut the rope holding the cruciform cadmium emergency rope.

    It may have been a back fit of the term to Dr. Hiberry’s personal role. Maybe it was a conglomeration of the two: “What do we do if Dr. Fermi tells Dr. Hilberry to cut the rope?” and Mr. Wilson (or someone else) says “Scram!” Then the acronym comes later. Or, Dr. Hilberry and Dr. Fermi in discussing a title for Dr. Hilberry’s role, taking place as part of an acronym crazy government bureaucracy (The Manhattan Engineering District) came up with the acronym first.

    I do not know which is the real truth. I don’t think we can ever prove it one way or the other. I am biased having earned my degree in nuclear engineering when Dr. Hilberry was our beloved old hand, the professor emeritus who had been part of the Manhattan Project. I am also well acquainted with the government’s love of acronyms (25 years active duty Air Force and continuing duty as a civilian and volunteer). That being said, I think that Hilberry’s description of the etymology of “SCRAM” is at least as credible as Wilson and Nyer’s, and it has priority.

    It is quite right to provide possible alternatives and to credit Misters Wilson and Nyer. I do think it is a slur against Dr. Hilberry to suggest that his story should be disregarded after he is gone and unable to defend himself.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s


Get every new post delivered to your Inbox.

Join 1,349 other followers

%d bloggers like this: