[ RadSafe ] Reactor SL-1 accident

Doug Huffman doug.huffman at wildblue.net
Thu Jun 23 07:10:50 CDT 2011

Dear Franz,  It is good to write to you and I can describe a bit of the
SL-1 accident.  I had a co-worker that worked at the SL-1 reactor and,
indeed, was assigned to do the work that caused the incident. But for
having the sniffles, he may have been present at the explosion.  He
still corresponds with me, though on social and political issues.

I learned of the official conclusions of the incident as part of my
training and, later, as part of my preparation to teach an aspect of
safety to my peers.  My co-worker confirmed the official explanation
during our safety instruction.

As I recall from thirty years ago, the SL-1 was a semi-portable, Small
and Low-powered reactor for the US Army.  I believe that one very like
it was at an Antarctic base for its full life time and removed without
notable incident.

It had few control rods, perhaps as few as three or four.  Planned
maintenance had been completed and the control rod drive mechanisms were
being restored.  They were of a rack and pinion design.  During the
maintenance the rack had been disconnected from the pinion drive gear
and the rods rested on mechanical stops.  They each weighed some tens of

The central rod provided most of the shut down reactivity and was the
first to be engaged with its drive mechanism.  The worker evidently
squatted over the rod's pinion and lifted it too quickly and too great a
distance; tens of centimeters in less than a second.  The manual
engagement was by an approved procedure except for the unknown details
that allowed and caused the jerk.

The brief high power excursion, perhaps a prompt criticality, caused a
steam explosion that disassembled the reactor and reactor vessel, its
contents and the reactor head.  A significant piece of evidence was the
worker's body found pinned to the enclosure's ceiling by the control rod
stuck through his body and into the structure.

The structure and the corpses were highly radioactive.  The structure
was disassembled and buried on site.  The corpses were recovered intact
and were buried with the structure.  The burial site was paved for
control of loose contamination.  It has been called a "parking lot" and
legend has it that snow melts quickly.  Of course the radiation levels
are probably too high for uncontrolled access.

These are my recollections of the SL-1 accident, gathered from my
training and preparation for peer-training and confirmed by a co-worker
that had been assigned the work.

Doug Huffman
Washington Island

On 6/21/2011 15:41, franz.schoenhofer at chello.at wrote:
> Roy,
> You mentioned in your post the SL-1 accident.. I was in highschool then, not really being to much interested in such news, but I do not remember that I ever heard or read anything about it until about the early eighties when we loaned at my Austrian ministry.films from the IAEA about nuclear explosions and also about the SL-1 accident. Since I had in the course of my work at that ministry   to deal with nuclear accidents I got a little deeper in the story, but I never ever read about any hints of sabotage. We unfortunately have now any number of suicide bombers, but at that time and at that accident I cannot believe that any fools (sorry, I cannot think of any other word) would have deliberately infiltrated the SL-1 crew, deliberrately drawn out the control rods by their bare hands to cause an explosion, which caused the death of three (!!!) persons - in present cynical speak a negligible "efficiency". 
> Could you explain more about this "sabotage"? 
> Best regards, 
> Franz
> ---- ROY HERREN <royherren2005 at yahoo.com> schrieb:
>> How about the SL-1 accident, see 
>> http://www.radiationworks.com/sl1reactor.htm?   "3 January 1961: A reactor 
>> explosion (attributed by a Nuclear Regulatory Commission source to sabotage) at 
>> the National Reactor Testing Station in Idaho Falls, Idaho, killed one navy 
>> technician and two army technicians, and released radioactivity "largely 
>> confined" (words of John A. McCone, Director of the Atomic Energy Commission) to 
>> the reactor building.  The three men were killed as they moved fuel rods in a 
>> "routine" preparation for the reactor start-up. One technician was blown to the 
>> ceiling of the containment dome and impaled on a control rod. His body remained 
>> there until it was taken down six days later. The men were so heavily exposed to 
>> radiation that their hands had to be buried separately with other radioactive 
>> waste, and their bodies were interred in lead coffins."
>>  Roy Herren 
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