The SL-1 Incident
America’s First Nuclear Accident
At 21.01 on the frigid evening of January 3rd 1961, in a small fire station located in Idaho Falls, Idaho, an alarm sounds; two long bursts followed by a short. The signal for an issue at the Stationary Low-Power reactor number 1, or simply SL-1, the fire crew attended with haste, but without much fear; this would be the third call out to the station on this day alone, the previous two call outs being false alarms. Getting to the reactor by 21:10.
The Reactor That Shouldn’t Have Failed
The SL-1 reactor was designed to act as a self-contained power station for use in harsh Arctic environments where the USA had set up secret listening stations to eavesdrop on radio chatter from the Russians, environments where using diesel fuel generators was either uneconomical, impractical or both. The SL-1 was far from the most glamorous and exciting of projects that had been conceived of at the labs in Idaho; with that honour going to the projects to get a nuclear powered plane in the sky, which could theoretically remain airborne indefinitely or the race to build the world’s first nuclear submarine, a race that the USA won in August 1958 when the nuclear powered USS Nautilus became the first craft to circumvent under the north pole
When the fire crew pulled up outside the 50-foot-tall silo like building, clad in sheet metal that housed the miniaturised reactor, nothing seemed out of the ordinary, except maybe some easily overlooked steam escaping from the roof. The fire crew entered the common area that the crew shared and found mugs of coffee still hot on the table, but not a sight nor sound of the three-man crew.
Three Men Inside
The crew consisted of Jack Byrnes (22), Richard McKinley (26) and Richard Legg (26). All three men were known to partake in rambunctious and booze fuelled parties with sex workers. Jack Byrnes was known to be a hot-headed young man who had been in a drunken brawl with Richard Legg, who was known to set off alarms just to startle his co-workers.
With no sign of the three men, the fire crew assumed that they must be in the reactor so started up the stair case to enter the reactor building when there radiological hazard detectors triggered and started to show impossibly high readings – More than 500 roentgen per hour – a dose that would see the men absorb the maximum recommended dose over the course of a year in just two minutes.
Clearly, something was wrong. heading back to the truck to get the backup detector, it showed the same results. Driven by the knowledge that if there were casualties inside the reactor building, that time would be of the essence, the fire crew climbed the way to the door to the reactor room, ignoring the clicks and alarms coming from their equipment, and they looked through the window in the door.
The reactor had gone.
Too Late
Somehow, the small nuclear reactor housed in the main building of SL-1 had utterly destroyed itself and killed Jack Byrnes and Richard Legg instantly; Richard McKinley survived the initial blast, and was lying mortally wounded, missing one of his hands and a large portion of his face. He was soaked to the skin in highly radioactive water. It would be half an hour before the rescue team could recover the man who died of his wounds in the ambulance on the way to the hospital at around 23:00.
There was a problem for the recovery team, however, the mangled remains of Jack Byrnes were barely identifiable but present, and McKinley was in the ambulance that left Richard Legg, who seemed to have vanished into thin air, until one of the rescue team looked up.
The control rods had been ejected from the reactor with such astounding force that two of them had struck him and literally nailed him to the ceiling by his pelvis and abdomen. It took days to remove the remains of Jack Byrnes, with crews working in minute-long shifts to minimise radiological exposure. It would take a lot longer, and the application of a stretcher on a crane to free the highly contaminated remains of Richard Legg.
Buried in Lead
The remains of the men were so highly irradiated and thought to be so toxic that the army took extreme measures in their burials. The mortal remains of the men had most of their skin and internal organs removed and were wrapped like mummies in strips of lead coated linin and plastic, the bodies were then sealed inside lead lined metal coffins, buried at a depth of 10 feet, with the casket having successive layers of foot thick concrete and earth. One can only imagine what some archaeologist would make of these thousands of years in the future. Even in this far-flung hypothetical future, the bodies would probably still be radioactive enough to pose a danger to the future scientist.
What caused the reactor to explode and take the lives of these three men? What cataclysmic, massive error occurred to cause the reactor to go ‘prompt critical’ and self-destruct in a fraction of the time it takes to blink an eye? To answer this fully, it is necessary to know a little about how a reactor works and what makes the control rods such a vital part of the contraption.
How a Nuclear Reactor Works (and Fails)
Nuclear physics is legendarily difficult to understand; however, how a reactor generates power is actually pretty straightforward. It all comes down to heat and water.
Nuclear materials, such as enriched uranium, emit particles called neutrons as they decay. These free neutrons can hit each other and impart a tiny amount of energy as heat. This is called fission. (When a heavy nucleus, the positively charged central core of an atom, consisting of protons and neutrons and containing nearly all its mass, splits after colliding) if you cram a lot of nuclear material together, this radioactive decay will heat up other radioactive material, causing it to heat up and shoot out more materials. This is known as going critical. This critical mass will now escalate on its own and create a chain reaction.
What stops this runaway chain reaction is simply the introduction of other materials to control the reaction; these so-called control rods simply absorb these particles. Control rods can be made of boron, indium, cadmium or even silver. In the case of the SL-1, these control rods were made of boron. If anything were to go wrong with a reactor, the chances are that it would be a control rod issue at the heart of the matter.
The control rods are inserted into the reactor to regulate the temperature, which then boils the water in the reactor, and then this steam is converted to electricity by the use of a turbine.
There are two types of neutrons, fast neutrons and slow neutrons. For the purposes of a reactor, fast neutrons are actually worse than slow neutrons. This is one of the ways that simple water comes into the picture. water is very dense and can be used as a moderator to slow down the particles and help continue the heat production process. Also, water can be used as a failsafe; if you heat water too much, it becomes steam, meaning that there are now voids and the water is less dense, this means that there are too many fast neutrons, decreasing the number of fissions and leading to a cooler reactor.
One major design flaw with the SL-1 reactor is that one control rod was powerful enough on its own to take the reactor all the way from cool to critical.
With control rods, very small distances can produce radically varied temperatures, in the case of SL-1 Richard Legg had been tasked with raising the seven foot long 100lb rod of boron up by four inches, by hand, to reconnect it to the mechanism that would regulate the temperature in the core much more accurately.
There was, however, one small problem: the control rod, powerful enough to kick-start the entire reactor from dormant to full operating capacity and beyond, got stuck. This was not a unique situation; between February of 1959 and December of 1960, these rods malfunctioned on 63 separate occasions. The army’s response? Exercise the rods, by which they meant lift them up and down so that they wouldn’t get stuck. In the event of a stuck rod, the judicious use of a blunt force in the form of a pipe wrench was recommended. The reactor had been cold since the station was closed for the Christmas holidays from December 23rd 1960, and tasked with firing the reactor back up. Byrnes pulled on the control rod.
Accident, Sabotage… or Just Bad Luck?
What happened next is a matter of record; the rod instead of being moved four inches was pulled up 20 inches, this led the reactor to go from dormant to well above standard operating capacity in four milliseconds, (for context the time it takes to blink is around 100ms) this caused the water to flash boil and sent the control rods out of the reactor with the force of 500 PSI, in what is known as a water hammer effect, the rods ejected out of the core at approximately 85 feet per second and impaled the unfortunate Richard Legg, killing him instantly. The force of the reaction was so strong that it lifted the entire reactor structure, weighing around 26,000 pounds, nine feet out of its housing before coming to rest again in its housing.
The reason why it happened is a matter of much speculation; it is known that the last contact the station had with the outside world was at around 19:00 when Byrnes received a phone call from his wife, with whom he had been having difficulties, his wife asked him for a divorce and these events must certainly have been playing on Byrnes mind, as certainly was the fact that Legg, who was his superior officer and with whom he shared no little animosity was—judging on the positions of the bodies—quite literally breathing down his neck when he was performing the delicate operation. It would have been easy for Byrnes, in a fit of rage, to have deliberately extracted the rod too far in an ostentatious act of murder suicide.
However, this is unlikely; the leaked memos detailing Legg’s affair with Byrnes’s wife have been thoroughly discredited. And it seems as if the SL-1 accident was just that, a terrible accident that was the result of an ageing reactor, poor design and sheer bad luck.
The events of 3rd January 1961 led to changes in reactor designs; no longer would one rod be powerful enough to completely start the reactor, and moving the rods by hand was completely abolished.
Three men buried in concrete tombs, sealed away like radioactive mummies, guarded by time and thick layers of earth. And all because of a stuck rod and a terrible design flaw. If there are ghosts, I can’t imagine they’re happy.
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