Following World War II, the United States military expended great efforts to harness the power of the atom. Military planners were enamored with the promise of cheap, long-term power offered by a nuclear reactor, and efforts were in full swing in the 1950’s to develop nuclear reactors to support the military.

Before satellites were available to monitor for impending attack, radar stations were placed in locations that were thought most likely routes for Soviet nuclear missiles. The Distance Early Warning (DEW) line was a line of radar outposts across the arctic in Alaska and Canada, where radar operators would watch 24 hours a day, 7 days a week for incoming ballistic missiles. These outposts were maintained by regularly flying fuel and supplies in to the outposts to generate electricity and heat. Perhaps it goes without saying that this was very expensive, and the U.S. military was very interested in a cheaper alternative, and so looked to nuclear reactors. A series of reactors were envisioned, some mobile (to be identified as M-type reactors), some stationary (designated as S-type), at a variety of power levels (L for low, M for medium, H for high).

One of the first of these reactors to be developed was the SL-1 reactor (S for stationary, L for low-power, and 1 because it was the first of this type). The intended purpose of this particular reactor was to provide heat and electricity to radar monitoring stations along the DEW line. The reactors were designed to take advantage of local materials for shielding where possible, and were also designed such that the pieces when disassembled could be easily transported to the location where they would be set up and operated. This meant that the large concrete structures used to safely contain modern reactor vessels would have been too heavy and costly to build, and so a simple steel building was erected to protect the reactor components from the elements. The hope was that soldiers with a minimal amount of training would be able to operate and maintain these reactors with a minimum amount of support, enabling them to be operational for up to three years without refueling.

The SL-1 reactor design was flawed in many ways. As an example, thin boron sheets were attached to the outside of the control rod blades to provide better control of the fission process in the reactor. In the core of the reactor, Boron is converted into Carbon 14, and this tended to cause the boron sheets to deform and eventually flake off, causing the control rods to stick and hang up periodically in the reactor core. Another more fundamental design flaw was the ability for the reactor to achieve criticality with the actuation of only one of the control rods. Criticality in a reactor is the condition where it supports a sustained nuclear fission reaction and can generate power. On the SL-1 reactor, if the central control rod were withdrawn, criticality could be achieved, even with the other control rods fully inserted. As a result of this reactor accident, modern reactors are required to be designed in such a way that the withdrawal of any single control rod cannot cause the reactor to become critical.

The SL-1 reactor went critical (i.e. caused sustained nuclear fission for the first time) in August of 1958, and was then used to produce power, and to train reactor operators. Soldiers who wished to become reactor operators were given 9 months of initial training in Fort Belvoir, Virginia, before heading to the desert in eastern Idaho for an additional 6 weeks of classroom training, before training with a senior reactor operator crew operating the SL-1 reactor. The reactor was operated by a crew of 2-3 people, and maintenance was typically conducted by the same two to three-man reactor crew, in keeping with the goal of the reactor development program to have a reactor that could be operated and maintained with minimal support in a remote area. During the day shift in Idaho, a health physicist was typically also on hand to monitor the radiation exposure of the crew.

On December 23, 1960 the SL-1 reactor was shut down in preparation for the Christmas holiday, after which crews began to conduct scheduled maintenance to prepare the reactor to resume normal operation. On January 3rd, 1961 the night shift took over the maintenance operations on the reactor from the day shift. This included two Army men, John A. “Jack” Byrnes, the Senior Reactor Operator, and Richard L. McKinley, a trainee, and a Navy man, Richard C. “Dick” Legg, the Assistant Operator and shift supervisor.

For the most part, the men on the shift were competent and unremarkable among the other trainee reactor operators in their class. Several interesting things emerged after the accident in relation to the men involved, however. Jack Byrnes, for example, worked part time at a gas station, filling cars with gas, topping up tires and cleaning windows. While Byrnes didn’t invent the side-hustle, this has to be one of the more interesting pairings of all time, Nuclear Reactor Operator by day, Pump Jockey by night. Byrnes was also having some sort of marital trouble, and it is known that Byrnes wife called the reactor building a few times the night of the accident, although whether this played into the events on the night of the accident is unknown, as is the substance of their discussion.

After the accident, it also came to light that Dick Legg was known as a prankster. Among his many pranks, he reportedly once turned off a fan used to cool specific reactor instruments, causing the system to alarm. After nearly sending everyone on the shift into a panic, Legg coolly reached around the back of the control panel and switched the fan back on. These were the men preparing the reactor for operation the night of January 3rd, 1961.

Part of the maintenance conducted during the shut-down of the reactor required that the control rods be disconnected from the control rod drive mechanisms. Under normal operations, these mechanisms would lift and lower the control rods to increase or decrease the power output of the nuclear reactor core, which would in turn cause more or less steam to be generated. This steam would then power turbine generators for electrical power, and heat for the reactor building. On the night of January 3, 1961 the men were working to reattach the control rods to the drive mechanisms. When the central control rod was disconnected, a C-clamp was attached at the level of the floor above the reactor to support the weight of the control rod while the control rod drive mechanism was disconnected. To reconnect it, one man had to lift the roughly 85 lb control rod off the supporting C-clamp so another man could remove the clamp. To enable the control rod to be lifted, a handle was attached in the place of the control rod drive mechanism. At 9:01pm on the night of January 3rd, 1961 Jack Byrnes was lifting the control rod. Dick Legg was crouching next to him, ready to remove the C-clamp, and Richard McKinnley was standing a short distance away, holding a Cutie Pie radiation instrument to monitor radiation exposure levels.

The procedure called for the control rod to be lifted no more than 2 inches to disconnect the clamp. Subsequent investigation has shown that the control rod was lifted 20 inches or more out of the core. This caused the power level in the reactor core to rise extremely quickly (a condition referred to as “prompt criticality”), and within fractions of a second much of the fuel had melted, and a large amount of steam was formed. This steam explosion then caused the large layer of cooler water above the reactor core it to accelerate upwards and slam into the underside of the reactor vessel head. The reactor vessel then jumped, shearing all the piping and instrumentation connected to it, dislodging shield blocks, and eventually hitting the ceiling of the reactor building. All three men died as a result of the accident, it is believed that Byrnes and Legg died immediately, and McKinnley may have survived until shortly after he was recovered from the reactor building, and is thought to have died in the ambulance within hours of the accident, although this is not clear. At any rate, he never regained consciousness. The three men were the only witnesses to what actually caused the accident.

This left everyone wondering what could have caused Byrnes to pull the central control rod so far out. Initially there was some concern that this may have happened out of ignorance to the danger of pulling the central control rod, however investigation found that the reactor operators had conversations where they discussed that in the event of an advancing Soviet army they would likely just go pull the central control rod to blow up the reactor, so it is unlikely, although not impossible that the men were ignorant of this danger. Speculation ranged far and wide as to the cause of the accident, from a stuck control rod, to showing off, to horseplay, and even included a theory that this was a murder-suicide.

In the aftermath of the accident, the U.S. government made a considerable effort to understand what had happened. One of the more amusing, although tragic, theories was related to Dick Legg’s penchant for horseplay and pranks. Someone (the real hero of this story) theorized that perhaps as Byrnes began to lift the control rod, Legg may have “goosed” him, causing him to jerk the control rod upwards in surprise. Let’s call this the “Atomic Goosing” theory. A less thorough investigating team may have dismissed this as a remote possibility that warranted no further thought, but I think we are all grateful to know that the investigators in this case were VERY thorough.

The investigating team built a mock-up of the top of the reactor, complete with properly weighted control rods. Subjects and researchers took turns pulling up on the control rod to first determine if it was physically possible for a person to pull the rod fast enough to cause the prompt criticality condition. After determining that it was indeed possible, they then attempted to test “atomic goosing” theory. For the uninitiated, Merriam-Webster defines this type of goose as “to touch or pinch (someone) on the buttocks”.

If you think through what the goal of the testing is, a few things become clear. First, the subject who is lifting the rod can’t be expecting the goose. You can’t be surprised by a goose if you know it’s coming. This seems to imply that the subjects likely didn’t consent to the goosing beforehand. One can only speculate on what the subjects were told, and how things were explained afterwards (“Woah, calm down, Joe. That was an EXPERIMENTAL goose.”). Second, the nature of the goosing could play a role in the response of the subject to said stimulus. Given this, we can only assume that somewhere deep buried in the government archives there exists a procedure for delivering the appropriate goose, perhaps with diagrams, maybe a step-by-step process, perhaps even calibration jigs, and necessary training to perform the correct goose. Even if such a document doesn’t exist, we can all rest comfortably with the assurance that U.S. tax dollars were once used to goose people for SCIENCE!

What we actually know of this testing is largely from interviews with C. Wayne Bills, who was the deputy director of health and safety at the Idaho site at the time of the accident. He describes the subsequent testing as including a sudden release of the rod while someone pulled it up (simulating the stuck rod condition), as well as someone sneaking up behind the person lifting the rod, and poking them in their sensitive areas. He notes that none of the tests caused those doing the lifting to inadvertently pull the central control rod more than a few inches, let alone the 20 or more that lead to the accident. The official conclusions of the investigative team were that we don’t know what lead to Byrnes pulling the control rod out of the core.

In the aftermath of the accident, it was necessary to properly dispose of the now destroyed and highly contaminated reactor and components. In keeping with the mindset of the ‘50’s and early ‘60’s, they made this a problem for future generations. Much of the contaminated reactor building and components were buried in the desert in eastern Idaho, not far from where the reactor was constructed and operated.

The bodies of the three men were unfortunately extremely radioactive following the accident. This was largely due to small particles of radioactive materials that became embedded under the skin and elsewhere in the men’s bodies as a result of the steam explosion and melted nuclear fuel. With radioactive materials embedded in their bodies, it was not possible to wash it off, and so autopsies had to be conducted from behind thick lead walls using makeshift tools attached to the end of 10 foot long handles. Afterwards, caskets had to be brought to the desert site machine shops and lined with lead prior to the funerals to protect mourners from receiving high radiation doses.

Whether you are for or against nuclear power, it has to be recognized that this accident, while tragic, played a part in the safety of modern nuclear reactors, and perhaps we can all smile at the time that the U.S. government goosed people for science.

Bonus Fact:

There wasn’t actually any marketing firm behind the name of the Cutie Pie handheld radiation detector, even though it sounds like exactly the sort of radiation monitor used by the “My Little Ponies”, or perhaps something that would come in a “Strawberry Shortcake” nuclear reactor play set. It turns out the name was given to this type of meter in a now declassified Atomic Energy Commission paper from September 22, 1945, near the end of the Manhattan Project. This paper details the construction of the “Cutie Pie” radiation detector. In that document, the device is described as containing a circuit that was as simple as possible, yet sensitive for radiation work. It also states that they named it “Cutie Pie” “because of its diminutive size”. Perhaps the proper way to hold it at fancy tea parties or high class nuclear reactor functions was with the pinky extended, although no mention of this appears in the AEC paper.

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