Welcome to Stuff You Missed in History Class, a production of iHeartRadio. Hello, and welcome to the podcast. I'm Tracy B. Wilson and I'm Holly Frye. A few weeks ago, some friends of mine were having a totally normal conversation about the Demon Core, specifically about Demon Core memes. We did an episode on the Demon Core in twenty twenty, and we just ran that as a Saturday Classic. But in case you missed it, this is a plutonium sphere made for use in a nuclear weapon that went on to be used in criticality experiments and it was involved in two different fatal accidents. And one of those accidents, a physicist was using a screwdriver to position a reflector so that the sphere would stay just below criticality. And if you're thinking that sounds like a bad idea, you're right. In the course of this conversation, my friend Adrian, who was the same Adrian who suggested an episode on the Demon Core, said that she would love a deep dive into the sl one reactor explosion. And that threw me for a second because I thought we had talked about it in that Demon Core episode at the end where we talked about other nuclear incidents, and in reality, the SL one got cut out of that episode because all the other nuclear accidents we were talking about in that episode it mostly involved people putting nuclear material into the wrong containers, and the SL one explosion was a whole other thing. It was the first, uh and I think only deadly nuclear reactor disaster in the United States. There have been other nuclear accidents that have have had casualties involved in fatalities involved, but this one was due to the reactor itself. So here is an early Christmas present Adrian episode is for you. The Stationary Low power Plant Number one or SL one was a small boiling water reactor built at the National Reactor Testing Station, which is now Idaho National Laboratory, about forty miles or sixty four kilometers west of Idaho Falls, Idaho. The testing station was established by the Atomic Energy Commission in nineteen forty nine to research, build, and test various nuclear reactors. Because of the nature of this work, the testing station was intentionally built in a remote area, but close enough to cities and towns that people moving to the area to work at the facility would be able to find a place to live. In the late nineteen fifties, the sl one was considered one of the least exciting reactors at the testing station. For comparison, one of the other prototypes developed there was a submarine reactor designed for the USS Nautilus, which was the Navy's first nuclear powered submarine. There was also a project going on to develop a nuclear powered jet aircraft. Both of those things sound very exciting, but the sl ones focus was all about practicality, efficiency, and reliability. It had been developed after a nineteen fifty five request by the Department of Defense for a nuclear power plant for the Defense Early Warning System, or the DO Line. The DEW Line was a chain of isolated radar stations about three thousand miles long from northwestern Alaska to southeastern Greenland, about two hundred miles north of the Arctic Circle. It's outside the scope of this episode, but the building, operation, and the eventual cleanup of the Dow Line all had and continue to have a massive impact on Inuit peoples all across this region. Its legacy for those communities has been described as mixed. The Dew Line created job opportunities, housing, and infrastructure that wouldn't have existed otherwise, but none of those were created with the needs of those communities in mind. To some extent, the same could be said of the National Reactor Testing Station, which was roughly the same distance from the Fort Hall Reservation as from Idaho Falls. This was during the Cold War, and crossing the Arctic was the most direct way for Soviet aircraft or missiles to potentially reach Canada or the United States, so the Dew Line, as that early warning name suggests, was meant to provide an early warning of such an attack. Construction on the new line had started in nineteen fifty four. With the radar stations getting power and heat from diesel generators. That meant that the military had to keep those generators supplied with fuel. The Army's criteria for a nuclear reactor to replace those generators included that it had to be built above ground with components that could be delivered to the site by cargo plane. It had to be able to withstand the extreme cold of the far North, and be reliable and easy to maintain by a small team of people. It also needed to run for at least three years without refueling. The SL one was a three megawat reactor designed for an output of two hundred kilowatts of net electricity and four hundred kilowatts of energy in the form of heat. This heat output would be important in the Arctic environment, but it was also important at the testing grounds in Idaho. On the night of the disaster, the temperature was roughly eighteen degrees below zero fahrenheit or about negative twenty eight celsius. The building the reactor was housed in was not meant to contain radiation from a meltdown or other disaster in the site because of its remote location, which would also be true for the dow line. The SL one's first five hundred hour test run started on August eleventh, nineteen fifty eight. After this test run, it was shut down for inspection, testing, maintenance, and to do various adjustments. From that point, the reactor would typically run for a period of one to six weeks, then it would be shut down again for maintenance and testing. At the same time, trainees would be going through both classroom and practical training on the reactor, and if they passed all of their various courses and assessments through this work, they could be certified as reactor operators. This all sounds fairly straightforward at least as straightforward as things can be when you're talking about an experimental nuclear reactor prototype that's also being used to train personnel, but there were a number of issues. Initially, this reactor was the responsibility of ARGON National Laboratory, but argun's role ended in early nineteen fifty nine. At that point, a civilian contractor called combat Rustan Engineering Incorporated took over, but didn't have policy and procedure manuals written. When that takeover happened, the Army, Air Force, and Navy were all sending people to be trained, and there were various rivalries and power grabs going on among the various military branches. The Atomic Energy Commission was also involved, but had a fairly hands off role in theory. Military personnel were handling the actual operation of the reactor with on site supervision through combustion engineering, but reading through all the overlapping responsibilities feels a little like looking at a company org chart where someone theoretically has one boss but also has a bunch of dotted lines to other people and departments. Like a lot of developments during the Cold War, including developments in the nuclear industry, things moved really quickly, and technologies often went into use without a lot of testing, since the Department of Defense wanted a reactor that could run for at least three years without refueling. The sl one was using burnable poisons to lower the core's reactivity when it was new. This sort of stretched out how long the fuel would last over time. These burnable poisons were strips of boron alloys that were tack welded onto the fuel assemblies. Soon, these fairly untested strips started warping in between those welds, and borons started flaking off of them and settling to the bottom of the reactor. Then there were the control rods. Nuclear reactors run on fission reactions. The fuel is an isotope whose atoms can split apart when they absorb a neutron that produces two new atoms along with heat and some more neutrons. Some of those neutrons have the right amount of energy to split more atoms, which continues the cycle. With the right number of neutrons. This leads to a self sustaining or critical reaction. With too many neutrons, the reaction can go supercritical, meaning that it starts to escalate. Control rods absorb some of the neutrons controlling the rate of the reaction. Most reactors have numerous control rods that have to be adjusted in sequence to start or stop a critical reaction. To cut down on maintenance and make it easier to operate, The sl one only had five, and one control rod could do that all by itself. This was obviously risky, but at first these five control rods seemed to work fairly well. Over time, though, they developed what was described as a stickiness and this is just what it sounds like. When the rods needed to be raised or lowered, they might get stuck. This only happened about two percent of the time, but that meant over the life of the reactor it happened about eighty time, and that is not great when we are talking about the rods that are controlling a nuclear reaction. There was also an emergency shut down procedure, or a scram, in which the rods were all supposed to drop into the reactor just by gravity. Forty six times at least one rod failed to drop and it had to be driven down using an electrical clutch. This problem happened randomly, but it also seemed to be getting worse. More than thirty of those recorded stickiness incidents happened just in November and December of nineteen sixty. This stickiness seems to have been connected to the burnable poisons in the way that they were warping between the wells. On top of that, the boron that was flaking off was affecting the reactivity of the fuel in unpredictable ways, making it hard to calculate exactly how far the rods needed to move to control the reaction. And those flakes of boron and other fore and matter were affecting the water seals around the reactor's drive shafts, which also may have contributed to the stickiness. Increasing water filtration seemed to help somewhat, and on December twentieth, nineteen sixty, technicians were ordered to quote perform a complete rod travel exercise at approximately four hours after the start of each shift, meaning to manually raise and lower each rod to try to keep it moving smoothly. The SL one incident happened two weeks after that order was given, and we'll have more after a sponsor break. On December twenty third, nineteen sixty, the SL one reactor was shut down for a holiday break, and during that shutdown procedure, three of the control rods stuck and had to be driven into the reactor. Bruz returned on December twenty seventh to start on various maintenance tasks. With the reactor still shut down. On January third, nineteen sixty one, the night shift was tasked with restarting it. The reactor was staffed around the clock in three eight hour shifts, but the facility had minimal staffing during the night, including the facility gate being left locked rather than being staffed with a security guard. Three men were on duty that night, Navy CB Richard C. Legg, known as Dick, who was the shift supervisor, Army specialist John A. Burns the third known as Jack, and Army Specialist Richard Leroy McKinley, who was a trainee. All three of these men were in their twenties. Since part of the point of this project was to build a reactor that the Army could maintain with minimal staffing in a remote area, none of them had a background in nuclear engineering. Leg was experienced in the procedure they were due, but this was the first time he was doing it as a supervisor. The US Atomic Energy Commission made a video brief after this incident that gives us step by step recreation of how technicians reconnected the reactor's rack and pinion system before restarting it. I have no background in this field, but as a layperson, it struck me as very fiddly and inexact as a way to handle the control rods in a nuclear reactor. I was not alone in this. I showed this video to Adrian and she was like, what is happening? This was a two man job. First they would lower a shield plug and then opinion gear housing and then a spring housing over the rack. Then they would insert a handling tool into the spring housing and threaded onto the rack like a screw. This handling tool was basically a rod that they could grab onto. One person would pull upward on that tool to lift the rack a few inches while the other person tightened a sea clamp onto it. Then they would lower it until it rested on that clamp, Take the handling tool off, put a retaining washer and a nut onto the rack, put the handling tool back on again, and do a second lift, this time just far enough to take the seaclamp off. This is like the seaclamp that you would see at a hardware store that you put on, you know, to hold maybe a piece of board to the table, and you screw the little thing at the bottom. Under normal circumstances, the washer and nut would have connected the rack to a drive motor, but for unclear reasons, while doing this process for the central control, rod Burns suddenly raised it more than twenty inches rather than the few inches that were required. This was also farther than the distance that would have been needed to start a critical reaction. This resulted in what was known as a prompt criticality, that is, a supercritical state that is caused only by the initial influx of neutrons into the fuel, not involving any delayed neutrons that are emitted later on in the fission process. This reaction only took about four milliseconds, so it was almost instantaneous. The power level surged to more than six thousand times the reactor's rated output. The heat vaporized the water in the reactor, which created a water hammer that blew inside the top of the reactor housing, lifting the entire thing about nine feet or two point seven meters off the ground. While this reactor was considered to be small and lightweight. It weighed twenty six thousand pounds, so this was a massive amount of energy. About twenty percent of the reactor's radioactive fuel melted, and the explosion for the fuel rods away from one another and toward the walls of the containment vessel. The other four control rods were still partly or fully inserted into the core afterward, so the steam explosion had cut off the critical reaction, but this wouldn't be clear until much later. When this happened, alarms started going off at the Atomic Energy Commission fire stations and security headquarters, about ten miles east of the reactor. A personnel radiation monitor about a mile away from the reactor also alarmed, and a patrolman reported that all the needles on this monitor were at their maximum reading and it could not be reset. There had also been two false alarms earlier in the day caused by a malfunctioning fire detector in an auxiliary building, so while the first responders did not know what was going on when they got this alarm, they wouldn't have been surprised if it was just another false alarm. When firefighters arrived, the outside of the building seemed undamaged, and apart from some steam rising above the roof, there didn't seem to be anything suspicious going on. After security arrived and unlocked the gate, they entered through the administration building with their regular fire protection gear, self contained breathing systems, and radiation detectors. They didn't know for sure how many people were inside the building, but the coats, lunch pails, and cups of coffee in the brake room suggested there might be three. But the firefighters didn't see any other sign of anyone, and no one answered when they called out or pounded on the door. Radiation alarms were going off when they got into the building, but at first the firefighter's own radiation detectors did not show levels that would keep them from performing a search. But when they got into the staircase that led up to the reactor, their radiation detectors maxed out at the highest possible reading, so suddenly that at first the firefighters wondered if they were malfunctioning. They weren't, though it was obvious that there was too much radiation for them to just go into the stairwell with the gear that they had, so they left the building and they waited for a health physicist. A health physicist is somebody whose job is to protect the safety of the people who work with radiation, as well as the safety of their environment. A health physicist arrived a little more than fifteen minutes after the initial alarm and they all went inside, but once they got to that stairway, the health physicist again had them turned back. It was determined they needed more protective gear. Not long after, two more health physicists arrived with anti contamination gear, shoe covers, additional respirators and breathing systems, as well as other equipment. By that point, the reactor room up the stairs was the only place at the facility where those three men could be even with protective gear. Radiation levels in the building were so high that the search had to be carried out in relays of only about a minute each. The health physicist kept time with a stopwatch. In addition to this strict time limit, conditions inside were difficult to navigate. Once rescuers got up the stairs and into the reactor room, the floor was wet and it was covered with debris. Some of this debris was compared to a lot of marbles, and their face masks kept fogging over. Once they got into the reactor room, firefighters spotted one man who was still breathing and another who appeared to be dead. At first, they didn't know who was who or where the third man was, but the person who was still alive was later identified as Richard McKinley, aged twenty seven. The initial priority was to try to save his life. A team of five volunteers went inside carrying a stretcher, two of them to try to remove McKinley, and the other three to see if they could figure out where the third man was. While they did do kind of a relay to remove McKinley from the scene, they still did not see any sign of the third man. McKinley was taken to an ambulance, which was then moved away from the road to keep it from contaminating the road with radiation. McKinley did not survive, though he was pronounced dead about two hours after the incident. His body contaminated the ambulance with radiation, and it also exposed the on call nurse who cared for him to a large amount of radiation. The effort to rescue McKinley had been carried out as fast as possible because he was still alive, Rescuers took more time to plan out how to remove the body that they'd seen, including sending photographers into the room for ten seconds each to document exactly where he was. It was during that process that one of the team members happened to spot the body of the third man, pinned to the ceiling by one of the reactor's shield plugs. It was eventually determined that the body on the floor was Jack Burn's age twenty two, and that the body pinned to the ceiling was Dick leg age twenty six. That determination was not made for a little while, though, They did not know what was happening at this point, so they and McKinley had all experienced catastrophic and really gruesome injuries. Even though the sl one had been built at the National Reactor Testing Station, whose purpose was to build and test experimental nuclear reactors, there was not really a plan for what to do with highly radioactive bodies after an accident. Their bodies were so heavily contaminated and the nearest morgues were far enough away that drivers would have absorbed a a fatal dose of radiation just trying to transport them there in that moment, the vehicle itself would also be contaminated, and so would the roads that it traveled on, and then so would the morgue. Ultimately, a decision was made to turn the decontamination room at the facility's on site chemical processing plant into a temporary morgue, both to store the bodies and decontaminate them as much as possible. They were transported there in the same ambulance where McKinley had died, draped in lead blankets with lead aprons draped over the back of the driver's seat. Once there, they went through decontamination as well as autopsies. During this process, the autopsy team discovered that all three men had been wrongly identified. The correct identification was based on their heights and weights and their tattoos, because their faces were unrecognizable. As the team had been figuring out what to do with these bodies, figuring out to take them to this temporary morgue, McKinley's clothes had frozen solid in the sub zero temperatures. It was hoped that removing his clothing would also remove some of the radioactive contamination surrounding him, which would then make it safer for the people transporting his body. To get to the temporary morgue with him, a team was given cutting tools and a minute to try to get him out of his clothes. This wound up taking about a minute in seventeen seconds, and unfortunately it did not actually do that much to lower the radiation levels. Leg's body did not arrive at this temporary morgue until well after the disaster, because first the recovery team had to figure out how to safely retrieve him. He remained where he was pinned to the ceiling for six days. Although the reactor core was no longer critical, the area above the reactor had the highest radiation levels in the entire building. There were also concerns that the shield plug hole holding him in place might fall, hit the core and start another nuclear reaction. More photographers were sent in in thirty second shifts to document exactly where Leg was and what else was happening in the room so that the team could work out a plan. There were a couple of different attempts at this and in the end, on January ninth, eight men working in two man relays spent sixty five seconds each dropping his body onto a stretcher and then carrying that stretcher out of the building. Even though it was very warm in the room where he was his body had not started to decompose while it was pinned there, because the radiation had killed all of the microorganisms that are involved in that process. The same was also true of the two other men, which meant that while there was no safe way to involve their bodies, there also was no need to the Department of Defense coordinated with the men's families on their burial wishes. The bodies were wrapped in plastic and lead and placed in hermetically sealed, lead lined coffins. Then military cargo planes transported them to the towns where they were going to be buried. Burns and leg were buried in private cemeteries, and McKinley was buried at Arlington National Cemetery. Even with all these steps, there were still low levels of radiation surrounding the men's caskets, not enough to harm anyone through a brief exposure, but enough that precautions needed to be taken. Hell physicists traveled with each of the bodies to monitor the radiation levels and to provide guidance on how to keep everyone who was exposed to the caskets safe. At the cemetery's crews dug larger than normal graves They poured concrete into the bottoms, and then they placed the caskets onto those concrete slabs before filling the rest of the grave with concrete. The men's families were allowed to be present at the graveside, but only a few people could be there for each of them, and they were also kept at a distance during very brief services Because of all the time required to retrieve Leg's body and to carry out decontamination and autopsies. More than twenty days passed between the accident and when the men's bodies were transported for their burials. During that time, authorities were also working to verify the status of the reactor core and confirm whether it was at risk of going critical again. We will get to the efforts to clean up the SL one site after another sponsor break on May twenty third, nineteen sixty one, officials started the process of trying to determine the cause of the explosion at the SL one reactor, as well as removing the reactor core, decontaminating the area, and destroying the building. They also wanted to decontaminate the surrounding area so that usable buildings could be put back into service. We've really been focused on the reactor, but there were eight other support facilities there, plus a water storage tank, fuel storage tanks, an electrical substation, water and sewer systems, and other infrastructure in all of that had to be decontaminated. This involved steps like scrubbing everything to remove radioactive dust and residue, painting surfaces or covering them in concrete, and destroying things that could not be adequately treated. This was an enormous project, with more than eight hundred people involved. One reason that it took so many people was that the area around the reactor was still so highly radioactive, and some of it was highly hazardous, like vacuuming up radioactive dust in just a couple of minutes. People who carried out this type of work encountered the maximum amount of radiation that they were allowed to be exposed to for an entire quarter, So a lot of people cycled through the cleanup effort, reaching that quarterly maximum in only a minute or two of work, and then having to take three months before coming back. Radiation exposures were measured with instruments and tracked with film badges. Because there was a limited number of health physicists and they all needed to continue to be able to work, they typically kept time on people's relays to do their work outside of the danger zone, and then they would do something like bang on a piece of metal when the worker's time was up. Some of this work was also undertaken remotely because of the extreme hazards involved, including removing the reactor core. Like the removal of Leg's body, this required extensive planning and photographic documentation of the site. This time, much of the photography work involved remotely operated cameras built to with stand radiation, which were able to take pictures down into the reactor structure. Crews then built a mock up of the building to work out how to remove the core using a crane that was built on site. The cleanup process took eighteen months, with General Electric Corporation being contracted for the cleanup and removal of the reactor vessel. Kind of a side note, they had personnel available for this because that nuclear jet project we mentioned earlier had been scrapped, in part because the shielding necessary for the reactor would have made the aircraft too heavy to fly. Moving contaminated material to an existing nuclear waste disposal facility would have created additional hazards basically carrying highly radioactive material a long way away and contaminating everything it encountered in the process, so most of what could not be salvaged was buried there on site. Ninety nine thousand cubic feet of contaminated material were buried between eight and fourteen feet deep, with soil and vegetation also added to cover all of this area because additional precautions were possible during this cleanup process. The people who were exposed to the highest doses of radiation were mainly the first responders who had arrived on the scene immediately after the accident and the people who were there during the first week before Leg's body was recovered. Decontamination trailers were brought to the site for workers, where they had to go through a process of intensive scrubbing. The very first responders to arrive on the scene had to take additional steps for their hands because they didn't have special gloves to wear and thought it was more important to try to save McKinley's life. Across the Board, reports on this accident from official sources that came out within the first few years after it happened, and described these responders as not being negatively affected by their radiation exposures. Nobody showed clinical symptoms of radiation sickness at the time, nobody had to be hospitalized after their work on recovery or cleanup, but there's really not a lot of documentation on whether those radiation exposures affected their health later on. Some of the people who responded to this accident later died of cancer, including multiple miloma, and it's possible, but not conclusively proven, that this radiation exposure was a contributing factor. Official documents also focus on the idea that radiation exposure in the surrounding areas was minimal. The phrase quote very little contamination above background levels shows up in a lot of documents, but clouds of radioactive gas and particles did make their way to surrounding communities in the hours and days after that the explosion, including different isotopes of radioactive iodine. There was ongoing monitoring of the nearby environment for radiation after this accident, including periodically checking the roads for any radioactive contaminants that had been carried out on the tires of vehicles that were used at the site. We've already talked about a number of holes in the National Reactor Testing Station's emergency plans that became really obvious during this incident, like not already having a plan for how to handle contaminated bodies. So this led to a whole examination of all of these procedures. The National Reactor Testing Station also surveyed the forty seven licensed reactors in the United States to evaluate their safety and their emergency shutdown procedures. It was already known that the sl one's use of only five control rods was a risk, but after this requireedirements to keep reactors from being able to go critical with the removal of only one control rod, became known as the one stuck rod rule. In the aftermath of this accident, unions, including United Auto Workers also advocated for better worker protections at nuclear facilities. There was also a move to have these kinds of reactor operations overseen by highly trained nuclear mechanics supervised by a nuclear engineer, who were expected to follow extremely detailed, step by step procedures to the letter. After all this cleanup work, the remaining facilities that the building were approved for use on June twenty second, nineteen sixty two. Rather than building another reactor there, the site was used to house welding shops. These shops were closed down in nineteen eighty four, and funds for dismantling them were approved in nineteen ninety three. At that point, much of the site still showed signs of low level radioactive contamination, so there was another round of decontamination and processing. The effort to fully decontaminate and decommission the site took more than thirty eight thousand man hours over twenty one months. The EBA surveyed the site for safety twice in the early two thousands. Although the Army continued to use other smaller nuclear reactors after this incident, the SL one project was scrapped. The radar sites that the dow Line continued to be powered using diesel or electric generators. The dew Line was deactivated in the nineteen eighties and replaced with the North Warning System, and cleanup of some of those earlier de line sites is still ongoing. We haven't really talked about exactly what caused the SL One incident because there are still questions. More than sixty years later. Initially, when the men's bodies were misidentified, people thought McKinley, who was a trainee, had been lifting the control and had just simply made a mistake, but Burns, who was really the one moving the control rod, was more experienced. One possible conclusion was that the control rod had become stuck, and that when Burns broke through that stickiness, he accidentally moved the rod much farther than was necessary. Officials built a mock up of the reactor and carried out a bunch of experiments to see if this explanation even made sense, and they concluded that it was possible for one man to lift the control rod in a way that would have caused the explosion, but that it was not likely to have been the result of trying to free a stuck control rod. Another possibility was that this was an error on Leg's part as a supervisor. As we said earlier, three days before, the reactor had been shut down for the holiday and maintenance break crews had been ordered to undertake a quote complete rod travel exercise about four hours after the start of every shift. Although the men working at the reactor had repeatedly been told not to raise the rod more than four inches while reconnecting it. They had never been told why. So it's possible that Leg was trying to do two things at once, doing this travel exercise while also working on restarting the reactor, and that he just didn't realize what the consequences would be because he was not a nuclear engineer and had not been trained on that. Another possibility also puts some of the blame on Leg. He had a reputation for horseplay and being a practical joker, and there's speculation that he startled or grabbed Burns at a critical moment while Burns was lifting that control ride, and that Burns kind of yanked it up in response. And then there are rumors about the men's personal lives. One which seems to have been completely unsubstantiated was that Burns was having an affair with Leg's wife. This is briefly alluded to in one report of this incident, but nowhere else, and it seems to be entirely speculative. Although both men's wives flatly denied it, it was something that Leg's wife continued to be questioned about for years after this was over. There's more to back up the idea that Burns and Leg might just not have gotten along. In May of nineteen sixty, Leg and Burns had been at the same bachelor party, and after a night of carousing, Burns, who was married, allegedly had an encounter with a sex worker. Afterward, Leg and Burns reportedly got into a fistfight. It is not clear whether that is related to the sex worker or not. Leg and Burns had gone through their initial training together, but then Leg had been promoted and Burns had not, on the grounds that his commanding officers thought he wasn't ready. One of the reasons he wasn't ready being that he would get visibly angry and throw thing when he was upset, and Leg reportedly also had anger management issues. Before the holiday break, his supervisor told him that they would be having a meeting on January fourth to discuss a possible transfer, in part because Leg had been caught falsifying a time card for a friend. After being informed of this, Leg challenged his commanding officer to a fistfight. Burns had been transferred onto Leg's shift to replace the friend with the falsified time card, and it's possible that he was also angry about both the transfer and about being supervised by Leg, but again this is all speculation and we really don't know. Burns was also apparently having problems in his marriage. In addition to being in the military, he was having to work part time at a gas station just to make ends meet. His marriage seems to have become increasingly rocky, in part because he just was not around much, so his wife was having to manage their household and raise their child mostly on her own. They'd had a series of arguments, and apparently she called him at work on the night of January third to say that she wanted a divorce. She tried to call him again later that evening, reportedly because she had reconsidered, but then she couldn't reach him. So there's this idea that Burns was distraught over the state of his marriage and maybe was also angry at Leg, and that he pulled the control rod out on purpose. But this is again really speculative, and some sources conclude that this is all rumor that was intentionally spread to distract from the fact that the sl one reactor, with its boron flakes and sticky control rods and a design that could go super critical with only one rod removed, was inherently and unacceptably unsafe, and that it should have been taken out of commission before this accident even happened. Also, if all these personal details are true, it seems like a massive oversight on the part of the commanding officers to have assigned one man known for a volatile temper and another known for horseplay to work overnight shifts on a nuclear reactor, accompanied only by a trainee. So that's the sl one reactor. We'll talk about various things more on Friday. I have listener mail. It's from Elizabeth. It's on a topic we've already talked about, but I liked this email also, so I'm reading it to. Elizabeth wrote, Hi, ladies, You've probably gotten plenty of responses telling you this already. But in the behind the scenes Friday episode, when Tracy mentioned reading a book where a kid copied a key by making an impression and then carving a copy of it out of wood, I knew instantly what she was talking about. It was a story in the Great Brain series by John D. Fitzgerald, a collection of books about a family around the turn of the century, where one of the boys, the Great Brain, is always figuring something out and or coming up with some scheme. The kid is kind of like Sherlock Holmes crossed with P. T. Barnum. I remember one story where they go to a carnival side show featuring a mind reader, and the Great Brain figures out how he's doing it and then proceeds to fleece the neighborhood kids by putting on his own version of the show. The specific story you mentioned is I'm pretty sure from the Great Brain at the Academy, if I'm remembering right, he uses the key he ends up making to sneak out of the school, go to a nearby store to buy candy, and then bring it back to sell it a huge markup to the other students. I love the books when I was a kid, but I haven't looked at them for a year, so I can't swear to the quality. But hearing Tracy talk about it brought back some fond memories. Thanks so much for all you do. I've been a dedicated fan of a show for years. Best wishes, Elizabeth. Thank you for this email. Elizabeth, one hundred percent. That is the plot that I remember from the book that I was trying to reconstruct from memory. I also have not tried to go back to these books, and they were written, if I recall correctly, in like the mid twentieth century. So I would say if anybody is thinking of going to check them out based on them sounding interesting in our discussions of this on the show, I would say, it's probably a safe bet you're going to find ideas that are outdated at best at this point. But again I have not gone to look. I for sure have revisited childhood favorites much much later in my life and been like, yikes. Either yikes at the time and I didn't realize it, or yikes. The conversation we have about these ideas is totally different now. Some of those sometimes tho's the same thing, honestly. So if you would like to send us a note, we're at History Podcasts at iHeartRadio dot com, and you can also subscribe to our show on the iHeartRadio app or anywhere else you'd like to get your podcasts. Stuff you missed in History Class is a production of iHeartRadio. For more podcasts from iHeartRadio, visit the iHeartRadio app, Apple Podcasts, or wherever you listen to your favorite shows.

Welcome to Stuff You Missed in History Class, a production of iHeartRadio. Hello, and welcome to the podcast. I'm Tracy B. Wilson and I'm Holly Frye. A few weeks ago, some friends of mine were having a totally normal conversation about the Demon Core, specifically about Demon Core memes. We did an episode on the Demon Core in twenty twenty, and we just ran that as a Saturday Classic. But in case you missed it, this is a plutonium sphere made for use in a nuclear weapon that went on to be used in criticality experiments and it was involved in two different fatal accidents. And one of those accidents, a physicist was using a screwdriver to position a reflector so that the sphere would stay just below criticality. And if you're thinking that sounds like a bad idea, you're right. In the course of this conversation, my friend Adrian, who was the same Adrian who suggested an episode on the Demon Core, said that she would love a deep dive into the sl one reactor explosion. And that threw me for a second because I thought we had talked about it in that Demon Core episode at the end where we talked about other nuclear incidents, and in reality, the SL one got cut out of that episode because all the other nuclear accidents we were talking about in that episode it mostly involved people putting nuclear material into the wrong containers, and the SL one explosion was a whole other thing. It was the first, uh and I think only deadly nuclear reactor disaster in the United States. There have been other nuclear accidents that have have had casualties involved in fatalities involved, but this one was due to the reactor itself. So here is an early Christmas present Adrian episode is for you. The Stationary Low power Plant Number one or SL one was a small boiling water reactor built at the National Reactor Testing Station, which is now Idaho National Laboratory, about forty miles or sixty four kilometers west of Idaho Falls, Idaho. The testing station was established by the Atomic Energy Commission in nineteen forty nine to research, build, and test various nuclear reactors. Because of the nature of this work, the testing station was intentionally built in a remote area, but close enough to cities and towns that people moving to the area to work at the facility would be able to find a place to live. In the late nineteen fifties, the sl one was considered one of the least exciting reactors at the testing station. For comparison, one of the other prototypes developed there was a submarine reactor designed for the USS Nautilus, which was the Navy's first nuclear powered submarine. There was also a project going on to develop a nuclear powered jet aircraft. Both of those things sound very exciting, but the sl ones focus was all about practicality, efficiency, and reliability. It had been developed after a nineteen fifty five request by the Department of Defense for a nuclear power plant for the Defense Early Warning System, or the DO Line. The DEW Line was a chain of isolated radar stations about three thousand miles long from northwestern Alaska to southeastern Greenland, about two hundred miles north of the Arctic Circle. It's outside the scope of this episode, but the building, operation, and the eventual cleanup of the Dow Line all had and continue to have a massive impact on Inuit peoples all across this region. Its legacy for those communities has been described as mixed. The Dew Line created job opportunities, housing, and infrastructure that wouldn't have existed otherwise, but none of those were created with the needs of those communities in mind. To some extent, the same could be said of the National Reactor Testing Station, which was roughly the same distance from the Fort Hall Reservation as from Idaho Falls. This was during the Cold War, and crossing the Arctic was the most direct way for Soviet aircraft or missiles to potentially reach Canada or the United States, so the Dew Line, as that early warning name suggests, was meant to provide an early warning of such an attack. Construction on the new line had started in nineteen fifty four. With the radar stations getting power and heat from diesel generators. That meant that the military had to keep those generators supplied with fuel. The Army's criteria for a nuclear reactor to replace those generators included that it had to be built above ground with components that could be delivered to the site by cargo plane. It had to be able to withstand the extreme cold of the far North, and be reliable and easy to maintain by a small team of people. It also needed to run for at least three years without refueling. The SL one was a three megawat reactor designed for an output of two hundred kilowatts of net electricity and four hundred kilowatts of energy in the form of heat. This heat output would be important in the Arctic environment, but it was also important at the testing grounds in Idaho. On the night of the disaster, the temperature was roughly eighteen degrees below zero fahrenheit or about negative twenty eight celsius. The building the reactor was housed in was not meant to contain radiation from a meltdown or other disaster in the site because of its remote location, which would also be true for the dow line. The SL one's first five hundred hour test run started on August eleventh, nineteen fifty eight. After this test run, it was shut down for inspection, testing, maintenance, and to do various adjustments. From that point, the reactor would typically run for a period of one to six weeks, then it would be shut down again for maintenance and testing. At the same time, trainees would be going through both classroom and practical training on the reactor, and if they passed all of their various courses and assessments through this work, they could be certified as reactor operators. This all sounds fairly straightforward at least as straightforward as things can be when you're talking about an experimental nuclear reactor prototype that's also being used to train personnel, but there were a number of issues. Initially, this reactor was the responsibility of ARGON National Laboratory, but argun's role ended in early nineteen fifty nine. At that point, a civilian contractor called combat Rustan Engineering Incorporated took over, but didn't have policy and procedure manuals written. When that takeover happened, the Army, Air Force, and Navy were all sending people to be trained, and there were various rivalries and power grabs going on among the various military branches. The Atomic Energy Commission was also involved, but had a fairly hands off role in theory. Military personnel were handling the actual operation of the reactor with on site supervision through combustion engineering, but reading through all the overlapping responsibilities feels a little like looking at a company org chart where someone theoretically has one boss but also has a bunch of dotted lines to other people and departments. Like a lot of developments during the Cold War, including developments in the nuclear industry, things moved really quickly, and technologies often went into use without a lot of testing, since the Department of Defense wanted a reactor that could run for at least three years without refueling. The sl one was using burnable poisons to lower the core's reactivity when it was new. This sort of stretched out how long the fuel would last over time. These burnable poisons were strips of boron alloys that were tack welded onto the fuel assemblies. Soon, these fairly untested strips started warping in between those welds, and borons started flaking off of them and settling to the bottom of the reactor. Then there were the control rods. Nuclear reactors run on fission reactions. The fuel is an isotope whose atoms can split apart when they absorb a neutron that produces two new atoms along with heat and some more neutrons. Some of those neutrons have the right amount of energy to split more atoms, which continues the cycle. With the right number of neutrons. This leads to a self sustaining or critical reaction. With too many neutrons, the reaction can go supercritical, meaning that it starts to escalate. Control rods absorb some of the neutrons controlling the rate of the reaction. Most reactors have numerous control rods that have to be adjusted in sequence to start or stop a critical reaction. To cut down on maintenance and make it easier to operate, The sl one only had five, and one control rod could do that all by itself. This was obviously risky, but at first these five control rods seemed to work fairly well. Over time, though, they developed what was described as a stickiness and this is just what it sounds like. When the rods needed to be raised or lowered, they might get stuck. This only happened about two percent of the time, but that meant over the life of the reactor it happened about eighty time, and that is not great when we are talking about the rods that are controlling a nuclear reaction. There was also an emergency shut down procedure, or a scram, in which the rods were all supposed to drop into the reactor just by gravity. Forty six times at least one rod failed to drop and it had to be driven down using an electrical clutch. This problem happened randomly, but it also seemed to be getting worse. More than thirty of those recorded stickiness incidents happened just in November and December of nineteen sixty. This stickiness seems to have been connected to the burnable poisons in the way that they were warping between the wells. On top of that, the boron that was flaking off was affecting the reactivity of the fuel in unpredictable ways, making it hard to calculate exactly how far the rods needed to move to control the reaction. And those flakes of boron and other fore and matter were affecting the water seals around the reactor's drive shafts, which also may have contributed to the stickiness. Increasing water filtration seemed to help somewhat, and on December twentieth, nineteen sixty, technicians were ordered to quote perform a complete rod travel exercise at approximately four hours after the start of each shift, meaning to manually raise and lower each rod to try to keep it moving smoothly. The SL one incident happened two weeks after that order was given, and we'll have more after a sponsor break. On December twenty third, nineteen sixty, the SL one reactor was shut down for a holiday break, and during that shutdown procedure, three of the control rods stuck and had to be driven into the reactor. Bruz returned on December twenty seventh to start on various maintenance tasks. With the reactor still shut down. On January third, nineteen sixty one, the night shift was tasked with restarting it. The reactor was staffed around the clock in three eight hour shifts, but the facility had minimal staffing during the night, including the facility gate being left locked rather than being staffed with a security guard. Three men were on duty that night, Navy CB Richard C. Legg, known as Dick, who was the shift supervisor, Army specialist John A. Burns the third known as Jack, and Army Specialist Richard Leroy McKinley, who was a trainee. All three of these men were in their twenties. Since part of the point of this project was to build a reactor that the Army could maintain with minimal staffing in a remote area, none of them had a background in nuclear engineering. Leg was experienced in the procedure they were due, but this was the first time he was doing it as a supervisor. The US Atomic Energy Commission made a video brief after this incident that gives us step by step recreation of how technicians reconnected the reactor's rack and pinion system before restarting it. I have no background in this field, but as a layperson, it struck me as very fiddly and inexact as a way to handle the control rods in a nuclear reactor. I was not alone in this. I showed this video to Adrian and she was like, what is happening? This was a two man job. First they would lower a shield plug and then opinion gear housing and then a spring housing over the rack. Then they would insert a handling tool into the spring housing and threaded onto the rack like a screw. This handling tool was basically a rod that they could grab onto. One person would pull upward on that tool to lift the rack a few inches while the other person tightened a sea clamp onto it. Then they would lower it until it rested on that clamp, Take the handling tool off, put a retaining washer and a nut onto the rack, put the handling tool back on again, and do a second lift, this time just far enough to take the seaclamp off. This is like the seaclamp that you would see at a hardware store that you put on, you know, to hold maybe a piece of board to the table, and you screw the little thing at the bottom. Under normal circumstances, the washer and nut would have connected the rack to a drive motor, but for unclear reasons, while doing this process for the central control, rod Burns suddenly raised it more than twenty inches rather than the few inches that were required. This was also farther than the distance that would have been needed to start a critical reaction. This resulted in what was known as a prompt criticality, that is, a supercritical state that is caused only by the initial influx of neutrons into the fuel, not involving any delayed neutrons that are emitted later on in the fission process. This reaction only took about four milliseconds, so it was almost instantaneous. The power level surged to more than six thousand times the reactor's rated output. The heat vaporized the water in the reactor, which created a water hammer that blew inside the top of the reactor housing, lifting the entire thing about nine feet or two point seven meters off the ground. While this reactor was considered to be small and lightweight. It weighed twenty six thousand pounds, so this was a massive amount of energy. About twenty percent of the reactor's radioactive fuel melted, and the explosion for the fuel rods away from one another and toward the walls of the containment vessel. The other four control rods were still partly or fully inserted into the core afterward, so the steam explosion had cut off the critical reaction, but this wouldn't be clear until much later. When this happened, alarms started going off at the Atomic Energy Commission fire stations and security headquarters, about ten miles east of the reactor. A personnel radiation monitor about a mile away from the reactor also alarmed, and a patrolman reported that all the needles on this monitor were at their maximum reading and it could not be reset. There had also been two false alarms earlier in the day caused by a malfunctioning fire detector in an auxiliary building, so while the first responders did not know what was going on when they got this alarm, they wouldn't have been surprised if it was just another false alarm. When firefighters arrived, the outside of the building seemed undamaged, and apart from some steam rising above the roof, there didn't seem to be anything suspicious going on. After security arrived and unlocked the gate, they entered through the administration building with their regular fire protection gear, self contained breathing systems, and radiation detectors. They didn't know for sure how many people were inside the building, but the coats, lunch pails, and cups of coffee in the brake room suggested there might be three. But the firefighters didn't see any other sign of anyone, and no one answered when they called out or pounded on the door. Radiation alarms were going off when they got into the building, but at first the firefighter's own radiation detectors did not show levels that would keep them from performing a search. But when they got into the staircase that led up to the reactor, their radiation detectors maxed out at the highest possible reading, so suddenly that at first the firefighters wondered if they were malfunctioning. They weren't, though it was obvious that there was too much radiation for them to just go into the stairwell with the gear that they had, so they left the building and they waited for a health physicist. A health physicist is somebody whose job is to protect the safety of the people who work with radiation, as well as the safety of their environment. A health physicist arrived a little more than fifteen minutes after the initial alarm and they all went inside, but once they got to that stairway, the health physicist again had them turned back. It was determined they needed more protective gear. Not long after, two more health physicists arrived with anti contamination gear, shoe covers, additional respirators and breathing systems, as well as other equipment. By that point, the reactor room up the stairs was the only place at the facility where those three men could be even with protective gear. Radiation levels in the building were so high that the search had to be carried out in relays of only about a minute each. The health physicist kept time with a stopwatch. In addition to this strict time limit, conditions inside were difficult to navigate. Once rescuers got up the stairs and into the reactor room, the floor was wet and it was covered with debris. Some of this debris was compared to a lot of marbles, and their face masks kept fogging over. Once they got into the reactor room, firefighters spotted one man who was still breathing and another who appeared to be dead. At first, they didn't know who was who or where the third man was, but the person who was still alive was later identified as Richard McKinley, aged twenty seven. The initial priority was to try to save his life. A team of five volunteers went inside carrying a stretcher, two of them to try to remove McKinley, and the other three to see if they could figure out where the third man was. While they did do kind of a relay to remove McKinley from the scene, they still did not see any sign of the third man. McKinley was taken to an ambulance, which was then moved away from the road to keep it from contaminating the road with radiation. McKinley did not survive, though he was pronounced dead about two hours after the incident. His body contaminated the ambulance with radiation, and it also exposed the on call nurse who cared for him to a large amount of radiation. The effort to rescue McKinley had been carried out as fast as possible because he was still alive, Rescuers took more time to plan out how to remove the body that they'd seen, including sending photographers into the room for ten seconds each to document exactly where he was. It was during that process that one of the team members happened to spot the body of the third man, pinned to the ceiling by one of the reactor's shield plugs. It was eventually determined that the body on the floor was Jack Burn's age twenty two, and that the body pinned to the ceiling was Dick leg age twenty six. That determination was not made for a little while, though, They did not know what was happening at this point, so they and McKinley had all experienced catastrophic and really gruesome injuries. Even though the sl one had been built at the National Reactor Testing Station, whose purpose was to build and test experimental nuclear reactors, there was not really a plan for what to do with highly radioactive bodies after an accident. Their bodies were so heavily contaminated and the nearest morgues were far enough away that drivers would have absorbed a a fatal dose of radiation just trying to transport them there in that moment, the vehicle itself would also be contaminated, and so would the roads that it traveled on, and then so would the morgue. Ultimately, a decision was made to turn the decontamination room at the facility's on site chemical processing plant into a temporary morgue, both to store the bodies and decontaminate them as much as possible. They were transported there in the same ambulance where McKinley had died, draped in lead blankets with lead aprons draped over the back of the driver's seat. Once there, they went through decontamination as well as autopsies. During this process, the autopsy team discovered that all three men had been wrongly identified. The correct identification was based on their heights and weights and their tattoos, because their faces were unrecognizable. As the team had been figuring out what to do with these bodies, figuring out to take them to this temporary morgue, McKinley's clothes had frozen solid in the sub zero temperatures. It was hoped that removing his clothing would also remove some of the radioactive contamination surrounding him, which would then make it safer for the people transporting his body. To get to the temporary morgue with him, a team was given cutting tools and a minute to try to get him out of his clothes. This wound up taking about a minute in seventeen seconds, and unfortunately it did not actually do that much to lower the radiation levels. Leg's body did not arrive at this temporary morgue until well after the disaster, because first the recovery team had to figure out how to safely retrieve him. He remained where he was pinned to the ceiling for six days. Although the reactor core was no longer critical, the area above the reactor had the highest radiation levels in the entire building. There were also concerns that the shield plug hole holding him in place might fall, hit the core and start another nuclear reaction. More photographers were sent in in thirty second shifts to document exactly where Leg was and what else was happening in the room so that the team could work out a plan. There were a couple of different attempts at this and in the end, on January ninth, eight men working in two man relays spent sixty five seconds each dropping his body onto a stretcher and then carrying that stretcher out of the building. Even though it was very warm in the room where he was his body had not started to decompose while it was pinned there, because the radiation had killed all of the microorganisms that are involved in that process. The same was also true of the two other men, which meant that while there was no safe way to involve their bodies, there also was no need to the Department of Defense coordinated with the men's families on their burial wishes. The bodies were wrapped in plastic and lead and placed in hermetically sealed, lead lined coffins. Then military cargo planes transported them to the towns where they were going to be buried. Burns and leg were buried in private cemeteries, and McKinley was buried at Arlington National Cemetery. Even with all these steps, there were still low levels of radiation surrounding the men's caskets, not enough to harm anyone through a brief exposure, but enough that precautions needed to be taken. Hell physicists traveled with each of the bodies to monitor the radiation levels and to provide guidance on how to keep everyone who was exposed to the caskets safe. At the cemetery's crews dug larger than normal graves They poured concrete into the bottoms, and then they placed the caskets onto those concrete slabs before filling the rest of the grave with concrete. The men's families were allowed to be present at the graveside, but only a few people could be there for each of them, and they were also kept at a distance during very brief services Because of all the time required to retrieve Leg's body and to carry out decontamination and autopsies. More than twenty days passed between the accident and when the men's bodies were transported for their burials. During that time, authorities were also working to verify the status of the reactor core and confirm whether it was at risk of going critical again. We will get to the efforts to clean up the SL one site after another sponsor break on May twenty third, nineteen sixty one, officials started the process of trying to determine the cause of the explosion at the SL one reactor, as well as removing the reactor core, decontaminating the area, and destroying the building. They also wanted to decontaminate the surrounding area so that usable buildings could be put back into service. We've really been focused on the reactor, but there were eight other support facilities there, plus a water storage tank, fuel storage tanks, an electrical substation, water and sewer systems, and other infrastructure in all of that had to be decontaminated. This involved steps like scrubbing everything to remove radioactive dust and residue, painting surfaces or covering them in concrete, and destroying things that could not be adequately treated. This was an enormous project, with more than eight hundred people involved. One reason that it took so many people was that the area around the reactor was still so highly radioactive, and some of it was highly hazardous, like vacuuming up radioactive dust in just a couple of minutes. People who carried out this type of work encountered the maximum amount of radiation that they were allowed to be exposed to for an entire quarter, So a lot of people cycled through the cleanup effort, reaching that quarterly maximum in only a minute or two of work, and then having to take three months before coming back. Radiation exposures were measured with instruments and tracked with film badges. Because there was a limited number of health physicists and they all needed to continue to be able to work, they typically kept time on people's relays to do their work outside of the danger zone, and then they would do something like bang on a piece of metal when the worker's time was up. Some of this work was also undertaken remotely because of the extreme hazards involved, including removing the reactor core. Like the removal of Leg's body, this required extensive planning and photographic documentation of the site. This time, much of the photography work involved remotely operated cameras built to with stand radiation, which were able to take pictures down into the reactor structure. Crews then built a mock up of the building to work out how to remove the core using a crane that was built on site. The cleanup process took eighteen months, with General Electric Corporation being contracted for the cleanup and removal of the reactor vessel. Kind of a side note, they had personnel available for this because that nuclear jet project we mentioned earlier had been scrapped, in part because the shielding necessary for the reactor would have made the aircraft too heavy to fly. Moving contaminated material to an existing nuclear waste disposal facility would have created additional hazards basically carrying highly radioactive material a long way away and contaminating everything it encountered in the process, so most of what could not be salvaged was buried there on site. Ninety nine thousand cubic feet of contaminated material were buried between eight and fourteen feet deep, with soil and vegetation also added to cover all of this area because additional precautions were possible during this cleanup process. The people who were exposed to the highest doses of radiation were mainly the first responders who had arrived on the scene immediately after the accident and the people who were there during the first week before Leg's body was recovered. Decontamination trailers were brought to the site for workers, where they had to go through a process of intensive scrubbing. The very first responders to arrive on the scene had to take additional steps for their hands because they didn't have special gloves to wear and thought it was more important to try to save McKinley's life. Across the Board, reports on this accident from official sources that came out within the first few years after it happened, and described these responders as not being negatively affected by their radiation exposures. Nobody showed clinical symptoms of radiation sickness at the time, nobody had to be hospitalized after their work on recovery or cleanup, but there's really not a lot of documentation on whether those radiation exposures affected their health later on. Some of the people who responded to this accident later died of cancer, including multiple miloma, and it's possible, but not conclusively proven, that this radiation exposure was a contributing factor. Official documents also focus on the idea that radiation exposure in the surrounding areas was minimal. The phrase quote very little contamination above background levels shows up in a lot of documents, but clouds of radioactive gas and particles did make their way to surrounding communities in the hours and days after that the explosion, including different isotopes of radioactive iodine. There was ongoing monitoring of the nearby environment for radiation after this accident, including periodically checking the roads for any radioactive contaminants that had been carried out on the tires of vehicles that were used at the site. We've already talked about a number of holes in the National Reactor Testing Station's emergency plans that became really obvious during this incident, like not already having a plan for how to handle contaminated bodies. So this led to a whole examination of all of these procedures. The National Reactor Testing Station also surveyed the forty seven licensed reactors in the United States to evaluate their safety and their emergency shutdown procedures. It was already known that the sl one's use of only five control rods was a risk, but after this requireedirements to keep reactors from being able to go critical with the removal of only one control rod, became known as the one stuck rod rule. In the aftermath of this accident, unions, including United Auto Workers also advocated for better worker protections at nuclear facilities. There was also a move to have these kinds of reactor operations overseen by highly trained nuclear mechanics supervised by a nuclear engineer, who were expected to follow extremely detailed, step by step procedures to the letter. After all this cleanup work, the remaining facilities that the building were approved for use on June twenty second, nineteen sixty two. Rather than building another reactor there, the site was used to house welding shops. These shops were closed down in nineteen eighty four, and funds for dismantling them were approved in nineteen ninety three. At that point, much of the site still showed signs of low level radioactive contamination, so there was another round of decontamination and processing. The effort to fully decontaminate and decommission the site took more than thirty eight thousand man hours over twenty one months. The EBA surveyed the site for safety twice in the early two thousands. Although the Army continued to use other smaller nuclear reactors after this incident, the SL one project was scrapped. The radar sites that the dow Line continued to be powered using diesel or electric generators. The dew Line was deactivated in the nineteen eighties and replaced with the North Warning System, and cleanup of some of those earlier de line sites is still ongoing. We haven't really talked about exactly what caused the SL One incident because there are still questions. More than sixty years later. Initially, when the men's bodies were misidentified, people thought McKinley, who was a trainee, had been lifting the control and had just simply made a mistake, but Burns, who was really the one moving the control rod, was more experienced. One possible conclusion was that the control rod had become stuck, and that when Burns broke through that stickiness, he accidentally moved the rod much farther than was necessary. Officials built a mock up of the reactor and carried out a bunch of experiments to see if this explanation even made sense, and they concluded that it was possible for one man to lift the control rod in a way that would have caused the explosion, but that it was not likely to have been the result of trying to free a stuck control rod. Another possibility was that this was an error on Leg's part as a supervisor. As we said earlier, three days before, the reactor had been shut down for the holiday and maintenance break crews had been ordered to undertake a quote complete rod travel exercise about four hours after the start of every shift. Although the men working at the reactor had repeatedly been told not to raise the rod more than four inches while reconnecting it. They had never been told why. So it's possible that Leg was trying to do two things at once, doing this travel exercise while also working on restarting the reactor, and that he just didn't realize what the consequences would be because he was not a nuclear engineer and had not been trained on that. Another possibility also puts some of the blame on Leg. He had a reputation for horseplay and being a practical joker, and there's speculation that he startled or grabbed Burns at a critical moment while Burns was lifting that control ride, and that Burns kind of yanked it up in response. And then there are rumors about the men's personal lives. One which seems to have been completely unsubstantiated was that Burns was having an affair with Leg's wife. This is briefly alluded to in one report of this incident, but nowhere else, and it seems to be entirely speculative. Although both men's wives flatly denied it, it was something that Leg's wife continued to be questioned about for years after this was over. There's more to back up the idea that Burns and Leg might just not have gotten along. In May of nineteen sixty, Leg and Burns had been at the same bachelor party, and after a night of carousing, Burns, who was married, allegedly had an encounter with a sex worker. Afterward, Leg and Burns reportedly got into a fistfight. It is not clear whether that is related to the sex worker or not. Leg and Burns had gone through their initial training together, but then Leg had been promoted and Burns had not, on the grounds that his commanding officers thought he wasn't ready. One of the reasons he wasn't ready being that he would get visibly angry and throw thing when he was upset, and Leg reportedly also had anger management issues. Before the holiday break, his supervisor told him that they would be having a meeting on January fourth to discuss a possible transfer, in part because Leg had been caught falsifying a time card for a friend. After being informed of this, Leg challenged his commanding officer to a fistfight. Burns had been transferred onto Leg's shift to replace the friend with the falsified time card, and it's possible that he was also angry about both the transfer and about being supervised by Leg, but again this is all speculation and we really don't know. Burns was also apparently having problems in his marriage. In addition to being in the military, he was having to work part time at a gas station just to make ends meet. His marriage seems to have become increasingly rocky, in part because he just was not around much, so his wife was having to manage their household and raise their child mostly on her own. They'd had a series of arguments, and apparently she called him at work on the night of January third to say that she wanted a divorce. She tried to call him again later that evening, reportedly because she had reconsidered, but then she couldn't reach him. So there's this idea that Burns was distraught over the state of his marriage and maybe was also angry at Leg, and that he pulled the control rod out on purpose. But this is again really speculative, and some sources conclude that this is all rumor that was intentionally spread to distract from the fact that the sl one reactor, with its boron flakes and sticky control rods and a design that could go super critical with only one rod removed, was inherently and unacceptably unsafe, and that it should have been taken out of commission before this accident even happened. Also, if all these personal details are true, it seems like a massive oversight on the part of the commanding officers to have assigned one man known for a volatile temper and another known for horseplay to work overnight shifts on a nuclear reactor, accompanied only by a trainee. So that's the sl one reactor. We'll talk about various things more on Friday. I have listener mail. It's from Elizabeth. It's on a topic we've already talked about, but I liked this email also, so I'm reading it to. Elizabeth wrote, Hi, ladies, You've probably gotten plenty of responses telling you this already. But in the behind the scenes Friday episode, when Tracy mentioned reading a book where a kid copied a key by making an impression and then carving a copy of it out of wood, I knew instantly what she was talking about. It was a story in the Great Brain series by John D. Fitzgerald, a collection of books about a family around the turn of the century, where one of the boys, the Great Brain, is always figuring something out and or coming up with some scheme. The kid is kind of like Sherlock Holmes crossed with P. T. Barnum. I remember one story where they go to a carnival side show featuring a mind reader, and the Great Brain figures out how he's doing it and then proceeds to fleece the neighborhood kids by putting on his own version of the show. The specific story you mentioned is I'm pretty sure from the Great Brain at the Academy, if I'm remembering right, he uses the key he ends up making to sneak out of the school, go to a nearby store to buy candy, and then bring it back to sell it a huge markup to the other students. I love the books when I was a kid, but I haven't looked at them for a year, so I can't swear to the quality. But hearing Tracy talk about it brought back some fond memories. Thanks so much for all you do. I've been a dedicated fan of a show for years. Best wishes, Elizabeth. Thank you for this email. Elizabeth, one hundred percent. That is the plot that I remember from the book that I was trying to reconstruct from memory. I also have not tried to go back to these books, and they were written, if I recall correctly, in like the mid twentieth century. So I would say if anybody is thinking of going to check them out based on them sounding interesting in our discussions of this on the show, I would say, it's probably a safe bet you're going to find ideas that are outdated at best at this point. But again I have not gone to look. I for sure have revisited childhood favorites much much later in my life and been like, yikes. Either yikes at the time and I didn't realize it, or yikes. The conversation we have about these ideas is totally different now. Some of those sometimes tho's the same thing, honestly. So if you would like to send us a note, we're at History Podcasts at iHeartRadio dot com, and you can also subscribe to our show on the iHeartRadio app or anywhere else you'd like to get your podcasts. Stuff you missed in History Class is a production of iHeartRadio. For more podcasts from iHeartRadio, visit the iHeartRadio app, Apple Podcasts, or wherever you listen to your favorite shows.