When Science Goes Wrong: Twelve Tales From the Dark Side of Discovery - Simon LeVay (2008)

NUCLEAR PHYSICS: Meltdown

THE TOMBSTONE OF Richard Leroy McKinley looks no different from hundreds of others in Section 31 of Arlington National Cemetery. It’s a plain stone slab, decorated with a simple cross. It lists McKinley’s date of birth (December 2, 1933) and death (January 3, 1961), states his rank (Army Specialist 4), and mentions his service in Korea.

If you were to dig beneath the stone, however – an act which is forbidden by a special order from the office of the US Adjutant General – you would find something out of the ordinary. You would have to dig through three feet of earth, then drill through a foot-thick slab of concrete, then break open a metal enclosure that reaches ten feet into the ground, and then work your way through another concrete casing before you got to the metal casket, which is lined with lead sheeting. If you finally managed to get the casket open, you would find what appeared to be a mummy, wrapped in successive layers of lead, plastic, and cotton sheeting. After unwinding these wrappings, you would finally see the mortal remains of Richard McKinley himself. You would notice that his belly and chest have been roughly sliced open and his internal organs removed, along with his left arm and most of his skin. While pondering this macabre scene, you would be absorbing enough nuclear radiation to put your own life in peril.

McKinley was one of three men – the others were John Byrnes and Richard Legg – who died in a night time explosion at the National Reactor Testing Station (now the Idaho National Laboratory) on Idaho’s Snake River Plain. The cause of the explosion, in a scientific sense, was quickly figured out. But the human cause of the accident – if, indeed, it was an accident – remains a mystery 45 years after the event.

The Testing Station opened in 1949. Throughout the 1950s and beyond, it was ground central for America’s effort to develop controlled nuclear fission as the basis for power generation, both for military and civilian applications. The Station’s first reactor went critical in 1951, and a couple dozen more were constructed during the remainder of the decade.

The reactor where the three men died became operational in 1958. It was called Stationary Low-Power Reactor Unit 1, or SL-1 for short. The ‘stationary’ in its name set it apart from the reactors then being developed for submarines, ships, and even aircraft. The ‘low-power’ referred to the fact that SL-1 was designed as a compact, easily transported and easily operated device that could provide modest amounts of electricity and heat. Its main intended application was to power the stations of the Distant Early Warning Line – the radar and radio installations that had been strung out across the North American Arctic to alert the USA to a Soviet bomber or missile attack.

The SL-1 reactor was located, like all the other Testing Station reactors, on a sagebrush desert in the middle of nowhere. The nearest sizeable community, the town of Idaho Falls, lay 40 miles to the east, and was where the reactor operators lived. Because of the lack of a nearby population that might be put at risk by a nuclear accident, and because the reactor was designed for use in even more remote locations, it had no concrete containment structure. Instead, it was housed in a simple silo-like building, about 50ft high and clad in sheet metal.

The building had three levels. In the lowest level sat the reactor itself, buried in a bed of gravel. The middle level – the reactor room – gave the operators access to the top of the reactor and the all-important control rods, as well as to the turbine generator that converted the reactor’s heat to electricity. The top level (the ‘attic’) contained a condenser and fans to convert the steam that exited the generator back to water. In addition, a long, low building directly abutted the silo. This contained the control room and offices.

The design of the reactor was quite simple. At the bottom of a 15ft-high steel vessel was the reactor core, a set of fuel plates containing uranium metal that had been moderately enriched in the radioactive isotope uranium-235, or235U. The nucleus of a 235U atom will disintegrate when it absorbs a low-energy neutron, and the disintegration is accompanied by the release of several high-energy neutrons. For a nuclear chain reaction to occur, the energy of the emitted neutrons must be reduced to a level that can trigger further disintegrations. In the SL-1 reactor, this was accomplished by water that circulated between the fuel plates. Thus, SL-1 was a ‘water-moderated’ reactor. Water also served to carry heat from the reactor to the generator.

The essential requirement for a nuclear reactor is that the nuclear chain reaction be controllable. For that purpose, SL-1 was equipped with five control rods whose lowermost portions were blades made of cadmium metal, an efficient absorber of neutrons. Each rod weighed about 100lb, or 45kg, and was seven feet long. When the rods were all dropped to their lowest position, so that the blades lay between the fuel plates, they absorbed enough neutrons to terminate the chain reaction. Raising the rods by a few inches allowed the reaction to begin. During normal operation, the control rods were raised and lowered by motors located in the reactor room above the reactor, and the motors were controlled remotely by operators in the control room.

Jack Byrnes and Dick Legg joined the SL-1 staff in the autumn of 1959. Byrnes was 20 years old; he came from Utica, New York, and he brought with him his 19-year-old wife, Arlene, and their one-year-old son. Legg was a single man from rural Michigan, but he married a woman from the local Mormon community soon after he arrived in Idaho Falls. Byrnes had enlisted in the US Army and Legg in the US Navy, but the two men knew each other before they arrived in Idaho because they had taken the same training programme in Virginia over the previous months.

By the time of the accident on January 3, 1961, Byrnes and Legg had more than a year of experience operating the SL-1 reactor. Legg, in fact, had already been designated a chief operator and shift supervisor. Richard McKinley, on the other hand, was a new arrival and was still a trainee. He had much more experience in the military than the other two men, however; he was 28, and he had served both in the Army and the Air Force. He was married with two children.

On December 23, 1960, 11 days before the accident, SL-1 workers shut the reactor down for the Christmas holiday. They did this, as usual, by dropping the five control rods to their lowermost position. Several of the rods failed to drop under their own weight, however, and had to be driven down. This ‘sticking’ behaviour had been noticed before, but it wasn’t considered a serious problem. The key central rod which, on account of its position, was capable of starting and stopping the nuclear chain reaction by itself, had never stuck, nor did it do so on this occasion.

During the day on January 3, a work crew detached the control rods from the motors that normally raised and lowered them, in order to conduct some tests. The workers left the task of reconnecting the rods and restarting the reactor to the night crew, which consisted of Byrnes, Legg, and McKinley. The three men came on duty in the late afternoon. The last contact that anyone in the outside world had with them was around 7pm, when Byrnes’s wife spoke to him on the telephone.

At 9.01pm, an automatic alarm sounded at the Testing Station’s firehouse, signalling a problem at the SL-1 reactor. There had been two such alarms earlier that day, and both had turned out to be false, having been triggered by a faulty fire detector. Thus the firemen suspected that this alarm was false, too. Nevertheless they set out in a car and fire truck, reaching the reactor at 9.10pm. When they entered the control room, they found it deserted, but radiation alarms were sounding and a radiation detector carried by one of the firemen confirmed potentially dangerous levels of radiation.

The fire crew decided to check the reactor room, which was reached by a metal staircase that wound around the outside of the reactor building. By the time they were halfway up the staircase, their radiation detector was pegging out at 500 roentgens per hour, meaning that the men would absorb one year’s permissible dose of radiation in less than two minutes. They retreated. Then one of them climbed quickly to the top of the staircase and took a glance inside the reactor room before descending again. He saw that the floor of the room was awash with water from the reactor and was littered with broken equipment and gravel from the shielding bed. He didn’t see any of the three missing men.

A major disaster alarm was now sounded, and officials were roused at the Testing Station in Idaho Falls, and even in Washington DC. Among the men who raced to the site was Ed Vallario, the health physicist responsible for the SL-1 reactor. At around 10.30pm, wearing respirators but no other protective gear, Vallario and another man ran up the staircase to the reactor room. Again, their radiation detectors went off scale. When they reached the entrance to the reactor room and looked inside, they saw Richard McKinley. He was lying by the control panel, moaning and twisting his body in an apparent attempt to reach the controls. The right side of his face was severely injured. Near him lay the lifeless body of Jack Byrnes. Dick Legg was nowhere to be seen.

The two rescuers beat a hasty retreat. Vallario knew that McKinley must have absorbed a lethal dose of radiation, but he was still alive so he had to be rescued. Vallario and four other men found a stretcher and made another foray into the reactor room. They were able to get McKinley onto the stretcher and out of the building, but not before two of the men’s respirators malfunctioned, forcing them to remove the respirators momentarily and to inhale the unfiltered, contaminated air of the reactor room.

The rescuers placed McKinley in a truck and then transferred him to an arriving ambulance. In the ambulance he was tended to by a nurse, Hazel Leisen, but within moments – before the ambulance could even get onto the main road – he died. Health physicists quickly pulled Leisen out of the ambulance, for radiation levels inside the vehicle were 500 roentgens per hour – enough to kill anyone who drove in it for more than a few minutes. The driver was wrapped in a lead blanket and told to drive the ambulance off into the sagebrush, so as not to expose people passing on the road. He did so, and then made a run for it.

With McKinley and Byrnes both dead, there was but one urgent question remaining: where was the third member of the night crew? To find the answer, another team of four volunteers entered the reactor room. They searched around futilely and in increasing desperation as the seconds ticked away. Then one of the men’s flashlights happened to point upward.

Dick Legg’s body was pinned to the ceiling by one of the reactor’s control rods, as if by a giant thumbtack. Evidently, the control rod had shot explosively out of the reactor and had passed through Legg’s pelvis and abdomen on the way to the ceiling, carrying his entire body with it. Now he dangled, limply; he was very obviously dead. The men ran from the room.

An hour or two after midnight, teams went to the homes of the three dead men to notify their wives – now widows – of the tragedy.

The acute emergency was over, but two difficult problems lay ahead. The dead men needed to be removed from the site, decontaminated, autopsied, and buried. And the reactor needed to be rendered safe, broken down, and analysed so that the cause of the accident could be established.

Richard McKinley’s body needed to be dealt with first, because it was still lying in the abandoned ambulance out amongst the sagebrush. Operating in minute-long shifts, workers approached the ambulance and, using poles and other tools, succeeded in removing McKinley’s clothes and wrapping the body in lead blankets. After roads were closed to other traffic, a volunteer put on a lead-lined jacket and drove the ambulance at high speed to the Testing Station’s uranium reprocessing plant, where the body was placed in a steel bath containing ice and alcohol. The hope was that this would leach radioactive contamination off the body. Later that day, other teams of workers dashed into the reactor room and, working in relays, removed the body of Jack Byrnes, which was then also brought to the reprocessing plant.

Removing Dick Legg’s body, impaled as it was to the ceiling of the reactor room, presented a far more challenging task. Not only was it in an extremely high-radiation environment; there was also the risk that, if it fell onto the broken and exposed reactor during the recovery effort, it might trigger a second nuclear accident.

At least the rescuers had time on their side, for the radiation was so intense that Legg’s body had been completely sterilised: every bacterium inside and outside of his body had been killed, and the body would therefore not decompose.

As a first step in the recovery, radiation specialists built a full-scale mock-up of the reactor room, where they could test various strategies for reaching and removing the body. By five days after the accident they had settled on a strategy and put it into effect. First, they opened a large freight door that gave access to the reactor room from outside the building. Then they obtained a crane with a long boom and attached a netlike structure to the end of it. The crane operator, working blind behind a lead shield but guided by a distant spotter, manoeuvred the net through the cargo door and under Legg’s body. Then volunteers, working in minute-long relays, ran into the reactor room with long, hooked poles and attempted to drag the body down from the control rod. After several relays, the mangled body did indeed fall into the net, and it was removed from the building and taken to the reprocessing plant.

In an official film made to document the SL-1 accident and its aftermath, the narrator stated that the three bodies were successfully decontaminated by washing, and thus were brought into a state in which they could be safely returned to their families and buried. This was a complete fiction, however. In reality, repeated washing and even shaving of the men’s body hair had little effect in reducing radiation levels near the corpses, which still ranged up to 1,500 roentgens per hour. Countless particles of nuclear fuel had penetrated all three men’s bodies, in effect converting them into high-level nuclear waste. No one could safely remain close to them for more than a minute or so. Performing autopsies and dealing with the ultimate disposal of the bodies therefore presented an extraordinary challenge.

Three physicians from Los Alamos National Laboratory took on the task. Working behind lead shields set up several feet away, the doctors manipulated the bodies with instruments attached to long steel pipes. They first documented the injuries caused by the blast. Richard McKinley, the only one of the crew who was not killed instantly, had major wounds to his scalp, face and eyes, and to his left hand and left leg. Jack Byrnes, whose dead body had been found lying next to the reactor, had more severe injuries. His face, throat, rib cage, left arm, left leg and back were completely crushed, and his pelvis had been driven up into his abdomen. As for Dick Legg, who had been found impaled into the ceiling of the reactor room, his body had suffered devastating damage. The top off his head had been sliced off, exposing his brain, and his face was collapsed inward. The upper half of his body had been twisted by 180 degrees with respect to the lower half, and his internal organs had been destroyed or displaced by the control rod as it blasted through his pelvis and abdomen. His left leg was cut almost in two.

With the clumsy tools available to them, the doctors cut open the bodies and removed the internal organs for microscopic study. A more difficult task was to reduce the radiation levels to a point that would permit the bodies to receive normal burial. Guided by radiation detectors, the doctors sliced away great swathes of skin and underlying tissue, but that wasn’t enough. With McKinley, the doctors had to remove his left arm. With Byrnes, they removed both legs. With Dick Legg, they had to go even further: They removed all four limbs and – after consultation with their superiors – his head, which was the most radioactive body part of all. All these removed body parts were packed in a drum, driven to a remote spot and dropped into a deep trench designated to receive high-level waste from the accident.

The remaining portions of the men’s bodies – just a limbless, headless torso in Legg’s case – were now prepared for burial. The bodies were coated in drying powder, wrapped in cotton and then in plastic sheeting. A final wrapping was done with lead sheeting – one-eighth of an inch thick for McKinley and Byrnes, three-quarters of an inch for Legg. More than a ton of lead was used for this purpose. Thus ensheathed, the bodies were placed in hermetically-sealed steel caskets that had been lined with more lead, and the caskets were placed within purpose-made lead vaults. Radiation levels outside the vaults were now reduced to levels well below 1 roentgen per hour, and the bodies were deemed safe for transport.

Eighteen days after the accident, military planes carried the vaults to airports near the intended burial grounds. McKinley’s family chose Arlington National Cemetery on account of his service in Korea, as well as a sense that he had died in service to his country. Byrnes and Legg were buried in cemeteries in New York and Michigan respectively.

The funerals were bizarre affairs. In each case, on the day before burial an extra-deep grave was excavated and a foot-thick layer of concrete was poured and allowed to harden, forming a pad. On the day of the funeral, the rites were limited to eight minutes, with the grieving family members standing at least 20ft away from the vaults. Legg’s family insisted on the casket being taken out of its vault for the rites. This caused radiation levels to double, and the service was limited to five minutes. The vaults were then lowered onto the pads and, after the families had left, more concrete was poured so that the vaults were completely encased in foot-thick concrete – two feet thick, in Legg’s case. Finally, the concrete was covered with several feet of earth.

In their effort to establish the cause of the accident, investigators took two main directions: interviews with SL-1 staff and administrators, and examination of the accident site. The staff interviews produced limited information. The only eyewitnesses to the accident were dead, after all. The workers who had shut down the reactor before the Christmas holiday described how three of the control rods refused to fall freely into the reactor core and had to be driven down. This sticking behaviour was much worse, they reported, than had been experienced earlier.

Engineers described another problem that had developed with the reactor over its two-year operating lifetime. As part of the reactor design, strips of boron had been attached to the fuel plates. Boron, like cadmium, is an efficient absorber of neutrons, and the strips had the function of helping prevent a runaway reaction and extending the life of the core. Nevertheless, the strips had begun to corrode and flake away from the fuel plates, leaving the reactor more excitable than it had been when it came online. Thus, the control rods didn’t have to be raised as far as they did previously in order to start the nuclear chain reaction.

Because of these and other problems that had developed with the SL-1 reactor, officials had planned to replace the entire reactor sometime during 1961. When the accident occurred, therefore, the reactor was being operated on borrowed time. The crews had to keep recalibrating the control rods, for example, to ensure that the control motors moved them up and down within the range that controlled the reactor core. Nevertheless, no one believed that the reactor was threatening to get out of control. There still seemed to be a large margin of safety built into the various operations required for starting, stopping, and running the reactor.

Officials described the background and training of McKinley, Byrnes, and Legg. Because McKinley was a new trainee, there was some suspicion that he might have done something to trigger the accident. Attaching the control rods to the drives – the task that the men were engaged in at the time of the accident – required the rods to be raised by hand by about four inches. Raising the central rod by more than about 16 inches would trigger a runaway chain reaction (a nuclear ‘excursion’, as it is called). Both Byrnes and Legg were well versed in the procedure and knew not to lift the rods beyond the permitted four inches. Could McKinley, out of ignorance, have pulled the central rod much farther out than that?

During the first few days of the inquiry, this scenario seemed especially plausible on account of an unfortunate circumstance: in the haste and confusion of the recovery, the bodies were misidentified. McKinley’s body was originally thought to be the one that was impaled in the reactor room ceiling. This would have meant that he was standing directly on top of the reactor at the time of the accident, where he could have been handling the central control rod. In the course of the autopsy, however, it became clear that McKinley was the man who was pulled out first – the man who was still alive at the time the rescuers arrived. This man had been at some distance from the reactor at the time of the accident, thus he could not have been handling any control rod. Once the bodies were correctly identified, the idea that the accident was the result of a trainee’s mistake fell apart.

Much more information was obtained from the reactor site. During the 11 months following the accident, workers gradually tore down the reactor building while carefully documenting every item that was found. Many of the items, including the control rods, were extremely radioactive. These were taken for study to a ‘hot lab’ on the Testing Station, where they could be handled, cut up and inspected with remotely-controlled instruments.

The investigators first wanted to establish whether or not a nuclear excursion had in fact occurred. The fact that radiation levels in the reactor building were so high did not compel that conclusion: the radiation came primarily from nuclear fuel that had been ejected from the reactor, but the fuel might have been ejected as the consequence of a chemical explosion or some other event within the reactor vessel. To resolve this issue, radiation technologists took one of the dead men’s wedding rings and dissolved it in acid. They found that some of the gold atoms in the ring had been converted from normal gold, 197AU, to radioactive gold, 198AU – a transition that occurs by capture of an extra neutron. Thus, the presence of 198AU was proof that there had been an intense flash of neutrons during the accident, and these neutrons must have been generated by an uncontrolled chain reaction within the reactor’s fuel elements.

The central control rod (minus its cadmium blade) was one of the early items to be recovered, because it was found lying directly on top of the reactor. Evidently it had fallen there after being violently ejected during the explosion and striking the reactor room ceiling. The blade had broken off and remained inside the reactor.

From the control rod, the investigators learned the exact moment in the proceedings when the accident occurred. To re-attach a control rod to its drive, the crew had to take the following steps, which formed an unvarying routine. First, they had to insert a handle into the top of the rod, effectively extending the rod by a couple of feet. Second, a crew member grasped the handle and raised the control rod by about four inches, while another worker attached a C-clamp to the rod. The rod was then lowered back down until the C-clamp rested against the housing through which the rod passed as it entered the reactor vessel. This held the rod in a fixed position for the following steps. The handle was removed and a nut and washer were attached to the top of the rod – these were required for attachment to the drive. Then the handle was reattached and a worker raised the rod just slightly – maybe a quarter of an inch -so that another worker could remove the C-clamp. The handle was removed, and the drive was connected to the top of the rod.

When it was recovered, the control rod had nothing attached to its top end. In fact, the very topmost part of the rod had been broken off and was missing. Then workers found this missing part in the attic above the reactor. Attached to this part was the washer and nut used for joining the rod to its drive, and attached to the washer and nut was the lifting handle.

The fact that the handle had been attached to the central control rod meant that the crew was working on this rod when the accident occurred. Furthermore, since the washer and nut were already in place between the handle and the rod, the workers must have already completed the first, four-inch, lift and attached the C-clamp and the washer and nut. They were now due to perform the second, tiny, lift that was required to release the C-clamp.

This wasn’t all that was learned from the central control rod. When it was found lying on top of the reactor, the rod still lay within its ‘shield plug’ – a kind of steel collar, normally fixed to the top of the reactor vessel, through which the rod could be moved up and down. Below the shield plug was fixed a ‘guide tube’: this formed a sheath around the rod, which moved up and down inside it. Evidently, the rod, the shield plug and the guide tube had been blown out of the reactor as a unit. When found, the rod was only slightly withdrawn from the plug, just as would be expected for the phase of the operation that was being performed at the time. This seemed to argue against the idea that someone had withdrawn the rod the 16 inches required to initiate a chain reaction in the core.

But quite a different story emerged when the rod and the plug were disassembled and examined microscopically. The control rod was peppered with small impact marks and scratches that had been caused by the explosion. So was the guide tube. It quickly became apparent that the individual marks on the guide tube could be lined up with corresponding marks on the control rod – but only if the top of the rod was withdrawn from the shield plug by 20 inches. Thus the rod must have been raised by that amount at the time of the explosion.

Apparently, someone or something had raised the rod much farther than was prescribed or permitted, and in fact four inches beyond the distance needed to set off an uncontrolled chain reaction. Evidently, when the rod/plug assembly was propelled violently against the ceiling, the tip of the rod (along with the handle) broke off, and the remainder of the rod was driven back down through the shield plug and guide tube, leaving it in a seemingly normal position.

The investigators confirmed the excessive withdrawal a few months later when workers were able to inspect the reactor core. The cadmium blade of the central control rod was trapped by the partially melted and deformed fuel plates, but it was 20 inches above its lowermost position. Thus the entire control rod assembly had been withdrawn by that distance at the time of the accident.

Why had the control rod been raised so far beyond the safe level – especially at a phase of the operation when it needed to be raised by only a fraction of an inch? The most obvious explanation was that the rod had become stuck, and a crew member – or two crew members working together – had tugged mightily to free it. Then, when the rod suddenly broke loose, they unintentionally pulled it far beyond the intended distance.

This scenario sounds entirely plausible: everyone has had similar experiences in the course of wrestling with balky mechanical devices, if not with such disastrous consequences. But could it really have happened at SL-1? To find out, the investigators built a replica of the control rod that could be locked and released at will. They had a large number of workers attempt to free the ‘stuck’ rod by pulling on it as hard as they could. When the rod was suddenly and unexpectedly released during the pull, none of the workers raised the rod more than about 10 inches. This was certainly an uncomfortably large distance, but it wasn’t enough to start an uncontrolled chain reaction in the core. The main reason that the rod didn’t come up very far when it was released was its weight of around 100lb. As soon as the workers’ initial effort slackened, it stopped dead or fell back.

The investigators considered another scenario, which was that one of the crew members had played a prank on the man who was tugging on the rod, perhaps by grabbing or pinching him in the rear. Might a reflex response have led the man to straighten up, causing him to pull the rod upward by 20 inches? To test this idea, the investigators actually perpetrated this prank on a number of men who were in the process of pulling on the mock-up rod. None of the men who were goosed in this way pulled the rod up by any extra distance, however.

Eventually, the identity of the crew member who raised the control rod became clear: It was Jack Byrnes. McKinley, as already mentioned, was not within reach of the rods when the accident occurred. Legg must have been crouching astride control rod number seven*,  one of the outer control rods, because this was the rod that ripped through his body, sending him rocketing upward and pinning him to the ceiling. Because of his crouched posture, he was far too low down to have been pulling on the central rod, but he was at an ideal height to detach the C-clamp from it. Furthermore, the pattern of radiation absorbed by the bodies of Legg and Byrnes confirmed that Legg was crouching down, whereas Byrnes was standing above the centre rod in the normal position for pulling on it.

All in all, it seemed clear that the accident happened because Jack Byrnes, an experienced operator, raised the central control rod too far, but the exact reason for his action remained obscure, at least in the official report. The investigators wrote that ‘the reason or motive for the abnormal withdrawal is considered highly speculative, and it does not appear at all likely that there will ever be any reason to change this judgment’.

Calling something ‘highly speculative’ is, of course, an invitation to speculation, and there has been plenty of that in the years since the SL-1 accident. For the most part, it has revolved around an unproven theory that Jack Byrnes perpetrated the explosion as a murder/suicide – his motive being to bring to an end a desperate love-triangle involving himself, his wife and his fellow crew member, Dick Legg.

Even while the original inquiry was going on, and radiation specialists were analysing the remains of the reactor, investigators were also checking into the backgrounds and family circumstances of the three dead men. None of their findings made it into the report, but they soon became the subject of gossip around the Testing Station. In July 1962, Leo Miazga, an investigator for the Atomic Energy Commission (AEC), filed a supplemental report describing what he had learned about the crew members and their families. Miazga’s report was never made public, but recently a copy was obtained by Colorado-based journalist William McKeown, who wrote a book about the SL-1 accident.

According to McKeown, Miazga’s report documented the breakdown of Jack and Arlene Byrnes’s marriage. Jack had been spending less and less time at home, and on the evening of the accident he had taken his personal items with him in his car as if he was moving out. When Arlene called Jack at work later that evening, it was to discuss ending their marriage. Thus Jack Byrnes may have been in a distracted mood – or worse – during the later part of the work shift.

Miazga did not find evidence to link Dick Legg to Arlene. Still, it was clear that Byrnes and Legg did not get along. In fact, they had engaged in a drunken fistfight during a bachelor party in May 1960, eight months before the accident.

The first that the wider public heard about a possible love triangle as the cause of the accident was in 1979, when a Vermont newspaper, the Brattleboro Reformer, ran a story about an AEC memo on the topic of nuclear safety. The memo had been written in 1971 by Stephen Hanauer, then an AEC staff member. Hanauer had cited the love-triangle story to illustrate the notion that nuclear-reactor accidents could be caused by internal sabotage. Hanauer’s memo was leaked to the Reformer by Robert Pollard, a nuclear regulator who became an antinuclear campaigner. The Reformer’s story was picked up by the national press, and two years later a television documentary about the accident mentioned the love-triangle theory. McKeown’s book gives it a great deal of play without drawing any firm conclusions. When I spoke with Stephen Hanauer, now retired, in 2005, he portrayed the love triangle as a mere piece of gossip that he had picked up, not something that was backed by any kind of solid evidence.

There always will be the temptation to attribute accidents to the foibles of individuals – especially deceased individuals – because doing so may be seen as relieving planners, designers and administrators from responsibility. A case somewhat similar to the SL-1 accident occurred in 1989, when an explosion destroyed a gun turret on the US battleship Iowa during training exercises, killing 47 sailors. The Navy initially called the explosion a suicidal act by one of the gunners, Clayton Hartwig, who was said to have been depressed because a sexual relationship with another sailor had gone sour. Later, the evidence for this explanation fell apart, and the Navy apologised to Hartwig’s family. The explosion was probably caused by accidental over-ramming of the gun’s propellant charges, perhaps combined with faulty packing of the charges.

Whatever the reason why Jack Byrnes raised SL-1’s central control rod so far, it was quickly recognised that allowing the movement of a single control rod to trigger an uncontrolled nuclear chain reaction was a serious design flaw. This flaw came about primarily on account of the small size of the SL-1 reactor, which used a total of only five control rods. Every subsequent reactor design has required the lifting of several control rods to cause a runaway reaction. Still, even with such reactors it is possible to trigger nuclear excursions by inappropriate lifting of multiple rods. In fact, an accident of that kind happened in Canada nine years before the SL-1 accident. During a crisis triggered by other events, an operator at the Chalk River reactor in Ontario erroneously pressed a button that raised several banks of control rods. As a result, a nuclear excursion began that blew the four-ton lid of the reactor vessel into the roof of the building. The accident contaminated the entire plant, but no one was killed.

The worst reactor accident in the United States, the partial core meltdown at the Three Mile Island reactor in Pennsylvania in 1979, was caused by loss of coolant to the core, not by problems with the control rods. There was only an insignificant release of radioactivity to the environment, and no one was killed or injured. The world’s worst nuclear power plant accident – and the only accident at a commercial plant that has ever resulted in radiation-induced deaths – was the 1986 disaster at the Chernobyl-4 reactor in Ukraine. This was caused by operator errors during a test of the reactor’s response to a loss of electrical power supply, combined with design deficiencies. More than 50 people – mostly emergency workers – died of radiation injuries in the aftermath of the accident. Some experts believe that larger numbers of people in the general population are dying or will die from radiation-induced illnesses.

The SL-1 accident may have had other victims. Hazel Leisen, the nurse who tended to Richard McKinley while he was in the ambulance, died of cancer a few years after the accident. Ed Vallario, the health physicist who led the rescue attempt, and two of his helpers, also died of cancer, although Vallario didn’t fall ill until more than 30 years after the accident. The statistics of small numbers don’t permit any firm conclusion as to whether or not the four cancer deaths resulted from the radiation exposure these individuals received in 1961.