SL-1: The Nuclear Disaster America Wants You to Forget

In January 1961, three young men walked into a small nuclear reactor building in the Idaho desert. They were doing routine maintenance: reconnecting control rods, checking systems, preparing for a restart. The kind of work they’d done dozens of times before.

They never walked out.

What happened inside that building, in just four thousandths of a second, would kill all three of them instantly. It would send firefighters rushing across frozen highways into radiation fields so intense their meters nearly maxed out. It would scatter radioactive debris across the facility and release a cloud of contaminated gas that drifted over the surrounding desert.

And here’s the thing: you’ve probably never heard of it.

The SL-1 incident remains the only nuclear reactor accident in American history to kill people on the spot. Not Three Mile Island. Not any of the dozens of other reactors that have had problems over the decades. Just this one. A tiny experimental reactor in the middle of nowhere, operated by a handful of twenty-somethings, gone catastrophically wrong on a freezing January night.

The immediate cause is clear enough: a single control rod, pulled too far, too fast. But why it was pulled that far—that’s where things get complicated. Investigators would spend years piecing together what happened. They’d examine the wreckage, interview witnesses, reconstruct the physics down to the millisecond. And in the end, they’d have to admit they couldn’t say for certain what actually went wrong in that room.

What they could say was this: the reactor’s design was flawed, the procedures were inadequate, and the institutional culture that allowed those problems to fester was a disaster waiting to happen.

This is the story of SL-1: the deadliest nuclear accident in American history, and the one almost nobody remembers.

Desert Proving Ground

To understand what happened at SL-1, you first need to understand where it happened, and why anyone thought putting experimental nuclear reactors in the Idaho desert was a good idea in the first place.

In 1949, the federal government carved out a massive chunk of the Snake River Plain, about forty miles west of Idaho Falls. Nearly 890 square miles of sagebrush, lava rock, and not much else. They called it the National Reactor Testing Station, and the whole point was isolation. If you’re going to test experimental reactors, the kind that might fail in spectacular and unpredictable ways, you want them as far from population centres as possible. Eastern Idaho fit the bill perfectly.

By 1961, more than 30 different reactors had operated at this site, everything from early breeder reactors to compact military units designed for submarines and remote bases. The Army, in particular, had big plans. Their Nuclear Power Program envisioned small, portable reactors that could heat and power Arctic radar stations along the DEW Line, those early warning installations scattered across Alaska and northern Canada watching for Soviet bombers. The Navy had nuclear submarines, the Air Force was experimenting with nuclear-powered aircraft—the Army wanted its piece of the atomic future too.

SL-1, originally called the Argonne Low Power Reactor, was built to prove the concept. A tiny reactor, small enough to transport by air, designed to generate just enough electricity and heat to keep a remote outpost running. Nothing flashy, nothing particularly powerful. Just a proof of concept sitting in the desert alongside dozens of other experimental machines, waiting to show what it could do.

A Tiny, Dangerous Machine

Now, let’s talk about the reactor itself, because the design choices made here matter enormously for understanding what went wrong.

SL-1 was a boiling-water reactor, which means water flows through the core, gets heated by nuclear fission, boils into steam, and that steam drives a turbine to generate electricity. Same basic principle as the massive commercial plants that would later power cities across America, just shrunk down to fit inside a cylindrical steel building you could transport by cargo plane. The whole thing was designed to produce about 3 megawatts of thermal energy, which translated to roughly 200 kilowatts of electricity and 400 kilowatts of heat. Enough to run a remote radar station, not enough to worry about.

Here’s where it gets interesting. To keep the reactor small and portable, the designers made some compromises. The core used highly enriched uranium fuel in just 40 of the 59 available positions, which concentrated most of the reactivity toward the centre. Control came from five rods, and one of them, the central rod known as Rod 9, had an outsized influence on the reactor’s behaviour. Move that rod, and you moved the needle on reactor power more than any other single component.

You see the problem? In later reactor designs, there’s a fundamental safety principle called the “one stuck rod” criterion, which basically says no single control rod should ever be capable of making the reactor go critical by itself. If one rod gets stuck, or someone pulls it too far, the reactor should still remain safely shut down. SL-1 didn’t meet that standard—because that standard didn’t exist yet. Pull Rod 9 far enough, and you could send the whole reactor into a runaway chain reaction in milliseconds.

Training, Trouble, and Thin Oversight

The reactor had design problems, but it also had operational problems—and those were arguably just as dangerous.

SL-1 was operated by Combustion Engineering, a civilian contractor working for the Atomic Energy Commission, but the day-to-day crews were military personnel, mostly Army specialists with some Navy electricians mixed in. These were young men, generally in their early twenties, trained on-site to run a reactor that was supposed to be simple enough for small teams to operate in remote Arctic conditions. The training was adequate for routine operations, but the procedures themselves were sparse by modern standards. We’re talking brief checklists and informal guidance, not the hundreds of pages of step-by-step instructions that would later become standard at nuclear facilities.

And the reactor kept misbehaving. Control rods stuck periodically and had to be freed by maintenance crews. Unexplained automatic shutdowns, called scrams, happened often enough that operators started treating them as routine annoyances rather than warning signs. Contamination levels inside the building crept upward over time.

Any one of these issues might have prompted a serious investigation and shutdown at a facility with more rigorous oversight, but SL-1 was a small experimental reactor in the middle of the desert, staffed by a skeleton crew working long hours with minimal supervision. Problems got logged, maybe discussed, and then everyone moved on to the next shift. The culture wasn’t reckless exactly—it was just stretched thin, normalising small failures until they stopped looking like failures at all.

Three Men on the Night Shift

On the evening of January 3rd, 1961, three men reported for the night shift at SL-1. The reactor had been shut down for eleven days over the holiday period, and their job was to get it ready for a restart scheduled for the following day.

Army Specialist John Byrnes was 22 years old, the designated reactor operator for the shift. Navy Electrician’s Mate First Class Richard Legg, at 26, served as shift supervisor and was the most experienced of the three. And Army Specialist Richard McKinley, 27, was an operator in training, there to learn the procedures and assist where needed. Three young servicemen, none of them over 30, doing maintenance work on a cold Tuesday night in the middle of the Idaho desert.

The task itself was straightforward, at least on paper. During shutdown, the control rods had been disconnected from their drive mechanisms, and the crew needed to reconnect them before the reactor could be brought back online. This meant manually lifting certain rods a few inches to re-engage them with the motorised drives that would control them during normal operation. The procedures specified that the central rod, Rod 9, should be lifted about four inches to reconnect it—no more than that.

Four inches was enough to latch the rod to its drive. Four inches was safe. What the crew may not have fully understood, and what their supervisors arguably should have made clearer, was just how little margin for error that central rod actually allowed.

Four Milliseconds to Disaster

At 9:01 p.m., something went catastrophically wrong.

Investigators would later reconstruct the sequence from physical evidence—scratches on the rod, damage patterns in the core, the position of debris. Their conclusion: instead of lifting the central control rod the prescribed four inches, someone pulled it roughly twenty inches. And twenty inches was more than enough to kill everyone in that room.

Here’s what happens when you withdraw a control rod too far, too fast, from a reactor like SL-1. Normally, a nuclear chain reaction is moderated by what physicists call “delayed neutrons,” particles released a few seconds after fission that give operators time to respond to changes. But if you add too much reactivity too quickly, the reaction stops waiting for those delayed neutrons and starts sustaining itself on “prompt” neutrons alone, the ones released instantly during fission. That’s called going prompt critical, and when it happens, power doesn’t rise gradually—it rises exponentially, faster than any human or mechanical system can respond.

In SL-1’s case, the reactor jumped from essentially zero power to nearly 20 gigawatts in about four milliseconds. To put that in perspective, 20 gigawatts is roughly twenty times the output of a large commercial nuclear plant, and it all happened in less time than it takes to blink. The water surrounding the fuel didn’t boil—it flashed to steam almost instantaneously, creating a pressure spike of around 10,000 pounds per square inch. That pressure launched the entire reactor vessel upward, shearing pipes and blasting superheated water, steam, and radioactive debris into the operating room above. The core itself partially melted and vaporised, releasing about 80 curies of iodine-131 and roughly 1,100 curies of mixed fission products into the building and, eventually, into the atmosphere.

Four milliseconds. That’s all it took.

Fire Alarm in the Frozen Night

Minutes after the explosion, a heat alarm triggered at the NRTS security station several miles away. A crew of firefighters climbed into their truck and headed out across Highway 20 in sub-zero temperatures, driving through the frozen darkness toward SL-1. They weren’t particularly worried—the alarm system had already malfunctioned twice earlier that day, and false alarms were common enough at the testing station that nobody assumed the worst.

When they reached the SL-1 support building, everything looked almost normal. The lights were on, jackets hung on their hooks, and three coffee cups sat on a table, still warm. But the men who’d been drinking that coffee were nowhere to be found. The firefighters called out, got no response, and started climbing the stairs toward the reactor room above.

That’s when their radiation meters started climbing too.

The readings spiked toward the top of the scale as they approached the reactor level, some instruments showing levels approaching 25 roentgens per hour, which was close to their maximum reading. The responders pushed forward anyway, and what they found inside was chaos—two men lying motionless on the floor, and a third faintly moaning nearby. Without fully understanding what they were walking into, the rescuers dragged the injured man out of the building and loaded him into an ambulance.

He would die before reaching the hospital. The ambulance itself was so badly contaminated that it had to be buried as radioactive waste. And the responders who’d rushed in to help received whole-body radiation doses as high as 27 roentgens, well below immediately fatal levels but significant enough to raise their long-term cancer risk.

Some areas of the reactor room, they would later discover, had radiation fields exceeding 800 roentgens per hour.

The Invisible Cloud

So what actually got released into the environment? That depends on who you ask.

The official numbers from the Atomic Energy Commission put the atmospheric release at about 80 curies of iodine-131 and roughly 1,100 curies of mixed fission products. Health physics teams fanned out across the site in the hours and days after the accident, taking air samples and measuring contamination on buildings and equipment. They found elevated iodine levels on nearby structures, some readings running as high as 50 times normal background, but the AEC maintained that offsite air concentrations remained well below federal safety guidelines. The remote location, they argued, had done its job—the desert absorbed most of the contamination before it could reach populated areas.

The workers were another story. Twenty-two people involved in the initial emergency response and early recovery efforts received whole-body radiation exposures between roughly 3 and 27 roentgens, and hundreds more who participated in the months-long cleanup had measurable contamination on their bodies or clothing. These weren’t trivial doses, even if they fell short of causing immediate radiation sickness.

But here’s where things get contested. Critics, including groups like the Environmental Defense Institute, argue that the AEC’s release estimates were badly underestimated, either through measurement limitations or deliberate downplaying. They point to elevated thyroid cancer rates in eastern Idaho and argue that thousands of downwind residents were exposed to radioactive gases that official reports minimised.

Federal dose-reconstruction studies conducted decades later generally support the lower estimates, concluding that public exposures were modest compared to, say, atmospheric weapons testing fallout. The disagreement hasn’t been fully resolved, and it continues to fuel debates over worker compensation and institutional trust to this day.

Recovery in a Hot Zone

Cleaning up the mess took more than a year and required inventing new ways to work in intensely radioactive environments.

General Electric won the contract to dismantle SL-1, and roughly 475 people participated in the recovery operation over the following months. The challenges were unlike anything most of them had faced before. Radiation levels inside the reactor building remained dangerously high, which meant workers could only spend minutes at a time in certain areas before reaching their exposure limits.

Engineers improvised remote-handling tools, built specially shielded cranes with thick steel walls and lead glass viewing windows, and developed rotation schedules that spread the dose across as many workers as possible. The reactor vessel itself had to be cut free from its mountings and hauled to a hot-cell facility for detailed forensic analysis, a painstaking process that required weeks of careful work.

The contaminated debris, along with irradiated soil from around the building, was buried on-site in a fenced disposal area that remains capped and monitored to this day. And then there was the matter of the three operators. Their remains were so heavily contaminated that standard burial wasn’t an option. Richard McKinley, the trainee who’d been pulled from the reactor room and died in the ambulance, was eventually interred at Arlington National Cemetery in a lead-lined casket encased in concrete, a precaution necessary to contain the radioactivity still present in his body.

The other two men were buried under similar constraints elsewhere. Even in death, the accident refused to let them go.

Who—or What—Was to Blame?

The investigation answered the “what” fairly quickly. The “why” has never been fully resolved.

Atomic Energy Commission investigators spent months analysing the wreckage, reconstructing the physics of the accident, and interviewing everyone who might have relevant information. Their conclusion on the technical cause was unambiguous: the central control rod had been withdrawn approximately 20 inches instead of the 4 inches specified in the maintenance procedure, and that excessive withdrawal triggered the prompt criticality that destroyed the reactor. The scratches on the rod, the damage patterns in the core, the position of debris—all of it pointed to the same sequence of events. What the evidence couldn’t tell them was why the rod moved that far.

Four theories emerged over time, and none of them has ever been definitively proven or ruled out. The first and simplest explanation is operator error, that Byrnes, who was standing on top of the reactor and physically lifting the rod, simply pulled too hard or lost his grip and yanked it further than intended. The second theory suggests he may have been deliberately “exercising” a sticky rod, pulling it up and down to free a mechanism that had been giving trouble, and misjudged the movement.

The third and fourth theories are darker—some investigators quietly explored the possibility that one of the operators deliberately caused the accident, either as an act of sabotage, suicide, or even murder-suicide. Rumours circulated about personal tensions among the crew, including allegations of a love triangle involving two of the men and a woman back in Idaho Falls.

The Army leaned publicly on “human error” without elaborating, and popular retellings have often repeated the more sensational theories as though they were established fact. They weren’t. Investigators found no conclusive evidence of intent, no suicide note, no definitive proof of the rumoured personal conflicts.

Modern historians like Todd Tucker, who obtained extensive documents through Freedom of Information requests, argue that focusing on operator behaviour misses the larger picture anyway—that design flaws and inadequate procedures created a situation where a single mistake, or even a single stuck rod, could kill three people in milliseconds. The official report ultimately acknowledges that the precise actions and motivations of the operators in those final moments cannot be determined with certainty.

Aftermath for Families and “Downwinders”

The three men who died at SL-1 left behind families who found themselves navigating grief in an information vacuum.

Communication from the Army and the Atomic Energy Commission was heavily filtered from the start. The widows received condolences and death benefits, but basic details about what had actually happened to their husbands remained classified for years. Autopsy results, burial procedures, the nature of the injuries—all of it was wrapped in secrecy, ostensibly for national security reasons but also, critics would later argue, to protect the nuclear program from embarrassing scrutiny. The families were left to mourn without fully understanding what they were mourning, piecing together fragments of information from official briefings that raised more questions than they answered.

For the broader community in eastern Idaho, the official message was reassurance. The release was minor, the authorities said. The remote location had contained the contamination. There was no significant risk to public health. And for decades, most people accepted that at face value.

But as thyroid cancer rates in the region drew attention in later years, some residents began connecting dots—or at least suspecting connections. SL-1 wasn’t the only nuclear activity in their backyard. The Idaho testing station had hosted dozens of experimental reactors over the decades, and atmospheric weapons tests in Nevada had sent fallout drifting across the region throughout the 1950s.

Activists and researchers started using the term “downwinders” to describe communities they believed had been exposed and forgotten, echoing similar fights by residents near the Nevada test site who’d won federal recognition and compensation. The Environmental Defense Institute and other groups argued that SL-1’s releases had been systematically underestimated and that the true health toll would never be known because nobody had bothered to track it properly.

Federal dose-reconstruction studies have generally pushed back on these claims, concluding that SL-1’s offsite exposures were low compared to weapons-test fallout and unlikely to have caused significant excess cancers. But for many locals, those studies came from the same institutions that had told them not to worry in the first place. The distrust runs deep, and it hasn’t gone away.

The Other “Worst” Nuclear Disaster

When I called SL-1 the deadliest nuclear reactor accident in American history, I meant something very specific—it’s the only one that killed people immediately, on the spot, from the direct effects of the accident itself. But “deadliest” is a slippery word, and depending on how you count, other incidents might claim that title.

Take Santa Susana, for example. In 1959, two years before SL-1, a reactor called the Sodium Reactor Experiment at the Santa Susana Field Laboratory near Los Angeles suffered a partial meltdown. Nobody died that day, and the incident was kept quiet for decades, but the reactor released radioactive gases that drifted over the suburbs of the San Fernando Valley.

An independent advisory panel convened years later estimated that contamination from Santa Susana, including the 1959 meltdown and other releases, might have contributed to roughly 260 excess cancer deaths in the surrounding communities. That’s a modelled estimate, not a body count, and other studies commissioned by the government and Boeing, which operated the facility, found weaker or no clear evidence of elevated cancer rates nearby. The science remains contested, but if those higher estimates are accurate, Santa Susana’s long-term toll would far exceed SL-1’s three immediate fatalities.

And then there’s Three Mile Island, the 1979 partial meltdown at a commercial reactor in Pennsylvania that became the defining nuclear accident in American public consciousness. TMI released considerably more radioactivity than SL-1, though most of it was contained within the reactor building, and extensive studies have found no confirmed radiation-related deaths among workers or the public. What TMI killed was public trust in nuclear power. The industry effectively stopped building new plants in the United States for decades afterward, a policy shift with enormous implications for energy and climate that continues to shape debates today.

So which one was “worst”? It depends entirely on what you’re measuring.

Writing Safety Rules in Blood

There’s an old saying in engineering that safety regulations are written in blood, and SL-1 wrote quite a few of them.

The most fundamental change was the formalisation of something now called the “one stuck rod” criterion. Remember how SL-1’s central control rod could, by itself, make the reactor go prompt critical if withdrawn far enough? That’s no longer allowed. Modern reactor designs must demonstrate that even if their single most reactive control rod is fully withdrawn or stuck in the out position, the reactor will remain safely shut down.

This requirement is baked into the design criteria that every new reactor must meet, and it traces directly back to what happened in the Idaho desert in 1961. Engineers looked at SL-1 and said, essentially, “never again.”

Procedurally, the changes were just as dramatic. Those brief, informal checklists that SL-1 operators worked from gave way to multi-hundred-page, line-by-line procedure manuals that specify exactly what to do, in what order, under what conditions, with sign-offs and independent verifications at critical steps. Training programs expanded enormously, and independent safety review teams became standard at nuclear facilities. If a procedure seemed adequate but hadn’t been thoroughly documented and reviewed, that was no longer acceptable.

Even the radiation instruments got redesigned. The meters that first responders carried into the SL-1 building maxed out at relatively low readings, leaving them effectively blind in exactly the conditions where they most needed accurate information. After the accident, instrument manufacturers developed equipment capable of measuring much higher dose rates, so that incident commanders could actually assess the hazards their people were walking into.

All of these changes, taken together, helped make later accidents less deadly than they might otherwise have been. Three Mile Island was a disaster, but nobody died from radiation exposure—and SL-1’s lessons were part of the reason why.

Small Reactors, Long Shadows

Here’s an interesting bit of historical rhyming: the same ideas that birthed SL-1 are making a comeback.

Small modular reactors and microreactors are suddenly hot topics in the energy world, with startups and government agencies alike promising compact, flexible nuclear plants that can be factory-built and shipped to remote locations. The U.S. military is actively developing portable reactors again through programmes like Project Pele, aiming to power forward operating bases without the logistical nightmare of trucking in diesel fuel. NASA is exploring nuclear power for lunar bases.

And where are many of these new designs being tested? Idaho National Laboratory—the same site where SL-1 once stood, now hosting projects like MARVEL, a microreactor experiment whose environmental assessment explicitly references the lessons learned from the 1961 accident.

Proponents of modern small reactors argue, with some justification, that today’s designs are fundamentally different. They use passive safety features that don’t rely on human operators or powered systems to prevent meltdowns, inherently safe fuel forms that can’t reach dangerous temperatures, and control systems designed from the ground up with the one-stuck-rod criterion and dozens of other post-SL-1 requirements baked in. A modern microreactor, they’ll tell you, simply cannot do what SL-1 did.

And that’s probably true—for the physics, anyway. But physics was only part of what went wrong in 1961. SL-1 also failed because of inadequate procedures, stretched-thin oversight, normalised maintenance problems, and an institutional culture that prioritised keeping the reactor running over asking hard questions about whether it should be running at all. Those aren’t physics problems.

They’re human problems. And humans haven’t changed nearly as much as reactor designs have. The burial ground where SL-1’s contaminated debris lies is still out there in the Idaho desert, still fenced, still monitored. Every new reactor built at that site goes up in its shadow.

Key Takeaways

• SL-1 remains the only U.S. nuclear reactor accident to kill people instantly, yet remains largely unknown compared to Three Mile Island.
• The central control rod was pulled 20 inches instead of 4, causing prompt criticality and a 20-gigawatt power spike in four milliseconds.
• Investigators could not determine why the rod was pulled too far; theories range from operator error to deliberate sabotage, none proven.
• The accident led to the ‘one stuck rod’ safety criterion, extensive procedural reforms, and redesigned radiation instruments for responders.
• Modern small modular reactors are being tested at the same Idaho site, raising questions about whether human factors have improved enough.

Frequently Asked Questions

What was SL-1 and where was it located?

SL-1 was a small experimental boiling-water nuclear reactor originally called the Argonne Low Power Reactor, located at the National Reactor Testing Station in the Idaho desert, about forty miles west of Idaho Falls. It was designed to be small enough to transport by air and generate enough electricity and heat to power a remote Arctic radar station.

What happened during the SL-1 accident on January 3, 1961?

At 9:01 p.m., during routine maintenance to reconnect control rods after an eleven-day shutdown, the central control rod (Rod 9) was pulled approximately 20 inches instead of the specified 4 inches. This caused the reactor to go prompt critical, jumping from zero to nearly 20 gigawatts in about four milliseconds. The resulting pressure spike of around 10,000 psi launched the reactor vessel upward, killing all three operators instantly and releasing radioactive debris and gases.

Who were the three men killed in the SL-1 accident?

The three men were Army Specialist John Byrnes (22), the designated reactor operator; Navy Electrician’s Mate First Class Richard Legg (26), the shift supervisor and most experienced of the three; and Army Specialist Richard McKinley (27), an operator in training.

What made SL-1’s design particularly dangerous?

SL-1’s design concentrated most reactivity toward the center of the core using highly enriched uranium fuel in just 40 of 59 positions. Most critically, the central control rod (Rod 9) had an outsized influence on reactor behavior—withdraw it far enough and the reactor could go prompt critical by itself. This violated what later became the ‘one stuck rod’ safety criterion, which states that no single control rod should ever be capable of making a reactor go critical by itself.

What were the environmental and health consequences of the SL-1 accident?

The accident released about 80 curies of iodine-131 and roughly 1,100 curies of mixed fission products. Twenty-two emergency responders received whole-body radiation exposures between roughly 3 and 27 roentgens. Some areas of the reactor room exceeded 800 roentgens per hour. The Atomic Energy Commission maintained offsite air concentrations remained below safety guidelines, though critics like the Environmental Defense Institute argue releases were underestimated and may have contributed to elevated thyroid cancer rates in eastern Idaho.

How was the SL-1 cleanup conducted?

Cleanup took more than a year and involved roughly 475 people. Workers could only spend minutes at a time in certain areas due to high radiation. Engineers improvised remote-handling tools, built specially shielded cranes with lead glass viewing windows, and developed rotation schedules to spread radiation exposure. Contaminated debris and irradiated soil were buried in a fenced, capped, and monitored disposal area.

The three operators’ remains were so heavily contaminated they required lead-lined caskets encased in concrete for burial.

What theories exist about why the control rod was pulled too far?

Four theories emerged, none definitively proven: (1) operator error—Byrnes simply pulled too hard or lost his grip; (2) deliberately ‘exercising’ a sticky rod that had been malfunctioning; (3) sabotage; or (4) suicide or murder-suicide, with rumors of personal tensions including an alleged love triangle. Investigators found no conclusive evidence of intent. Modern historians argue focusing on operator behavior misses the larger picture of design flaws and inadequate procedures that created the dangerous situation.

What safety changes resulted from the SL-1 accident?

The most fundamental change was formalization of the ‘one stuck rod’ criterion, requiring that no single control rod can make a reactor go prompt critical. Procedures evolved from brief informal checklists to multi-hundred-page manuals with sign-offs and independent verifications. Training programs expanded, independent safety review teams became standard, and radiation instruments were redesigned to measure much higher dose rates so responders wouldn’t be ‘blind’ in high-radiation conditions.

How does SL-1 compare to other nuclear accidents like Three Mile Island and Santa Susana?

SL-1 is the only U.S. nuclear reactor accident to kill people immediately on the spot from direct accident effects (3 fatalities). The 1959 Santa Susana partial meltdown had no immediate deaths but may have contributed to roughly 260 excess cancer deaths by independent estimates. Three Mile Island (1979) released more radioactivity but caused no confirmed radiation-related deaths—its main impact was destroying public trust in nuclear power and halting new plant construction. Which was ‘worst’ depends on what is being measured.

What connections exist between SL-1 and modern small reactor development?

The same concepts behind SL-1—small, portable reactors for remote locations—are experiencing renewed interest through small modular reactors, microreactors, the military’s Project Pele, and NASA’s lunar base plans. Many are being tested at Idaho National Laboratory, the same site where SL-1 stood. Modern designs incorporate passive safety features and the one-stuck-rod criterion. However, proponents note that while physics has changed, the human factors that contributed to SL-1—inadequate procedures, stretched oversight, normalized maintenance problems—remain relevant concerns.

Sources

• Original Into the Shadows video: SL-1: The Nuclear Disaster America Wants You to Forget
• Hero image source by openverse, cc0.

Related Coverage