It was August 13, 1945, and the “Demon Core” was ready, waiting to be unleashed on a stunned Japan still reeling in fresh chaos from the deadliest attacks anyone had ever seen.
A week ago, ‘Little boy’ had exploded over Hiroshima, quickly followed by ‘Fat man’ in Nagasaki.
These were the first and only atomic bombs ever used in warfare, claiming as many as 200,000 lives – and if things had turned out differently, a third fatal blow would have followed.
But history had other plans.
After Nagasaki proved that Hiroshima was no accident, Japan immediately surrendered on August 15, with Japanese radio broadcasting a recorded speech by Emperor Hirohito giving in to Allied demands.
Recreation of the 1945 accident. (Los Alamos National Laboratory)
As it turns out, this was the first time the general Japanese public had ever heard the voice of one of their emperors, but for scientists at the Los Alamos Laboratory in New Mexico – aka Project Y – The event had a more urgent meaning.
It meant the functional Heart of the third atomic bomb They had been working on it – a 14-pound sphere of refined plutonium and gallium – that wasn’t needed for the war effort after all.
If the conflict had still raged, as it had for almost five straight years, that plutonium core would have been fitted into a second Fat Man assembly and detonated over another unsuspecting Japanese city just four days later.
As it was, fate granted these souls a reprieve and the device of Los Alamos – codenamed ‘Rufu’ at this time – would be retained at the facility for further testing.
During these tests, the remaining atomic bomb that eventually became known as the Demon Corehas earned this name.
Daghlian’s burned, blistered hand. (Los Alamos National Laboratory)
The first accident occurred less than a week after the surrender of Japan and just two days after the date of the aborted bombing of the Demon Core.
This mission may never have started, but the demon core stranded in Los Alamos still found an opportunity to kill.
Los Alamos scientists knew the risks of their approach when they performed criticality experiments on it – a means of measuring the threshold at which the plutonium would become supercritical, the point at which a nuclear chain reaction would unleash a blast of deadly radiation.
The trick of scientists in the Manhattan project — which included the Los Alamos Lab — to figure out how far one could go before triggering this dangerous reaction.
They even had an informal nickname for the high-risk experiments, hinting at the dangers of their actions. You named it “Tick the Dragon’s Tail”knowing that if they were unlucky enough to awaken the enraged beast, they would be cremated.
Louis Slotin, left, with the First Atomic Bomb Assembly, Gadget (Los Alamos National Laboratory)
And that’s exactly what happened to the physicist from Los Alamos Harry Daghlian.
On the night of August 21, 1945, after dinner, Daghlian returned to the lab to tickle the dragon’s tail alone – with no other scientists (just a guard) around, in violation of safety protocols.
As Daghlian worked, he surrounded the plutonium sphere with stones made of tungsten carbide, which reflected the neutrons emitted by the core onto them, bringing them closer to the critical point.
Brick by brick, Daghlian built these reflective walls around the core until his neutron monitoring equipment indicated that if he placed any more, the plutonium would become supercritical.
He moved to pull one of the stones away, but in the process accidentally dropped it right onto the top of the sphere, invoking Hypercriticality and creating a glow of blue light and a heat wave.
Recreation of the 1946 accident. (Los Alamos National Laboratory)
Daghlian immediately reached out and removed the stone, feeling a tingling sensation in his hand.
Unfortunately it was already too late.
In that brief moment he had received a lethal dose of radiation. His burned, irradiated hand blistered and he eventually fell into a coma after weeks of nausea and pain.
He was dead just 25 days after the accident. The security guard on duty also received a non-lethal dose of radiation.
But the demon core wasn’t ready yet.
Despite a review of safety procedures following Daghlian’s death, any changes made were insufficient to prevent a similar accident the following year.
Recreation of the 1946 accident. (Los Alamos National Laboratory)
On May 21, 1946, one of Daghlian’s colleagues, physicist Louis Slotindemonstrated a similar criticality experiment in which a beryllium dome was lowered over the core.
Like the tungsten carbide bricks before it, the beryllium dome reflected neutrons back toward the core, pushing it toward criticality. Slotin was careful to ensure the dome — called the tamper — never fully covered the core, using a screwdriver to maintain a small gap that acted as a crucial valve to allow enough neutrons to escape.
The method worked until it didn’t.
The screwdriver slipped and the dome fell, momentarily completely covering the demon core with a beryllium bubble that bounced back too many neutrons.
Another scientist in the room Ram writerturned as the dome collapsed, felt heat and saw a flash of blue as the demon core went supercritical for the second time in a year.
Diagram of the 1946 accident. (Los Alamos National Laboratory)
“The blue flash was clearly visible in the room, even though it (the room) was well lit by the windows and possibly overhead lights,” Schreiber later said wrote in a report.
“The total duration of the flash could not have been more than a few tenths of a second.
Slotin might have been quick to correct his fatal mistake, but again, the damage was already done.
He and seven others in the room – including a photographer and a security guard – were all exposed to a burst of radiation, although Slotin was the only one to receive a lethal dose, and a larger one than that inflicted on Daghlian.
After an initial bout of nausea and vomiting, he initially appeared to be recovering in hospital, but within days he was losing weight, suffering from abdominal pain and showing signs of mental confusion.
Operation Crossroads. (US Department of Defense)
A press release from Los Alamos at the time described his condition as “three-dimensional sunburn”.
Nine days after the screwdriver slipped off, it was gone.
The two fatal accidents, just months apart, eventually led to real change at Los Alamos.
New protocols spelled an end to “hands-on” criticality experiments, in which scientists were forced to use remote-controlled machines to manipulate radioactive nuclei hundreds of meters away.
They also stopped calling the plutonium core “Rufus.” From then on it was known only as the “Demon Core”.
But after everything that had happened, the time of the remaining atomic bomb had also expired.
After the Slotin accident – and the resulting increase in radiation levels in the core – there are plans to use it Operation Crossroadsthe first post-war nuclear blast demonstrations, which began a month later at Bikini Atoll, were shelved.
Instead, the plutonium was melted down and reintegrated into the US nuclear stockpile to be recast into other cores when needed. For the second and final time, the Demon Core was denied detonation.
While the deaths of two scientists can’t compare to the untold horrors if the Demon Core had been used in a third nuclear attack on Japan, it’s also easy to see why scientists gave it that superstitious name.
Then there are the odd details that fill in the background of the story.
For example, how Daghlian and Slotin were not only killed by similar accidents involving the same plutonium core: both incidents took place on Tuesdayon the 21st day of the month, and the men even died in the same sickroom.
Of course, these are just coincidences. The demon core wasn’t actually demonic. If there’s an evil presence here, it’s not at its core, but the fact that humans rushed to create these horrifying weapons in the first place.
And the real horror – aside from the horrifying effects of radiation poisoning – is how spectacularly scientists in the mid-20th century failed to protect themselves from the extreme dangers they were toying with, despite knowing full well the serious risks in their midst .
According to the scribeSlotin’s first words immediately after the screwdriver incident were simple and already resigned.
He had comforted his dying friend Daghlian in the hospital and he knew what was coming next.
“Well,” he said, “that’s enough.”
A version of this post was first published in 2018.
