{"id":225942,"date":"2026-01-11T12:14:03","date_gmt":"2026-01-11T18:14:03","guid":{"rendered":"https:\/\/gunsamerica.com\/digest\/?p=225942"},"modified":"2026-01-11T12:14:10","modified_gmt":"2026-01-11T18:14:10","slug":"demon-core-criticality-accident-history","status":"publish","type":"post","link":"https:\/\/gunsamerica.com\/digest\/demon-core-criticality-accident-history\/","title":{"rendered":"Demon Core: The Day Curiosity Killed"},"content":{"rendered":"\n

<\/path><\/svg><\/span><\/span>Estimated reading time: <\/span>13<\/span> minutes<\/span><\/p>\n\n\n\n

From Hiroshima\u2019s first operational strike to the Demon Core\u2019s deadly lessons, this is how nukes, missteps, and raw physics still terrify a very modern world.<\/p>\n\n\n\n

Why Nukes Still Keep Putin Relevant<\/h2>\n\n\n\n

Humanity has a weird love-hate relationship with nuclear weapons. They are at once everywhere and nowhere. The spectre of nuclear war shapes geopolitics unlike anything else. However, nobody really knows what that would look like.<\/p>\n\n\n\n

\"1950s
We still don’t really know how a serious nuclear exchange might play out, because we are all too rightfully terrified to try it. Public domain.<\/figcaption><\/figure>\n\n\n\n

The Trump Card<\/p>\n\n\n\n

Nukes are the only reason anybody on Planet Earth still takes Vladimir Putin seriously. Russia has a population of around 146 million. Russia’s gross domestic product falls just behind that of Italy and just ahead of that of Canada. Germany\u2019s economy is twice as vibrant as that of the Russian Federation. Ours is ten times larger. Were it not for the 4,309 operational nuclear warheads that Putin maintains, Russia would be rightfully viewed as a Third World backwater goat-spit of a nation. Absent those nukes, the world would have long ago banded together and spanked the Russians right out of Ukraine. However, nuclear war scares absolutely everybody, and for good reason.<\/p>\n\n\n\n

\"Vladimir
Here we see Russian President Vladimir Putin (right) meeting with Barack Obama. Putin is an objectively horrible person. Public domain.<\/figcaption><\/figure>\n\n\n\n

Nuclear weapons have only been used twice in real combat, and that was back in 1945. Both of those bombs were essentially prototypes. North Korea conducted the world’s last live nuclear test in 2017. Imagine how much the world has changed since 1945. Back then, telephones were the size of shoeboxes and were tethered to the wall. Now they are smaller than a box of wooden matches, ride in your pocket, and will let you talk to people in Norway from a subway in Istanbul. Nuclear weapons evolved just as transformationally; it is simply that nobody tries them out anymore.<\/p>\n\n\n\n

Hiroshima: The First Operational Atomic Strike<\/h2>\n\n\n\n

On 6 November 1945, we dropped the world\u2019s first operational nuclear weapon on Hiroshima, Japan. The Hiroshima bomb was a gun-type design powered by uranium-235. In this case, a slug of uranium was fired along a short barrel to impact a target made from the same stuff.<\/p>\n\n\n\n

\"Little
This is a photograph of the world’s first operational atomic bomb as it was about to be loaded into the B-29 Enola Gay for the attack on Hiroshima. Public domain.<\/figcaption><\/figure>\n\n\n\n

This violent kinetic reaction created a critical mass that resulted in a nuclear detonation. The Hiroshima bomb had a nominal yield equivalent to around 15,000 tons of conventional TNT explosive. It killed 70,000 people at the time of detonation and claimed about the same number later from residual effects.<\/p>\n\n\n\n

Nagasaki: When Smoke Saved Kokura<\/h2>\n\n\n\n

Three days later, we deployed a second nuclear device over Nagasaki. Curiously, Nagasaki was not the primary target. The second atomic bomb strike was to be directed at Kokura, but thick smoke over the target spared that city. The aircraft commander, a 25-year-old Army Air Corps pilot named Charles Sweeney, made the call on the fly to switch targets to Nagasaki.<\/p>\n\n\n\n

\"B-29
Charles Sweeney is the guy in the dark jacket. He was only 25 years old when he commanded a mission to obliterate an entire Japanese city. That’s what it took to win the war. Public domain. <\/figcaption><\/figure>\n\n\n\n

This second bomb was an altogether different design that was markedly more complicated than the first. This weapon was powered by plutonium-239. Plutonium-239 does not occur in nature. This isotope is a byproduct of the reaction that occurs when uranium-238 captures a loose neutron inside a nuclear reactor. Plutonium-239 is more easily produced than uranium-235. However, it is tougher to get plutonium-239 to go off uniformly.<\/p>\n\n\n\n

The second bomb used an altogether different mechanism. A series of chemical explosive charges configured similarly to the individual components of a soccer ball were arrayed circumferentially around a plutonium core. When carefully detonated at exactly the same moment, this created an immense imploding pressure wave that drove the plutonium to critical mass and resulted in a nuclear detonation. This nuclear strike killed 74,000 people at the moment of detonation and claimed a further 70,000 souls by the end of the year.<\/p>\n\n\n\n

Manhattan Project Money, Pressure, and Mistakes<\/h2>\n\n\n\n

The Manhattan Project was the program that created these two weapons. It cost $2 billion in 1945. That would be about $30 billion today. The Manhattan Project was the second-most expensive military undertaking of World War<\/a> 2. Curiously, the most expensive was the production of the B-29 Superfortress bomber that delivered the weapons. The overall cost of the B-29 program was closer to $3 billion.<\/p>\n\n\n\n

\"B-29
The development of the B-29 Superfortress bomber was actually the single most expensive engineering enterprise of World War 2. Public domain.<\/figcaption><\/figure>\n\n\n\n

Nuclear research in 1944 and 1945 was moving at light speed. We desperately needed the A-bomb as a tool to end the war. We knew that every other major combatant nation on Planet Earth was rabid for this capability. Whoever first deployed nuclear weapons at scale would undoubtedly emerge victorious. That pressure to produce resulted in some tidy little tragedies.<\/p>\n\n\n\n

How Atomic Energy Gets So Big From So Little<\/h2>\n\n\n\n

Nuclear energy is just crazy weird if you think about it. The laws of conservation of mass and energy posit that matter and energy can neither be created nor destroyed; they just change forms. When you strike a match, the fuel in the match doesn\u2019t actually cease to exist. It just changes into hot gases, smoke, ash, and the like. Those laws no longer apply when it comes to nuclear reactions.<\/p>\n\n\n\n

\"Side-by-side
The Hiroshima bomb is on the left. The Nagasaki weapon is on the right. Public domain.<\/figcaption><\/figure>\n\n\n\n

When the first bomb detonated over Hiroshima, about 0.7 grams\u2019 worth of uranium\u2014roughly the same weight as a small paperclip\u2014was instantly transformed into pure energy. That uranium no longer existed within the physical universe. It had actually been turned into energy in accordance with Einstein\u2019s E=MC2. If my math is correct, that paperclip\u2019s worth of uranium released as much energy as two million conventional 155mm high-explosive artillery rounds all going off at one time. Wow…<\/p>\n\n\n\n

The Demon Core: A Softball-Sized Killer<\/h2>\n\n\n\n

The thing about radioactive material is that you really don\u2019t want to get any of it on you. The half-life for plutonium-239 is 24,110 years. That means it takes 24,110 years for half of a quantity of radioactive plutonium-239 to degrade into something less lethal. That stuff is unimaginably dangerous.<\/p>\n\n\n\n

\"Physicists
Harry Daghlian is second from the left. Louis Slotin is second from the right. Here, the two men are helping assemble a nuclear bomb. Both physicists died horribly after being accidentally exposed to vast quantities of radiation. Public domain.<\/figcaption><\/figure>\n\n\n\n

Back in 1945, we had little clue what we were doing. The eggheads who made it called this particular sphere of plutonium gallium alloy Rufus. Rufus was 8.9 cm in diameter. That\u2019s roughly 3.5 inches. For the sake of comparison, a regulation softball is 3.8 inches across.<\/p>\n\n\n\n

Plutonium is really dense. This softball-sized chunk weighed 14 pounds. As plutonium corrodes readily in the presence of oxygen, this sphere was coated with nickel to help retain its stability. Rufus eventually became known as the Demon Core.<\/p>\n\n\n\n

We built this monster to power the third atomic bomb that was obviously never dropped on Japan. When Japan capitulated, the core was retained at the Los Alamos Laboratory in New Mexico for research. One of the questions that needed to be answered was exactly how close this thing was to criticality just sitting on a table.<\/p>\n\n\n\n

Daghlian\u2019s Accident: A Brick, A Spark, A Fatal Dose<\/h2>\n\n\n\n

Plutonium naturally releases neutrons. Focusing these neutrons back into the material is what causes the mass to go supercritical and explode. How much of that neutron flux was required to get the party started was important to know. On 21 August 1945, a 24-year-old physicist named Haroutune \u201cHarry\u201d Krikor Daghlian was studying just that. To do so, he stacked tungsten carbide bricks circumferentially around the magic ball. Tungsten carbide is an effective neutron reflector. While he was occupied doing this, a 29-year-old military security guard named Robert Hemmerly sat at a desk some dozen feet away.<\/p>\n\n\n\n

\"Los
This was the situation that led to the death of Harry Daghlian. Daghlian inadvertently dropped one of the tungsten carbide blocks shown here and created a catastrophic radiation release. Los Alamos photograph.<\/figcaption><\/figure>\n\n\n\n

As Daghlian carefully stacked these heavy bricks around the core, he accidentally let one slip out of his hands. This thing bounced off the plutonium sphere, creating an impressive shower of sparks. He immediately moved the offending brick back to its intended spot. 25 days later, Harry Daghlian died of acute radiation syndrome. Private Hemmerly succumbed to acute myelogenous leukemia in 1978, 33 years after the accident. Hemmerly was 62 at the time.<\/p>\n\n\n\n

Tickling the Dragon\u2019s Tail: Slotin\u2019s Fatal Slip<\/h2>\n\n\n\n

On 21 May 1946, a physicist named Louis Slotin was tending to Rufus alongside seven assistants. They were, likewise, studying the effects of neutron reflectors on critical mass. Slotin was actually scheduled to leave Los Alamos. He was only present to demonstrate the technique to Alvin Graves, another physicist who was planning to use this core during Operation Crossroads, the nuclear tests at the Bikini Atoll.<\/p>\n\n\n\n

\"Beryllium
The beryllium spheres shown here acted as neutron reflectors to energize the plutonium fuel. Note the lack of gloves. Additionally, somebody was obviously drinking a Coke around this stuff. Public domain.<\/figcaption><\/figure>\n\n\n\n

In this case, the reflectors were a matching pair of machined beryllium spheres. The astute film nerd will recall the comic reference to beryllium spheres in the epic sci-fi farce Galaxy Quest. Galaxy Quest is one of my favorite movies. If you haven’t seen it, check it out. You’ll thank me later.<\/p>\n\n\n\n

\"Galaxy
Galaxy Quest is nature’s perfect movie. There is an oblique reference in the film to early nuclear research.<\/figcaption><\/figure>\n\n\n\n

Anyway, the protocol required that these spheres be arranged around the plutonium core using shims to maintain a slight separation so the mass did not become critical. However, Louis Slotin was a rebel. Arcane workplace safety rules didn’t apply to him.<\/p>\n\n\n\n

Slotin had done this many times with several different cores, often while dressed in blue jeans and cowboy boots. His technique was to wedge a flat-tip screwdriver in between the beryllium spheres and twist as needed to adjust the spacing. When the esteemed nuclear physicist Enrico Fermi heard about this, he predicted that Slotin would be dead within a year. A colleague named Richard Feynman referred to this unorthodox technique as \u201cTickling the dragon\u2019s tail.\u201d<\/p>\n\n\n\n

\"Recreation
One quick slip with a screwdriver was all it took to kill Louis Slotin. Public domain.<\/figcaption><\/figure>\n\n\n\n

As he lowered the top sphere, Slotin\u2019s screwdriver slipped. The two spheres were in contact for less than a second before Slotin flipped the top half onto the floor. Slotin was crouching over the apparatus at the time, so his body shielded most of the rest of his team from the explosive neutron burst.<\/p>\n\n\n\n

\"Diagram
The relative locations of the people around the core determined their radiation dose. Public domain.<\/figcaption><\/figure>\n\n\n\n

Slotin was 35 at the time. He died of acute radiation poisoning nine days later. Of the remaining six people present, Marion Cieslicki succumbed to acute myelocytic leukemia 19 years after the accident in 1965. Surprisingly, the rest all died of fairly reasonable causes.<\/p>\n\n\n\n

\"Mapping
Investigators created this map showing where everyone in the room was standing when the accident occurred. Public domain.<\/figcaption><\/figure>\n\n\n\n

What A Real Nuclear Exchange Might Mean Today<\/h2>\n\n\n\n

The Hiroshima bomb had a nominal output of 15,000 tons of TNT. The Russian Tsar Bomba, the largest nuclear weapon ever detonated, was 3,000 times more powerful. The W88 warhead that currently rides atop modern American nuclear missiles produces 475 kilotons of explosive force, roughly 32 times that of the Hiroshima bomb.<\/p>\n\n\n\n

\"Tsar
The Russian Tsar Bomba detonated in 1961 with the explosive force of 50 million tons of TNT. An air burst, the force of the detonation actually reflected off the earth and lifted the fireball farther up into the air. The resulting mushroom cloud rose to a height of 42 miles, and the blast wave circled the globe three times. Fair use.<\/figcaption><\/figure>\n\n\n\n

I read recently that somebody believed that the US would return to its current GDP roughly a decade after a global nuclear exchange. Other really smart folks think a serious nuclear war would end all life on Planet Earth. Personally, I\u2019d just as soon we not answer that question any time soon.<\/p>\n\n\n\n