The Demon Core: A Tale of Atomic Ambition and Tragic Fate

The demon core was a plutonium core, originally intended to be the heart of the third atomic bomb developed by the United States during World War II. As the war neared its climax, the United States dropped two nuclear bombs on Japan — one on Hiroshima and another on Nagasaki — in a bid to bring about a swift end to the conflict.

In the shadow of these monumental events, preparations were underway for a potential third strike. The plutonium core, later to be infamously known as the "demon core," was meant to power this third nuclear weapon.

The intention behind its creation was clear: If Japan didn't surrender following the devastation at Hiroshima and Nagasaki, the U.S. was prepared to drop a third atomic bomb to enforce submission.

However, history took a different turn. Japan's surrender in the wake of the two atomic bombings called off the assembly and deployment of what would have been a third catastrophic event. Consequently, the demon core was never used as intended and remained at Los Alamos National Laboratory, where it transitioned from a weapon of war to a subject of scientific inquiry.

Despite its dormant state, the core retained a dangerous potential due to its critical mass — a precise amount of plutonium capable of sustaining a chain reaction of nuclear fission.

This lingering capacity for unprecedented energy release earmarked the demon core as an object of both fascination and horror, setting the stage for a series of events that underscored the dangerous balance between scientific ambition and the sanctity of human life.

Harry Daghlian was an American physicist at the forefront of the United States' atomic research on the Manhattan Project. He became an unwitting testament to the danger of handling radioactive material.

In the summer of 1945, within the confines of the Los Alamos laboratory, Daghlian was engaged in a critical experiment designed to probe the boundaries of nuclear fission. His task involved constructing a neutron reflector around the demon core to measure its approach to criticality (the point at which a nuclear chain reaction becomes self-sustaining).

Daghlian's methodical approach had him carefully assembling layers of tungsten carbide bricks around the plutonium core. He had built five layers of bricks and was about to place the last brick in the center when his monitoring device signaled that the core could go supercritical.

The assembly was precariously close to reaching critical mass.

Reacting to the warning, Daghlian attempted to withdraw the brick, aiming to halt the experiment and prevent the core from going critical. However, his hand slipped and he accidentally dropped the brick onto the core. The mishap triggered a prompt critical reaction, evidenced by a blue flash of light and a blast of heat.

At that moment, the plutonium bathed Daghlian in a lethal dose of radiation, marking the beginning of an agonizing battle with radiation sickness; despite the best efforts of medical professionals, Daghlian's condition deteriorated rapidly and he ultimately died of radiation sickness 25 days later.

His tragic death highlighted the profound dangers inherent in the atomic age, serving as a grim reminder of the potency of the radioactive materials humanity had unleashed.

The term "critical" signifies a state in which a nuclear chain reaction becomes self-sustaining. This criticality is achieved when the mass of fissile material, such as plutonium or uranium, reaches a point where each nuclear fission event releases a sufficient number of neutrons to sustain an ongoing series of reactions.

Achieving critical mass does not inherently mean a nuclear explosion is imminent; rather, it indicates that the material has reached a delicate balance of neutron production and absorption. In controlled conditions, such as a nuclear reactor, maintaining a state of criticality allows for a steady release of energy, useful for generating electricity.

Conversely, in the context of atomic weapons, surpassing criticality — moving into what is known as "supercritical" — is deliberately sought to initiate a rapid, uncontrolled chain reaction, resulting in a devastating nuclear explosion.

Despite the tragic loss of Harry Daghlian, scientists at Los Alamos continued experiments on the core. Louis Slotin, a Canadian physicist known for his dexterity and confidence in handling radioactive materials, became the next to challenge the boundaries of nuclear physics.

Slotin was known for demonstrating a criticality experiment that involved bringing a plutonium core to the brink of going critical — essentially trying to get even closer to the edge of initiating an uncontrolled nuclear chain reaction.

The experiment used two beryllium-coated metal half-spheres, which could be brought close to the demon core to reflect neutrons back into it, inching it toward criticality.

The critical moment in the procedure came when Slotin, using only a screwdriver, wedged between the two spheres to create just enough space to prevent them from fully closing around the plutonium core: a risky process known as "tickling the tail of the sleeping dragon."

On May 21, 1946, Slotin was demonstrating this precarious experiment to Alvin Graves, his intended replacement, among other scientists in the room. As Slotin attempted the experiment, a slip of his hand caused the metal spheres to snap shut, instantly sending the core to its critical point.

The room was engulfed in another blue flash of light and a blast of heat, signifying a burst of neutron radiation.

Though Slotin quickly reacted to remove the sphere and halt the reaction, the damage was done. The others in the room survived with varying degrees of radiation exposure, but Slotin was not so fortunate. He suffered a massive dose of radiation poisoning and died 9 days later, becoming the second victim of the demon core.

The demon core, a product of the Manhattan Project's intense and groundbreaking efforts to harness atomic energy, claimed the lives of two physicists. The unfortunate victims, Harry Daghlian and Louis Slotin, suffered fatal accidents that led to their deaths due to acute radiation syndrome, also known as radiation sickness.

The deaths of Daghlian and Slotin served as a stark reminder of the inherent risks associated with the handling of radioactive materials and propelled forward the development of more rigorous safety measures.

In response to these incidents, enhanced safety protocols, including remote handling techniques and the implementation of stringent criticality safety guidelines, were adopted to prevent similar fatalities.

Thus, while the demon core directly resulted in two deaths, its legacy prompted significant advancements in the field of nuclear safety, ultimately safeguarding countless lives in subsequent years of atomic research and energy production.

The fate of the demon core, after its brief yet impactful history, was to be melted down and recycled into new cores for testing.

Following the second accident and the death of Louis Slotin, the laboratory instituted a change in how it approached nuclear safety. Recognizing the dire consequences of hands-on criticality experiments, Los Alamos never allowed its scientists to engage in such perilous direct contact again.

In the wake of these reforms, criticality experiments at Los Alamos were conducted remotely, with about a quarter mile separating scientists from radioactive material to ensure their safety.

This shift not only reflected a newfound respect for the power and danger of nuclear materials but also set a precedent for nuclear research worldwide. Since the U.S. hasn't dropped any more nuclear weapons following the bombings of Hiroshima and Nagasaki, the new cores created from the demon core remain unused.

We created this article in conjunction with AI technology, then made sure it was fact-checked and edited by a HowStuffWorks editor.