The Demon Core: Deadly Nuclear Sphere

In the shadowy history of the nuclear arms race, codenames were key. Thus, the US research program that developed the atomic bomb was called the Manhattan Project. The first ever detonated nuclear device was nicknamed Gadget. And the bombs dropped on the Japanese cities of Hiroshima and Nagasaki were Little Boy and Fat Man respectively. And then, there was the Demon Core. Also known as the cursed core and the plutonium death core, this was a radioactive metal sphere no bigger than a softball and weighing roughly the same as a bowling ball.

It was intended to form the heart of another nuclear device for a third hit on Japan. Instead, it became notorious for its role in two fatal Manhattan Project accidents, claiming the lives of two scientists. So, what was this ‘cursed core’? How did it earn its eerie moniker? And what happened to the Demon Core? Read on to find out.

On 6th August 1945, the US dropped an atomic bomb with a uranium core, known as Little Boy, on the Japanese city of Hiroshima. On 9th August, it dropped one with a plutonium core, known as a Fat Man, on Nagasaki. Both had catastrophic consequences. During the same period, the scientists of the Manhattan project cast another sphere of plutonium with a diameter of 3.5 inches and weighing 13.7 pounds. They named it Rufus. It was intended to become the heart of a third bomb, another Fat Man. It was expected to be ready on 16th August. However, Japan’s surrender on 15th August 1945 rendered it unnecessary.

Instead of being deployed in warfare, Rufus became an object of study at the Los Alamos Laboratory in New Mexico. Scientists sought to understand the properties of plutonium and the mechanics of nuclear fission, using the core in a series of criticality experiments. These experiments aimed to determine the conditions under which the plutonium would reach critical mass, the point at which a nuclear chain reaction becomes self-sustaining. Rufus ended up causing the deaths of two scientists, earning it a new nickname: The Demon Core.

The first victim of the Demon Core was 24-year-old physicist Harry Daghlian. On 21st August 1945, he was conducting an experiment that involved stacking heavy bricks around the core, then still known as Rufus. As he added another brick, he noticed the setup was getting too close to a state where it could release harmful radiation, known as criticality. When he tried to remove the brick, he accidentally dropped it onto the core, causing it to release a burst of radiation. Although he quickly stopped the experiment, Daghlian had already received a dose of about 510 rem. For context, a dose over 500 rem is typically fatal. Despite medical treatment, he died of radiation sickness 25 days later, on 15th September 1945.

While it’s unclear exactly when the “Demon Core” moniker was coined or by whom, it’s generally accepted that it only earned this name after 21st May 1946, the date it was involved in a second fatal accident. On this occasion, Canadian physicist Louis Slotin was demonstrating a criticality experiment to several colleagues. Colloquially known as “tickling the dragon’s tail,” it involved bringing two beryllium hemispheres close together around the core without touching it. Slotin used a screwdriver to hold the hemispheres apart. But the screwdriver slipped and the hemispheres closed, causing the core to become supercritical. A flash of blue light filled the room as a massive burst of neutron radiation was released. Slotin immediately separated the hemispheres, stopping the reaction.

Despite his quick response, Slotin received a dose of 2,100 rem over his body, but 15,000 rem on the hand closest to the experiment. He died nine days later, aged 35. Several other personnel in the room were also exposed but survived with varying degrees of radiation sickness. This second tragedy cemented the core’s ominous reputation as the Demon Core.

The two fatal Manhattan Project accidents prompted a thorough review of safety protocols at nuclear research facilities. Hands-on criticality experiments were discontinued in favour of remote-controlled methods, significantly reducing the risk to personnel.

The stories of Daghlian and Slotin became cautionary tales within the scientific community. Their sacrifices underscored the lethal potential of nuclear materials and the necessity for rigorous safety measures. The accidents also contributed to a broader public awareness of the dangers associated with nuclear energy, influencing policies and perceptions for decades to come.

As for the Demon Core itself, it was supposed to be used in further tests. However, following the second of the Manhattan Project accidents, it was melted down instead.

The Demon Core incidents highlighted several critical lessons in nuclear safety. Both accidents occurred during manual experiments that were lacking in the kind of safety standards we’re familiar with today. The reliance on this kind of manual control was a massive risk, as one minor slip could – and did – prove fatal. Implementing strict protocols and using remote handling tools became essential practices following these events.

The deaths of Daghlian and Slotin also raised ethical questions about the responsibilities of scientists working with these kinds of dangerous technologies. Balancing the pursuit of knowledge with the duty to protect the people working on such experiments – and the wider public – remains a fundamental challenge in scientific research.

The tale of the Demon Core is a haunting chapter in the history of nuclear science. The legacies of Harry Daghlian and Louis Slotin continued to influence the scientific community decades after the accidents that proved so treacherous. These sobering events ultimately saw a far more stringent focus on safety practices and risk considerations in such dangerous scientific endeavours.