Demon Core: The experiment that took the lives of two physicists

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Known Dubbed the “Demon Core”, this block of gray metal was responsible for two tragic accidents that claimed the lives of physicists. was talented and emphasized the dangers of using nuclear materials. So what was so special and dangerous about this object?

In the early 1940s, the world was in the midst of a scientific revolution that would change history forever. During World War II, the famous Manhattan Project brought together scientists from around the world to develop the atomic bomb, a weapon that harnessed nuclear fission to release enormous amounts of energy. Elements such as uranium-235 and plutonium-239 formed the basis of these devices.

This last element, the hero of this story, is a highly radioactive isotope that can undergo chain nuclear fission, releasing energy by splitting its atoms into smaller pieces. The so-called critical state occurs when the material is compressed or structured in a way that allows the neutrons emitted by fission to cause uncontrolled chain reactions.

“This principle is the same principle that powers atomic bombs, but in a laboratory, even small amounts of nuclear material can be lethal when reactions are left uncontrolled.”

Demon Core was created as part of the war effort to be used in a third atomic bomb after Hiroshima and Nagasaki. However, with the end of World War II, better understanding the limits of the physicality of nuclear materials became a subject of study.

Weighing around 6.2 kilograms, the core was dense and seemingly harmless, but its closeness to criticality meant it could trigger dangerous chain reactions under certain conditions.

Physicists who worked with him They attempted to determine how close they could get to the critical state without going beyond it, by conducting experiments known as “playing with the dragon’s tail.”

But this is not a happy story. On the night of August 21, 1945, physicist Harry Daghlian was alone in the core room of the Los Alamos National Laboratory in New Mexico. He was running an experiment to measure the critical mass of the nucleus by stacking blocks of tungsten carbide around plutonium to increase its reactivity by reflecting neutrons back to the nucleus.

At a crucial moment, Daghlian accidentally dropped one of the blocks directly onto the core. This triggered a sudden release of radiation, causing the material to reach a temporary critical state.

Daghlian reacted quickly and removed the block, but it was too late. He received a lethal dose of radiation equivalent to 5.0 Gy (5.0 gray, the unit of absorbed radiation. Lethality begins around 2.0 Gy).

Over the next few weeks, Daghlian experienced the classic symptoms of acute radiation exposure: nausea, burns, and organ failure. He died 25 days later, when he was only 24 years old.

Less than a year later, on May 21, 1946, physicist Louis Slotin also fell victim to the Demon Core. Slotin, an expert in nuclear bomb assembly, was demonstrating a criticality experiment to other colleagues. Using an extremely risky technique, he manipulated the beryllium hemispheres around the nucleus, which act as neutron reflectors.

To check the proximity of the reflectors, Slotin simply used a screwdriver and separated them with a small opening. During the experiment, the key slipped, closing the gap and sending the core into a supercritical state. In a fraction of a second, an intense burst of radiation was released.

Realizing his mistake, Slotin reacted quickly and separated the hemispheres, but he had already absorbed a lethal dose of radiation estimated at 10 Gy. He felt instantaneous warmth, a classic sign of excessive radiation exposure. Over the next few days, he developed the same symptoms as Daghlian, including nausea, vomiting, and severe burning. Slotin died nine days later at the age of 35.

In both cases, the emitted radiation caused massive ionization in the scientists’ bodies, destroying the molecules. The DNA is broken and the cells are irreversibly killed, making recovery impossible.

After the second accident, the core was deactivated and eventually used in a nuclear test in Operation Crossroads in 1946. Significant changes to safety protocols for nuclear testingIncluding a ban on manual handling of radioactive materials in critical conditions.

The Demon Core left a dark legacy, but it also served as a warning about the dangers of nuclear energy if not used with due respect and care. The unfortunate accidents at Daghlian and Slotin helped shape safer practices in handling radioactive materials that continue to evolve today.