“Demon Core”: how the third nuclear bomb intended for Japan killed two scientists

In 1945, the United States prepared nuclear bombs that were dropped on Hiroshima and Nagasaki. Initially, it was planned to hit many more cities, but Japan signed an act of surrender. Therefore, scientists began to use the charge from the third atomic bomb for experiments. Subsequently, it was called the “demon core”, or “demon charge”. The core was a ball of radioactive plutonium, which at that moment was called “Rufus”. Its weight is 6.2 kg and its diameter is 8.9 centimeters. However, during the experiments, two accidents occurred at once, which ended in the death of the scientists. This was the reason for the name of the kernel.

“Demon Core”: how the third nuclear bomb intended for Japan killed two scientists. The demon core that killed two nuclear physicists. Photo source: trauma.ru. Photo.

The demon core that killed two nuclear physicists. Photo source: trauma.ru

“Demon core” – what is it

The “demon charge”, like the charge that was used in the bombing of Nagasaki, consisted of three parts: it included two plutonium-gallium hemispheres and a ring that prevented ejection jet streams between hemispheres. In their experiments, scientists also used reflectors that surrounded the core and reflected neutrons back into the nuclear material, which increased the intensity of fission. Since plutonium easily corrodes, the sphere was coated with nickel.

The “demon core” had only a small margin of “safe fission” period before the radioactivity increased and became supercritical. This is because once the fission reaction begins, its rate increases rapidly. Therefore, any external influences, for example, compression of the core, could increase reactivity and lead to an uncontrolled chain reaction.

“Demon core” - what is it. The design of the «demon charge» consisted of three parts. Photo source: trauma.ru. Photo.

Accident related to the “demon core”

In 1945, nuclear physicist Harry Daghlian conducted an experiment with a neutron reflector on the demon core. At some point, he accidentally dropped a brick on the core, as a result it became critical and released a deadly stream of neutron radiation.

Doctors fought for the scientist’s life for three months, but he ultimately died from radiation sickness because he was too seriously damaged. But, despite the death of his colleague, the second scientist Louis Zlotin continued his work.

Accident related to the “demon core”. Harry Daghlian after a failed experiment on the left and Louis Zlotin on the right. Photo source: kulturologia.ru. Photo.

Harry Daghlian after a failed experiment on the left and Louis Zlotin on the right. Photo source: kulturologia.ru

“Tickling the dragon's tail” – a dangerous experiment

Zlotin wanted to find out how close the core is to supercriticality. To do this, he conducted an experiment that involved slowly lowering a neutron reflector over the core. Since the neutrons were reflected into the nucleus, the criticality increased. In parallel with this, measurements of activity inside the core took place.

During the experiments, it was important that the reflector did not touch the “demon core,” as this could lead to unpredictable consequences. Therefore, spacers were used between the reflector and the core. However, Louis Zlotin for some reason was not privy to the protocol. As a result, being a talented physicist, he developed his own method of increasing criticality, which required less time but was more dangerous. In particular, he refused to use gaskets.

Instead of spacers, Louis Zlotin used a flathead screwdriver to create the necessary space between the core and the reflector. Throughout the experiment, he manipulated the screwdriver with one hand. The experiment was successful, and the scientist repeated it several times. Because of the danger, this experiment was nicknamed “tickling the dragon's tail,” as the famous physicist Richard Feynman compared such actions in terms of danger and courage to provoking a dragon.

“Tickling the dragon's tail” is a dangerous experiment. A dangerous experiment by Louis Zlotin. Photo source: trauma.ru. Photo.

A dangerous experiment by Louis Zlotin. Photo source: trauma.ru

However, the scientist ultimately made a mistake – on May 21, 1946, when he demonstrated the experiment to several people in the Los Alamos scientific laboratory, the screwdriver only slipped. And although the reflector did not completely touch the core, it came very close to the core, as a result of which the core went into a supercritical state.

A flash of blue light erupted from the core, and then a strong fire broke out. Louis Slotin quickly removed the reflectors from the core, causing the reaction to stop. However, he himself managed to receive a strong dose of radiation, which killed him within nine days. The people present in the laboratory also received a large dose of radiation, but thanks to the position of the scientist’s body and his quick reaction, they managed to survive.

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Thus, the “devil's core” killed two people, after which experiments with it stopped. However, if Japan had not surrendered, many more people would have died from it, like bombs that left behind only shadows of people. However, nuclear tests continued, not only in the United States, but also in other countries. They also caused illness and even death of many people.