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Early atomic bomb research – the ‘demon core’ that killed physicist Harry Daghlian 

The Demon Core: How One Man Intervened With His Bare Hands During A Nuclear Accident   https://www.iflscience.com/physics/the-demon-core-accident-how-one-man-stopped-a-nuclear-detonation-with-his-bare-hands/ 17 May 21,

Following the end of World War 2 and the devastating impacts of the Hiroshima and Nagasaki nuclear bombings, the Cold War was looming. The immense destruction and power promised by atomic bombs pushed world superpowers into a nuclear research frenzy, with the USA preparing to drop a third on Japan , and the remaining nations creating their own arsenal as a deterrent or defense.  

Enter the ‘demon core’. Sitting at a sizeable 6.2 kilograms (13.7 pounds) and 3.5 inches in diameter, this spherical mass of radioactive plutonium (at the time named ‘Rhufus’) was designed in nuclear research to be a fissile core for early iterations of the atomic bomb. Throughout 1945 and 1946, the demon core was experimented on ……

As expected from its’ ominous title, the demon core was not kind to the nuclear physicists involved. Designed as a bomb core, it had just a tiny margin before it would increase radioactivity and become supercritical (once the fission reaction has begun, it increases in rate). Therefore, any external factors that could increase reactivity, for example, compression of the core (which is how the fission bomb detonates), must be carefully monitored around the demon core.

Despite the danger, researchers used the core as an experimental piece on supercriticality, using neutron reflectors to push it to its’ limits. Neutron reflectors are used to surround the core, and as the nuclear fission reaction occurs, they reflect neutrons back at the nuclear material to increase the amount of fission taking place.

In 1945, alone in his laboratory, physicist Harry Daghlian was performing a neutron reflector experiment on the demon core when he mistakenly dropped a brick of reflective tungsten carbide onto the core, pushing it into supercriticality and releasing a deadly burst of neutron radiation. After a 3-week battle with acute radiation sickness, Daghlian succumbed to his wounds, leading to tighter legislation around nuclear research in the Manhattan Project – although it would not be strict enough.

Despite the danger, researchers used the core as an experimental piece on supercriticality, using neutron reflectors to push it to its’ limits. Neutron reflectors are used to surround the core, and as the nuclear fission reaction occurs, they reflect neutrons back at the nuclear material to increase the amount of fission taking place.

In 1945, alone in his laboratory, physicist Harry Daghlian was performing a neutron reflector experiment on the demon core when he mistakenly dropped a brick of reflective tungsten carbide onto the core, pushing it into supercriticality and releasing a deadly burst of neutron radiation. After a 3-week battle with acute radiation sickness, Daghlian succumbed to his wounds, leading to tighter legislation around nuclear research in the Manhattan Project – although it would not be strict enough.

That burst of radiation would kill Slotin within 9 days of exposure. Stood right beside him during the accident, Alvin Graves would also receive a huge dose of radiation but would survive the ordeal and live for another 20 years before death. Owing to Slotin’s quick thinking and body position, which absorbed most of the radiation, the remaining onlookers were shielded from the blast and survived to tell the tale.  

Following the accidents, the core would finally gain its name as the demon core, before being recycled down into other fissile cores. 

May 18, 2021 - Posted by | history, incidents, Reference, weapons and war

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