The Demon Core

THE CURSE OF THE DEMON CORE

The real-life story of a small ball of plutonium, the people
it killed, and the researchers who blew it up.

THE BOMB
On the evening of Tuesday, August 21, 1945, American physicist Harry Daghlian was working at the U.S. government’s ultra-secret Los Alamos National Laboratory in New Mexico. He was performing a very delicate experiment: Daghlian was placing brick-shaped pieces of metal around a chunk of plutonium, the highly unstable fuel used in most nuclear bombs. And he was making it more unstable with every brick he placed around it. [...]

Daghlian was working with a gray, softball-sized sphere of Pu-239. It was basically the core, or pit, of a nuclear bomb—the part that does the exploding. He was performing experiments with the core to determine whether it was the proper size and density to sustain a chain reaction—so it could be used in an actual bomb.

CORE VALUES
Daghlian began surrounding the core with bricks of tungsten carbide, a very dense metal that reflects neutron radiation. The more enclosed in metal the core became, the more neutrons were reflected back into the core, rather than simply flying off. That meant that the rate of neutron bashing and atom splitting in the core increased as Daghlian added more and more bricks. (A geiger counter indicated whether the experiment was working, by clicking faster and faster.) [...]

Using the bricks, Daghlian built walls, about ten inches on a side and ten inches high, around the plutonium. He then took a brick and slowly positioned it—he was simply holding it in his hand—over the opening at the top of the structure, right over the core. The geiger counter clicked wildly. Enough neutrons were now being reflected back into the core that it was headed toward a supercritical state.

Daghlian went to jerk the brick away…and dropped it.

UH-OH
The brick landed right on top of the ball of plutonium. The plutonium was now effectively surrounded by neutron reflecting material, and it went supercritical immediately. There was a blue flash…

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• Past excerpts can be found by hitting “Excerpts” in the tags blow this post.