The Demon Core

The original atomic bombs were fission bombs. Fission bombs start a fission reaction. The other, newer atomic bombs--hydrogen bombs, are fusion bombs. They use the same fission reaction to start a fusion reaction. A fission bomb's reaction is, basically, the energy released when large and unstable atoms are unzipped. A fusion bomb's reaction is, basically, the energy released when two hydrogen atoms are fused into a helium atom.

I was always surprised that a fusion reaction releases far more energy that a fission reaction.

In any case, the original bombs needed a plutonium sphere--a ball or core--about the size of one of those mini-basketballs they sell at amusement parks. It would be placed in a bowl of neutron reflective material made of tungsten-carbide. To start the reaction, the top half of the bowl would have to be slammed onto the bottom half, preferably by an explosive device. The strength with which the top-half of the shell coming down around the core determined how far along the reaction would go. Placing it slowly would generate a shot of neutron radiation, but not a bomb-like explosion.

The plutonium core, while dangerous when in contact with or surrounded by tungsten-carbide neutron reflective objects, is itself stable and safe to handle with bare hands, if warm to the touch. In the beginning of the atomic age, scientists would have to test the criticality of a particular core; test it's explosive-ness and reactivity.

During one such early test, a physicist named Harry Daghlian, while building a tungsten-carbide base around a particular core, dropped one of the bricks directly onto the sphere. It went critical for only a moment and blasted him with radiation. He died twenty-five days later. Here's a photograph of a recreation of the accident with the exact same core:



The very next year, a friend of Daghlian and another physicist and self-proclaimed "bomb putter-together-er", a man given to bravado and showing off, had led a group of scientists into a room to show off how easy it was to test the criticality of a plutonium core. His name was Louis Slotin. He was from Winnipeg, his parents having escaped the encroaching antisemitism in Europe.

Using a line from Dick Feynman, they were going to "tickle the dragon's tail," a reference to the potential dangers. Slotin was about to be relieved of the hand-testing procedures, and was attempting to train a new physicist for the job. He typically went against protocol and used only a flat-head screwdriver to keep the two outer shells separated around the core. While even more dangerous, this would bring the core to near-criticality and give better test results.

Do you see where this is going? Slotin's hand slipped and the shells came together. The core went critical and blasted everyone in the room with neutron radiation. Slotin, having actually been holding the core, was dead in nine days.

Many of the seven others in the room that day died years later with what appeared to be obvious radiation related ailments.

In a strange turn of events the core for both Daghlian and Slotin was the same, and came to be known as the Demon Core.

Here's a picture of the recreation of the Slotin event, taken a few days after, using the same exact core. It's the same damn core!



Ironically, having been brought to criticality twice, the Demon Core was even more efficient and powerful. Here is the actual explosion of the bomb made with the Demon Core:



Is this totally wild or is just me?

It was after the Slotin incident that the US government stopped doing human tests of plutonium core criticality. Takes an incident, I guess, to get the right changes in a reactionary world.