At Los Alamos there was a sphere of plutonium-239 that killed two men in nine months. Afterward, they called it the Demon Core.

The first accident: 21 August 1945. Physicist Harry K. Daghlian Jr. was working alone at night, stacking tungsten carbide bricks around the core to build a neutron reflector. Reflect enough neutrons back in and a subcritical mass goes critical.

He dropped a brick onto the core.

He got it off, but he’d already taken a lethal dose. He died of acute radiation syndrome 25 days later, on 15 September.

The second accident: 21 May 1946. Physicist Louis Slotin was demonstrating a procedure to determine the core’s critical mass — lowering a beryllium half-shell over the sphere and holding it fractionally open so it didn’t quite close.

The tool he used to hold the gap open was a screwdriver.

That experiment had a name. They called it tickling the dragon’s tail, and Enrico Fermi had reportedly warned Slotin he’d be dead within a year if he kept doing it that way.

The screwdriver slipped. The shell dropped. The core went prompt critical, there was a flash of blue light and a wave of heat, and Slotin threw the shell off with his bare hand — which almost certainly saved the seven other people in the room.

He died nine days later, on 30 May 1946.

What gets me about this is the tooling. The most dangerous object in North America, and the safety margin was a man’s grip on a screwdriver.

That is what the frontier of a new technology actually looks like: brilliant people, an unforgiving physics, and procedures that hadn’t been written yet because nobody had lived long enough to write them.

The Demon Core sits at the heart of my book Nightstalkers: The Rift — it’s the force behind the first rift opening in our timeline, right after the war, at Area 51.

This is one of the entries in The Elements Little Black Book: Facts, Trivia and Secrets of the Building Blocks of Everything.

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