# Demon Core: The Sphere That Turned Deadly

Page: https://stenobird.com/podcast/understand-all-6956841/demon-core-the-sphere-that-turned-deadly
Text version: https://stenobird.com/podcast/understand-all-6956841/demon-core-the-sphere-that-turned-deadly.md
Podcast: [Understand All](https://stenobird.com/podcast/understand-all-6956841)
Published: 2026-06-16T09:40:02+00:00
Episode link: https://www.spreaker.com/episode/demon-core-the-sphere-that-turned-deadly--72444875
Audio file: https://dts.podtrac.com/redirect.mp3/api.spreaker.com/download/episode/72444875/demon_core_the_sphere_that_turned_deadly.mp3
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JSON: https://stenobird.com/v1/public/podcasts/understand-all-6956841/episodes/demon-core-the-sphere-that-turned-deadly
Duration seconds: 416

## Resource

A plutonium sphere at Los Alamos was never meant to become a legend — so how did the Demon Core end up tied to two fatal criticality accidents? In this episode, we unpack the Demon Core, Harry Daghlian, Louis Slotin, and the physics and safety failures behind the lab tragedies, so listen now and hear the real story before the myths take over. The Demon Core was a 6.2 kg plutonium-gallium sphere at Los Alamos that became infamous after two separate criticality accidents killed physicists Harry Daghlian and Louis Slotin. In this episode, we unpack the Demon Core, criticality accidents, neutron reflectors, and why a tiny change in geometry can turn a lab experiment deadly. • How the Demon Core went from wartime bomb core to radiation-safety cautionary tale • Why tungsten-carbide bricks and a beryllium reflector changed everything • What “criticality excursion” and “prompt criticality” actually mean • How the accidents shaped modern nuclear safety and remote handling rules 00:00 — A small lab slip with huge consequences 03:10 — What the Demon Core was 07:05 — The Harry Daghlian accident 11:20 — The Louis Slotin accident 16:00 — What changed in nuclear safety afterward Related resources: Internal: /episodes/demon-core | External: https://en.wikipedia.org/wiki/Demon_core | https://ahf.nuclearmuseum.org/ahf/history/atomic-accidents/ | https://en.wikipedia.org/wiki/Criticality_accident If this episode made you think differently about safety, science, or human error, share it with a friend and leave a review — it helps more people find the show.

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## Transcript

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