Demon Core: A 6.2 kg Sphere and Two Bench Accidents

The demon core was a 6.2 kg plutonium sphere at Los Alamos that went critical twice on a lab bench, in August 1945 and May 1946, without exploding. We follow the neutrons to see what criticality means, how a reflector pushed the sphere past the line, and why each event was a burst rather than a blast. The episode ends with the remote experiments that followed and what became of the core. The payoff: the sphere was never a bomb. On its own it was subcritical, and it needed a reflector to get close to the line. In 1945 that reflector was tungsten carbide bricks, and in 1946 it was beryllium shells held apart by a screwdriver. In both accidents a hand-held margin gave out. Reflection explains how each burst began, and the metal's own heating explains why neither became a blast. What stopped the 1946 reaction is something the physicist who wrote about it, on 3 June 1946, said he was not quite sure of. The change that followed targeted the hands, not the sphere: experiments went on, with personnel a quarter-mile away. SOURCES Los Alamos report LA-13638, A Review of Criticality Accidents — https://trinity.ans.org/file/1475/la-13638... Los Alamos Historical Society, The Slotin Accident: Inside the Archives — https://losalamoshistory.org/the-slotin-ac... Atomic Heritage Foundation, Harry Daghlian — https://ahf.nuclearmuseum.org/ahf/profile/... Atomic Heritage Foundation, Louis Slotin — https://ahf.nuclearmuseum.org/ahf/profile/... #DemonCore #Criticality #LosAlamos #ManhattanProject #NuclearPhysics Which question about this subject do you want answered next? Tell us in the comments. Chapters: 0:00 What was the demon core? 0:28 Why was the sphere still in a lab? 1:34 What does 'critical' mean? 2:54 How does a reflector push it critical? 4:02 What was Daghlian measuring in 1945? 4:56 What went wrong with the last brick? 5:55 Why did it not explode like a bomb? 7:04 Why was the same core still in use? 7:52 What was Slotin demonstrating in 1946? 8:52 What happened when the screwdriver slipped? 9:36 What did Los Alamos record? 10:03 What stopped the 1946 reaction? 10:48 How did experiments change afterwards? 11:48 What happened to the core itself? 12:33 Was it the design or the procedure? Narrated by an AI voice. Pictures are AI-generated illustrations unless credited above.