Demon Core: How The Third Nuclear Bomb Destined For Japan Killed a Bunch of American Scientists

President Harry S. Truman knew that one bomb would not be enough to force Japan to surrender, so he ordered two. What many don’t know is that there was a third bomb in reserve, just in case. This third bomb had not been assembled yet, but its plutonium core—the heart of the bomb—was ready, and kept at the Los Alamos National Laboratory. When it became clear a third bomb would not be necessary, nuclear scientists at Los Alamos were delirious with excitement. Here there was in their hands, the rarest of the rare material—a 6.2 kg core of pure plutonium. They probed and prod the shinny metallic sphere and subjected it to countless experiments, until two sloppy scientists nearly blew up the laboratory and ruined it for every one. Both of them were dead within days, and the core acquired the nickname “demon core”. A replica of the demon core in a mock setup used by one of the physicists during a fatal experiment.   Nuclear bombs are different from conventional bombs. There are no fuses or detonators. What we have instead is a mass of nearly critical radioactive materials. At the time of detonation, this mass is made supercritical by bringing more radioactive materials close together so that flying neutrons knock out more neutrons free from other atoms creating a self-sustaining chain reaction. At that time, there was no easy method to determine how much uranium or plutonium would be required to achieve critical mass. So scientists figured it out the hard way. At the head of the Critical Assemblies group was Otto Robert Frisch, an Austrian physicist. Frisch’s method was simple and dangerous. Frisch cut up the fissile materials into small bars 3 centimeters long, and stacked them up while keeping an eye on his radiation meter until criticality was achieved. To help slow down the reaction, he used uranium hydride instead of pure uranium.