The Tale of Demon Core Apparatus: Accident Brought Blisters and Blood to Attending Scientists

On August 13, 1945, there was a nuclear bomb known as the "demon core" that was ready to be used against Japan. A week earlier, two other nuclear bombs, "Little Boy" and "Fat Man," had already been used in Hiroshima and Nagasaki, respectively, and caused significant destruction and loss of life. However, Japan surrendered on August 15 after the attack on Nagasaki, with Emperor Hirohito acknowledging the demands of the Allies. These were the only nuclear bombs ever used in warfare and resulted in the deaths of approximately 200,000 people. If circumstances had been different, there may have been a third nuclear strike.

The surrender of Japan on August 15, 1945, also had significant implications for the scientists at the Los Alamos Laboratory in New Mexico who were working on a third nuclear bomb, which had a 6.2-kilogram plutonium and gallium core known as "Rufus." If the war had continued, this core would have been used in a second "Fat Man" bomb and detonated over another Japanese city just four days later. However, with the end of the conflict, the core was retained at the laboratory for further testing. It was during these tests that the device earned the nickname "demon core." This was the first time that the Japanese public had heard the voice of one of their emperors.

'Demon Core' Apparatus

The nuclear experiment, which was planned for launch but ultimately didn't happen, resulted in a core called the "demon core" being left at Los Alamos. The scientists at Los Alamos were aware of the dangers of working with the core, as they were conducting experiments to determine the point at which the plutonium would reach a critical mass and cause a nuclear chain reaction, releasing harmful radiation.

On the night of August 21, 1945, Los Alamos physicist Harry Daghlian was working alone in the lab (contrary to safety protocols) with only a security guard present. He was attempting to conduct a "tickling the dragon's tail" experiment, in which he placed bricks made of tungsten carbide around a plutonium sphere to bring it closer to criticality. As he continued to add bricks, the neutron-monitoring equipment indicated that the plutonium was almost at the point of becoming supercritical. As he reached to remove one of the bricks, he accidentally dropped it onto the top of the sphere, causing it to reach super criticality and emit a blue light and a burst of heat.

Despite removing the brick, Daghlian had already received a fatal dose of radiation. His hand was severely burned and he fell into a coma after experiencing weeks of sickness and pain. He passed away just 25 days after the accident. The security guard present also received a non-lethal dose of radiation. Despite an investigation and review of safety procedures following Daghlian's death, another similar accident occurred the following year.

(Photo : (Los Alamos National Laboratory))
Recreation of 1945 accident.

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Scientists: Victims of Extreme Radiation

On May 21, 1946, physicist Louis Slotin was conducting a criticality experiment similar to the one that resulted in Daghlian's death. He was using a beryllium dome, called a tamper, to reflect neutrons at the core and bring it closer to criticality. He carefully maintained a small gap between the tamper and the core using a screwdriver to allow enough neutrons to escape. However, the screwdriver slipped and the tamper fell completely over the core, causing it to reach super criticality and emit a blue flash and heat. Another scientist in the room, Raemer Schreiber, witnessed the incident.

Schreiber reported that the blue flash was visible in the room and lasted for a few tenths of a second. Slotin quickly removed the tamper, but the damage had already been done. Slotin, as well as seven others in the room including a photographer and security guard, were exposed to radiation, with Slotin receiving a lethal dose that was higher than the one that Daghlian had received. Initially, Slotin seemed to recover in the hospital, but he soon began to lose weight, experience abdominal pain, and show signs of mental confusion.

Los Alamos released a press statement at the time describing Slotin's condition as "three-dimensional sunburn." He passed away nine days after the accident. The two deadly accidents prompted significant changes at Los Alamos, including the implementation of new protocols that prohibited "hands-on" criticality experiments and required scientists to use remote-controlled machinery to manipulate radioactive cores from a distance of hundreds of meters. The plutonium core was also given the nickname "demon core" rather than its previous name, "Rufus."

'Demon' That Caused Devastation and Death

After the Slotin accident, the demon core's radiation levels increased, leading to the cancellation of plans to use it in Operation Crossroads, the first post-war nuclear explosion demonstrations that were scheduled to take place at the Bikini Atoll a month later. Instead, the plutonium was melted down and added back to the US nuclear stockpile to be used in the creation of other cores as needed. This marked the second and final time that the demon core was not used in a detonation.

While the deaths of the two scientists cannot be compared to the potential devastation that could have occurred if the demon core had been used in a nuclear attack against Japan, it is clear why the scientists gave it the superstitious nickname they did. The story of the demon core also includes other strange details. It is interesting to note that both Daghlian and Slotin died from similar accidents involving the demon core on Tuesdays, on the 21st day of the month, and in the same hospital room.

These are simply coincidences, however. The demon core itself was not demonic. The real horror is the reckless and dangerous manner in which mid-20th century scientists pursued the creation of these weapons, fully aware of the risks involved. Based on Schreiber's narrative, Slotin's first words after the accident involving the screwdriver were resigned, as he had comforted his dying friend Daghlian in the hospital and knew what was to come.