Horror fiction and folklore is filled with tales of cursed items, from the nasty wish-bringing “Monkey’s Paw" to the real and allegedly cursed Hope Diamond. Supernatural curses are of course not real, but science has shown us that items exist — or can be fabricated — that are so inherently dangerous that misfortune follows them, and the term “cursed” seems oddly appropriate.
The best example of this is what came to be known as the “demon core,” a 6.2 kilogram, 3.5 inch diameter subcritical sphere of plutonium that was used in fission experiments at Los Alamos laboratory in the mid-1940s. This sphere, which was originally intended to be the “third shot” at Japan after Hiroshima and Nagasaki, resulted in the deaths of two workers of Los Alamos in that era, and its legacy did not end there, as we will see.
Some words about the physics of the “demon core” is appropriate here. Plutonium is highly radioactive, and the nuclei of plutonium-239 atoms decay into atoms of uranium-235, ejecting a high-energy alpha particle in the process. That particle can stimulate other atoms to release their own high-energy products, and under the right conditions — “critical” conditions — this process starts a chain reaction, in which an “avalanche” of nuclear fission happens all at once, creating a burst of lethal radiation and potentially an explosion.
The chain reaction only happens when radioactive decay products spend enough time in the core to cause many secondary decays. One way this can happen is if the core is large enough, i.e. of a critical mass. Another way to do this is to surround a smaller core with materials that can reflect neutrons back at it, increasing the the rate of reaction and pushing it critical.
This latter strategy is extremely risky, especially if done by hand, and resulted in the two direct fatalities from the “demon core.” On August 21, 1945, the first of these happened when physicist Harry Daghlian accidentally dropped a neutron-reflecting brick on top of the core, resulting in a critical burst radiation. Though he knocked the brick away immediately, Daghlian received a fatal dose of radiation and died 25 days later.
(Replica of the Daghlian experiment, with core surrounded by neutron-reflecting bricks. Via Wikipedia.)
The second accident occurred on May 21, 1946, when physicist Louis Slotin and several other personnel were performing a slightly different criticality experiment, in which the core was surrounded by two hemispheres of neutron-reflecting material. By adjusting the separation of the hemispheres, the amount of radiation could be adjusted, with completely closure resulting in criticality. Slotin was recklessly keeping the hemispheres separated by the thinnest of margins — the head of a flat-head screwdriver — when the tool slipped and the sphere closed. A flash of blue light heralded the beginning of a chain reaction but, as Daghlian before him, Slotin stopped the reaction by quickly knocking the top hemisphere away. His actions likely saved the lives of his colleagues, but Slotin himself was not so lucky — he died nine days later from radiation poisoning.
(Replica of the Slotin experiment, via Wikipedia.)
With the second fatality, this plutonium core was now known as the “demon core.” Though Daghlian and Slotin were the only two direct fatalities due to the accidents, others on hand would later die of cancers likely brought on by these early exposures. Private Robert J. Hemmerly, who was present at Daghlian’s experiment, died in 1978 of acute myelogenous leukemia. Of those in the room with Slotin, one suffered immediately from acute radiation poisoning at the time (but lived), and several others died years later from illnesses likely radiation-related.
With Slotin’s death, manual testing of cores was ended, but the demon core’s deadly legacy was not quite finished. The core was used in the Crossroads Able nuclear detonation at Bikini Atoll on July 1, 1946. This test undoubtedly killed much local sealife, but also irradiated “Fifty-seven guinea pigs, 109 mice, 146 pigs, 176 goats, and 3,030 white rats” that had been placed on target ships. 35% of the animals died as a direct result of the blast or radiation exposure.
Not every animal succumbed to the “curse” of the demon core, however. One pig, named “Pig 311,” and one goat, “Goat 315,” survived the blast and were later transported to live out their days at the National Zoo. Apparently the curse had burned itself out in its final fiery explosion.
(Pig 311 and Goat 315, via Neatorama.)