Criticality accident
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A criticality accident is an accidental uncontrolled nuclear fission chain reaction. It is sometimes referred to as a critical excursion, critical power excursion, divergent chain reaction, or simply
The sphere of plutonium surrounded by neutron-reflecting tungsten carbide blocks in a re-enactment of Harry Daghlian's 1945 experiment
A re-creation of the Slotin incident. The plutonium "demon core" (the same as in the Daghlian incident) was inside at the time of the accident, and would not be visible.
Lady Godiva assembly in the scrammed (safe) configuration
Lady Godiva assembly, with damaged supporting rods after the excursion of February 1954. Note the images are of different assemblies.
Demon core
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The demon core was a sphere of plutonium–gallium alloy that was involved in two fatal radiation accidents when scientists tested it as a fissile core of an early atomic bomb. It was manufactured in 19
Criticality accident
…and died 25 days later after accidentally dropping a tungsten carbide brick onto a sphere of plutonium, which was later (see next entry) nicknamed the demon core. The brick acted as a neutron reflector, bringing the mass to criticality. This was the first known criticality accident causing a fatality. 0 1 21 May…
The two physicists Harry Daghlian (center left) and Louis Slotin (center right) during the Trinity Test. Both died following supercritical accidents involving the "demon core".
A drawing based on the above sketch