Harry K. Daghlian, Jr.

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The sphere of plutonium surrounded by neutron-reflecting tungsten carbide blocks in a re-enactment of Harry Daghlian's 1945 experiment.^[1]

Harry Daghlian's radiation burned hand^[1]

Harry K. Daghlian, Jr., (1921 – September 15, 1945) was a physicist with the Manhattan Project who died from performing an accidental critical mass experiment at the remote Omega Site facility at Los Alamos National Laboratory in New Mexico, on August 21, 1945.

Daghlian was irradiated as a result of a criticality accident which occurred when he accidentally dropped a small tungsten carbide brick onto a 6.2 kg delta phase plutonium bomb core.^[1] This core, available at the close of World War II and later nicknamed the "Demon core", later resulted in the death of Louis Slotin in a similar accident, and was used in the ABLE detonation, during the Crossroads series of nuclear weapon testing. ^[2]

In the experiment, the tungsten bricks were being slowly added around the core, being used as neutron reflectors, which serve to reduce the mass required for plutonium to be critical. Eventually, enough bricks would have been added to allow the assembly to go into a controlled critical nuclear reaction, as a miniature nuclear reactor. This last step was not to have been done by a scientist working alone, however, and Daghlian was violating "official" safety regulations by working on it late at night in the lab. Since the assembly was nearly in the critical state, the accidental addition of the last brick caused the reaction to go immediately into the prompt critical region of supercritical behavior.

The radiation event which accompanied prompt criticality was accompanied by a blue glow of ionization. Daghlian panicked immediately after dropping the brick and attempted to knock off the brick without success. He was forced to partially disassemble the tungsten-carbide pile to halt the reaction.^[2]

Daghlian died twenty-one days later, from acute radiation sickness.^[2]

This incident was fictionalized in the 1995 book Los Alamos by Joseph Kanon.

On May 20, 2000, Daghlian was memorialized by the city of New London, Connecticut.

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[edit] Notes

^ ^a ^b ^c LA-13638 A Review of Criticality Accidents Los Alamos report, 2000 revision — PDF, pages 74-75, 'His dose was estimated as 510 rem from a yield of 10^16 fissions.', 'The nickel canning on the plutonium core did not rupture.'
^ ^a ^b ^c Miller, Richard L. (1991). Under the Cloud: The Decades of Nuclear Testing. The Woodlands, Texas: Two Sixty Press, 68, 69, 77. ISBN 0029216206.