Nuclear Fallout in the Marshall Islands: A Mistake
by I’m a baby boomer so the tales of nuclear devastation in Hiroshima and Nagasaki, were an unsettling casualty of war that was etched in the pages of my history textbooks. However, I don’t recall mention of the nuclear tests performed in Operation Castle. Specifically, the Castle Bravo test of 1954, which was intended to be a secret, or the resulting fallout from the accident that occurred there.
Testing in the Marshall Islands Resumes
The Operation Crossroads testing of 1946 at Bikini Atoll, had been deemed a success by the United States and nuclear testing ceased for the time being. However, in 1954, the Marshall Islands were once again the site of additional United States nuclear testing under the name Operation Castle. These tests were different from the previous tests conducted as they were designed to test the first solid fuel “dry” bomb.
Bravo Exceeds Predicted Yield
Also known as the H-bomb, the “dry” bomb was fueled by lithium deuteride. The Soviet Union had already used lithium deuteride in a nuclear bomb in their Sloika model, which was named after a layer cake. That’s because the design utilized a scheme in which fission and fusion fuel were layered. Bravo, however used the Teller-Ulam design which separated the fusion device from the fission device. As a result, Bravo became the most powerful nuclear device ever detonated by the United States. The predicted yield of Bravo was four to six megatons. The actual yield was 15 megatons., some two and a half times what had been predicted.
High Yield Blamed on Error
The unexpected high yield was found to be caused by an error on the part of the designers at the United States Department of Energy Los Alamos National Laboratory in New Mexico. As a result, more tritium was produced than expected, which in fusion with deuterium produced more neutrons than expected and induced more fission of the uranium tamper. Of the 15 megaton yield from Bravo, ten megatons resulted from fission of the natural uranium tamper.
Bravo created a mushroom cloud that reached 50,000 feet and broke 100,000 feet two minutes later. After six minutes, the cloud top peaked at 130,000 feet.
Nuclear Fallout
The fission reactions from Bravo were dirty and produced a large amount of nuclear fallout. Nuclear fallout generally refers to the radioactive dust created when a nuclear weapon explodes. It is the residual radiation hazard that falls out of the atmosphere into which it is spread during the explosion. Because of Bravo’s accidental high yield, this was the largest bomb ever to be tested by the United States and created the worst radiological disaster in US history.
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