5 Nuclear Test Failures Caught on Tape

Castle Bravo was the first of several tests of a brand-new series of high-yield thermonuclear weapons conducted by the US military in the Marshall Islands under Operation Castle. The detonation was the first atmospheric test of a nuke fueled by lithium-deuteride. It was expected to yield a 6 megaton blast, but nuclear engineers were astonished by its ultimate power.

On March 1, 1954, the Castle Bravo detonation produced a 15 megaton yield. In terms of energy released, it was about 1,000 times more potent than the Hiroshima and Nagasaki bombs. The incident became the most powerful nuclear explosion that the United States has ever detonated.

The miscalculation occurred because engineers only considered the lithium-6 isotope to be reactive. This isotope accounted for 40% of the lithium content. The remaining 60% was lithium-7 isotope, which produced a larger neutron flux than expected and contributed to the detonation’s increased yield.

The explosion sent a giant mushroom cloud nearly 22 miles into the air, leaving an enormous 250-foot-deep crater. The radioactive fallout from the blast covered over 7,000 square miles, including the inhabited Rongelap and Utirik atolls. It also spread over the seas, damaging countless maritime flora and fauna.

Evacuation efforts organized by the United States and the United Nations proved too slow to prevent lethal radiation exposure. In the Rongelap atoll, white powder resembling snow fell from the skies while young children played with it.

An hour and a half after the detonation, the radiation remnants reached the Japanese fishing vessel Lucky Dragon No. 5, which was 80 miles east of the test site in the middle of the ocean. 23 crewmembers suffered acute radiation syndrome, and the Japanese government expressed their outrage not long after.

The gaseous fallout continued to spread beyond the Atolls and around the world. Some radioactive material traces were discovered in India, Australia, Europe, Japan, and the United States.

The blast incited international outrage over the morality of atmospheric thermonuclear testing. The fallout from Castle Bravo has also been linked to a bout of several types of cancer such as leukemia and thyroid cancer in the Atolls residents.

Despite the indignation, Castle Bravo's tragic miscalculation did not stop thermonuclear testing. Operation Castle continued with a series of nuclear tests on the Marshall Islands.

During 12 years, between 1946 and 1958, the United States conducted 67 nuclear weapons experiments in the Pacific Ocean.