Castle Bravo was the code name given to the first U.S. test of a dry fuel thermonuclear hydrogen bomb device (the first practical deliverable hydrogen bomb in the U.S. nuclear arsenal), detonated on March 1, 1954 at Bikini Atoll, Marshall Islands, as the first test of Operation Castle. Castle Bravo was the most powerful nuclear device ever detonated by the United States (and just under one-third the energy of the most powerful ever detonated), with a yield of 15 megatons, about 1,000 times more powerful than the Hiroshima or Nagasaki atomic bombs.
A several mile-wide fireball erupted within seconds, visible 250 miles away. A Lucky Dragon fishing boat crew member described the sight as the Sun rising in the west. The crater formed was 6,500 feet in diameter and 250 feet deep. A mushroom cloud 47,000 feet high (nearly 9 miles high) and 7 miles in diameter formed within a minute. The mushroom cloud grew to 130,000 feet high (nearly 25 miles high) and 62 miles in diameter in less than 10 minutes, expanding at 100 meters per second (or 220 miles per hour).
That yield, far exceeding the expected yield of 4 to 6 megatons (due to a theoretical physics error), combined with other factors, led to the most significant accidental radiological contamination ever caused by a United States nuclear weapon test. Fallout from the detonation — intended to be a secret test — poisoned the islanders who had previously inhabited the atoll and returned there afterwards, as well as the crew of Daigo Fukuryū Maru ("Lucky Dragon No. 5"), a Japanese fishing boat, and created international concern about atmospheric thermonuclear testing.
The cloud contaminated more than 7,000 square miles of the surrounding Pacific Ocean, including dangerous levels of radioactive fallout over an area hundreds of miles long, including surrounding inhabited islands like Rongerik, Rongelap (100 miles downwind), and Utirik (300 miles downwind). Downwind Marshall Islanders suffered doses as high as 200 Rems, and thus immediate -- as well as latent -- health impacts, including radiation poisoning, and later birth defects and thyroid tumors (children on Rongelap later suffered 90% thyroid tumor rates, beginning just a decade later). In 1964, the U.S. government admitted responsibility and provided some compensation.
Some attribute the radiological incident to moving Nevil Shute to write the 1957 novel On the Beach.
As described on the Wikipedia site for Godzilla, "With the nuclear bombings of Hiroshima and Nagasaki and the Lucky Dragon 5 incident still fresh in the Japanese consciousness, Godzilla was conceived as a metaphor for nuclear weapons."
The American magazine Consumer Reports began warning about atmospheric bomb tests’ Strontium-90 fallout contaminating milk supplies.
The documentary film Nuclear Savage chronicles the experience of Marshall Islands under U.S. nuclear weapons testing: "a Pacific island paradise...until the United States tested nuclear weapons and conducted secret human radiation experiments. Experiments that would remain top-secret for decades..."
As Beyond Nuclear's Kevin Kamps described in his "70 Years of Radioactive Risks in America and Japan," presented at Helen Caldicott's conference, Medical and Ecological Consequences of the Fukushima Nuclear Accident, held at the NY Academy of Medicine on the second anniversary of the beginning of the Fukushima catastrophe, the death of a Lucky Dragon #5 crew member, as well as the sale and consumption of radioactive tuna throughout Japan, outraged the Japanese people, less than 9 years after Hiroshima and Nagasaki. Unprecedented, large protests followed. The U.S. and Japanese governments were concerned that Japan would "go communist." The U.S. CIA was deployed to Japan, to sell "Atoms for Peace" to the Japanese people, in an effort to calm the protests. The CIA recruited an agent, Shoriki, a Class A War Criminal, owner of Japan's biggest newspaper and t.v. station, to sell "Atoms for Peace" to the Japanese people. He was wildly successful. This is how the Nuclear Village, and the Nuclear Safety Myth, were born in Japan, ultimately leading to Fukushima Daiichi nuclear catastrophe. See Kevin's Power Point presentation, slides 12 to 16 (including the accompanying notes), for more information.
The National Security Archive at George Washington University has just released documents about the Castel Bravo disaster never made public before.
As reported by the Asahi Shimbun, a nuclear evacuee from Fukushima Daiichi nuclear power plant's host town (now a ghost town), 21-year-old Keiko Takahashi, has traveled to the Marshall Islands to meet with survivors of the U.S. H-bomb disaster. She was joined there by 80-year-old Matashichi Oishi, a surviving crew member from the Lucky Dragon No. 5 fishing boat. As the U.S. has failed to decontaminate their former ancestral homelands in six long decades, many Marhsall Islander nuclear evacuees have lost hope of ever returning to their former homes, although they nonetheless strive to keep their traditional culture alive in their new homes.
“A clue to achieving a nuclear-free world will be found when people who suffered damage join hands, share lessons and face challenges,” Takahashi said.