The US military unleashed its largest nuclear blast in tests 69 years ago, but scientists had no idea the blast would be so large

• Between 1946 and 1958, the US conducted dozens of nuclear tests in the Pacific.

• The largest of these was the detonation of the Castle Bravo device on March 1, 1954.

• It was 1,000 times more powerful than the atomic bomb that leveled Hiroshima during World War II.

The U.S. military tested dozens of nuclear weapons in the Pacific in the years following World War II, but none of the explosions matched in magnitude that of the Castle Bravo test – what a nuclear weapons historian once was called “the largest single radiological disaster in American history.”

The Castle Bravo device was the largest nuclear weapon ever tested by the United States. On March 1, 1954 – Wednesday exactly 69 years ago – the military detonated this bomb in Bikini Atoll, a small coral reef in the Marshall Islands.

The radioactive fallout from the blast was far worse than expected and a high-profile incident that raised questions about the development of atmospheric tests, a nuclear weapons expert told Insider.

Castle Bravo was the first of six weapons to be tested as part of a week-long series of long-range thermonuclear device experiments — also known as Operation Castle — that spanned March 1 through May 31, 1954. The 23,500-pound device created a mushroom cloud that reached a height of 130,000 feet and left a crater that was 250 feet deep and over 6,500 feet wide.

But scientists grossly misjudged the yield, predicting it would only produce an explosive yield of at most six megatons, the researchers said Brookings Institute. Little did they know that the fusion fuel would have such a large impact on the bomb’s detonation.

The detonation produced an actual explosive force of 15 megatons, the Department of Defense said in Operation Castle data sheetmeaning it was 1,000 times more powerful than the atomic bomb that leveled Hiroshima, Japan, at the end of World War II.

“It got a lot worse”

Castle Bravo also produced a significant amount of radioactive fallout that had adverse effects for years. Radioactive material fell on Marshall Islanders and was even found in communities thousands of miles away, causing serious illnesses, and American military personnel were tasked with cleaning up nuclear testing exposed by contaminated food and dust causing lasting health problems.

The story goes on

A Japanese fishing vessel that was sailing about 80 miles from the Castle Bravo test site on the day the Castle Bravo device was detonated was exposed to radiation that eventually killed one sailor and left others on board with radiation poisoning, the authorities said Atomic Heritage Foundation. And nearly 40 US Navy sailors who were exposed to the fallout suffered skin injuries, according to the Department of Defense written down.

Whenever the military prepared for a nuclear test, they established a containment zone to prepare for the radioactive fallout that followed after the device detonated. But when a bomb produces a greater explosive force than expected, those earlier assumptions about safety can be jeopardized, Hans Kristensen, the director of the nuclear intelligence project at the Federation of American Scientists, told Insider.

“Of course, what happened after Bravo was that much of the fallout was greatly amplified and drifted over a much larger area than expected,” Kristensen said. “Fallout was expected to have a significant impact anyway. But that made it a lot worse.”

The fallout resulted in serious health effects for Marshall Islands residents, although it’s unclear exactly how many people were affected by the testing. The National Cancer Institute found that some cancers in residents who survived years of nuclear testing can be traced to radiation exposure. Castle Bravo alone was responsible for almost all of the radiation doses in the country’s northern atolls.

A 2019 report of the Republic of the Marshall Islands’ National Nuclear Commission said nuclear weapons tests – like Castle Bravo – have had disastrous effects on the country’s environment, and some people still fear daily how their long-term exposure to the radiation could affect their health.

“There was a real impact on the people living on the surrounding islands,” Kristensen said. “And those consequences have been very serious,” and long-lasting, he added.

Castle Bravo was a real “eye opener”

Despite the devastation caused by Castle Bravo, the US military continued to conduct nuclear weapons tests in the Pacific. A total of 67 tests were conducted between 1946 and 1958.

But the incident helped the US – and the world community – realize the serious dangers involved in this particular type of testing, as the continued detonations of nuclear and hydrogen bombs led to increased concerns about the effects of radioactive fallout.

A year later, in 1955, the United Nations established the Scientific Committee on the Effects of Atomic Radiation instructed monitoring the effects of radiation exposure and assisting governments and organizations in developing protective measures and evaluating radiation risk.

The USA, Great Britain and the Soviet Union signed it Limited Test Ban Treaty 1963, which banned nuclear weapons testing in the atmosphere, in space, and under water. The agreement was the first of several which targeted nuclear weapons during the Cold War era but did not ban underground testing. The follow-up treaty on the comprehensive nuclear test ban was signed in the 1990s.

“It definitely contributed to that realization that maybe atmospheric nuclear testing isn’t that smart,” Kristensen explained, adding, “It was kind of an eye opener, I think, for the global community as well.” I mean, it was so powerful and devastating that it really helped move that forward.”

Continue reading the original article Business Insider