America’s Disastrous Miscalculation: The Castle Bravo Nuclear Test

America’s Disastrous Miscalculation: The Castle Bravo Nuclear Test

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The Castle Bravo explosion

During the Cold War, the United States and the Soviet Union were involved in an intense nuclear arms race. This involved the testing of atomic weaponry by both sides.

On 1 March 1954 the United States military detonated its most powerful nuclear explosion ever. The test came in the form of a dry fuel hydrogen bomb.

An error of nuclear proportions

Due to a theoretical error by the bomb’s designers, the device resulted in measured yield of 15 megatonness of TNT. This was far far more than the 6 – 8 megatonnes it was expected to produce.

The device was detonated on a small artificial island off of Namu Island in the Bikini Atoll, part of the Marshall Islands, which are located in the equatorial Pacific.

Code named Castle Bravo, this first test of the Operation Castle test series was 1,000 times more powerful than either of the atomic bombs the US dropped on Hiroshima and Nagasaki in World War Two.

Within a second of detonation Bravo formed a 4.5-mile-high fireball. It blasted a crater some 2,000 metres in diameter and 76 metres deep.

Dan sat down with Julie McDowall to talk about Britain's plans in case of nuclear Armageddon during the Cold War. They also discuss the nuclear disaster at Chernobyl and its infamous legacy.

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Destruction and fallout

An area of 7,000 square miles was contaminated as a result of the test. Inhabitants of Rongelap and Utirik atolls were exposed to high levels of fallout, resulting in radiation sickness, but they were not evacuated until 3 days after the blast. A Japanese fishing ship was also exposed, killing one of its crew.

In 1946, long before Castle Bravo, residents of the Bikini Islands were removed and resettled to Rongerik Atoll. Islanders were allowed to resettle in the 1970s, but left again due to contracting radiation sickness from eating contaminated food.

There are similar stories concerning the residents of Rongelap and Bikini Islanders have still yet to return home.

The legacy of nuclear testing

Castle Bravo.

All in all the United States performed 67 nuclear tests in the Marshall Islands, the last of which was in 1958. A UN Human Rights Council report stated that the environmental contamination was ‘near-irreversible’. Islanders continue to suffer due to a number of factors relating to their displacement from their homes.

The most powerful nuclear explosion in history was the Tsar Bomba, detonated by the Soviet Union on 30 October 1961 over the Mityushikha Bay nuclear testing range in the Arctic Sea. The Tsar Bomba produced a yield of 50 megatonnes — over 3 times the amount produced by Castle Bravo.

By the 1960s there was not one place on Earth where fallout from nuclear weapons testing could not be measured. It can still be found in soil and water, including even the polar ice caps.

Exposure to nuclear fallout, specifically Iodine-131, can cause a number of health problems, especially thyroid cancer.

60 th Anniversary of Castle BRAVO Nuclear Test, the Worst Nuclear Test in U.S. History

Washington, D.C., February 28, 2014 &ndash Sixty years ago, on 1 March 1954 (28 February on this side of the International Dateline), on Bikini Atoll in the Marshall Islands, the U.S. government staged the largest nuclear test in American history. The BRAVO shot in the Castle thermonuclear test series had an explosive yield of 15 megatons, 1000 times that of the weapon that destroyed Hiroshima and nearly three times the 6 megatons that its planners expected. To recall this shocking event the National Security Archive posts today a selection of documents about the BRAVO shot and its consequences, mainly from State Department records at the National Archives.

The 15-megaton Castle BRAVO nuclear test, 1 March 1954, created a crater a mile wide and spread radioactive fallout around the world. The mushroom cloud rose to 130,000 feet and broadened to more than 25 miles in diameter. Excerpt from U.S. Air Force documentary film, Joint Task Force 7 Commander's Report, Operation Castle.

Castle BRAVO spewed radioactive fallout around the world and gravely sickened nearby inhabitants of the Marshall Islands, then under a U.S. trusteeship, and 236 were evacuated as well as 28 American military personnel on a nearby island. Twenty-three Japanese fishermen were also contaminated, which made the test known to the world and roiled U.S-Japanese relations. While the U.S. government claimed at the time that a shift in the wind spread the fallout far from the test site, a recent U.S. government report demonstrates that it was the volcanic nature of the explosion that dumped the fallout nearby. The adverse health effects for inhabitants of Rangelop Atoll, 110 miles away from the test site, were severe and some islands remained uninhabitable for years. This radiological calamity had a significant impact on world opinion and helped spark the movement for a nuclear test moratorium which ultimately led to the 1963 Limited Test Ban Treaty.

Included in this posting is a U.S. Air Force documentary film on the Joint Task Force 7 commander's report on the Castle Series. It includes footage of the BRAVO shot as well as coverage of the evacuation of U.S. personnel and Marshall Islanders in the wake of the test. The documentary is sanitized at points apparently to protect nuclear weapons design information. A Freedom of Information request by the Archive for a fresh review and a subsequent appeal failed to dislodge more details.

Documents in this posting include:

  • Japanese government accounts of the Fukuryu Maru incident
  • The May 1954 petition by Marshall Islanders for an end to nuclear tests in the area
  • U.S. Embassy Tokyo telegrams on BRAVO's adverse impact for U.S.-Japanese relations
  • Internal U.S. government consideration of compensation to the Japanese government and the Marshall Islands for losses incurred by nuclear testing
  • Decisions to delay the return of the inhabitants to Rongelap Atoll because of unsafe conditions
  • A comprehensive Defense Threat Reduction Agency report from 2013 on Castle BRAVO exposing "legends and lore" about the test

Source: Document 17: Thomas Kunkle and Bryon Ristvet, Castle Bravo: Fifty Years of Legend and Lore: A Guide to Offsite Radiation Exposure, page 35

Source: Document 17: Thomas Kunkle and Bryon Ristvet, Castle Bravo: Fifty Years of Legend and Lore: A Guide to Offsite Radiation Exposure, page 5.

Why and how exactly U.S. scientists miscalculated the yield remains classified but what made the 15-megaton Bravo shot the worst nuclear test in U.S. history is no secret. The device detonated on an islet in a coral reef, producing massive levels of fallout that quickly reached the stratosphere before falling to earth. It is worth comparing BRAVO to the most powerful nuclear test ever, the Soviet Union's 50-megaton "Tsar Bomba" of 30 October 1961. That test's radiological consequences were far less severe because the "Tsar Bomba's" fireball never touched the earth's surface producing significantly less fallout than BRAVO. Historian of science Alex Wellerstein has written that Castle BRAVO is a "cautionary tale about hubris and incompetence in the nuclear age &mdash scientists setting off a weapon whose size they did not know, whose effects they did not correctly forecast, whose legacy will not soon be outlived."[i]

While the "Tsar Bomba" was almost immediately known to the world, the architects of the Castle test series worked in secrecy the Eisenhower administration wanted to keep words like "hydrogen" and "thermonuclear" out of public discourse and only the fact that tests would be held in the Pacific in 1954 went to the public. After the BRAVO shot occurred, the AEC and the Defense Department sought to control what could be known about the event. But the cat was out of the bag when the Fukuryu Maru crew returned to port which gave Washington a serious damage control problem as information about the 1 March test began to reach the public. At the end of the month AEC chairman Lewis Strauss gave a generally misleading press conference about BRAVO but he managed to alarm the public when he acknowledged that hydrogen bombs could be "made large enough to take out a city … any city."[ii]

Until recently, an extensive collection of documents on nuclear testing in the Marshall Islands was readily available on a Department of Energy Web site, The Marshall Islands Document Collection. It no longer has an on-line presence. In the fall of 2013, at the time of the U.S. government shut-down, this important collection disappeared from the Web. It is unclear whether the Department intends to restore it as a distinct Web page. Many documents on the Marshall Islands can be found on the Energy Department's OpenNet but whether they are essentially the same items is also unclear at present. Moreover other documents on nuclear testing in the Marshall Islands that the Energy Department declassified in the 1990s and were once available at the National Archives or on-line were reclassified early in the last decade after the Kyl-Lott amendment went into effect in 1999.[iii]

Unique non-U.S. government documents about the consequences of nuclear testing in the Marshall Islands are also at risk. The case files of the Nuclear Claims Tribunal for the Marshall Islands, which went out of existence in 2010, are an irreplaceable record of the impact of nuclear testing on a vulnerable population. The collection of paper records resides in a building in Majuro, the Marshall Island's capital city, but no arrangements are in place to assure their long-term preservation.[iv]

America’s Disastrous Miscalculation: The Castle Bravo Nuclear Test - History

Wikimedia Commons The mushroom cloud from the Castle Bravo nuclear test blast at Bikini Atoll, which was 1,000 times more powerful than the bomb dropped over Hiroshima. March 1, 1954.

Bikini Atoll’s isolation had proved a blessing early in its history. The small population of the Pacific island chain — about 1,800 miles from Papua New Guinea, the nearest land mass of note — was free from the conflict of the outside world until the 20th century, when it served as a Japanese outpost during World War II. After the war, the United States took over administration of the atoll, at which point its isolation became a curse.

The U.S. realized that Bikini Atoll’s isolation made it the ideal area for nuclear testing. One Sunday in February 1946, the island’s U.S. military governor asked the locals if they would be willing to temporarily relocate for “the good of mankind and to end all world wars.”

The islanders agreed under the impression they would be able to return to their homes after only a brief period. No one involved thought that, thanks to the nuclear testing, Bikini Atoll would remain uninhabited for more than 70 years.

Carl Mydans/The LIFE Picture Collection/Getty Images Inhabitants of Bikini Atoll prepare to evacuate prior to the Operation Crossroads nuclear weapons test in 1946.

Nuclear testing began that very year with a devastating nuclear test known as Operation Crossroads, but testing was soon terminated due to safety concerns after one of the detonations resulted in a 94-foot tsunami that coated everything in its path with radioactive water.

The entire test fleet, which consisted of old American ships and captured Axis vessels from the war, was sent to the bottom of the atoll’s lagoon, including Japanese Admiral Yamamoto’s flagship, Nagato, where he had received confirmation that the Pearl Harbor attacks were underway.

Wikimedia Commons The USS Saratoga sinks during the Operation Crossroads nuclear testing at Bikini Atoll.

The next series of tests that began in 1954, had devastating if unintended consequences for Bikini Atoll that are still wreaking havoc to this day.

Codenamed Operation Castle, these detonations were meant to test the efficiency of a deliverable hydrogen bomb: one that was small enough to be transported by plane, but had the capability to level an entire city. The result was the Castle Bravo test, which used a bomb 1,000 times more powerful than the one that annihilated Hiroshima. This bomb was the largest U.S. nuclear device ever detonated.

However, two things went horribly wrong with Castle Bravo: the scientists had severely underestimated the yield of the bomb (it would be more than double what they had predicted) and the winds changed during the detonation. Instead of being carried over the open ocean, the radioactive fallout fell over populated areas.

Children on the atolls within range thought that the powdery substance falling from the skies was snow and began to eat it. The islanders were literally covered with the fallout until they were evacuated two days later. The unsuspecting crew of a Japanese fishing vessel 80 miles east of the Castle Bravo test site was also exposed to the fallout. Traces of radioactivity from the blast were later found as far away as Europe.

Wikimedia Commons The crew of a Japanese fishing vessel was unintentionally exposed to nuclear fallout from the Castle Bravo test at Bikini Atoll.

Although nuclear testing in Bikini Atoll officially ended in 1958, the high levels of radiation prevented the inhabitants from returning until more than a decade later, when President Johnson promised that the U.S. would work to ensure they could go back to their homeland. An eight-year plan was prepared that included the replanting of crops and clearing of radioactive debris.

The islanders finally began to return home in the early 1970s, nearly 30 years after the testing had begun. However, during routine surveillance in 1978, the U.S. found that the inhabitants of Bikini Atoll were exhibiting dangerously high levels of radioactivity and the entire population once again had to be evacuated. They would not return.

Today, the danger of living on Bikini Atoll comes from consuming contaminated food or water there is no real risk in simply walking around the islands, although the crater from the blast is still visible from the air.

In an attempt to make amends for Castle Bravo, Operation Crossroads, and all of the nuclear testing at Bikini Atoll, the U.S. set up a series of trust funds amounting to millions of dollars to provide for the islanders whose homes had been destroyed.

And the testing has also given the islanders a new source of income, albeit one that comes nowhere close to making up for the damage done: Some locals now run diving tours through a graveyard of World War II battleships left on the ocean floor thanks to Operation Crossroads some 70 years before.

After this look at Bikini Atoll, Operation Crossroads, and Castle Bravo, read up on the Halifax Explosion, history’s largest blast before nuclear weapons. Then, see some astounding photos that document the United States’ reckless history of nuclear testing.

Biggest Bangs: 5 U.S. and Russian Nuclear Tests that Shook the World

The first-ever hydrogen bomb blast, Ivy Mike, required American weaponeers to create an vast new industrial capacity for manufacturing liquid hydrogen in its "heavy" form of liquid deuterium.

By early 1954, hot on the heels of the Korean conflict, the United States had new H-bomb designs ready to test. The six-shot series of Operation Castle would prove these new designs at Bikini Atoll. As with Operation Ivy, an armada of ships and an army of people shipped out the Central Pacific to dredge islands, build test equipment and ready bunkers.

The bombs prepared included a weaponized version of the Ivy Mike device—the liquid-fueled EC-16 hydrogen bomb, along with others trying out the new American dry fuel made of mixed Li-6 and Li-7 hydride. Scientist thought Lithium-6 was far less reactive to neutrons thrown from fission primaries and thus expected yields of six to ten megatons.

Nature (only partly) surprised them on the first test. The Castle Bravo shot yielded fifteen megatons—the biggest American nuclear test ever—and the worst radiological disaster in American history. It was two hundred and fifty times bigger than Hiroshima, Castle Bravo vaporized an island, contaminated three atolls and hundreds of people, caused major diplomatic incidents and introduced the word “fallout” into public discourse.

The size of the explosion resulted from Li-6's previously-unknown affinity for neutrons the supposedly regular-gas bomb fuel turned out to be premium hi-test. Nature wasn't involved in another factor, the wind: despite warnings from meteorologists Test Director Alvin Graves ordered the shot fired. Graves, who had survived near-lethal radiation exposure, had little patience with those urging caution.

Despite the disaster the U.S. military carried on with Operation Castle, and conducted two of the other three biggest American tests. Unlike the land-based and heavily instrumented Castle Bravo test, Castle Romeo tested a weapon in its bomb casing mounted aboard a barge afloat in Bikini’s lagoon. The first test destroyed most of the test equipment on Bikini, and big test were blowing holes in Bikini’s reef. Because it used pure Li-6 hydride the Romeo shot was almost canceled it became the third biggest American test at eleven megatons yield.

Castle Yankee was the second biggest American test at 13.5 megatons. As the fifth test of Operation Castle, Yankee again used a bomb casing on a barge, and again used the Li-6/Li-7 mixed fuel used in Castle Bravo. The 13.5 megaton blast produced a fireball four miles wide 2.5 megatons of the 13.5 came from pure fusion alone.

The Castle Bravo, Romeo and Yankee tests proved the H-bomb design that became the first U.S. “city-killers”: high-yield thermonuclear weapons capable of completely destroying a target even if the weapon missed by miles. These Mk17 and Mk 24 bombs looked the part—nineteen feet long, five feet wide, ten tons heavy—big enough for a cowboy to ride into Armageddon.

Weapons development moved fast during those years. Only four years after Operation Castle, Operation Hardtack came to Bikini and Eniewetak Atolls as American weaponeers raced to test refined H-bomb designs before an unofficial testing moratorium announced by President Eisenhower. Hardtack Poplar, the fifth biggest American nuclear test, yielded 9.3 megatons from a bomb that would become the biggest ever deployed by the United States: the Mk-41 twenty-five-megaton three-stage device.

Hardtack Poplar tested only the first two stages, resulting in a very “clean” explosion—one with far less fallout. The third stage of the operational weapon was a internal casing of fissile uranium containing the first two stages the immense neutron flux from the second-stage fusion explosion causes the third stage to fission and produce huge amounts of energy and radioactive waste. In Poplar the uranium casing was replaced with an inert lead one.

After Operation Hardtack the moratorium on testing delayed new designs, and when US testing resumed in 1962 no tests greater than four megatons are conducted. The United States turned to underground tests at the Nevada Test Site which is unable to contain megaton-class shots. The last known U.S. multi-megaton shot was Cannikin—a five-megaton blast a mile beneath Amchitka Island in the Aleutians.

Really huge nuclear weapons fell out of favor in America as missile accuracy increased. More accurate delivery platforms mean less need for big explosions to kill a target (and smaller delivery vehicles—a big warhead needs a big missile or plane or sub). But historian Alex Wellerstein notes that American bombs could have gotten much, much more powerful without growing bigger:

“By 1962, after the Dominic series, they thought they might be able to pull off 50 Mt in only a 4,500 kg (10,000 lb) package—a kind of ridiculous 11 kt/kg ratio.”

Could there have been a five-ton fifty Megaton bomb? It’s just as well that it was never (knowingly) explored. After all, the genie, however great, never stays in the bottle.

Steve Weintz, a frequent contributor to many publications such as WarIsBoring, is a writer, filmmaker, artist and animator. This article first appeared several years ago.

Castle Koon

Koon was the first thermonuclear device to be designed by UCRL (now Lawrence Livermore), and was the last weapon design on which Edward Teller directly worked. It was a fizzle - with a predicted yield of 1 megaton its actual yield was only 110 kt. Of this, 100 kt was from fission (almost entirely due to the primary), only 10 kt of energy was contributed by fusion reactions.

The test device was name Morgenstern ("morningstar"). It had a somewhat more complex internal design than the Los Alamos devices and was intended to break new ground in weapon design. Diagnostics indicated an unexpectedly long time delay between the primary firing and the secondary ignition. Reportedly this was due to a simple design flaw - the neutron flux from the primary had pre-heated the secondary leading to poor compression. Other devices tested in Castle contained boron-10, which may have served as neutron shield to reduce this pre-heating effect. In any case, the failure of this dry fueled design also led to the cancellation of the test for its cryogenic sister device - the Ramrod.

Below is a map of Eninman Island before and after the Koon shot. The crater was 990 feet wide and 75 feet deep. Remember, Koon was a fizzle ! A successful shot would have obliterated most of the island.

As a species, humans have progressed tremendously in the past 10,000 years. We can now fly, talk to loved ones across the globe, access information on remote locations, study the human body and our planet earth with the most sophisticated technological instruments. We not only have landed on the moon and timed the landing with the precision of a second, but have robots investigating Mars for suitability of life. We have satellites looking down on us providing the most astounding views of planet earth. This is just the tip of the iceberg.

The purpose of this article, however, is not to rest on our laurels but to scrutinize the mistakes we have made in the past. This article is intended to provide young professionals globally with a critical perspective of mistakes humans have made in hope that we learn from them.

Very few mistakes we have made as a race come close to the abuse of the most powerful bomb ‘The Atom Bomb’. Though World War II ended with the atomic bombing of Japan, it instigated an arms race known as “the cold war” between the Capitalistic Bloc i.e. The United States and NATO allies and the Eastern Bloc i.e. The Soviet Union and the Warsaw pact allies, which encouraged both sides to build powerful atomic weapons. The scientists and engineers in United States and Soviet Union had only one purpose: To build more powerful nuclear bombs.

In this article we review some of the critical events and lessons learnt.

6 August 1945: The atomic bombing of Hiroshima takes place. After sometime, a second bomb is dropped on Nagasaki by the United States. This basically ends World War II killing 150,000 people! But a lot more people die as a result of radiation from the bombing. This marked the beginning of the era of mass destruction. Joseph Stalin, the then General Secretary of the Soviet Union and the Dictator of the State decides he too wants to own a nuclear weapon, the Atom Bomb.

20 August 1945: Stalin orders Russian scientists and engineers to build him an Atom Bomb.

1946: U.S decides that it will test all its nuclear weapons on an Island 2700 miles southwest of Hawaii, Bikini Atoll. The native people living there are moved to a different island. A fleet of 90 Japanese, American and German warships are assembled in a lagoon near the island to witness the power of the Atomic Bomb.

25 July 1946: The first test of the Atom Bomb is conducted and all warships assembled in the vicinity are destroyed. At this point, only the United States knows how to build an Atomic Bomb.

29 August 1947: The Soviets tested their first Atom Bomb which was a copy of the Nagasaki bomb. The likeness was so much that it was believed that there were spies in the Los Alamos Project making the Atomic Bomb in United States.

1950: The spies are caught and 4 days after, the United States announces that it will design even more powerful weapons. The need to strike balance created a great rush in design exercises which resulted in the creation of the Hydrogen Bomb. The first Hydrogen Bomb intends to draw power from a fission reaction unlike the earlier Atom Bombs which worked as a result of a fusion reaction (splitting of atoms under immense pressure releasing vast amounts of energy i.e. 20 Kilotons which is equal to 20,000 tons of TNT). In comparison, the energy released from a Hydrogen Bomb is measured in Megatons (Millions of tons of TNT). At this point the US scientists and engineers believed that it is only a matter of time before the Russians will catch up. So now it is up to the Los Alamos scientists and engineers to build the world’s first thermo-nuclear bomb, the Hydrogen Bomb, codenamed ‘MIKE’.

1 November 1952: The first Hydrogen Bomb is tested, the world’s first man made thermo-nuclear reaction. But it weighed 82 tons and was not of much use.

12 August 1953: There is intense debate as to which group created the first portable Hydrogen Bomb. There is still debate to this day. But it is strongly believed that the Soviets built it. Could the United States do the same?

March 1954: 6 months later, Los Alamos answers the Soviet Union by creating a Hydrogen Bomb from solid fuel made from the lightest metal on earth, Lithium, specifically Isotope Lithium 6. America’s super bomb is codenamed ‘Castle Bravo’. The bomb was only tested with liquid Hydrogen and not Lithium 6 which resulted in incorrect calculations. Even then, United States decides to test Castle Bravo on the northwest side of the Bikini Island. The bomb is to be triggered from the island of Enyu, 20miles away, from a water tight bunker protected by reinforced concrete and massive doors. 48 hours before triggering, all personnel except the firing men, are removed from Bikini Island. The expected energy from the explosion is 5 Million tons equivalent of TNT. If the explosion produces a higher energy release, no one within the 20 mile radius will remain alive.

Question to consider: Why did the US test a bomb which they knew was never simulated with liquid hydrogen? Isn’t it an obvious lesson to never execute without thorough testing, especially when it’s the case of a bomb? It was poor judgement on behalf of the United States to ever test the Hydrogen Bomb without full knowledge.

1 March 1954: Castle Bravo is tested. The energy, heat and light from the explosion was so high that personnel on a ship 23 miles away could see the bones in their bodies. The aftershock produced a Tsunami. The explosion even got so close to the bunker that the concrete walls creaked. So what went wrong? Castle Bravo was not only made up of 30% Lithium 6 but also 70% Lithium 7 which was thought to be inert. However, on post analysis it was confirmed that the explosion went out of control and as a result, Lithium 7 became radioactive. This was something the scientists and engineers were not aware of, but should have been. Castle Bravo was designed to yield 5 Megatons of TNT, but because of the miscalculation, it resulted in an explosion of 15 Megatons of TNT. It also was directed towards Japan, another unexpected variation in the explosion that was not as per designs. There was a national outcry over radiation effects that not only affected people but also marine life.

Question to consider: How much bomb testing is too much testing when it comes to destruction of natural resources? I think that considering that both parties, the US and Soviet Union, acted on fear alone of being bombed by nuclear weapons, it was already time to stop creating more powerful bombs.

Before and After the Castle Bravo explosion on Bikini Island, Image courtesy of

1960s specifically 1961: By this time, United States has all the necessary technology and expertise needed to build bombs of all sizes, ranging from a few kilotons to megatons capacity. It was also in this time, that Soviet Union scientists and engineers started building long range missiles in response to the Castle Bravo. Relations between US and Soviet Union deteriorate even further. At this time, John F. Kennedy was sworn in as the 35 th president of the United States.

July 1961: President Kennedy decided to station half of the bombers in Europe on more alert. This freightened Nikita Khrushchev, the First Secretary of the Central Committee of the Communist Party of the Soviet Union who then called on Russian scientists and engineers to show US what the Soviet Union is capable of. He wanted the biggest bomb ever made in history dubbed the Tsar Bomb meaning the King of Bombs. The Castle Bravo exploded at 15 Megatons, but the Tsar was designed to explode at 50 Megatons.

30 October 1961: The seismograph in the US Military Monitoring Station in Alexandria, VA records a massive surge of activity. But the origin of this surge is not an earthquake, it is from a location inside Soviet Union territory. The only explanation to this event is that the Soviets have built a bomb more powerful than the United States ever had, a 50 Megaton weapon deliverable. This is 4000 times bigger than the Hiroshima atomic bomb.

The Soviet Union tested the Tsar Bomb. The most powerful bomb ever made by man, created a mushroom cloud which peaked at 40miles, around 7 times the height of Mt. Everest. Buildings 70 miles away were destroyed, and windows shattered 300miles away. Analysis state that if the Tsar Bomb was detonated on Washington D.C. from an optimum height of 2000 Ft, the initial fireball will kill everything and everybody within 3 miles, people 12 miles away would suffer 3 rd degree burns, most building 20miles will be destroyed killing 1 Million people instantly and 3.5 Million in total.

The scientist who designed the Tzar Bomb estimated that 500,000 worldwide will suffer in the coming decades if the radiation deposited by the huge cloud slowly disappeared. The fallout of the Tsar Bomb is still classified. The United States test zone Bikini Island as of 1970 is still radioactive.

1963 –Finally both sides agreed to a Test Ban Treaty performing all further tests underground to avoid fallouts.

So what can Young Professionals learn from this experience today? We can learn that progress for the sake of progress is not as great an idea as it may first seem, that progress at any cost often results in very high costs paid by countries and people of the world. Our lessons learnt are also that politicians must not drive technological progress the way they did during the Cold War. Building such weapons in the name of protection of one’s own countrymen does not make them any less destructive to neither man nor nature. So as scientists and engineers, if we have the capability of building such technology, technology that has the capacity for mass destruction, then it is our duty to ensure that all steps are taken to avoid mass destruction. Power against power and meaningless wars only create destruction of our world as we know it.

The accident [ edit | edit source ]

It was an utter technological disaster! The plan was to have a blast with an expected yield of 4 to 8 megatons (with 6 Mt being officially predicted), but the actual yield far exceeding this with a blast of 15 megatons.

Radioactive fall out was horrendous spread over thousands of miles in the western and central Pacific, contaminating several small islands like Rongerik, Rongelap and Utirik.

The immediate injuries were on the American aircraft carrierUSS Bairoko, were 16 crew members received beta burns.

2 thoughts on &ldquoMarshall Islanders Remember ‘Castle Bravo’ Nuclear Bomb With Honolulu Veterans and Supporters&rdquo

A friend of my parents, who lived down the street from us, was in the Navy during that time. He was on board one of the Navy ships that was in the area when a nuclear bomb test was fired off. He, and other sailors, were told to look toward the blast area, and remained on that ship throughout the exercises.

I can remember him having tremendous boils on the back of his neck.

He passed away from cancer in the 1960’s.

I never knew about the blasts at the Marshall Islands. The US should compensate the Marshall Islanders but won’t. We are always taught by the Media and US History Classes that the Americans have always been the good guys and its enemies the bad guys. We are also taught democracies don’t do bad things to other countries and only authoritarian governments do that. It’s the media’s job to inform you, they sometimes misinform you.

Those Who Witnessed Castle Bravo Looked Into Armageddon

More than 60 years ago on an island in the South Pacific, scientists and military officers, fishermen and Marshall Islands natives observed first-hand what Armageddon would be like.

And it almost killed them all. The Atomic Energy Commission code-named the nuclear test Castle Bravo.

The March 1, 1954 experiment was the first thermonuclear explosion based on practical technology that would lead to a deliverable H-bomb for the Air Force’s Strategic Air Command—part of the Operation Castle series of tests needed to manufacture the high-yield weapons.

Bravo was the worst radiological disaster in American atomic testing history𠅋ut the test provided information that led to a lightweight, high-yield megaton bomb that would fit inside a SAC bomber.

Widespread contamination sickened and exiled Pacific Islanders and killed a Japanese citizen. The United States had to admit it possessed the ability to make deliverable H-bombs𠅊n information windfall for the Soviet Union, and the catalyst for serious consideration of a ban on atmospheric nuclear tests.

Bravo’s fallout even inspired the creation of a science fiction screen legend Godzilla. In the 1954 Japanese movie of the same name, atomic testing resurrects the “King of Monsters”𠅊 symbol for the new terror felt in the only nation ever attacked with nuclear weapons.

Perhaps most importantly, Bravo forced many scientists and military officers to concede how deadly nuclear weapons really were—not just in their immediate effects such as blast and intense heat, but the lingering effects of high-energy radiation.

“I think the most important message we might take away from the Castle Bravo shot is the amount of hubris it represents,” Alex Wellerstein, a historian at the Stevens Institute of Technology and blogger, told War Is Boring.

“The scientists and military assured the politicians and Marshallese people that it was a safe experiment, that they had things under control, that they understood what would happen. And they were very wrong.”

The Bravo shot in 1954 was not the first test at Bikini Atoll, part of the 140,000-square-mile Pacific Proving Grounds. Nor would it be the last𠅏rom 1946 to 1958, the U.S. government held 67 atmospheric tests there.

Only two years earlier, the Ivy Mike shot demonstrated the first true thermonuclear reaction. It produced a 10-megaton yield, but the device relied on cryogenic liquid hydrogen isotopes that were bulky, required refrigeration equipment that weighed tons and was almost impossible to store in a weapon.

A prototype “wet fuel” bomb based on the Ivy Mike test was 24 feet long, five feet wide and weighed 30 tons. It was more like a railroad box car than a deliverable weapon. But Bravo used lithium deuteride 𠇍ry fuel,” which is solid and lightweight at room temperature.

Scientists estimated the device would have a yield of about five megatons. They based many of their safety precautions—such as the location of various observation posts and ships, a safety 𠇎xclusion zone” in the Pacific Ocean surrounding Bikini and estimates of fallout dispersal—on a five-megaton yield.

Above�stle Bravo. U.S. government photo. At top—the explosion’s fireball and mushroom cloud photographed from more than 30 miles away. Los Alamos National Laboratory photo

Zero hour for Bravo was at 6:45 a.m. local time on March 1. From the moment the device detonated, many of the observers knew something had gone spectacularly wrong.

The flash from the nuclear explosion was overwhelming, even by the standards of nuclear explosions. Men saw their bones appear as shadows through their living flesh. Streams of blinding light shone through the smallest cracks and pinholes in secured doors and hatches.

Bravo’s thermal radiation was far more intense than expected. More than 30 miles away from Ground Zero on Bikini Atoll, sailors on board Navy ships said the heat was like having a blowtorch applied to their bodies.

The shock wave destroyed buildings supposedly outside of the calculated damage zone. It nearly knocked observation aircraft out of the sky, and caused some men inadvertently trapped in a forward observation bunker to wonder if the explosion ripped their concrete and steel shelter from its foundations and flung it into the sea.

Then there was the fireball.

It was four miles in diameter and hotter than the surface of the sun. The Bravo fireball rose at the rate of 1,000 feet per second, and created a mushroom cloud that eventually topped 130,000 feet above sea level.

“In mere seconds the sailors sensed that something unspeakably wrong was occurring … Battle-hardened men who had served in World War II went to their knees and prayed,” L. Douglas Keeney wrote in 15 Minutes: General Curtis LeMay and the Countdown to Nuclear Annihilation.

“We soon found ourselves under a large black and orange cloud that seemed to be dropping bright red balls of fire all over the ocean around us,” one sailor recounted. “I think many of us expected that we were witnessing the end of the world.”

Later, scientists calculated that Castle Bravo’s yield was actually 15 megatons.

The reason? A “tritium bonus” occurred during the thermonuclear reaction. Cascading neutrons transformed the lithium-7 isotope—that comprised most of the 𠇍ry fuel”—into tritium and helium.

Tritium causes extremely energetic fusion.

It was the thermonuclear equivalent of throwing gasoline on a small blaze and producing an instant conflagration.

Bravo’s yield was 1,000 times greater than the Hiroshima bomb, far bigger than the scientists had planned. To make matters worse, meteorological forecasts predicted that high-altitude winds would blow the radioactive fallout away from inhabited areas.

Instead, the wind blew the radioactive cloud toward them.

Fallout from Bravo rained down on ships and sailors. Ships’ captains ordered entire crews below decks, and sealed their vessels for days in an effort to escape contamination. Fallout dusted U.S. service members stationed on nearby Rongerik Island.

Fallout maps showing dispersal of Bravo’s radioactive plume and the distance it traveled from Ground Zero. Illustration via permission from

Restricted Data: The Nuclear Secrecy Blog

The plume blanketed Marshall Islanders on Rongelap, Ailinginae and Utirik atolls downwind from Ground Zero. Unaware of the danger, children played in the radioactive dust, while other islanders licked it off their hands and arms because they thought it was snow.

And if things weren’t bad enough, fallout contaminated the Japanese fishing boat Fukuryu Maru, exposing the 23-man crew to high levels of radiation. One crewman died from radiation exposure, which provoked international outrage and a diplomatic crisis between the U.S. and Japan.

After the Fukuryu Maru incident became known, the U.S. Navy expanded the exclusion zone around the Pacific Proving Grounds to 570,000 square miles. However, the proving grounds and exclusion zone were so huge, it caused serious problems for the Japanese fishing industry.

The U.S. and Japan eventually resolved their diplomatic differences, and the U.S. agreed to pay more than $15 million in compensation to the Fukuryu Maru survivors.

The Marshall Islanders hit by fallout experienced numerous health problems for decades after the Bravo shot, including birth defects and thyroid cancer.

Eventually, natives evacuated from the contaminated islands, returned briefly, and then evacuated again because of concerns about lingering radiation. The natives are still in exile.

“We are sadly more akin to the Children of Israel when they left Egypt and wandered through the desert for 40 years,” Bikinian representative Tomaki Juda said during a media conference in 2014 commemorating the 60th anniversary of Bravo. “We left Bikini and have wandered through the ocean for 32 years and we will never return to our Promised Land.”

In 1990, Congress passed the Radiation Exposure Compensation Act. The Justice Department can make a one-time payment of $75,000 to an 𠇊tomic veteran” for a nuclear testing-related illness. However, government records indicate that fewer than three percent of atomic veterans have made a claim.

In 1963, the United States signed the Limited Test Ban Treaty that prohibited atmospheric testing of nuclear weapons.

“I think we should also make sure not to let short-term national security fears keep us from being methodical and careful about our thinking and actions,” Wellerstein said. “The reason Bravo got so far wrong is because small errors in understanding, under certain circumstances, can get magnified greatly.”

Castle Bravo – What You Need to Know About the Largest Thermonuclear Bomb America Ever Detonated

When it comes to Nuclear bombs there’s large and then there’s Castle Bravo. On March 1st, 1954 the United States detonated the largest Thermonuclear weapon in the world birthing a blast that wouldn’t be topped for nearly 10 years. To this day, it holds the spot as the largest explosion ever caused by the United States and sits as the fifth largest man-made detonation of all time. This is the story of how the Castle Bravo bomb stunned researchers and brought about an international call to ban such thermonuclear testing.

The First Lithium Deuteride Fueled Nuke for the U.S.

The United States knew Castle Bravo would be a groundbreaking weapon. The bomb was the first of its kind in the United States Arsenal as a Lithium deuteride fueled Thermonuclear Bomb. Bravo was developed at the infamous Los Alamos Research Lab (you’ll remember them from our episode The Demon Core). Its unique fuel was solid at room temperature. A one-of-a-kind cooling system liquefied the Lithium deuteride at the time of detonation. This allowed the weapon to be more effective and lightweight. However, this fuel choice would lead to a detonation beyond anyone’s expectations.

The Detonation

Researchers planned to test the bomb on an artificial island built at Bikini Atoll, the long-running U.S. nuclear test site. A single second after detonation Castle Bravo formed a fireball 4 and a half miles in diameter. At its peak, the mushroom cloud reached a height of 130,000 feet and a diameter of 62 miles. To put the massive scale of this explosion in perspective, the cloud stretched nearly 10 miles outside of the Ozone layer and within 10 miles of exiting the stratosphere. Manhattan could stretch across the diameter of the blast 5 times over. When the dust cleared a crater 250 feet deep and 6,500 feet wide was left in the earth. Contaminants from the event would span over 7,000 square miles.

Bikini Atoll became a Nuclear Test site in 1946 when the first test was conducted on the islands.
Photo by Science in HD on Unsplash

Within seconds of the blast researchers observing the controlled detonation immediately knew that something was wrong. Scientists knew this bomb was big, but no early estimates came anywhere near the size of the blast that they had just witnessed. People tell rumors today that the rays from the bomb allowed the researchers to see the bones in the others observing the event. So, what went wrong?

It Needs to Be At Least Three Times as Big

Designers of the thermonuclear bomb expected a yield of 5 megatons from the blast. Castle Bravo bore a yield of 15 megatons, 3 times the expected blast size. This wasn’t a mathematic error, it was an underestimate of the reaction of the lithium-7 making up the lithium deuteride fuel. Scientists assumed that the lithium-7 would dissolve through the process of fission. However, rather than dissolve the element created an extra neutron. Making up nearly 60% of the fuel the reaction from the lithium-7 lead to an additional 10 Mt of explosive force.

The Fallout

Under the originally expected conditions, the fallout of this nuclear test would have been wide-ranging. The United States selected the location of the test to be far enough from any human settlement to avoid any harmful effects of radioactive fallout. The exponential increase in blast size coupled with an unexpected wind shift on the day of the detonation triggered a dangerous situation that spanned from the Marshall Islands to Japan.

In the years after the test, thousands of island people groups suffered serious health conditions as a direct result of fallout from Castle Bravo. Los Alamos conducted Operation Castle in secret but the effects of the test gained international attention quickly. Countries around the world called to ban atmospheric thermonuclear testing. The calls after the blast did not cease nuclear testing. Tests would continue for 40 years, even after the Tsar Bomba was detonated by Russia and unleashed nearly 5 times the energy of Castle Bravo sending a shockwave that circled the planet three times.


Castle Bravo was a mistake. A mistake that created a bomb significantly more powerful than anyone expected. People across the pacific suffered serious health consequences from the Castle Bravo detonation. Also, the blast destroyed miles of underwater wildlife habitat including much of the coral reefs at Bikini Atoll. Thankfully, the Comprehensive Nuclear Test Ban Treaty has banned the above-ground testing of such weapons. Hopefully, a detonation like this will never again transpire.


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