Nuclear testing at Bikini Atoll
Nuclear testing at Bikini Atoll consisted of the detonation of 23 nuclear weapons by the United States between 1946 and 1958 on Bikini Atoll in the Marshall Islands. Tests occurred at seven test sites on the reef itself, on the sea, in the air, and underwater. The test weapons produced a combined yield of about 77–78.6 Mt of TNT in explosive power. After the inhabitants agreed to a temporary evacuation, to allow nuclear testing on Bikini, which they were told was of great importance to humankind, two nuclear weapons were detonated in 1946. About ten years later, additional tests with thermonuclear weapons in the late 1950s were also conducted. The first thermonuclear explosion was much more powerful than expected, and created a number of issues, but did demonstrate the dangers of such devices.
The United States and its allies were engaged in a Cold War nuclear arms race with the Soviet Union to build more advanced bombs from 1947 until 1991. The first series of tests over Bikini Atoll in July 1946 was codenamed Operation Crossroads. The first bomb, named Able, was dropped from an aircraft and detonated above the target fleet. The second, Baker, was suspended under a barge. It produced a large Wilson cloud and contaminated all of the target ships. Chemist Glenn T. Seaborg, the longest-serving chairman of the Atomic Energy Commission, called the second test "the world's first nuclear disaster." A third test, Charlie, was cancelled due to concerns over the lingering radiation from Baker's detonation.
The second series of tests in 1954 was codenamed Operation Castle. The first detonation was Castle Bravo, which tested a new design utilizing a dry-fuel thermonuclear bomb. It was detonated at dawn on March 1, 1954. Scientists miscalculated: the 15 Mt of TNT nuclear explosion far exceeded the expected yield of 4–8 Mt of TNT. This was about 1,000 times more powerful than either of the atomic bombs dropped on Hiroshima and Nagasaki during World War II. The scientists and military authorities were shocked by the size of the explosion, and many of the instruments that they had put in place to evaluate the effectiveness of the weapon were destroyed.
Authorities had promised the Bikini Atoll's residents that they would be able to return home after the nuclear tests. A majority of the island's family heads agreed to leave the island, and most of the residents were moved to the Rongerik Atoll and later to Kili Island. Both locations proved unsuitable to sustaining life, and the United States provides residents with on-going aid. Despite the promises made by authorities, these and further nuclear tests rendered Bikini unfit for habitation, contaminating the soil and water, making subsistence farming and fishing too dangerous. The United States has paid more than $300 million into various trust funds to compensate the islanders and their descendants. A 2016 investigation found radiation levels on Bikini Atoll as high as 639 mrem/yr, well above the established safety standard for habitation. However, Stanford University scientists reported "an abundance of marine life apparently thriving in the crater of Bikini Atoll" in 2017.
Preparation
The major preparation was to relocate the residents after discussion with them. At the time it was thought it would be a temporary relocation. As time showed, the nuclear weapons contaminated the area in a way that made them dangerous to live in for an extended period.Residents relocated
In February 1946, the United States government forced the 167 Micronesian inhabitants of the atoll to temporarily relocate so that testing could begin on atomic bombs. King Juda agreed to the request, announcing that "we will go believing that everything is in the hands of God." Nine of the eleven family heads chose Rongerik as their new home. Navy Seabees helped them to disassemble their church and community house and prepare to relocate to their new home. On March 7, 1946, the residents gathered their belongings and building supplies. They were transported eastward on Navy landing craft 1108 and LST 861 to the uninhabited Rongerik Atoll, which was one-sixth the size of Bikini Atoll. No one lived on Rongerik because it had an inadequate water and food supply, and also due to traditional beliefs that the island was haunted by the Demon Girls of Ujae. The Navy left them with a few weeks of food and water which soon proved inadequate.Military services
The United States assembled a support fleet of 242 ships that provided quarters, experimental stations, and workshops for more than 42,000 personnel. The islands were primarily used as recreation and instrumentation sites. Seabees built bunkers, floating dry docks, steel towers for cameras and recording instruments, and other facilities on the island to support the servicemen. These included the "Up and Atom Officer's Club" and the "Cross Spikes Club", a bar and hang-out created by servicemen on Bikini Island between June and September 1946. The "club" was little more than a small open-air building which served alcohol to servicemen and provided outdoor entertainment, including a ping pong table. The "Cross Spikes Club" was the only entertainment that the enlisted servicemen had access to during their June to September stay at Bikini.Ship graveyard
The Navy designated Bikini Atoll lagoon as a ship graveyard, then brought in 95 ships, including carriers, battleships, cruisers, destroyers, submarines, attack transports, and landing ships. The proxy fleet would have comprised the sixth largest naval fleet in the world if the ships had been active. All carried varying amounts of fuel, and some carried live ordnance.Weapons tests
Operation Crossroads
Crossroads consisted of two detonations, each with a yield of 23 kt of TNT. Able was detonated over Bikini on July 1, 1946 and exploded at an altitude of, but was dropped by aircraft about off target. It sank only five of the ships in the lagoon. Baker was detonated underwater at a depth of on July 25, sinking eight ships. The second underwater blast created a large condensation cloud and contaminated the ships with more radioactive water than was expected. Many of the surviving ships were too contaminated to be used again for testing and were sunk. The air-borne nuclear detonation raised the surface seawater temperature by, created blast waves with speeds of up to, and shock and surface waves up to high. Blast columns reached the floor of the lagoon, which is approximately deep.Charlie was planned for 1947 but was canceled primarily because of the Navy's inability to decontaminate the target ships after the Baker test. Charlie was rescheduled as Operation Wigwam, a deep water shot conducted in 1955 off the California coast.
Castle Bravo test
The next series of tests over Bikini Atoll was codenamed Operation Castle. The first test of that series was Castle Bravo, a new design utilizing a dry fuel thermonuclear bomb. It was detonated at dawn on March 1, 1954.The explosion yielded 15 Mt of TNT, far exceeding the expected yield of 4 to 8 Mt of TNT, and was about 1,000 times more powerful than each of the atomic bombs dropped on Hiroshima and Nagasaki during World War II. The device was the most powerful nuclear weapon ever detonated by the United States. Bravo had just under one third the energy of the Soviet Tsar Bomba, the largest nuclear device ever tested. However, while the Soviets intended to create such a large weapon, Castle Bravo's yield was much higher than anticipated. The scientists and military authorities were shocked by the size of the explosion, and it destroyed many of the instruments put in place to evaluate the effectiveness of the test.
The test was considered "the worst" nuclear test, with one designer saying "We had no idea what we were doing". The results of this test led to the limited test ban treaty of 1963.
Castle Bravo contamination
The unexpectedly large yield led to the most significant radiological contamination caused by the United States. A few minutes after the detonation, blast debris began to fall on Eneu/Enyu Island on Bikini Atoll where the crew who fired the device were located. Their Geiger counters detected the unexpected fallout, and they were forced to take shelter indoors for a number of hours before it was safe for an airlift rescue operation.The fallout continued to spread across the inhabited islands of the Rongelap, Rongerik, and Utrik Atolls. The inhabitants of Rongelap and Rongerik Atolls were evacuated by servicemen two days after the detonation, but the residents of the more distant Utrik Atoll were not evacuated for three days. Many of them soon began to show symptoms of acute radiation syndrome. They returned to the islands three years later but were forced to relocate again when the islands were found to be unsafe.
The fallout gradually dispersed around the globe, depositing traces of radioactive material in Australia, India, Japan, and parts of the United States of America and Europe. It had been organized as a secret test, but Castle Bravo quickly became an international incident prompting calls for a ban on atmospheric testing of thermonuclear weapons.
Local populations affected
The Rongelap Atoll was coated with up to of snow-like irradiated calcium debris and ash over the entire island. Virtually all the inhabitants experienced severe radiation sickness, including itchiness, sore skin, vomiting, diarrhea, and fatigue. Their symptoms also included burning eyes and swelling of the neck, arms, and legs. They were forced to abandon the islands three days after the tests, leaving behind all their belongings. The U.S. government relocated them to Kwajalein for medical treatment.Six days after the Castle Bravo test, the government set up a secret project to study the medical effects of the weapon on the residents of the Marshall Islands. The United States was subsequently accused of using the inhabitants as medical research subjects without obtaining their consent to study the effects of nuclear exposure. Until that time, the Atomic Energy Commission had given little thought to the potential impact of widespread fallout contamination and health and ecological impacts beyond the formally designated boundary of the test site.