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| Fig. 1: Arial view of Bikini Atoll, the most notable test site from the Pacific Proving Grounds. (Source: Wikimedia Commons) |
Immediately after the end of World War II the United States sought out a location where it could test and develop its newly proven and developed Nuclear Arsenal. The location decided upon would be a series of Atolls in the Marshall Islands in the South Pacific, most notably Bikini, seen in Fig. 1, and Enewetak Atoll. [1] The location was approved by the United Nations as the Strategic Trust Territory. In these Pacific islands, as many as 105 tests occurred, totaling around 210 megatons. Among these tests were the first Hydrogen or Thermonuclear weapons, much more powerful than the fission bombs from beforehand. Many unique tests were carried out, including flying B-17 drones over zero point at detonation to see the damage and testing weapons on a fleet of decommissioned warships. [2] Tests were conducted on land and in water, causing mass amounts of radioactive fallout spreading to the 2,000+ islands that the Marshall Islands consist of and destruction of entire islands and coral reefs at ground zero. Many unforeseen effects from the radiation on the islands have left residents with health problems and long lasting effects on their ecosystem.
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| Fig. 2: The fireball and subsequent mushroom cloud from the 15 megaton explosion of Castle Bravo. (Source: Wikimedia Commons) |
Castle Bravo, the first dry thermonuclear bomb and probably the most notable of all the tests, was subject to massive error and miscalculation by scientists. The device, originally planned to be in the range of 4 to 8 megatons was measured at 15 megatons. The basic idea of a Hydrogen bomb is to utilise fusion through fission instead of just fission. A conventional fission bomb is used as the trigger to compress the secondary part of the bomb, consisting of fusion fuel, 40% Lithium-6 deuteride and Lithium-7 deuteride, a dry fuel. When talking about a dry Hydrogen bomb we are talking about a solid and not a liquid or wet fuel. The use of dry fuel is favored due to the fact that Lithium-6 deuteride is much easier to weaponize than deuterium and tritium gases and liquids, which in turn allows for a dramatic cut in weight of the device, allowing many more delivery capabilities. The reason the yield of the explosion was so high was due to the use of the dry fuel and its unknown capabilities, leading to miscalculations by the designers from Los Alamos Laboratories. This error was due to the fact that the Lithium-7 deuteride was expected to be inert when accepting a neutron and becoming a decaying isotope, Lithium-8. This decay indeed occurred, but into an high energy alpha particle, a neutron and a tritium nucleus, which in turn lead to be apart of the drive. This caused fusion between the tritium and the deuteride and lead to increased yield that was not expected. [3] In Fig. 2 we can see the fireball of 4 miles in diameter within the first second of detonation and contaminating 7,000 miles of the Pacific Ocean. The fallout from the explosion was much larger than expected and affected many of the nearby islands and the villagers in them.
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| Fig. 3: Geographical variation of cumulative Cs-137, a product of the nuclear tests, from all Marshall Islands nuclear tests. [3] (Courtesy of the U.S. Department of Defense.) |
The US Government had relocated all residents of the Bikini and Enewetak atolls to shield them from direct effects of the nuclear fallout. However, fallout from the testing was vast and reached locations the government did not expect to be touched by the testing. Most effects that occurred came through the Castle Bravo test due to the fact that it was so much larger than expected, particularly in the northern atolls and on Rongelap atoll. Residents of Rongelap islands had experienced symptoms of itchiness, vomiting and fatigue, common to radiation sickness. As seen in Fig. 3, people living in these northern atolls have been measured to experience between 200 and 1,000 mGys, while the average US resident experiences 1 mGy. [4] Through calculating these numbers researchers have projected that there will be an estimated 170 radiation caused cancer for people in the Marshall Islands. Most of these cancers will be of thyroid cancer or some form of leukemia. These numbers vary depending on age, as children are much more susceptible to radiation in their thyroid than adults. Not only did the testing effect the people, but also the ecosystem in which they lived in. With the vast amount of testing that occurred in the water the coral reefs of the islands were virtually decimated and the habitat in which they sustained. However sixty three years later, marine life in Bikini Atoll flourishes with coral reefs growing and fish plentiful. While there are no exact numbers on the number of species present today, we know of 126 coral species that existed before the tests and 42 that have not grown back. [5] This demonstrates the biodiversity of the ecosystem and coral. While the coral has regrown, the islands remain unlivable to this day.
© Matthew Gutwald. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.
[1] H. E. W. Crawford et al., The Five Series Study: Mortality of Military Participants in U.S. Nuclear Weapons Tests (National Academy Press, 2000).
[2] "Nuclear Testing Program in the Marshall Islands," Committee on Energy and Natural Resources, U.S. Senate, S. Hrg. 109-178, 19 Jul 05.
[3] "Castle Bravo: Fifty Years of Legend and Lore," Defense Threat Reduction Agency, DTRAIAC SR-12-001, January 2013.
[4] S. L. Simon et al., "Radiation Doses and Cancer Risks in the Marshall Islands Associated with Exposure to Radioactive Fallout from Bikini and Enewetak Nuclear Weapons Tests: Summary," Health Phys. 99, 105 (2010).
[5] Z. T. Richards, "Bikini Atoll Coral Biodiversity Resilience Five Decades After Nuclear Testing," Marine Poll. Bull. 56, 503 (2008).
