Castle Bravo mushroom cloud
|Test series||Operation Castle|
|Test site||Bikini Atoll|
|Date||March 1, 1954|
|Yield||15 Mt (approx. 63 PJ)|
Castle Bravo was the code name given to the first United States test of a dry fuel hydrogen bomb, 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 Tsar Bomba, the most powerful device ever detonated), with a yield of 15 megatons of TNT. That yield, far exceeding the expected yield of 4 to 8 megatons (6 Mt predicted), combined with other factors, led to the most significant accidental radioactive contamination ever caused by the United States.
Fallout from the detonation—intended to be a secret test—fell on residents of Rongelap and Utirik atolls and spread around the world. The islanders were not evacuated until three days later and suffered radiation sickness. They were returned to the islands three years later but were removed again when their island was found to be unsafe. The crew of the Japanese fishing vessel Daigo Fukuryū Maru ("Lucky Dragon No. 5") was also contaminated by fallout, killing one crew member. The blast created an international reaction about atmospheric thermonuclear testing.
The device was a very large cylinder weighing 23,500 pounds (10.7 t) and measuring 179.5 inches (4.56 m) in length and 53.9 inches (1.37 m) in diameter. It was mounted in a "shot cab" on an artificial island built on a reef off Namu Island, in the Bikini Atoll. A sizable array of diagnostic instruments was trained on it, including high-speed cameras trained through an arc of mirror towers around the shot cab.
Coordinates for Bravo Crater are. The coordinates of the remains of the Castle Bravo causeway are .
The Shrimp device in its shot cab.
|Type||Teller-Ulam design Thermonuclear weapon|
|Designer||Ben Diven-project engineer|
|Designed||24 February 1953 (GMT)|
|Manufacturer||Los Alamos National Laboratory|
|Unit cost||$1,844,000 (1954 USD)|
|Produced||October 1953 (GMT)|
|Weight||10,659 kilograms (23,499 lb)|
|Length||455.93 centimeters (179.50 in)|
|Diameter||136.90 centimeters (53.90 in)|
|Filling weight||218,940 grams (7,723 oz)|
|Blast yield||15 megatons of TNT (63 PJ)|
The device to be detonated for the test was named Shrimp and the same basic configuration (the radiation implosion) as the experimental Ivy Mike wet-device, except with a different type of fusion fuel. Shrimp used lithium deuteride, or LiD for short, which is solid at room temperature; Ivy Mike used cryogenic liquid deuterium, or LD for short, which required elaborate cooling equipment. Castle Bravo was the first test by the United States of a practical deliverable fusion bomb (hydrogen bomb). The successful test rendered the cryogenic design used by Ivy Mike and its derivative, the Mark 16 nuclear bomb, which was slated to be tested as the initial Castle Yankee, obsolete. It also used a 7075 Aluminium ballistic case that drastically reduced the bomb's weight, a departure from the heavy steel casing employed by contemporary weapon-projects, in an effort to increase radiation confinement.
Describing the weapon's design from outside inwards, one observes attached to the cylindrical case a U-238 liner, the radiation case. The Shrimp design used an approximately 2.5 cm thick U-238 radiation case. Its internal surface (that is to say the side that "looked" the nuclear components) was lined with ~240 μm thick copper liner out of standardized 0.08 μm thick copper foil. Copper is an excellent reflector. Natural uranium, or Depletalloy, nails lined to the top of their head with copper reverted the radiation case to the ballistic case. The nails were bolted in spiral-arrays and in a double-shear configuration to better distribute the shear loads. This method (of reverting the radiation case to the ballistic case) was first used successfully to the Ivy Mike device. The otherwise cylindrical radiation case had a parabolic end which housed a fission atomic bomb the primary, that was employed to create the conditions needed to start the fusion reaction, and its other end was a typical straight-line plane.
The space between the tamper and the case formed a radiation channel to conduct X-rays from the primary to the secondary; the space was filled with polystyrene plastic foam impregnated with a low molecular weight hydrocarbon (possibly methane or pentane gas) which turned to plasma from the X-rays, which in turn reduced the sputtering effect that choked the radiation from compressed the secondary. Sputtering is a problem, also shared by the Magnetically Confined Fusion reactors (see Tokamak), that has to do with the ablated parcels, the blown-off U-238 (or Pb-Bi alloy, depending on radiation hohlraum design), which fly inside the radiation channel and absorb radiation or reflect it, contributing negatively on the radiation mirroring. The re-emitted X-rays from the radiation case must be deposited to the outer walls of the secondary tamper and ablate it externally, increasing the density and temperature of the fusion fuel to the level needed to sustain a thermonuclear reaction. (See nuclear weapon design.).
Since the ablative process takes place to both walls of the radiation channel, we deduce that the U-238 tamper (the metal jacket encasing the secondary) had a thickness of 2.5 cm, so that an equal pressure to would be applied both walls of the hohlraum. This is based to Third Law, where "each action has an equal and opposite reaction". With that in mind, if one of the walls was thicker, the ablation pressure to that wall would be different and it would cause unstable compression. Furthermore, with the same thickness the confinement time could be more easily estimated. The rocket effect on the surface of the walls created by the ablation of several superficial U-238 layers would force an equal mass of U-238 that rested with the reminder of the tamper to speed-up inwards, thus imploding (or exploding in the case of the radiation case). The ballistic case would confine the exploding radiation case for as long as it was necessary. The fact that the hohlraum material was U-238 is based to the presence of the final fission reaction. It was shown by the U-237 found by the Japanese in the shot debris (see Chuck Hansen Swords of Armageddon Book: IV-282). One must note, as stated by Chuck Hansen in Swords of Armageddon, Book: IV-16, that the series of first generation thermonuclear weapons (MK-14, 16, 17, 21, 22 and 24) all used uranium tampers enriched to 37.5% in U-235. Exception to this was the MK-15 Zombie that used a 93.5% enriched fission jacket.
Moving on to the secondary assembly itself. It was situated at the one end of the device, specifically the "rectangular" end, where its end screwed to the radiation case. The end of the device as seen in the declassified films, show that a small cone protracted from the ballistic case. This was done so that the projection would nest the "screw" and would have better structural strength to support the secondary which concentrated most of the device's mass. Any other supporting structure would cause radiation transfer blockade and was discarded. The other end of the radiation case was shaped like a parabola to focus the radiation exerted by the fission device. The secondary was a cylindrical geometry, more like an elongated truncated cone. From its foremost part to its aft section it had a steep tapering. Tapering was used for two reasons; firstly the radiation drops sharply by distance, as a function divided by the square of the distance value. This rendered the use of higher mass of the then scarce fusion fuel in the rear end of the secondary inefficient, and the whole device wasteful. Secondly, by tapering, a form of quasi parabola was created in the aft section of the radiation channel without having to machine the radiation case to a parabola at its both ends, something that enhanced the radiation focusing and benefited the design with a streamlined production line, as it was cheaper, faster and easier to manufacture the radiation case with only one parabolic end. The tapering in this design was much steeper than its cousins, the Runt and the Alarm Clock devices.
This secondary device was what contained the lithium deuteride fusion fuel, and was the "actual" Shrimp component of the assembly. It run from the end of the radiation case to almost half of the bomb's length. The fact that the whole device was called with the same name was a matter of simplification. Running down to the center of the secondary, was a ~2 cm thick hollow cylindrical rod of plutonium, with an about 0.5 cm aperture at its center, the sparkplug, which imploded together with the secondary's compression and was timed to detonate by the stray of the first generations of neutrons that arrived from the primary. It's purpose was to compress the fusion material around it from its inside, equally applying pressure with the tamper. It weighted about 18 kg and its detonation would yield 61 kt, the same with the primary's yield. It would be then completely burned by the fusion neutrons contributing about 330 kt to the total yield. The stray of neutrons entered the assembly by a small hole (filed with boron-10 doped paraffin wax to time the neutrons' income) that was pierced through the ~10 cm thick U-238 radiation shield. It was positioned in front of the secondary and faced the primary. It was shaped as a truncated cone. To visualize the concept, its small diameter was facing on the primary's side and the large diameter fixed at the secondary. Surrounding the fusion fuel-sparkplug assembly was a uranium tamper with an in-between standoff air-gap about 2.5 cm wide. That was to increase the tamper's momentum, a levitation technique used as early as Operation Sandstone and famously quoted by Ted Taylor as hammer-on-the-nail-impact.
The Shrimp was at least in theory identical in geometry to the Runt and Runt II devices later detonated in Castle Romeo and Castle Yankee respectively. On paper it was a scaled-downed version of these devices. It used partially enriched lithium as its fusion fuel. Natural lithium is a mixture of lithium-6 and lithium-7 isotopes (with 7.5% of the former). The enriched lithium used in Bravo was nominally 40% lithium-6 (the fuel slugs varied in enrichment from 37%-40% in Li-6). All these were due to shortages in enriched lithium at that time, as the first Alloy Development Plants (ADP) started production by the fall of 1953. The volume of LiD fuel used was approximate the same to the volume of the LD filling used in the Sausage device, or about 410,000 cc, corresponding to 218.94 kg of lithium deuteride as LiD has a density of 0.534 g/cm3. The mixture costed about $4.54/g.
The thermonuclear burn would produce high energy neutrons (with a temperature of 14 MeV) and the reaction's neutronicity was estimated at ~0.885 (for a Lawson criterion of ~1.5). These figures do not count the Li-7 isotope (where the Li-7D has a neutronicity of ~0.835) and along with the cross-sections were given as group averages from about 2.40 to approximately 2.55 MeV and from 14.0 to 14.1 MeV (the small power group is not statistically present). All of the high-energy 14 MeV neutrons would cause fission in the U-238 fusion tamper wrapped around the secondary and the sparkplug's plutonium rod. The ratio of deuterium atoms burned to 14 MeV neutrons spawned by the burning was expected to vary from 5:1 to 3:1.
Boron was also used at many locations in this dry system; It has a high cross-section for the absorption of slow neutrons which fission U-235 and Pu-239, but a low cross-section for the absorption of fast neutrons which fission U-238. Because of this characteristic, boron-10, when loaded (deposited) into the surface of the secondary stage, it would prevent predetonation of the sparkplug by stray neutrons from the primary without interfering with the subsequent fissioning of the U-238 fusion tamper around the secondary. Boron also played a role in increasing the compressive plasma pressure around the secondary that blocked the sputtering effect, leading to higher thermonuclear efficiency. By doping with boron-10 the structural foam holding the secondary in place within the casing, the secondary was to be compressed more highly, at a cost of some radiated neutrons. An example of the boron-10 usefulness can be seen by the fact that the fizzled Castle Koon Morgenstern device didn't utilise it in its design. As a result, the intense neutron flux from its RACER IV primary pre-detonated the spherical fission sparkplug which in turn "cooked" the fusion fuel leading to an overall poor compression. A common misconception here is that the plasma pressure does not assist the implosion. The plastic's low molecular weight is unable to implode in any way the secondary's mass. Its pressure confines in the vicinity of the ablation process the boiled-off sections of the tamper and the radiation case from entering the radiation channel that has to be open for the radiation transit.
The primary device was a LASL-furnished COBRA tritium-boosted atomic bomb, a very compact, specifically designed MK-7 device as the thermonuclear device's primary. This boosted fission device was urgently tested in the Upshot Knothole Climax event and yielded 61 kt (out of 50-70 kt expected yield range), so that the planned operation Domino could be cancelled to alleviate the forthcoming presidential elections. The implosion system weighed 900 lb and used the more powerful Cyclotol 75/25 in preference to the Composition B used in most bombs at that time, with the assembled module weighting in total 1840 lbs and measuring 30.5 in across.
When Bravo was detonated, it formed a fireball almost four and a half miles (roughly 7 km) across within a second. This fireball was visible on Kwajalein atoll over 250 miles (400 km) away. The explosion left a crater 6,500 feet (2,000 m) in diameter and 250 feet (76 m) in depth. The mushroom cloud reached a height of 47,000 feet (14,000 m) and a diameter of 7 miles (11 km) in about a minute; it then reached a height of 130,000 feet (40 km) and 62 miles (100 km) in diameter in less than 10 minutes and was expanding at more than 100 meters per second (360 km/h; 220 mph). As a result of the blast, the cloud contaminated more than seven thousand square miles of the surrounding Pacific Ocean including some of the surrounding small islands like Rongerik, Rongelap and Utirik.
In terms of TNT tonnage equivalence, Castle Bravo was about 1,000 times more powerful than each of the atomic bombs which were dropped on Hiroshima and Nagasaki during World War II. The largest nuclear explosion ever produced was a test conducted by the Soviet Union seven and a half years later, the 50 Mt Tsar Bomba. Castle Bravo is the fifth largest nuclear explosion in history, exceeded by the Soviet tests of Tsar Bomba at 50.6 Mt, Test 219 (24.2 Mt), and two other ~20 Mt Soviet tests in 1962 at Novaya Zemlya.
Cause of high yield
The yield of 15 megatons was three times the yield of 5 Mt predicted by its designers. The cause of the higher yield was a theoretical error made by designers of the device at Los Alamos National Laboratory. They considered only the lithium-6 isotope in the lithium deuteride secondary to be reactive; the lithium-7 isotope, accounting for 60% of the lithium content, was assumed to be inert. It was expected that lithium-6 isotope would absorb a neutron from the fissioning plutonium and emit an alpha particle and tritium in the process, of which the latter would then fuse with the deuterium and increase the yield in a predicted manner. Lithium-6 indeed reacted in this manner.
It was assumed that the lithium-7 would absorb one neutron, producing lithium-8 which decays (via beryllium-8) to a pair of alpha particles on a timescale of seconds—vastly longer than the timescale of nuclear detonation. However, when lithium-7 is bombarded with energetic neutrons, rather than simply absorbing a neutron, it captures the neutron and decays almost instantly into an alpha particle, a tritium nucleus, and another neutron. As a result, much more tritium was produced than expected, the extra tritium fusing with deuterium and producing an extra neutron. The extra neutron produced by fusion and the extra neutron released directly by lithium-7 decay produced a much larger neutron flux. The result was greatly increased fissioning of the uranium tamper and increased yield.
This resultant extra fuel (both lithium-6 and lithium-7) contributed greatly to the fusion reactions and neutron production and in this manner greatly increased the device's explosive output. The test used lithium with a high percentage of lithium-7 only because lithium-6 was then scarce and expensive; the later Castle Union test used almost pure lithium-6. Had sufficient lithium-6 been available, the usability of the common lithium-7 might not have been discovered.
The fission reactions of the natural uranium tamper were quite dirty, producing a large amount of fallout. That, combined with the much-larger-than-expected yield and a major wind shift, produced some very serious consequences. In the de-classified film Operation Castle, task force commander Major General Percy Clarkson points to a diagram indicating that the wind shift was still in the range of "acceptable fallout", although just barely.
The decision to carry out the Bravo test under the prevailing winds was made by Dr. Alvin C. Graves, the Scientific Director of Operation Castle. Graves had total authority over detonating the weapon, above that of the military Commander of Operation Castle. Graves appears in the widely available film of the earlier 1952 test "Ivy Mike", which examines the last-minute fallout decisions. The narrator, Western actor Reed Hadley, is filmed aboard the control ship in that film, showing the final conference. Hadley points out that 20,000 people live in the potential area of the fallout. He asks the control panel scientist if the test can be aborted and is told "yes", but it would ruin all their preparations in setting up timed measuring instruments in the race against the Russians. In Mike the fallout correctly landed north of the inhabited area but, in the 1954 Bravo test, there was a lot of wind shear, and the wind that was blowing north the day before the test steadily veered towards the east. (In the 1946 Los Alamos accident Graves' personal friend, Louis Alexander Slotin, died from radiation exposure and Graves had himself received an exposure of 400 röntgens, or 3.5 grays (Gy).)
Radioactive fallout was spread eastward onto the inhabited Rongelap and Rongerik atolls, which were evacuated 48 hours after the detonation. Subsequently many Marshall Islands natives suffered from birth defects and received compensation from the U.S. federal government. A medical study, named Project 4.1, studied the effects of the fallout on the islanders.
Although the atmospheric fallout plume drifted eastward, once fallout landed in the water it was carried in several directions by ocean currents, including northwest and southwest.
A Japanese fishing boat, Daigo Fukuryū Maru (Lucky Dragon No.5), came in direct contact with the fallout, which caused many of the crew to grow ill; one died of a secondary infection. This resulted in an international incident and reignited Japanese concerns about radiation, especially as Japanese citizens were once more adversely affected by U.S. nuclear weapons. The official U.S. position had been that the growth in the strength of atomic bombs was not accompanied by an equivalent growth in radioactivity released. Japanese scientists who had collected data from the fishing vessel disagreed with this. Sir Joseph Rotblat, working at St Bartholomew's Hospital, London, demonstrated that the contamination caused by the fallout from the test was far greater than that stated officially. Rotblat was able to deduce that the bomb had three stages and showed that the fission phase at the end of the explosion increased the amount of radioactivity a thousandfold. Rotblat's paper was taken up by the media, and the outcry in Japan reached such a level that diplomatic relations became strained and the incident was even dubbed by some as "a second Hiroshima". Nevertheless, the Japanese and U.S. governments quickly reached a political settlement, with the transfer to Japan of US $15,300,000 as compensation, with the surviving victims receiving about ¥ 2 million each ($5,550 in 1954, or about $48,900 in 2015)[unreliable source?] It was also agreed that the victims would not be given Hibakusha status.
Unanticipated fallout and the radiation emitted by it also affected many of the vessels and personnel involved in the test, in some cases forcing them into bunkers for several hours. In contrast to the crew of the Lucky Dragon No. 5, who did not appreciate the hazard and therefore did not take shelter in the hold of their ship, or refrain from licking the fallout dust, the firing crew that triggered the explosion were able to safely shelter in their firing station when they noticed the wind was carrying the fallout in the unanticipated direction towards the island of Enyu on the Bikini Atoll where they were located, with the fire crew sheltering in place or "button[ing] up" until several hours had passed and the radiation levels outside had decayed to values safe enough to travel in.
Sixteen crew members of the aircraft carrier USS Bairoko received beta burns and there was an increased cancer rate among its crew. Radioactive contamination also affected many of the testing facilities built on other islands of the Bikini atoll system.
The fallout spread traces of radioactive material as far as Australia, India and Japan, and even the United States and parts of Europe. Though organized as a secret test, Castle Bravo quickly became an international incident, prompting calls for a ban on the atmospheric testing of thermonuclear devices.
A world-wide network of gummed film stations was established to monitor fallout following Operation Castle. Although meteorological data were poor, a general connection of tropospheric flow patterns with observed fallout was evident. There was a tendency for fallout/debris to remain in tropical latitudes, with incursions into the temperate regions associated with meteorological disturbances of the predominantly zonal flow. Outside of the tropics, the Southwestern United States received the greatest total fallout, about five times that received in Japan.
Stratospheric fallout particles of Strontium-90 from the test were later captured with Balloon-borne air filters used to sample the air at stratospheric altitudes, the research (Project Ashcan) was conducted to better understand the stratosphere, fallout times and arrive at more accurate meteorological models after hindcasting, the research was published in the Journal of Geophysical Research in 1959.
In addition to the radiological accident, the unexpectedly high yield of the device severely damaged many of the permanent buildings on the control site island on the far side of the atoll. Little of the desired diagnostic data on the shot was collected; many instruments designed to transmit their data back before being destroyed by the blast were instead vaporized instantly, while most of the instruments that were expected to be recovered for data retrieval were destroyed by the blast.
The fallout also affected islanders who had previously inhabited the atoll, and who returned there some time after the tests. This was found to be due to the presence of radioactive caesium in locally grown coconut milk. Plants and trees absorb potassium as part of the normal biological process, but will also readily absorb caesium if present, being of the same group on the periodic table, and therefore very similar chemically. Islanders consuming contaminated coconut milk were found to have abnormally high concentrations of caesium in their bodies and then had to be evacuated from the atoll a second time.
The Soviet Union had previously used lithium deuteride in its Sloika design (known as the "Joe-4" in the U.S.), in 1953. It was not a true hydrogen bomb; fusion provided only 15–20 percent of its yield, most coming from boosted fission reactions. Its yield was 400 kilotons, and it could not be infinitely scaled, as with a true thermonuclear device.
The Teller-Ulam-based "Ivy Mike" device had a much greater yield of 10.4 Mt, but most of this also came from fission: 77 percent of the total came from fast fission of its natural uranium tamper.
Castle Bravo had the greatest yield of any U.S. nuclear test, 15 Mt, though again, a substantial fraction came from fission. In the Teller-Ulam design, the fission and fusion stages were kept physically separate in a reflective cavity. The radiation from the exploding fission primary brought the fuel in the fusion secondary to critical density and pressure, setting off thermonuclear (fusion) chain-reactions, which in turn set off a tertiary fissioning of the bomb's outer casing. Consequently, this type of bomb is also known as a "fission-fusion-fission" device. The Soviet researchers, led by Andrei Sakharov, developed and tested their first Teller-Ulam device in 1955.
The publication of the Bravo fallout analysis was a militarily sensitive issue, with Joseph Rotblat possibly deducing the staging nature of the Castle Bravo device by studying the ratio and presence of tell-tale isotopes, namely uranium-237, present in the fallout. With this information having a history of being regarded as potentially revealing the means by which megaton yield nuclear devices achieve their yield. In the History of the Teller–Ulam design, Soviet scientist Sakharov hit upon what the Soviet Union regarded as "Sakharov's third idea" during the month after the Castle Bravo test, the final piece of the puzzle being the idea that the compression of the secondary can be accomplished by the primary's x-rays before fusion began.
The Shrimp device design later evolved into the Mark 21 nuclear bomb, of which 275 units were produced, weighing 15,000 pounds (6,800 kg) and measuring 12.5 feet (3.8 m) long and 56 inches (1.4 m) in diameter. This 4-megaton bomb was produced until July 1956. In 1957, it was converted into the Mark 36 nuclear bomb and entered into production again.
As a result of the extensive fallout, Nevil Shute wrote the novel On the Beach which was released in 1957. The novel is about a war that released so much radioactive fallout that all the life in the Northern Hemisphere disappeared, while the Southern Hemisphere awaited a similar fate. However the American government voiced a criticism of this general premise, that there was a threat of extinction from nuclear war because they did not, nor have they ever, had enough nuclear weapons to cause human extinction. Similarly the premise that all of humanity would die following a nuclear war and only the "cockroaches would survive" is critically dealt with in the book Would the Insects Inherit the Earth and Other Subjects of Concern to Those Who Worry About Nuclear War. A combination of the Castle Bravo detonation, alongside the subsequent poisoning of the Lucky Dragon 5, and the resultant flashbacks to the bombings of Hiroshima and Nagasaki all culminated in the creation of what is perhaps Japan's most widely recognized media icon, Godzilla.
During the opening scene of the 2014 American Godzilla reboot and in the prequel comic Godzilla: Awakening, the Castle Bravo nuclear test was an attempt to kill Godzilla and a prehistoric parasite called "Shinomura." Godzilla, however, survived the "test," despite humanity believing otherwise, while the Shinomura was incinerated.
- http://nuclearweaponarchive.org/Usa/Tests/Castle.html retrieved Oct. 8, 2013
- "The Ghost Fleet of Bikini Atoll". August 9, 2010. A&E Television Networks. Military History Channel. Retrieved May 4, 2012. Missing or empty
- John Bellamy Foster (2009). The Ecological Revolution: Making Peace with the Planet, Monthly Review Press, New York, p. 73.
- Danneskiold, Jim (14 April 2005). "Operation Castle tests focus of April 20 panel discussion". Archived from the original on 7 May 2009.
- Rhodes Chapter 23
- "Nuclear Weapon Archive". Retrieved 2008-03-01.
- Titus, A. Costandina. Bombs in the backyard atomic testing and American politics. Reno: University of Nevada P, 2001. Google Books. .
- Rhodes p. 541
- "Operation Castle". nuclearweaponarchive.org. Retrieved 4 August 2015.
- Kunkel, Thomas; Ristvet, Brian (January 25, 2013). "DTRIAC SR-12-001 CASTLE BRAVO:FIFTY YEARS OF LEGEND AND LORE A Guide to Off - Site Radiation Exposures" (PDF). Albuquerque, NM: Defense Threat Reduction Agency. Retrieved November 23, 2015.
- "Les cobayes du Dr Folamour" (in French).
- "Nuclear Issues". Retrieved 2006-03-26.
- S. Sevitt, "The Bombs," The Lancet, July 23, 1955, pp. 199-201.
- Rhodes, p.542
- Beverly Deepe Keever (February 25, 2004). "Shot in the Dark". Honolulu Weekly. Archived from the original on 12 July 2011. Retrieved 2008-11-30.
The Japanese government and people dubbed it "a second Hiroshima" and it nearly led to severing diplomatic relations
- "50 Facts About U.S. Nuclear Weapons". brookings.edu. Archived from the original on 19 July 2011. Retrieved 4 August 2015.
- Keiji Hirano (February 29, 2004). "Bikini Atoll H-bomb damaged fisheries, created prejudice". Chugoku. Retrieved 2008-11-30.
- Dr. John C. Clark as told to Robert Cahn (July 1957). "Trapped by Radioactive Fallout, Saturday Evening Post" (PDF). accessed Feb 20, 2013
- Hoffman, Michael, "Forgotten atrocity of the atomic age", Japan Times, 28 August 2011, p. 11.
- http://www.dgely.com/Bikini/Nuclear%20Testing/Operation%20Castle/Operation%20Castle%20Bravo%20Blast.htm The Bravo device was detonated from a firing station located on Enyu Island. Given the proximity of the firing station to ground zero and the surprise yield of the blast, the crew within the bunker were shaken, but well protected from the radiation. Outside the bunker after 1 hour, radiation levels were 250 Rems/hour. Inside: .035Rems/hour...As shown above this vessel was exposed to [around] 1,000 rads, well above the threshold where vomiting and severe physical effects are felt.
- DeGroot 2004, pp. 196-198
- List, R.J. "WORLD-WIDE FALLOUT FROM OPERATION CASTLE - SciTech Connect". osti.gov. Retrieved 4 August 2015.
- "Analysis of stratospheric strontium90 measurements". wiley.com. Retrieved 4 August 2015.
- http://www.osti.gov/scitech/biblio/4225048 ANALYSIS OF STRATOSPHERIC STRONTIUM-90 MEASUREMENTS Weather Bureau, Washington, D.C. 1959-03-01
- "WebElements Periodic Table of the Elements Caesium biological information". Retrieved 12 November 2013.
- Nash, Gary B., Julie Roy Jeffrey, John R. Howe, Peter J. Frederick, Allen F. Davis, Allan M. Winkler, Charlene Mires, and Carla Gardina Pestana. The American People, Concise Edition Creating a Nation and a Society, Combined Volume (6th Edition). New York: Longman, 2007.
- Joseph Rotblat: visionary for peace. By Reiner Braun, Wiley-VCH, 2007 ISBN 3-527-40690-5
- https://www.princeton.edu/sgs/publications/sgs/pdf/2_4DeGeer.pdf The Radioactive Signature of the Hydrogen Bomb.
- "Bartlett - Nuclear Warfare in the Movies". ucla.edu. Retrieved 4 August 2015.
- Mushroom Clouds and Mushroom Men - The Fantastic Cinema of Ishiro Honda (by Peter H. Brothers, published by AuthorHouse in 2009)
- Gerard DeGroot, The Bomb: A Life (London: Jonathan Cape, 2004) ISBN 0-224-06232-8
- Chuck Hansen, U. S. Nuclear Weapons: The Secret History (Arlington: AeroFax, 1988)
- Rhodes, Richard (1995). Dark Sun: The Making of the Hydrogen Bomb. New York: Simon and Schuster. ISBN 0-684-80400-X.
- Holly M. Barker, Bravo for the Marshallese: Regaining control in a Post-Nuclear, Post Colonial World (Belmont, CA: Wadsworth, 2004)
- Republic of the Marshall Islands Embassy website
- Cronkite E. P., Conard R. A., Bond V. P. (1997). "Historical events associated with fallout from Bravo Shot — Operation Castle and 25 Y of medical findings". Health Physics 73 (1): 176–186. doi:10.1097/00004032-199707000-00014. PMID 9199227.
|Wikimedia Commons has media related to Castle Bravo.|
- The short film Operation Castle Commanders Report (1954) is available for free download at the Internet Archive
- The short film Military Effects Studies Operation Castle (1954) is available for free download at the Internet Archive
- The short film Nuclear Test Film - Operation Castle (1954) is available for free download at the Internet Archive
- Operation Castle
- US tests hydrogen bomb in Bikini (BBC News)
- First-person article about conducting the test