Operation Castle
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[[Image:Castle Romeo.jpg|right|thumb|250px|Operation Castle was the highest-yield nuclear test series ever conducted by the United States.]]
'''Operation Castle''' was a [[United States]] series of high-energy (high-[[nuclear weapon yield|yield]]) [[nuclear test]]s by Joint Task Force SEVEN (JTF-7) at [[Bikini Atoll]] beginning in March 1954. It followed [[Operation Upshot-Knothole]] and preceded [[Operation Teapot]].
Conducted as a joint venture between the [[United States Atomic Energy Commission|Atomic Energy Commission]] (AEC) and the [[United States Department of Defense|Department of Defense]] (DoD), the ultimate objective of the operation was to test designs for an aircraft-deliverable [[thermonuclear]] weapon.
Operation Castle is (largely) considered{{who}} to be a success for the "dry fuel" design. One device failed to produce its predicted yield. Two other devices detonated with over twice their predicted yields. One test in particular, [[Castle Bravo]], resulted in extensive radiological contamination of nearby islands (including inhabitants and U.S. soldiers stationed there), as well as a nearby Japanese fishing boat, resulting in one direct fatality and continued health problems for many of those exposed. Public reaction to the tests and an awareness of the long-range effects of [[nuclear fallout]] has been attributed as being part of the motivation for the [[Partial Test Ban Treaty]] of 1963.
==Background==
[[Image:AEC_Authorization_for_Operation_Castle.png|right|thumb|225px|AEC Authorization for '''Operation Castle''']]
[[Bikini Atoll]] had previously hosted nuclear testing in 1946 as part of [[Operation Crossroads]] where the world’s fourth and fifth atomic weapons were detonated in Bikini Lagoon. Since then, US nuclear weapons testing had moved to [[Enewetak|Eniwetok Atoll]] to take advantage of generally larger islands and deeper water (and therefore more real estate to stage experiments and support equipment upon). Both Atolls were part of the US [[Pacific Proving Grounds]].
However, the extremely high yields of the Castle weapons caused concern within the AEC that potential damage to the limited infrastructure already established at Eniwetok would delay other operations. Additionally, the cratering from the Castle weapons was expected to be comparable to that of [[Ivy Mike]], a 10.4 [[megaton|Mt]] device tested at Eniwetok in 1951 leaving a crater approximately 1 mile (1.6 km) in diameter.<ref >''Operation Ivy'', pg 192</ref>
The Ivy Mike test had been the world’s first [[thermonuclear]] explosion that used [[hydrogen]] [[nuclear fusion|fusion]] as its primary power source. The Mike device used [[cryogenic]] hydrogen [[isotopes]] in a liquid state, commonly referred to as a "wet bomb." The complex [[Dewar flask|dewar]] mechanisms needed to store the liquid hydrogen made the device three stories tall and 82 tons in total weight—completely impractical to be delivered by contemporary weapon systems of the [[cold war]].<ref>''Dark Sun'', pg 495.</ref> With the success of Ivy Mike as a proof of concept, research began on using a solid state “dry fuel” to achieve a practical fusion weapon. The "dry fuel" concept used the [[Teller-Ulam]] design with [[lithium deuteride]] as the fusion fuel, greatly reducing the size, weight, and complexity. Operation Castle was chartered to test four dry fuel designs, two wet bombs, and one smaller device. Approval for Operation Castle was communicated to JTF-7 by Major General [[Kenneth D. Nichols]], General Manager of the AEC, on [[21 January]], [[1954]].
==Experiments==
Operation Castle was organized into 7 experiments, all but one which were to take place at Bikini Atoll. Below is the original test schedule (as of February 1954). <ref>''Castle Series'', pg 247</ref>
{| class="wikitable" style="margin:auto;"
|+ Operation Castle Schedule
|-
! | Experiment
! | Device
! | Prototype
! | Fuel
! | Date
! | Predicted Yield
! | Manufacturer
! | Test Location
|-
! ''[[Castle Bravo|BRAVO]]''
| Shrimp
| TX-21
| 40% Li-6 D (dry)
| 1 March, 1954
| 6 [[megaton|Mt]]
| Los Alamos Scientific Laboratory
| Reef off Nam Is, Bikini
|-
! ''[[Castle Union|UNION]]''
| Alarm Clock
| EC-14
| 95% Li-6 D (dry)
| 11 March, 1954
| 3-4 [[megaton|Mt]]
| Los Alamos Scientific Laboratory
| Barge off Iroij, Bikini
|-
! ''[[Castle Yankee|YANKEE]]''
| Jughead
| TX/EC-16
| Cryo H-3 (wet)
| 22 March, 1954
| 8 [[megaton|Mt]]
| Los Alamos Scientific Laboratory
| Barge off Iroij, Bikini
|-
! ''[[Castle Echo|ECHO]]''
| Ramrod
| N/A
| Cryo H-3 (wet)
| 29 March, 1954
| 65-275 [[kiloton|Kt]]
| University of California Radiation Laboratory (Livermore)
| Eleleron, Enewetak
|-
! ''[[Castle Nectar|NECTAR]]''
| Zombie
| TX-15
|Boosted fission
| 5 April, 1954
| 1.8 [[megaton|Mt]]
| Los Alamos Scientific Laboratory
| Barge off Iroij, Bikini
|-
! ''[[Castle Romeo|ROMEO]]''
| Runt
| TX/EC-17A
| 7.5% Li-6 D (natural)
| 15 April, 1954
| 4 [[megaton|Mt]]
| Los Alamos Scientific Laboratory
| Barge off Iroij, Bikini
|-
! ''[[Castle Koon|KOON]]''
| Morgenstern
| N/A
| 7.6% Li-6 D (natural)
| 22 April, 1954
| 1 [[megaton|Mt]]
| University of California Radiation Laboratory (Livermore)
| Eneman, Bikini
|-
|}
Operation Castle was intended to be a proof of concept for lithium deuteride fuels in fusion weapons. The so-called "dry" lithium-6 fuels were a significant advancement in weapon design over the liquid hydrogen used in the Ivy Mike device. Bravo and Union used enriched lithium in the Teller-Ulam configuration where a typical [[nuclear fission|fission]] device is detonated in order to create the temperature and pressure needed for [[nuclear fusion|fusion]] in the lithium fuel capsule. Romeo and Koon used the same Teller-Ulam configuration, however, both were fueled by naturally occurring lithium deuteride (92% Li-7, 7.5% Li-6). The natural fuels, being vastly less time and resource intensive to obtain compared to enriched lithium, were important for US's ability expand the nuclear stockpile during the cold war [[nuclear arms race|arms race]].
Because the viability of dry fuels was not known, and there was significant risk of failure, development of liquid isotope weapons continued in parallel. Even though they were considered less practical due to logistical problems with transport, handling, and storage of a cryogenic device, the cold war arms race drove a technical demand for a viable weapon. Echo and Yankee were liquid fuel designs that were greatly reduced in size and weight over their Ivy Mike predecessor. The Jughead device was ultimately weaponized, despite the liquid fuel draw-backs, and saw limited fielding in the inventory until the dry fuel weapons were common.
Nectar was not a fusion weapon in the same sense as the rest of the Castle series. Even though it used a dry lithium fuel for [[fission boosting]], the principal reaction material in the second stage was uranium and plutonium. Similar to the Teller-Ulam configuration, a [[Nuclear fission|fission]] device was used to create high temperatures and pressures in order to compress a second [[fissionable]] mass that would have otherwise been too large to sustain an efficient reaction if it were triggered with conventional explosives. This experiment was intended to develop intermediate yield weapons for expanding the inventory (around 1-2 [[megatons|Mt]] vs. 4-8).
==Test execution==
The most notable event of Operation Castle was the Bravo test. The dry fuel for Bravo was 40% enriched Li-6, and 60% naturally occurring Li-7, the latter of which was expected to be essentially inert. Yet, [[J. Carson Mark]], head of the Los Alamos Theoretical Design Division, had speculated that Bravo could "go big", estimating that the device could produce an explosive yield as much as 20% more than had been originally calculated.<ref> O'Keefe, page 179</ref> Unexpectedly, the Li-7 was not inert, but extremely reactive under fusion conditions and produced a very high neutron and energy surplus through a previously unquantified neutron reaction. The result was that Bravo exceeded its expected [[nuclear weapon yield|yield]] by more than 250%, totaling 15 [[megatons|Mt]] or 1,000 times more powerful than the [[Little Boy]] weapon used on [[Hiroshima]]. Bravo is to this day the largest detonation ever conducted by the United States, and the seventh largest ever detonated in the world.
Because Bravo exceeded its designed yield by such a large margin, the JTF-7 was caught unprepared. Much of the permanent infrastructure on [[Bikini Atoll]] was heavily damaged. The intense thermal flash ignited a fire at a distance of 20 nautical miles on the island of Eneu (base island of Bikini Atoll).<ref>Castle Series, pg 209</ref> The ensuing [[nuclear fallout|fallout]] contaminated all of the Atoll to various levels, so much so that it could not be approached by JTF-7 for 24 hours after the test, and even then exposure times were limited.<ref>Hacker, pg 140</ref> As the fallout spread downwind, more atolls were contaminated with activated calcium ash. Although people on the atolls were evacuated soon after the test, in the end 239 Marshallese on the [[Utirik Atoll|Utirik]], [[Rongelap Atoll|Rongelap]], and [[Ailinginae Atoll]]s were subjected to significant levels of radiation, and 28 Americans stationed on the [[Rongerik]] Atoll were also exposed. Follow-up studies of the contaminated individuals began soon after the blast as [[Project 4.1]], and though the short-term effects of the radiation exposure for most of the Marshallese were mild and/or hard to correlate, the long-term effects were pronounced. Additionally, 23 Japanese fishermen aboard ''[[Daigo Fukuryū Maru|Lucky Dragon No. 5]]'' were also exposed to high levels of radiation. They suffered symptoms of [[radiation poisoning]], and one crew member died in September of 1954.
The heavy contamination and extensive damage from Bravo caused significant delays in the conduct the rest of the series. The post-Bravo schedule was revised on [[14 April]], [[1954]]<ref>''Castle Series'' pg 268</ref>.
{| class="wikitable" style="margin:auto;"
|+ Operation Castle Schedule (Post BRAVO)
|-
! | Experiment
! | Original Date
! | Revised Date
! | Original Yield
! | Revised Yield
|-
! ''[[Castle Union|UNION]]''
| 11 March, 1954
| 22 April, 1954
| 3-4 [[megaton|Mt]]
| 5-10 [[megaton|Mt]]
|-
! ''[[Castle Yankee|YANKEE]]''
| 22 March, 1954
| 27 April, 1954
| 8 [[megaton|Mt]]
| 9.5 [[megaton|Mt]]
|-
! ''[[Castle Nectar|NECTAR]]''
| 5 April, 1954
| 20 April
| 1.8 [[megaton|Mt]]
| 1-3 [[megaton|Mt]]
|-
! ''[[Castle Romeo|ROMEO]]''
| 15 April, 1954
| 27 March, 1954
| 4 [[megaton|Mt]]
| 8 [[megaton|Mt]]
|-
! ''[[Castle Koon|KOON]]''
| 22 April, 1954
| 7 April, 1954
| 1 [[megaton|Mt]]
| 1.5 [[megaton|Mt]]
|-
|}
The Romeo and Koon tests were complete by the time of this revision. The Echo test was canceled due to the liquid fuel design being considered obsolete following the success of the dry fuel in Bravo. The Jughead device was similarly considered obsolete and the Yankee test was conducted using a Runt II device (similar to the Union device) hastily completed at Los Alamos and flown to Bikini. With this revision, both of the "wet" fuel devices were removed from the test schedule.
As Operation Castle continued, the increased yields and fallout from the dry fuel experiments caused test locations to be re-evaluated. While the majority of the tests were planned for barges near the sand spit of Iroij, some were moved to the Bravo and Union craters. Additionally, Nectar was moved from Bikini Atoll to the Ivy Mike crater at [[Enewetak]] as a means of expediency since Bikini was still heavily contaminated from the previous tests.<ref>''Castle Series'' pg 248.</ref>
The final test in Operation Castle took place on [[14 May]], [[1954]].
{| class="wikitable" style="margin:auto;"
|+ Operation Castle (Actual)
|-
! | Experiment
! | Date
! | Yield
! | Location
|-
! ''[[Castle Bravo|BRAVO]]''
| 1 March, 1954
| 15[[megaton|Mt]]
| Reef off Nam Is, Bikini
|-
! ''[[Castle Romeo|ROMEO]]''
| 27 March, 1954
| 11 [[megaton|Mt]]
| Barge in BRAVO crater, Bikini
|-
! ''[[Castle Koon|KOON]]''
| 7 April, 1954
| 110 [[kiloton|kt]]
| Eneman, Bikini
|-
! ''[[Castle Union|UNION]]''
| 26 April, 1954
| 6.9 [[megaton|Mt]]
| Barge off Iroij, Bikini
|-
! ''[[Castle Yankee|YANKEE]]''
| 5 May, 1954
| 13.5 [[megaton|Mt]]
| Barge in UNION, Bikini
|-
! ''[[Castle Nectar|NECTAR]]''
| 14 May, 1954
| 1.69 [[megaton|Mt]]
| Barge Ivy-MIKE crater, Enewetak
|-
|}
==Results==
[[Image: Bikini_Atoll_Post_BRAVO.gif|right|thumb|300px|[[Bikini Atoll]] in the summer 1954 after the completion of Operation Castle.]]
Operation Castle was an unqualified success for the implementation of dry fuel devices. The Bravo design was quickly weaponized and is suspected to be the progenitor of the [[Mark 21 nuclear bomb|Mk-21]] gravity bomb. The Mk-21 design project began on [[26 March]], [[1954]] (just three weeks after Bravo) with production of 275 weapons beginning in the fall of 1955. Romeo, relying on natural lithium, was rapidly turned into the [[Mark 17 nuclear bomb|Mk-17 bomb]], the US first [[H bomb]] <ref>[http://www.atomicmuseum.com/Tour/cw2.cfm Development of the Mk 17 bomb], Atomic Museum.com </ref>, and was available to strategic forces as an Emergency Capability by late summer of 1954. Most of the Castle dry fuel devices eventually appeared in the inventory and ultimately grandfathered the majority of [[thermonuclear]] configurations.
In contrast, the [[Lawrence Livermore National Laboratory|Livermore]]-designed Koon design was a failure. Using natural lithium and a heavily modified [[Teller-Ulam]] configuration, the test produced only 110 [[kiloton|Kt]] of an expected 1.5 [[megaton|Mt]]. While engineers at the Radiation Laboratory had hoped it would lead to a promising new field of weapons, it was eventually determined that the design allowed premature heating of the lithium fuel, thereby disrupting the delicate fusion conditions.
==See also==
*[[Katsuko Saruhashi]]
*[[Pacific Proving Grounds]]
*[[Project 4.1]]
==References==
<references/>
==Bibliography==
*{{cite book
| last = The United States Department of Defense
| coauthors = Defense Nuclear Agency
| title =Castle Series
| publisher = United States Government Printing Office
| date = 1982
| location = Washington DC
}}
*{{cite book
| last = The United States Department of Defense
| coauthors = Defense Nuclear Agency
| title =Operation Ivy--1952
| publisher = United States Government Printing Office
| date = 1983
| location = Washington DC
}}
*{{cite book
| last = Rhodes
| first = Richard
| authorlink = Richard Rhodes
| title = Dark Sun
| publisher = Simon & Schuster
| date = 1995
| location = New York, New York
}}
*{{cite book
| last = O'Keefe
| first = Bernard J.
| title = Nuclear Hostages
| publisher = Houghton Mifflin Company
| date = 1983
| location = Boston
}}
*{{cite book
| last = Hacker
| first = Barton C
| title = Elements of Controversy: The Atomic Energy Commission and Radiation Safety in Nuclear Weapons Testing
| publisher = University of California Press
| date = 1994
| location = Los Angeles
}}
== External links ==
{{commons|Operation Castle|Operation Castle}}
* [http://www.archive.org/details/CastleCommandersReport1954 Downloadable/Streamable Declassified Film: Operation Castle Commanders Report, at the Internet Archive]
*[http://www.archive.org/details/MilitaryEffectsStudiesonOperationCastle1954 Downloadable/Streamable Declassified Film: Military Effects Studies Operation Castle, at the Internet Archive]
* [http://nuclearweaponarchive.org/Usa/Tests/Castle.html Operation Castle]
* [http://www.aracnet.com/~pdxavets/castle.htm Operation Castle and photos]
* [http://www.aracnet.com/~pdxavets/brady3.htm Operation Castle: A Radiological Safety Nightmare]
[[Category:American nuclear explosive tests|Castle]]
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