Instruct: Given a question, retrieve relevant passages that can help answer the question.
Query: Which countries have thermonuclear weapons?
Since the atomic bombings of Hiroshima and Nagasaki, nuclear weapons have been detonated over two thousand times for testing and demonstration. Only a few nations possess such weapons or are suspected of seeking them. The only countries known to have detonated nuclear weapons—and acknowledge possessing them—are (chronologically by date of first test) the United States, the Soviet Union (succeeded as a nuclear power by Russia), the United Kingdom, France, China, India, Pakistan, and North Korea. Israel is believed to possess nuclear weapons, though, in a policy of deliberate ambiguity, it does not acknowledge having them. Germany, Italy, Turkey, Belgium and the Netherlands are nuclear weapons sharing states.[4][5][6] South Africa is the only country to have independently developed and then renounced and dismantled its nuclear weapons.[7]
Only six countries—United States, Russia, United Kingdom, China, France, and India—have conducted thermonuclear weapon tests. (Whether India has detonated a "true" multi-staged thermonuclear weapon is controversial.)[15] North Korea claims to have tested a fusion weapon as of January2016, though this claim is disputed.[16] Thermonuclear weapons are considered much more difficult to successfully design and execute than primitive fission weapons. Almost all of the nuclear weapons deployed today use the thermonuclear design because it is more efficient.
Pure fission weapons historically have been the first type to be built by new nuclear powers. Large industrial states with well-developed nuclear arsenals have two-stage thermonuclear weapons, which are the most compact, scalable, and cost effective option once the necessary technical base and industrial infrastructure are built.
Pictures of nuclear weapons themselves (the actual casings) were not made public until 1960, and even those were only mock-ups of the "Fat Man" and "Little Boy" weapons dropped on Japan—not the more powerful weapons developed more recently. Diagrams of the general principles of operation of thermonuclear weapons have been available in very general terms since at least 1969 in at least two encyclopedia articles, and open literature research into inertial confinement fusion has been at least richly suggestive of how the "secondary" and "inter" stages of thermonuclear weapons work.
There are currently no known gun-type weapons in service: advanced nuclear weapon states tended to abandon the design in favor of the implosion-type weapons, boosted fission weapons, and thermonuclear weapons. New nuclear weapon states tend to develop boosted fission and thermonuclear weapons only. All known gun-type nuclear weapons previously built worldwide have been dismantled.
Compared to fission weapons, thermonuclear designs are exceedingly complex, and staged weapons in particular are so complex that only five countries (USA, Russia, France, UK, China) have created them in more than 70 years of research. The fuels for an H-bomb are also far more difficult to create. Several countries with long-standing nuclear weapons programs, such as India and Pakistan, are suspected of striving towards a hybrid or "boosted" design instead, which is easier. Since both fusion weapons and hybrid designs can at times be referred to as "hydrogen bombs", it cannot be said with certainty at present, what type of weapon North Korea may have been referring to in any given test. At present, analysts are skeptical of the 2016 test being a staged thermonuclear design, while noting that the most recent test, in 2017, was considerably more powerful. In 2018, North Korea had offered and was reportedly preparing for inspections at nuclear and missile sites.
As thermonuclear weapons represent the most efficient design for weapon energy yield in weapons with yields above , virtually all the nuclear weapons of this size deployed by the five nuclear-weapon states under the Non-Proliferation Treaty today are thermonuclear weapons using the Teller–Ulam design.
The United States Atomic Energy Commission, directed by David E. Lilienthal until 1950, was in charge of designing and building nuclear weapons. The policy was 100% civilian control. The U.S. had only 9 atomic bombs in 1946, but the stockpile grew to 650 by 1951. Lilienthal wanted to give high priority to peaceful uses, especially nuclear power plants, but coal was cheap and the power industry was not interested. Construction of the first nuclear plant would not begin until 1954. In early 1950, Truman authorized the development of thermonuclear weapons, a more powerful version of atomic bombs. Truman's decision to develop thermonuclear weapons faced opposition from many liberals and some government officials, but Truman believed that the Soviet Union would likely develop the weapons, and he was unwilling to allow the Soviets to have such an advantage. The first test of thermonuclear weaponry was conducted by the United States in 1952, and the Soviet Union performed its own thermonuclear test in August 1953.
In 1972, the DOE declassified a statement that "The fact that in thermonuclear (TN) weapons, a fission 'primary' is used to trigger a TN reaction in thermonuclear fuel referred to as a 'secondary'", and in 1979 added: "The fact that, in thermonuclear weapons, radiation from a fission explosive can be contained and used to transfer energy to compress and ignite a physically separate component containing thermonuclear fuel." To this latter sentence they specified that ""Any elaboration of this statement will be classified."" (emphasis in original) The only statement which may pertain to the "sparkplug" was declassified in 1991, "Fact that fissile and/or fissionable materials are present in some secondaries, material unidentified, location unspecified, use unspecified, and weapons undesignated." In 1998, the DOE declassified the statement that "The fact that materials may be present in channels and the term 'channel filler,' with no elaboration", which may refer to the polystyrene foam (or an analogous substance). (DOE 2001, sect. V.C.)
Virtually all thermonuclear weapons deployed today use the "two-stage" design described above, but it is possible to add additional fusion stages—each stage igniting a larger amount of fusion fuel in the next stage. This technique can be used to construct thermonuclear weapons of arbitrarily large yield, in contrast to fission bombs, which are limited in their explosive force. The largest nuclear weapon ever detonated, the Tsar Bomba of the USSR, which released an energy equivalent of over 50 megatons of TNT (210PJ), was a three-stage weapon. Most thermonuclear weapons are considerably smaller than this, due to practical constraints from missile warhead space and weight requirements.[17]
The Mark 15 is widely described as a transitional design between fission and thermonuclear weapons. The Mark 15 was a staged weapon (see Teller-Ulam design) that used radiation implosion from a fission nuclear primary (RACER IV) to implode a secondary stage. Unlike most modern thermonuclear bombs, most of the Mark 15's destructive energy came from fission reactions. The secondary was made primarily of highly enriched uranium (HEU) around a thermonuclear core. The implosion created fusion reactions whose neutrons increased the yield of the HEU fission reactions, but which would have generated a very significant fission yield by itself.
The Soviet thermonuclear weapons program was aided heavily by Klaus Fuchs. Fuchs’ most valuable contribution to the Soviet weapons program concerned the hydrogen bomb. The idea of a hydrogen bomb arose from discussions between Enrico Fermi and Edward Teller in 1941. From 1943 Teller lectured at Los Alamos on what he called the "super". Following their meeting, Fermi was convinced by Teller to present a series of lectures detailing the current state of research into thermonuclear weapons. In September 1945 Fuchs passed a synopsis of these lectures to the Soviets. This information was important to the Soviets, but not solely for the information about the US bomb project. The importance of this material was in that it confirmed that the United States were working on their own thermonuclear weapon research. Although the information provided by Fuchs regarding the thermonuclear weapons research was not seen as entirely beneficial, it still provided the Soviet Union with knowledge such as the properties of tritium. Tritium is an isotope of hydrogen with two neutrons, which allows for more efficient fusion reactions to occur during the detonation of a nuclear weapon. Discovering the properties of this radioactive material would allow the Soviet Union to develop a more powerful weapon that requires less fuel. Following Fuchs's return, experts from the Soviet Union spent a great deal of time researching his findings for themselves. Even though the Soviets did obtain some original ideas, the findings of this research served to confirm Fuchs's notes from the American lectures on the matter. After his return to England in mid-1946, Fuchs was not again in touch with Soviet intelligence until September 1947, when his controller confirmed the Soviet interest in thermonuclear weapons. In response Fuchs provided details of the "ongoing theoretical superbomb studies in the U.S. under the direction of Teller and Enrico Fermi at the University of Chicago." Fuchs obtained information regardless of the American McMahon Act, which prevented Anglo-American cooperation on nuclear weapons research. Under this act, Fuchs did not have routine access to American collaborators like Fermi and Teller. Fuchs was very close to Teller at Los Alamos, and while there Fuchs had worked on thermonuclear weapons. As Teller later recalled, "he [Fuchs] talked with me and others frequently in depth about our intensive efforts… it was easy and pleasant to discuss my work with him. He also made impressive contributions, and I learned many technical facts from him." Fuchs obtained the information, it energized the Soviets to direct new intelligence activities against research in Chicago. In February 1948 the Soviet Union formally began its hydrogen bomb program. A month later Fuchs again met with Feklisov, an event which "played an exceptional role in the subsequent course of the Soviet thermonuclear bomb program." A report of June 1953 warned that, although no indication of Soviet development of hydrogen bombs had been found, "Soviet research, development and even field testing of thermonuclear reactions based on the disclosures of Fuchs may take place by mid-1953." U.S. intelligence thus recognized for the first time that Fuchs' material held invaluable information for the Soviet thermonuclear weapons program.
A thermonuclear weapon, or fusion weapon, is a second-generation nuclear weapon design which affords vastly greater destructive power than first-generation atomic bombs. Modern fusion weapons consist essentially of two main components: a nuclear fission primary stage (fueled by Uranium-235 or Plutonium-239) and a separate nuclear fusion secondary stage containing thermonuclear fuel: the heavy hydrogen isotopes deuterium and tritium, or in modern weapons lithium deuteride. For this reason thermonuclear weapons are often colloquially called hydrogen bombs, or H-bombs.
Test No. 6 is the codename for China's first test of a three-staged thermonuclear device and, also its sixth nuclear weapons test. The device was detonated at Lop Nur Test Base, or often dubbed as Lop Nur Nuclear Weapon Test Base, in Malan, Xinjiang, on 17 June 1967. With successful testing of this three-stage thermonuclear device, China became the fourth country to have successfully developed a thermonuclear weapon after the United States, Soviet Union and the United Kingdom. It was dropped from a Hong-6 (Chinese manufactured Tu-16) and was parachute-retarded for an airburst at 2960 meters. The bomb was a three-stage device with a boosted U-235 primary and U-238 pusher. The yield was 3.3 megatons.
Research has been done into the possibility of pure fusion bombs: nuclear weapons that consist of fusion reactions without requiring a fission bomb to initiate them. Such a device might provide a simpler path to thermonuclear weapons than one that required development of fission weapons first, and pure fusion weapons would create significantly less nuclear fallout than other thermonuclear weapons, because they would not disperse fission products. In 1998, the United States Department of Energy divulged that the United States had, "...made a substantial investment" in the past to develop pure fusion weapons, but that, "The U.S. does not have and is not developing a pure fusion weapon", and that, "No credible design for a pure fusion weapon resulted from the DOE investment".[18]
The French nuclear testing site was moved to the unpopulated French atolls in the Pacific Ocean. The first test conducted at these new sites was the "Canopus" test in the Fangataufa atoll in French Polynesia on 24 August 1968, the country's first multistage thermonuclear weapon test. The bomb was detonated from a balloon at a height of 520 meters. The result of this test was significant atmospheric contamination. Very little is known about France's development of the Teller–Ulam design, beyond the fact that France detonated a 2.6 Mt device in the 'Canopus" test. France reportedly had great difficulty with its initial development of the Teller-Ulam design, but it later overcame these, and is believed to have nuclear weapons equal in sophistication to the other major nuclear powers.
In 1979 the US Department of Energy sued to suppress the publication of an article by Howard Morland in "The Progressive" magazine detailing design information on thermonuclear and fission nuclear weapons he was able to glean in conversations with officials at several DoE contractor plants active in manufacture of nuclear weapons components. Ray Kidder, a nuclear weapon designer testifying for Morland, identified several open literature sources for the information Morland repeated in his article , while aviation historian Chuck Hansen produced a similar document for US Senator Charles Percy . Morland and "The Progressive" won the case, and Morland published a book on his journalistic research for the article, the trial, and a technical appendix in which he "corrected" what he felt were false assumptions in his original article about the design of thermonuclear weapons in his book, "The Secret That Exploded". The concepts in Morland's book are widely acknowledged in other popular-audience descriptions of the inner workings of Thermonuclear weapons.
Information about the W88 has implied that it is a variation of the standard Teller–Ulam design for thermonuclear weapons. In a thermonuclear weapon such as the W88, nuclear fission in the "primary" part causes nuclear fusion in the "secondary" part, which results in the main explosion. Although the weapon employs fusion in the secondary, most of the explosive yield comes from fission of nuclear material in the primary, secondary, and casing.
The Chiefs of Staff Committee and the Churchill ministry, however, believed that
The government decided on 27 July 1954 to begin development of a thermonuclear bomb, and announced its plans in February 1955. British knowledge of thermonuclear weapons was based on the work done at the Los Alamos Laboratory during the war. Two British scientists, Egon Bretscher and Klaus Fuchs, had attended the conference there on the Super (as it was then called) in April 1946, and Chadwick had written a secret report on it in May 1946, but the design was found to be unworkable. Some intelligence about Joe 4 was derived from its debris, which was provided to Britain under the 1948 "Modus Vivendi". Penney established three megaton bomb projects at Aldermaston: Orange Herald, a large boosted fission weapon; Green Bamboo, an interim thermonuclear design similar to the Soviet Layer Cake used in Joe 4 and the American Alarm Clock; and Green Granite, a true thermonuclear design.
North Korea claimed to have tested its miniaturised thermonuclear bomb on 6 January 2016. North Korea's first three nuclear tests (2006, 2009 and 2013) were relatively low yield and do not appear to have been of a thermonuclear weapon design. In 2013, the South Korean Defense Ministry speculated that North Korea may be trying to develop a "hydrogen bomb" and such a device may be North Korea's next weapons test. In January 2016, North Korea claimed to have successfully tested a hydrogen bomb, although only a magnitude 5.1 seismic event was detected at the time of the test, a similar magnitude to the 2013 test of a 6–9 kt atomic bomb. These seismic recordings cast doubt upon North Korea's claim that a hydrogen bomb was tested and suggest it was a non-fusion nuclear test.
In 1953, shortly after the Americans tested a thermonuclear weapon in 1952, followed by the Soviets with Joe 4, and before the UK government took a decision in July 1954 to develop a thermonuclear weapon, the Atomic Weapons Research Establishment at Aldermaston was asked about the possibilities for a very large pure fission bomb with a yield of one megaton. This study referred to the Zodiak Mk.3 bomb, but progressed no further than a rudimentary study. At this time studies were also started that ultimately led to a decision in 1954 to develop a thermonuclear weapon, and the design studies were split into two tracks because the British at that time had not yet discovered the Teller-Ulam technique necessary to initiate fusion. One track led to an intermediate design, the so-called Type A thermonuclear design, similar to the Alarm Clock and layer cake hybrid designs of other nuclear powers; although these designs are now regarded as large boosted fission weapons, and no longer regarded as thermonuclear weapons that derive a very large part of their energy from a fusion reaction, designated by the British as Type B, but as hybrids. The British hybrid weapon was known as Green Bamboo, weighed approx 4,500 lb (2,045 kg) and its spherical shape measured approx 45 inches diameter with a 72-point implosion system. This Green Bamboo weapon was intended as the warhead for all projected British strategic delivery systems of the period; the Yellow Sun Stage 1 air-dropped bomb, and the Blue Steel air-launched stand-off missile. The large girth of these weapons was designed to accommodate the diameter of Green Bamboo's implosion sphere.
Thermonuclear fusion is a way to achieve nuclear fusion by using extremely high temperatures. There are two forms of thermonuclear fusion: "uncontrolled", in which the resulting energy is released in an uncontrolled manner, as it is in thermonuclear weapons ("hydrogen bombs") and in most stars; and "controlled", where the fusion reactions take place in an environment allowing some or all of the energy released to be harnessed for constructive purposes. This article focuses on the latter.
The thermonuclear weapons race between the United States and the Soviet Union exceeded all expectations set out before the scientists who took part. Two countries creating thermonuclear weapons with such energy yields from two different design methods proved to be the crowning achievement for science in the 1950s. Of course, the successful and promising work from both the United States and the Soviet Union only spurred each country to push for stronger weapons, as the floodgates of thermonuclear weapon potential had been opened. This was, of course, entirely the norm at the time considering that the Cold War was in full swing. It was a significant boost to Soviet morale knowing that the Soviet Union's physicists, engineers, scientist, and great minds were able to not only compete with the Americans, but also able to out perform them in some key areas of weapon and technological development.
All so-called "fission-fusion-fission" weapons (i.e., all conventional modern thermonuclear warheads) employ the additional step of "jacket fissioning", using fusion neutrons. This works as follows: the high-energy or "fast" neutrons generated by fusion are used to fission a fissionable jacket located around the fusion stage. In the past this jacket was often made of natural or depleted uranium; but today's weapons in which there is a premium on weight and size (i.e., virtually all modern strategic weapons) use moderately-to-highly enriched uranium as the jacketing material (see Oralloy thermonuclear warheads section below). The fast fission of the secondary jacket in fission-fusion-fission bombs is sometimes referred to as a "third stage" in the bomb, but it should not be confused with the obsolete true three-stage thermonuclear design, in which there existed another complete tertiary fusion stage.
Strauss, however, deeply distrusted Oppenheimer. He had become aware of Oppenheimer's former Communist affiliations before World War II and questionable behavior during the war, and he began to think that Oppenheimer might even be a Soviet spy. Strauss was also suspicious of Oppenheimer's tendency to downplay Soviet capabilities. In 1953, Oppenheimer stated in the July edition of "Foreign Affairs" that he believed the Soviets were "about four years behind" in atomic weapons development. The US had exploded the first thermonuclear device the previous year, but it required a two-story building filled with refrigeration equipment to chill the liquid hydrogen. However, only a month after Oppenheimer made his proclamation, in August 1953, the Soviet Union declared and US sensors confirmed that it had tested its own hydrogen bomb. (It was not, however, a staged thermonuclear weapon of the Teller-Ulam design. Scholars have debated for some time whether the Soviet Joe 4 device should be considered a true hydrogen bomb. The first Soviet test of an undisputedly "true" hydrogen bomb was not until 1955.) Moreover, the Soviet device relied on solid lithium-6 deuteride, rather than liquid hydrogen, to boost the yield, making the Soviet device the first truly-deliverable thermonuclear weapon, which proved that the United States was the country trailing technologically in nuclear weapon capability.