Nuclear Weapons Design are physical, chemical, and engineering arrangements that cause the physics package of a nuclear weapon to detonate. There are three existing basic design types:
205-410: A thermonuclear weapon , fusion weapon or hydrogen bomb ( H bomb ) is a second-generation nuclear weapon design . Its greater sophistication affords it vastly greater destructive power than first-generation nuclear bombs , a more compact size, a lower mass, or a combination of these benefits. Characteristics of nuclear fusion reactions make possible the use of non-fissile depleted uranium as
410-408: A hohlraum or radiation case. The "George" shot of Operation Greenhouse of 9 May 1951 tested the basic concept for the first time on a very small scale. As the first successful (uncontrolled) release of nuclear fusion energy, which made up a small fraction of the 225 kt (940 TJ ) total yield, it raised expectations to a near certainty that the concept would work. On 1 November 1952,
615-416: A nuclear fission primary stage (fueled by U or Pu ) and a separate nuclear fusion secondary stage containing thermonuclear fuel: heavy isotopes of hydrogen ( deuterium and tritium ) as the pure element or in modern weapons lithium deuteride . For this reason, thermonuclear weapons are often colloquially called hydrogen bombs or H-bombs . A fusion explosion begins with
820-735: A secondary section that consists of fusion fuel . The energy released by the primary compresses the secondary through the process of radiation implosion , at which point it is heated and undergoes nuclear fusion . This process could be continued, with energy from the secondary igniting a third fusion stage; the Soviet Union's AN602 " Tsar Bomba " is thought to have been a three-stage fission-fusion-fusion device. Theoretically by continuing this process thermonuclear weapons with arbitrarily high yield could be constructed. This contrasts with fission weapons, which are limited in yield because only so much fission fuel can be amassed in one place before
1025-425: A sixth nuclear test just a few hours after photographs of North Korean leader Kim Jong-un inspecting a device resembling a thermonuclear weapon warhead were released. Initial estimates in first few days were between 70 and 160 kilotons and were raised over a week later to range of 250 to over 300 kilotons. Jane's Information Group estimated, based mainly on visual analysis of propaganda pictures, that
1230-571: A 2.6 Mt device in the " Canopus " test in August 1968. On 11 May 1998, India announced that it has detonated a hydrogen bomb in its Operation Shakti tests (" Shakti I ", specifically). Some non-Indian analysts, using seismographic readings, have suggested that it might not be the case by pointing at the low yield of the test, which they say is close to 30 kilotons (as opposed to 45 kilotons announced by India). However, some non-Indian experts agree with India. Dr. Harold M. Agnew , former director of
1435-407: A 5 kilogram mass produces 9.68 watts of thermal power. Such a piece would feel warm to the touch, which is no problem if that heat is dissipated promptly and not allowed to build up the temperature. But this is a problem inside a nuclear bomb. For this reason bombs using Pu fuel use aluminum parts to wick away the excess heat, and this complicates bomb design because Al plays no active role in
1640-566: A Teller–Ulam design June 1967 (" Test No. 6 "), a mere 32 months after detonating its first fission weapon (the shortest fission-to-fusion development yet known), with a yield of 3.3 Mt. Little is known about the Chinese thermonuclear program. Development of the bomb was led by Yu Min . Very little is known about the French development of the Teller–Ulam design beyond the fact that it detonated
1845-430: A design could not produce thermonuclear weapons whose explosive yields could be made arbitrarily large (unlike U.S. designs at that time). The fusion layer wrapped around the fission core could only moderately multiply the fission energy (modern Teller–Ulam designs can multiply it 30-fold). Additionally, the whole fusion stage had to be imploded by conventional explosives, along with the fission core, substantially increasing
2050-497: A dozen megatons, which was generally considered enough to destroy even the most hardened practical targets (for example, a control facility such as the Cheyenne Mountain Complex ). Even such large bombs have been replaced by smaller yield nuclear bunker buster bombs. For destruction of cities and non-hardened targets, breaking the mass of a single missile payload down into smaller MIRV bombs in order to spread
2255-456: A few specific incidents outlined in a section below. The basic principle of the Teller–Ulam configuration is the idea that different parts of a thermonuclear weapon can be chained together in stages, with the detonation of each stage providing the energy to ignite the next stage. At a minimum, this implies a primary section that consists of an implosion-type fission bomb (a "trigger"), and
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#17327728482272460-495: A fission 'primary' is used to trigger a TN reaction in thermonuclear fuel referred to as a 'secondary'", and in 1979, it 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 the latter sentence, it specified, "Any elaboration of this statement will be classified." (emphasis in original) The only statement that may pertain to
2665-414: A free neutron hits the nucleus of a fissile atom like uranium-235 ( U), the uranium nucleus splits into two smaller nuclei called fission fragments, plus more neutrons (for U three about as often as two; an average of just under 2.5 per fission). The fission chain reaction in a supercritical mass of fuel can be self-sustaining because it produces enough surplus neutrons to offset losses of neutrons escaping
2870-451: A high-yield explosion. A W88 warhead manages to yield up to 475 kilotonnes of TNT (1,990 TJ) with a physics package 68.9 inches (1,750 mm) long, with a maximum diameter of 21.8 inches (550 mm), and by different estimates weighing in a range from 175 to 360 kilograms (386 to 794 lb). The smaller warhead allows more of them to fit onto a single missile and improves basic flight properties such as speed and range. The idea of
3075-556: A liquid state meant that the "Ivy Mike" device was too heavy and too complex to be of practical use. The first deployable Teller–Ulam weapon in the US would not be developed until 1954, when the liquid deuterium fuel of the "Ivy Mike" device would be replaced with a dry fuel of lithium deuteride and tested in the " Castle Bravo " shot (the device was codenamed the Shrimp ). The dry lithium mixture performed much better than had been expected, and
3280-488: A massive effort was mounted to re-invent the process. An impurity crucial to the properties of the old Fogbank was omitted during the new process. Only close analysis of new and old batches revealed the nature of that impurity. The manufacturing process used acetonitrile as a solvent , which led to at least three evacuations of the Fogbank plant in 2006. Widely used in the petroleum and pharmaceutical industries, acetonitrile
3485-545: A matter of inspiration” and was “therefore, unpredictable” and “largely accidental.” At the Oppenheimer hearing, in 1954, Bethe spoke of Teller's “stroke of genius” in the invention of the H-bomb. And finally in 1997 Bethe stated that “the crucial invention was made in 1951, by Teller.” Other scientists (antagonistic to Teller, such as J. Carson Mark ) have claimed that Teller would have never gotten any closer without
3690-564: A million times more energy than comparable chemical reactions, making nuclear bombs a million times more powerful than non-nuclear bombs, which a French patent claimed in May 1939. In some ways, fission and fusion are opposite and complementary reactions, but the particulars are unique for each. To understand how nuclear weapons are designed, it is useful to know the important similarities and differences between fission and fusion. The following explanation uses rounded numbers and approximations. When
3895-437: A necessity for gun-assembled bombs, with their much greater insertion time and much greater mass of fuel required (because of the lack of fuel compression). There is another source of free neutrons that can spoil a fission explosion. All uranium and plutonium nuclei have a decay mode that results in energetic alpha particles . If the fuel mass contains impurity elements of low atomic number (Z), these charged alphas can penetrate
4100-580: A part of an idea which I already had worked out and difficulty getting people to listen to. He was willing to sign a paper. When it then came to defending that paper and really putting work into it, he refused. He said, "I don't believe in it." The issue is controversial. Bethe in his “Memorandum on the History of the Thermonuclear Program” (1952) cited Teller as the discoverer of an “entirely new approach to thermonuclear reactions”, which “was
4305-576: A possibility. It was first used in thermonuclear weapons with the W76 thermonuclear warhead and produced at a plant in the Y-12 Complex at Oak Ridge, Tennessee , for use in the W76. Production of Fogbank lapsed after the W76 production run ended. The W76 Life Extension Program required more Fogbank to be made. This was complicated by the fact that the original Fogbank's properties were not fully documented, so
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#17327728482274510-428: A protected location outside the physics package, from which they penetrate the pit. This method allows better timing of the first fission events in the chain reaction, which optimally should occur at the point of maximum compression/supercriticality. Timing of the neutron injection is a more important parameter than the number of neutrons injected: the first generations of the chain reaction are vastly more effective due to
4715-492: A relatively low yield and do not appear to have been of a thermonuclear weapon design. In 2013, the South Korean Defense Ministry had speculated that North Korea might be trying to develop a "hydrogen bomb" and such a device might be North Korea's next weapons test. In January 2016, North Korea claimed to have successfully tested a hydrogen bomb, but only a magnitude 5.1 seismic event was detected at
4920-405: A small neutron absorption cross section and helps protect the plutonium against corrosion . A drawback is that gallium compounds are corrosive and so if the plutonium is recovered from dismantled weapons for conversion to plutonium dioxide for power reactors , there is the difficulty of removing the gallium. Because plutonium is chemically reactive it is common to plate the completed pit with
5125-599: A thermonuclear fusion bomb ignited by a smaller fission bomb was first proposed by Enrico Fermi to his colleague Edward Teller when they were talking at Columbia University in September 1941, at the start of what would become the Manhattan Project . Teller spent much of the Manhattan Project attempting to figure out how to make the design work, preferring it over work on the atomic bomb, and over
5330-484: A thin layer of inert metal, which also reduces the toxic hazard. The gadget used galvanic silver plating; afterward, nickel deposited from nickel tetracarbonyl vapors was used, but thereafter and since, gold became the preferred material. Recent designs improve safety by plating pits with vanadium to make the pits more fire-resistant. The first improvement on the Fat Man design was to put an air space between
5535-506: A true implosion. History of the Teller%E2%80%93Ulam design The Teller–Ulam design is a technical concept behind modern thermonuclear weapons , also known as hydrogen bombs . The design – the details of which are military secrets and known to only a handful of major nations – is believed to be used in virtually all modern nuclear weapons that make up the arsenals of the major nuclear powers. The idea of using
5740-408: A variety of interpersonal strategies to encourage informational responses from them (such as by asking questions such as "Do they still use sparkplugs?" even if he was unaware what the latter term specifically referred to). (Morland 1981) Morland eventually concluded that the "secret" was that the primary and secondary were kept separate and that radiation pressure from the primary compressed
5945-466: A variety of more complicated circumstances, the DOE case began to wane, as it became clear that some of the data it attempted to claim as "secret" had been published in a students' encyclopedia a few years earlier. After another hydrogen bomb speculator, Chuck Hansen , had his own ideas about the "secret" (quite different from Morland's) published in a Wisconsin newspaper, the DOE claimed The Progressive case
6150-508: A very small scale (and the next shot in the series, "Item," was the first boosted fission weapon ), raising expectations to a near certainty that the concept would work. On November 1, 1952, the Teller–Ulam configuration was tested in the " Ivy Mike " shot at an island in the Enewetak atoll, with a yield of 10.4 megatons of TNT (44 PJ) (over 450 times more powerful than the bomb dropped on Nagasaki during World War II). The device, dubbed
6355-465: A weapon, they argued, could only be used against large civilian populations, and could thus only be used as a weapon of genocide. Many scientists, such as Teller's colleague Hans Bethe (who had discovered stellar nucleosynthesis , the nuclear fusion that takes place in stars ), urged that the United States should not develop such weapons and set an example towards the Soviet Union. Promoters of
Thermonuclear weapon - Misplaced Pages Continue
6560-428: A while, many scientists thought (and hoped) that the weapon itself would be impossible to construct. The exact history of the Teller–Ulam breakthrough is not completely known, partly because of numerous conflicting personal accounts and also by the continued classification of documents that would reveal which was closer to the truth. Previous models of the "Super" had apparently placed the fusion fuel either surrounding
6765-464: A yield equivalent to 400 kt (1,700 TJ) (only 15%– 20% from fusion), the Sloika device did, however, have the advantage of being a weapon which could actually be delivered to a military target, unlike the "Ivy Mike" device, though it was never widely deployed. Teller had proposed a similar design as early as 1946, dubbed the "Alarm Clock" (meant to "wake up" research into the "Super"), though it
6970-637: Is about 180 million electron volts (MeV); i.e., 74 TJ/kg. Only 7% of this is gamma radiation and kinetic energy of fission neutrons. The remaining 93% is kinetic energy (or energy of motion) of the charged fission fragments, flying away from each other mutually repelled by the positive charge of their protons (38 for strontium, 54 for xenon). This initial kinetic energy is 67 TJ/kg, imparting an initial speed of about 12,000 kilometers per second (i.e. 1.2 cm per nanosecond). The charged fragments' high electric charge causes many inelastic coulomb collisions with nearby nuclei, and these fragments remain trapped inside
7175-474: Is called the D-T reaction. Using the heat and pressure of fission, hydrogen-2, or deuterium ( D), fuses with hydrogen-3, or tritium ( T), to form helium-4 ( He) plus one neutron (n) and energy: The total energy output, 17.6 MeV, is one tenth of that with fission, but the ingredients are only one-fiftieth as massive, so the energy output per unit mass is approximately five times as great. In this fusion reaction, 14 of
7380-410: Is estimated that only about 20% of the plutonium underwent fission; the rest, about 5 kg (11 lb), was scattered. An implosion shock wave might be of such short duration that only part of the pit is compressed at any instant as the wave passes through it. To prevent this, a pusher shell may be needed. The pusher is located between the explosive lens and the tamper. It works by reflecting some of
7585-460: Is flammable and toxic. Y-12 is the sole producer of Fogbank. A simplified summary of the above explanation is: How exactly the energy is "transported" from the primary to the secondary has been the subject of some disagreement in the open press but is thought to be transmitted through the X-rays and gamma rays that are emitted from the fissioning primary . This energy is then used to compress
7790-637: Is hot enough to emit black-body radiation in the X-ray spectrum. These X-rays are absorbed by the surrounding air, producing the fireball and blast of a nuclear explosion. Most fission products have too many neutrons to be stable so they are radioactive by beta decay , converting neutrons into protons by throwing off beta particles (electrons), neutrinos and gamma rays. Their half-lives range from milliseconds to about 200,000 years. Many decay into isotopes that are themselves radioactive, so from 1 to 6 (average 3) decays may be required to reach stability. In reactors,
7995-521: Is interpreted as being at least partially correct, but to what degree it lacks information or has incorrect information is not known with any great confidence. The difficulty which a number of nations had in developing the Teller–Ulam design (even when they understood the design, such as with the United Kingdom) makes it somewhat unlikely that the simple information alone is what provides the ability to manufacture thermonuclear weapons. Nevertheless,
8200-473: Is known as the pit . Some weapons tested during the 1950s used pits made with U-235 alone, or in composite with plutonium , but all-plutonium pits are the smallest in diameter and have been the standard since the early 1960s. Casting and then machining plutonium is difficult not only because of its toxicity, but also because plutonium has many different metallic phases . As plutonium cools, changes in phase result in distortion and cracking. This distortion
8405-404: Is normally overcome by alloying it with 30–35 mMol (0.9–1.0% by weight) gallium , forming a plutonium-gallium alloy , which causes it to take up its delta phase over a wide temperature range. When cooling from molten it then has only a single phase change, from epsilon to delta, instead of the four changes it would otherwise pass through. Other trivalent metals would also work, but gallium has
Thermonuclear weapon - Misplaced Pages Continue
8610-406: Is of central importance. The plenitude and cheapness of both bulk dry fusion fuel (lithium deuteride) and U (a byproduct of uranium enrichment) permit the economical production of very large nuclear arsenals, in comparison to pure fission weapons requiring the expensive U or Pu fuels. Fusion produces neutrons which dissipate energy from the reaction. In weapons, the most important fusion reaction
8815-487: Is omitted, by replacing the uranium tamper with one made of lead , for example, the overall explosive force is reduced by approximately half but the amount of fallout is relatively low. The neutron bomb is a hydrogen bomb with an intentionally thin tamper, allowing as many of the fast fusion neutrons as possible to escape. Current technical criticisms of the idea of "foam plasma pressure" focus on unclassified analysis from similar high energy physics fields that indicate that
9020-417: Is one in which the percentage of fission-produced neutrons captured by other neighboring fissile nuclei is large enough that each fission event, on average, causes more than one follow-on fission event. Neutrons released by the first fission events induce subsequent fission events at an exponentially accelerating rate. Each follow-on fissioning continues a sequence of these reactions that works its way throughout
9225-529: Is one order of magnitude greater than the higher proposed plasma pressures and nearly two orders of magnitude greater than calculated radiation pressure. No mechanism to avoid the absorption of energy into the radiation case wall and the secondary tamper has been suggested, making ablation apparently unavoidable. The other mechanisms appear to be unneeded. United States Department of Defense official declassification reports indicate that foamed plastic materials are or may be used in radiation case liners, and despite
9430-477: Is present, one also has some amounts of the following two net reactions: Most lithium is Li, and this gave Castle Bravo a yield 2.5 times larger than expected. The neutrons are supplied by the nuclear reactor in a way similar to production of plutonium Pu from U feedstock: target rods of the Li feedstock are arranged around a uranium-fueled core, and are removed for processing once it has been calculated that most of
9635-460: Is the Soviet early Sloika design. In essence, the Teller–Ulam configuration relies on at least two instances of implosion occurring: first, the conventional (chemical) explosives in the primary would compress the fissile core, resulting in a fission explosion many times more powerful than that which chemical explosives could achieve alone (first stage). Second, the radiation from the fissioning of
9840-435: Is the dominant process that produces radioactive fission product fallout . Before Ivy Mike, Operation Greenhouse in 1951 was the first American nuclear test series to test principles that led to the development of thermonuclear weapons. Sufficient fission was achieved to boost the associated fusion device, and enough was learned to achieve a full-scale device within a year. The design of all modern thermonuclear weapons in
10045-426: Is the fusion fuel, usually a form of lithium deuteride , which is used because it is easier to weaponize than liquefied tritium/deuterium gas. This dry fuel, when bombarded by neutrons, produces tritium, a heavy isotope of hydrogen that can undergo nuclear fusion, along with the deuterium present in the mixture. (See the article on nuclear fusion for a more detailed technical discussion of fusion reactions.) Inside
10250-446: Is the medium by which the outside pressure (force acting on the surface area of the secondary) is transferred to the mass of fusion fuel. The proposed tamper-pusher ablation mechanism posits that the outer layers of the thermonuclear secondary's tamper-pusher are heated so extremely by the primary's X-ray flux that they expand violently and ablate away (fly off). Because total momentum is conserved, this mass of high velocity ejecta impels
10455-423: Is the mother, because he remained with the child. As for me, I guess I am the midwife." The Teller–Ulam breakthrough—the details of which are still classified—was apparently the separation of the fission and fusion components of the weapons, and to use the radiation produced by the fission bomb to first compress the fusion fuel before igniting it. Some sources have suggested that Ulam initially proposed compressing
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#173277284822710660-416: Is the primary example). Such processes have resulted in a body of unclassified knowledge about nuclear bombs that is generally consistent with official unclassified information releases and related physics and is thought to be internally consistent, though there are some points of interpretation that are still considered open. The state of public knowledge about the Teller–Ulam design has been mostly shaped from
10865-551: Is thought to be a standard implosion method fission bomb, though likely with a core boosted by small amounts of fusion fuel (usually 1:1 deuterium : tritium gas) for extra efficiency; the fusion fuel releases excess neutrons when heated and compressed, inducing additional fission. When fired, the Pu or U core would be compressed to a smaller sphere by special layers of conventional high explosives arranged around it in an explosive lens pattern, initiating
11070-495: Is thought to have used multiple stages (including more than one tertiary fusion stage) in their 50 Mt (210 PJ) (100 Mt (420 PJ) in intended use) Tsar Bomba. The fissionable jacket could be replaced with lead, as was done with the Tsar Bomba. If any hydrogen bombs have been made from configurations other than those based on the Teller–Ulam design, the fact of it is not publicly known. A possible exception to this
11275-584: Is to incorporate material with a large cross-section for neutron capture, such as boron (specifically B comprising 20% of natural boron). Naturally this neutron absorber must be removed before the weapon is detonated. This is easy for a gun-assembled bomb: the projectile mass simply shoves the absorber out of the void between the two subcritical masses by the force of its motion. The use of plutonium affects weapon design due to its high rate of alpha emission. This results in Pu metal spontaneously producing significant heat;
11480-408: Is widely assumed to be beryllium , which fits that description and would also moderate the neutron flux from the primary. Some material to absorb and re-radiate the X-rays in a particular manner may also be used. Candidates for the "special material" are polystyrene and a substance called " Fogbank ", an unclassified codename. Fogbank's composition is classified, though aerogel has been suggested as
11685-686: The Los Alamos Laboratory and a remote site 14.3 km (8.9 mi) east of it in Bayo Canyon, proved the practicality of the implosion design for a fission device, with the February 1945 tests positively determining its usability for the final Trinity/Fat Man plutonium implosion design. The key to Fat Man's greater efficiency was the inward momentum of the massive U-238 tamper. (The natural uranium tamper did not undergo fission from thermal neutrons, but did contribute perhaps 20% of
11890-673: The Los Alamos National Laboratory , said that India's assertion of having detonated a staged thermonuclear bomb was believable. The British seismologist Roger Clarke argued that seismic magnitudes suggested a combined yield of up to 60 kilotonnes, consistent with the Indian announced total yield of 56 kilotonnes. Professor Jack Evernden, a US seismologist, has always maintained that for correct estimation of yields, one should "account properly for geological and seismological differences between test sites." His estimation of
12095-503: The Sausage , used an extra-large fission bomb as a "trigger" and liquid deuterium , kept in its liquid state by 20 short tons (18 tonnes) of cryogenic equipment, as its fusion fuel, and it had a mass of around 80 short tons (73 tonnes) altogether. An initial press blackout was attempted, but it was soon announced that the US had detonated a megaton-range hydrogen bomb. The elaborate refrigeration plant necessary to keep its fusion fuel in
12300-570: The Trident II SLBM, had a prolate primary (code-named Komodo ) and a spherical secondary (code-named Cursa ) inside a specially shaped radiation case (known as the "peanut" for its shape). The value of an egg-shaped primary lies apparently in the fact that a MIRV warhead is limited by the diameter of the primary: if an egg-shaped primary can be made to work properly, then the MIRV warhead can be made considerably smaller yet still deliver
12505-513: The Trinity device and the Fat Man (Nagasaki) bomb, nearly identical plutonium fission through implosion designs were used. The Fat Man device specifically used 6.2 kg (14 lb), about 350 ml or 12 US fl oz in volume, of Pu-239 , which is only 41% of bare-sphere critical mass (see Fat Man article for a detailed drawing) . Surrounded by a U-238 reflector/tamper,
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#173277284822712710-425: The Trinity test , after the atomic bombings of Japan scientists at Los Alamos were surprised by how devastating the effects of the weapon had been. Many of the scientists rebelled against the notion of creating a weapon thousands of times more powerful than the first atomic bombs. For the scientists the question was in part technical—the weapon design was still quite uncertain and unworkable—and in part moral: such
12915-609: The United States Department of Energy has been not to acknowledge the leaking of design information, as such acknowledgment would potentially validate the information as accurate. In a small number of prior cases, the U.S. government has attempted to censor weapons information in the public press , with limited success. According to the New York Times , physicist Kenneth W. Ford defied government orders to remove classified information from his book Building
13120-611: The W-80 the gas expansion velocity is roughly 410 km/s (41 cm/μs) and the implosion velocity 570 km/s (57 cm/μs). The pressure due to the ablating material is calculated to be 5.3 billion bars (530 trillion pascals ) in the Ivy Mike device and 64 billion bars (6.4 quadrillion pascals) in the W-80 device. Comparing the three mechanisms proposed, it can be seen that: The calculated ablation pressure
13325-545: The W47 warhead deployed on Polaris ballistic missile submarines , megaton-class warheads were as small as 18 inches (0.46 m) in diameter and 720 pounds (330 kg) in weight. Further innovation in miniaturizing warheads was accomplished by the mid-1970s, when versions of the Teller–Ulam design were created that could fit ten or more warheads on the end of a small MIRVed missile. The first Soviet fusion design, developed by Andrei Sakharov and Vitaly Ginzburg in 1949 (before
13530-434: The detonation of the fission primary stage. Its temperature soars past 100 million kelvin , causing it to glow intensely with thermal ("soft") X-rays . These X-rays flood the void (the "radiation channel" often filled with polystyrene foam ) between the primary and secondary assemblies placed within an enclosure called a radiation case, which confines the X-ray energy and resists its outward pressure. The distance separating
13735-557: The neutron flux from the primary to prematurely begin heating the secondary, weakening the compression enough to prevent any fusion. There is very little detailed information in the open literature about the mechanism of the interstage. One of the best sources is a simplified diagram of a British thermonuclear weapon similar to the American W80 warhead. It was released by Greenpeace in a report titled "Dual Use Nuclear Technology" . The major components and their arrangement are in
13940-408: The nuclear chain reaction that powers the conventional "atomic bomb". The secondary is usually shown as a column of fusion fuel and other components wrapped in many layers. Around the column is first a "pusher- tamper ", a heavy layer of uranium-238 ( U ) or lead that helps compress the fusion fuel (and, in the case of uranium, may eventually undergo fission itself). Inside this
14145-467: The secondary before fusion ("radiation implosion"), in the spring of 1954. Sakharov's "Third Idea", as the Teller–Ulam design was known in the Soviet Union, was tested in the shot " RDS-37 " in November 1955 with a yield of 1.6 Mt (6.7 PJ). If the Soviet Union had been able to analyze the fallout data from either the "Ivy Mike" or "Castle Bravo" tests, they could have been able to discern that
14350-598: The secondary before igniting it. When an early draft of the article, to be published in The Progressive magazine, was sent to the DOE after it had fallen into the hands of a professor who was opposed to Morland's goal, the DOE requested that the article not be published and pressed for a temporary injunction. After a short court hearing in which the DOE argued that Morland's information was (1). likely derived from classified sources, (2). if not derived from classified sources, itself counted as "secret" information under
14555-423: The secondary through the shock waves generated by the primary and that it was Teller who then realized that the radiation from the primary would be able to accomplish the task (hence " radiation implosion "). However, compression alone would not have been enough and the other crucial idea, staging the bomb by separating the primary and secondary, seems to have been exclusively contributed by Ulam. The elegance of
14760-460: The secondary . The crucial detail of how the X-rays create the pressure is the main remaining disputed point in the unclassified press. There are three proposed theories: The radiation pressure exerted by the large quantity of X-ray photons inside the closed casing might be enough to compress the secondary. Electromagnetic radiation such as X-rays or light carries momentum and exerts a force on any surface it strikes. The pressure of radiation at
14965-470: 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.) Whether
15170-448: The " Teller–Ulam design " is not definitively known in the public domain—the degree of credit assigned to Teller by his contemporaries is almost exactly commensurate with how well they thought of Teller in general. In an interview with Scientific American from 1999, Teller told the reporter: I contributed; Ulam did not. I'm sorry I had to answer it in this abrupt way. Ulam was rightly dissatisfied with an old approach. He came to me with
15375-460: The " born secret " clause of the 1954 Atomic Energy Act , and (3). dangerous and would encourage nuclear proliferation , Morland and his lawyers disagreed on all points, but the injunction was granted, as the judge in the case thought that it was safer to grant the injunction and allow Morland, et al., to appeal, which they did in United States v. The Progressive, et al. (1979). Through
15580-544: The "Castle Bravo" device that was detonated in 1954 had a yield two-and-a-half times greater than had been expected (at 15 Mt (63 PJ), it was also the most powerful bomb ever detonated by the United States). Because much of the yield came from the final fission stage of its U tamper, it generated much nuclear fallout , which caused one of the worst nuclear accidents in US history after unforeseen weather patterns blew it over populated areas of
15785-520: The "Mike" test with the hope of analyzing it for information, a chemist at Arzamas-16 (the Soviet weapons laboratory) had mistakenly poured the concentrate down the drain before it could be analyzed. Only in the fall of 1952 did the Soviet Union set up an organized system for monitoring fallout data. Nonetheless, the memoirs also say that the yield from one of the American tests , which became an international incident involving Japan, told Sakharov that
15990-536: The "classical Super" design were public knowledge even before thermonuclear weapons were first tested. After Truman ordered the crash program to develop the hydrogen bomb in January 1950, the Boston Daily Globe published a cutaway description of a hypothetical hydrogen bomb with the caption Artist's conception of how H-bomb might work using atomic bomb as a mere "trigger" to generate enough heat to set up
16195-407: The 17.6 MeV (80% of the energy released in the reaction) shows up as the kinetic energy of the neutron, which, having no electric charge and being almost as massive as the hydrogen nuclei that created it, can escape the scene without leaving its energy behind to help sustain the reaction – or to generate x-rays for blast and fire. The only practical way to capture most of the fusion energy is to trap
16400-581: The British fusion bomb, with Sir William Penney in charge of the project. British knowledge on how to make a thermonuclear fusion bomb was rudimentary, and at the time the United States was not exchanging any nuclear knowledge because of the Atomic Energy Act of 1946 . The United Kingdom had worked closely with the Americans on the Manhattan Project. British access to nuclear weapons information
16605-499: The Fat Man's pit was brought close to critical mass by the neutron-reflecting properties of the U-238. During detonation, criticality was achieved by implosion. The plutonium pit was squeezed to increase its density by simultaneous detonation, as with the "Trinity" test detonation three weeks earlier, of the conventional explosives placed uniformly around the pit. The explosives were detonated by multiple exploding-bridgewire detonators . It
16810-621: The H Bomb: A Personal History . Ford claims he used only pre-existing information and even submitted a manuscript to the government, which wanted to remove entire sections of the book for concern that foreign states could use the information. Though large quantities of vague data have been officially released—and larger quantities of vague data have been unofficially leaked by former bomb designers—most public descriptions of nuclear weapon design details rely to some degree on speculation, reverse engineering from known information, or comparison with similar fields of physics ( inertial confinement fusion
17015-515: The H-bomb's "thermonuclear fusion" process . The fact that a large proportion of the yield of a thermonuclear device stems from the fission of a uranium 238 tamper (fission-fusion-fission principle) was revealed when the Castle Bravo test "ran away," producing a much higher yield than originally estimated and creating large amounts of nuclear fallout. In 1972, the DOE declassified a statement that "The fact that in thermonuclear (TN) weapons,
17220-478: The Soviets had a working fission bomb), was dubbed the Sloika , after a Russian layer cake , and was not of the Teller–Ulam configuration. It used alternating layers of fissile material and lithium deuteride fusion fuel spiked with tritium (this was later dubbed Sakharov's "First Idea"). Though nuclear fusion might have been technically achievable, it did not have the scaling property of a "staged" weapon. Thus, such
17425-440: The Soviets searched for an alternative design. The "Second Idea", as Sakharov referred to it in his memoirs, was a previous proposal by Ginzburg in November 1948 to use lithium deuteride in the bomb, which would, in the course of being bombarded by neutrons, produce tritium and free deuterium. In late 1953 physicist Viktor Davidenko achieved the first breakthrough of staging the reactions. The next breakthrough of radiation implosion
17630-618: The Teller–Ulam configuration was tested at full scale in the "Ivy Mike" shot at an island in the Enewetak Atoll , with a yield of 10.4 Mt (44 PJ ) (over 450 times more powerful than the bomb dropped on Nagasaki during World War II ). The device, dubbed the Sausage , used an extra-large fission bomb as a "trigger" and liquid deuterium—kept in its liquid state by 20 short tons (18 t ) of cryogenic equipment—as its fusion fuel, and weighed around 80 short tons (73 t ) altogether. The liquid deuterium fuel of Ivy Mike
17835-537: The Teller–Ulam design was apparently independent, but it was allowed to share in some US fallout data which may have been useful. After the successful detonation of a megaton-range device and thus its practical understanding of the Teller–Ulam design "secret," the United States agreed to exchange some of its nuclear designs with the United Kingdom, which led to the 1958 US-UK Mutual Defence Agreement . The People's Republic of China detonated its first device using
18040-435: The U.S. and Soviets, achieving only approximately 300 kt (1,300 TJ). The second test Orange Herald was the modified fission bomb and produced 720 kt (3,000 TJ)—making it the largest fission explosion ever. At the time almost everyone (including the pilots of the plane that dropped it) thought that this was a fusion bomb. This bomb was put into service in 1958. A second prototype fusion bomb, Purple Granite ,
18245-409: The US design was much better than theirs, and he decided that they must have exploded a separate fission bomb and somehow used its energy to compress the lithium deuteride. He then turned his focus to finding a way for an explosion to one side to be used to compress the ball of fusion fuel within 5% of symmetry, which he realised could be achieved by focusing the X-rays. The Soviet Union demonstrated
18450-522: The United States is known as the Teller–Ulam configuration for its two chief contributors, Edward Teller and Stanisław Ulam , who developed it in 1951 for the United States, with certain concepts developed with the contribution of physicist John von Neumann . Similar devices were developed by the Soviet Union, United Kingdom, France, China and India. The thermonuclear Tsar Bomba was the most powerful bomb ever detonated. As thermonuclear weapons represent
18655-460: The United States, such knowledge can by default be classified as " Restricted Data ", even if it is created by persons who are not government employees or associated with weapons programs, in a legal doctrine known as " born secret " (though the constitutional standing of the doctrine has been at times called into question; see United States v. Progressive, Inc. ). Born secret is rarely invoked for cases of private speculation. The official policy of
18860-507: The United States, though some were later developed independently by other states. In early news accounts, pure fission weapons were called atomic bombs or A-bombs and weapons involving fusion were called hydrogen bombs or H-bombs . Practitioners of nuclear policy, however, favor the terms nuclear and thermonuclear, respectively. Nuclear fission separates or splits heavier atoms to form lighter atoms. Nuclear fusion combines lighter atoms to form heavier atoms. Both reactions generate roughly
19065-524: The accuracy of the supposed leaked information. Aside from images of the warhead casing but never of the " physics package " itself, most information in the public domain about the design is relegated to a few terse statements and the work of a few individual investigators. Here is a short discussion of the events that led to the formation of the "public" models of the Teller–Ulam design, with some discussions as to their differences and disagreements with those principles outlined above. The general principles of
19270-411: The amount of chemical explosives needed. The first Sloika design test, RDS-6s , was detonated in 1953 with a yield equivalent to 400 kt (1,700 TJ) ( 15%- 20% from fusion). Attempts to use a Sloika design to achieve megaton-range results proved unfeasible. After the United States tested the "Ivy Mike" thermonuclear device in November 1952, proving that a multimegaton bomb could be created,
19475-472: The atoll and Japanese fishermen on board the Daigo Fukuryu Maru . After an initial period focused on making multi-megaton hydrogen bombs, efforts in the United States shifted towards developing miniaturized Teller–Ulam weapons which could outfit Intercontinental Ballistic Missiles and Submarine Launched Ballistic Missiles . The last major design breakthrough in this respect was accomplished by
19680-428: The bare-metal critical mass (see Little Boy article for a detailed drawing) . When assembled inside its tamper/reflector of tungsten carbide , the 64 kg (141 lb) was more than twice critical mass. Before the detonation, the uranium-235 was formed into two sub-critical pieces, one of which was later fired down a gun barrel to join the other, starting the nuclear explosion. Analysis shows that less than 2% of
19885-411: The barrel of a much larger gun). Such warheads were deployed by the United States until 1992, accounting for a significant fraction of the U in the arsenal , and were some of the first weapons dismantled to comply with treaties limiting warhead numbers. The rationale for this decision was undoubtedly a combination of the lower yield and grave safety issues associated with the gun-type design. For both
20090-420: The best weapon-grade uranium contains a significant number of U nuclei. These are susceptible to spontaneous fission events, which occur randomly (it is a quantum mechanical phenomenon). Because the fissile material in a gun-assembled critical mass is not compressed, the design need only ensure the two sub-critical masses remain close enough to each other long enough that a U spontaneous fission will occur while
20295-488: The bomb might weigh between 250 and 360 kg (550 and 790 lb). The Teller–Ulam design was for many years considered one of the top nuclear secrets, and even today, it is not discussed in any detail by official publications with origins "behind the fence" of classification . The policy of the US Department of Energy (DOE) has always been not to acknowledge when "leaks" occur since doing such would acknowledge
20500-437: The bomb of the number of fission events needed to attain the full design yield. Additionally, heat resulting from the fissions that do occur would work against the continued assembly of the supercritical mass, from thermal expansion of the fuel. This failure is called predetonation . The resulting explosion would be called a "fizzle" by bomb engineers and weapon users. Plutonium's high rate of spontaneous fission makes uranium fuel
20705-456: The bomb's fissile pit and tamper until their kinetic energy is converted into heat . Given the speed of the fragments and the mean free path between nuclei in the compressed fuel assembly (for the implosion design), this takes about a millionth of a second (a microsecond), by which time the core and tamper of the bomb have expanded to a ball of plasma several meters in diameter with a temperature of tens of millions of degrees Celsius. This
20910-404: The bomb's power is the initiation of subsequent fissions. Over half of the neutrons escape the bomb core, but the rest strike U nuclei causing them to fission in an exponentially growing chain reaction (1, 2, 4, 8, 16, etc.). Starting from one atom, the number of fissions can theoretically double a hundred times in a microsecond, which could consume all uranium or plutonium up to hundreds of tons by
21115-451: The bomb, which would, by the bombardment by neutrons, produce tritium . In late 1953, physicist Viktor Davidenko achieved the first breakthrough, that of keeping the primary and the secondary parts of the bombs in separate pieces ("staging"). The next breakthrough was discovered and developed by Sakharov and Yakov Zeldovich , that of using the X-rays from the fission bomb to compress
21320-480: The casing to a plasma, which then re-radiated radiation into the secondary's pusher, causing its surface to ablate and driving it inwards, compressing the secondary, igniting the sparkplug, and causing the fusion reaction. The general applicability of this principle is unclear. In 1999 a reporter for the San Jose Mercury News reported that the U.S. W88 nuclear warhead, a small MIRVed warhead used on
21525-440: The casing's circumference. The neutron guns are tilted so the neutron emitting end of each gun end is pointed towards the central axis of the bomb. Neutrons from each neutron gun pass through and are focused by the neutron focus lens towards the centre of primary in order to boost the initial fissioning of the plutonium. A " polystyrene Polarizer/Plasma Source" is also shown (see below). The first U.S. government document to mention
21730-412: The conditions needed for fusion, and the idea of staging or placing a separate thermonuclear component outside a fission primary component, and somehow using the primary to compress the secondary. Teller then realized that the gamma and X-ray radiation produced in the primary could transfer enough energy into the secondary to create a successful implosion and fusion burn, if the whole assembly was wrapped in
21935-404: The cores of boosted fission devices in order to increase their energy yields. This is especially so for the fission primaries of thermonuclear weapons. The second way is indirect, and takes advantage of the fact that the neutrons emitted by a supercritical fission "spark plug" in the secondary assembly of a two-stage thermonuclear bomb will produce tritium in situ when these neutrons collide with
22140-462: The coulomb barrier of these impurity nuclei and undergo a reaction that yields a free neutron. The rate of alpha emission of fissile nuclei is one to two million times that of spontaneous fission, so weapon engineers are careful to use fuel of high purity. Fission weapons used in the vicinity of other nuclear explosions must be protected from the intrusion of free neutrons from outside. Such shielding material will almost always be penetrated, however, if
22345-420: The current ideas of the Teller–Ulam design came into public awareness after the DOE attempted to censor a magazine article by the anti-weapons activist Howard Morland in 1979 on the "secret of the hydrogen bomb." In 1978, Morland had decided that discovering and exposing the "last remaining secret" would focus attention onto the arms race and allow citizens to feel empowered to question official statements on
22550-522: The danger of its accidentally becoming supercritical becomes too great. Surrounding the other components is a hohlraum or radiation case , a container that traps the first stage or primary's energy inside temporarily. The outside of this radiation case, which is also normally the outside casing of the bomb, is the only direct visual evidence publicly available of any thermonuclear bomb component's configuration. Numerous photographs of various thermonuclear bomb exteriors have been declassified. The primary
22755-412: The decision to go forward with the development of the new weapon. Teller and other U.S. physicists struggled to find a workable design. Stanislaw Ulam , a co-worker of Teller, made the first key conceptual leaps towards a workable fusion design. Ulam's two innovations that rendered the fusion bomb practical were that compression of the thermonuclear fuel before extreme heating was a practical path towards
22960-403: The design impressed many scientists, to the point that some who previously wondered if it were feasible suddenly believed it was inevitable and that it would be created by both the US and the Soviet Union. Even Oppenheimer, who was originally opposed to the project, called the idea "technically sweet." The "George" shot of Operation Greenhouse in 1951 tested the basic concept for the first time on
23165-445: The design might yield a single megaton of energy if it was pushed to its limits. After the US tested the "Ivy Mike" device in 1952, proving that a multimegaton bomb could be created, the Soviet Union searched for an additional design and continued to work on improving the Sloika (the "First Idea"). The "Second Idea", as Sakharov referred to it in his memoirs, was a previous proposal by Ginzburg in November 1948 to use lithium deuteride in
23370-486: The development of a fission bomb held at the University of California, Berkeley , where he guided discussion towards the idea of creating his "Super" bomb, which would hypothetically be many times more powerful than the yet-undeveloped fission weapon. Teller assumed creating the fission bomb would be nothing more than an engineering problem, and that the "Super" provided a much more interesting theoretical challenge. For
23575-424: The diagram, though details are almost absent; what scattered details it does include likely have intentional omissions or inaccuracies. They are labeled "End-cap and Neutron Focus Lens" and "Reflector Wrap"; the former channels neutrons to the U / Pu Spark Plug while the latter refers to an X-ray reflector; typically a cylinder made of an X-ray opaque material such as uranium with
23780-401: The edges of the shaper where it is diffracted around the edges into the main mass of explosive. This causes the detonation to form into a ring that proceeds inward from the shaper. Due to the lack of a tamper or lenses to shape the progression, the detonation does not reach the pit in a spherical shape. To produce the desired spherical implosion, the fissile material itself is shaped to produce
23985-414: The effects of that absorbed energy led to the third mechanism: ablation . The outer casing of the secondary assembly is called the "tamper-pusher". The purpose of a tamper in an implosion bomb is to delay the expansion of the reacting fuel supply (which is very hot dense plasma) until the fuel is fully consumed and the explosion runs to completion. The same tamper material serves also as a pusher in that it
24190-421: The energy carried by the fusion neutrons. In the case of a neutron bomb (see below), the last-mentioned factor does not apply, since the objective is to facilitate the escape of neutrons, rather than to use them to increase the weapon's raw power. An essential nuclear reaction is the one that creates tritium , or hydrogen-3. Tritium is employed in two ways. First, pure tritium gas is produced for placement inside
24395-529: The energy from a fission device to begin a fusion reaction was first proposed by the Italian physicist Enrico Fermi to his colleague Edward Teller in the fall of 1941 during what would soon become the Manhattan Project , the World War II effort by the United States and United Kingdom to develop the first nuclear weapons . Teller soon was a participant at Robert Oppenheimer 's 1942 summer conference on
24600-511: The energy of the explosions into a "pancake" area is far more efficient in terms of area-destruction per unit of bomb energy. This also applies to single bombs deliverable by cruise missile or other system, such as a bomber, resulting in most operational warheads in the U.S. program having yields of less than 500 kt (2,100 TJ). In his 1995 book Dark Sun: The Making of the Hydrogen Bomb , author Richard Rhodes describes in detail
24805-522: The entire secondary stage and drives up the density of the plutonium spark plug. The density of the plutonium fuel rises to such an extent that the spark plug is driven into a supercritical state, and it begins a nuclear fission chain reaction . The fission products of this chain reaction heat the highly compressed (and thus super dense) thermonuclear fuel surrounding the spark plug to around 300 million kelvin, igniting fusion reactions between fusion fuel nuclei. In modern weapons fueled by lithium deuteride,
25010-447: The escape or capture of neutrons. To avoid a premature chain reaction during handling, the fissile material in the weapon must be kept subcritical. It may consist of one or more components containing less than one uncompressed critical mass each. A thin hollow shell can have more than the bare-sphere critical mass, as can a cylinder, which can be arbitrarily long without ever reaching criticality. Another method of reducing criticality risk
25215-528: The explosion processes. A tamper is an optional layer of dense material surrounding the fissile material. Due to its inertia it delays the thermal expansion of the fissioning fuel mass, keeping it supercritical for longer. Often the same layer serves both as tamper and as neutron reflector. Little Boy , the Hiroshima bomb, used 64 kg (141 lb) of uranium with an average enrichment of around 80%, or 51 kg (112 lb) of uranium-235, just about
25420-414: The exponential function by which neutron multiplication evolves. The critical mass of an uncompressed sphere of bare metal is 50 kg (110 lb) for uranium-235 and 16 kg (35 lb) for delta-phase plutonium-239. In practical applications, the amount of material required for criticality is modified by shape, purity, density, and the proximity to neutron-reflecting material , all of which affect
25625-515: The far more powerful Super. The debate covered matters that were alternatively strategic, pragmatic, and moral. In their Report of the General Advisory Committee, Robert Oppenheimer and colleagues concluded that "[t]he extreme danger to mankind inherent in the proposal [to develop thermonuclear weapons] wholly outweighs any military advantage." Despite the objections raised, on 31 January 1950, President Harry S. Truman made
25830-428: The far-more-powerful Super. On January 31, 1950, US President Harry S. Truman ordered a program to develop a hydrogen bomb. Many scientists returned to Los Alamos to work on the "Super" program, but the initial attempts still seemed highly unworkable. In the "classical Super," it was thought that the heat alone from the fission bomb would be used to ignite the fusion material, but that proved to be impossible. For
26035-504: The fission primary was being kept separate from the fusion secondary , a key part of the Teller–Ulam device, and perhaps that the fusion fuel had been subjected to high amounts of compression before detonation. One of the key Soviet bomb designers, Yuli Khariton , later said: At that time, Soviet research was not organized on a sufficiently high level, and useful results were not obtained, although radiochemical analyses of samples of fallout could have provided some useful information about
26240-455: The fission "trigger" (in a spherical formation) or at the heart of it (similar to a "boosted" weapon) in the hopes that the closer the fuel was to the fission explosion, the higher the chance it would ignite the fusion fuel by the sheer force of the heat generated. In 1951, after many years of fruitless labor on the "Super", a breakthrough idea from the Polish émigré mathematician Stanislaw Ulam
26445-432: The fissioning of the final natural uranium tamper, something that could not normally be achieved without the neutron flux provided by the fusion reactions in secondary or tertiary stages. Such designs are suggested to be capable of being scaled up to an arbitrary large yield (with apparently as many fusion stages as desired), potentially to the level of a " doomsday device ." However, usually such weapons were not more than
26650-434: The fissioning plutonium spark plug also emits free neutrons that collide with lithium nuclei and supply the tritium component of the thermonuclear fuel. The secondary's relatively massive tamper (which resists outward expansion as the explosion proceeds) also serves as a thermal barrier to keep the fusion fuel filler from becoming too hot, which would spoil the compression. If made of uranium , enriched uranium or plutonium,
26855-503: The gap between the Neutron Focus Lens (in the center) and the outer casing near the primary. It separates the primary from the secondary and performs the same function as the previous reflector. There are about six neutron guns (seen here from Sandia National Laboratories ) each protruding through the outer edge of the reflector with one end in each section; all are clamped to the carriage and arranged more or less evenly around
27060-564: The hundredth link in the chain. Typically in a modern weapon, the weapon's pit contains 3.5 to 4.5 kilograms (7.7 to 9.9 lb) of plutonium and at detonation produces approximately 5 to 10 kilotonnes of TNT (21 to 42 TJ) yield, representing the fissioning of approximately 0.5 kilograms (1.1 lb) of plutonium. Materials which can sustain a chain reaction are called fissile . The two fissile materials used in nuclear weapons are: U, also known as highly enriched uranium (HEU), "oralloy" meaning "Oak Ridge alloy", or "25" (a combination of
27265-537: The idea of Ulam. The nuclear weapons designer Ted Taylor was clear about assigning credit for the basic staging and compression ideas to Ulam, while giving Teller the credit for recognizing the critical role of radiation as opposed to hydrodynamic pressure. Priscilla Johnson McMillan in her book The Ruin of J. Robert Oppenheimer: And the Birth of the Modern Arms Race , writes that Teller sought to "conceal
27470-478: The importance of nuclear weapons and nuclear secrecy. Most of Morland's ideas about how the weapon worked were compiled from highly-accessible sources; the drawings that most inspired his approach came from the Encyclopedia Americana . Morland also interviewed, often informally, many former Los Alamos scientists (including Teller and Ulam, though neither gave him any useful information), and used
27675-462: The intensities seen in everyday life, such as sunlight striking a surface, is usually imperceptible, but at the extreme intensities found in a thermonuclear bomb the pressure is enormous. For two thermonuclear bombs for which the general size and primary characteristics are well understood, the Ivy Mike test bomb and the modern W-80 cruise missile warhead variant of the W-61 design, the radiation pressure
27880-420: The internal components of the "Ivy Mike" Sausage device, based on information obtained from extensive interviews with the scientists and engineers who assembled it. According to Rhodes, the actual mechanism for the compression of the secondary was a combination of the radiation pressure, foam plasma pressure, and tamper-pusher ablation theories; the radiation from the primary heated the polyethylene foam lining of
28085-503: The interstage was only recently released to the public promoting the 2004 initiation of the Reliable Replacement Warhead (RRW) Program. A graphic includes blurbs describing the potential advantage of a RRW on a part-by-part level, with the interstage blurb saying a new design would replace "toxic, brittle material" and "expensive 'special' material... [that require] unique facilities". The "toxic, brittle material"
28290-424: The last digit of the atomic number of uranium-235, which is 92, and the last digit of its mass number, which is 235); and Pu, also known as plutonium-239, or "49" (from "94" and "239"). Uranium's most common isotope , U, is fissionable but not fissile, meaning that it cannot sustain a chain reaction because its daughter fission neutrons are not (on average) energetic enough to cause follow-on U fissions. However,
28495-523: The last year of the project he was assigned exclusively to the task. However once World War II ended, there was little impetus to devote many resources to the Super , as it was then known. The first atomic bomb test by the Soviet Union in August 1949 came earlier than expected by Americans, and over the next several months there was an intense debate within the U.S. government, military, and scientific communities regarding whether to proceed with development of
28700-413: The layer of fuel is the " spark plug ", a hollow column of fissile material ( Pu or U ) often boosted by deuterium gas. The spark plug, when compressed, can undergo nuclear fission (because of the shape, it is not a critical mass without compression). The tertiary, if one is present, would be set below the secondary and probably be made of the same materials. Separating
28905-407: The less-dense fuel mass. Each following fission event in the chain approximately doubles the neutron population (net, after losses due to some neutrons escaping the fuel mass, and others that collide with any non-fuel impurity nuclei present). For the gun assembly method (see below) of supercritical mass formation, the fuel itself can be relied upon to initiate the chain reaction. This is because even
29110-441: The lithium nuclei have been transmuted to tritium. Of the four basic types of nuclear weapon, the first, pure fission, uses the first of the three nuclear reactions above. The second, fusion-boosted fission, uses the first two. The third, two-stage thermonuclear, uses all three. The first task of a nuclear weapon design is to rapidly assemble a supercritical mass of fissile (weapon grade) uranium or plutonium. A supercritical mass
29315-454: The lithium nuclei in the bomb's lithium deuteride fuel supply. Elemental gaseous tritium for fission primaries is also made by bombarding lithium-6 ( Li) with neutrons (n), only in a nuclear reactor. This neutron bombardment will cause the lithium-6 nucleus to split, producing an alpha particle, or helium -4 ( He), plus a triton ( T) and energy: But as was discovered in the first test of this type of device, Castle Bravo , when lithium-7
29520-431: The low direct plasma pressure they may be of use in delaying the ablation until energy has distributed evenly and a sufficient fraction has reached the secondary's tamper/pusher. Richard Rhodes ' book Dark Sun stated that a 1-inch-thick (25 mm) layer of plastic foam was fixed to the lead liner of the inside of the Ivy Mike steel casing using copper nails. Rhodes quotes several designers of that bomb explaining that
29725-472: The low yields was that radioactivity released from yields significantly more than 45 kilotons might not have been contained fully. Even low-yield tests can have a bearing on thermonuclear capability, as they can provide information on the behavior of primaries without the full ignition of secondaries . North Korea claimed to have tested its miniaturised thermonuclear bomb on January 6, 2016. North Korea's first three nuclear tests (2006, 2009 and 2013) had
29930-535: The materials used to produce the explosion. The relationship between certain short-lived isotopes formed in the course of thermonuclear reactions could have made it possible to judge the degree of compression of the thermonuclear fuel, but knowing the degree of compression would not have allowed Soviet scientists to conclude exactly how the exploded device had been made, and it would not have revealed its design. Sakharov stated in his memoirs that though he and Davidenko had fallout dust in cardboard boxes several days after
30135-533: The mid-1970s, when versions of the Teller–Ulam design were created which could fit on the end of a small MIRVed missile. In the Soviet Union , the scientists working on their own hydrogen bomb project also ran into difficulties in developing a megaton-range fusion weapon. Because Klaus Fuchs had only been at Los Alamos at a very early stage of the hydrogen bomb design (before the Teller–Ulam configuration had been completed), none of his espionage information
30340-511: The most efficient design for weapon energy yield in weapons with yields above 50 kilotons of TNT (210 TJ), 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. Detailed knowledge of fission and fusion weapons is classified to some degree in virtually every industrialized country . In
30545-463: The necessity to assemble the supercritical mass of fuel very rapidly. The time required to accomplish this is called the weapon's critical insertion time . If spontaneous fission were to occur when the supercritical mass was only partially assembled, the chain reaction would begin prematurely. Neutron losses through the void between the two subcritical masses (gun assembly) or the voids between not-fully-compressed fuel nuclei (implosion assembly) would sap
30750-436: The neutrons inside a massive bottle of heavy material such as lead, uranium, or plutonium. If the 14 MeV neutron is captured by uranium (of either isotope; 14 MeV is high enough to fission both U and U) or plutonium, the result is fission and the release of 180 MeV of fission energy, multiplying the energy output tenfold. For weapon use, fission is necessary to start fusion, helps to sustain fusion, and captures and multiplies
30955-454: The neutrons released by fusion of the heavy hydrogen isotopes deuterium and tritium will fission U. This U fission reaction in the outer jacket of the secondary assembly of a two-stage thermonuclear bomb produces by far the greatest fraction of the bomb's energy yield, as well as most of its radioactive debris. For national powers engaged in a nuclear arms race, this fact of U's ability to fast-fission from thermonuclear neutron bombardment
31160-402: The nuclear fuel is cast into a solid shape and placed within the center of a cylinder of high explosive. Detonators are placed at either end of the explosive cylinder, and a plate-like insert, or shaper , is placed in the explosive just inside the detonators. When the detonators are fired, the initial detonation is trapped between the shaper and the end of the cylinder, causing it to travel out to
31365-424: The outer radiation case, with the components coming to a thermal equilibrium , and the effects of that thermal energy are then analyzed. The energy is mostly deposited within about one X-ray optical thickness of the tamper/pusher outer surface, and the temperature of that layer can then be calculated. The velocity at which the surface then expands outwards is calculated and, from a basic Newtonian momentum balance,
31570-403: The outside neutron flux is intense enough. When a weapon misfires or fizzles because of the effects of other nuclear detonations, it is called nuclear fratricide . For the implosion-assembled design, once the critical mass is assembled to maximum density, a burst of neutrons must be supplied to start the chain reaction. Early weapons used a modulated neutron generator code named " Urchin " inside
31775-511: The pit containing polonium -210 and beryllium separated by a thin barrier. Implosion of the pit crushes the neutron generator, mixing the two metals, thereby allowing alpha particles from the polonium to interact with beryllium to produce free neutrons. In modern weapons, the neutron generator is a high-voltage vacuum tube containing a particle accelerator which bombards a deuterium/tritium-metal hydride target with deuterium and tritium ions . The resulting small-scale fusion produces neutrons at
31980-438: The plastic foam layer inside the outer case is to delay ablation and thus recoil of the outer case: if the foam were not there, metal would ablate from the inside of the outer case with a large impulse, causing the casing to recoil outwards rapidly. The purpose of the casing is to contain the explosion for as long as possible, allowing as much X-ray ablation of the metallic surface of the secondary stage as possible, so it compresses
32185-510: The power of the "staging" concept in October 1961 when they detonated the massive and unwieldy Tsar Bomba , a 50 Mt (210 PJ) hydrogen bomb which derived almost 97% of its energy from fusion rather than fission—its uranium tamper was replaced with one of lead shortly before firing, in an effort to prevent excessive nuclear fallout. Had it been fired in its "full" form, it would have yielded at around 100 Mt (420 PJ). The weapon
32390-460: The press as the "father of the hydrogen bomb", a title which he did not seek to discourage. Many of Teller's colleagues were irritated that he seemed to enjoy taking full credit for something he had only a part in, and in response, with encouragement from Enrico Fermi, Teller authored an article titled "The Work of Many People," which appeared in Science magazine in February 1955, emphasizing that he
32595-413: The pressure produced by such a plasma would only be a small multiplier of the basic photon pressure within the radiation case, and also that the known foam materials intrinsically have a very low absorption efficiency of the gamma ray and X-ray radiation from the primary. Most of the energy produced would be absorbed by either the walls of the radiation case or the tamper around the secondary. Analyzing
32800-441: The primary and secondary at either end. It does not reflect like a mirror; instead, it gets heated to a high temperature by the X-ray flux from the primary, then it emits more evenly spread X-rays that travel to the secondary, causing what is known as radiation implosion . In Ivy Mike , gold was used as a coating over the uranium to enhance the blackbody effect. Next comes the "Reflector/Neutron Gun Carriage". The reflector seals
33005-421: The primary would be used to compress and ignite the secondary fusion stage, resulting in a fusion explosion many times more powerful than the fission explosion alone. This chain of compression could conceivably be continued with an arbitrary number of tertiary fusion stages, each igniting more fusion fuel in the next stage although this is debated. Finally, efficient bombs (but not so-called neutron bombs ) end with
33210-511: The proceedings of the appeals trial, as a short erratum in The Progressive a month later. In 1981, Morland published a book, The secret that exploded , about his experience, describing in detail the train of thought which led him to his conclusions about the "secret." Because the DOE sought to censor Morland's work, one of the few times that it violated its usual approach of not acknowledging "secret" material that had been released, it
33415-538: The radioactive products are the nuclear waste in spent fuel . In bombs, they become radioactive fallout, both local and global. Meanwhile, inside the exploding bomb, the free neutrons released by fission carry away about 3% of the initial fission energy. Neutron kinetic energy adds to the blast energy of a bomb, but not as effectively as the energy from charged fragments, since neutrons do not give up their kinetic energy as quickly in collisions with charged nuclei or electrons. The dominant contribution of fission neutrons to
33620-404: The remainder of the war the effort was focused on first developing fission weapons. Nevertheless, Teller continued to pursue the "Super", to the point of neglecting work assigned to him for the fission weapon at the secret Los Alamos lab where he worked. (Much of the work Teller declined to do was given instead to Klaus Fuchs , who was later discovered to be a spy for the Soviet Union . ) Teller
33825-418: The rest of the tamper-pusher to recoil inwards with tremendous force, crushing the fusion fuel and the spark plug. The tamper-pusher is built robustly enough to insulate the fusion fuel from the extreme heat outside; otherwise, the compression would be spoiled. Rough calculations for the basic ablation effect are relatively simple: the energy from the primary is distributed evenly onto all of the surfaces within
34030-400: The role" of Ulam, and that only "radiation implosion" was Teller's idea. Teller went as far as refusing to sign the patent application because it would need Ulam's signature. Thomas Powers writes that "of course the bomb designers all knew the truth, and many considered Teller the lowest, most contemptible kind of offender in the world of science, a stealer of credit". Teller became known in
34235-412: The same effect. Due to the physics of the shock wave propagation within the explosive mass, this requires the pit to be a prolate spheroid , that is, roughly egg shaped. The shock wave first reaches the pit at its tips, driving them inward and causing the mass to become spherical. The shock may also change plutonium from delta to alpha phase, increasing its density by 23%, but without the inward momentum of
34440-449: The secondary efficiently, maximizing the fusion yield. Plastic foam has a low density, so causes a smaller impulse when it ablates than metal does. Possible variations to the weapon design have been proposed: Most bombs do not apparently have tertiary "stages"—that is, third compression stage(s), which are additional fusion stages compressed by a previous fusion stage. The fissioning of the last blanket of uranium, which provides about half
34645-422: The secondary from the primary is the interstage . The fissioning primary produces four types of energy: 1) expanding hot gases from high explosive charges that implode the primary; 2) superheated plasma that was originally the bomb's fissile material and its tamper; 3) the electromagnetic radiation ; and 4) the neutrons from the primary's nuclear detonation. The interstage is responsible for accurately modulating
34850-592: The secondary stages by radiation implosion. Because of these difficulties, in 1955 Prime Minister Anthony Eden agreed to a secret plan, whereby if the Aldermaston scientists failed or were greatly delayed in developing the fusion bomb, it would be replaced by an extremely large fission bomb. In 1957 the Operation Grapple tests were carried out. The first test, Green Granite, was a prototype fusion bomb that failed to produce equivalent yields compared to
35055-416: The severing of the strong nuclear force holding the mutually-repulsive protons together), plus two or three free neutrons. These race away and collide with neighboring fuel nuclei. This process repeats over and over until the fuel assembly goes sub-critical (from thermal expansion), after which the chain reaction shuts down because the daughter neutrons can no longer find new fuel nuclei to hit before escaping
35260-497: The shock wave backward, thereby having the effect of lengthening its duration. It is made out of a low density metal – such as aluminium , beryllium , or an alloy of the two metals (aluminium is easier and safer to shape, and is two orders of magnitude cheaper; beryllium has high neutron-reflective capability). Fat Man used an aluminium pusher. The series of RaLa Experiment tests of implosion-type fission weapon design concepts, carried out from July 1944 through February 1945 at
35465-471: The statements vindicate some or all of the models presented above is up for interpretation, and official US government releases about the technical details of nuclear weapons have been purposely equivocating in the past (such as the Smyth Report ). Other information, such as the types of fuel used in some of the early weapons, has been declassified, but precise technical information has not been. Most of
35670-494: The supercritical assembly. Most of these have the speed (kinetic energy) required to cause new fissions in neighboring uranium nuclei. The uranium-235 nucleus can split in many ways, provided the atomic numbers add up to 92 and the mass numbers add up to 236 (uranium-235 plus the neutron that caused the split). The following equation shows one possible split, namely into strontium-95 ( Sr), xenon-139 ( Xe), and two neutrons (n), plus energy: The immediate energy release per atom
35875-422: The supercritical mass of fuel nuclei. This process is conceived and described colloquially as the nuclear chain reaction . To start the chain reaction in a supercritical assembly, at least one free neutron must be injected and collide with a fissile fuel nucleus. The neutron joins with the nucleus (technically a fusion event) and destabilizes the nucleus, which explodes into two middleweight nuclear fragments (from
36080-468: The tamper and the pit to create a hammer-on-nail impact. The pit, supported on a hollow cone inside the tamper cavity, was said to be "levitated". The three tests of Operation Sandstone , in 1948, used Fat Man designs with levitated pits. The largest yield was 49 kilotons, more than twice the yield of the unlevitated Fat Man. It was immediately clear that implosion was the best design for a fission weapon. Its only drawback seemed to be its diameter. Fat Man
36285-401: The tamper captures fast fusion neutrons and undergoes fission itself, increasing the overall explosive yield . Additionally, in most designs the radiation case is also constructed of a material that undergoes fission driven by fast thermonuclear neutrons. Such bombs are classified as two stage weapons. Fast fission of the tamper and radiation case is the main contribution to the total yield and
36490-410: The time of the test, a similar magnitude to the 2013 test of a 6–9 kt atomic bomb. Those seismic recordings have scientists worldwide doubting North Korea's claim that a hydrogen bomb was tested and suggest it was a non-fusion nuclear test. On September 9, 2016, North Korea conducted their fifth nuclear test which yielded between 10 and 30 kilotons. On September 3, 2017, North Korea conducted
36695-422: The total yield from fission by fast neutrons). After the chain reaction started in the plutonium, it continued until the explosion reversed the momentum of the implosion and expanded enough to stop the chain reaction. By holding everything together for a few hundred nanoseconds more, the tamper increased the efficiency. The core of an implosion weapon – the fissile material and any reflector or tamper bonded to it –
36900-404: The transfer of energy from the primary to the secondary. It must direct the hot gases, plasma, electromagnetic radiation and neutrons toward the right place at the right time. Less than optimal interstage designs have resulted in the secondary failing to work entirely on multiple shots, known as a " fissile fizzle ". The Castle Koon shot of Operation Castle is a good example; a small flaw allowed
37105-406: The two assemblies ensures that debris fragments from the fission primary (which move much more slowly than X-ray photons ) cannot disassemble the secondary before the fusion explosion runs to completion. The secondary fusion stage—consisting of outer pusher/ tamper , fusion fuel filler and central plutonium spark plug—is imploded by the X-ray energy impinging on its pusher/ tamper. This compresses
37310-481: The uranium mass underwent fission; the remainder, representing most of the entire wartime output of the giant Y-12 factories at Oak Ridge, scattered uselessly. The inefficiency was caused by the speed with which the uncompressed fissioning uranium expanded and became sub-critical by virtue of decreased density. Despite its inefficiency, this design, because of its shape, was adapted for use in small-diameter, cylindrical artillery shells (a gun-type warhead fired from
37515-412: The velocity at which the rest of the tamper implodes inwards. Applying the more detailed form of those calculations to the Ivy Mike device yields vaporized pusher gas expansion velocity of 290 kilometres per second (29 cm/μs) and an implosion velocity of perhaps 400 km/s (40 cm/μs) if + 3 ⁄ 4 of the total tamper/pusher mass is ablated off, the most energy efficient proportion. For
37720-404: The weapon (with the foam) would be as follows: This would complete the fission-fusion-fission sequence. Fusion, unlike fission, is relatively "clean"—it releases energy but no harmful radioactive products or large amounts of nuclear fallout . The fission reactions though, especially the last fission reactions, release a tremendous amount of fission products and fallout. If the last fission stage
37925-438: The weapon is in the vicinity of the target. This is not difficult to arrange as it takes but a second or two in a typical-size fuel mass for this to occur. (Still, many such bombs meant for delivery by air (gravity bomb, artillery shell or rocket) use injected neutrons to gain finer control over the exact detonation altitude, important for the destructive effectiveness of airbursts.) This condition of spontaneous fission highlights
38130-449: The weapon's main fuel, thus allowing more efficient use of scarce fissile material such as uranium-235 ( U ) or plutonium-239 ( Pu ). The first full-scale thermonuclear test ( Ivy Mike ) was carried out by the United States in 1952, and the concept has since been employed by most of the world's nuclear powers in the design of their weapons. Modern fusion weapons essentially consist of two main components:
38335-478: The weapon, including Teller and Berkeley physicists Ernest Lawrence and Luis Alvarez , argued that such a development was inevitable, and to deny such protection to the people of the United States—especially when the Soviet Union was likely to create such a weapon itself—was itself an immoral and unwise act. Still others, such as Oppenheimer, simply thought that the existing stockpile of fissile material
38540-498: The yield in large bombs, does not count as a "stage" in this terminology. The U.S. tested three-stage bombs in several explosions during Operation Redwing but is thought to have fielded only one such tertiary model, i.e., a bomb in which a fission stage, followed by a fusion stage, finally compresses yet another fusion stage. This U.S. design was the heavy but highly efficient (i.e., nuclear weapon yield per unit bomb weight) 25 Mt (100 PJ) B41 nuclear bomb . The Soviet Union
38745-433: The yields of the Indian tests concur with those of India. Indian scientists have argued that some international estimations of the yields of India's nuclear tests are unscientific. India says that the yield of its tests were deliberately kept low to avoid civilian damage and that it can build staged thermonuclear weapons of various yields up to around 200 kilotons on the basis of those tests. Another cited reason for
38950-410: Was 1.5 metres (5 ft) wide vs 61 centimetres (2 ft) for Little Boy. The Pu-239 pit of Fat Man was only 9.1 centimetres (3.6 in) in diameter, the size of a softball. The bulk of Fat Man's girth was the implosion mechanism, namely concentric layers of U-238, aluminium, and high explosives. The key to reducing that girth was the two-point implosion design. In the two-point linear implosion,
39155-413: Was better spent in attempting to develop a large arsenal of tactical atomic weapons rather than potentially squandered on the development of a few massive "Supers". In any case, work slowed greatly at Los Alamos, as some 5,500 of the 7,100 scientists and related staff who had been there at the conclusion of the war left to go back to their previous positions at universities and laboratories. A conference
39360-483: Was calculated to be 73 × 10 ^ bar (7.3 TPa ) for the Ivy Mike design and 1,400 × 10 ^ bar (140 TPa ) for the W-80. Foam plasma pressure is the concept that Chuck Hansen introduced during the Progressive case, based on research that located declassified documents listing special foams as liner components within the radiation case of thermonuclear weapons. The sequence of firing
39565-431: Was calculated to be ultimately not worth the effort and no prototype was ever developed or tested. Attempts to use a Sloika design to achieve megaton-range results proved unfeasible in the Soviet Union as it had in the calculations done in the US, but its value as a practical weapon since it was 20 times more powerful than their first fission bomb, should not be underestimated. The Soviet physicists calculated that at best
39770-413: Was cut off by the United States at one point due to concerns about Soviet espionage. Full cooperation was not reestablished until an agreement governing the handling of secret information and other issues was signed. However, the British were allowed to observe the U.S. Castle tests and used sampling aircraft in the mushroom clouds , providing them with clear, direct evidence of the compression produced in
39975-549: Was discovered and developed by Sakharov and Yakov Zel'dovich in early 1954. Sakharov's "Third Idea", as the Teller–Ulam design was known in the USSR, was tested in the shot " RDS-37 " in November 1955 with a yield of 1.6 Mt (6.7 PJ). The Soviets demonstrated the power of the staging concept in October 1961, when they detonated the massive and unwieldy Tsar Bomba. It was the largest nuclear weapon developed and tested by any country. In 1954 work began at Aldermaston to develop
40180-537: Was given some resources with which to study the "Super", and contacted his friend Maria Göppert-Mayer to help with laborious calculations relating to opacity . The "Super", however, proved elusive, and the calculations were incredibly difficult to perform, especially since there was no existing way to run small-scale tests of the principles involved (in comparison, the properties of fission could be more easily probed with cyclotrons , newly created nuclear reactors , and various other tests). Even though they had witnessed
40385-510: Was held at Los Alamos in 1946 to examine the feasibility of building a Super; it concluded that it was feasible, but there were a number of dissenters to that conclusion. When the Soviet Union exploded their own atomic bomb (dubbed " Joe 1 " by the US) in August 1949, it caught Western analysts off guard, and over the next several months there was an intense debate within the US government, military, and scientific communities on whether to proceed with
40590-509: Was impractical for a deployable weapon, and the next advance was to use a solid lithium deuteride fusion fuel instead. In 1954 this was tested in the " Castle Bravo " shot (the device was code-named Shrimp ), which had a yield of 15 Mt (63 PJ ) (2.5 times expected) and is the largest U.S. bomb ever tested. Efforts shifted towards developing miniaturized Teller–Ulam weapons that could fit into intercontinental ballistic missiles and submarine-launched ballistic missiles . By 1960, with
40795-412: Was later dubbed Sakharov's "First Idea"). Though nuclear fusion was technically achieved, it did not have the scaling property of a staged weapon, and their first hydrogen bomb test, Joe 4 , is considered a hybrid fission/fusion device more similar to a large boosted fission weapon than a Teller–Ulam weapon (though using an order of magnitude more fusion fuel than a boosted weapon). Detonated in 1953 with
41000-405: Was moot, dropped its suit, and allowed the magazine to publish, which it did in November 1979. Morland had by then, however, changed his opinion of how the bomb worked to suggesting that a foam medium (the polystyrene) rather than radiation pressure was used to compress the secondary and that in the secondary was a sparkplug of fissile material as well. He published the changes, based in part on
41205-412: Was not alone in the weapon's development (he would later write in his memoirs that he had told a "white lie" in the 1955 article, and would imply that he should receive full credit for the weapon's invention). Hans Bethe, who also participated in the hydrogen bomb project, once said, "For the sake of history, I think it is more precise to say that Ulam is the father, because he provided the seed, and Teller
41410-484: Was of much use, and the Soviet physicists working on the project had to develop their weapon independently. The first Soviet fusion design, developed by Andrei Sakharov and Vitaly Ginzburg in 1949 (before the Soviet Union had a working fission bomb), was dubbed the Sloika , after a Russian layered puff pastry, and was not of the Teller–Ulam configuration, but rather used alternating layers of fissile material and lithium deuteride fusion fuel spiked with tritium (this
41615-420: Was seized upon by Teller and developed into the first workable design for a megaton-range hydrogen bomb. This concept, now called "staged implosion" was first proposed in a classified scientific paper, On Heterocatalytic Detonations I. Hydrodynamic Lenses and Radiation Mirrors by Teller and Ulam on March 9, 1951. The exact amount of contribution provided respectively from Ulam and Teller to what became known as
41820-731: Was technically deployable (it was tested by dropping it from a specially modified bomber), but militarily impractical, and was developed and tested primarily as a show of Soviet strength. It is the largest nuclear weapon developed and tested by any country. The details of the development of the Teller–Ulam design in other countries are less well known. In any event, the United Kingdom initially had difficulty in its development of it and failed in its first attempt in May 1957 (its " Grapple I " test failed to ignite as planned, but much of its energy came from fusion in its secondary). However, it succeeded in its second attempt in its November 1957 " Grapple X " test, which yielded 1.8 Mt. The British development of
42025-504: Was used in the third test, but only produced approximately 150 kt (630 TJ). Nuclear weapon design Pure fission weapons 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. Most known innovations in nuclear weapon design originated in
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