Plutonium-240 ( Pu or Pu-240 ) is an isotope of plutonium formed when plutonium-239 captures a neutron . The detection of its spontaneous fission led to its discovery in 1944 at Los Alamos and had important consequences for the Manhattan Project .
94-424: Pu undergoes spontaneous fission as a secondary decay mode at a small but significant rate. The presence of Pu limits plutonium's use in a nuclear bomb , because the neutron flux from spontaneous fission initiates the chain reaction prematurely, causing an early release of energy that physically disperses the core before full implosion is reached. It decays by alpha emission to uranium-236 . About 62% to 73% of
188-513: A misnomer , as their energy comes from the nucleus of the atom, just as it does with fusion weapons. In fission weapons, a mass of fissile material ( enriched uranium or plutonium ) is forced into supercriticality —allowing an exponential growth of nuclear chain reactions —either by shooting one piece of sub-critical material into another (the "gun" method) or by compression of a sub-critical sphere or cylinder of fissile material using chemically fueled explosive lenses . The latter approach,
282-651: A policy of deliberate ambiguity , it does not acknowledge having them. Germany , Italy , Turkey , Belgium , the Netherlands , and Belarus are nuclear weapons sharing states. South Africa is the only country to have independently developed and then renounced and dismantled its nuclear weapons. The Treaty on the Non-Proliferation of Nuclear Weapons aims to reduce the spread of nuclear weapons, but there are different views of its effectiveness. There are two basic types of nuclear weapons: those that derive
376-597: A combination of fission and fusion reactions ( thermonuclear bomb ), producing a nuclear explosion . Both bomb types release large quantities of energy from relatively small amounts of matter . The first test of a fission ("atomic") bomb released an amount of energy approximately equal to 20,000 tons of TNT (84 TJ ). The first thermonuclear ("hydrogen") bomb test released energy approximately equal to 10 million tons of TNT (42 PJ). Nuclear bombs have had yields between 10 tons TNT (the W54 ) and 50 megatons for
470-678: A conference—called for in the manifesto—in Pugwash, Nova Scotia , Eaton's birthplace. This conference was to be the first of the Pugwash Conferences on Science and World Affairs , held in July 1957. By the 1960s, steps were taken to limit both the proliferation of nuclear weapons to other countries and the environmental effects of nuclear testing . The Partial Nuclear Test Ban Treaty (1963) restricted all nuclear testing to underground nuclear testing , to prevent contamination from nuclear fallout, whereas
564-458: A faster and less vulnerable attack, the development of long-range intercontinental ballistic missiles (ICBMs) and submarine-launched ballistic missiles (SLBMs) has given some nations the ability to plausibly deliver missiles anywhere on the globe with a high likelihood of success. More advanced systems, such as multiple independently targetable reentry vehicles (MIRVs), can launch multiple warheads at different targets from one missile, reducing
658-594: A few nations possess such weapons or are suspected of seeking them. The only countries known to have detonated nuclear weapons—and acknowledge possessing them—are (chronologically by date of first test) the United States , the Soviet Union (succeeded as a nuclear power by Russia ), the United Kingdom , France , China , India , Pakistan , and North Korea . Israel is believed to possess nuclear weapons, though, in
752-538: A fission bomb to initiate them. Such a device might provide a simpler path to thermonuclear weapons than one that required the development of fission weapons first, and pure fusion weapons would create significantly less nuclear fallout than other thermonuclear weapons because they would not disperse fission products. In 1998, the United States Department of Energy divulged that the United States had, "...made
846-421: A fusion weapon as of January 2016 , though this claim is disputed. Thermonuclear weapons are considered much more difficult to successfully design and execute than primitive fission weapons. Almost all of the nuclear weapons deployed today use the thermonuclear design because it results in an explosion hundreds of times stronger than that of a fission bomb of similar weight. Thermonuclear bombs work by using
940-458: A millisecond to complete, and made it necessary to develop implosion-style weapons where the assembly occurs in a few microseconds. Even with this design, it was estimated in advance of the Trinity test that Pu impurity would cause a 12% chance of the explosion failing to reach its maximum yield. The minimization of the amount of Pu , as in weapons-grade plutonium (less than 7% Pu)
1034-472: A nation's economic electronics-based infrastructure. Because the effect is most effectively produced by high altitude nuclear detonations (by military weapons delivered by air, though ground bursts also produce EMP effects over a localized area), it can produce damage to electronics over a wide, even continental, geographical area. Research has been done into the possibility of pure fusion bombs : nuclear weapons that consist of fusion reactions without requiring
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#17328521043781128-532: A new nuclear strategy, one that is distinct from that which gave relative stability during the Cold War. Since 1996, the United States has had a policy of allowing the targeting of its nuclear weapons at terrorists armed with weapons of mass destruction . Robert Gallucci argues that although traditional deterrence is not an effective approach toward terrorist groups bent on causing a nuclear catastrophe, Gallucci believes that "the United States should instead consider
1222-425: A nuclear war between two nations would result in mutual annihilation. From this point of view, the significance of nuclear weapons is to deter war because any nuclear war would escalate out of mutual distrust and fear, resulting in mutually assured destruction . This threat of national, if not global, destruction has been a strong motivation for anti-nuclear weapons activism. Critics from the peace movement and within
1316-411: A nuclear weapon from another country by threatening nuclear retaliation is known as the strategy of nuclear deterrence . The goal in deterrence is to always maintain a second strike capability (the ability of a country to respond to a nuclear attack with one of its own) and potentially to strive for first strike status (the ability to destroy an enemy's nuclear forces before they could retaliate). During
1410-465: A nuclear weapon is a gravity bomb dropped from aircraft ; this was the method used by the United States against Japan in 1945. This method places few restrictions on the size of the weapon. It does, however, limit attack range, response time to an impending attack, and the number of weapons that a country can field at the same time. With miniaturization, nuclear bombs can be delivered by both strategic bombers and tactical fighter-bombers . This method
1504-409: A nuclear weapon to its target is an important factor affecting both nuclear weapon design and nuclear strategy . The design, development, and maintenance of delivery systems are among the most expensive parts of a nuclear weapons program; they account, for example, for 57% of the financial resources spent by the United States on nuclear weapons projects since 1940. The simplest method for delivering
1598-433: A nuclear weapon with suitable materials (such as cobalt or gold ) creates a weapon known as a salted bomb . This device can produce exceptionally large quantities of long-lived radioactive contamination . It has been conjectured that such a device could serve as a "doomsday weapon" because such a large quantity of radioactivities with half-lives of decades, lifted into the stratosphere where winds would distribute it around
1692-482: A plutonium-based nuclear warhead core complicates its design, and pure Pu is considered optimal. This is for a few reasons: The spontaneous fission problem was extensively studied by the scientists of the Manhattan Project during World War II . It blocked the use of plutonium in gun-type nuclear weapons in which the assembly of fissile material into its optimal supercritical mass configuration can take up to
1786-421: A policy of expanded deterrence, which focuses not solely on the would-be nuclear terrorists but on those states that may deliberately transfer or inadvertently leak nuclear weapons and materials to them. By threatening retaliation against those states, the United States may be able to deter that which it cannot physically prevent.". Graham Allison makes a similar case, arguing that the key to expanded deterrence
1880-447: A significant portion of their energy from fission reactions used to "trigger" fusion reactions, and fusion reactions can themselves trigger additional fission reactions. Only six countries—the United States , Russia , the United Kingdom , China , France , and India —have conducted thermonuclear weapon tests. Whether India has detonated a "true" multi-staged thermonuclear weapon is controversial. North Korea claims to have tested
1974-478: A sphere are A = 4 π r 2 {\displaystyle A=4\pi r^{2}} and V = 4 3 π r 3 {\displaystyle V={\frac {4}{3}}\pi r^{3}} respectively. The blast wave, however, was likely assumed to grow out as the surface area of the approximately hemispheric near surface burst blast wave of the Trinity gadget. The paper
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#17328521043782068-547: A substantial investment" in the past to develop pure fusion weapons, but that, "The U.S. does not have and is not developing a pure fusion weapon", and that, "No credible design for a pure fusion weapon resulted from the DOE investment". Nuclear isomers provide a possible pathway to fissionless fusion bombs. These are naturally occurring isotopes ( Hf being a prominent example) which exist in an elevated energy state. Mechanisms to release this energy as bursts of gamma radiation (as in
2162-420: Is a thermonuclear weapon that yields a relatively small explosion but a relatively large amount of neutron radiation . Such a weapon could, according to tacticians, be used to cause massive biological casualties while leaving inanimate infrastructure mostly intact and creating minimal fallout. Because high energy neutrons are capable of penetrating dense matter, such as tank armor, neutron warheads were procured in
2256-430: Is achieved by reprocessing the fuel after just 90 days of use. Such rapid fuel cycles are highly impractical for civilian power reactors and are normally only carried out with dedicated weapons plutonium production reactors. Plutonium from spent civilian power reactor fuel typically has under 70% Pu and around 26% Pu , the rest being made up of other plutonium isotopes, making it more difficult to use it for
2350-451: Is analogous to identifying a criminal by fingerprints. "The goal would be twofold: first, to deter leaders of nuclear states from selling weapons to terrorists by holding them accountable for any use of their weapons; second, to give leaders every incentive to tightly secure their nuclear weapons and materials." According to the Pentagon's June 2019 " Doctrine for Joint Nuclear Operations " of
2444-403: Is coming up with ways of tracing nuclear material to the country that forged the fissile material. "After a nuclear bomb detonates, nuclear forensics cops would collect debris samples and send them to a laboratory for radiological analysis. By identifying unique attributes of the fissile material, including its impurities and contaminants, one could trace the path back to its origin." The process
2538-430: Is detonated , usually expressed as a TNT equivalent (the standardized equivalent mass of trinitrotoluene which, if detonated, would produce the same energy discharge), either in kilotonnes (kt—thousands of tonnes of TNT), in megatonnes (Mt—millions of tonnes of TNT), or sometimes in terajoules (TJ). An explosive yield of one terajoule is equal to 0.239 kilotonnes of TNT . Because the accuracy of any measurement of
2632-576: Is estimated to have been between 12 and 18 kilotonnes of TNT (50 and 75 TJ) (a 20% margin of error), while the Nagasaki bomb, " Fat Man ", is estimated to be between 18 and 23 kilotonnes of TNT (75 and 96 TJ) (a 10% margin of error). Such apparently small changes in values can be important when trying to use the data from these bombings as reflective of how other bombs would behave in combat, and also result in differing assessments of how many "Hiroshima bombs" other weapons are equivalent to (for example,
2726-481: Is for the purpose of achieving different yields for different situations , and in manipulating design elements to attempt to minimize weapon size, radiation hardness or requirements for special materials, especially fissile fuel or tritium. Some nuclear weapons are designed for special purposes; most of these are for non-strategic (decisively war-winning) purposes and are referred to as tactical nuclear weapons . The neutron bomb purportedly conceived by Sam Cohen
2820-469: Is moved 2.5 meters by the wave, so the effect of the Trinity device is to displace a hemispherical shell of air of volume 2.5 m × 2π(16 km) . Multiply by 1 atm to get an energy of 4.1 × 10 J ~ 100 kT TNT. A good approximation of the yield of the Trinity test device was obtained in 1950 by the British physicist G. I. Taylor from simple dimensional analysis and an estimation of
2914-498: Is no evidence that it is feasible beyond the military domain. However, the U.S. Air Force funded studies of the physics of antimatter in the Cold War , and began considering its possible use in weapons, not just as a trigger, but as the explosive itself. A fourth generation nuclear weapon design is related to, and relies upon, the same principle as antimatter-catalyzed nuclear pulse propulsion . Most variation in nuclear weapon design
Plutonium-240 - Misplaced Pages Continue
3008-409: Is not a fusion bomb. In the boosted bomb, the neutrons produced by the fusion reactions serve primarily to increase the efficiency of the fission bomb. There are two types of boosted fission bomb: internally boosted, in which a deuterium-tritium mixture is injected into the bomb core, and externally boosted, in which concentric shells of lithium-deuteride and depleted uranium are layered on the outside of
3102-490: Is not clear that this has ever been implemented, and their plausible use in nuclear weapons is a matter of dispute. The other basic type of nuclear weapon produces a large proportion of its energy in nuclear fusion reactions. Such fusion weapons are generally referred to as thermonuclear weapons or more colloquially as hydrogen bombs (abbreviated as H-bombs ), as they rely on fusion reactions between isotopes of hydrogen ( deuterium and tritium ). All such weapons derive
3196-451: Is the primary means of nuclear weapons delivery; the majority of U.S. nuclear warheads, for example, are free-fall gravity bombs, namely the B61 , which is being improved upon to this day. Preferable from a strategic point of view is a nuclear weapon mounted on a missile , which can use a ballistic trajectory to deliver the warhead over the horizon. Although even short-range missiles allow for
3290-495: The Ivy Mike hydrogen bomb was equivalent to either 867 or 578 Hiroshima weapons — a rhetorically quite substantial difference — depending on whether one uses the high or low figure for the calculation). Other disputed yields have included the massive Tsar Bomba , whose yield was claimed between being "only" 50 megatonnes of TNT (210 PJ) or at a maximum of 57 megatonnes of TNT (240 PJ) by differing political figures, either as
3384-540: The Oklahoma City bombing , using a truck-based fertilizer bomb, was 0.002 kt. The estimated strength of the explosion at the Port of Beirut is 0.3-0.5 kt. Most artificial non-nuclear explosions are considerably smaller than even what are considered to be very small nuclear weapons. The yield-to-mass ratio is the amount of weapon yield compared to the mass of the weapon. The highest achieved values are somewhat lower, and
3478-688: The Starfish Prime high-altitude nuclear test in 1962, an unexpected effect was produced which is called a nuclear electromagnetic pulse . This is an intense flash of electromagnetic energy produced by a rain of high-energy electrons which in turn are produced by a nuclear bomb's gamma rays. This flash of energy can permanently destroy or disrupt electronic equipment if insufficiently shielded. It has been proposed to use this effect to disable an enemy's military and civilian infrastructure as an adjunct to other nuclear or conventional military operations. By itself it could as well be useful to terrorists for crippling
3572-528: The Treaty on the Non-Proliferation of Nuclear Weapons (1968) attempted to place restrictions on the types of activities signatories could participate in, with the goal of allowing the transference of non-military nuclear technology to member countries without fear of proliferation. Nuclear weapon yield The explosive yield of a nuclear weapon is the amount of energy released such as blast, thermal, and nuclear radiation, when that particular nuclear weapon
3666-450: The Trinity test by dropping small pieces of paper in the air and measuring how far they were moved by the blast wave of the explosion; that is, he found the blast pressure at his distance from the detonation in pounds per square inch , using the deviation of the papers' fall away from the vertical as a crude blast gauge/barograph , and then with pressure X in psi, at distance Y , in miles figures, he extrapolated backwards to estimate
3760-548: The Tsar Bomba (see TNT equivalent ). A thermonuclear weapon weighing as little as 600 pounds (270 kg) can release energy equal to more than 1.2 megatonnes of TNT (5.0 PJ). A nuclear device no larger than a conventional bomb can devastate an entire city by blast, fire, and radiation . Since they are weapons of mass destruction , the proliferation of nuclear weapons is a focus of international relations policy. Nuclear weapons have been deployed twice in war , both by
3854-663: The Tsar Bomba of the USSR, which released an energy equivalent of over 50 megatons of TNT (210 PJ), was a three-stage weapon. Most thermonuclear weapons are considerably smaller than this, due to practical constraints from missile warhead space and weight requirements. In the early 1950s the Livermore Laboratory in the United States had plans for the testing of two massive bombs, Gnomon and Sundial , 1 gigaton of TNT and 10 gigatons of TNT respectively. Fusion reactions do not create fission products, and thus contribute far less to
Plutonium-240 - Misplaced Pages Continue
3948-424: The hafnium controversy ) have been proposed as possible triggers for conventional thermonuclear reactions. Antimatter , which consists of particles resembling ordinary matter particles in most of their properties but having opposite electric charge , has been considered as a trigger mechanism for nuclear weapons. A major obstacle is the difficulty of producing antimatter in large enough quantities, and there
4042-599: The head of government or head of state . Despite controls and regulations governing nuclear weapons, there is an inherent danger of "accidents, mistakes, false alarms, blackmail, theft, and sabotage". In the late 1940s, lack of mutual trust prevented the United States and the Soviet Union from making progress on arms control agreements. The Russell–Einstein Manifesto was issued in London on July 9, 1955, by Bertrand Russell in
4136-436: The tropopause into the stratosphere , where the calm non-turbulent winds permit the debris to travel great distances from the burst, eventually settling and unpredictably contaminating areas far removed from the target of the explosion. There are other types of nuclear weapons as well. For example, a boosted fission weapon is a fission bomb that increases its explosive yield through a small number of fusion reactions, but it
4230-537: The "implosion" method, is more sophisticated and more efficient (smaller, less massive, and requiring less of the expensive fissile fuel) than the former. A major challenge in all nuclear weapon designs is to ensure that a significant fraction of the fuel is consumed before the weapon destroys itself. The amount of energy released by fission bombs can range from the equivalent of just under a ton to upwards of 500,000 tons (500 kilotons ) of TNT (4.2 to 2.1 × 10 GJ). All fission reactions generate fission products ,
4324-578: The 1980s (though not deployed in Europe) for use as tactical payloads for US Army artillery shells (200 mm W79 and 155 mm W82 ) and short range missile forces. Soviet authorities announced similar intentions for neutron warhead deployment in Europe; indeed, they claimed to have originally invented the neutron bomb, but their deployment on USSR tactical nuclear forces is unverifiable. A type of nuclear explosive most suitable for use by ground special forces
4418-425: The Cold War, policy and military theorists considered the sorts of policies that might prevent a nuclear attack, and they developed game theory models that could lead to stable deterrence conditions. Different forms of nuclear weapons delivery (see above) allow for different types of nuclear strategies. The goals of any strategy are generally to make it difficult for an enemy to launch a pre-emptive strike against
4512-488: The Joint Chiefs of Staffs website Publication, "Integration of nuclear weapons employment with conventional and special operations forces is essential to the success of any mission or operation." Because they are weapons of mass destruction, the proliferation and possible use of nuclear weapons are important issues in international relations and diplomacy. In most countries, the use of nuclear force can only be authorized by
4606-497: The Nuclear Age (1961) that mere possession of a nuclear arsenal was enough to ensure deterrence, and thus concluded that the spread of nuclear weapons could increase international stability . Some prominent neo-realist scholars, such as Kenneth Waltz and John Mearsheimer , have argued, along the lines of Gallois, that some forms of nuclear proliferation would decrease the likelihood of total war , especially in troubled regions of
4700-448: The U.S. government and published in Life magazine), using successive frames of the explosion, Taylor found that R / t is a constant in a given nuclear blast (especially between 0.38 ms, after the shock wave has formed, and 1.93 ms, before significant energy is lost by thermal radiation). Furthermore, he estimated a value for S numerically at 1. Thus, with t = 0.025 s and
4794-651: The USAAF detonated a plutonium implosion-type fission bomb nicknamed " Fat Man " over the Japanese city of Nagasaki . These bombings caused injuries that resulted in the deaths of approximately 200,000 civilians and military personnel . The ethics of these bombings and their role in Japan's surrender are to this day, still subjects of debate . Since the atomic bombings of Hiroshima and Nagasaki , nuclear weapons have been detonated over 2,000 times for testing and demonstration. Only
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#17328521043784888-753: The USAF AIR-2 Genie , the AIM-26 Falcon and US Army Nike Hercules . Missile interceptors such as the Sprint and the Spartan also used small nuclear warheads (optimized to produce neutron or X-ray flux) but were for use against enemy strategic warheads. Other small, or tactical, nuclear weapons were deployed by naval forces for use primarily as antisubmarine weapons. These included nuclear depth bombs or nuclear armed torpedoes. Nuclear mines for use on land or at sea are also possibilities. The system used to deliver
4982-515: The United States against the Japanese cities of Hiroshima and Nagasaki in 1945 during World War II . Nuclear weapons have only twice been used in warfare, both times by the United States against Japan at the end of World War II . On August 6, 1945, the United States Army Air Forces (USAAF) detonated a uranium gun-type fission bomb nicknamed " Little Boy " over the Japanese city of Hiroshima ; three days later, on August 9,
5076-512: The United States. Small, two-man portable tactical weapons (somewhat misleadingly referred to as suitcase bombs ), such as the Special Atomic Demolition Munition , have been developed, although the difficulty of combining sufficient yield with portability limits their military utility. Nuclear warfare strategy is a set of policies that deal with preventing or fighting a nuclear war. The policy of trying to prevent an attack by
5170-474: The blast radius being 140 metres, and taking ρ to be 1 kg/m (the measured value at Trinity on the day of the test, as opposed to sea-level values of approximately 1.3 kg/m ) and solving for E , Taylor obtained that the yield was about 22 kilotonnes of TNT (90 TJ). This does not take into account the fact that the energy should only be about half this value for a hemispherical blast, but this very simple argument did agree to within 10% with
5264-485: The chance of a successful missile defense . Today, missiles are most common among systems designed for delivery of nuclear weapons. Making a warhead small enough to fit onto a missile, though, can be difficult. Tactical weapons have involved the most variety of delivery types, including not only gravity bombs and missiles but also artillery shells, land mines , and nuclear depth charges and torpedoes for anti-submarine warfare . An atomic mortar has been tested by
5358-435: The creation of nuclear fallout than fission reactions, but because all thermonuclear weapons contain at least one fission stage, and many high-yield thermonuclear devices have a final fission stage, thermonuclear weapons can generate at least as much nuclear fallout as fission-only weapons. Furthermore, high yield thermonuclear explosions (most dangerously ground bursts) have the force to lift radioactive debris upwards past
5452-450: The decision process. The prospect of mutually assured destruction might not deter an enemy who expects to die in the confrontation. Further, if the initial act is from a stateless terrorist instead of a sovereign nation, there might not be a nation or specific target to retaliate against. It has been argued, especially after the September 11, 2001, attacks , that this complication calls for
5546-420: The design. A tamper is typically made of uranium and it holds the core together using its inertia. It is used to prevent the core from separating too soon to generate maximum fission, so as not to cause a "fizzle". The initiator is a source of neutrons either inside of the core, or on the outside of the bomb, and in this case it shoots neutrons at the core at the moment of detonation. It is essentially kick starting
5640-492: The early 1960s. Since then, the smaller warheads needed to achieve the increased net damage efficiency (bomb damage/bomb mass) of multiple warhead systems have resulted in increases in the yield/mass ratio for single modern warheads. In order of increasing yield (most yield figures are approximate): In comparison, the blast yield of the GBU-43 Massive Ordnance Air Blast bomb is 0.011 kt, and that of
5734-463: The energy of a fission bomb to compress and heat fusion fuel. In the Teller-Ulam design , which accounts for all multi-megaton yield hydrogen bombs, this is accomplished by placing a fission bomb and fusion fuel ( tritium , deuterium , or lithium deuteride ) in proximity within a special, radiation-reflecting container. When the fission bomb is detonated, gamma rays and X-rays emitted first compress
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#17328521043785828-547: The energy released by TNT has always been problematic, the conventional definition is that one kilotonne of TNT is held simply to be equivalent to 10 calories . The yield-to-weight ratio is the amount of weapon yield compared to the mass of the weapon. The practical maximum yield-to-weight ratio for fusion weapons ( thermonuclear weapons ) has been estimated to six megatonnes of TNT per tonne of bomb mass (25 TJ/kg). Yields of 5.2 megatonnes/tonne and higher have been reported for large weapons constructed for single-warhead use in
5922-426: The fact that destructive power of a single warhead on land scales approximately only as the cube root of its yield, due to blast "wasted" over a roughly hemispherical blast volume, while the strategic target is distributed over a circular land area with limited height and depth. This effect more than makes up for the lessened yield/mass efficiency encountered if ballistic missile warheads are individually scaled down from
6016-451: The fission bomb core. The external method of boosting enabled the USSR to field the first partially thermonuclear weapons, but it is now obsolete because it demands a spherical bomb geometry, which was adequate during the 1950s arms race when bomber aircraft were the only available delivery vehicles. The detonation of any nuclear weapon is accompanied by a blast of neutron radiation . Surrounding
6110-420: The fusion fuel, then heat it to thermonuclear temperatures. The ensuing fusion reaction creates enormous numbers of high-speed neutrons , which can then induce fission in materials not normally prone to it, such as depleted uranium . Each of these components is known as a "stage", with the fission bomb as the "primary" and the fusion capsule as the "secondary". In large, megaton-range hydrogen bombs, about half of
6204-569: The general relation such that the left and right sides are dimensionally balanced in terms of M , L , and T (i.e., each dimension has the same exponent on both sides). Where these data are not available, as in a number of cases, precise yields have been in dispute, especially when they are tied to questions of politics. The weapons used in the atomic bombings of Hiroshima and Nagasaki , for example, were highly individual and very idiosyncratic designs, and gauging their yield retrospectively has been quite difficult. The Hiroshima bomb, " Little Boy ",
6298-520: The globe, would make all life on the planet extinct. In connection with the Strategic Defense Initiative , research into the nuclear pumped laser was conducted under the DOD program Project Excalibur but this did not result in a working weapon. The concept involves the tapping of the energy of an exploding nuclear bomb to power a single-shot laser that is directed at a distant target. During
6392-405: The heat capacity for very hot air. Taylor had initially done this highly classified work in mid-1941 and published an article with an analysis of the Trinity data fireball when the Trinity photograph data was declassified in 1950 (after the USSR had exploded its own version of this bomb). Taylor noted that the radius R of the blast should initially depend only on the energy E of the explosion,
6486-407: The isotope Pu captures a neutron, it is about 4500 times more likely to become plutonium-241 than to fission. In general, isotopes of odd mass numbers are more likely to absorb a neutron, and can undergo fission upon neutron absorption more easily than isotopes of even mass number. Thus, even mass isotopes tend to accumulate, especially in a thermal reactor . The inevitable presence of some Pu in
6580-429: The kilotonne or megatonne range (much less down to the resolution of individual terajoules ). Even under very controlled conditions, precise yields can be very hard to determine, and for less controlled conditions the margins of error can be quite large. For fission devices, the most precise yield value is found from " radiochemical /Fallout analysis"; that is, measuring the quantity of fission products generated, in much
6674-446: The lower value for very hot diatomic air (1.2), and under conditions of an atomic fireball is (coincidentally) close to the STP (standard) gamma for room-temperature air, which is 1.4. This gives the value of Taylor's S constant to be 1.036 for the adiabatic hypershock region where the constant R / t condition holds. As it relates to fundamental dimensional analysis, if one expresses all
6768-496: The majority of their energy from nuclear fission reactions alone, and those that use fission reactions to begin nuclear fusion reactions that produce a large amount of the total energy output. All existing nuclear weapons derive some of their explosive energy from nuclear fission reactions. Weapons whose explosive output is exclusively from fission reactions are commonly referred to as atomic bombs or atom bombs (abbreviated as A-bombs ). This has long been noted as something of
6862-444: The manufacturing of nuclear weapons. For nuclear weapon designs introduced after the 1940s, however, there has been considerable debate over the degree to which Pu poses a barrier for weapons construction; see the article Reactor-grade plutonium . Nuclear bomb A nuclear weapon is an explosive device that derives its destructive force from nuclear reactions , either fission (fission bomb) or
6956-489: The maximal size that could be carried by a single-warhead missile. The efficiency of an atomic bomb is the ratio of the actual yield to the theoretical maximum yield of the atomic bomb. Not all atomic bombs possess the same yield efficiency as each individual bombs design plays a large role in how efficient it can be. In order to maximize yield efficiency one must make sure to assemble the critical mass correctly, as well as implementing instruments such as tampers or initiators in
7050-407: The midst of the Cold War. It highlighted the dangers posed by nuclear weapons and called for world leaders to seek peaceful resolutions to international conflict. The signatories included eleven pre-eminent intellectuals and scientists, including Albert Einstein , who signed it just days before his death on April 18, 1955. A few days after the release, philanthropist Cyrus S. Eaton offered to sponsor
7144-536: The military establishment have questioned the usefulness of such weapons in the current military climate. According to an advisory opinion issued by the International Court of Justice in 1996, the use of (or threat of use of) such weapons would generally be contrary to the rules of international law applicable in armed conflict, but the court did not reach an opinion as to whether or not the threat or use would be lawful in specific extreme circumstances such as if
7238-408: The missiles before they land or implementing civil defense measures using early-warning systems to evacuate citizens to safe areas before an attack. Weapons designed to threaten large populations or to deter attacks are known as strategic weapons . Nuclear weapons for use on a battlefield in military situations are called tactical weapons . Critics of nuclear war strategy often suggest that
7332-408: The official value of the bomb's yield in 1950, which was 20 kilotons of TNT (84 TJ) (see G. I. Taylor, Proc. Roy. Soc. London A 200 , pp. 235–247 (1950)). A good approximation to Taylor's constant S for γ {\displaystyle \gamma } below about 2 is The value of the heat capacity ratio here is between the 1.67 of fully dissociated air molecules and
7426-431: The passage of the blast wave. Since, at the time, there was no wind[,] I could observe very distinctly and actually measure the displacement of the pieces of paper that were in the process of falling while the blast was passing. The shift was about 2 1/2 meters, which, at the time, I estimated to correspond to the blast that would be produced by ten thousand tonnes of TNT. The surface area (A) and volume (V) of
7520-632: The reaction so the maximum fission reactions can occur to maximize yield. The following list is of milestone nuclear explosions. In addition to the atomic bombings of Hiroshima and Nagasaki , the first nuclear test of a given weapon type for a country is included, as well as tests that were otherwise notable (such as the largest test ever). All yields (explosive power) are given in their estimated energy equivalents in kilotons of TNT (see TNT equivalent ). Putative tests (like Vela incident ) have not been included. Yields of nuclear explosions can be very hard to calculate, even using numbers as rough as in
7614-428: The remains of the split atomic nuclei. Many fission products are either highly radioactive (but short-lived) or moderately radioactive (but long-lived), and as such, they are a serious form of radioactive contamination . Fission products are the principal radioactive component of nuclear fallout . Another source of radioactivity is the burst of free neutrons produced by the weapon. When they collide with other nuclei in
7708-401: The same way as the chemical yield in chemical reaction products can be measured after a chemical reaction . The radiochemical analysis method was pioneered by Herbert L. Anderson . For nuclear explosive devices where the fallout is not attainable or would be misleading , neutron activation analysis is often employed as the second most accurate method, with it having been used to determine
7802-402: The surrounding material, the neutrons transmute those nuclei into other isotopes, altering their stability and making them radioactive. The most commonly used fissile materials for nuclear weapons applications have been uranium-235 and plutonium-239 . Less commonly used has been uranium-233 . Neptunium-237 and some isotopes of americium may be usable for nuclear explosives as well, but it
7896-498: The survival of the state were at stake. Another deterrence position is that nuclear proliferation can be desirable. In this case, it is argued that, unlike conventional weapons, nuclear weapons deter all-out war between states, and they succeeded in doing this during the Cold War between the U.S. and the Soviet Union . In the late 1950s and early 1960s, Gen. Pierre Marie Gallois of France, an adviser to Charles de Gaulle , argued in books like The Balance of Terror: Strategy for
7990-456: The time t after the detonation, and the density ρ of the air. The only equation having compatible dimensions that can be constructed from these quantities is Here S is a dimensionless constant having a value approximately equal to 1, since it is low-order function of the heat capacity ratio or adiabatic index which is approximately 1 for all conditions. Using the picture of the Trinity test shown here (which had been publicly released by
8084-432: The time when Pu captures a neutron , it undergoes fission ; the remainder of the time, it forms Pu. The longer a nuclear fuel element remains in a nuclear reactor , the greater the relative percentage of Pu in the fuel becomes. The isotope Pu has about the same thermal neutron capture cross section as Pu ( 289.5 ± 1.4 vs. 269.3 ± 2.9 barns ), but only a tiny thermal neutron fission cross section (0.064 barns). When
8178-426: The value tends to be lower for smaller, lighter weapons, of the sort that are emphasized in today's arsenals, designed for efficient MIRV use or delivery by cruise missile systems. Large single warheads are seldom a part of today's arsenals, since smaller MIRV warheads, spread out over a pancake-shaped destructive area, are far more destructive for a given total yield, or unit of payload mass. This effect results from
8272-497: The variables in terms of mass M , length L , and time T : (think of the expression for kinetic energy, E = m v 2 / 2 {\displaystyle E=mv^{2}/2} ), and then derive an expression for, say, E , in terms of the other variables, by finding values of α {\displaystyle \alpha } , β {\displaystyle \beta } , and γ {\displaystyle \gamma } in
8366-446: The weapon system and difficult to defend against the delivery of the weapon during a potential conflict. This can mean keeping weapon locations hidden, such as deploying them on submarines or land mobile transporter erector launchers whose locations are difficult to track, or it can mean protecting weapons by burying them in hardened missile silo bunkers. Other components of nuclear strategies included using missile defenses to destroy
8460-631: The world where there exists a single nuclear-weapon state. Aside from the public opinion that opposes proliferation in any form, there are two schools of thought on the matter: those, like Mearsheimer, who favored selective proliferation, and Waltz, who was somewhat more non- interventionist . Interest in proliferation and the stability-instability paradox that it generates continues to this day, with ongoing debate about indigenous Japanese and South Korean nuclear deterrent against North Korea . The threat of potentially suicidal terrorists possessing nuclear weapons (a form of nuclear terrorism ) complicates
8554-624: The yield comes from the final fissioning of depleted uranium. Virtually all thermonuclear weapons deployed today use the "two-stage" design described to the right, but it is possible to add additional fusion stages—each stage igniting a larger amount of fusion fuel in the next stage. This technique can be used to construct thermonuclear weapons of arbitrarily large yield. This is in contrast to fission bombs, which are limited in their explosive power due to criticality danger (premature nuclear chain reaction caused by too-large amounts of pre-assembled fissile fuel). The largest nuclear weapon ever detonated,
8648-408: The yield of both Little Boy and thermonuclear Ivy Mike 's respective yields. Yields can also be inferred in a number of other remote sensing ways, including scaling law calculations based on blast size, infrasound , fireball brightness ( Bhangmeter ), seismographic data ( CTBTO ), and the strength of the shock wave. Enrico Fermi famously made a (very) rough calculation of the yield of
8742-478: The yield of the Trinity device, which he found was about 10 kilotonnes of blast energy. Fermi later recalled: I was stationed at the Base Camp at Trinity in a position about ten miles [16 km] from the site of the explosion... About 40 seconds after the explosion the air blast reached me. I tried to estimate its strength by dropping from about six feet small pieces of paper before, during, and after
8836-744: Was the Special Atomic Demolition Munition , or SADM, sometimes popularly known as a suitcase nuke . This is a nuclear bomb that is man-portable, or at least truck-portable, and though of a relatively small yield (one or two kilotons) is sufficient to destroy important tactical targets such as bridges, dams, tunnels, important military or commercial installations, etc. either behind enemy lines or pre-emptively on friendly territory soon to be overtaken by invading enemy forces. These weapons require plutonium fuel and are particularly "dirty". They also demand especially stringent security precautions in their storage and deployment. Small "tactical" nuclear weapons were deployed for use as antiaircraft weapons. Examples include
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