Nuclear weapon

Term

Shortly after the discovery of radioactivity at the end of the 19th century, it became clear that tremendous amounts of energy are released over long periods of time when radioactive elements decay. Soon speculations arose about the technical and military use of this new kind of energy. The word atomic bomb was coined by H. G. Wells in his 1914 novel The World Set Free, describing a weapon that would use induced radioactivity to cause a long-lasting explosion. The term "atomic bomb" was thus coined two decades before the discovery of nuclear fission, the basis for the nuclear weapons developed since the 1940s, to which the literary term was eventually applied. Wells had dedicated his book to the chemist Frederick Soddy, an associate of the then leading nuclear physicist Ernest Rutherford.

In 1911, Rutherford described with his atomic model the basic structure of atoms consisting of a heavy nucleus and a light shell of electrons. Subsequently, the so-called atomic physical processes, which also include chemical reactions and in which essentially the electron shell is involved, were distinguished from the more energetic processes in the atomic nucleus (such as radioactivity and nuclear fission), which became the subject of nuclear physics. Thus, in more recent technical language, terms such as nuclear weapon or nuclear weapon (to Latin nuclearis 'pertaining to the nucleus') and nuclear power plant are often preferred to atomic bomb and nuclear power plant; at times, however, such usage is considered euphemistic. Even official language continues to use the compounds with atom- in some cases: In Germany, for example, the licensing authorities with technical responsibility for nuclear energy are sometimes called the Atomic Supervisory Authority, there is an Atomic Energy Act, and a predecessor of the Federal Ministry of Education and Research had the title Atomic Ministry. The conventional terms are also common in the language of most other nations, as the name of the International Atomic Energy Agency (IAEA) shows.

The term nuclear bomb initially covered only nuclear weapons based on nuclear fission (fission) (A-bomb), in contrast fusion weapons were called hydrogen bomb (H-bomb); in addition, there are special developments such as the cobalt bomb and the neutron bomb. The terms nuclear weapons and nuclear weapons are generic terms for all types of weapons that exploit energy gains from nuclear reactions.

Beginnings

Generally known for their work in developing nuclear weapons are Robert Oppenheimer and Edward Teller. The first scientist to think seriously about nuclear weapons was probably the Hungarian physicist Leó Szilárd; in September 1933, he considered the possibility of making atomic nuclei undergo an energy-producing chain reaction by bombarding them with neutrons. This idea was still speculative at the time. In 1934, the German chemist Ida Noddack-Tacke suggested "that when heavy nuclei are bombarded with neutrons, these nuclei break up into several larger fragments."

With the discovery of neutron-induced uranium nuclear fission in 1938 by Otto Hahn and Fritz Straßmann and its correct theoretical interpretation by Lise Meitner and her nephew Otto Frisch, the most important theoretical principles and experimental findings were published in 1939, which made nuclear weapons seem possible if fissile uranium was sufficiently available. This possibility was first recognized by the two German-Austrian emigrants Rudolf Peierls and Otto Frisch, who were working at the University of Birmingham. In a secret memorandum written in March 1940, they described theoretical calculations for the construction of a uranium bomb and strongly warned against the possibility of Germany building an atomic bomb. As a result, the British MAUD Commission, which was also kept secret, was set up to recommend research into the construction of an atomic bomb.

Even before the start of World War II on September 1, 1939, the three physicists Leó Szilárd, Albert Einstein and Eugene Wigner, who had emigrated from Germany to the United States, sent a letter in August 1939 to the then U.S. President Franklin D. Roosevelt to warn him of the possibility of Germany developing an atomic bomb and to encourage him to develop his own. In the fall of 1940, Enrico Fermi and Szilárd received money to begin developing a nuclear reactor. When the success of this work convinced the U.S. government that the development of an atomic bomb was possible in principle and that Germany, the enemy in the war, possessed this capability, research was stepped up and eventually led to the Manhattan Project.

German nuclear fission project

In Nazi Germany during World War II, scientists such as Werner Heisenberg, Carl Friedrich von Weizsäcker, Walther Gerlach, Kurt Diebner, and Otto Hahn, among others, worked on harnessing nuclear fission to achieve German war aims as part of the German Uranium Project.

The fear of the USA that Germany could thus develop its own nuclear explosive device was an important reason to initiate its own atomic bomb program. It was suspected that several research groups, spread over the territory of the German Reich and working partly independently of each other, were working on the development of a German nuclear weapon until the end of the war. After the war, however, it was determined that no nuclear weapons were developed in the Uranium Project. In the last large-scale experiment, the Haigerloch research reactor, Heisenberg's research group had not even succeeded in producing a critical nuclear chain reaction in 1945.

However, there are also researches which speak about secret tests of the research group around Kurt Diebner with radiating material in connection with explosions. This is doubted by many physicists and so far no evidence for the execution of such tests could be produced.

Manhattan Project

In 1942, under the code name "Project Y" (as part of the Manhattan Project), the Los Alamos research laboratory in the US state of New Mexico was conceived under the greatest secrecy. From 1943 on, several thousand people, many of them scientists and technicians, worked there under the scientific direction of Robert Oppenheimer.

On July 16, 1945, the first atomic bomb was detonated above ground near Alamogordo (Trinity test). The nuclear fuel used in the bomb was plutonium and had an explosive force of 21 kilotons TNT equivalent.

Because of Germany's surrender in early May 1945, 2½ months before the Trinity test, no atomic bomb was used in Germany. The first and so far only air raids with atomic bombs were flown against the Japanese cities of Hiroshima and Nagasaki on August 6 and 9, 1945.

Deployment against Hiroshima and Nagasaki

On August 6, 1945, 21 days after the first successful test at Alamogordo, the bomber Enola Gay dropped the first atomic bomb (explosive: uranium-235), called Little Boy, over the coastal city of Hiroshima, where it detonated about 600 m above the ground at 08:15 local time. About 90,000 people died immediately, and another 50,000 people died of radiation sickness within days to weeks.

On August 9, 1945, the bomber Bockscar was to drop the second atomic bomb (explosive: plutonium-239), called Fat Man, over Kokura. When visibility there was still poor after three approaches and fuel was running low, the commander switched to the alternative target, the coastal city of Nagasaki. Since the cloud cover there was also too dense, the city center was missed by several kilometers. Moreover, because the city area is hillier than Hiroshima's, which hindered the spread of the blast wave, there were fewer casualties there - although Fat Man's explosive power was a little more than 50% more powerful than Little Boy's. Nevertheless, 36,000 people died immediately in this attack; another 40,000 people were so badly irradiated that they died within days to weeks.

For a long time, it was assumed that tens of thousands more people had died over the course of years and decades from late effects of radiation exposure. Studies from Germany, the USA and Japan have corrected these estimates significantly downwards: according to them, slightly more than 700 deaths can be attributed to nuclear contamination.

The significance and necessity of the atomic bomb missions remain controversial to this day. Proponents have argued that the use reduced the duration of the war and thus saved the lives of millions of people. Others have argued that atomic bomb use was ethically indefensible; the war would have ended in short order even without atomic bomb use had there been alternatives that were discarded, not used, or not considered.

Development after the Second World War

For three years, the U.S. was the only country to have operational nuclear weapons and conducted tests with them, for example, under water. In 1948, they possessed about 50 operational warheads. In view of their military inferiority to the Soviet Union in conventional terms, a massive nuclear retaliatory strike against the USSR was designed for the first time in early 1948 in the "Halfmoon" plan, which initially envisaged 133 atomic bombs on 70 Soviet cities, but soon after in a reduced version the existing 50 atomic bombs on 20 Soviet cities.

Meanwhile, Great Britain and the Soviet Union were working on their own atomic bombs. The Soviet Union was informed of the atomic bomb program by Klaus Fuchs during World War II. The Soviet atomic bomb project led to the successful detonation of its own first atomic bomb on August 29, 1949, which Britain did not achieve until October 2, 1952, and France on February 13, 1960. In 1962, Britain allowed the U.S. to conduct the Dominic test series on Kiritimati Christmas Island in the Pacific. The People's Republic of China detonated a first nuclear bomb at the Lop Nor nuclear weapons test site in the Xinjiang Autonomous Region on October 16, 1964. This nuclear weapon was developed using Soviet technology.

Soldiers' testimonies; test subjects in nuclear weapons testing.

The adjacent picture shows an American troop test with soldiers at a short distance from the atomic explosion in 1951 in the USA; it documents the partly careless, partly ignorant handling of radioactivity at that time.

About 20,000 British soldiers were also moved, without being informed in more detail, to test sites in Australia (12 tests), Kiritimati (6 tests), and Malden Island (3 tests).

The soldiers, most of whom were young, were instructed to protect their eyes with their hands or elbows during the tests. The soldiers, who witnessed those tests and are referred to as Atomic Veterans, reported the explosions as incomparably frightening experiences. They reported that the radiation released was so glaring and penetrating that the blood vessels and bones of their own hands and arms were visible through their skin. They said the ensuing heat wave from the blast felt like body-penetrating fire. The blast wave had also indirectly caused bruises and broken bones as soldiers were thrown away by the shock wave. Almost all of the soldiers used in the tests suffered physical and psychological damage. Some soldiers were sterile after the tests; overall, a much higher infant mortality rate and more frequent deformities were observed in the soldiers' offspring. Many of those veterans became chronically ill and had various forms of cancer. According to reports, for almost all of those who were present during those tests, long-term damage was a factor in their subsequent deaths.

Development of the hydrogen bomb

Further development of nuclear weapons led to the hydrogen bomb. The USA detonated its first hydrogen bomb (code name Ivy Mike) on October 31/November 1, 1952. It released 10.4 megatons of TNT equivalent energy, 800 times that of the Hiroshima bomb.

The Soviet Union detonated its first hydrogen bomb on August 12, 1953, at the Semipalatinsk nuclear weapons test site. It detonated its first transportable H-bomb on November 22, 1955. The United States first tested a thermonuclear hydrogen bomb based on the Teller-Ulam design during Operation Redwing (May 4-July 21, 1956) on May 20, 1956. On October 30, 1961, the Soviet Union detonated the Tsar bomb on Novaya Zemlya Island, the most powerful nuclear weapon ever detonated at 57 MT.

Britain detonated its first hydrogen bomb in 1957 (Operation Grapple), China detonated its first on June 17, 1967, at the Lop Nor Test Site (Test No. 6), and France detonated its first on August 24, 1968, at Fangataufa Atoll (Canopus).

The UK joined the ban on atmospheric nuclear weapons testing in 1962. Thereafter, all tests were conducted underground in cooperation with the USA at the Nevada Test Site (24 tests), most recently in 1991. In total, the UK conducted 45 tests.

Development after the Cold War

After the disintegration of the Soviet Union at the beginning of the 1990s, experts doubted the military sense of nuclear weapons, since any target could also be destroyed with conventional weapons of the desired size. The greatest danger of nuclear armament, they said, was use by terrorists, because they could cause great damage with little effort if nuclear weapons were used; nuclear weapons, on the other hand, were completely unsuitable in the fight against terrorism.

Regardless of this development, the USA and Russia, as the successor state to the Soviet Union, remained the states with the most nuclear weapons. Their arsenal continues to be maintained; it received less and less public attention after the end of the Cold War.

The development of such small nuclear weapons has been judged by experts to be a danger because their use would hardly cause a stir. Instead of destroyed cities and thousands of dead, the world public would only see a small crater. As a consequence, the inhibition threshold to use nuclear weapons and to wage wars in this way at comparatively low cost - without losing one's own soldiers and without too negative an image - would fall. This would also call into question the Nuclear Non-Proliferation Treaty, which could have unforeseeable consequences (treaty abrogation).

The technical development of nuclear weapons since the 1940s has produced a wide variety of different variants. Basically, a distinction is made between atomic bombs based on the nuclear fission or fission principle ("classical" atomic bomb) and those based on the nuclear fusion principle (hydrogen or H-bomb).

In a fission bomb, a supercritical mass of fissile material is brought together to trigger it. How high this mass is depends on the material, geometry and design. The smallest critical mass can be achieved with a spherical shape of fissile material, the most common being uranium-235 or plutonium-239. Supercriticality leads to a nuclear fission chain reaction with a rapidly increasing nuclear reaction rate. The energy thus released causes the material to vaporize explosively.

In the fusion bomb, a nuclear fission bomb is first detonated. The pressures and temperatures thus generated inside the bomb are sufficient to ignite the fusion reaction with the ^6Li it contains. With the deuterium present and the tritium produced in the aforementioned reaction, the thermonuclear reaction gets underway.

Several different systems have been developed to detonate atomic bombs, i.e., to set the nuclear fission process in motion.

Gun design

The simplest principle is to use a conventional explosive charge to fire a nuclear explosive body, which is subcritical on its own, at a second body, which is also subcritical, in order to combine the two parts into a supercritical mass. Either two hemispheres of fissile material with two explosive capsules are fired at each other, or a cylindrical body of fissile material is fired at a sphere with a corresponding hole.

Such a design of an atomic bomb is called gun design. The Little Boy atomic bomb dropped on Hiroshima by the USA on August 6, 1945 was built according to this system and had an explosive force of 13 kilotons of TNT.

Implosion

Another method is implosion, in which the fissile material is present as a hollow sphere. This is surrounded by a layer of explosive, which is detonated during the explosion by a number of electrical detonators in such a way that the resulting pressure wave compresses the fissile material in the center. This implosion increases its density, creating a supercritical state.

Both the Alamogordo test bomb and the atomic bomb dropped on Nagasaki on August 9, 1945 were implosion bombs. These had an explosive force of 20 kilotons of TNT.

The energy released by the explosion of a nuclear weapon is usually expressed in kilotons. A kiloton, abbreviated kT, is the energy released by the detonation of 1000 tons (1 Gg) of TNT (about 4-1012 J). Therefore, it is also referred to as TNT equivalent. For various reasons, however, the explosive power of conventional and nuclear weapons is only approximately equivalent via this unit. In the case of very powerful explosions, such as those of hydrogen bombs, the explosive force is given in megatons, or MT for short. This unit corresponds to the energy of one million tons (1 Tg) of TNT.

However, the sheer explosive power alone is not yet a measure of the effectiveness of a nuclear weapon. Depending on the type, area of application and explosion level of the weapon, various other factors are important. Among others, the following parameters are in use:

• Total destruction radius: the radius around the explosion center in which all animal and human life as well as all buildings, plants, etc. are completely destroyed. Depending on the size of the bomb, this can be up to 10 km. The experimental Soviet Tsar bomb in its most powerful version had a total destruction radius of up to 20 km. This is followed by other radii where the destructive power of the bomb decreases, e.g. the radius where the chance of survival is above 50%; then the one where it is above 80%, and so on.
• Million dead: Number of people killed in an explosion in a metropolitan area. This quantity depends very much on the location. In particular, the population density and the construction of the city have a very large influence on the number of dead. During the Cold War, model calculations were carried out for the use of powerful nuclear weapons against the most important targets, including Moscow, Leningrad, Washington, D.C., and New York. In modern times, there are corresponding simulations that assume a terrorist attack with a small nuclear weapon (a few kilotons).
• Number of warheads: Many nuclear missiles have multiple nuclear warheads, which are then separated from the launch vehicle at high altitude and spread over a large area. A single missile can devastate huge areas in this way; the Soviet SS-18 Satan, for example, can spread its warheads over an area of up to 60,000 km², depending on how it is equipped. (By comparison, Bavaria has an area of 70,552 km².) In modern missiles, the individual warheads are controllable so that a single target can be attacked with each warhead.

These are in each case not fixed units, but only indicative quantities on the basis of which the damage of a nuclear weapon can be estimated. Depending on the intended use, other quantities may also be of interest, such as the mechanical, thermal and electromagnetic power, or the fallout produced and long-term effects. Sometimes simply technical quantities such as dimensions and weight are important. To get an accurate picture of the effect of a single bomb, detailed knowledge of a wide variety of data is necessary.

The most powerful nuclear weapons designed as regular military warheads are hydrogen bombs with up to 25 MT of explosive power (warhead for SS-18 ICBM or Mk-41 bomb for B-52 bomber). The most powerful nuclear weapon currently in service is probably the warhead of the Chinese DF-5A intercontinental ballistic missile with 3 MT. Typically, however, it is much less, such as 100 kT for the most common American nuclear weapon, W-76-0. Without nuclear fusion, that is, with fission of uranium or plutonium nuclei only, 500 kT (American Ivy King test - Mk-18 bomb) to 800 kT (most powerful French test) are achieved. Fat Man, dropped over Nagasaki, in contrast, had only 20 kT of explosive power. Some modern nuclear weapons also allow a dialing of the explosive power, so the American B83 bomb can be detonated with a few kT up to 1.2 MT.

Strategic nuclear weapons

Strategic nuclear weapons are nuclear weapons with large explosive power that are not used on the battlefield but are intended to destroy targets in the enemy's hinterland, such as entire cities or missile silos of intercontinental missiles. Their explosive power ranges from the kiloton range to theoretically over 100 megatons of TNT in the case of the hydrogen bomb.

The nuclear triad consists of intercontinental ballistic missiles, submarine-launched ballistic missiles, and strategic bombers. The distribution of nuclear weapons across multiple platform types is intended to ensure the striking power of a nuclear force in the event of conflict.

Strategic nuclear weapons are:

• free-fall nuclear bombs dropped directly on the target by aircraft (usually long-range bombers);
• land-based intercontinental ballistic missiles (ICBMs) with nuclear warheads deployed in silos or mobile on land;
• land-based medium-range ballistic missiles (MRBM, IRBM) with nuclear warheads mounted in silos or on mobile launchers. A particular problem of these weapons is their extremely short flight and thus reaction time of only a few minutes. They are therefore considered particularly susceptible to unintentionally triggering a nuclear strike, since there is virtually no time to trigger political decision-making processes after radar-based (mis)detection of such a missile. Examples of such missiles are the Jupiter missiles deployed by the U.S. in Turkey in the 1950s and those missiles that the USSR wanted to deploy in Cuba - which triggered the Cuban Missile Crisis at the time. Today, such weapons are stationed only by those states that lack the technology of intercontinental missiles, such as Pakistan or Israel.
• Submarine-launched ballistic missiles (SLBMs) with nuclear warheads;
• air-launched ballistic missiles (ALBMs) with nuclear warheads launched from aircraft;
• Cruise missiles with nuclear warheads, which can be fired from aircraft (ALCM), warships or submarines, are primarily intended for "tactical" use.

Depending on its design, a missile can also carry several nuclear warheads (so-called MIRV design, Multiple Independently targetable Re-entry Vehicle) and thus devastate radii of several hundred kilometers.

Tactical nuclear weapons

Tactical nuclear weapons (also called nuclear battlefield weapons) are intended to be used in a similar way to conventional weapons to counter enemy forces. Their area of effect and, as a rule, their explosive power are significantly smaller than those of strategic weapons. The smallest tactical nuclear weapon in service has an explosive yield of about 0.3 kT. The small effective radius is intended to permit deployment relatively close to friendly positions.

Tactical nuclear weapons have existed and continue to exist in various forms:

• Nuclear artillery shells (about W9) that can be fired by conventional artillery pieces, see M65 gun, later M109 self-propelled howitzer;
• Infantry grenades with propellant charge (RPG), see Davy Crockett;
• Short-range tactical surface-to-surface missiles (e.g., Honest John, FROG, Lance);
• Atomic Demolition Munitions, colloquially 'atomic mines';
• nuclear free-fall bombs (e.g., B61);
• Air-to-air missiles to combat aircraft, such as the AIM-26 Falcon;
• Surface-to-air missiles (e.g., Bomarc, Nike) to counter aircraft;
• Anti-submarine warfare missiles (e.g., RUR-5 ASROC);
• nuclear depth charges for use against submarines (e.g., B57);
• nuclear-tipped torpedoes (such as the Soviet Shkhale torpedo);
• nuclear-tipped sea target missiles to take out entire carrier groups in a single strike.

The designation "tactical" can be misunderstood insofar as these weapons can already cause the most severe destruction and release considerable radioactivity, which would have devastating effects in the event of war. NATO's "Flexible Response" nuclear strategy assumed that the use of tactical nuclear weapons could be controlled. If conventional means of combat proved too weak, the use of tactical nuclear weapons would make it possible to repel attacks on NATO territory without having to escalate the confrontation to a full-scale nuclear strike (so-called all-out war). On the Soviet side, this theory was rejected from the outset. It was thought to be impossible to limit once the use of nuclear weapons had occurred. France was also very skeptical of the concept.

Neutron bombs

Neutron bombs are tactical nuclear weapons that produce a smaller explosive force (about 1 kT) but a stronger neutron radiation compared to the conventional design.

This was expected to increase the effectiveness against armored forces: For the destruction of tanks, a bomb normally has to explode in the immediate vicinity, since the armor provides protection against pressure and heat. Against neutron radiation, however, it provides little protection, since neutrons penetrate even heavy materials almost unimpeded. Therefore, the explosion of a neutron bomb could instantly kill the crew of a tank without destroying the tank itself. However, the neutron radiation produces secondary radioactivity in the target area, which permanently disables the site and any material remaining there.

In addition, neutron bombs can be used to disable enemy nuclear weapons (e.g., approaching missiles) by destroying their firing or guidance electronics.

The development and deployment of neutron bombs, also in Germany, were initially justified on the grounds that a war waged with them would devastate the country and infrastructure less than conventional nuclear weapons, even with the larger number of explosions required. However, model calculations soon showed that this would hardly be true in practice. This is because in the effectively irradiated area, the pressure and heat effects would already be lethal, buildings and facilities would also be destroyed, and the material would become radioactive through capture. A "clean" alternative to the classical atomic bomb would thus not be achieved.

The neutron weapon's thought process of killing people and preserving things, e.g. tanks, was sharply criticized by many people in Western Europe from 1977 on. Egon Bahr spoke of a "symbol of the perversion of human thinking". Furthermore, it was criticized that death by a neutron bomb was particularly cruel. People exposed to strong neutron beams would die an agonizing and slow death. Victims would suffer hair loss, paralysis, loss of sensory perception and articulation, spasms, uncontrolled diarrhea, and fluid loss for several weeks until they finally died. The peace movement unfolded a campaign against the neutron bomb starting in 1977, first in the Netherlands and then in West Germany.

In addition, critics feared that the neutron bomb would lower the operational threshold of nuclear weapons and thus increase the risk of escalation to war with more powerful nuclear bombs.

About 800 neutron bombs have been built in the USA since 1974. The last neutron bombs were officially scrapped in 1992.

For a stationing site in Germany in the 1980s, see Special Ammunition Depot Giessen.

Mini Nukes

So-called mini-nukes are nuclear weapons with an explosive force of less than five kilotons. New research into small, technically advanced nuclear weapons is planned in the USA. In May 2003, the U.S. Senate lifted a ten-year-old ban on the development of mini-nukes. This decision was weakened in Congress by a resolution allowing the research but maintaining a ban on the development or production of new low-yield nuclear weapons.

Suitcase bombs, for example for use by intelligence services or terrorists, have been described and are also presented on the High Energy Weapons Archive; however, it is also emphasized there that the physical feasibility is more than doubtful (for example, too high quantities of conventional explosives would have been needed for detonation). On the other hand, the weight of the American W-54 warhead to the Davy Crockett light gun was already only 23 kilograms. The egg-shaped weapon from the 1950s had a diameter of only about 27 cm by 40 cm in length and achieved a maximum explosive force of about 0.02 kT TNT equivalent.

Furthermore, in the 1950s and 1960s, NASA was developing a propulsion technology using small nuclear warheads, as it was to be used for manned or unmanned missions. The concept was discarded, but the documents of 'Project Orion' are still under lock and key, mainly to prevent misuse by e.g. terrorists.

Bunker Crusher

Nuclear bunker-busting weapons are designed to penetrate deep into the earth to destroy underground and hardened bunkers. There is no way that the bombs, dropped from the air, can penetrate deep enough below the surface and the explosion will be completely underground. Thus, a bomb crater is created and highly radioactive material is ejected into the air. Likewise, the shocks generated are likely to cause widespread destruction around the actual target. There is already a "bunker buster" in the U.S. arsenal: the B-61-11, which, according to the Nuclear Posture Review (NPR) of U.S. nuclear weapons policy published in January 2002, has an explosive force size of more than five kilotons and is therefore not a "mini-nuke." This weapon penetrates only up to seven meters into the earth and 2-3 meters into frozen ground from an altitude of just over 13,000 meters. The U.S. has about 50 of these bombs at its disposal.

Dirty bomb

In the case of a dirty bomb, the effect of the explosion is further enhanced by radioactive fallout contamination over a large area and over many years. This is achieved by building the weapon or by a nuclear explosion on the ground (for the latter, see nuclear weapon explosion). The cobalt bomb in particular has been called a dirty bomb. In this design, a cobalt casing is placed around the actual explosive device. This metal is transformed by the explosion into ^60Co, a highly radiating isotope with a relatively long half-life, which should rain down as dust and contaminate the area in question for a long time.

At the beginning of the 21st century, the term dirty bomb was coined differently. It is now used to describe an explosive device made of conventional explosives to which radioactive material has been added to be distributed as widely as possible by the explosion. A nuclear explosion does not take place. It is assumed that terrorists could use such IEDs to spread terror.

The International Atomic Energy Agency also warns that terrorists could acquire radioactive material, e.g. from successor states of the Soviet Union. There, as in the U.S., substances are repeatedly lost from industry, research institutions or hospitals. Since the material for a dirty bomb can be obtained from civilian nuclear technology, all nuclear technology is also counted among dual-use products.

The Goiânia accident in Brazil in 1987 is sometimes cited as an example of the consequences of a dirty bomb, when thieves broke into an empty hospital and stole a container of radioactive ^{137Caesium chloride} and took it home. Out of curiosity and ignorance, many people handled the bluish fluorescent material in their neighborhoods and carried pieces of the substance around with them. Several residential districts were affected, and eventually four people died from radiation sickness, ten others needed intensive medical treatment, and 85 buildings had to be demolished or decontaminated.

All states in Europe have ratified the Nuclear Non-Proliferation Treaty, which entered into force on March 5, 1970. According to the treaty, only Great Britain, France and the Soviet Union or its successor state Russia are allowed to possess nuclear weapons (from the states located in Europe). The European nuclear powers, like the other European countries, are also prohibited from passing on nuclear weapons. In addition, the Federal Republic of Germany committed itself to the victorious powers of World War II to renounce the construction of nuclear weapons through the Treaty of Germany, which entered into force on May 5, 1955. This renunciation was reaffirmed in 1990 in the Two Plus Four Treaty.

The nuclear weapons stored in Europe (cf. special ammunition depots) have been drastically reduced after the end of the Cold War. Between 1990 and 1996, some 208 NATO nuclear weapons silos were built at European air bases. Originally, 438 NATO bunkers were planned for this purpose, but they were no longer needed. The bunkers controlled by U.S. forces for bombs that were available to NATO forces in an emergency had not all been stockpiled. By 1998, the United Kingdom had dismantled its arsenal of drop bombs on bases. Then, starting in 1996, the other arsenals were emptied.

The U.S. and Britain stored up to 5,000 nuclear weapons in German bunkers during the Cold War, including the Zebra package intended for use inside Germany. An estimated 480 nuclear weapons are believed to be stored in Europe today as part of nuclear sharing, 20 of which are at Büchel Air Base in Germany. There, the Air Force trains the use of nuclear weapons by Tornado fighter-bombers as part of the nuclear sharing program. The German air bases in Memmingen and Nörvenich no longer had any nuclear weapons as early as 1995. It is also assumed that the 130 warheads were withdrawn from Ramstein Air Base.

The two Western European nuclear powers, Great Britain and France, began converting parts of their arsenals to sea-based systems as early as the 1960s and 1970s, respectively. Today, both countries maintain four ballistic nuclear submarines, each of which can be equipped with 16 nuclear missiles. France now maintains only 60 warheads for use by bombers, while the United Kingdom has had only sea-based systems since 2000. As a result of this change, the number of storage sites at air bases has also been reduced. Sea-based warheads now account for the majority of nuclear weapons deployed in Europe. British warheads are stored entirely at Clyde Naval Base, while French warheads are stored at Brest.

Switzerland began a study of producing its own weapons shortly after the American atomic bombs were dropped. After initial secrecy until 1958, the Swiss nuclear weapons program was uniquely legitimized by two referenda in 1962 and 1963, continued in the form of planning, and only definitively stopped in 1988, although Switzerland had already signed the Nuclear Non-Proliferation Treaty in 1969. In 1995, its indefinite extension was agreed to, and in 2016 the remaining 20 kg of weapons-grade plutonium were transported from the Swiss stockpile to the USA.

(As of 2011, for number of weapons and storage systems; as of 2019, for locations with stored nuclear weapons).

• Great Britain
• Lakenheath (33 WS3 storage systems, currently no weapons stored).
• Netherlands
• Volkel (eleven WS3 storage systems, 10-20 bombs B61-3/4)
• Belgium
• Small Brogel (eleven WS3 storage systems, 10-20 bombs B61-3/4).
• Germany
• Büchel Air Base (eleven WS3 storage systems, 10-20 B61-3/4 bombs)
• Ramstein Air Base (55 WS3 storage systems, currently no weapons stored)
• Italy
• Aviano (18 WS3 storage systems, 50 bombs B61-3/4)
• Ghedi-Torre (eleven WS3 storage systems, 10-20 B61-3/4 bombs).
• Greece
• Araxos (eleven WS3 storage systems, currently no weapons stored)
• Turkey
• Balıkesir (eleven WS3 storage systems, currently no weapons stored).
• Incirlik Air Base (25 WS3 storage systems, 60-70 bombs B61-3/4)
• Akıncı (Mürted) (eleven WS3 storage systems, currently no weapons stored).

The five permanent members of the Security Council are considered official nuclear powers. They are listed in the Nuclear Non-Proliferation Treaty as states with nuclear weapons.

Two states have so far made public the number of their nuclear warheads. However, these figures refer only to deployable warheads, not deactivated ones.

• Great Britain: 225
• USA: 5,113

The exact number of nuclear warheads is often unclear and must be estimated. The Federation of American Scientists announced the following figures for 2009:

• China: ≈ 180
• France: ≈ 300
• Great Britain: ≈ 160
• Russia: ≈ 13,000 (4,830 operational)
• USA: 9,400 (2,700 operational)

India, Pakistan, Israel, and North Korea are not listed in the Nuclear Non-Proliferation Treaty but still possess nuclear weapons and delivery systems (2008 figures):

• India: ≈ 50
• Israel: ≈ 80
• Pakistan: ≈ 60
• North Korea: < 10

The Carnegie Endowment for International Peace issued the following data for 2007 in its Proliferation Report:

• China: 410
• France: 350
• Great Britain: 200
• Russia: ≈ 16,000
• United States: ≈ 10,300

as well as

• India: ≈ 75 to 110
• Israel: ≈ 100 to 170
• Pakistan: ≈ 50 to 110

The United States reported in May 2010 that it had 5,113 operational nuclear warheads as of September 2009. In 1967, the figure was 31,255 warheads.

The United Kingdom gave the full number of its warheads at the end of May 2010. In a question and answer session, British Foreign Secretary William Hague announced that the country had 225 nuclear weapons. In doing so, the British government changed its traditional stance of announcing only the number of deployable warheads.

Although not officially confirmed for a long time, it is considered indisputable that Israel has also been in possession of nuclear weapons since the 1970s. Mordechai Vanunu, then a technician at the Negev Nuclear Research Center, betrayed the existence of Israel's nuclear weapons project in 1986 and was kidnapped by Mossad from Rome to Israel. On December 11, 2006, Israeli Prime Minister Olmert admitted to the German channel Sat.1 that Israel was a nuclear power. However, this was later denied by him again. There had previously been protests at home and abroad in response to this statement. In January 2007, Iranian media reported that Israel was planning a nuclear attack on Iran, which was denied by Tel Aviv.

North Korean nuclear weapons

North Korea also declared in spring 2005 that it had developed nuclear weapons as a deterrent; however, the statement was and is doubted by various sides. It was and is undisputed, however, that North Korea maintains an ambitious program to obtain nuclear weapons. On October 3, 2006, the North Korean government announced its intention to conduct nuclear bomb tests.

On October 9, 2006, at 10:36 a.m. local time, a successful underground nuclear weapons test was conducted at Hwadaeri near Kilju and later confirmed by seismic measurements in Russia and the United States. The explosive force was over 800 tons of TNT, according to South Korean estimates. Russia's Defense Ministry, on the other hand, estimates 5 to 15 kilotons of TNT. (By comparison, the Hiroshima bomb had an explosive force of the equivalent of 13 kilotons of TNT.) To date, however, it is not clear whether the detonation on October 9, 2006, was actually a nuclear explosion. It is possible that the detonation could also have been carried out by conventional means in order to increase political pressure on the international community. U.S. spy planes have provided evidence of very faintly elevated radioactivity in the atmosphere above the test site, but it was so faint that it was not detected at all until the second attempt. A second nuclear weapons test apparently succeeded on May 25, 2009, reportedly achieving an explosive yield of 20 kilotons. On January 6, 2016, North Korea announced that a successful test of a hydrogen bomb had been conducted. However, experts doubt that it was really a successful test of a hydrogen bomb, as the energy released was too low for a hydrogen bomb explosion. Either the test failed or it was only a hybrid nuclear bomb.

Iran programs

Iran is accused of striving for nuclear weapons, first and foremost by Israel and the USA. However, there is no proof of this. According to its own statements, Iran is working on the civilian use of nuclear power for energy generation.

Diplomats in Vienna, the headquarters of the International Atomic Energy Agency (IAEA), told the F.A.Z. in 2015 that Iran had already installed 1,000 centrifuges for uranium enrichment at the Natans facility a few weeks ago. This is a significant increase, as Iran initially had only 164 centrifuges in operation twice after enrichment began a year ago. The government in Tehran had even reported on April 12, 2007, that it had a total of 3,000 centrifuges in operation, which meant that enrichment had reached industrial levels.

The number of centrifuges is considered important because it can be used to gauge the progress of Iran's nuclear program. Western governments fear that Iran wants to acquire the capability to build nuclear weapons under the guise of a civilian nuclear program. About 3,000 centrifuges are considered necessary to produce the material for one to two nuclear bombs a year.

Programs or property in the past

With the disintegration of the Soviet Union, there were three other successor states of the USSR with nuclear weapons besides Russia: Ukraine, Belarus and Kazakhstan. Ukraine was at times the country with the third largest nuclear arsenal on earth. All of these states were parties to the START-1 Treaty, which was signed by the Soviet Union and the United States in 1991 and entered into force in 1995. Ukraine, Belarus, and Kazakhstan committed to the NPT treaty and pledged to destroy their nuclear arsenals. Kazakhstan and Belarus became nuclear-weapon-free by 1996. The last Ukrainian warhead was destroyed in Russia in October 2001.

South Africa developed a nuclear weapon under the apartheid government, probably with Israeli help, and possibly conducted a test off its coast in September 1979. Shortly before the end of apartheid, South Africa destroyed its six nuclear weapons in order to join the Nuclear Non-Proliferation Treaty in 1991 and thus rejoin international society. By 1994, all South African nuclear weapons facilities had been dismantled.

Argentina, Brazil, Libya, and Switzerland had nuclear weapons programs in the past, but have abandoned and officially ended them. The government of Sweden debated whether to develop nuclear weapons after 1945 and decided against it.

Between 1950 and 1980, 32 accidents involving U.S. nuclear weapons alone were reported. According to research by Eric Schlosser, the U.S. government recorded at least 700 "significant" accidents and incidents involving some 1250 nuclear weapons between 1950 and 1968. Especially in the 1950s and 1960s, many weapons had to be dropped during emergency bomber landings. Some of the weapons were never recovered because they were dropped (but not detonated) in the oceans. Greenpeace estimates that about 50 nuclear bombs were lost. Eleven bombs are officially missing from the United States. Radioactive contamination was found in several cases.

Crashes of nuclear bombers and other accidents are very problematic because the impact can scatter the fissile material in the environment, even if the bomb does not detonate. In the case of plutonium, this is particularly dangerous because it also has chemical toxicity.

See also:

• Intercontinental ballistic missile accidents
• Accidents with nuclear weapons on board the B-36 bomber
• Accidents with nuclear weapons on board the B-47 bomber
• Accidents with nuclear weapons on board the bomber B-50
• Accidents with nuclear weapons on board the strategic bomber B-52
• Accidents with nuclear weapons on board the Douglas C-124 transport aircraft
• Loss of a nuclear weapon and a Douglas A-4
• Loss of a nuclear weapon on board the flying boat Martin P5M
• List of submarine accidents since 1945, including nuclear submarines with nuclear missiles.

However, not only in the case of accidents, but also as part of the disposal process within normal production, massive amounts of radioactive material were released into the environment, especially in the Soviet Union (Mayak, Lake Karachai).

Because of the enormous destructive power of nuclear bombs, there have always been efforts to abolish all nuclear weapons and to ban them in general in order to prevent them from destroying mankind. However, the Cold War and the power interests of individual nations prevented a rapid move away from weapons of mass destruction. Nevertheless, a number of treaties were enforced, each signaling a major step toward a world free of nuclear weapons. Whether the treaties are actually as effective as desired, however, is in doubt.

On October 10, 1963, the Test Ban Treaty came into force, in which several major powers agreed not to detonate nuclear weapons in water, in space, or in the atmosphere. Underground tests were not to exceed a certain level. To date, 120 nations have joined this agreement.

The Nuclear Non-Proliferation Treaty was signed by the USA, the Soviet Union and Great Britain on July 1, 1968, and entered into force in 1970. After North Korea withdrew its signature in 2003, the treaty is valid in 188 states. Signatories also include the People's Republic of China and France (both in 1992). Accession to the Treaty on the Non-Proliferation of Nuclear Weapons implies an obligation on the part of the signatory states to submit at regular intervals to inspections carried out by the International Atomic Energy Agency to ensure compliance with the treaty. However, Article VI states that states undertake to conduct negotiations "in the near future" that guarantee "complete disarmament."

The Comprehensive Nuclear-Test-Ban Treaty (CTBT) has been open for signature since 1996. It will not enter into force until a certain group of countries has ratified it, including the USA. Ratifications by some key countries are currently pending. The U.S. in particular opposes arms controls.

Compliance with the contracts is verified by various techniques: Earthquake monitoring stations respond to even the smallest vibrations and allow fairly accurate location of underground detonations. They can also clearly distinguish the seismographic signatures of earthquakes and nuclear weapons tests. Hydroacoustics can detect and locate underwater explosions. Special microphones and radionuclide detectors can detect, identify, and locate atmospheric nuclear explosions. The monitoring stations are located around the world. When the treaty goes into effect, there will also still be the option of on-site inspection. The implementation of the treaty is being prepared by the Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO).

Bilateral treaties between the United States and the Soviet Union or Russia aimed at limiting or disarming strategic nuclear weapons include the SALT I and II talks (1969 to 1979) that led to the ABM Treaty (1972), the INF Treaty (1987), START I and II (1991 and 1993), and the SORT Treaty (2002).

Uranium-based nuclear bombs contain highly enriched uranium. One speaks of weapons-grade uranium only from an enrichment level of 85 %. Natural uranium has 0.7% uranium-235; for use in light water reactors, the uranium must be enriched to 3-4% ^{235U content} (reactor-grade). Highly enriched uranium is therefore a valuable raw material.

Plutonium from plutonium bombs, on the other hand - a very problematic substance because of its long half-life and high radiotoxicity - cannot be destroyed: "Plutonium can only be disposed of in the form of final disposal after mixing with other nuclear waste or by reworking it into MOX elements."

Between 1993 and 2013, the U.S. and Russia successfully cooperated on the megaton-to-megawatt disarmament project. By converting 500 tons of Russian nuclear weapons material into electricity, the U.S. covered 10% of its electricity generation for 20 years and Russia received a total of $17 billion.

Numerous international campaigns advocate for the abolition of all nuclear weapons, including:

• International Campaign to Abolish Nuclear Weapons (ICAN)
• International Physicians for the Prevention of Nuclear War / Physicians in Social Responsibility e. V. (IPPNW)
• Büchel is everywhere! atomwaffenfrei.jetzt
• Parliamentary Network for Nuclear Disarmament and Non-Proliferation (PNND)

Numerous appeals for nuclear disarmament and arms control were also made to politicians from the physics community - such as the Franck Report, the Russell-Einstein Manifesto, which led to the founding of the Pugwash Movement, the Mainau Rally or the Declaration of the Göttingen Eighteen. A number of resolutions by the German Physical Society (DPG) also pointed out the dangers associated with the existence of nuclear weapons and called for the reduction of existing arsenals and the conclusion of a nuclear test ban treaty. In its resolution of April 2010, the DPG first advocates the renunciation of first use and the withdrawal of all nuclear weapons remaining in Germany and Europe.

In addition, all Christian churches are opposed in principle to the use of any kind of nuclear weapons, and in some cases even to the possession of them. As recently as 2006, the World Council of Churches again called for the elimination of all nuclear weapons.

Starting with Catholic philosophers in Britain in the early 1960s, ethical concerns were introduced against the strategy of nuclear deterrence. For many people, the use of a nuclear weapon was immoral because it would necessarily result in the death of civilians and the poisoning of the earth. The argument was as follows: If the use of nuclear weapons was immoral, the same was true of the strategy of nuclear deterrence, since it involved the conditional intention to act immorally.

In the Catholic Church, with the Second Vatican Council (1965), the use of so-called scientific weapons is pointed out as exceeding the limits of a just defense, since the use of the same can "cause immense and uncontrollable destruction". The Pastoral Constitution Gaudium et Spes further pronounces a prohibition of total war, which "aims at the destruction of entire cities or vast areas and their populations without distinction." (GS 80)

Violation of the principles of discrimination and proportionality (see Just War) represent the main criticisms of the use of nuclear weapons.

On March 27, 2017, negotiations on a treaty banning nuclear weapons began following a decision by the UN General Assembly. The aim is to achieve an "unequivocal political commitment" to the goal of a world free of nuclear weapons. This is intended as a first, quickly achievable step toward a nuclear weapons convention that also includes concrete disarmament measures. However, only two-thirds of the 193 member states are initially taking part in the negotiations. The nuclear powers and almost all NATO states, including Germany, are not involved.

• Atomic war watch
• Nuclear Force
• Nuclear weapons in Germany
• Nuclear Weapons Effect
• Nuclear warheads list
• Civil nuclear explosive device explains procedure for civil use of nuclear explosions