Nuclear weapons tests are experiments carried out to determine the performance of
nuclear weapon
A nuclear weapon is an explosive device that derives its destructive force from nuclear reactions, either fission (fission or atomic bomb) or a combination of fission and fusion reactions (thermonuclear weapon), producing a nuclear exp ...
s and the effects of
their explosion. Nuclear testing is a sensitive political issue. Governments have often performed tests to signal strength. Because of their destruction and
fallout
Nuclear fallout is residual radioactive material that is created by the reactions producing a nuclear explosion. It is initially present in the radioactive cloud created by the explosion, and "falls out" of the cloud as it is moved by the ...
, testing has seen opposition by civilians as well as governments, with international bans having been agreed on. Thousands of tests have been performed, with most in the second half of the 20th century.
The first nuclear device was detonated as a test by the United States at the
Trinity site
Trinity was the first detonation of a nuclear weapon, conducted by the United States Army at 5:29 a.m. MWT (11:29:21 Greenwich Mean Time, GMT) on July 16, 1945, as part of the Manhattan Project. The test was of an implosion-type nuclear ...
in
New Mexico
New Mexico is a state in the Southwestern United States, Southwestern region of the United States. It is one of the Mountain States of the southern Rocky Mountains, sharing the Four Corners region with Utah, Colorado, and Arizona. It also ...
on July 16, 1945, with a yield approximately
equivalent
Equivalence or Equivalent may refer to:
Arts and entertainment
*Album-equivalent unit, a measurement unit in the music industry
*Equivalence class (music)
*'' Equivalent VIII'', or ''The Bricks'', a minimalist sculpture by Carl Andre
*'' Equiva ...
to 20
kiloton
TNT equivalent is a convention for expressing energy, typically used to describe the energy released in an explosion. A ton of TNT equivalent is a unit of energy defined by convention to be (). It is the approximate energy released in the det ...
s of
TNT
Troponin T (shortened TnT or TropT) is a part of the troponin complex, which are proteins integral to the contraction of skeletal and heart muscles. They are expressed in skeletal and cardiac myocytes. Troponin T binds to tropomyosin and helps ...
. The first
thermonuclear weapon
A thermonuclear weapon, fusion weapon or hydrogen bomb (H-bomb) is a second-generation nuclear weapon design. Its greater sophistication affords it vastly greater destructive power than first-generation nuclear bombs, a more compact size, a lowe ...
technology test of an engineered device, codenamed
Ivy Mike
Ivy Mike was the code name, codename given to the first full-scale test of a Thermonuclear weapon, thermonuclear device, in which a significant fraction of the explosive nuclear weapon yield, yield comes from nuclear fusion.
Ivy Mike was detona ...
, was tested at the
Enewetak Atoll
Enewetak Atoll (; also spelled Eniwetok Atoll or sometimes Eniewetok; , , or , ; known to the Japanese as Brown Atoll or Brown Island; ) is a large coral atoll of 40 islands in the Pacific Ocean and with its 296 people (as of 2021) forms a leg ...
in the
Marshall Islands
The Marshall Islands, officially the Republic of the Marshall Islands, is an island country west of the International Date Line and north of the equator in the Micronesia region of the Northwestern Pacific Ocean.
The territory consists of 29 c ...
on November 1, 1952 (local date), also by the United States. The largest nuclear weapon ever tested was the
Tsar Bomba
The Tsar Bomba (code name: ''Ivan'' or ''Vanya''), also known by the alphanumerical designation "AN602", was a Thermonuclear weapon, thermonuclear aerial bomb, and by far the most powerful nuclear weapon ever created and tested. The Soviet phy ...
of the
Soviet Union
The Union of Soviet Socialist Republics. (USSR), commonly known as the Soviet Union, was a List of former transcontinental countries#Since 1700, transcontinental country that spanned much of Eurasia from 1922 until Dissolution of the Soviet ...
at
Novaya Zemlya
Novaya Zemlya (, also , ; , ; ), also spelled , is an archipelago in northern Russia. It is situated in the Arctic Ocean, in the extreme northeast of Europe, with Cape Flissingsky, on the northern island, considered the extreme points of Europe ...
on October 30, 1961, with the largest yield ever seen, an estimated 50–58
megatons.
With the advent of nuclear technology and its increasingly global fallout an
anti-nuclear movement
The Anti-nuclear war movement is a new social movements, social movement that opposes various nuclear technology, nuclear technologies. Some direct action groups, environmental movements, and professional organisations have identified them ...
formed and in 1963, three (UK, US, Soviet Union) of the then four nuclear states and many non-nuclear states signed the
Limited Test Ban Treaty, pledging to refrain from testing nuclear weapons in the atmosphere, underwater, or in
outer space. The treaty permitted
underground nuclear testing
Underground nuclear testing is the test detonation of nuclear weapons that is performed underground. When the device being tested is buried at sufficient depth, the nuclear explosion may be contained, with no release of radioactive materials t ...
.
France
France, officially the French Republic, is a country located primarily in Western Europe. Overseas France, Its overseas regions and territories include French Guiana in South America, Saint Pierre and Miquelon in the Atlantic Ocean#North Atlan ...
continued atmospheric testing until 1974, and
China
China, officially the People's Republic of China (PRC), is a country in East Asia. With population of China, a population exceeding 1.4 billion, it is the list of countries by population (United Nations), second-most populous country after ...
continued until 1980. Neither has signed the treaty.
Underground tests conducted by the Soviet Union continued until 1990, the United Kingdom until 1991, the United States until 1992, and both China and France until 1996. In signing the
Comprehensive Nuclear-Test-Ban Treaty
The Comprehensive Nuclear-Test-Ban Treaty (CTBT) is a multilateral treaty to ban nuclear weapons test explosions and any other nuclear explosions, for both civilian and military purposes, in all environments. It was adopted by the United Nati ...
in 1996, these countries pledged to discontinue all nuclear testing; the treaty has not yet entered into force because of its failure to be ratified by eight countries. Non-signatories
India
India, officially the Republic of India, is a country in South Asia. It is the List of countries and dependencies by area, seventh-largest country by area; the List of countries by population (United Nations), most populous country since ...
and
Pakistan
Pakistan, officially the Islamic Republic of Pakistan, is a country in South Asia. It is the List of countries and dependencies by population, fifth-most populous country, with a population of over 241.5 million, having the Islam by country# ...
last tested nuclear weapons in 1998.
North Korea
North Korea, officially the Democratic People's Republic of Korea (DPRK), is a country in East Asia. It constitutes the northern half of the Korea, Korean Peninsula and borders China and Russia to the north at the Yalu River, Yalu (Amnok) an ...
conducted
nuclear tests in
2006
2006 was designated as the International Year of Deserts and Desertification.
Events
January
* January 1– 4 – Russia temporarily cuts shipment of natural gas to Ukraine during a price dispute.
* January 12 – A stampede during t ...
,
2009
2009 was designated as the International Year of Astronomy by the United Nations to coincide with the 400th anniversary of Galileo Galilei's first known astronomical studies with a telescope and the publication of Astronomia Nova by Joha ...
,
2013
2013 was the first year since 1987 to contain four unique digits (a span of 26 years).
2013 was designated as:
*International Year of Water Cooperation
*International Year of Quinoa
Events
January
* January 5 – 2013 Craig, Alask ...
,
January 2016,
September 2016 and 2017. The
most recent confirmed nuclear test in September 2017 in North Korea.
Types

Nuclear weapons tests have historically been divided into four categories reflecting the medium or location of the test.
*Atmospheric testing involves explosions that take place in the
atmosphere
An atmosphere () is a layer of gases that envelop an astronomical object, held in place by the gravity of the object. A planet retains an atmosphere when the gravity is great and the temperature of the atmosphere is low. A stellar atmosph ...
. Generally, these have occurred as devices detonated on
towers
A tower is a tall Nonbuilding structure, structure, taller than it is wide, often by a significant factor. Towers are distinguished from guyed mast, masts by their lack of guy-wires and are therefore, along with tall buildings, self-supporting ...
, balloons, barges, or islands, or dropped from airplanes, and also those only buried far enough to intentionally create a surface-breaking crater. The United States, the Soviet Union, and China have all conducted tests involving explosions of missile-launched warheads (See
List of nuclear weapons tests#Tests of live warheads on rockets). Nuclear explosions close enough to the ground to draw dirt and debris into their
mushroom cloud
A mushroom cloud is a distinctive mushroom-shaped flammagenitus cloud of debris, smoke, and usually condensed water vapour resulting from a large explosion. The effect is most commonly associated with a nuclear explosion, but any sufficiently e ...
can generate large amounts of
nuclear fallout
Nuclear fallout is residual radioactive material that is created by the reactions producing a nuclear explosion. It is initially present in the mushroom cloud, radioactive cloud created by the explosion, and "falls out" of the cloud as it is ...
due to
irradiation
Irradiation is the process by which an object is exposed to radiation. An irradiator is a device used to expose an object to radiation, most often gamma radiation, for a variety of purposes. Irradiators may be used for sterilizing medical and p ...
of the debris (particularly with
neutron radiation
Neutron radiation is a form of ionizing radiation that presents as free neutrons. Typical phenomena are nuclear fission or nuclear fusion causing the release of free neutrons, which then react with nuclei of other atoms to form new nuclides— ...
) as well as
radioactive contamination
Radioactive contamination, also called radiological pollution, is the deposition of, or presence of Radioactive decay, radioactive substances on surfaces or within solids, liquids, or gases (including the human body), where their presence is uni ...
of otherwise non-radioactive material. This definition of atmospheric is used in the
Limited Test Ban Treaty, which banned this class of testing along with exoatmospheric and underwater.
*Underground testing is conducted under the surface of the earth, at varying depths.
Underground nuclear testing
Underground nuclear testing is the test detonation of nuclear weapons that is performed underground. When the device being tested is buried at sufficient depth, the nuclear explosion may be contained, with no release of radioactive materials t ...
made up the majority of nuclear tests by the United States and the Soviet Union during the
Cold War
The Cold War was a period of global Geopolitics, geopolitical rivalry between the United States (US) and the Soviet Union (USSR) and their respective allies, the capitalist Western Bloc and communist Eastern Bloc, which lasted from 1947 unt ...
; other forms of nuclear testing were banned by the
Limited Test Ban Treaty in 1963. True underground tests are intended to be fully contained and emit a negligible amount of fallout. Unfortunately these nuclear tests do occasionally "vent" to the surface, producing from nearly none to considerable amounts of radioactive debris as a consequence. Underground testing, almost by definition, causes
seismic
Seismology (; from Ancient Greek σεισμός (''seismós'') meaning "earthquake" and -λογία (''-logía'') meaning "study of") is the scientific study of earthquakes (or generally, quakes) and the generation and propagation of elastic ...
activity of a magnitude that depends on the
yield of the nuclear device and the composition of the medium in which it is detonated, and generally creates a
subsidence crater. In 1976, the United States and the USSR agreed to limit the maximum yield of underground tests to 150
kt with the
Threshold Test Ban Treaty.
Underground testing also falls into two physical categories: tunnel tests in generally horizontal tunnel ''drifts'', and shaft tests in vertically drilled holes.
*Exoatmospheric testing is conducted above the atmosphere. The test devices are lifted on rockets. These
high-altitude nuclear explosions can generate a
nuclear electromagnetic pulse
A nuclear electromagnetic pulse (nuclear EMP or NEMP) is a burst of electromagnetic radiation created by a nuclear explosion. The resulting rapidly varying electric and magnetic fields may couple with electrical and electronic systems to produce ...
(NEMP) when they occur in the
ionosphere
The ionosphere () is the ionized part of the upper atmosphere of Earth, from about to above sea level, a region that includes the thermosphere and parts of the mesosphere and exosphere. The ionosphere is ionized by solar radiation. It plays ...
, and charged particles resulting from the blast can cross hemispheres following
geomagnetic lines of force to create an auroral display.
*Underwater testing involves nuclear devices being
detonated underwater, usually moored to a ship or a barge (which is subsequently destroyed by the explosion). Tests of this nature have usually been conducted to evaluate the effects of nuclear weapons against naval vessels (such as in
Operation Crossroads
Operation Crossroads was a pair of nuclear weapon tests conducted by the United States at Bikini Atoll in mid-1946. They were the first nuclear weapon tests since Trinity on July 16, 1945, and the first detonations of nuclear devices sinc ...
), or to evaluate potential sea-based nuclear weapons (such as
nuclear torpedo
A nuclear torpedo is a torpedo armed with a nuclear warhead.
The idea behind the nuclear warheads in a torpedo was to create a much bigger explosive blast. Later analysis suggested that smaller, more accurate, and faster torpedoes were more efficie ...
es or
depth charges). Underwater tests close to the surface can disperse large amounts of radioactive particles in water and steam, contaminating nearby ships or structures, though they generally do not create fallout other than very locally to the explosion.
Salvo tests
Another way to classify nuclear tests is by the number of explosions that constitute the test. The treaty definition of a salvo test is:
In conformity with treaties between the United States and the Soviet Union, a salvo is defined, for multiple explosions for peaceful purposes, as two or more separate explosions where a period of time between successive individual explosions does not exceed 5 seconds and where the burial points of all explosive devices can be connected by segments of straight lines, each of them connecting two burial points, and the total length does not exceed 40 kilometers. For nuclear weapon tests, a salvo is defined as two or more underground nuclear explosions conducted at a test site within an area delineated by a circle having a diameter of two kilometers and conducted within a total period of time of 0.1 seconds.
The USSR has exploded up to eight devices in a single salvo test; Pakistan's second and last official test exploded four different devices. Almost all lists in the literature are lists of tests; in the lists in Wikipedia (for example, ''
Operation Cresset
Operation Cresset was a group of 22 nuclear test
Nuclear weapons tests are experiments carried out to determine the performance of nuclear weapons and the effects of their explosion. Nuclear testing is a sensitive political issue. Governm ...
'' has separate items for ''Cremino'' and ''Caerphilly'', which together constitute a single test), the lists are of explosions.
Purpose
Separately from these designations, nuclear tests are also often categorized by the purpose of the test itself.
* Weapons-related tests are designed to garner information about how (and if) the weapons themselves work. Some serve to develop and validate a specific weapon type. Others test experimental concepts or are physics experiments meant to gain fundamental knowledge of the processes and materials involved in nuclear detonations.
* Weapons effects tests are designed to gain information about the effects of the weapons on structures, equipment, organisms, and the environment. They are mainly used to assess and improve survivability to nuclear explosions in civilian and military contexts, tailor weapons to their targets, and develop the tactics of nuclear warfare.
* Safety experiments are designed to study the behavior of weapons in simulated accident scenarios. In particular, they are used to verify that a (significant) nuclear detonation cannot happen by accident. They include one-point safety tests and simulations of storage and transportation accidents.
* Nuclear test detection experiments are designed to improve the capabilities to detect, locate, and identify nuclear detonations, in particular, to monitor compliance with test-ban treaties. In the United States these tests are associated with Operation
Vela Uniform before the
Comprehensive Test Ban Treaty
The Comprehensive Nuclear-Test-Ban Treaty (CTBT) is a multilateral treaty to ban nuclear weapons test explosions and any other nuclear explosions, for both civilian and military purposes, in all environments. It was adopted by the United Nati ...
stopped all nuclear testing among signatories.
*
Peaceful nuclear explosions
Peaceful nuclear explosions (PNEs) are nuclear explosions conducted for non-military purposes. Proposed uses include excavation for the building of canals and harbours, electrical generation, the use of nuclear explosions to drive spacecraft, and a ...
were conducted to investigate non-military applications of nuclear explosives. In the United States, these were performed under the umbrella name of
Operation Plowshare.
Aside from these technical considerations, tests have been conducted for political and training purposes, and can often serve multiple purposes.
Alternatives to full-scale testing

Since the 1996
Comprehensive Nuclear-Test-Ban Treaty
The Comprehensive Nuclear-Test-Ban Treaty (CTBT) is a multilateral treaty to ban nuclear weapons test explosions and any other nuclear explosions, for both civilian and military purposes, in all environments. It was adopted by the United Nati ...
, "nuclear explosions" of all kinds are banned. Nuclear nations have invested in many alternatives to maintain confidence in weapon capability:
*
Computer simulation
Computer simulation is the running of a mathematical model on a computer, the model being designed to represent the behaviour of, or the outcome of, a real-world or physical system. The reliability of some mathematical models can be determin ...
is used extensively to provide as much information as possible without physical testing. Mathematical models for such simulation model scenarios not only of performance but also of
shelf life
Shelf life is the length of time that a commodity may be stored without becoming unfit for use, consumption, or sale. In other words, it might refer to whether a commodity should no longer be on a pantry shelf (unfit for use), or no longer on a s ...
and
maintenance
The technical meaning of maintenance involves functional checks, servicing, repairing or replacing of necessary devices, equipment, machinery, building infrastructure and supporting utilities in industrial, business, and residential installa ...
.
A theme has generally been that even though simulations cannot fully replace physical testing, they can reduce the amount of it that is necessary.
* Physical testing
** Materials testing
*** Subcritical (or cold) tests involving fissile materials and
high explosives
An explosive (or explosive material) is a reactive substance that contains a great amount of potential energy that can produce an explosion if released suddenly, usually accompanied by the production of light, heat, sound, and pressure. An exp ...
that purposely result in no
yield. The name refers to the lack of creation of a
critical mass
In nuclear engineering, critical mass is the minimum mass of the fissile material needed for a sustained nuclear chain reaction in a particular setup. The critical mass of a fissionable material depends upon its nuclear properties (specific ...
of fissile material. Subcritical tests continue to be performed by the United States, Russia, and the People's Republic of China, at least.
*** Proxy isotope testing: high temperature/density/pressure compression testing of non-fissile isotopes such as
plutonium-242 or
uranium-238
Uranium-238 ( or U-238) is the most common isotope of uranium found in nature, with a relative abundance of 99%. Unlike uranium-235, it is non-fissile, which means it cannot sustain a chain reaction in a thermal-neutron reactor. However, it i ...
, to determine a bomb core's relevant
equation of state
In physics and chemistry, an equation of state is a thermodynamic equation relating state variables, which describe the state of matter under a given set of physical conditions, such as pressure, volume, temperature, or internal energy. Most mo ...
.
** Fission testing
***
Critical mass
In nuclear engineering, critical mass is the minimum mass of the fissile material needed for a sustained nuclear chain reaction in a particular setup. The critical mass of a fissionable material depends upon its nuclear properties (specific ...
experiments studying fissile material compositions, densities, geometries, and
reflectors. They can be subcritical or supercritical, in which case significant radiation fluxes can be produced. This type of test has resulted in several
criticality accident
A criticality accident is an accidental uncontrolled nuclear fission chain reaction. It is sometimes referred to as a critical excursion, critical power excursion, divergent chain reaction, or simply critical. Any such event involves the uninten ...
s.
*** Hydronuclear tests (hydrodynamical + nuclear) study nuclear materials under the conditions of explosive shock compression. They can create subcritical conditions, or supercritical conditions with yields ranging from negligible all the way up to a substantial fraction of full weapon yield. Any fission yield is considered banned by the CTBT.
** Fusion testing:
inertial confinement fusion
Inertial confinement fusion (ICF) is a fusion energy process that initiates nuclear fusion reactions by compressing and heating targets filled with fuel. The targets are small pellets, typically containing deuterium (2H) and tritium (3H).
Typical ...
experiments using lasers, like the
National Ignition Facility
The National Ignition Facility (NIF) is a laser-based inertial confinement fusion (ICF) research device, located at Lawrence Livermore National Laboratory in Livermore, California, United States. NIF's mission is to achieve fusion ignition wit ...
, or magnetized liners, like the
Z Pulsed Power Facility, or projectile compression. They study the plasma physics and
ignition of deuterium-tritium mixtures.
Subcritical tests executed by the United States include:
History
The first atomic weapons test was conducted near Alamogordo, New Mexico, on July 16, 1945, during the
Manhattan Project
The Manhattan Project was a research and development program undertaken during World War II to produce the first nuclear weapons. It was led by the United States in collaboration with the United Kingdom and Canada.
From 1942 to 1946, the ...
, and given the codename "
Trinity
The Trinity (, from 'threefold') is the Christian doctrine concerning the nature of God, which defines one God existing in three, , consubstantial divine persons: God the Father, God the Son (Jesus Christ) and God the Holy Spirit, thr ...
". The test was originally to confirm that the implosion-type
nuclear weapon design
Nuclear weapons design are physical, chemical, and engineering arrangements that cause the physics package of a nuclear weapon to detonate. There are three existing basic design types:
# Pure fission weapons are the simplest, least technically de ...
was feasible, and to give an idea of what the actual size and effects of a
nuclear explosion
A nuclear explosion is an explosion that occurs as a result of the rapid release of energy from a high-speed nuclear reaction. The driving reaction may be nuclear fission or nuclear fusion or a multi-stage cascading combination of the two, th ...
would be before they were used in combat against Japan. The test gave a good approximation of many of the explosion's effects, but did not give an appreciable understanding of
nuclear fallout
Nuclear fallout is residual radioactive material that is created by the reactions producing a nuclear explosion. It is initially present in the mushroom cloud, radioactive cloud created by the explosion, and "falls out" of the cloud as it is ...
, which was not well understood by the project scientists until well after the
atomic bombings of Hiroshima and Nagasaki
On 6 and 9 August 1945, the United States detonated two atomic bombs over the Japanese cities of Hiroshima and Nagasaki, respectively, during World War II. The aerial bombings killed between 150,000 and 246,000 people, most of whom were civili ...
.
The United States conducted six atomic tests before the Soviet Union developed their first atomic bomb (
RDS-1
The RDS-1 (), also known as Izdeliye 501 (device 501) and First Lightning (), was the nuclear bomb used in the Soviet Union's first nuclear weapon test. The United States assigned it the code-name Joe-1, in reference to Joseph Stalin. It was de ...
) and tested it on August 29, 1949. Neither country had very many atomic weapons to spare at first, and so testing was relatively infrequent (when the US used two weapons for ''
Operation Crossroads
Operation Crossroads was a pair of nuclear weapon tests conducted by the United States at Bikini Atoll in mid-1946. They were the first nuclear weapon tests since Trinity on July 16, 1945, and the first detonations of nuclear devices sinc ...
'' in 1946, they were detonating over 20% of their current arsenal). By the 1950s the United States had established a dedicated test site on its own territory (
Nevada Test Site
The Nevada National Security Sites (N2S2 or NNSS), popularized as the Nevada Test Site (NTS) until 2010, is a reservation of the United States Department of Energy located in the southeastern portion of Nye County, Nevada, about northwest of ...
) and was also using a site in the
Marshall Islands
The Marshall Islands, officially the Republic of the Marshall Islands, is an island country west of the International Date Line and north of the equator in the Micronesia region of the Northwestern Pacific Ocean.
The territory consists of 29 c ...
(
Pacific Proving Grounds
The Pacific Proving Grounds was the name given by the United States government to a number of sites in the Marshall Islands and a few other sites in the Pacific Ocean at which it conducted nuclear testing between 1946 and 1962. The U.S. tested ...
) for extensive atomic and nuclear testing.
The early tests were used primarily to discern the military effects of atomic weapons (''Crossroads'' had involved the effect of atomic weapons on a navy, and how they functioned underwater) and to test new weapon designs. During the 1950s, these included new hydrogen bomb designs, which were tested in the Pacific, and also new and improved fission weapon designs. The Soviet Union also began testing on a limited scale, primarily in
Kazakhstan
Kazakhstan, officially the Republic of Kazakhstan, is a landlocked country primarily in Central Asia, with a European Kazakhstan, small portion in Eastern Europe. It borders Russia to the Kazakhstan–Russia border, north and west, China to th ...
. During the later phases of the
Cold War
The Cold War was a period of global Geopolitics, geopolitical rivalry between the United States (US) and the Soviet Union (USSR) and their respective allies, the capitalist Western Bloc and communist Eastern Bloc, which lasted from 1947 unt ...
, both countries developed accelerated testing programs, testing many hundreds of bombs over the last half of the 20th century.

Atomic and nuclear tests can involve many hazards. Some of these were illustrated in the US
Castle Bravo
Castle Bravo was the first in a series of high-yield thermonuclear weapon design tests conducted by the United States at Bikini Atoll, Marshall Islands, as part of ''Operation Castle''. Detonated on 1 March 1954, the device remains the most powe ...
test in 1954. The weapon design tested was a new form of hydrogen bomb, and the scientists underestimated how vigorously some of the weapon materials would react. As a result, the explosion—with a
yield of 15
Mt—was over twice what was predicted. Aside from this problem, the weapon also generated a large amount of radioactive
nuclear fallout
Nuclear fallout is residual radioactive material that is created by the reactions producing a nuclear explosion. It is initially present in the mushroom cloud, radioactive cloud created by the explosion, and "falls out" of the cloud as it is ...
, more than had been anticipated, and a change in the weather pattern caused the fallout to spread in a direction not cleared in advance. The fallout plume spread high levels of radiation for over , contaminating populated islands in nearby atoll formations. Though they were soon evacuated, many of the islands' inhabitants suffered from radiation burns and later from other effects such as increased cancer rate and birth defects, as did the crew of the Japanese fishing boat ''
Daigo Fukuryū Maru
was a Japanese tuna fishing boat with a crew of 23 men which was contaminated by nuclear fallout from the United States Castle Bravo thermonuclear weapon test at Bikini Atoll on March 1, 1954.
The crew suffered acute radiation syndrome (ARS) ...
''. One crewman died from radiation sickness after returning to port, and it was feared that the radioactive fish they had been carrying had made it into the Japanese food supply.

Castle Bravo was the worst US nuclear accident, but many of its component problems—unpredictably large yields, changing weather patterns, unexpected fallout
contamination
Contamination is the presence of a constituent, impurity, or some other undesirable element that renders something unsuitable, unfit or harmful for the physical body, natural environment, workplace, etc.
Types of contamination
Within the scien ...
of populations and the food supply—occurred during other atmospheric nuclear weapons tests by other countries as well. Concerns over worldwide fallout rates eventually led to the
Partial Test Ban Treaty
The Partial Test Ban Treaty (PTBT), formally known as the 1963 Treaty Banning Nuclear Weapon Tests in the Atmosphere, in Outer Space and Under Water, prohibited all nuclear weapons testing, test detonations of nuclear weapons except for those co ...
in 1963, which limited signatories to underground testing. Not all countries stopped atmospheric testing, but because the United States and the Soviet Union were responsible for roughly 86% of all nuclear tests, their compliance cut the overall level substantially. France continued atmospheric testing until 1974, and China until 1980.
A tacit moratorium on testing was in effect from 1958 to 1961 and ended with a series of Soviet tests in late 1961, including the
Tsar Bomba
The Tsar Bomba (code name: ''Ivan'' or ''Vanya''), also known by the alphanumerical designation "AN602", was a Thermonuclear weapon, thermonuclear aerial bomb, and by far the most powerful nuclear weapon ever created and tested. The Soviet phy ...
, the largest nuclear weapon ever tested. The United States responded in 1962 with
Operation Dominic
Operation Dominic was a series of 31 nuclear test explosions ("shots") with a total yield conducted in 1962 by the United States in the Pacific. This test series was scheduled quickly, in order to respond in kind to the Soviet resumption of t ...
, involving dozens of tests, including the explosion of a missile launched from a submarine.
Almost all new nuclear powers have announced their possession of nuclear weapons with a nuclear test. The only acknowledged nuclear power that claims never to have conducted a test was South Africa (although see
Vela incident
The Vela incident was an unidentified double flash of light detected by an American Vela Hotel satellite on 22 September 1979 near the South African territory of Prince Edward Islands in the Indian Ocean, roughly midway between Africa and Antar ...
), which has since dismantled all of its weapons. Israel is widely thought to possess a sizable nuclear arsenal, though it has never tested, unless they were involved in Vela. Experts disagree on whether states can have reliable nuclear arsenals—especially ones using advanced warhead designs, such as hydrogen bombs and miniaturized weapons—without testing, though all agree that it is very unlikely to develop significant nuclear innovations without testing. One other approach is to use
supercomputer
A supercomputer is a type of computer with a high level of performance as compared to a general-purpose computer. The performance of a supercomputer is commonly measured in floating-point operations per second (FLOPS) instead of million instruc ...
s to conduct "virtual" testing, but codes need to be validated against test data.
There have been many attempts to limit the number and size of nuclear tests; the most far-reaching is the
Comprehensive Test Ban Treaty
The Comprehensive Nuclear-Test-Ban Treaty (CTBT) is a multilateral treaty to ban nuclear weapons test explosions and any other nuclear explosions, for both civilian and military purposes, in all environments. It was adopted by the United Nati ...
of 1996, which has not, , been ratified by eight of the "
Annex 2 countries" required for it to take effect, including the United States. Nuclear testing has since become a controversial issue in the United States, with a number of politicians saying that future testing might be necessary to maintain the aging warheads from the
Cold War
The Cold War was a period of global Geopolitics, geopolitical rivalry between the United States (US) and the Soviet Union (USSR) and their respective allies, the capitalist Western Bloc and communist Eastern Bloc, which lasted from 1947 unt ...
. Because nuclear testing is seen as furthering nuclear arms development, many are opposed to future testing as an acceleration of the arms race.
In
total nuclear test megatonnage, from 1945 to 1992, 520 atmospheric nuclear explosions (including eight underwater) were conducted with a total yield of 545
megatons,
with a peak occurring in 1961–1962, when 340 megatons were detonated in the atmosphere by the United States and
Soviet Union
The Union of Soviet Socialist Republics. (USSR), commonly known as the Soviet Union, was a List of former transcontinental countries#Since 1700, transcontinental country that spanned much of Eurasia from 1922 until Dissolution of the Soviet ...
, while the estimated number of underground nuclear tests conducted in the period from 1957 to 1992 was 1,352 explosions with a total yield of 90 Mt.
Image: Trinity shot color.jpg, The first atomic test, "Trinity
The Trinity (, from 'threefold') is the Christian doctrine concerning the nature of God, which defines one God existing in three, , consubstantial divine persons: God the Father, God the Son (Jesus Christ) and God the Holy Spirit, thr ...
", took place on July 16, 1945.
Image: Sedan Plowshare Crater.jpg, The Sedan test of 1962 was an experiment by the United States in using nuclear weapons to excavate large amounts of earth.
File:330-PS-3256 (45898 AC) (17204655228).jpg, Kytoon
A kytoon or kite balloon is a tethered aircraft which obtains some of its lift dynamically as a heavier-than-air kite and the rest aerostatically as a lighter-than-air balloon. The word is a portmanteau of kite and balloon.
The primary advantage ...
balloons were used on Indian Springs Air Force Base, Nevada, April 20, 1952, to get exact weather information during atomic test periods.
Yield
The
yields of atomic bombs and thermonuclear are typically measured in different amounts. Thermonuclear bombs can be hundreds or thousands of times stronger than their atomic counterparts. Due to this, thermonuclear bombs' yields are usually expressed in megatons which is about the equivalent of 1,000,000 tons of TNT. In contrast, atomic bombs' yields are typically measured in kilotons, or about 1,000 tons of TNT.
In US context, it was decided during the Manhattan Project that yield measured in tons of TNT equivalent could be imprecise. This comes from the range of experimental values of the energy content of TNT, ranging from . There is also the issue of which ton to use, as short tons, long tons, and metric tonnes all have different values. It was therefore decided that one kiloton would be equivalent to .
Nuclear testing by country
The nuclear powers have conducted more than 2,000 nuclear test explosions (numbers are approximate, as some test results have been disputed):
* United States: 1,054 tests by official count (involving at least 1,149 devices). 219 were atmospheric tests as defined by the
CTBT. These tests include 904 at the
Nevada Test Site
The Nevada National Security Sites (N2S2 or NNSS), popularized as the Nevada Test Site (NTS) until 2010, is a reservation of the United States Department of Energy located in the southeastern portion of Nye County, Nevada, about northwest of ...
, 106 at the
Pacific Proving Grounds
The Pacific Proving Grounds was the name given by the United States government to a number of sites in the Marshall Islands and a few other sites in the Pacific Ocean at which it conducted nuclear testing between 1946 and 1962. The U.S. tested ...
and other locations in the Pacific, 3 in the South Atlantic Ocean, and 17 other tests taking place in
Amchitka Alaska
Alaska ( ) is a non-contiguous U.S. state on the northwest extremity of North America. Part of the Western United States region, it is one of the two non-contiguous U.S. states, alongside Hawaii. Alaska is also considered to be the north ...
,
Colorado
Colorado is a U.S. state, state in the Western United States. It is one of the Mountain states, sharing the Four Corners region with Arizona, New Mexico, and Utah. It is also bordered by Wyoming to the north, Nebraska to the northeast, Kansas ...
,
Mississippi
Mississippi ( ) is a U.S. state, state in the Southeastern United States, Southeastern and Deep South regions of the United States. It borders Tennessee to the north, Alabama to the east, the Gulf of Mexico to the south, Louisiana to the s ...
,
New Mexico
New Mexico is a state in the Southwestern United States, Southwestern region of the United States. It is one of the Mountain States of the southern Rocky Mountains, sharing the Four Corners region with Utah, Colorado, and Arizona. It also ...
and
Nevada
Nevada ( ; ) is a landlocked state in the Western United States. It borders Oregon to the northwest, Idaho to the northeast, California to the west, Arizona to the southeast, and Utah to the east. Nevada is the seventh-most extensive, th ...
outside the NNSS (see
Nuclear weapons and the United States for details). 24 tests are classified as British tests held at the NTS. There were 35 Plowshare detonations and 7 Vela Uniform tests; 88 tests were safety experiments and 4 were transportation/storage tests. Motion pictures were made of the explosions, later used to validate computer simulation predictions of explosions. ''
United States' table data''.
* Soviet Union: 715 tests (involving 969 devices) by official count, plus 13 unnumbered test failures. Most were at their Southern Test Area at
Semipalatinsk Test Site
The Semipalatinsk Test Site or Semipalatinsk-21 (; ), also known as "The Polygon", was the primary testing venue for the Soviet Union's nuclear weapons. It is located in Zhanasemey District, Abai Region, Kazakhstan, south of the valley of the Ir ...
and the Northern Test Area at
Novaya Zemlya
Novaya Zemlya (, also , ; , ; ), also spelled , is an archipelago in northern Russia. It is situated in the Arctic Ocean, in the extreme northeast of Europe, with Cape Flissingsky, on the northern island, considered the extreme points of Europe ...
. Others include rocket tests and peaceful-use explosions at various sites in
Russia
Russia, or the Russian Federation, is a country spanning Eastern Europe and North Asia. It is the list of countries and dependencies by area, largest country in the world, and extends across Time in Russia, eleven time zones, sharing Borders ...
,
Kazakhstan
Kazakhstan, officially the Republic of Kazakhstan, is a landlocked country primarily in Central Asia, with a European Kazakhstan, small portion in Eastern Europe. It borders Russia to the Kazakhstan–Russia border, north and west, China to th ...
,
Turkmenistan
Turkmenistan is a landlocked country in Central Asia bordered by Kazakhstan to the northwest, Uzbekistan to the north, east and northeast, Afghanistan to the southeast, Iran to the south and southwest and the Caspian Sea to the west. Ash ...
,
Uzbekistan
, image_flag = Flag of Uzbekistan.svg
, image_coat = Emblem of Uzbekistan.svg
, symbol_type = Emblem of Uzbekistan, Emblem
, national_anthem = "State Anthem of Uzbekistan, State Anthem of the Republ ...
and
Ukraine
Ukraine is a country in Eastern Europe. It is the List of European countries by area, second-largest country in Europe after Russia, which Russia–Ukraine border, borders it to the east and northeast. Ukraine also borders Belarus to the nor ...
. ''
Soviet Union's table data''.
* United Kingdom: 45 tests, of which 12 were in
Australia
Australia, officially the Commonwealth of Australia, is a country comprising mainland Australia, the mainland of the Australia (continent), Australian continent, the island of Tasmania and list of islands of Australia, numerous smaller isl ...
n territory, including three at the
Montebello Islands
The Montebello Islands, also rendered as the Monte Bello Islands, are an archipelago of around 174 small islands, about 92 of which are named, lying north of Barrow Island (Western Australia), Barrow Island and off the Pilbara region of W ...
and nine in mainland
South Australia
South Australia (commonly abbreviated as SA) is a States and territories of Australia, state in the southern central part of Australia. With a total land area of , it is the fourth-largest of Australia's states and territories by area, which in ...
at
Maralinga and Emu Field, 9 at
Christmas Island (Kiritimati) in the
Pacific Ocean
The Pacific Ocean is the largest and deepest of Earth's five Borders of the oceans, oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean, or, depending on the definition, to Antarctica in the south, and is ...
, plus 24 in the United States at the Nevada Test Site
as part of joint test series). 43 safety tests (the ''Vixen'' series) are not included in that number, though safety experiments by other countries are. ''
The United Kingdom's summary table''.
* France: 210 tests by official count (50 atmospheric, 160 underground), four atomic atmospheric tests at
C.S.E.M. near
Reggane
Reggane (from Berber "Argan"; ) is a town and commune, and the capital of Reggane District, in Adrar Province, central Algeria. Reggane lies in the Sahara Desert near an oasis. According to the 2008 census it has a population of 20,402, up from 14 ...
, 13 atomic underground tests at
C.E.M.O. near
In Ekker in the French
Algeria
Algeria, officially the People's Democratic Republic of Algeria, is a country in the Maghreb region of North Africa. It is bordered to Algeria–Tunisia border, the northeast by Tunisia; to Algeria–Libya border, the east by Libya; to Alger ...
n Sahara, and nuclear atmospheric and underground tests at and around Fangataufa and Moruroa Atolls in French Polynesia. Four of the In Ekker tests are counted as peaceful use, as they were reported as part of the CET's APEX (Application pacifique des expérimentations nucléaires, “Peaceful Application of Nuclear Experiments”), and given alternate names. ''France and weapons of mass destruction, France's summary table''.
* China: 45 tests (23 atmospheric and 22 underground), at Lop Nur Nuclear Weapons Test Base, in Malan, Xinjiang, Malan, Xinjiang There are two additional unnumbered failed tests. ''China's nuclear test series, China's summary table''.
* India: Six underground explosions (including the first one in 1974), at Pokhran. ''India's nuclear testing series, India's summary table''.
* Pakistan: Six underground explosions at Ras Koh Hills and the Chagai District. ''Pakistan's nuclear testing series, Pakistan's summary table''.
* North Korea: North Korea is the only country in the world that still tests nuclear weapons, and their tests have caused 2017-2018 North Korea crisis, escalating tensions between them and the United States. Their most recent nuclear test was on 2017 North Korean nuclear test, September 3, 2017. ''North Korea's nuclear testing series, North Korea's summary table''
There may also have been at least three alleged but unacknowledged nuclear explosions (see List of nuclear tests#Alleged tests, list of alleged nuclear tests) including the
Vela incident
The Vela incident was an unidentified double flash of light detected by an American Vela Hotel satellite on 22 September 1979 near the South African territory of Prince Edward Islands in the Indian Ocean, roughly midway between Africa and Antar ...
.
From the first nuclear test in 1945 until tests by Pakistan in 1998, there was never a period of more than 22 months with no nuclear testing. June 1998 to October 2006 was the longest period since 1945 with no acknowledged nuclear tests.
A summary table of all the nuclear testing that has happened since 1945 is here: Worldwide nuclear testing counts and summary.
Global fallout

Nuclear weapons testing did not produce scenarios like nuclear winter as a result of a scenario of a concentrated number of nuclear explosions in a nuclear holocaust, but the thousands of tests, hundreds being atmospheric, did nevertheless produce a global fallout that peaked in 1963 (the bomb pulse), reaching levels of about 0.15 mSv per year worldwide, or about 7% of average background radiation dose from all sources, and has slowly decreased since,
with natural environmental radiation levels being around 1 mSv. This global fallout was one of the main drivers for the ban of nuclear weapons testing, particularly atmospheric testing. It has been estimated that by 2020 up to 2.4 million people have died as a result of nuclear weapons testing.
Criticism
Nuclear arms tests have been criticized for its arms race
and its fallout,
with a potentially global fallout.
Nuclear weapons tests have been criticized by anti-nuclear movement, anti-nuclear activists as nuclear imperialism, colonialism,
ecocide, environmental racism and nuclear genocide.
The movement gained particularly in the 1960s and in the 1980s again.
The international day "End Nuclear Tests Day" raises critical awareness annually.
Treaties against testing
There are many existing anti-nuclear explosion treaties, notably the Partial Nuclear Test Ban Treaty and the Comprehensive Nuclear-Test-Ban Treaty, Comprehensive Nuclear Test Ban Treaty. These treaties were proposed in response to growing international concerns about environmental damage among other risks. Nuclear testing involving humans also contributed to the formation of these treaties. Examples can be seen in the following articles:
* Desert Rock exercises
* Totskoye range nuclear tests
The Partial Nuclear Test Ban treaty makes it illegal to detonate any nuclear explosion anywhere except underground, in order to reduce atmospheric fallout. Most countries have signed and ratified the Partial Nuclear Test Ban, which went into effect in October 1963. Of the nuclear states, France, China, and North Korea have never signed the Partial Nuclear Test Ban Treaty.
The 1996 Comprehensive Nuclear-Test-Ban Treaty (CTBT) bans all nuclear explosions everywhere, including underground. For that purpose, the Comprehensive Nuclear-Test-Ban Treaty Organization Preparatory Commission, Preparatory Commission of the Comprehensive Nuclear-Test-Ban Treaty Organization is building an international monitoring system with 337 facilities located all over the globe. 85% of these facilities are already operational. , the CTBT has been signed by 183 States, of which 157 have also ratified. For the Treaty to enter into force it needs to be ratified by 44 specific nuclear technology-holder countries. These "Annex 2 States" participated in the negotiations on the CTBT between 1994 and 1996 and possessed nuclear power or research reactors at that time. The ratification of eight Annex 2 states is still missing: China, Egypt, Iran, Israel and the United States have signed but not ratified the Treaty; India, North Korea and Pakistan have not signed it.
The following is a list of the treaties applicable to nuclear testing:
Compensation for victims
Over 500 atmospheric nuclear weapons tests were conducted at various sites around the world from 1945 to 1980. As public awareness and concern mounted over the possible health hazards associated with exposure to the
nuclear fallout
Nuclear fallout is residual radioactive material that is created by the reactions producing a nuclear explosion. It is initially present in the mushroom cloud, radioactive cloud created by the explosion, and "falls out" of the cloud as it is ...
, various studies were done to assess the extent of the hazard. A Centers for Disease Control and Prevention/ National Cancer Institute study claims that nuclear fallout might have led to approximately 11,000 excess deaths, most caused by thyroid cancer linked to exposure to iodine-131.
* United States: Prior to March 2009, the US was the only nation to compensate nuclear test victims. Since the Radiation Exposure Compensation Act of 1990, more than $1.38 billion in compensation has been approved. The money is going to people who took part in the tests, notably at the
Nevada Test Site
The Nevada National Security Sites (N2S2 or NNSS), popularized as the Nevada Test Site (NTS) until 2010, is a reservation of the United States Department of Energy located in the southeastern portion of Nye County, Nevada, about northwest of ...
, and to others exposed to the radiation. As of 2017, the US government refused to pay for the medical care of troops who associate their health problems with the construction of Runit Dome in the Marshall Islands.
* France: In March 2009, the French Government offered to compensate victims for the first time and legislation is being drafted which would allow payments to people who suffered health problems related to the tests.
The payouts would be available to victims' descendants and would include Algerians, who were exposed to nuclear testing in the Sahara in 1960. Victims say the eligibility requirements for compensation are too narrow.
* United Kingdom: There is no formal British government compensation program. Nearly 1,000 veterans of Christmas Island (Kiritimati)#Nuclear bomb tests, Christmas Island nuclear tests in the 1950s are engaged in legal action against the Ministry of Defense for negligence. They say they suffered health problems and were not warned of potential dangers before the experiments.
* Russia: Decades later, Russia offered compensation to veterans who were part of the Totskoye nuclear exercise, 1954 Totsk test. There was no compensation to civilians sickened by the Totsk test. Anti-nuclear groups say there has been no government compensation for other nuclear tests.
* China: China has undertaken highly secretive atomic tests in remote deserts in a Central Asian border province. Anti-nuclear activists say there is no known government program for compensating victims.
Milestone nuclear explosions
The following list is of milestone nuclear explosions. In addition to the
atomic bombings of Hiroshima and Nagasaki
On 6 and 9 August 1945, the United States detonated two atomic bombs over the Japanese cities of Hiroshima and Nagasaki, respectively, during World War II. The aerial bombings killed between 150,000 and 246,000 people, most of whom were civili ...
, 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 trinitrotoluene, TNT (see TNT equivalent). List of nuclear tests#Alleged tests, Putative tests (like
Vela incident
The Vela incident was an unidentified double flash of light detected by an American Vela Hotel satellite on 22 September 1979 near the South African territory of Prince Edward Islands in the Indian Ocean, roughly midway between Africa and Antar ...
) have not been included.
;Note
* "Staged" refers to whether it was a "true"
thermonuclear weapon
A thermonuclear weapon, fusion weapon or hydrogen bomb (H-bomb) is a second-generation nuclear weapon design. Its greater sophistication affords it vastly greater destructive power than first-generation nuclear bombs, a more compact size, a lowe ...
of the so-called Teller–Ulam configuration or simply a form of a boosted fission weapon. For a more complete list of nuclear test series, see List of nuclear tests. Some exact yield estimates, such as that of the
Tsar Bomba
The Tsar Bomba (code name: ''Ivan'' or ''Vanya''), also known by the alphanumerical designation "AN602", was a Thermonuclear weapon, thermonuclear aerial bomb, and by far the most powerful nuclear weapon ever created and tested. The Soviet phy ...
and the tests by India and Pakistan in 1998, are somewhat contested among specialists.
See also
*
* (in Nevada in the US)
*
*
*
*
* '
* (including nuclear weapons accidents)
*
*
*
*
* :Nuclear test sites, Nuclear test sites
*
*
*
*
*
*
* ' (documentary about nuclear weapon testing)
Explanatory notes
Citations
General and cited references
* Gusterson, Hugh. ''Nuclear Rites: A Weapons Laboratory at the End of the Cold War''. Berkeley, CA: University of California Press, 1996.
* Hacker, Barton C. ''Elements of Controversy: The Atomic Energy Commission and Radiation Safety in Nuclear Weapons Testing, 1947–1974''. Berkeley, CA: University of California Press, 1994.
* Rice, James. Downwind of the Atomic State: Atmospheric Testing and the Rise of the Risk Society. (New York University Press, 2023). https://nyupress.org/9781479815340/downwind-of-the-atomic-state/
* Schwartz, Stephen I. ''Atomic Audit: The Costs and Consequences of U.S. Nuclear Weapons''. Washington, D.C.: Brookings Institution Press, 1998.
* Weart, Spencer R. ''Nuclear Fear: A History of Images''. Cambridge, MA: Harvard University Press, 1985.
External links
Federation of American Scientists
Preparatory Commission for the Comprehensive Nuclear-Test-Ban-Treaty OrganizationNuclearFiles.org*
Bulletin of the Atomic ScientistsAlsos Digital Library for Nuclear IssuesAtomic Bomb website and nuclear weapon testing articlesThe Woodrow Wilson Center's Nuclear Proliferation International History Project
{{DEFAULTSORT:Nuclear Weapons Testing
Nuclear weapons testing,
Nuclear weapons, Testing