Nuclear weapons testing

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The mushroom cloud from the Castle Bravo thermonuclear weapon test in 1954, the largest nuclear weapons test ever conducted by the United States

Nuclear weapons tests are experiments carried out to determine the performance, yield, and effects of nuclear weapons. Testing nuclear weapons offers practical information about how the weapons function, how detonations are affected by different conditions, and how personnel, structures, and equipment are affected when subjected to nuclear explosions. However, nuclear testing has often been used as an indicator of scientific and military strength. Many tests have been overtly political in their intention; most nuclear weapons states publicly declared their nuclear status through a nuclear test.

The first nuclear device was detonated as a test by the United States at the Trinity site in New Mexico on July 16, 1945, with a yield approximately equivalent to 20 kilotons of TNT. The first thermonuclear weapon technology test of an engineered device, codenamed Ivy Mike, was tested at the Enewetak Atoll in the Marshall Islands on November 1, 1952 (local date), also by the United States. The largest nuclear weapon ever tested was the Tsar Bomba of the Soviet Union at Novaya Zemlya on October 30, 1961, with the largest yield ever seen, an estimated 50–58 megatons.

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. France continued atmospheric testing until 1974, and China continued until 1980. Neither has signed the treaty.[1]

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 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 and Pakistan last tested nuclear weapons in 1998. North Korea conducted nuclear tests in 2006, 2009, 2013, 2016, and 2017. The most recent confirmed nuclear test occurred in September 2017 in North Korea.


Four major types of nuclear testing: 1. atmospheric, 2. underground, 3. exoatmospheric, and 4. underwater

Nuclear weapons tests have historically been divided into four categories reflecting the medium or location of the test.

  • Atmospheric testing designates explosions that take place in the atmosphere. Generally, these have occurred as devices detonated on towers, 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 bombs (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 can generate large amounts of nuclear fallout due to irradiation of the debris (particularly with neutron radiation) as well as radioactive contamination 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 refers to nuclear tests conducted under the surface of the earth, at varying depths. Underground nuclear testing made up the majority of nuclear tests by the United States and the Soviet Union during the Cold War; 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 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.[2] 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 refers to nuclear tests conducted above the atmosphere. The test devices are lifted on rockets. These high-altitude nuclear explosions can generate a nuclear electromagnetic pulse (NEMP) when they occur in the ionosphere, 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), or to evaluate potential sea-based nuclear weapons (such as nuclear torpedoes 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[edit]

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.[3]

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 has separate items for Cremino and Caerphilly, which together constitute a single test), the lists are of explosions.


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 stopped all nuclear testing among signatories.
  • Peaceful nuclear explosions 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[edit]

Subcritical experiment at the Nevada National Security Site

Computer simulation 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 and maintenance.[4][5] A theme has generally been that even though simulations cannot fully replace physical testing, they can reduce the amount of it that is necessary.[6]

Hydronuclear tests 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.[7]

Critical mass experiments determine the quantity of fissile material required for criticality with a variety of fissile material compositions, densities, shapes, 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 accidents.

Subcritical (or cold) tests are any type of tests involving nuclear materials and possibly high explosives (like those mentioned above) that purposely result in no yield. The name refers to the lack of creation of a critical mass of fissile material. They are the only type of tests allowed under the interpretation of the Comprehensive Nuclear-Test-Ban Treaty tacitly agreed to by the major atomic powers.[8][9] Subcritical tests continue to be performed by the United States, Russia, and the People's Republic of China, at least.[10][11]

Subcritical tests executed by the United States include:[12][13][14]

Subcritical Tests
Name Date Time (UT[a]) Location Elevation + Height Notes
A series of 50 tests January 1, 1960 Los Alamos National Lab Test Area 49 35°49′22″N 106°18′08″W / 35.82289°N 106.30216°W / 35.82289; -106.30216 2,183 metres (7,162 ft) and 20 metres (66 ft) Series of 50 tests during US/USSR joint nuclear test ban.[15]
Odyssey NTS Area U1a 37°00′41″N 116°03′35″W / 37.01139°N 116.05983°W / 37.01139; -116.05983 1,222 metres (4,009 ft) and 190 metres (620 ft)
Trumpet NTS Area U1a-102D 37°00′40″N 116°03′31″W / 37.01099°N 116.05848°W / 37.01099; -116.05848 1,222 metres (4,009 ft) and 190 metres (620 ft)
Kismet March 1, 1995 NTS Area U1a 37°00′41″N 116°03′35″W / 37.01139°N 116.05983°W / 37.01139; -116.05983 1,222 metres (4,009 ft) and 293 metres (961 ft) Kismet was a proof of concept for modern hydronuclear tests; it did not contain any SNM (Special Nuclear Material—plutonium or uranium).
Rebound July 2, 1997 10:—:— NTS Area U1a 37°00′41″N 116°03′35″W / 37.01139°N 116.05983°W / 37.01139; -116.05983 1,222 metres (4,009 ft) and 293 metres (961 ft) Provided information on the behavior of new plutonium alloys compressed by high-pressure shock waves; same as Stagecoach but for the age of the alloys.
Holog September 18, 1997 NTS Area U1a.101A 37°00′37″N 116°03′32″W / 37.01036°N 116.05888°W / 37.01036; -116.05888 1,222 metres (4,009 ft) and 290 metres (950 ft) Holog and Clarinet may have switched locations.
Stagecoach March 25, 1998 NTS Area U1a 37°00′41″N 116°03′35″W / 37.01139°N 116.05983°W / 37.01139; -116.05983 1,222 metres (4,009 ft) and 290 metres (950 ft) Provided information on the behavior of aged (up to 40 years) plutonium alloys compressed by high-pressure shock waves.
Bagpipe September 26, 1998 NTS Area U1a.101B 37°00′37″N 116°03′32″W / 37.01021°N 116.05886°W / 37.01021; -116.05886 1,222 metres (4,009 ft) and 290 metres (950 ft)
Cimarron December 11, 1998 NTS Area U1a 37°00′41″N 116°03′35″W / 37.01139°N 116.05983°W / 37.01139; -116.05983 1,222 metres (4,009 ft) and 290 metres (950 ft) Plutonium surface ejecta studies.
Clarinet February 9, 1999 NTS Area U1a.101C 37°00′36″N 116°03′32″W / 37.01003°N 116.05898°W / 37.01003; -116.05898 1,222 metres (4,009 ft) and 290 metres (950 ft) Holog and Clarinet may have switched places on the map.
Oboe September 30, 1999 NTS Area U1a.102C 37°00′39″N 116°03′32″W / 37.01095°N 116.05877°W / 37.01095; -116.05877 1,222 metres (4,009 ft) and 290 metres (950 ft)
Oboe 2 November 9, 1999 NTS Area U1a.102C 37°00′39″N 116°03′32″W / 37.01095°N 116.05877°W / 37.01095; -116.05877 1,222 metres (4,009 ft) and 290 metres (950 ft)
Oboe 3 February 3, 2000 NTS Area U1a.102C 37°00′39″N 116°03′32″W / 37.01095°N 116.05877°W / 37.01095; -116.05877 1,222 metres (4,009 ft) and 290 metres (950 ft)
Thoroughbred March 22, 2000 NTS Area U1a 37°00′41″N 116°03′35″W / 37.01139°N 116.05983°W / 37.01139; -116.05983 1,222 metres (4,009 ft) and 290 metres (950 ft) Plutonium surface ejecta studies, followup to Cimarron.
Oboe 4 April 6, 2000 NTS Area U1a.102C 37°00′39″N 116°03′32″W / 37.01095°N 116.05877°W / 37.01095; -116.05877 1,222 metres (4,009 ft) and 290 metres (950 ft)
Oboe 5 August 18, 2000 NTS Area U1a.102C 37°00′39″N 116°03′32″W / 37.01095°N 116.05877°W / 37.01095; -116.05877 1,222 metres (4,009 ft) and 290 metres (950 ft)
Oboe 6 December 14, 2000 NTS Area U1a.102C 37°00′39″N 116°03′32″W / 37.01095°N 116.05877°W / 37.01095; -116.05877 1,222 metres (4,009 ft) and 290 metres (950 ft)
Oboe 8 September 26, 2001 NTS Area U1a.102C 37°00′39″N 116°03′32″W / 37.01095°N 116.05877°W / 37.01095; -116.05877 1,222 metres (4,009 ft) and 290 metres (950 ft)
Oboe 7 December 13, 2001 NTS Area U1a.102C 37°00′39″N 116°03′32″W / 37.01095°N 116.05877°W / 37.01095; -116.05877 1,222 metres (4,009 ft) and 290 metres (950 ft)
Oboe 9 June 7, 2002 21:46:— NTS Area U1a.102C 37°00′39″N 116°03′32″W / 37.01095°N 116.05877°W / 37.01095; -116.05877 1,222 metres (4,009 ft) and 290 metres (950 ft)
Mario August 29, 2002 19:00:— NTS Area U1a 37°00′41″N 116°03′35″W / 37.01139°N 116.05983°W / 37.01139; -116.05983 1,222 metres (4,009 ft) and 290 metres (950 ft) Plutonium surface studies (optical analysis of spall). Used wrought plutonium from Rocky Flats.
Rocco September 26, 2002 19:00:— NTS Area U1a 37°00′41″N 116°03′35″W / 37.01139°N 116.05983°W / 37.01139; -116.05983 1,222 metres (4,009 ft) and 290 metres (950 ft) Plutonium surface studies (optical analysis of spall), followup to Mario. Used cast plutonium from Los Alamos.
Piano September 19, 2003 20:44:— NTS Area U1a.102C 37°00′39″N 116°03′32″W / 37.01095°N 116.05877°W / 37.01095; -116.05877 1,222 metres (4,009 ft) and 290 metres (950 ft)
Armando May 25, 2004 NTS Area U1a 37°00′41″N 116°03′35″W / 37.01139°N 116.05983°W / 37.01139; -116.05983 1,222 metres (4,009 ft) and 290 metres (950 ft) Plutonium spall measurements using x-ray analysis.[b]
Step Wedge April 1, 2005 NTS Area U1a 37°00′41″N 116°03′35″W / 37.01139°N 116.05983°W / 37.01139; -116.05983 1,222 metres (4,009 ft) and 190 metres (620 ft) April–May 2005, a series of mini-hydronuclear experiments interpreting Armando results.
Unicorn August 31, 2006 01:00:— NTS Area U6c 36°59′12″N 116°02′38″W / 36.98663°N 116.0439°W / 36.98663; -116.0439 1,222 metres (4,009 ft) and 190 metres (620 ft) "...confirm nuclear performance of the W88 warhead with a newly-manufactured pit." Early pit studies.
Thermos January 1, 2007 NTS Area U1a 37°00′41″N 116°03′35″W / 37.01139°N 116.05983°W / 37.01139; -116.05983 1,222 metres (4,009 ft) and 190 metres (620 ft) February 6 – May 3, 2007, 12 mini-hydronuclear experiments in thermos-sized flasks.
Bacchus September 16, 2010 NTS Area U1a.05? 37°00′41″N 116°03′35″W / 37.01139°N 116.05983°W / 37.01139; -116.05983 1,222 metres (4,009 ft) and 190 metres (620 ft)
Barolo A December 1, 2010 NTS Area U1a.05? 37°00′41″N 116°03′35″W / 37.01139°N 116.05983°W / 37.01139; -116.05983 1,222 metres (4,009 ft) and 190 metres (620 ft)
Barolo B February 2, 2011 NTS Area U1a.05? 37°00′41″N 116°03′35″W / 37.01139°N 116.05983°W / 37.01139; -116.05983 1,222 metres (4,009 ft) and 190 metres (620 ft)
Castor September 1, 2012 NTS Area U1a 37°00′41″N 116°03′35″W / 37.01139°N 116.05983°W / 37.01139; -116.05983 1,222 metres (4,009 ft) and 190 metres (620 ft) Not even a subcritical, contained no plutonium; a dress rehearsal for Pollux.
Pollux December 5, 2012 NTS Area U1a 37°00′41″N 116°03′35″W / 37.01139°N 116.05983°W / 37.01139; -116.05983 1,222 metres (4,009 ft) and 190 metres (620 ft) A subcritical test with a scaled-down warhead mockup.[c]
Leda June 15, 2014 NTS Area U1a 37°00′41″N 116°03′35″W / 37.01139°N 116.05983°W / 37.01139; -116.05983 1,222 metres (4,009 ft) and 190 metres (620 ft) Like Castor, the plutonium was replaced by a surrogate; this is a dress rehearsal for the later Lydia. The target was a weapons pit mock-up.[d]
Lydia ??-??-2015 NTS Area U1a 37°00′41″N 116°03′35″W / 37.01139°N 116.05983°W / 37.01139; -116.05983 1,222 metres (4,009 ft) and 190 metres (620 ft) Expected to be a plutonium subcritical test with a scaled-down warhead mockup.[citation needed]
Vega December 13, 2017 Nevada test site Plutonium subcritical test with a scaled down warhead mockup.[16]
Ediza February 13, 2019 NTS Area U1a 37°00′41″N 116°03′35″W / 37.01139°N 116.05983°W / 37.01139; -116.05983 Plutonium subcritical test designed to confirm supercomputer simulations for stockpile safety.[17]
Nightshade A November 2020 Nevada test site Plutonium subcritical test designed to measure ejecta emission.[18][19]


The Phoenix of Hiroshima (foreground) in Hong Kong Harbor in 1967, was involved in several famous anti-nuclear protest voyages against nuclear testing in the Pacific.
The 6,900-square-mile (18,000 km2) expanse of the Semipalatinsk Test Site (indicated in red), attached to Kurchatov (along the Irtysh river). The site comprised an area the size of Wales.[20]

The first atomic weapons test was conducted near Alamogordo, New Mexico, on July 16, 1945, during the Manhattan Project, and given the codename "Trinity". The test was originally to confirm that the implosion-type nuclear weapon design was feasible, and to give an idea of what the actual size and effects of a nuclear explosion would be before they were used in combat against Japan. While the test gave a good approximation of many of the explosion's effects, it did not give an appreciable understanding of nuclear fallout, which was not well understood by the project scientists until well after the atomic bombings of Hiroshima and Nagasaki.

The United States conducted six atomic tests before the Soviet Union developed their first atomic bomb (RDS-1) 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 U.S. used two weapons for Operation Crossroads in 1946, they were detonating over 20% of their current arsenal). However, by the 1950s the United States had established a dedicated test site on its own territory (Nevada Test Site) and was also using a site in the Marshall Islands (Pacific Proving Grounds) 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. During the later phases of the Cold War, though, both countries developed accelerated testing programs, testing many hundreds of bombs over the last half of the 20th century.

In 1954 the Castle Bravo fallout plume spread dangerous levels of radiation over an area over 100 miles (160 km) long, including inhabited islands.

Atomic and nuclear tests can involve many hazards. Some of these were illustrated in the U.S. Castle Bravo 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, 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 100 miles (160 km), contaminating a number of 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. 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.

Because of concerns about worldwide fallout levels, the Partial Test Ban Treaty was signed in 1963. Above are the per capita thyroid doses (in rads) in the continental United States resulting from all exposure routes from all atmospheric nuclear tests conducted at the Nevada Test Site from 1951 to 1962.

Castle Bravo was the worst U.S. nuclear accident, but many of its component problems—unpredictably large yields, changing weather patterns, unexpected fallout contamination 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 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 largest nuclear weapon ever tested. The United States responded in 1962 with Operation Dominic, 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), 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 supercomputers 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 of 1996, which has not, as of 2013, 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. 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,[21] with a peak occurring in 1961–1962, when 340 megatons were detonated in the atmosphere by the United States and Soviet Union,[22] 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.[21]


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 900 to 1,100 calories per gram (3,800 to 4,600 kJ/g). 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 1.0×1012 calories (4.2×1012 kJ).[23]

Nuclear testing by country[edit]

Over 2,000 nuclear tests have been conducted in over a dozen different sites around the world. Red Russia/Soviet Union, blue France, light blue United States, violet Britain, yellow China, orange India, brown Pakistan, green North Korea, and light green (territories exposed to nuclear bombs). The black dot indicates the location of the Vela incident.
"Baker Shot", part of Operation Crossroads, a nuclear test by the United States at Bikini Atoll in 1946

The nuclear powers have conducted more than 2,000 nuclear test explosions (numbers are approximate, as some test results have been disputed):

There may also have been at least three alleged but unacknowledged nuclear explosions (see list of alleged nuclear tests) including the Vela incident.

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.

Graph of nuclear testing
Graph of nuclear testing

Treaties against testing[edit]

There are many existing anti-nuclear explosion treaties, notably the Partial Nuclear Test Ban Treaty and the 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:

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.[33]

The 1996 Comprehensive Nuclear-Test-Ban Treaty (CTBT) bans all nuclear explosions everywhere, including underground. For that purpose, the 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.[34] As of May 2012, the CTBT has been signed by 183 States, of which 157 have also ratified. However, 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.[35]

The following is a list of the treaties applicable to nuclear testing:

Name Agreement date In force date In effect today? Notes
Unilateral USSR ban March 31, 1958 March 31, 1958 no USSR unilaterally stops testing provided the West does as well.
Bilateral testing ban August 2, 1958 October 31, 1958 no USA agrees; ban begins on 31 October 1958, 3 November 1958 for the Soviets, and lasts until abrogated by a USSR test on 1 September 1961.
Antarctic Treaty System December 1, 1959 June 23, 1961 yes Bans testing of all kinds in Antarctica.
Partial Nuclear Test Ban Treaty (PTBT) August 5, 1963 October 10, 1963 yes Ban on all but underground testing.
Outer Space Treaty January 27, 1967 October 10, 1967 yes Bans testing on the moon and other celestial bodies.
Treaty of Tlatelolco February 14, 1967 April 22, 1968 yes Bans testing in South America and the Caribbean Sea Islands.
Nuclear Non-proliferation Treaty January 1, 1968 March 5, 1970 yes Bans the proliferation of nuclear technology to non-nuclear nations.
Seabed Arms Control Treaty February 11, 1971 May 18, 1972 yes Bans emplacement of nuclear weapons on the ocean floor outside territorial waters.
Strategic Arms Limitation Treaty (SALT I) January 1, 1972 no A five-year ban on installing launchers.
Anti-Ballistic Missile Treaty May 26, 1972 August 3, 1972 no Restricts ABM development; additional protocol added in 1974; abrogated by the US in 2002.
Agreement on the Prevention of Nuclear War June 22, 1973 June 22, 1973 yes Promises to make all efforts to promote security and peace.
Threshold Test Ban Treaty July 1, 1974 December 11, 1990 yes Prohibits higher than 150 kt for underground testing.
Peaceful Nuclear Explosions Treaty (PNET) January 1, 1976 December 11, 1990 yes Prohibits higher than 150 kt, or 1500kt in aggregate, testing for peaceful purposes.
Moon Treaty January 1, 1979 January 1, 1984 no Bans use and emplacement of nuclear weapons on the moon and other celestial bodies.
Strategic Arms Limitations Treaty (SALT II) June 18, 1979 no Limits strategic arms. Kept but not ratified by the US, abrogated in 1986.
Treaty of Rarotonga August 6, 1985 ? Bans nuclear weapons in South Pacific Ocean and islands. US never ratified.
Intermediate Range Nuclear Forces Treaty (INF) December 8, 1987 June 1, 1988 no Eliminated Intermediate Range Ballistic Missiles (IRBMs). Implemented by 1 June 1991. Both sides alleged the other was in violation of the treaty. Expired following U.S. withdrawal, 2 August 2019.
Treaty on Conventional Armed Forces in Europe November 19, 1990 July 17, 1992 yes Bans categories of weapons, including conventional, from Europe. Russia notified signatories of intent to suspend, 14 July 2007.
Strategic Arms Reduction Treaty I (START I) July 31, 1991 December 5, 1994 no 35-40% reduction in ICBMs with verification. Treaty expired 5 December 2009, renewed (see below).
Treaty on Open Skies March 24, 1992 January 1, 2002 yes Allows for unencumbered surveillance over all signatories.
US unilateral testing moratorium October 2, 1992 October 2, 1992 no George. H. W. Bush declares unilateral ban on nuclear testing.[36] Extended several times, not yet abrogated.
Strategic Arms Reduction Treaty (START II) January 3, 1993 January 1, 2002 no Deep reductions in ICBMs. Abrogated by Russia in 2002 in retaliation of US abrogation of ABM Treaty.
Southeast Asian Nuclear-Weapon-Free Zone Treaty (Treaty of Bangkok) December 15, 1995 March 28, 1997 yes Bans nuclear weapons from southeast Asia.
African Nuclear Weapon Free Zone Treaty (Pelindaba Treaty) January 1, 1996 July 16, 2009 yes Bans nuclear weapons in Africa.
Comprehensive Nuclear Test Ban Treaty (CTBT) September 10, 1996 yes (effectively) Bans all nuclear testing, peaceful and otherwise. Strong detection and verification mechanism (CTBTO). US has signed and adheres to the treaty, though has not ratified it.
Treaty on Strategic Offensive Reductions (SORT, Treaty of Moscow) May 24, 2002 June 1, 2003 no Reduces warheads to 1700–2200 in ten years. Expired, replaced by START II.
START I treaty renewal April 8, 2010 January 26, 2011 yes Same provisions as START I.

Compensation for victims[edit]

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, 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.[37]

  • United States: Prior to March 2009, the U.S. 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, and to others exposed to the radiation.[38] As of 2017, the U.S. 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.[39]
  • 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. However, victims say the eligibility requirements for compensation are too narrow.[citation needed]
  • United Kingdom: There is no formal British government compensation program. However, nearly 1,000 veterans of 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.[citation needed]
  • Russia: Decades later, Russia offered compensation to veterans who were part of the 1954 Totsk test. However, 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.[citation needed]
  • 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.[citation needed]

Milestone nuclear explosions[edit]

The following list is of milestone nuclear explosions. In addition to the atomic bombings of Hiroshima and Nagasaki, the first nuclear test of a given weapon type for a country is included, as well as tests that were otherwise notable (such as the largest test ever). All yields (explosive power) are given in their estimated energy equivalents in kilotons of TNT (see TNT equivalent). Putative tests (like Vela incident) have not been included.

Date Name
Yield (kt)
Country Significance
(1945-07-16)July 16, 1945 Trinity 18–20 United States First fission-device test, first plutonium implosion detonation.
(1945-08-06)August 6, 1945 Little Boy 12–18 United States Bombing of Hiroshima, Japan, first detonation of a uranium gun-type device, first use of a nuclear device in combat.
(1945-08-09)August 9, 1945 Fat Man 18–23 United States Bombing of Nagasaki, Japan, second detonation of a plutonium implosion device (the first being the Trinity Test), second and last use of a nuclear device in combat.
(1949-08-29)August 29, 1949 RDS-1 22 Soviet Union First fission-weapon test by the Soviet Union.
(1951-05-08)May 8, 1951 George 225 United States First boosted nuclear weapon test, first weapon test to employ fusion in any measure.
(1952-10-03)October 3, 1952 Hurricane 25 United Kingdom First fission weapon test by the United Kingdom.
(1952-11-01)November 1, 1952 Ivy Mike 10,400 United States First "staged" thermonuclear weapon, with cryogenic fusion fuel, primarily a test device and not weaponized.
(1952-11-16)November 16, 1952 Ivy King 500 United States Largest pure-fission weapon ever tested.
(1953-08-12)August 12, 1953 RDS-6s 400 Soviet Union First fusion-weapon test by the Soviet Union (not "staged").
(1954-03-01)March 1, 1954 Castle Bravo 15,000 United States First "staged" thermonuclear weapon using dry fusion fuel. A serious nuclear fallout accident occurred. Largest nuclear detonation conducted by United States.
(1955-11-22)November 22, 1955 RDS-37 1,600 Soviet Union First "staged" thermonuclear weapon test by the Soviet Union (deployable).
(1957-05-31)May 31, 1957 Orange Herald 720 United Kingdom Largest boosted fission weapon ever tested. Intended as a fallback "in megaton range" in case British thermonuclear development failed.
(1957-11-08)November 8, 1957 Grapple X 1,800 United Kingdom First (successful) "staged" thermonuclear weapon test by the United Kingdom
(1960-02-13)February 13, 1960 Gerboise Bleue 70 France First fission weapon test by France.
(1961-10-31)October 31, 1961 Tsar Bomba 50,000 Soviet Union Largest thermonuclear weapon ever tested—scaled down from its initial 100 Mt design by 50%.
(1964-10-16)October 16, 1964 596 22 China First fission-weapon test by the People's Republic of China.
(1967-06-17)June 17, 1967 Test No. 6 3,300 China First "staged" thermonuclear weapon test by the People's Republic of China.
(1968-08-24)August 24, 1968 Canopus 2,600 France First "staged" thermonuclear weapon test by France
(1974-05-18)May 18, 1974 Smiling Buddha 12 India First fission nuclear explosive test by India.
(1998-05-11)May 11, 1998 Pokhran-II 45–50 India First potential fusion-boosted weapon test by India; first deployable fission weapon test by India.
(1998-05-28)May 28, 1998 Chagai-I 40 Pakistan First fission weapon (boosted) test by Pakistan[40]
(2006-10-09)October 9, 2006 2006 nuclear test under 1 North Korea First fission-weapon test by North Korea (plutonium-based).
(2017-09-03)September 3, 2017 2017 nuclear test 200–300 North Korea First "staged" thermonuclear weapon test claimed by North Korea.

See also[edit]

Explanatory notes[edit]

  1. ^ Universal Time at the Nevada National Security Site is 8 hours after local time; UT dates are one day after local date for UT times after 16:00.
  2. ^ A video of the Armando test on YouTube
  3. ^ A video of the Pollux test on YouTube
  4. ^ A video of the Leda test on YouTube


  1. ^ "The Treaty has not been signed by France or by the People's Republic of China." U.S. Department of State, Limited Test Ban Treaty.
  2. ^ For a longer and more technical discussion, see U.S. Congress, Office of Technology Assessment (October 1989). The Containment of Underground Nuclear Explosions (PDF). Washington, D.C.: U.S. Government Printing Office. Archived from the original (PDF) on 2013-02-27. Retrieved 2018-12-24.
  3. ^ Yang, Xiaoping; North, Robert; Romney, Carl; Richards, Paul R. "Worldwide Nuclear Explosions" (PDF).
  4. ^ Scoles, Sarah (2023-04-20). "Trust but verify: U.S. labs are overhauling the nuclear stockpile. Can they validate the weapons without bomb tests?". Science.
  5. ^ Hoffman, David E. (2011-11-01). "Supercomputers offer tools for nuclear testing — and solving nuclear mysteries". Washington Post.
  6. ^ Associated Press (2006-10-18). "Supercomputers can't perfectly simulate nuclear blasts: Experts". CBC News.
  7. ^ Carey Sublette (9 August 2001), Nuclear Weapons Frequently Asked Questions, section 4.1.9, retrieved 10 April 2011
  8. ^ Jonathan Medalia (12 March 2008), Comprehensive Nuclear-Test-Ban Treaty: Issues and Arguments (PDF), Congressional Research Service, pp. 20–22, retrieved 9 December 2013
  9. ^ Medalia, Jonathan (2005-03-11). "Nuclear Weapons: Comprehensive Test Ban Treaty" (PDF). Congressional Record Service. Retrieved 2013-12-09.
  10. ^ "US conducts 'subcritical' nuclear test". 2012-12-07. Retrieved 2013-05-28.
  11. ^ Thomas Nilsen (2 October 2012). "Subcritical nuke tests may be resumed at Novaya Zemlya". Retrieved 2017-07-13.
  12. ^ Papazian, Ghazar R.; Reinovsky, Robert E.; Beatty, Jerry N. (2003). "The New World of the Nevada Test Site" (PDF). Los Alamos Science (28). Retrieved 2013-12-12.
  13. ^ Thorn, Robert N.; Westervelt, Donald R. (February 1, 1987). "Hydronuclear Experiments" (PDF). LANL Report LA-10902-MS. Retrieved December 9, 2013.
  14. ^ Conrad, David C. (July 1, 2000). "Underground explosions are music to their ears". Science and Technology Review. Retrieved 9 December 2013.
  15. ^ Nevada Test Site: U1a Complex subcritical experiments (PDF) (Report). DOE Nevada. February 2003. Archived from the original (PDF) on 17 May 2003.
  16. ^ Kishner, Andrew (18 September 2018). "U.S. Sneaks in 'Vega,' Its 28th Subcritical Nuclear Test". Retrieved 30 October 2019.
  17. ^ O'Brien, Nolan (24 May 2019). "Subcritical experiment captures scientific measurements to advance stockpile safety". LLNL. Retrieved 16 January 2021.
  18. ^ "US conducted subcritical nuclear test in November". NHK World-Japan. 16 January 2021. Retrieved 16 January 2021.
  19. ^ Danielson, Jeremy; Bauer, Amy L. (September 2016). Nightshade Prototype Experiments (Silverleaf). Los Alamos National Laboratory (Report). OSTI. doi:10.2172/1338708. OSTI 1338708.
  20. ^ Togzhan Kassenova (28 September 2009). "The lasting toll of Semipalatinsk's nuclear testing". Bulletin of the Atomic Scientists.
  21. ^ a b Pavlovski, O. A. (1 January 1998). "Radiological Consequences of Nuclear Testing for the Population of the Former USSR (Input Information, Models, Dose, and Risk Estimates)". Atmospheric Nuclear Tests. Springer, Berlin, Heidelberg. pp. 219–260. doi:10.1007/978-3-662-03610-5_17. ISBN 978-3-642-08359-4.
  22. ^ "Radioactive Fallout - Worldwide Effects of Nuclear War - Historical Documents".
  23. ^ The Containment of Underground Explosions (Report). Office of Technology Assessment. 31 October 1989. p. 11. OTA-ISC-414.
  24. ^ "United States Nuclear Tests: July 1945 through September 1992" (PDF). Las Vegas, NV: Department of Energy, Nevada Operations Office. 2000-12-01. Archived from the original (PDF) on 2006-10-12. Retrieved 2013-12-18. This is usually cited as the "official" US list.
  25. ^ Long, Kat. "Blasts from the Past: Old Nuke Test Films Offer New Insights [Video]". Scientific American. Retrieved 2017-04-24.
  26. ^ "USSR Nuclear Weapons Tests and Peaceful Nuclear Explosions 1949 through 1990" (Document). Sarov, Russia: RFNC-VNIIEF. 1996. The official Russian list of Soviet tests.
  27. ^ Mikhailov, Editor in Chief, V.N.; Andryushin, L.A.; Voloshin, N.P.; Ilkaev, R.I.; Matushchenko, A.M.; Ryabev, L.D.; Strukov, V.G.; Chernyshev, A.K.; Yudin, Yu.A. "Catalog of Worldwide Nuclear Testing". Archived from the original on 2013-12-19. Retrieved 2013-12-28. {{cite web}}: |last1= has generic name (help)An equivalent list available on the internet.
  28. ^ "British nuclear weapons testing in Australia | ARPANSA". Retrieved 2022-11-02.
  29. ^ "UK/US Agreement". Archived from the original on 2007-06-07. Retrieved 2010-10-21.
  30. ^ "N° 3571.- Rapport de MM. Christian Bataille et Henri Revol sur les incidences environnementales et sanitaires des essais nucléaires effectués par la France entre 1960 et 1996 (Office d'évaluation des choix scientifiques et technologiques)". Retrieved 2010-10-21.
  31. ^ "Nuclear Weapons Test List". Retrieved 22 September 2018.
  32. ^ "Pakistan Special Weapons - A Chronology". Archived from the original on 2012-04-27. Retrieved 2018-12-24.
  33. ^ U.S. Department of State, Limited Test Ban Treaty.
  34. ^ "CTBTO Factsheet: Ending Nuclear Explosions" (PDF). Retrieved 2012-05-23.
  35. ^ "Status of signature and ratification". Retrieved 2012-05-23.
  36. ^ "The Status of the Comprehensive Test Ban Treaty: Signatories and Ratifiers". Arms Control Association. March 2014. Retrieved June 29, 2014.
  37. ^ Council, National Research (11 February 2003). Exposure of the American Population to Radioactive Fallout from Nuclear Weapons Tests: A Review of the CDC-NCI Draft Report on a Feasibility Study of the Health Consequences to the American Population from Nuclear Weapons Tests Conducted by the United States and Other Nations. doi:10.17226/10621. ISBN 9780309087131. PMID 25057651.
  38. ^ "Radiation Exposure Compensation System: Claims to Date Summary of Claims Received by 06/11/2009" (PDF).
  39. ^ "Troops Who Cleaned Up Radioactive Islands Can't Get Medical Care". The New York Times. 28 January 2017.
  40. ^ "Pakistan Nuclear Weapons: A Brief History of Pakistan's Nuclear Program". Federation of American Scientists. 11 December 2002. Retrieved 30 October 2019.

General and cited references[edit]

  • 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).
  • 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[edit]