Nuclear weapons testing

Nuclear weapons tests are experiments carried out to determine the performance of nuclear weapons and the effects of their explosion. Over 2,000 nuclear weapons tests have been carried out since 1945. Nuclear testing is a sensitive political issue. Governments have often performed tests to signal strength. Because of their destruction and fallout, 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 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, 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.
With the advent of nuclear technology and its increasingly global fallout an anti-nuclear movement formed and in 1963, three 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.
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, 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. Generally, these have occurred as devices detonated on towers, balloons, barges, or islands, or dropped from airplanes, and some 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. 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 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 is conducted below the surface of the earth at varying depths. Underground nuclear testing comprised 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. 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. 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 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. Tests of this nature have usually been conducted to evaluate the effects of nuclear weapons against naval vessels, or to evaluate potential sea-based nuclear weapons. 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, 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 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 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

Since the 1996 Comprehensive Nuclear-Test-Ban Treaty, "nuclear explosions" of all kinds are banned. Nuclear nations have invested in many alternatives to maintain confidence in weapon capability:

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. A theme has generally been that even though simulations cannot fully replace physical testing, they can reduce the amount that is necessary.
Physical testing
* Materials testing
** Subcritical tests involving fissile materials and high explosives that purposely result in no yield. The name refers to the lack of creation of a critical mass 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, to determine a bomb core's relevant equation of state.
* Fission testing
** Critical mass 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 accidents.
** 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. Any fission yield is considered banned by the CTBT.
* Fusion testing: inertial confinement fusion experiments using lasers, like the National Ignition Facility, or magnetized liners, like the Z Pulsed Power Facility, or projectile compression. These study the plasma physics and ignition of deuterium-tritium mixtures.

Subcritical tests executed by the United States include:

History

Significance

Country

Name

Date

Yield

First plutonium test

United States|1912

Yield

The yield of atomic and thermonuclear weapons is typically measured in kilotons or megatons TNT equivalent. Thermonuclear bombs, often mesaured in megatons, can be hundreds of times stronger than their atomic counterparts measured only in kilotons.
In the 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 was also the issue of which ton to use, as short tons, long tons, and metric tonnes all had different values. It was decided that one kiloton would be equivalent to exactly,.

Nuclear testing by country

The nuclear powers have conducted more than 2,000 nuclear test explosions :

United States: 1,054 tests by official count. 219 were atmospheric tests as defined by the CTBT. These tests include 904 at the Nevada Test Site, 106 at the Pacific Proving Grounds and other locations in the Pacific, 3 in the South Atlantic Ocean, and 17 other tests taking place in Amchitka Alaska, Colorado, Mississippi, New Mexico and Nevada outside the NNSS. 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 by official count, plus 13 unnumbered test failures. Most were at their Southern Test Area at Semipalatinsk Test Site and the Northern Test Area at Novaya Zemlya. Others include rocket tests and peaceful-use explosions at various sites in Russia, Kazakhstan, Turkmenistan, Uzbekistan and Ukraine. Soviet Union's table data.
United Kingdom: 45 tests, of which 12 were in Australian territory, including three at the Montebello Islands and nine in mainland South Australia at Maralinga and Emu Field, 9 at Christmas Island (Kiritimati) in the Pacific Ocean, plus 24 in the United States at the Nevada Test Site as part of joint test series). 43 safety tests 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, four atomic atmospheric tests at C.S.E.M. near Reggane, 13 atomic underground tests at C.E.M.O. near In Ekker in the French Algerian 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, and given alternate names. France's summary table.
China: 45 tests, at Lop Nur Nuclear Weapons Test Base, in Malan, Xinjiang There are two additional unnumbered failed tests. China's summary table.
India: Six underground explosions, at Pokhran. India's summary table.
Pakistan: Six underground explosions at Ras Koh Hills and the Chagai District. 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 escalating tensions between them and the United States. Their most recent nuclear test was on September 3, 2017. North Korea's summary table

There may also have been at least three alleged but unacknowledged nuclear explosions 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.

Global fallout

Nuclear weapons testing did not produce an outcome 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 produce a global fallout that peaked in 1963, reaching levels of about 0.15 mSv per year worldwide, or about 7% of average background radiation dose from all sources. It 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 on nuclear weapons testing, particularly atmospheric testing. It has been estimated that by 2020 between 200,000 to 460,000 people had died as a result of nuclear weapons testing, while the total number of deaths may rise up to 2.4 million people.

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 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. 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 a nuclear explosion anywhere except underground, in order to reduce atmospheric fallout. Most countries have signed and ratified the Partial Nuclear Test Ban, which came 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 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 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:

Name	Agreement date	In force date	In effect today?	Notes
Unilateral USSR ban			no	USSR unilaterally stops testing provided the West does as well.
Bilateral testing ban			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			yes	Bans testing of all kinds in Antarctica.
Partial Nuclear Test Ban Treaty			yes	Ban on all but underground testing.
Outer Space Treaty			yes	Bans testing on the moon and other celestial bodies.
Treaty of Tlatelolco			yes	Bans testing in South America and the Caribbean Sea Islands.
Nuclear Non-proliferation Treaty			yes	Bans the proliferation of nuclear technology to non-nuclear nations.
Seabed Arms Control Treaty			yes	Bans emplacement of nuclear weapons on the ocean floor outside territorial waters.
Strategic Arms Limitation Treaty			no	A five-year ban on installing launchers.
Anti-Ballistic Missile Treaty			no	Restricts ABM development; additional protocol added in 1974; abrogated by the US in 2002.
Agreement on the Prevention of Nuclear War			yes	Promises to make all efforts to promote security and peace.
Threshold Test Ban Treaty			yes	Prohibits higher than 150 kt for underground testing.
Peaceful Nuclear Explosions Treaty			yes	Prohibits higher than 150 kt, or 1500kt in aggregate, testing for peaceful purposes.
Moon Treaty			no	Bans use and emplacement of nuclear weapons on the moon and other celestial bodies.
Strategic Arms Limitations Treaty			no	Limits strategic arms. Kept but not ratified by the US, abrogated in 1986.
Treaty of Rarotonga			?	Bans nuclear weapons in South Pacific Ocean and islands. US never ratified.
Intermediate Range Nuclear Forces Treaty			no	Eliminated Intermediate Range Ballistic Missiles. Implemented by 1 June 1991. Both sides alleged the other was in violation of the treaty. Expired following US withdrawal, 2 August 2019.
Treaty on Conventional Armed Forces in Europe			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)			no	35-40% reduction in ICBMs with verification. Treaty expired 5 December 2009, renewed.
Treaty on Open Skies			yes	Allows for unencumbered surveillance over all signatories.
US unilateral testing moratorium			no	George. H. W. Bush declares unilateral ban on nuclear testing. Extended several times, not yet abrogated.
Strategic Arms Reduction Treaty (START II)			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			yes	Bans nuclear weapons from southeast Asia.
African [Nuclear Weapon Free Zone Treaty]			yes	Bans nuclear weapons in Africa.
Comprehensive Nuclear Test Ban Treaty			yes	Bans all nuclear testing, peaceful and otherwise. Strong detection and verification mechanism. US has signed and adheres to the treaty, though has not ratified it.
Treaty on Strategic Offensive Reductions			no	Reduces warheads to 1700–2200 in ten years. Expired, replaced by START II.
START I treaty renewal			yes	Same provisions as START I.

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 possible health hazards associated with exposure to nuclear fallout, various studies were done to assess the extent of the hazard. A Centers for Disease Control and Prevention/ National Cancer Institute study claimed 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, and to others exposed to the radiation from these tests. As of 2017, the US government has 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 was 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 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 1954 Totsk test. There was no compensation to civilians made sick 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], the first nuclear test of a given weapon type for a country is included, as well as tests that were otherwise notable. All yields are given in their estimated energy equivalents in kilotons of TNT. Putative tests have not been included.

Date	Name		Country	Significance
	Trinity		United States	First fission-device test, first plutonium implosion detonation.
	Little Boy		United States	Bombing of Hiroshima, Japan, first detonation of a uranium gun-type device, first use of a nuclear device in combat.
	Fat Man		United States	Bombing of Nagasaki, Japan, second detonation of a plutonium implosion device, second and last use of a nuclear device in combat.
	RDS-1	22	Soviet Union	First fission-weapon test by the Soviet Union.
	George	225	United States	First boosted nuclear weapon test, first weapon test to employ fusion in any measure.
	Hurricane	25		First fission weapon test by the United Kingdom.
	Ivy Mike	10,400	United States	First "staged" thermonuclear weapon, with cryogenic fusion fuel, primarily a test device and not weaponized.
	Ivy King	500	United States	Largest pure-fission weapon ever tested.
	RDS-6s	400	Soviet Union	First fusion-weapon test by the Soviet Union.
	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.
	RDS-37	1,600	Soviet Union	First "staged" thermonuclear weapon test by the Soviet Union.
	Orange Herald	720	United Kingdom	Largest boosted fission weapon ever tested. Intended as a fallback "in megaton range" in case British thermonuclear development failed.
	Grapple X	1,800	United Kingdom	First "staged" thermonuclear weapon test by the United Kingdom
		70	France	First fission weapon test by France.
	Tsar Bomba	50,000	Soviet Union	Largest thermonuclear weapon ever tested—scaled down from its initial 100 Mt design by 50%.
	596	22	China	First fission-weapon test by the People's Republic of China.
	Test No. 6	3,300	China	First "staged" thermonuclear weapon test by the People's Republic of China.
	Canopus	2,600	France	First "staged" thermonuclear weapon test by France
		12	India	First fission nuclear explosive test by India.
	Pokhran-II	45–50	India	First potential fusion-boosted weapon test by India; first deployable fission weapon test by India.
	Chagai-I	40	Pakistan	First fission weapon test by Pakistan
				First fission-weapon test by North Korea.
				First "staged" thermonuclear weapon test claimed by North Korea.

;Note

"Staged" refers to whether it was a "true" thermonuclear weapon 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 and the tests by India and Pakistan in 1998, are somewhat contested among specialists.

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.. 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.