Nuclear weapons tests are experiments carried out to determine the effectiveness, yield, and explosive capability of nuclear weapons. Throughout the twentieth century, most nations that developed nuclear weapons tested them. Testing nuclear weapons can yield information about how the weapons work, as well as how the weapons behave under various conditions and how personnel, structures, and equipment behave when subjected to nuclear explosions. Nuclear testing has often been used as an indicator of scientific and military strength, and many tests have been overtly political in their intention; most nuclear weapons states publicly declared their nuclear status by means of a nuclear test.
The first nuclear device was detonated as a test by the United States at the Trinity site on July 16, 1945, with a yield approximately equivalent to 20 kilotons of TNT. The first thermonuclear weapon technology test of engineer 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 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 in the United States continued until 1992 (its last nuclear test), the Soviet Union until 1990, the United Kingdom until 1991, and both China and France until 1996. In signing the Comprehensive Nuclear-Test-Ban Treaty in 1996, these states have pledged to discontinue all nuclear testing; the treaty has not yet entered into force because of 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.
Nuclear weapons tests have historically been divided into four categories reflecting the medium or location of the test.
Another way to classify nuclear tests are 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 second."
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 like2do.com resource (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.
Aside from these technical considerations, tests have been conducted for political and training purposes, and can often serve multiple purposes.
Hydronuclear tests study nuclear materials under the conditions of explosive shock compression. They can create sub-critical conditions, or supercritical conditions with yields ranging from negligible all the way up to a substantial fraction of full weapon yield.
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 sub-critical or super-critical, in which case significant radiation fluxes can be produced. This type of test resulted in several criticality accidents.
Sub-critical (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. Sub-critical tests continue to be performed by the United States, Russia, and the People's Republic of China, at least.
|Name||Date Time (UT[a])||Location||Elevation + Height||Notes|
|A series of 50 tests||January 1, 1960||Los Alamos National Lab Test Area 49||2,183 metres (7,162 ft) - 20 metres (66 ft)||Series of 50 tests during US/USSR joint nuclear test ban.|
|Odyssey||NTS Area U1a||1,222 metres (4,009 ft) - 190 metres (620 ft)|
|Trumpet||NTS Area U1a-102D||1,222 metres (4,009 ft) - 190 metres (620 ft)|
|Kismet||March 1, 1995||NTS Area U1a||1,222 metres (4,009 ft) - 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||1,222 metres (4,009 ft) - 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||1,222 metres (4,009 ft) - 290 metres (950 ft)||Holog and Clarinet may have switched locations.|
|Stagecoach||March 25, 1998||NTS Area U1a||1,222 metres (4,009 ft) - 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||1,222 metres (4,009 ft) - 290 metres (950 ft)|
|Cimarron||December 11, 1998||NTS Area U1a||1,222 metres (4,009 ft) - 290 metres (950 ft)||Plutonium surface ejecta studies.|
|Clarinet||February 9, 1999||NTS Area U1a.101C||1,222 metres (4,009 ft) - 290 metres (950 ft)||Holog and Clarinet may have switched places on the map.|
|Oboe||September 30, 1999||NTS Area U1a.102C||1,222 metres (4,009 ft) - 290 metres (950 ft)|
|Oboe 2||November 9, 1999||NTS Area U1a.102C||1,222 metres (4,009 ft) - 290 metres (950 ft)|
|Oboe 3||February 3, 2000||NTS Area U1a.102C||1,222 metres (4,009 ft) - 290 metres (950 ft)|
|Thoroughbred||March 22, 2000||NTS Area U1a||1,222 metres (4,009 ft) - 290 metres (950 ft)||Plutonium surface ejecta studies, followup to Cimarron.|
|Oboe 4||April 6, 2000||NTS Area U1a.102C||1,222 metres (4,009 ft) - 290 metres (950 ft)|
|Oboe 5||August 18, 2000||NTS Area U1a.102C||1,222 metres (4,009 ft) - 290 metres (950 ft)|
|Oboe 6||December 14, 2000||NTS Area U1a.102C||1,222 metres (4,009 ft) - 290 metres (950 ft)|
|Oboe 8||September 26, 2001||NTS Area U1a.102C||1,222 metres (4,009 ft) - 290 metres (950 ft)|
|Oboe 7||December 13, 2001||NTS Area U1a.102C||1,222 metres (4,009 ft) - 290 metres (950 ft)|
|Oboe 9||June 7, 2002 21:46:--||NTS Area U1a.102C||1,222 metres (4,009 ft) - 290 metres (950 ft)|
|Mario||August 29, 2002 19:00:--||NTS Area U1a||1,222 metres (4,009 ft) - 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||1,222 metres (4,009 ft) - 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||1,222 metres (4,009 ft) - 290 metres (950 ft)|
|Armando||May 25, 2004||NTS Area U1a||1,222 metres (4,009 ft) - 290 metres (950 ft)||Plutonium spall measurements using x-ray analysis.[b]|
|Step Wedge||April 1, 2005||NTS Area U1a||1,222 metres (4,009 ft) - 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||1,222 metres (4,009 ft) - 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||1,222 metres (4,009 ft) - 190 metres (620 ft)||Feb-6 thru May 3, 2007, 12 mini-hydronuclear experiments in thermos-sized flasks.|
|Bacchus||September 16, 2010||NTS Area U1a.05?||1,222 metres (4,009 ft) - 190 metres (620 ft)|
|Barolo A||December 1, 2010||NTS Area U1a.05?||1,222 metres (4,009 ft) - 190 metres (620 ft)|
|Barolo B||February 2, 2011||NTS Area U1a.05?||1,222 metres (4,009 ft) - 190 metres (620 ft)|
|Castor||September 1, 2012||NTS Area U1a||1,222 metres (4,009 ft) - 190 metres (620 ft)||Not even a subcrit, contained no plutonium; a dress rehearsal for Pollux.|
|Pollux||December 5, 2012||NTS Area U1a||1,222 metres (4,009 ft) - 190 metres (620 ft)||A subcritical test with a scaled down warhead mockup.[c]|
|Leda||June 15, 2014||NTS Area U1a||1,222 metres (4,009 ft) - 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||1,222 metres (4,009 ft) - 190 metres (620 ft)||Expected to be a plutonium subcritical test with a scaled down warhead mockup.|
There have also been simulations of the effects of nuclear detonations using conventional explosives (such as the Minor Scale U.S. test in 1985). The explosives might be spiked with radioactive materials to simulate fallout dispersal.
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.
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 a hundred miles, 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 Fukury? 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.
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 1945-92, 520 atmospheric nuclear explosions (including 8 underwater) have been conducted with a total yield of 545 megatons, with a peak occurring in 1961-62, when 340 megatons were detonated in the atmosphere by the United States and Soviet Union. while the estimated number of underground nuclear tests conducted in the period from 1957 to 1992 is 1,352 explosions with a total yield of 90 Mt.
The first atomic test, "Trinity", took place on July 16, 1945.
The Sedan test of 1962 was an experiment by the United States in using nuclear weapons to excavate large amounts of earth.
The nuclear powers have conducted more than 2,000 nuclear test explosions (numbers are approximate, as some test results have been disputed):
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.
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.
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. 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.
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||August 2, 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, 1962||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 USA 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||yes||Eliminates Intermediate Range Ballistic Missiles (IRBMs). Implemented by 1 June 1991. Both sides allege the other is in violation of the treaty.|
|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. 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.|
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.
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, and tests which 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.
|Trinity||18-20||USA||First fission device test, first plutonium implosion detonation|
|Little Boy||12-18||USA||Bombing of Hiroshima, Japan, first detonation of a uranium gun-type device, first use of a nuclear device in combat.|
|Fat Man||18-23||USA||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.|
|RDS-1||22||USSR||First fission weapon test by the USSR|
|Hurricane||25||UK||First fission weapon test by the UK|
|Ivy Mike||10,400||USA||First cryogenic fusion fuel "staged" thermonuclear weapon, primarily a test device and not weaponized|
|Ivy King||500||USA||Largest pure-fission weapon ever tested|
|Joe 4||400||USSR||First fusion weapon test by the USSR (not "staged")|
|Castle Bravo||15,000||USA||First dry fusion fuel "staged" thermonuclear weapon; a serious nuclear fallout accident occurred; largest nuclear detonation conducted by United States|
|RDS-37||1,600||USSR||First "staged" thermonuclear weapon test by the USSR (deployable)|
|Orange Herald||720||UK||Largest boosted fission weapon ever tested. Intended as a fallback "in megaton range" in case British thermonuclear development failed.|
|Grapple X||1,800||UK||First (successful) "staged" thermonuclear weapon test by the UK|
|70||France||First fission weapon test by France|
|Tsar Bomba||50,000||USSR||Largest thermonuclear weapon ever tested--scaled down from its initial 100 Mt design by 50%|
|596||22||PR China||First fission weapon test by the People's Republic of China|
|Test No. 6||3,300||PR 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 (boosted) test by Pakistan|
|2006 North Korean nuclear test||under 1||First fission weapon test by North Korea (plutonium-based)|
|2017 North Korean nuclear test||200-300||First "staged" thermonuclear weapon test claimed by North Korea|
"Staging" refers to whether it was a "true" hydrogen bomb 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.