Nuclear testing

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Preparation for an underground nuclear test at the Nevada Test Site in the 1980s. Visible in the photograph are the test monitoring equipment, as well as the subsidence craters created by previous underground nuclear tests.
Preparation for an underground nuclear test at the Nevada Test Site in the 1980s. Visible in the photograph are the test monitoring equipment, as well as the subsidence craters created by previous underground nuclear tests.
Nuclear weapons
One of the first nuclear bombs.
 Nuclear-armed countries 
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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 have developed nuclear weapons have 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 structures behave when subjected to nuclear explosions. Additionally, 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 atomic test was detonated by the United States at the Trinity site on July 16, 1945, with a yield approximately equivalent to 20 kilotons. The first hydrogen bomb, codenamed "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 an estimated yield of around 50 megatons.

In 1963, all nuclear 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, while China continued up until 1980. The last underground test by the United States was in 1992, the Soviet Union in 1990, the United Kingdom in 1991, and both France and China continued testing until 1996. After adopting the Comprehensive Test Ban Treaty in 1996, all of these states have pledged to discontinue all nuclear testing. Non-signatories India and Pakistan last tested nuclear weapons in 1998.

The most recent nuclear test was announced by North Korea on October 9, 2006. See 2006 North Korean nuclear test for more information.

Contents

[edit] Types of nuclear weapons tests

Nuclear weapons tests have historically been broken into categories (by treaties) reflecting the medium or location of the test: atmospheric, underwater, and underground.

Four major types of nuclear testing: 1. atmospheric, 2. underground, 3. exoatmospheric, and 4. underwater.
Four major types of nuclear testing: 1. atmospheric, 2. underground, 3. exoatmospheric, and 4. underwater.
  • Atmospheric testing designates explosions which take place in or above the atmosphere. Generally these have occurred as devices detonated on towers, balloons, barges, islands, or dropped from airplanes. A limited number of high altitude nuclear explosions have also been conducted, generally fired from rockets. Nuclear explosions which are 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. High altitude nuclear explosions can generate an electromagnetic pulse, and charged particles resulting from the blast can cross hemispheres to create an auroral display.
  • Underwater testing results from 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 water and steam, contaminating nearby ships or structures.
  • Underground testing refers to nuclear tests which are 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. When the explosion is fully contained, underground nuclear testing emits a negligible amount of fallout. However, underground nuclear tests can "vent" to the surface, producing considerable amounts of radioactive debris as a consequence. Underground testing can result in seismic activity depending on the yield of the nuclear device and the composition of the medium it is detonated in, and generally result in the creation of subsidence craters.[1] 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.

Separately from these designations, nuclear tests are also often categorized by the purpose of the test itself. Tests which are designed to garner information about how (and if) the weapons themselves work are weapons related tests, while tests designed to gain information about the effects of the weapons themselves on structures or organisms are known as weapons effects tests. Additional types of nuclear tests are possible as well (such as nuclear tests which are also part of anti-ballistic missile testing).

Nuclear-weapons-related testing which purposely results in no yield is known as subcritical testing, referring to the lack of a creation of a critical mass of fissile material. Additionally, there have been simulations of nuclear tests using conventional explosives (such as the Minor Scale U.S. test in 1985).

[edit] History

The first nuclear test, "Trinity", took place on July 16, 1945.
The first nuclear test, "Trinity", took place on July 16, 1945.

The first nuclear test was conducted in 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 nuclear tests before the Soviet Union developed their first atomic bomb (Joe 1) and tested it on August 29, 1949. Neither country had very many nuclear 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 were also using a site in the Marshall Islands (Pacific Proving Grounds) for extensive nuclear testing.

The early tests were used primarily to discern the military effects of nuclear weapons (Crossroads had involved the effect of nuclear 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 twentieth century.

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

Nuclear tests can involve many hazards. A number 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 be spread in a direction which had not been 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 well as a Japanese fishing boat (Daigo Fukuryū Maru). One member of the boat's crew 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 1951-1962.
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 1951-1962.

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 atmospheric tests stopped, however, but because the United States and the Soviet Union in particular stopped testing above ground it cut the number of atmospheric tests down substantially, because about 86% of all nuclear tests were conducted by those two countries. France continued atmospheric testing until 1974, and People's Republic of China until 1980.

Almost all new nuclear powers have announced their possession of nuclear weapons with a nuclear test. The only acknowledged nuclear power which claims never to have conducted a test was South Africa (see Vela Incident), which has since dismantled all of its weapons. Israel is widely thought to possess a sizeable nuclear arsenal, though it has never tested. 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 the value of these simulations without actual test result data is thought to be slim.

The Sedan test of 1962 was an experiment by the United States in using nuclear weapons to excavate large amounts of earth.
The Sedan test of 1962 was an experiment by the United States in using nuclear weapons to excavate large amounts of earth.

Some nuclear testing has been for ostensibly peaceful purposes. These so-called peaceful nuclear explosions were used to evaluate whether nuclear explosions could be used for non-military purposes such as digging canals and artificial harbors, or to stimulate oil and gas fields. In most cases the results were too radioactive for use, and the programs proved neither economically sound or politically favorable.

Nuclear testing has also been used for clearly political purposes. The most explicit example of this was the detonation of the largest nuclear bomb ever created, the 50 megaton Tsar Bomba (with a maximum yield of 100 Mt), by the Soviet Union in 1961. This weapon was too large to be practically used against an enemy target, and it is not thought that any were manufactured except the one detonated in the test.

There have been many attempts to limit the number and size of nuclear tests; the most far-reaching was the Comprehensive Test Ban Treaty of 1996, which was not ratified by 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 also opposed to future testing as an acceleration of the arms race.

[edit] Nuclear testing by country

Main article: List of nuclear tests

The nuclear powers have conducted at least 2,000 nuclear test explosions (numbers are approximated, as some test results have been disputed):

Over 2,000 nuclear tests have been conducted, in over a dozen different sites around the world.
Over 2,000 nuclear tests have been conducted, in over a dozen different sites around the world.

Additionally, there may have been at least three alleged but unacknowledged nuclear explosions (see list of alleged nuclear tests). Of these, the only one taken seriously as a possible nuclear test is the Vela Incident, a possible detection of a nuclear explosion in the Indian Ocean in 1979, hypothesized to have been a joint Israeli/South African test.

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, when North Korea reported a successful underground nuclear test, was the longest period since 1945 with no acknowledged nuclear tests.

Graph of nuclear testing (North Korea not yet shown).

[edit] 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, 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 megaton).

Date Name Yield (kT) Country Significance
16 Jul 1945 Trinity 19 Flag of the United States USA First fission device test, first plutonium implosion detonation
6 Aug 1945 Little Boy 15 Flag of the United States USA Bombing of Hiroshima, Japan, first detonation of an enriched uranium gun-type device
9 Aug 1945 Fat Man 21 Flag of the United States USA Bombing of Nagasaki, Japan
29 Aug 1949 RDS-1 22 Flag of the Soviet Union USSR First fission weapon test by the USSR
3 Oct 1952 Hurricane 25 Flag of the United Kingdom UK First fission weapon test by the UK
1 Nov 1952 Ivy Mike 10,400 Flag of the United States USA First "staged" thermonuclear weapon test (not deployable)
12 Aug 1953 Joe 4 400 Flag of the Soviet Union USSR First fusion weapon test by the USSR (not "staged", but deployable)
1 Mar 1954 Castle Bravo 15,000 Flag of the United States USA First deployable "staged" thermonuclear weapon; fallout accident where some people were radiation-poisoned
22 Nov 1955 RDS-37 1,600 Flag of the Soviet Union USSR First "staged" thermonuclear weapon test by the USSR (deployable)
8 Nov 1957 Grapple X 1,800 Flag of the United Kingdom UK First (successful) "staged" thermonuclear weapon test by the UK
13 Feb 1960 Gerboise Bleue 70 Flag of France France First fission weapon test by France
31 Oct 1961 Tsar Bomba 50,000 Flag of the Soviet Union USSR Largest thermonuclear weapon ever tested
16 Oct 1964 596 22 Flag of the People's Republic of China PR China First fission weapon test by the People's Republic of China
17 Jun 1967 Test No. 6 3,300 Flag of the People's Republic of China PR China First "staged" thermonuclear weapon test by the People's Republic of China
24 Aug 1968 Canopus 2,600 Flag of France France First "staged" thermonuclear test by France
18 May 1974 Smiling Buddha 12 Flag of India India First fission nuclear explosive test by India
11 May 1998 Shakti I 43 Flag of India India First potential fusion/boosted weapon test by India
(exact yields disputed, between 25kt and 45kt)
11 May 1998 Shakti II 12 Flag of India India First deployable fission weapon test by India
28 May 1998 Chagai-I 9-12 Flag of Pakistan Pakistan First fission weapon test by Pakistan.
9 Oct 2006 Hwadae-ri <1 Flag of North Korea North Korea First fission device tested by North Korea; resulted as a fizzle

"Deployable" refers to whether the device tested could be hypothetically used in actual combat (in contrast with a proof-of-concept device). "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.

[edit] See also

Weapons of mass destruction
WMD world map
By type

Biological warfare
Chemical warfare
Nuclear weapons
Radiological weapons

Treaties
By country
Albania Algeria
Argentina Australia
Brazil Bulgaria
Canada PR China
France Germany
India Iran
Iraq Israel
Japan Netherlands
North Korea Pakistan
Poland Russia
South Africa Syria
Taiwan (ROC) United Kingdom
United States
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[edit] Footnotes

  1. ^ For an overview of the preparations and considerations used in underground nuclear testing, see "Underground Nuclear Weapons Testing" (Globalsecurity.org). For a longer and more technical discussion, see U.S. Congress, Office of Technology Assessment (October 1989). The Containment of Underground Nuclear Explosions. Washington, D.C.: U.S. Government Printing Office. 

[edit] References

History
  • 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.
  • 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.

[edit] External links

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