Encyclopedia
Nuclear testing is experimentation with
nuclear weapons. Throughout the twentieth century, most nations which have developed nuclear weapons have staged tests of 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, and 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, 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 tests. 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 up 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 both last tested nuclear weapons in 1998.
Types of nuclear testing
Nuclear weapons tests have been historically broken into categories reflecting in what sort of medium or location the test has been conducted: atmospheric, underwater, and underground.
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 tests 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 . Tests of this nature have usually been conducted to evaluate the effects of nuclear weapons against a Navy , or to evaluate potential sea-based nuclear weapons . 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, on account of other forms of nuclear testing being banned by the
Limited Test Ban Treaty in 1963. When the explosion is fully contained, underground nuclear testing emits a negligible amount of fallout. Some underground nuclear tests have been able to "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 generally result in the creation of
subsidence craters. In 1976, the United States and the USSR agreed to limit the maximum yield of underground tests to 150 kt.
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 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 .
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 non-nuclear simulations of nuclear tests using conventional explosives .
History
The first nuclear test was conducted by the
United States 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 the scientists and military officers 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 only six nuclear tests before the
Soviet Union developed their first atomic bomb and tested it on August 29, 1949. Neither country had very many nuclear weapons to spare at first, and so testing was relatively limited . However, by the 1950s the United States had established a dedicated test site on its own territory and were also using a site in the
Marshall Islands for extensive nuclear testing.
The early tests were used primarily to discern the military effects of nuclear weapons 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.
Nuclear tests can involve many hazards. A number of these were best 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 ahead of time. The fallout plume spread high levels of radiation for over a hundred miles, contaminating a number of populated islands in nearby atoll formations , as well as a Japanese fishing boat . 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.
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 lead to the
Partial Test Ban Treaty in 1963, which limited signatories to only underground testing. Not all atmospheric tests stopped, however, but because the United States and the Soviet Union in particular stopped testing aboveground it cut the number of atmospheric tests down substantially, since around 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 to have never conducted a test was
South Africa , which has since claimed to have dismantled all of its weapons. The state of
Israel is widely thought by intelligence agencies 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.
Some nuclear testing has been for "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 , 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 actually manufactured except the one which was detonated in the test. The weapon was used by the USSR as a show of Soviet strength and force, rather than to be developed as an actual weapon or for specifically scientific purposes.
There have been many attempts to limit the number and size of nuclear testing; the most far-reaching was the
Comprehensive Test Ban Treaty of 1996, which was not ratified by the United States. The last worldwide nuclear tests were in 1998. 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.
Nuclear testing by country
The nuclear powers have conducted at least 2,000 nuclear test explosions :
United States: 1,054 tests by official count , most at
Nevada Test Site and the
Pacific Proving Grounds in the
Marshall Islands, with ten other tests taking place at various locations in the United States, including
Alaska,
Colorado,
Mississippi, and
New Mexico .
Soviet Union: 715 tests by official count , most at
Semipalatinsk Test Site and
Novaya Zemlya, and a few more at various sites in
Russia,
Kazakhstan,
Turkmenistan, and
Ukraine.
France: 210 tests, mostly at Reggane and Ekker in
Algeria, and
Fangataufa and
Moruroa in
French Polynesia.
United Kingdom: 45 tests
China: 45 tests
India: between 5 and 6 tests, at Pokhran.
Pakistan: between 3 and 6 tests, at Chagai Hills.
Additionally, there may have been at least three alleged/disputed/unacknowledged nuclear explosions . 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 be a joint
Israeli/
South African test.
From the first nuclear test in 1945 until the latest tests by
Pakistan in 1998, there was never a period of more than 22 months with no nuclear testing. Therefore, the period from June of 1998 to the present has been, by far, the longest period since 1945 with no acknowledged nuclear tests.
See also
References
;History
External links
- lists 2,199 explosions by date, country, location, yield etc.
- at Nuclear Files.org
