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A nuclear explosion is an explosion that occurs as a result of the rapid release of energy from a high-speed nuclear reaction. The driving reaction may be nuclear fission, nuclear fusion or a multistage cascading combination of the two, though to date all fusion based weapons have used a fission device to initiate fusion, and a pure fusion weapon remains a hypothetical device.
Atmospheric nuclear explosions are associated with mushroom clouds, although mushroom clouds can occur with large chemical explosions, and it is possible to have an air-burst nuclear explosion without these clouds. Nuclear explosions produce radiation and radioactive debris.
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In 1963, the United States, Soviet Union, and United Kingdom 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. Many other non-nuclear nations acceded to the Treaty following its entry into force; however, three nuclear weapons states have not acceded: France, China, and North Korea.
The primary application to date has been military (i.e. nuclear weapons). However, there are other potential applications, which have not yet been explored, or have been considered but abandoned. They include
- Nuclear pulse propulsion, including using a nuclear explosion as asteroid deflection strategy.
- Power generation; see PACER
- Peaceful nuclear explosions
Nuclear weapons are largely seen as a 'deterrent' by most governments; the sheer scale of the destruction caused by a nuclear weapon has prevented much serious consideration of their use in warfare.
In the history of warfare, two nuclear weapons have been detonated—both by the United States in World War II. The first event occurred on the morning of 6 August 1945, when the United States dropped a uranium gun-type device code-named "Little Boy" on the Japanese city of Hiroshima. The second event occurred three days later when, again, the United States dropped a plutonium implosion-type device code-named "Fat Man" on the city of Nagasaki. These bombings resulted in the immediate deaths of around 120,000 people and more over time, because of the nuclear radiation. The use of these weapons was and remains controversial. (See Atomic bombings of Hiroshima and Nagasaki for a full discussion).
Since trinity, mankind (those few nations with capability) has detonated roughly 1700 nuclear explosions, all but 2 as tests. Nuclear 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 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; most nuclear weapons states publicly declared their nuclear status by means of a nuclear test.
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 TNT equivalent). Putative tests (like Vela Incident) have not been included.
|1945-07-16||Trinity||18–20||USA||First fission device test, first plutonium implosion detonation|
|1945-08-06||Little Boy||12–18||USA||Bombing of Hiroshima, Japan, first detonation of an enriched uranium gun-type device, first use of a nuclear device in military combat.|
|1945-08-09||Fat Man||18–23||USA||Bombing of Nagasaki, Japan, second and last use of a nuclear device in military combat.|
|1949-08-29||RDS-1||22||USSR||First fission weapon test by the USSR|
|1952-10-03||Hurricane||25||UK||First fission weapon test by the UK|
|1952-11-01||Ivy Mike||10,400||USA||First cryogenic fusion fuel "staged" thermonuclear weapon, primarily a test device and not weaponized|
|1952-11-16||Ivy King||500||USA||Largest pure-fission weapon ever tested|
|1953-08-12||Joe 4||400||USSR||First fusion weapon test by the USSR (not "staged")|
|1954-03-01||Castle Bravo||15,000||USA||First dry fusion fuel "staged" thermonuclear weapon; a serious nuclear fallout accident occurred|
|1955-11-22||RDS-37||1,600||USSR||First "staged" thermonuclear weapon test by the USSR (deployable)|
|1957-11-08||Grapple X||1,800||UK||First (successful) "staged" thermonuclear weapon test by the UK|
|1957-05-31||Orange Herald||720||UK||Largest boosted fission weapon ever tested. Intended as a fallback "in megaton range" in case British thermonuclear development failed.|
|1960-02-13||Gerboise Bleue||70||France||First fission weapon test by France|
|1961-10-31||Tsar Bomba||57,000||USSR||Largest thermonuclear weapon ever tested—scaled down from its initial 100 Mt design by 50%|
|1964-10-16||596||22||PR China||First fission weapon test by the People's Republic of China|
|1967-06-17||Test No. 6||3,300||PR China||First "staged" thermonuclear weapon test by the People's Republic of China|
|1968-08-24||Canopus||2,600||France||First "staged" thermonuclear weapon test by France|
|1974-05-18||Smiling Buddha||12||India||First fission nuclear explosive test by India|
|1998-05-11||Pokhran-II||60||India||First potential fusion/boosted weapon test by India; first deployable fission weapon test by India|
|1998-05-28||Chagai-I||40||Pakistan||First fission weapon (boosted) test by Pakistan|
|1998-05-30||Chagai-II||20||Pakistan||Second fission weapon (boosted) test by Pakistan|
|2006-10-09||2006 North Korean nuclear test||~1||North Korea||First fission plutonium-based device tested by North Korea; likely resulted as a fizzle|
|2009-05-25||2009 North Korean nuclear test||2-6||North Korea||First successful fission device tested 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.
Effects of nuclear explosions
The dominant effects of a nuclear weapon (the blast and thermal radiation) are the same physical damage mechanisms as conventional explosives, but the energy produced by a nuclear explosive is millions of times more per gram and the temperatures reached are in the tens of megakelvins. Nuclear weapons are quite different from regular weapons because of the huge amount of explosive energy they can put out and the different kinds of effects they make, like high temperatures and nuclear radiation.
The devastating impact of the explosion does not stop after the initial blast, as with regular explosives. A cloud of nuclear radiation travels from the epicenter of the explosion, causing an impact to life forms even after the heat waves have ceased. The radiation can cause genetic mutation, radiation poisoning, and death.
- Lists of nuclear disasters and radioactive incidents
- Soviet nuclear well collapses
- Visual depictions of nuclear explosions in fiction
- [2010 test] Kakodkar says Pokhran-II tests fully successful], 24 September 2009
- Pakistan Nuclear Weapons. Federation of American Scientists. December 11, 2002