Nuclear explosion

1953 at the Ne Operation Upshot-Knothole nuclear test series.

The Greenhouse George test early fireball.

Nuclear weapons
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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.

History

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.

Nuclear weapons

Main articles: Nuclear weapons and History of nuclear weapons

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).

Nuclear testing

Main article: Nuclear testing

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.

Date	Name	Yield (kT)	Country	Significance
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; largest nuclear detonation conducted by United States
1955-11-22	RDS-37	1,600	USSR	First "staged" thermonuclear weapon test by the USSR (deployable)
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.
1957-11-08	Grapple X	1,800	UK	First (successful) "staged" thermonuclear weapon test by the UK
1960-02-13	Gerboise Bleue	70	France	First fission weapon test by France
1961-10-31	Tsar Bomba	50,000	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	2-12	North Korea	First fission plutonium-based device tested by North Korea
2009-05-25	2009 North Korean nuclear test	1-20	North Korea	Successful fission device tested by North Korea
2013-02-16	2013 North Korean nuclear test	9	North Korea
2016-01-06	2016 North Korean nuclear test	6-9	North Korea	Most recent nuclear test

"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

Main article: 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.

See also

• Lists of nuclear disasters and radioactive incidents
• Soviet nuclear well collapses
• Visual depictions of nuclear explosions in fiction