| Nuclear testing is experimentation with nuclear | | | | their mushroom cloud can generate large amounts |
| weapons. Throughout the twentieth century, | | | | of nuclear fallout due to irradiation of the debris. |
| most nations that have developed nuclear | | | | High-altitude nuclear tests can generate an |
| weapons have staged tests of them. Testing | | | | electromagnetic pulse, and charged particles |
| nuclear weapons can yield information about how | | | | resulting from the blast can cross hemispheres to |
| the weapons work, as well as how the weapons | | | | create an auroral display. |
| behave under various conditions and how | | | | Underwater testing results from nuclear devices |
| structures behave when subjected to nuclear | | | | being detonated underwater, usually moored to a |
| explosions. Additionally, nuclear testing has often | | | | ship or a barge (which is subsequently destroyed |
| been used as an indicator of scientific and military | | | | by the explosion). Tests of this nature have |
| strength, and many tests have been overtly | | | | usually been conducted to evaluate the effects of |
| political in their intention; most nuclear weapons | | | | nuclear weapons against naval vessels (such as in |
| states publicly declared their nuclear status by | | | | Operation Crossroads), or to evaluate potential |
| means of a nuclear test. | | | | sea-based nuclear weapons (such as nuclear |
| The first atomic test was detonated by the | | | | torpedoes or depth-charges). Underwater tests |
| United States at the Trinity site on July 16, 1945, | | | | close to the surface can disperse large amounts |
| with a yield approximately equivalent to 20 | | | | of radioactive water and steam, contaminating |
| kilotons. The first hydrogen bomb, codenamed | | | | nearby ships or structures. |
| "Mike", was tested at the Enewetak atoll in the | | | | Underground testing refers to nuclear tests which |
| Marshall Islands on November 1, 1952, also by the | | | | are conducted under the surface of the earth, at |
| United States. The largest nuclear weapon ever | | | | varying depths. Underground nuclear testing made |
| tested was the "Tsar Bomba" of the Soviet Union | | | | up the majority of nuclear tests by the United |
| at Novaya Zemlya on October 30, 1961, with an | | | | States and the Soviet Union during the Cold War, |
| estimated yield of around 50 megatons. | | | | on account of other forms of nuclear testing |
| In 1963, all nuclear and many non-nuclear states | | | | being banned by the Limited Test Ban Treaty in |
| signed the Limited Test Ban Treaty, pledging to | | | | 1963. When the explosion is fully contained, |
| refrain from testing nuclear weapons in the | | | | underground nuclear testing emits a negligible |
| atmosphere, underwater, or in outer space. The | | | | amount of fallout. However, underground nuclear |
| treaty permitted underground tests. France | | | | tests can "vent" to the surface, producing |
| continued atmospheric testing until 1974, while | | | | considerable amounts of radioactive debris as a |
| China continued up until 1980. The last | | | | consequence. Underground testing can result in |
| underground test by the United States was in | | | | seismic activity depending on the yield of the |
| 1992, the Soviet Union in 1990, the United | | | | nuclear device, and generally result in the creation |
| Kingdom in 1991, and both France and China | | | | of subsidence craters. In 1976, the United States |
| continued testing up until 1996. After adopting the | | | | and the USSR agreed to limit the maximum yield |
| Comprehensive Test Ban Treaty in 1996, all of | | | | of underground tests to 150 kt with the |
| these states have pledged to discontinue all | | | | Threshold Test Ban Treaty. |
| nuclear testing. Non-signatories India and Pakistan | | | | Separately from these designations, nuclear tests |
| both last tested nuclear weapons in 1998. | | | | are also often categorized by the purpose of the |
| The most recent nuclear test was announced by | | | | test itself. Tests which are designed to garner |
| North Korea on October 9, 2006. See 2006 North | | | | information about how (and if) the weapons |
| Korean nuclear test for more information. | | | | themselves work are weapons related tests, |
| Types of nuclear testing | | | | while tests designed to gain information about the |
| Nuclear weapons tests have been historically | | | | effects of the weapons themselves on structures |
| broken into categories (by treaties) reflecting in | | | | or organisms are known as weapons effects |
| what sort of medium or location the test has | | | | tests. Additional types of nuclear tests are |
| been conducted: atmospheric, underwater, and | | | | possible as well (such as nuclear tests which are |
| underground. | | | | also part of anti-ballistic missile testing). |
| Atmospheric testing designates explosions which | | | | Nuclear-weapons-related testing which purposely |
| take place in or above the atmosphere. Generally | | | | results in no yield is known as subcritical testing, |
| these have occurred as devices detonated on | | | | referring to the lack of a creation of a critical |
| towers, balloons, barges, islands, or dropped from | | | | mass of fissile material. Additionally, there have |
| airplanes. A limited number of high-altitude nuclear | | | | been non-nuclear simulations of nuclear tests using |
| explosions also conducted, generally fired from | | | | conventional explosives (such as the Minor Scale |
| rockets. Nuclear explosions which are close | | | | U.S. test in 1985). |
| enough to the ground to draw dirt and debris into | | | | |