Tests have been carried out aboard barges, atop towers, suspended from balloons, on the Earth's surface, more than 600 meters underwater and more than 200 meters underground. Nuclear weapons tests are experiments that are carried out to determine the effectiveness, performance and explosive capacity of nuclear weapons. Nuclear weapons testing provides practical information on how weapons work, how detonations are affected by different conditions, and how personnel, structures and equipment are affected when subjected to nuclear explosions. However, nuclear tests have often been used as an indicator of scientific and military strength.
Many tests have been openly political in intention; most nuclear-weapon states publicly declared their nuclear status through a nuclear test. For nuclear weapons testing, a salvo is defined as two or more underground nuclear explosions carried out at a test site within an area bounded by a circle two kilometers in diameter and carried out in a total period of time of 0.1 seconds. Not only does it seek the total abolition of nuclear weapons, but it also requires, for the first time, international cooperation to help victims of such tests and help remedy contaminated environments. Recognizing that even underground tests caused serious damage, and desirous of ending the era of nuclear testing, the international community adopted in 1996 the Comprehensive Nuclear-Test-Ban Treaty.
In addition to these designations, nuclear tests are also often classified according to the purpose of the test itself. Israel is widely believed to have a sizeable nuclear arsenal, although it has never tested it, unless it participates in Vela. Growing global concern about the consequences of atmospheric tests, including the effects of strontium-90 on nursing mothers and their babies, was a catalyst for the conclusion of the Partial Test Ban Treaty in 1963, which banned nuclear tests in the atmosphere, underwater and in space, but did not underground. Since then, nuclear testing has become a controversial topic in the United States, and several politicians say future testing may be necessary to maintain aging Cold War warheads.
Not all countries suspended atmospheric tests, but because the United States and the Soviet Union were responsible for approximately 86% of all nuclear tests, compliance substantially lowered the overall level. One of the main means by which rain and nuclear waste are transferred to people through the atmosphere is through the production and consumption of dairy products. Logistics would likely lead a terrorist organization to explode a small-scale nuclear fission device at ground level. However, by the 1950s the United States had established a dedicated test site on its own territory (Nevada Test Site) and was also using a site in the Marshall Islands (Pacific Proving Grounds) to conduct extensive atomic and nuclear tests.
People within 250 meters of a 0.01 kiloton nuclear detonation would receive doses of 4 Gy of the initial whole-body radiation, causing the mortality of almost half of the people exposed. In 1963, three (United Kingdom, United States, Soviet Union) of the four nuclear states at the time 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.