Nuclear weapons tests are experiments conducted to assess the performance, effectiveness, and explosive capacity of nuclear weapons. These tests provide valuable information on how weapons work, how detonations are affected by different conditions, and how personnel, structures, and equipment are affected when exposed to nuclear explosions. Additionally, nuclear tests have often been used as a symbol of scientific and military strength. In 1963, three of the four nuclear states at the time (the United Kingdom, United States, and Soviet Union) and many non-nuclear states signed the Limited Test Ban Treaty, vowing to refrain from testing nuclear weapons in the atmosphere, underwater, or in outer space.
This was followed by the Comprehensive Nuclear-Test-Ban Treaty (CTBT) in 1996, which is a legally binding global ban on the testing of nuclear explosives. Despite these treaties, there have been at least three suspected but unrecognized nuclear explosions (see list of alleged nuclear tests), including the Vela Incident. Recognizing that even underground tests were causing serious damage, and eager to end the era of nuclear testing, the international community adopted the CTBT. Studies and evaluations have estimated that cancer deaths due to global radiation doses from nuclear test programs in the atmosphere of the five nuclear-weapon States amount to hundreds of thousands.
This is contrary to the spirit of disarmament and reduction of the global nuclear arsenal that has been the intended objective of the world's nuclear states since the 1960s. At BEEF (Big Explosives Experimental Facility), researchers subject (non-nuclear) materials found in nuclear weapons to extremely powerful conventional explosions to study how they would respond to a real nuclear explosion. The CTBT has not yet entered into force. The partial nuclear-test-ban treaty makes it illegal to detonate any nuclear explosion anywhere except underground, in order to reduce atmospheric precipitation.
Because nuclear testing is considered to promote the development of nuclear weapons, many oppose future testing as an acceleration of the arms race. The United States ended all underground nuclear tests in the early 1990s on the eve of the CTBT, despite protests from the heads of its three national weapons laboratories. The first test was conducted to confirm that the design of an implosion-type nuclear weapon was feasible and to give an idea of what size and effects a nuclear explosion would have before they were used in combat against Japan. The preamble of the treaty banning nuclear weapons acknowledges the disproportionate impact of nuclear weapons activities on indigenous peoples. Only three countries - India, Pakistan, and North Korea - have conducted explosive nuclear tests since the CTBT was signed 25 years ago.