Weapons whose explosive output is exclusively from fission reactions are commonly referred to as atomic bombs or atom bombs (abbreviated as A-bombs). TypesДЄll existing nuclear weapons derive some of their explosive energy from nuclear fission reactions. Modernisation of weapons continues to this day. The Treaty on the Non-Proliferation of Nuclear Weapons aims to reduce the spread of nuclear weapons, but its effectiveness has been questioned. South Africa is the only country to have independently developed and then renounced and dismantled its nuclear weapons. Germany, Italy, Turkey, Belgium and the Netherlands are nuclear weapons sharing states. Israel is believed to possess nuclear weapons, though, in a policy of deliberate ambiguity, it does not acknowledge having them. The only countries known to have detonated nuclear weapons-and acknowledge possessing them-are (chronologically by date of first test) the United States, the Soviet Union (succeeded as a nuclear power by Russia), the United Kingdom, France, China, India, Pakistan, and North Korea. Only a few nations possess such weapons or are suspected of seeking them. Since the atomic bombings of Hiroshima and Nagasaki, nuclear weapons have been detonated over 2,000 times for testing and demonstration.

The ethics of these bombings and their role in Japan's surrender are subjects of debate. These bombings caused injuries that resulted in the deaths of approximately 200,000 civilians and military personnel. Army Air Forces detonated a plutonium implosion-type fission bomb nicknamed ' Fat Man' over the Japanese city of Nagasaki. Army Air Forces detonated a uranium gun-type fission bomb nicknamed ' Little Boy' over the Japanese city of Hiroshima three days later, on August 9, the U.S.

Nuclear weapons have only twice been used in war, both times by the United States against Japan near the end of World War II. 7.1 Effects of nuclear explosions on human health.Nuclear weapons have been deployed twice in war, by the United States against the Japanese cities of Hiroshima and Nagasaki in 1945 during World War II. Since they are weapons of mass destruction, the proliferation of nuclear weapons is a focus of international relations policy. ДЄ nuclear device no larger than a conventional bomb can devastate an entire city by blast, fire, and radiation. A thermonuclear weapon weighing as little as 600 pounds (270В kg) can release energy equal to more than 1.2 megatonnes of TNT (5.0В PJ). Nuclear bombs have had yields between 10 tons TNT (the W54) and 50 megatons for the Tsar Bomba (see TNT equivalent). The first thermonuclear ('hydrogen') bomb test released energy approximately equal to 10В million tons of TNT (42В PJ). The first test of a fission ('atomic') bomb released an amount of energy approximately equal to 20,000 tons of TNT (84 TJ). Both bomb types release large quantities of energy from relatively small amounts of matter. A nuclear weapon (also known as an atom bomb, atomic bomb, nuclear bomb or nuclear warhead, and colloquially as an A-bomb or nuke) is an explosive device that derives its destructive force from nuclear reactions, either fission (fission bomb) or a combination of fission and fusion reactions ( thermonuclear bomb).

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