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The mushroom cloud of the atomic bombing of Nagasaki, Japan, in 1945 lifted nuclear fallout some 60,000 feet (18 km) above the epicenter. A nuclear weapon is a weapon that derives its energy from nuclear reactions and has enormous destructive power - a single nuclear weapon is capable of destroying a city. Nuclear weapons have been used only twice for war, by the United States against the Japanese cities of Hiroshima and Nagasaki during World War II. They have been used many hundreds of times, however, for the nuclear testing undertaken by many countries.
The declared nuclear powers are the United States, Russia, United Kingdom, FranceThe French Republic or France ( French: Republique francaise or France is a country whose metropolitan territory is located in western Europe, and which is further made up of a collection of overseas islands and territories located in other continents., People's Republic of ChinaThe People's Republic of China PRC comprises most of the cultural, historic, and geographic area known as China. Since its founding in 1949, it has been led by the Communist Party of China (CPC). It is the world's most populous country, with a population, IndiaThe Republic of India is a large multicultural country in South Asia, with a population of over one billion. The Indian economy is the fourth largest in the world, in terms of purchasing power parity, and is the world's second-fastest growing economy. and PakistanIslami Jamhuria Pakistan ( In Detail) ( In Detail) National motto: Iman, Ittehad, Nazm( Urdu: "Faith, Unity, Discipline" Official Language(s) Urdu, English Capital Islamabad Largest City Karachi President General Pervez Musharraf Prime Minister Shaukat Az. In addition, IsraelThis article discusses the State of Israel. For other meanings of Israel see Israel (disambiguation). The State of Israel Medinat Yisrael in Hebrew, Daulat Israil in Arabic) is a country in the Middle East on the eastern edge of the Mediterranean Sea. is widely believed to possess nuclear weapons though it refuses to publicly state whether it possesses them or not (see Israel and weapons of mass destructionIsrael is very widely believed to possess a substantial arsenal of nuclear weapons and intermediate-range ballistic missiles to deliver them. There is also speculation that it may have chemical and biological weapons programs. Israel acceded to the Geneva). North KoreaThe Democratic People's Republic of Korea DPRK Korean: Choson Minjujuui Inmin Konghwaguk Hangul: ; Hanja: ), commonly known as North Korea is a country in eastern Asia, covering the northern half of the peninsula of Korea. To the south it borders South Ko has allegedly admitted to American diplomats that it possesses nuclear weapons (though this has not been substantiated); UkraineUkraine Ukrayina in Ukrainian; in Russian) is a republic in eastern Europe which borders the Black Sea to the south, the Russian Federation to the east, Belarus to the north, Poland, Slovakia and Hungary to the west and Romania and Moldova to the west and may possess a nuclear stockpile due to a clerical error; and Iran is allegedly developing the capacity to produce its own nuclear arsenal. See the list of countries with nuclear weapons for more details.
Non-weaponized nuclear explosives have also been proposed for various civilian uses.
1 Types of weapons
1.1 Common types
1.1.1 Fission bombs
Fission bombs derive their power from nuclear fission, where heavy nuclei ( uranium or plutonium) split into lighter elements when bombarded by neutrons (producing more neutrons which bombard other nuclei, triggering a nuclear chain reaction). These are historically called atom bombs or A-bombs, though this name is not precise due to the fact that chemical reactions release energy from atomic bonds and fusion is no less atomic than fission. Despite this possible confusion, the term atom bomb has still been generally accepted to refer specifically to nuclear weapons, and most commonly to pure fission devices.
1lb (0.45kg) of U-235 can release over 36 million million joules of energy.
1 atom of U-235 can produce around 200 million electron volts.
