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NuclearpBomb - Nuclear Bomb You have probably read in...

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Nuclear Bomb You have probably read in history books about the atomic bombs used in World War II. You may also have seen fictional movies where nuclear weapons were launched or detonated ( Fail Safe , Dr. Strangelove , The Day After , Testament , Fat Man and Little Boy , The Peacemaker , just to name a few). In the news, while many countries have been negotiating to disarm their arsenals of nuclear weapons, other countries have been developing nuclear weapons programs. Photo courtesy NARA Atomic Cannon Test, 1953 We have seen that these devices have incredible destructive power, but how do they work? In this article, you will learn about the physics that makes a nuclear bomb so powerful, how nuclear bombs are designed and what happens after a nuclear explosion. Nuclear bombs involve the forces, strong and weak, that hold the nucleus of an atom together, especially atoms with unstable nuclei (see How Nuclear Radiation Works for details). There are two basic ways that nuclear energy can be released from an atom: Nuclear fission - You can split the nucleus of an atom into two smaller fragments with a neutron. This method usually involves isotopes of uranium (uranium-235, uranium-233) or plutonium-239. Nuclear fusion -You can bring two smaller atoms, usually hydrogen or hydrogen isotopes (deuterium, tritium), together to form a larger one (helium or helium isotopes); this is how the sun produces energy. In either process, fission or fusion, large amounts of heat energy and radiation are given off. To build an atomic bomb, you need: A source of fissionable or fusionable fuel A triggering device A way to allow the majority of fuel to fission or fuse before the explosion occurs (otherwise the bomb will fizzle out) The first nuclear bombs were fission devices, and the later fusion bombs required a fission-bomb trigger. We will discuss the designs of the following devices: Fission bombs (in general)
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Gun-triggered fission bomb (Little Boy), which was detonated over Hiroshima, Japan, in 1945 Implosion-triggered fission bomb (Fat Man), which was detonated over Nagasaki, Japan, in 1945 Fusion bombs (in general) Teller-Ulam design of a hydrogen fusion bomb , which was test-detonated on Elugelap Island in 1952 A fission bomb uses an element like uranium-235 to create a nuclear explosion. If you have read How Nuclear Radiation Works , then you understand the basic process behind radioactive decay and fission. Uranium-235 has an extra property that makes it useful for both nuclear-power production and nuclear-bomb production -- U-235 is one of the few materials that can undergo induced fission . If a free neutron runs into a U-235 nucleus, the nucleus will absorb the neutron without hesitation, become unstable and split immediately.
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