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In physics, fission is a nuclear process, meaning it occurs in the nucleus of an atom. Fission is when the nucleus splits into two or more smaller nuclei plus some by-products. These by-products include free neutrons and photons (usually gamma rays). Fission releases substantial amounts of energy (the strong nuclear force binding energy). Fission can be induced by several methods, including bombarding the nucleus of a fissionable atom with another particle of the correct energy. Usually the other particle is a free neutron moving at the right speed. This free neutron is absorbed by the nucleus, making the nucleus unstable (much like a grocer's pyramid of oranges becomes unstable if someone throws another orange at it at the right speed). The unstable nucleus will then split into two or more pieces. These pieces are known as fission products and include two smaller nuclei, two or three other free neutrons, and some photons. The process releases a lot of energy compared to chemical reactions; the energy is released in the form of both photon radiation (like gamma rays) and in the kinetic energy (energy of motion) of the nuclei and neutrons.
The atomic nuclei released as fission products are of various chemical elements. Which elements are produced is somewhat random, but each nuclei usually ends up with about half the protons and neutrons of the original fissioned atom. Fission products are usually highly radioactive since these other nuclei are not stable isotopes. These isotopes then decay, releasing gamma rays and beta decayIn nuclear physics, beta decay (sometimes called neutron decay is a type of radioactive decay in which a beta particle (an electron or a positron) is emitted. In the case of electron emission, it is referred to as "beta minus" (β−); in the case radiation.
1 Inducing fission
- Though fission is most often / most easily started (induced) by the absorption of a free neutron, it can also be induced by throwing other things at a fissionable nucleus. These other things can include protons, other nuclei, or even very high amounts of high-energy photons (lots of gamma rays).
- Very infrequently, a fissionable nucleus will undergo spontaneous nuclear fission without an incoming neutron.
- Inducing fission is easiest in heavy elements, the heavier the better. Fission in any element heavier than ironThis article is about metallic iron. For the ironing device, see ironing manganese iron cobalt Fe Ru Full table General Name, Symbol, Number iron, Fe, 26 Chemical series transition metal Group, Period, Block 8 (VIIIB), 4 , d Density, Hardness 7874 kg/m3, produces energy, and fission in any element lighter than iron requires energy. The opposite is true of nuclear fusionIn physics, nuclear fusion (a thermonuclear reaction is a process in which two nuclei join, forming a larger nucleus and releasing energy. Nuclear fusion is the energy source which causes stars to shine, and hydrogen bombs to explode. It takes considerabl reactions - fusion in elements lighter than iron produces energy, and fusion in elements heavier than iron requires energy.
- The most frequently used elements to produce nuclear fission are uraniumUranium is a chemical element in the periodic table that has the symbol U and atomic number 92. A heavy, silvery-white, toxic, metallic , and naturally- radioactive element, uranium belongs to the actinide series and its isotope uranium-235 is used as the and plutoniumPlutonium is a radioactive, metallic, chemical element. It has the symbol Pu and the atomic number 94. Its atomic weight is 244. 06, its density 19,800 kg/m3. It is the element used in most modern nuclear weapons. The most important isotope of plutonium i. Uranium is the heaviest naturally occurring element; plutonium undergoes spontaneous fission reactions and has a limited half-lifeThis article describes the scientific meaning. For the computer game, see Half-Life''. For a quantity subject to exponential decay, the half-life is the time required for the quantity to fall to half of its initial value. Quantities subject to exponential. So, although other elements can be used, these have the best combination of abundance and ease of fission. See fissileIn nuclear engineering, a fissile material is one that is is capable of sustaining a chain reaction of nuclear fission. All fissile materials are equally capable of sustaining a chain reaction in which either thermal or slow neutrons or fast neutrons pred.
