![]() When fissionable material is in small pieces, the proportion of neutrons that escape through the relatively large surface area is great, and a chain reaction does not take place. The reaction can be controlled or moderated by introducing a substance that absorbs neutrons before they can react with more uranium atoms.\), a source of neutrons, and an explosive device for compressing it quickly into a small volume. Whether or not a chain reaction can occur depends on the energy of the neutrons that are released and how close the neighbor uranium atoms are. These two neutrons can go on to split other uranium nuclei, resulting in a nuclear chain reaction. In this particular reaction, one uranium nucleus breaks into a barium nucleus, a krypton nucleus, and two neutrons. A common fission reaction produces barium-141 and krypton-92. The term fission comes from the Latin word fissio, which means a cleaving or splitting. This process often produces gamma photons and releases a significant amount of energy. The energy from the neutrons can cause the uranium nucleus to break in any of a number of different ways. Nuclear fission is a nuclear reaction or a radioactive decay process in which the nucleus of an atom splits into two or more smaller, lighter nuclei. In nuclear power plants, energetic neutrons are directed into a sample of the isotope uranium-235. The critical mass of a fissionable material depends upon its nuclear properties (specifically, its nuclear fission cross-section ), density, shape, enrichment, purity, temperature, and surroundings. Other times, energy is added to a nucleus to overcome the nuclear binding energy holding the protons and neutrons together. In nuclear engineering, a critical mass is the smallest amount of fissile material needed for a sustained nuclear chain reaction. Sometimes this is supplied naturally, from radioactive decay of an element. What is a Chain Reaction A chain reaction in nuclear physics refers to the process during which nuclear fission reactions become self-sustaining. ![]() ![]() For example, the fission of one kilogram of uranium releases as much energy as burning around four billion kilograms of coal.Įnergy is required in order for fission to occur. The energy released by nuclear fission is considerable. This process is known as fission (see diagram below). However, the daughter nuclei may still be radioactive. When a U-235 nucleus absorbs an extra neutron, it quickly breaks into two parts. Other isotopes that can be induced to fission like this are plutonium-239, uranium-233, and thorium-232. The mass change and energy release yield smaller nuclei that are more stable than the original heavy nucleus. When nuclear fission is used to generate electricity, it is referred to as nuclear power.In this case, uranium-235 is used as the nuclear fuel and its fission is triggered by the absorption of a slow moving thermal neutron. The nucleus oscillates, so the repulsion may overcome the short-range attraction, causing the atom to split. The reason fission occurs is that energy upsets the balance between the electrostatic repulsion between positively-charged protons and the strong nuclear force that holds protons and neutrons together. In a nuclear power plant, this heat is used to boil water to produce steam that can be used to drive large turbines. One kind of nuclear reaction is fission, which occurs in a nuclear reactor and releases energy, usually in the form of heat and radiation. Fission is a type of nuclear reaction that may occur spontaneously or as a result of a particle striking an atomic nucleus. The energy that is released through a nuclear reaction or radioactive decay process. The original heavy atom is termed the parent nucleus, and the lighter nuclei are daughter nuclei. Fission is the splitting of an atomic nucleus into two or more lighter nuclei accompanied by energy release.
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