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Nuclear Reactors

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In nuclear fission, the nucleus of a heavy element, such as uranium or plutonium, is bombarded by a  neutron, which it absorbs. The product which is generated by fission reaction is unstable and split in to two lighter nuclei by emitting extra neutrons. In a properly designed nuclear reactor, it is possible to have some of the neutrons from the first fission event travel through the reactor's core and get absorbed by another uranium nucleus to cause another fission event.

Definition

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A Nuclear reactor is a device designed to sustain the fission process in a controlled chain reaction. The nuclear fission process is accompanied by the release of a large amount of energy, typically 200MeV per reaction. Much of this energy appears as the kinetic (or motion) energy of the fission product nuclei, which is then converted to thermal energy (or heat) as the fission products slow down in the reactor fuel material. This thermal energy is removed from the reactor core and used either to create steam to generate electricity or as process heat, as in the desalination of seawater.

Nuclear Reactor

Types

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There are several types of nuclear reactor, including power reactors, production reactors, test and research reactors, reactors for naval propulsion and space nuclear reactors.

Nuclear power reactors provide thermal energy (heat) for the production of electricity using a traditional steam generating plant. Production reactors provide a large number of neutrons to make a variety of radioactive isotopes and elements not available in nature.

The production reactor supports various neutron capture reactions in its core and any blanket regions surrounding the core.

Research and test reactors represent a wide range of "non-power" reactors that are primarily used to conduct research, development, testing and education. Research and test reactors are quite small compared with power reactors whose primary function is the generation of electricity.

The basic naval nuclear reactor
used to propel submarines and surface ships in navies around the world is a general compact pressurized water reactor that has a portion of its power plant package integrated into the ship's steel hull.

The nuclear fission reactor
has two distinctly different applications in the exploration of outer space.

Working

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Basically, a nuclear reactor is a machine which controls nuclear chain reactions and producing thermal energy during this reaction in a controlled manner. In the first increment of time, a neutron causes the fission of a uranium-235 nucleus, releasing energy as well as additional neutrons. In the next generation, both of the released neutrons cause another wave of nuclear fissions, with four neutrons being released. These four neutrons then find other uranium-235 nuclei to split. The first prerequisite in maintaining a self sustaining neutron chain reaction is that there is enough fissile material available in the right configuration. Nuclear reactor engineers refer to the amount of material capable of sustaining a continuous chain reaction in a reactor core as the critical mass. The fuel is the heart of the reactor core. Fuel assemblies are fuel rods conveniently packaged into bundles to accommodate the loading of fresh fuel and unloading of spent fuel from the core. The controlled rods generally have cross shaped blades containing materials that absorb neutrons. Reactor operators use the control rods to regulate the rate of the chain reaction taking place in the core. A coolant usually water is pumped through the reactor core to carry away the large amount of thermal energy released by nuclear fission reactions. The moderator in the reactor is used to control the speed of the reaction. As a result, slow down process of neutrons are taking place.

Modular Nuclear Reactors

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These reactors are the part of nuclear power plant. It has high efficiency and greater nuclear security. Small reactors are nothing but the reactors which produce the the output electricity less than 300MWe.