Nuclear power plant definition
A nuclear power plant is a facility for the production of electricity using nuclear energy.
Its operation is similar to a thermic power plant. The difference is that the power source from a nuclear plant is nuclear fission of certain atoms while in a thermic power plant the heat source (thermal energy) from burning of one or more fossil fuels (coal, natural gas , fuel ..). As in a conventional thermal power plant the heat is used to generate steam that drives a steam turbine connected to a generator that produces electricity.
The thermal energy that nuclear power uses to generate electricity is generated by a nuclear reactor. Within the nuclear reactor fission reactions in chain occur in controlled way. The element to fission is natural uranium or enriched uranium. Enriched uranium is natural uranium with a proportion of the isotope uranium-235 higher.
In addition to the reactor, a nuclear power plant always consists of a steam turbine, an alternator, two or three -primary, secondary, and tertiary- circuits and one or more cooling towers condenser fluid, usually water. The overall efficiency is between 30% and 40%.
It is usually considered the operating lifetime of a nuclear power plant in about thirty years. The main problem is that no one knows what to do with nuclear waste they generate.
Basic operation of a nuclear power plant
In a nuclear power plant, energy is extracted from the nucleus of atoms through its division (nuclear fission) since breaking release the binding energy within the atom linking the particulates. Nuclear fission is caused by artificial and controlled manner. In this, a large atom of a chemical element fires a neutron, a small particle at a certain speed, which breaks the atom (breaking its core, formed by neutrons and protons linked together by highly energetic links) in an exothermic nuclear reaction, ie energy is released as heat (thermal energy).
To achieve that energy obtained be greater than the energy used, it is necessary that nuclear reactions be chain reactions. Thus, although much energy is needed to start the nuclear chain reaction, once the reaction is initiated not much energy is required to maintain it, and there comes a time in which the energy obtained is higher than the energy used. To achieve this it is necessary that the largest chemical element (called heavy, with a high atomic mass) be also radioactive. The element used often is a rare isotope of uranium.
This is done in the nuclear reactor, wher also they pose tubes with a fluid called refrigerant, which is responsible for transporting the heat (thermal energy) extracted from the uranium from the reservoir, cooling it. This thermal energy is used to heat water to boiling, and water vapor pressure is used to move the blades of a turbine, thus we have transformed the thermal energy to mechanical energy. Then, the electric generator (or alternator) converts this mechanical energy to electrical energy.
This process is explained in more detail in the section: operation of a nuclear power plant.
A nuclear reactor is a device that produces heat (heat energy or thermal energy), based on release it from the core of atoms when they are broken when they are bombarded with neutrons. After break each nucleus into two fission fragments, in addition to releasing heat, also it emits neutrons, which break other nuclei in a chain reaction. In a reactor cooling and security are very important.
In the world there are different types of nuclear reactors, all of them are fission reactors, into the various nuclear power . The UN classifies them as follows:
- Pressurized Water Reactor (PWR and VVER). They use high pressure water to produce steam to the steam generators. They have three circuits.
- Boiling water reactor (BWR): The second most common in the world. Water boils, generating steam directly into the reactor core. They have only two circuits.
- Pressurized heavy water reactor (PHWR): Use high pressure heavy water as a neutron moderator and coolant.
- Gas Reactor (GCR: AGR and Magnox): They use graphite as the neutron moderator and carbon dioxide as a refrigerant in a gaseous state.
- Graphite moderated and cooled by light water reactor (LGR and RBMK): Models of Russian origin. The "light water" is plain water.
- Fast Reactor (LBR, or LMFBR): No slows neutrons chain reaction and cooled by liquid sodium. They are at the prototype stage and research.
Last review: February 1, 2016