Nuclear reactor| A system utilizing nuclear fission is carried out in a controlled and self-sustaining manner. Neutrons are used to fission the nuclear fuel, and the fission reaction produces not only energy and radiation but also additional neutrons. Thus a neutron chain reaction ensues. A nuclear reactor provides the assembly of materials to sustain and control the neutron chain reaction, to appropriately transport the heat produced from...
Reactor coolants| Coolants are selected for specific applications on the basis of their heat-transfer capability, physical properties, and nuclear properties. Water has many desirable characteristics. It was employed as the coolant in many of the first production reactors, and most power reactors still utilize water as the coolant. In a boiling-water reactor (BWR; see illustration),the water boils directly in...
Plant balance| The nuclear chain reaction in the reactor core produces energy in the form of heat, as the fission fragments slow down and dissipate their kinetic energy in the fuel. This heat must be removed efficiently and at the same rate it is being generated in order...
Core design control| A typical reactor core for a power reactor consists of the fuel element rods supported by a grid-type structure inside vessel. Structural materials employed in reactor systems must possess suitable nuclear and physical properties and...
Reactor application| Applications. Reactor applications include mobile, stationary, and packaged power plants; production of fissionable fuels (plutonium and uranium-233) for military and commercial applications; research, testing, teaching-demonstration, and experimental facilities; space and process heat; dual-purpose design; and special applications. The potential use of reactor radiation or...
How a nuclear reactor works| A nuclear reactor exploits the innate instability of some atoms—in general, those that have a large atomic number or that contain an imbalance of protons and neutrons—which break apart (fission) at random times, releasing photons, neutrons, electrons, and alpha particles. For some nuclides...
Nuclear fuels| Materials whose ability to release energy derives from specific properties of the atom's nucleus. In general, energy can be released by combining two light nuclei to form a heavier one, a process called nuclear fusion; by splitting a heavy nucleus into two fragments of intermediate mass, a process called...
Reactor byproducts| The neutron flow inside a reactor bombards, and by bombarding changes, the nuclei of many atoms in the reactor. The longer a unit of nuclear fuel remains in a reactor, therefore, the more altered nuclei it contains. Most of the new atoms formed are radioactive nuclides such as...
Production of heat and nuclear materials| The transmutation of nonfissionable materials to fissionable materials in nuclear reactors has made possible the large-scale production of atomic energy. The excess nuclear fuel produced can be extracted and used in other reactors or in nuclear weapons. The heat energy released by fission in...
Passive Nuclear Safety| Passive nuclear safety describes a safety feature of a nuclear reactor that does not require operator action or electronic feedback in order to shut down safely in the event of a particular type of emergency (usually overheating resulting from a loss of coolant or loss of coolant flow). Such reactors tend to rely more on the engineering of components such that their predicted behaviour according to...
