A nuclear reactor is a device used to initiate and control a fission nuclear chain reaction. They are used for commercial electricity, marine propulsion, weapons production and research. When a fissile nucleus, usually uranium-235 or plutonium-239, absorbs a neutron, it splits into lighter nuclei, releasing energy, gamma radiation, and free neutrons, which can induce further fission in a self-sustaining chain reaction. Reactors stabilize this with systems of active and passive control, varying the presence of neutron absorbers and moderators in the core, maintaining criticality with delayed neutrons. Fuel efficiency is exceptionally high;low-enriched uranium has an energy density 120,000 times higher than coal.
A pressurized water reactor (PWR) is a type of light-water nuclear reactor. PWRs constitute the large majority of the world's nuclear power plants.
A boiling water reactor (BWR) is a type of nuclear reactor used for the generation of electrical power. It is the second most common type of electricity-generating nuclear reactor after the pressurized water reactor (PWR).
A nuclear meltdown is a severe nuclear reactor accident that results in core damage from overheating. The term nuclear meltdown is not officially defined by the International Atomic Energy Agency or by the United States Nuclear Regulatory Commission. It has been defined to mean the accidental melting of the core of a nuclear reactor, however, and is in common usage a reference to the core's either complete or partial collapse.
The RBMK is a class of graphite-moderated nuclear power reactor designed and built by the Soviet Union. It is somewhat like a boiling water reactor as water boils in the pressure tubes. It is one of two power reactor types to enter serial production in the Soviet Union during the 1970s, the other being the VVER reactor. The name refers to its design where instead of a large steel pressure vessel surrounding the entire core, the core is surrounded by a cylindrical annular steel tank inside a concrete vault and each fuel assembly is enclosed in an individual 8 cm (inner) diameter pipe. The channels also contain the coolant, and are surrounded by graphite.
The A2W reactor is a naval nuclear reactor used by the United States Navy to provide electricity generation and propulsion on warships. The A2W designation stands for:
A loss-of-coolant accident (LOCA) is a mode of failure for a nuclear reactor; if not managed effectively, the results of a LOCA could result in reactor core damage. Each nuclear plant's emergency core cooling system (ECCS) exists specifically to deal with a LOCA.
The light-water reactor (LWR) is a type of thermal-neutron reactor that uses normal water, as opposed to heavy water, as both its coolant and neutron moderator; furthermore a solid form of fissile elements is used as fuel. Thermal-neutron reactors are the most common type of nuclear reactor, and light-water reactors are the most common type of thermal-neutron reactor.
Passive nuclear safety is a design approach for safety features, implemented in a nuclear reactor, that does not require any active intervention on the part of the operator or electrical/electronic feedback in order to bring the reactor to a safe shutdown state, in the event of a particular type of emergency. Such design features tend to rely on the engineering of components such that their predicted behaviour would slow down, rather than accelerate the deterioration of the reactor state; they typically take advantage of natural forces or phenomena such as gravity, buoyancy, pressure differences, conduction or natural heat convection to accomplish safety functions without requiring an active power source. Many older common reactor designs use passive safety systems to a limited extent, rather, relying on active safety systems such as diesel-powered motors. Some newer reactor designs feature more passive systems; the motivation being that they are highly reliable and reduce the cost associated with the installation and maintenance of systems that would otherwise require multiple trains of equipment and redundant safety class power supplies in order to achieve the same level of reliability. However, weak driving forces that power many passive safety features can pose significant challenges to effectiveness of a passive system, particularly in the short term following an accident.
A containment building is a reinforced steel, concrete or lead structure enclosing a nuclear reactor. It is designed, in any emergency, to contain the escape of radioactive steam or gas to a maximum pressure in the range of 275 to 550 kPa. The containment is the fourth and final barrier to radioactive release, the first being the fuel ceramic itself, the second being the metal fuel cladding tubes, the third being the reactor vessel and coolant system.
The Advanced CANDU reactor (ACR), or ACR-1000, was a proposed Generation III+ nuclear reactor design, developed by Atomic Energy of Canada Limited (AECL). It combined features of the existing CANDU pressurised heavy water reactors (PHWR) with features of light-water cooled pressurized water reactors (PWR). From CANDU, it took the heavy water moderator, which gave the design an improved neutron economy that allowed it to burn a variety of fuels. It replaced the heavy water cooling loop with one containing conventional light water, reducing costs. The name refers to its design power in the 1,000 MWe class, with the baseline around 1,200 MWe.
The AP1000 is a nuclear power plant designed and sold by Westinghouse Electric Company. The plant is a pressurized water reactor with improved use of passive nuclear safety and many design features intended to lower its capital cost and improve its economics.
The Sanmen Nuclear Power Station is a nuclear power station in Sanmen County, Zhejiang, China. Sanmen is the first implementation of the AP1000 pressurized water reactor (PWR) developed by Westinghouse Electric Company.
The three primary objectives of nuclear reactor safety systems as defined by the U.S. Nuclear Regulatory Commission are to shut down the reactor, maintain it in a shutdown condition and prevent the release of radioactive material.
A nuclear reactor coolant is a coolant in a nuclear reactor used to remove heat from the nuclear reactor core and transfer it to electrical generators and the environment. Frequently, a chain of two coolant loops are used because the primary coolant loop takes on short-term radioactivity from the reactor.
General Electric's BWR product line of boiling water reactors represents the designs of a relatively large (~18%) percentage of the commercial fission reactors around the world.
The APR-1400 is an advanced pressurized water nuclear reactor designed by the Korea Electric Power Corporation (KEPCO). Originally known as the Korean Next Generation Reactor (KNGR), this Generation III reactor was developed from the earlier OPR-1000 design and also incorporates features from the US Combustion Engineering (C-E) System 80+ design. Currently in South Korea there are 4 units in operation, and 2 units in construction. Four units are completed and in commercial operation in the United Arab Emirates at Barakah.
Shidao Bay Nuclear Power Plant, commonly known as Shidaowan, is a nuclear power plant in Shandong province, China. The site is located near the Xiqianjia village in Ningjin subdistrict, Rongcheng, Weihai, Shandong. The plant is located about 23 kilometres (14 mi) south of Rongcheng City, 14 kilometres (8.7 mi) northwest of Shidao, and 68 kilometres (42 mi) southeast of Weihai City.
An organic nuclear reactor, or organic cooled reactor (OCR), is a type of nuclear reactor that uses some form of organic fluid, typically a hydrocarbon substance like polychlorinated biphenyl (PCB), for cooling and sometimes as a neutron moderator as well.
The Indian Pressurized Water Reactor-900 (IPWR-900) is a class of pressurized water reactors being designed by the Bhabha Atomic Research Centre (BARC) in partnership with the Nuclear Power Corporation of India Limited to supplement the Indian three-stage nuclear power programme.
