A nuclear reactor is a device used to initiate and control a fission nuclear chain reaction or nuclear fusion reactions. Nuclear reactors are used at nuclear power plants for electricity generation and in nuclear marine propulsion. Heat from nuclear fission is passed to a working fluid, which in turn runs through steam turbines. These either drive a ship's propellers or turn electrical generators' shafts. Nuclear generated steam in principle can be used for industrial process heat or for district heating. Some reactors are used to produce isotopes for medical and industrial use, or for production of weapons-grade plutonium. As of 2022, the International Atomic Energy Agency reports there are 422 nuclear power reactors and 223 nuclear research reactors in operation around the world.
The pebble-bed reactor (PBR) is a design for a graphite-moderated, gas-cooled nuclear reactor. It is a type of very-high-temperature reactor (VHTR), one of the six classes of nuclear reactors in the Generation IV initiative.
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 Pebble Bed Modular Reactor (PBMR) is a particular design of pebble bed reactor developed by South African company PBMR (Pty) Ltd from 1994 until 2009. PBMR facilities include gas turbine and heat transfer labs at the Potchefstroom Campus of North-West University, and at Pelindaba, a high pressure and temperature helium test rig, as well as a prototype fuel fabrication plant. A planned test reactor at Koeberg Nuclear Power Station was not built.
A fast-neutron reactor (FNR) or fast-spectrum reactor or simply a fast reactor is a category of nuclear reactor in which the fission chain reaction is sustained by fast neutrons, as opposed to slow thermal neutrons used in thermal-neutron reactors. Such a fast reactor needs no neutron moderator, but requires fuel that is relatively rich in fissile material when compared to that required for a thermal-neutron reactor. Around 20 land based fast reactors have been built, accumulating over 400 reactor years of operation globally. The largest of this was the Superphénix Sodium cooled fast reactor in France that was designed to deliver 1,242 MWe. Fast reactors have been intensely studied since the 1950s, as they provide certain decisive advantages over the existing fleet of water cooled and water moderated reactors. These are:
Rudolf Schulten —professor at RWTH Aachen University—was the main developer of the pebble bed reactor design, which was originally invented by Farrington Daniels. Schulten's concept compacts silicon carbide-coated uranium granules into hard, billiard-ball-like graphite spheres to be used as fuel for a new high temperature, helium-cooled type of nuclear reactor.
Generation IVreactors are nuclear reactor design technologies that are envisioned as successors of generation III reactors. The Generation IV International Forum (GIF) – an international organization that coordinates the development of generation IV reactors – specifically selected six reactor technologies as candidates for generation IV reactors. The designs target improved safety, sustainability, efficiency, and cost. The first commercial Gen IV plants are not expected before 2040–2050, although the World Nuclear Association in 2015 suggested that some might enter commercial operation before 2030.
A high-temperature gas-cooled reactor (HTGR) is a type of gas-cooled nuclear reactor which use uranium fuel and graphite moderation to produce very high reactor core output temperatures. All existing HTGR reactors use helium coolant. The reactor core can be either a "prismatic block" or a "pebble-bed" core. China Huaneng Group currently operates HTR-PM, a 250 MW HTGR power plant in Shandong province, China.
The gas-cooled fast reactor (GFR) system is a nuclear reactor design which is currently in development. Classed as a Generation IV reactor, it features a fast-neutron spectrum and closed fuel cycle for efficient conversion of fertile uranium and management of actinides. The reference reactor design is a helium-cooled system operating with an outlet temperature of 850 °C using a direct Brayton closed-cycle gas turbine for high thermal efficiency. Several fuel forms are being considered for their potential to operate at very high temperatures and to ensure an excellent retention of fission products: composite ceramic fuel, advanced fuel particles, or ceramic clad elements of actinide compounds. Core configurations are being considered based on pin- or plate-based fuel assemblies or prismatic blocks, which allows for better coolant circulation than traditional fuel assemblies.
The THTR-300 was a thorium cycle high-temperature nuclear reactor rated at 300 MW electric (THTR-300) in Hamm-Uentrop, Germany. It started operating in 1983, synchronized with the grid in 1985, operated at full power in February 1987 and was shut down September 1, 1989. The THTR-300 served as a prototype high-temperature reactor (HTR) to use the TRISO pebble fuel produced by the AVR, an experimental pebble bed operated by VEW. The THTR-300 cost €2.05 billion and was predicted to cost an additional €425 million through December 2009 in decommissioning and other associated costs. The German state of North Rhine Westphalia, Federal Republic of Germany, and Hochtemperatur-Kernkraftwerk GmbH (HKG) financed the THTR-300’s construction.
The Gas Turbine Modular Helium Reactor (GT-MHR) is a class of nuclear fission power reactor designed that was under development by a group of Russian enterprises, an American group headed by General Atomics, French Framatome and Japanese Fuji Electric. It is a helium cooled, graphite moderated reactor and uses TRISO fuel compacts in a prismatic core design. The power is generated via a gas turbine rather than via the more common steam turbine.
The Institute of Nuclear and New Energy Technology is an energy research institute located in Tsinghua University, Beijing, China. The current Institute director is Zhang Zuoyi (张作义).
A graphite-moderated reactor is a nuclear reactor that uses carbon as a neutron moderator, which allows natural uranium to be used as nuclear fuel.
Dragon was an experimental high temperature gas-cooled reactor at Winfrith in Dorset, England, operated by the United Kingdom Atomic Energy Authority. Its purpose was to test fuel and materials for the European High Temperature Reactor programme, and it was built and managed as an Organisation for Economic Co-operation and Development/Nuclear Energy Agency international project. It operated from 1965 to 1976. The site extended to 129.4 hectares of heathland in rural south Dorset, and nine different experimental reactors were located there.
The AVR reactor was a prototype pebble-bed reactor, located immediately adjacent to Jülich Research Centre in West Germany, constructed in 1960, grid connected in 1967 and shut down in 1988. It was a 15 MWe, 46 MWt test reactor used to develop and test a variety of fuels and machinery.
A gas-cooled reactor (GCR) is a nuclear reactor that uses graphite as a neutron moderator and a gas as coolant. Although there are many other types of reactor cooled by gas, the terms GCR and to a lesser extent gas cooled reactor are particularly used to refer to this type of reactor.
The HTR-PM is a small modular nuclear reactor in China. It is the world’s first demonstrator of a high-temperature gas-cooled (HTGR) pebble-bed generation IV reactor based on the HTR-10. The reactor unit has a thermal capacity of 250 MW, and two reactors are connected to a single steam turbine to generate 210 MW of electricity. Its role is to replace coal-fired power plants in China's interior, in line with the country's plan to reach carbon neutrality by 2060.
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.
X-energy is an American private nuclear reactor and fuel design engineering company. It is developing a Generation IV high-temperature gas-cooled pebble-bed nuclear reactor design. Since its founding in 2009, it has received various government grants and contracts, notably through the Department of Energy's (DOE) Advanced Reactor Concept Cooperative Agreement in 2016 and its Advanced Reactor Demonstration Program (ARDP) in 2020.
