A nuclear reactor is a device used to initiate and control a fission nuclear chain reaction. Nuclear reactors are used at nuclear power plants for electricity generation and in nuclear marine propulsion. When a fissile nucleus like 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. The process is carefully controlled using control rods and neutron moderators to regulate the number of neutrons that continue the reaction, ensuring the reactor operates safely, although inherent control by means of delayed neutrons also plays an important role in reactor output control. The efficiency of nuclear fuel is much higher than fossil fuels; the 5% enriched uranium used in the newest reactors has an energy density 120,000 times higher than coal.
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.
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.
Rudolf Schulten was a German physicist who was professor at RWTH Aachen University and 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.
A molten-salt reactor (MSR) is a class of nuclear fission reactor in which the primary nuclear reactor coolant and/or the fuel is a mixture of molten salt with a fissile material.
Nuclear fuel refers to any substance, typically fissile material, which is used by nuclear power stations or other nuclear devices to generate energy.
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 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 uses 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 (1,560 °F) 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.
Dragon was an experimental high temperature gas-cooled reactor at Winfrith in Dorset, England, operated by the United Kingdom Atomic Energy Authority (UKAEA). Its purpose was to test fuel and materials for the European High Temperature Reactor programme, which was exploring the use of tristructural-isotropic (TRISO) fuel and gas cooling for future high-efficiency reactor designs. The project was built and managed as an Organisation for Economic Co-operation and Development/Nuclear Energy Agency international project. In total, 13 countries were involved in its design and operation during the project lifetime.
The High-Temperature Teaching & Test Reactor (HT3R or HT3R) is a multifaceted energy research facility proposed by the University of Texas of the Permian Basin (UTPB) and the Los Alamos National Laboratory (LANL), to be located in Andrews County, Texas. The proposal envisions a 25MWt (Megawatt thermal) reactor operated by a merchant nuclear power operating company with the education and science at the facility managed through an arrangement between LANL and UTPB/UTS (University of Texas System).
HTR-10 is a 10 MWt prototype high-temperature gas-cooled, pebble-bed reactor at Tsinghua University in China. Construction began in 1995, achieving its first criticality in December 2000, and was operated in full power condition in January 2003.
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.
A Next Generation Nuclear Plant (NGNP) is a specific proposed generation IV very-high-temperature reactor (VHTR) that could be coupled to a neighboring hydrogen production facility. It could also produce electricity and supply process heat. Up to 30% of this heat could be used to produce hydrogen via high-temperature electrolysis significantly reducing the cost of the process. The envisioned reactor design is helium-cooled, using graphite-moderated thermal neutrons, and TRISO fueled.
TerraPower is an American nuclear reactor design and development engineering company headquartered in Bellevue, Washington. TerraPower is developing a class of nuclear fast reactors termed traveling wave reactors (TWR).
The HTR-PM is a Chinese small modular nuclear reactor. It is a high-temperature gas-cooled (HTGR) pebble-bed generation IV reactor evolved from the HTR-10 prototype. The technology is intended to replace coal-fired power plants in China's interior, in line with the country's plan to reach carbon neutrality by 2060.
Project Pele is a project of the US Department of Defense to build a deployable nuclear power reactor for use in United States Armed Forces remote operating bases.
