• light water g
  • It occurred on 25-26 April 1986 in the No.4 light water graphite moderated reactor at the Chernobyl Nuclear Power Plant near Pripyat, a town in northern Ukrainian Soviet Socialist Republic which was part of the Soviet Union (USSR), approximately 104 km north of Kiev. (wikipedia.org)
  • vessel
  • While some LMRs are of the loop type, equipped with heat exchanger s and pumps outside the primary reactor vessel, others are of the pool variety, featuring a large volume of primary sodium in a pool that also contains the primary pumps and the primary-to-secondary heat exchanger. (britannica.com)
  • A reactor of this kind consists of a tank, or calandria vessel, containing a cold heavy water moderator at atmospheric pressure . (britannica.com)
  • Water coolant travels around the primarily circuit, through the reactor pressure vessel (where it is heated by the nuclear fuel elements) and on through the tubes in a stream generator. (nationalarchives.gov.uk)
  • The submarines reactor is shut down when the vessel is in harbour. (nationalarchives.gov.uk)
  • The second spike led to a reactor vessel rupture and a series of steam explosions. (wikipedia.org)
  • The pebbles are held in a vessel, and an inert gas (such as helium, nitrogen or carbon dioxide) circulates through the spaces between the fuel pebbles to carry heat away from the reactor. (wikipedia.org)
  • In conventional light-water reactor (LWR) designs, the entire fissile core is placed in a large pressure vessel. (wikipedia.org)
  • In most plants, ECCS is composed of the following systems: HPCI consists of a pump or pumps that have sufficient pressure to inject coolant into the reactor vessel while it is pressurized. (wikipedia.org)
  • It is designed to monitor the level of coolant in the reactor vessel and automatically inject coolant when the level drops below a threshold. (wikipedia.org)
  • This system is normally the first line of defense for a reactor since it can be used while the reactor vessel is still highly pressurized. (wikipedia.org)
  • The actuation of these valves depressurizes the reactor vessel and allows lower pressure coolant injection systems to function, which have very large capacities in comparison to high pressure systems. (wikipedia.org)
  • LPCI consists of a pump or pumps that inject coolant into the reactor vessel once it has been depressurized. (wikipedia.org)
  • No one can say for sure, but some experts say that had the accident continued for another 20 to 45 minutes, the [reactor] vessel would have heated up and the metal would have lost its strength, leading to a rupture," preventing further cooling and allowing superheated fuel to melt through the reactor vessel and enter - and likely exit - the reactor building. (whyfiles.org)
  • The Reactor Protection System (RPS) is a system, computerized in later BWR models, that is designed to automatically, rapidly, and completely shut down and make safe the Nuclear Steam Supply System (NSSS - the reactor pressure vessel, pumps, and water/steam piping within the containment) if some event occurs that could result in the reactor entering an unsafe operating condition. (wikipedia.org)
  • 1960s
  • Sodium -cooled fast-neutron-spectrum liquid-metal reactors (LMRs) received much attention during the 1960s and '70s when it appeared that their breeding capabilities would soon be needed to supply fissile material to a rapidly expanding nuclear industry. (britannica.com)
  • The LFTR concept was first investigated at the Oak Ridge National Laboratory Molten-Salt Reactor Experiment in the 1960s, though the MSRE did not use thorium. (wikipedia.org)
  • The concept was first suggested by Farrington Daniels in the 1940s, said to have been inspired by the innovative design of the benghazi burner by British desert troops in WWII, but commercial development did not take place until the 1960s in the German AVR reactor by Rudolf Schulten. (wikipedia.org)
  • turbine
  • The invention relates to a method for regulating the power supplied to a steam turbine by a pressurized water nuclear reactor driving an electrical generator supplying a network. (google.com)
  • The steam is used as a driving fluid for the turbine which actuates the electric current generator. (google.com)
  • The electric power demanded by the network can be variable in the course of time, so that the power that the nuclear reactor must supply to the turbine may itself be essentially variable in the course of time. (google.com)
  • However, in the case of considerable and rapid power variations to respond to the demand of the network, or in the case of electrical disconnection between the power station and the network, this operation being called load-rejection, it is necessary to have an additional regulating means for the power supplied by the steam turbine nuclear reactor. (google.com)
  • In all types the heat extracted from the core by primary sodium is transferred to a secondary, nonradioactive sodium loop, which serves as the heat source for a steam generator that heats the water in a tertiary loop to power a turbine. (britannica.com)
  • The light-water steam exiting the steam generator in the secondary loop is then transported through a conventional turbine cycle. (britannica.com)
  • The turbine, in turn, powers a generator that produces electrical energy. (encyclopedia.com)
  • Boiling water reactors (BWR) do not use steam generators, as turbine steam is produced directly in the reactor core. (wikipedia.org)
  • Activation of oxygen and dissolved nitrogen in the water means that the turbine hall is inaccessible during reactor operation and for some time afterwards. (wikipedia.org)
  • A power house houses the turbine and the generator. (hubpages.com)
  • The turbine rotates the turbine shaft which in turn rotates the generator shaft, which is coupled to the turbine shaft. (hubpages.com)
  • Thus the turbine converts hydraulic energy into mechanical energy and the generator converts mechanical energy into electrical energy. (hubpages.com)
  • citation needed] In a nuclear power station, the pressurized steam is fed through a steam turbine which drives an electrical generator connected to the electric grid for transmission. (wikipedia.org)
  • The condenser converts the steam to a liquid so that it can be pumped back into the steam generator, and maintains a vacuum at the turbine outlet so that the pressure drop across the turbine, and hence the energy extracted from the steam, is maximized. (wikipedia.org)
  • A heat exchanger, also known as a steam generator, transfers the heat to a secondary cooling loop, which powers a steam turbine with an electric generator attached to it (for a typical Rankine thermodynamic cycle). (wikipedia.org)
  • The pressure of the expanding steam turns a turbine that is connected to a generator. (georgiapower.com)
  • Other than the heat source, a nuclear energy facility operates like any fossil fuel plant: 1) heat is created to boil water 2) to create steam 3) to turn the turbine 4) which spins the generator. (georgiapower.com)
  • The steam is used to drive a turbine connected to an electrical generator. (blogspot.com)
  • rods
  • When the hafnium rods are inserted into the ceramic-based fuel cells, they absorb neutrons so as to stop fisson. (peachpundit.com)
  • It is known that the operation of nuclear reactors to follow a given power program uses neutron-absorbant rods which are moved in the core of the reactor according to the power demand program. (google.com)
  • During a disaster, when a power outage happens and diesel power generators which provide emergency power to the water pump are damaged by a tsunami or an earthquake, if no fresh water is being pumped to cool the fuel rods then the fuel rods continue to heat up. (wikipedia.org)
  • The enriched fuel is used in the reactors in the form of rods. (hubpages.com)
  • 2. Rods of cadmium are lowered into a reactor to control the reaction. (blogspot.com)
  • The rods regulate the nuclear divisions by absorbing a number of freed neutrons. (blogspot.com)
  • Fukushima Daiichi
  • As Japan confronted what Emperor Akihito called the worst crisis since World War II, we began to hear that the six-reactor complex at the Fukushima Daiichi plant, located directly in the tsunami's path, had lost electrical power. (whyfiles.org)
  • nuclear power
  • Coal has a trace amount of radioactive carbon (C14, usually absorbed from the environment the coal came from) that generates more measurable radiation than you can detect outside a nuclear power plant. (peachpundit.com)
  • Schematic diagram of a nuclear power plant using a pool-type sodium-cooled liquid-metal reactor. (britannica.com)
  • Any material used in a nuclear power plant to transfer the heat produced in the reactor core to another unit in which electricity is generated. (encyclopedia.com)
  • The first purely commercial nuclear power plant at Shippingport Atomic Power Station was originally designed as a pressurized water reactor (although the first power plant connected to the grid was at Calder Hall, UK), on insistence from Admiral Hyman G. Rickover that a viable commercial plant would include none of the "crazy thermodynamic cycles that everyone else wants to build. (wikipedia.org)
  • fuel
  • A cold fuel flows over some parts of the engine, absorbing its waste heat and being preheated before combustion. (wikipedia.org)
  • The reactor core in all such systems is a tightly packed bundle of fuel in steel cladding through which the sodium coolant flows to extract the heat. (britannica.com)
  • Canada has focused its developmental efforts on reactors that utilize abundant domestic natural uranium as fuel without having to resort to enrichment services that would be supplied only by other countries. (britannica.com)
  • The Calder Hall reactor design was fueled with slugs of natural uranium metal canned in aluminum , was cooled with carbon dioxide , and employed a moderator consisting of a block of graphite pierced by fuel channels. (britannica.com)
  • This plutonium isotope can be reprocessed and used as more reactor fuel or in the production of nuclear weapons. (scientificamerican.com)
  • Reactors can be designed to maximize plutonium production, and in some cases they actually produce more fuel than they consume. (scientificamerican.com)
  • Commercial nuclear reactors normally use uranium fuel that has had its U 235 content enriched to somewhere between 3 and 8 percent by weight. (scientificamerican.com)
  • Although the U 235 does most of the fissioning, more than 90 percent of the atoms in the fuel are U 238 --potential neutron capture targets and future plutonium atoms. (scientificamerican.com)
  • Creating extra fuel in nuclear reactors, however, is not without its concerns: One is that the plutonium produced can be removed and used in nuclear weapons. (scientificamerican.com)
  • For these reasons, in the U.S., President Carter halted such spent fuel reprocessing, making the use of breeder reactors problematic. (scientificamerican.com)
  • A material that covers the fuel elements in a nuclear reactor in order to prevent the loss of heat and radioactive materials from the fuel. (encyclopedia.com)
  • For example, all of the fuel in a reactor is sealed in a protective coating made of a zirconium alloy. (encyclopedia.com)
  • In the Molten-Salt Reactor Experiment it even served as a solvent carrying the nuclear fuel. (wikipedia.org)
  • The remaining neutron energy is dissipated in a lithium blanket, located within the con centric vessels, where the fuel ingredient, tritium, is also produced. (google.es)
  • Molten-salt-fueled reactors (MSRs) supply the nuclear fuel mixed into a molten salt. (wikipedia.org)
  • They should not be confused with designs that use a molten salt for cooling only (fluoride high-temperature reactors, FHRs) and still have a solid fuel. (wikipedia.org)
  • U-235 is the world's primary nuclear fuel and is usually used in light water reactors. (wikipedia.org)
  • Both test reactors used liquid fluoride fuel salts. (wikipedia.org)
  • In a nuclear power reactor, there are two types of fuel. (wikipedia.org)
  • Often the amount of fertile fuel in the reactor is far greater than the amount of fissile, but it cannot be fissioned directly. (wikipedia.org)
  • All reactors breed some fuel this way, but today's solid fueled thermal reactors don't breed enough new fuel from the fertile to make up for the amount of fissile they consume. (wikipedia.org)
  • Such a fuel cycle, using slowed down neutrons, gives back less than 2 new neutrons from fissioning the bred plutonium. (wikipedia.org)
  • The basic design of pebble-bed reactors features spherical fuel elements called pebbles. (wikipedia.org)
  • The pebble design is relatively simple, with each sphere consisting of the nuclear fuel, fission product barrier, and moderator (which in a traditional water reactor would all be different parts). (wikipedia.org)
  • The basic fuel for a nuclear power reactor is uranium - a heavy metal able to release abundant concentrated energy. (blogspot.com)
  • Today the only substantial use for uranium is as fuel in nuclear reactors, mostly for electricity generation. (blogspot.com)
  • These recovery operations produce a product called ' yellowcake ' that is transformed into fuel for nuclear power reactors. (georgiapower.com)
  • The fuel for nuclear reactors has to have a higher concentration of U235 than exists in natural uranium ore. (georgiapower.com)
  • While radioactive water at the unit most likely escaped from the reactor core, it also could have originated from spent fuel pools stored atop the reactor, he said. (abovetopsecret.com)
  • The emergency generators also failed, apparently due to water damage to them or their fuel supply. (whyfiles.org)
  • and significant damage to the fuel and potentially reactor equipment can occur within minutes. (whyfiles.org)
  • As hundreds of alarms buzzed in the control room, operators, lacking a direct measurement of the water level inside the reactor, made a bad situation worse, the reactor went at least partly dry, and a large percentage of the fuel melted. (whyfiles.org)
  • The slow, dangerous removal of fuel revealed massive heating and damage inside the reactor. (whyfiles.org)
  • From there, it's impossible to speculate how widely the radiation would have spread, the authors wrote, but this is what is called the China Syndrome - a runaway load of reactor fuel melting its way down into the earth. (whyfiles.org)
  • Because of this effect in BWRs, operating components and safety systems are designed with the intention that no credible scenario can cause a pressure and power increase that exceeds the systems' capability to quickly shut down the reactor before damage to the fuel or to components containing the reactor coolant can occur. (wikipedia.org)
  • Only if the fuel has been exposed for a few days in the reactor, can the Pu-239 be chemically separated from the rest of the material to yield high-purity Pu-239 metal. (wikipedia.org)
  • it emits neutron radiation, making handling more difficult, and its presence can lead to a "fizzle" in which a small explosion occurs, destroying the weapon but not causing fission of a significant fraction of the fuel. (wikipedia.org)
  • Plutonium is classified according to the percentage of the contaminant plutonium-240 that it contains: Supergrade 2-3% Weapons grade less than 7% Fuel grade 7-18% Reactor grade 18% or more A nuclear reactor that is used to produce plutonium for weapons therefore generally has a means for exposing U-238 to neutron radiation and for frequently replacing the irradiated U-238 with new U-238. (wikipedia.org)
  • However, most commercial nuclear power reactor designs require the entire reactor to shut down, often for weeks, in order to change the fuel elements. (wikipedia.org)
  • Boiling
  • Light water reactors, both boiling water and pressurised water reactors the most common type, use ordinary (light) water. (wikipedia.org)
  • Not to nitpick, but Chernobyl wasn't a sodium reactor, it was a graphite moderated, boiling light water cooled reactor. (peachpundit.com)
  • The coolant (treated water), which is maintained at high pressure to prevent boiling, is pumped through the nuclear reactor core. (wikipedia.org)
  • for example the boiling water reactor. (wikipedia.org)
  • Play media Pressurized water reactors (PWRs) constitute the large majority of the world's nuclear power plants (notable exceptions being the United Kingdom, Japan, the United States and Canada) and are one of three types of light water reactor (LWR), the other types being boiling water reactors (BWRs) and supercritical water reactors (SCWRs). (wikipedia.org)
  • A boiling water reactor, by contrast, has only one coolant loop, while more exotic designs such as breeder reactors use substances other than water for coolant and moderator (e.g. sodium in its liquid state as coolant or graphite as a moderator). (wikipedia.org)
  • Boiling water reactor safety systems are nuclear safety systems constructed within boiling water reactors in order to prevent or mitigate environmental and health hazards in the event of accident or natural disaster. (wikipedia.org)
  • Also like the pressurized water reactor, a boiling water reactor has a negative void coefficient, that is, the neutron (and the thermal) output of the reactor decreases as the proportion of steam to liquid water increases inside the reactor. (wikipedia.org)
  • power
  • Hydrogen-cooled turbogenerators are currently the most common electrical generators in large power plants. (wikipedia.org)
  • Future reactor designs will use neither of these methods, and many of them will enable the use of off the shelf natural occurring Uranium and Thorium, which will push the viability of nuclear power from 100's to millions or billions of years. (peachpundit.com)
  • American nuclear power plants have several levels of containment that the Soviet reactor didn't have. (peachpundit.com)
  • In pressurized water nuclear power stations used for the generation of electric current, steam is produced by heat exchange between the primary fluid constituted by water under pressure and the secondary fluid constituted by water which is converted into steam inside the steam generators. (google.com)
  • On the other hand, it is sometimes necessary to disconnect the current generator from the network for a longer or shorter time for a reason independent of the operation of the nuclear power station itself. (google.com)
  • Electric-power generation is obtained through the transfer of the heat of fission into the heavy-water coolant, which is circulated to a steam generator. (britannica.com)
  • Capacity factor refers to the ratio of time that a reactor is operating at full power during a given period versus the total available time during that same period. (britannica.com)
  • Thus, a capacity factor of 1.0 refers to a reactor that operates at full power 24 hours a day over the entire period of time being considered. (britannica.com)
  • The advanced gas-cooled reactor (AGR) was developed in the United Kingdom as the successor to reactors of the Calder Hall class, which combined plutonium production and power generation. (britannica.com)
  • After an initial agreement between Ronald Reagan and Mikhail Gorbachev in November 1985, the ITER reactor effort developed, and remains the primary international effort to develop practical fusion power. (wikipedia.org)
  • Before the reactor is shut down, electricity from the shore is required to power the submarine's mechanical and electrical systems such as pumps and back up systems. (nationalarchives.gov.uk)
  • During fission, a small amount of mass is converted into energy, which can be used to power a generator to create electricity. (scientificamerican.com)
  • The U.S. constructed two experimental breeder reactors, neither of which produced power commercially. (scientificamerican.com)
  • Every such plant contains four fundamental elements: the reactor, the coolant system, the electrical power generating unit, and the safety system. (encyclopedia.com)
  • The nuclear powered steam generator started as a power plant for the first nuclear submarine, the USS Nautilus (SSN-571). (wikipedia.org)
  • It was designed and built by the Westinghouse power company for the submarine from there the company started its development and research of nuclear powered steam generators. (wikipedia.org)
  • Once peaceful nuclear reactors were legalized for use as power plants, power corporations jumped at the opportunity to utilize the growing development of nuclear powered steam generators. (wikipedia.org)
  • Westinghouse built one of the first nuclear power plants, the Yankee Rowe nuclear power station (NPS), which also used a nuclear powered steam generator, in 1960. (wikipedia.org)
  • Eventually, other international companies such as Babcock & Wilcox and Combustion Engineering began their own programs for research and development of the nuclear power steam generator. (wikipedia.org)
  • the enclosure was not intended as a radiation shield, but was built quickly as occupational safety for the crews of the other undamaged reactors at the power station, with No.3 continuing to produce electricity into 2000. (wikipedia.org)
  • The accident motivated safety upgrades on all remaining Soviet-designed reactors in the RBMK (Chernobyl No.4) family, of which eleven continued to power electric grids as of 2013. (wikipedia.org)
  • Nuclear reactors are used at nuclear power plants for electricity generation and in propulsion of ships. (wikipedia.org)
  • As of April 2014, the IAEA reports there are 435 nuclear power reactors in operation, in 31 countries around the world. (wikipedia.org)
  • Just as conventional power-stations generate electricity by harnessing the thermal energy released from burning fossil fuels, nuclear reactors convert the energy released by controlled nuclear fission into thermal energy for further conversion to mechanical or electrical forms. (wikipedia.org)
  • Nuclear reactors typically employ several methods of neutron control to adjust the reactor's power output. (wikipedia.org)
  • The United States Army Nuclear Power Program operated pressurized water reactors from 1954 to 1974. (wikipedia.org)
  • The energy lost by the neutrons heats the moderator and is extracted for power. (wikipedia.org)
  • PWRs also use boric acid to make fine adjustments to reactor power level, or reactivity, using their Chemical and Volume Control System (CVCS). (wikipedia.org)
  • It is also used as a thermal power source in radioisotope thermoelectric generator power packs. (wikipedia.org)
  • Thorium reactors can generate power from the plutonium residue left by uranium reactors. (wikipedia.org)
  • The fission process stops when the proton beam stops, as when power is lost, thus the reactor is subcritical. (wikipedia.org)
  • The increased ratio of water to steam will lead to increased neutron moderation, which in turn will cause an increase in the power output of the reactor. (wikipedia.org)
  • In the limiting case of an ATWS (Anticipated Transient Without Scram) derangement, high neutron power levels (~ 200%) can occur for less than a second, after which actuation of SRVs will cause the pressure to rapidly drop off. (wikipedia.org)
  • Solar electric, due to the low amount of energy per square foot of generator, fairly demands decentralization: rooftops are about the only environmentally neutral surface area available in sufficient quantity to power most cities. (earthisland.org)
  • A few commercial power reactor designs, such as the reaktor bolshoy moshchnosti kanalniy (RBMK) and pressurized heavy water reactor (PHWR), do permit refueling without shutdowns, and they may pose a proliferation risk. (wikipedia.org)
  • radiation
  • The entire process takes place inside a heavy shielded reactor compartment that completely protects the crew from radiation. (nationalarchives.gov.uk)
  • Acute neutron radiation exposure (e.g., from a nuclear criticality accident) converts some of the stable 23 Na in human blood plasma to 24 Na. (wikipedia.org)
  • Measurements of its quantity are used to determine the absorbed radiation dose of the patient. (wikipedia.org)
  • The nuclear reactor is enclosed in a thick, massive, concrete, shield so as to protect the surrounding from radiation. (hubpages.com)
  • From an energy point of view the gamma-ray energy should not be so low that the radiation gets completely absorbed before emerging from the patient's body and not too high that it is difficult to detect. (wikibooks.org)
  • The term 'biological shield' is used for absorbing material placed around a nuclear reactor, or other source of radiation, to reduce the radiation to a level safe for humans. (wikipedia.org)
  • steam generator
  • each steam generator can measure up to 70 feet (21 m) in height and weigh as much as 800 tons. (wikipedia.org)
  • Each steam generator can contain anywhere from 3,000 to 16,000 tubes, each about .75 inches (19 mm) in diameter. (wikipedia.org)
  • That water flowing through the steam generator boils water on the shell side (which is kept at a lower pressure than the primary side) to produce steam. (wikipedia.org)
  • The steam is subsequently condensed via cooled water from a tertiary loop and returned to the steam generator to be heated once again. (wikipedia.org)
  • Steam generator tubes often degrade over time. (wikipedia.org)
  • Thus during scheduled maintenance outages or shutdowns, some or all of the steam generator tubes are inspected by eddy-current testing, and individual tubes can be plugged to remove them from operation. (wikipedia.org)
  • Without that pump, the steam generator wasn't able to remove heat from the reactor, so pressure in the reactor began to rise. (wikipedia.org)
  • The heated water then flows to a steam generator where it transfers its thermal energy to a secondary system where steam is generated and flows to turbines which, in turn, spin an electric generator. (wikipedia.org)
  • Some common steam generator arrangements are u-tubes or single pass heat exchangers. (wikipedia.org)
  • Before being fed into the steam generator, the condensed steam (referred to as feedwater) is sometimes preheated in order to minimize thermal shock. (wikipedia.org)
  • The exhaust steam from the turbines is then cooled, condensed and returned as feedwater to the steam generator. (wikipedia.org)
  • shut
  • This decay heat-source will remain for some time even after the reactor is shut down. (wikipedia.org)
  • 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. (wikipedia.org)
  • In addition, the reactor will already have rapidly shut down before the transient affects the RPV (as described in the Reactor Protection System section below. (wikipedia.org)
  • graphite
  • These events exposed the graphite moderator of the reactor to air, causing it to ignite. (wikipedia.org)
  • The pebble-bed reactor (PBR) is a design for a graphite-moderated, gas-cooled nuclear reactor. (wikipedia.org)
  • The uranium, thorium or plutonium nuclear fuels are in the form of a ceramic (usually oxides or carbides) contained within spherical pebbles a little smaller than the size of a tennis ball and made of pyrolytic graphite, which acts as the primary neutron moderator. (wikipedia.org)
  • Pebble-bed reactors need fire-prevention features to keep the graphite of the pebbles from burning in the presence of air if the reactor wall is breached, although the flammability of the pebbles is disputed. (wikipedia.org)