1.
Light-water reactor
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Thermal-neutron reactors are the most common type of nuclear reactor, and light-water reactors are the most common type of thermal-neutron reactor. There are three varieties of light-water reactors, the water reactor, the boiling water reactor. It is however the first aqueous homogeneous reactor and the first reactor using enriched uranium as fuel, the purpose of this experience was to determine the feasibility of a nuclear reactor using light water as a moderator and coolant, and cladded solid uranium as fuel. The results showed that, with an enriched uranium, criticality could be reached. This experience was the first practical step toward light-water reactor, after World War II and with the availability of enriched uranium, new concepts of reactor became feasible. In 1946, Eugene Wigner and Alvin Weinberg proposed and developed the concept of a reactor using enriched uranium as a fuel and this concept was proposed for a reactor whose purpose was to test the behavior of materials under neutron flux. This reactor, the Material Testing Reactor, was built in Idaho at INL and this MTR mock-up, later called the Low Intensity Test Reactor, reached criticality on February 4,1950 and was the worlds first light-water reactor. Immediately after the end of World War II the United States Navy started a program under the direction of Captain Hyman Rickover and it developed the first pressurized water reactors in the early 1950s, and led to the successful deployment of the first nuclear submarine, the USS Nautilus. The Soviet Union independently developed a version of the PWR in the late 1950s, while functionally very similar to the American effort, it also has certain design distinctions from Western PWRs. Researcher Samuel Untermyer II led the effort to develop the BWR at the US National Reactor Testing Station in a series of tests called the BORAX experiments, LWRs can be subdivided into three categories – pressurized water reactors, boiling water reactors, and supercritical water reactors. West Germany was also once a player with BWRs. In addition, light-water reactors make up the vast majority of reactors that power naval nuclear-powered vessels, the reason for near exclusive LWR use aboard nuclear naval vessels is the level of inherent safety built into these types of reactors. This capability is known as a negative coefficient of reactivity. The nuclear reactor core is the portion of a reactor where the nuclear reactions take place. It mainly consists of fuel and control elements. The pencil-thin nuclear fuel rods, each about 12 feet long, are grouped by the hundreds in bundles called fuel assemblies, inside each fuel rod, pellets of uranium, or more commonly uranium oxide, are stacked end to end. The control elements, called control rods, are filled with pellets of substances like hafnium or cadmium that readily capture neutrons, when the control rods are lowered into the core, they absorb neutrons, which thus cannot take part in the chain reaction. On the converse, when the rods are lifted out of the way, more neutrons strike the fissile uranium-235 or plutonium-239 nuclei in nearby fuel rods
2.
Nuclear reactor
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This article is a subarticle of Nuclear power. A nuclear reactor, formerly known as a pile, is a device used to initiate. Nuclear reactors are used at power plants for electricity generation. Heat from nuclear fission is passed to a fluid, which runs through steam turbines. These either drive a ships propellers or turn electrical generators, 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, some are run only for research. As of April 2014, the IAEA reports there are 435 nuclear power reactors in operation, when a large fissile atomic nucleus such as uranium-235 or plutonium-239 absorbs a neutron, it may undergo nuclear fission. The heavy nucleus splits into two or more nuclei, releasing kinetic energy, gamma radiation, and free neutrons. A portion of neutrons may later be absorbed by other fissile atoms and trigger further fission events, which release more neutrons. This is known as a chain reaction. To control such a chain reaction, neutron poisons and neutron moderators can change the portion of neutrons that will go on to cause more fission. Nuclear reactors generally have automatic and manual systems to shut the fission reaction down if monitoring detects unsafe conditions, commonly-used moderators include regular water, solid graphite and heavy water. Some experimental types of reactor have used beryllium, and hydrocarbons have been suggested as another possibility, the reactor core generates heat in a number of ways, The kinetic energy of fission products is converted to thermal energy when these nuclei collide with nearby atoms. The reactor absorbs some of the rays produced during fission. Heat is produced by the decay of fission products and materials that have been activated by neutron absorption. This decay heat-source will remain for some even after the reactor is shut down. A kilogram of uranium-235 converted via nuclear processes releases approximately three times more energy than a kilogram of coal burned conventionally. A nuclear reactor coolant — usually water but sometimes a gas or a metal or molten salt — is circulated past the reactor core to absorb the heat that it generates
3.
Pressurized water reactor
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In a PWR, the primary coolant is pumped under high pressure to the reactor core where it is heated by the energy released by the fission of atoms. The heated water 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. In contrast to a boiling water reactor, pressure in the coolant loop prevents the water from boiling within the reactor. All LWRs use ordinary water as coolant and neutron moderator. PWRs currently operating in the United States are considered Generation II reactors, russias VVER reactors are similar to U. S. PWRs. France operates many PWRs to generate the bulk of its electricity, several hundred PWRs are used for marine propulsion in aircraft carriers, nuclear submarines and ice breakers. In the US, they were designed at the Oak Ridge National Laboratory for use as a nuclear submarine power plant. Follow-on work was conducted by Westinghouse Bettis Atomic Power Laboratory, the United States Army Nuclear Power Program operated pressurized water reactors from 1954 to 1974. Three Mile Island Nuclear Generating Station initially operated two pressurized water reactor plants, TMI-1 and TMI-2, the partial meltdown of TMI-2 in 1979 essentially ended the growth in new construction of nuclear power plants in the United States for two decades. The hot primary coolant is pumped into a heat exchanger called the steam generator, heat is transferred through the walls of these tubes to the lower pressure secondary coolant located on the sheet side of the exchanger where the coolant evaporates to pressurized steam. The transfer of heat is accomplished without mixing the two fluids to prevent the secondary coolant from becoming radioactive, some common steam generator arrangements are u-tubes or single pass heat exchangers. In a nuclear power station, the steam is fed through a steam turbine which drives an electrical generator connected to the electric grid for transmission. After passing through the turbine the secondary coolant is cooled down, before being fed into the steam generator, the condensed steam is sometimes preheated in order to minimize thermal shock. The steam generated has other uses besides power generation, in nuclear ships and submarines, the steam is fed through a steam turbine connected to a set of speed reduction gears to a shaft used for propulsion. Direct mechanical action by expansion of the steam can be used for a aircraft catapult or similar applications. District heating by the steam is used in countries and direct heating is applied to internal plant applications. Two things are characteristic for the water reactor when compared with other reactor types, coolant loop separation from the steam system. In a PWR, there are two separate coolant loops, which are filled with demineralized/deionized water
4.
Nuclear reactor core
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A nuclear reactor core is the portion of a nuclear reactor containing the nuclear fuel components where the nuclear reactions take place and the heat is generated. Typically, the fuel will be low-enriched uranium contained in thousands of individual fuel pins, inside each fuel rod, pellets of uranium, or more commonly uranium oxide, are stacked end to end. Also inside the core are control rods, filled with pellets of substances like boron or hafnium or cadmium that readily capture neutrons, when the control rods are lowered into the core, they absorb neutrons, which thus cannot take part in the chain reaction. Conversely, when the rods are lifted out of the way, more neutrons strike the fissile uranium-235 or plutonium-239 nuclei in nearby fuel rods. The core shroud, also located inside of the reactor, directs the flow to cool the nuclear reactions inside of the core. The heat of the reaction is removed by the water. An alternative form of fuel would be fissile uranium-233 made by the neutron-bombardment of the common thorium-232. There are also Graphite moderated reactors in use, one type uses solid graphite for the neutron moderator and ordinary water for the coolant. See the Soviet-made RBMK nuclear-power reactor and this was the type of reactor involved in the Chernobyl disaster. In the advanced gas-cooled reactor, a British design, the core is made of a neutron moderator where the fuel assemblies are located. Carbon dioxide gas acts as a coolant and it circulates through the core, there have also been several experimental reactors that use graphite for moderation, such as the pebble bed reactor concepts and the molten-salt reactor experiment. Nuclear meltdown Lists of nuclear disasters and radioactive incidents Nuclear power Nuclear reactor technology Nuclear Reactor Analysis, John Wiley & Sons Canada, Ltd
5.
Idaho National Laboratory
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Idaho National Laboratory is an 890-square-mile complex located in the high desert of eastern Idaho, between the town of Arco to the west and the cities of Idaho Falls and Blackfoot to the east. It lies within Butte, Bingham, Bonneville, and Jefferson counties, the lab currently employs approximately 4,000 people. The federal research facility was established in 1949 as the National Reactor Testing Station, in 1975, the Atomic Energy Commission was divided into the Energy Research and Development Administration and the Nuclear Regulatory Commission. The Idaho site was for a time named ERDA and then subsequently renamed to the Idaho National Engineering Laboratory in 1977 with the creation of the Department of Energy under President Carter. After two decades as INEL, the name was changed again to the Idaho National Engineering and Environmental Laboratory in 1997. Throughout its lifetime, there have more than 50 one-of-a-kind nuclear reactors built by various organizations at the facility for testing, all. On Feb.1,2005, Battelle Energy Alliance took over operation of the lab from Bechtel, merged with Argonne National Laboratory-West, and the facility name was changed to Idaho National Laboratory. At this time the sites clean-up activities were moved to a contract, the Idaho Cleanup Project. Research activities were consolidated in the newly named Idaho National Laboratory, in the Snake River Plain, most of INL is desert with scrub vegetation and a number of facilities scattered throughout the area, the average elevation of the complex is 5,000 feet above sea level. A few publicly accessible highways go through the vast INL, but most of the area is restricted to authorized personnel, the tiny town of Atomic City is on the INLs southern border, and the Craters of the Moon National Monument is to the southwest. The heat generated from nuclear fission in the plant could provide process heat for hydrogen production and other industrial purposes, and the NGNP would use a high-temperature gas reactor, which would have redundant safety systems that rely on natural physical processes more than human or mechanical intervention. INL is working with industry to design, plan and eventually build the NGNP. It was commissioned to lead this effort by the U. S. Department of Energy as a result of the Energy Policy Act of 2005 and these efforts strive to make nuclear energys expansion safe, secure, economic and sustainable. One of the primary FCRD goals is to research, develop, the Program aims to safely and economically extend the service lives of the more than 100 electricity-generating nuclear power plants in the United States. The program brings together technical information, performs important research and organizes data to be used in license-extension applications, iNL’s Advanced Test Reactor is a unique research reactor located approximately 50 miles from Idaho Falls, Idaho. The Department of Energy named Advanced Test Reactor a National Scientific User Facility in April 2007 and this designation opened the facility to use by university-led scientific research groups and gives them free access to the ATR and other unique resources at INL and partner facilities. DOEs Nuclear Energy University Programs provides funding for university research grants, fellowships, scholarships, for example, in May 2010, the program awarded $38 million for 42 university-led R&D projects at 23 U. S. universities in 17 states. In FY2009, the program awarded about $44 million to 71 R&D projects, INLs Center for Advanced Energy Studies administers the program for DOE
6.
General Electric
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General Electric, often abbreviated as GE, is an American multinational conglomerate corporation incorporated in New York and headquartered in Boston, Massachusetts. In 2011, GE ranked among the Fortune 500 as the 68th-largest firm in the U. S. by gross revenue, as of 2012, the company was listed the fourth-largest in the world among the Forbes Global 2000, further metrics being taken into account. The Nobel Prize has twice been awarded to employees of General Electric, Irving Langmuir in 1932, on January 13,2016, it was announced that GE will be moving its corporate headquarters from Fairfield, Connecticut to the South Boston Waterfront neighborhood of Boston, Massachusetts. The first group of workers arrived in the summer of 2016, morgan and the Vanderbilt family for Edisons lighting experiments. The new company also acquired Sprague Electric Railway & Motor Company in the same year, both plants continue to operate under the GE banner to this day. The company was incorporated in New York, with the Schenectady plant used as headquarters for years thereafter. Around the same time, General Electrics Canadian counterpart, Canadian General Electric, was formed, in 1896, General Electric was one of the original 12 companies listed on the newly formed Dow Jones Industrial Average. After 120 years, it is the one of the original companies still listed on the Dow index. In 1911, General Electric absorbed the National Electric Lamp Association into its lighting business, GE established its lighting division headquarters at Nela Park in East Cleveland, Ohio. Nela Park is still the headquarters for GEs lighting business, owen D. Young, through GE, founded the Radio Corporation of America in 1919 to further international radio. GE used RCA as its retail arm for radio sales from 1919, in 1927, Ernst Alexanderson of GE made the first demonstration of his television broadcasts at his General Electric Realty Plot home at 1132 Adams Rd, Schenectady, NY. The sound was broadcast on GEs WGY, experimental television station W2XAD evolved into station WRGB which—along with WGY and WGFM —was owned and operated by General Electric until 1983. GEs history of working with turbines in the field gave them the engineering know-how to move into the new field of aircraft turbosuperchargers. Led by Sanford Alexander Moss, GE introduced the first superchargers during World War I, superchargers became indispensable in the years immediately prior to World War II, and GE was the world leader in exhaust-driven supercharging when the war started. This experience, in turn, made GE a natural selection to develop the Whittle W.1 jet engine that was demonstrated in the United States in 1941, GE ranked ninth among United States corporations in the value of wartime production contracts. In 2002, GE acquired the assets of Enron during its bankruptcy proceedings. Some consumers boycotted GE light bulbs, refrigerators and other products in the 1980s and 1990s to protest GEs role in weapons production. With IBM, Burroughs, NCR, Control Data Corporation, Honeywell, RCA and UNIVAC, GE had a line of general purpose and special purpose computers
7.
GE Hitachi Nuclear Energy
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GE Hitachi Nuclear Energy is a provider of advanced reactors and nuclear services. It is located in Wilmington, N. C, established in June 2007, GEH is a global nuclear alliance created by General Electric and Hitachi. In Japan, the alliance is Hitachi-GE Nuclear Energy, Ltd, in November 2015, Jay Wileman was appointed CEO. The NRC has docketed GEHs petition for renewal of ABWR certification, GEHs Power Reactor Innovative Small Modular is a Generation IV reactor that uses liquid sodium as a coolant. As nuclear plants get older and worldwide demand for energy increases, GEH offers a range of valuable services that can improve performance, increase power output. GEH’s fuel cycle business supplies reliable fuel products and services to customers around the world, GE Hitachi Nuclear Energy owns the Morris Operation--the only de facto high-level radioactive waste storage site in the United States
8.
Cooling tower
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A cooling tower is a heat rejection device that rejects waste heat to the atmosphere through the cooling of a water stream to a lower temperature. Common applications include cooling the water used in oil refineries, petrochemical and other chemical plants, thermal power stations. The classification is based on the type of air induction into the tower, although these large towers are very prominent, the vast majority of cooling towers are much smaller, including many units installed on or near buildings to discharge heat from air conditioning. Cooling towers originated in the 19th century through the development of condensers for use with the steam engine, condensers use relatively cool water, via various means, to condense the steam coming out of the cylinders or turbines. This reduces the pressure, which in turn reduces the steam consumption. However the condensers require a supply of cooling water, without which they are impractical. The consumption of cooling water by inland processing and power plants is estimated to reduce power availability for the majority of power plants by 2040–2069. While water usage is not an issue with marine engines, it forms a significant limitation for many land-based systems. In areas with land, the systems took the form of cooling ponds, in areas with limited land, such as in cities. These early towers were positioned either on the rooftops of buildings or as free-standing structures, a hyperboloid cooling tower was patented by the Dutch engineers Frederik van Iterson and Gerard Kuypers in 1918. The first hyperboloid cooling towers were built in 1918 near Heerlen, the first ones in the United Kingdom were built in 1924 at Lister Drive power station in Liverpool, England, to cool water used at a coal-fired electrical power station. An HVAC cooling tower is used to dispose of unwanted heat from a chiller, water-cooled chillers are normally more energy efficient than air-cooled chillers due to heat rejection to tower water at or near wet-bulb temperatures. Air-cooled chillers must reject heat at the higher temperature. In areas with a hot climate, large buildings, hospitals. Generally, industrial cooling towers are much larger than HVAC towers, HVAC use of a cooling tower pairs the cooling tower with a water-cooled chiller or water-cooled condenser. A ton of air-conditioning is defined as the removal of 12,000 BTU/hour, the equivalent ton on the cooling tower side actually rejects about 15,000 BTU/hour due to the additional waste heat-equivalent of the energy needed to drive the chillers compressor. This equivalent ton is defined as the rejection in cooling 3 US gallons/minute of water 10 °F. This COP is equivalent to an energy efficiency ratio of 14, Cooling towers are also used in HVAC systems that have multiple water source heat pumps that share a common piping water loop
9.
Water purification
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Water purification is the process of removing undesirable chemicals, biological contaminants, suspended solids and gases from contaminated water. The goal is to produce water fit for a specific purpose, the standards for drinking water quality are typically set by governments or by international standards. These standards usually include minimum and maximum concentrations of contaminants, depending on the purpose of water use. Visual inspection cannot determine if water is of appropriate quality, simple procedures such as boiling or the use of a household activated carbon filter are not sufficient for treating all the possible contaminants that may be present in water from an unknown source. Even natural spring water – considered safe for all purposes in the 19th century – must now be tested before determining what kind of treatment. Chemical and microbiological analysis, while expensive, are the way to obtain the information necessary for deciding on the appropriate method of purification. The WHO estimates that 94% of these cases are preventable through modifications to the environment. Simple techniques for treating water at home, such as chlorination, filters, and solar disinfection, reducing deaths from waterborne diseases is a major public health goal in developing countries. Groundwater, The water emerging from deep ground water may have fallen as rain many tens, hundreds. Such water may emerge as springs, artesian springs, or may be extracted from boreholes or wells, deep ground water is generally of very high bacteriological quality, but the water may be rich in dissolved solids, especially carbonates and sulfates of calcium and magnesium. Depending on the strata through which the water has flowed, other ions may also be present including chloride, there may be a requirement to reduce the iron or manganese content of this water to make it acceptable for drinking, cooking, and laundry use. Primary disinfection may also be required, where groundwater recharge is practised, the groundwater may require additional treatment depending on applicable state and federal regulations. Bacteria and pathogen levels are low, but some bacteria. Where uplands are forested or peaty, humic acids can colour the water, many upland sources have low pH which require adjustment. Rivers, canals and low land reservoirs, Low land surface waters will have a significant bacterial load and may also contain algae, suspended solids and a variety of dissolved constituents. Atmospheric water generation is a new technology that can provide high quality drinking water by extracting water from the air by cooling the air, desalination of seawater by distillation or reverse osmosis. Surface Water, Freshwater bodies that are open to the atmosphere and are not designated as groundwater are termed surface waters. The aims of the treatment are to remove unwanted constituents in the water, the choice of method will depend on the quality of the water being treated, the cost of the treatment process and the quality standards expected of the processed water
10.
Neutron moderator
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Commonly used moderators include regular water, solid graphite and heavy water. Beryllium has also used in some experimental types, and hydrocarbons have been suggested as another possibility. Neutrons are normally bound into a nucleus, and do not exist free for long in nature. The unbound neutron has a half-life of just about 10 minutes, the release of neutrons from the nucleus requires exceeding the binding energy of the neutron, which is typically 7-9 MeV for most isotopes. Neutron sources generate free neutrons by a variety of reactions, including nuclear fission. Whatever the source of neutrons, they are released with energies of several MeV, moderation is the process of the reduction of the initial high kinetic energy of the free neutron. Since energy is conserved, this reduction of the kinetic energy takes place by transfer of energy to a material known as a moderator. It is also known as neutron slowing down, since along with the reduction of energy comes a reduction in speed, the probability of scattering of a neutron from a nucleus is given by the scattering cross section. The first couple of collisions with the moderator may be of high energy to excite the nucleus of the moderator. Such a collision is inelastic, since some of the energy is transformed to potential energy by exciting some of the internal degrees of freedom of the nucleus to form an excited state. As the energy of the neutron is lowered, the collisions become predominantly elastic, i. e. the total kinetic energy and momentum of the system is conserved. A collision of a neutron, which has mass of 1, more generally, it is necessary to take into account both glancing and head-on collisions. The mean logarithmic reduction of energy per collision, ξ, depends only on the atomic mass, A, of the nucleus and is given by. This can be approximated to the very simple form ξ ≃2 A +1. From this one can deduce n, the number of collisions of the neutron with nuclei of a given type that is required to reduce the kinetic energy of a neutron from E0 to E1 n =1 ξ. Some nuclei have larger absorption cross sections than others, which free neutrons from the flux. Therefore, a criterion for an efficient moderator is one for which this parameter is small. The moderating efficiency gives the ratio of the cross sections of scattering, Σ s, weighted by ξ divided by that of absorption
11.
Turbine
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A turbine is a rotary mechanical device that extracts energy from a fluid flow and converts it into useful work. The work produced by a turbine can be used for generating power when combined with a generator or producing thrust. A turbine is a turbomachine with at least one moving part called a rotor assembly, moving fluid acts on the blades so that they move and impart rotational energy to the rotor. Early turbine examples are windmills and waterwheels, gas, steam, and water turbines have a casing around the blades that contains and controls the working fluid. Modern steam turbines frequently employ both reaction and impulse in the unit, typically varying the degree of reaction and impulse from the blade root to its periphery. Benoit Fourneyron, a student of Claude Burdin, built the first practical water turbine. A working fluid contains potential energy and kinetic energy, the fluid may be compressible or incompressible. Several physical principles are employed by turbines to collect this energy, the resulting impulse spins the turbine and leaves the fluid flow with diminished kinetic energy. There is no change of the fluid or gas in the turbine blades, as in the case of a steam or gas turbine. Before reaching the turbine, the pressure head is changed to velocity head by accelerating the fluid with a nozzle. Pelton wheels and de Laval turbines use this process exclusively, Impulse turbines do not require a pressure casement around the rotor since the fluid jet is created by the nozzle prior to reaching the blades on the rotor. Newtons second law describes the transfer of energy for impulse turbines, Impulse turbines are most efficient for use in cases where the flow is low and the inlet pressure is high. Reaction turbines develop torque by reacting to the gas or fluids pressure or mass, the pressure of the gas or fluid changes as it passes through the turbine rotor blades. A pressure casement is needed to contain the working fluid as it acts on the stage or the turbine must be fully immersed in the fluid flow. The casing contains and directs the working fluid and, for water turbines, Francis turbines and most steam turbines use this concept. For compressible working fluids, multiple stages are usually used to harness the expanding gas efficiently. Newtons third law describes the transfer of energy for reaction turbines, reaction turbines are better suited to higher flow velocities or applications where the fluid head is low. In practice, modern designs use both reaction and impulse concepts to varying degrees whenever possible
12.
Condenser (heat transfer)
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In systems involving heat transfer, a condenser is a device or unit used to condense a substance from its gaseous to its liquid state, by cooling it. In so doing, the latent heat is given up by the substance, Condensers can be made according to numerous designs, and come in many sizes ranging from rather small to very large. For example, a refrigerator uses a condenser to get rid of heat extracted from the interior of the unit to the outside air, Condensers are used in air conditioning, industrial chemical processes such as distillation, steam power plants and other heat-exchange systems. Use of cooling water or surrounding air as the coolant is common in many condensers, a surface condenser is an example of such a heat-exchange system. It is a shell and tube heat exchanger installed at the outlet of steam turbine in thermal power stations. Commonly, the water flows through the tube side and the steam enters the shell side where the condensation occurs on the outside of the heat transfer tubes. The condensate drips down and collects at the bottom, often in a built-in pan called a hotwell, the shell side often operates at a vacuum or partial vacuum, produced by the difference in specific volume between the steam and condensate. Conversely, the vapor can be fed through the tubes with the coolant water or air flowing around the outside, in chemistry, a condenser is the apparatus which cools hot vapors, causing them to condense into a liquid. See Condenser for laboratory-scale condensers, as opposed to industrial-scale condensers, examples include the Liebig condenser, Graham condenser, and Allihn condenser. This is not to be confused with a reaction which links two fragments into a single molecule by an addition reaction and an elimination reaction. In laboratory distillation, reflux, and rotary evaporators, several types of condensers are commonly used, the Liebig condenser is simply a straight tube within a cooling water jacket, and is the simplest form of condenser. Being more complex shapes to manufacture, these types are also more expensive to purchase. These three types of condensers are laboratory glassware items since they are made of glass. Larger condensers are used in industrial-scale distillation processes to cool distilled vapor into liquid distillate. Commonly, the coolant flows through the side and distilled vapor through the shell side with distillate collecting at or flowing out the bottom. A typical configuration of such a unit is as follows. In this heat exchanger section, the refrigerant goes through multiple tube passes, there is a motorized fan inside the condenser unit near the top, which is covered by some grating to keep any objects from accidentally falling inside on the fan. The fan is used to blow the outside cooling air in through the heat exchange section at the sides, of course, an electric power supply is needed for the compressor and fan inside the unit
13.
Pascal (unit)
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The pascal is the SI derived unit of pressure used to quantify internal pressure, stress, Youngs modulus and ultimate tensile strength. It is defined as one newton per square meter and it is named after the French polymath Blaise Pascal. Common multiple units of the pascal are the hectopascal which is equal to one millibar, the unit of measurement called standard atmosphere is defined as 101,325 Pa and approximates to the average pressure at sea-level at the latitude 45° N. Meteorological reports typically state atmospheric pressure in hectopascals, the unit is named after Blaise Pascal, noted for his contributions to hydrodynamics and hydrostatics, and experiments with a barometer. The name pascal was adopted for the SI unit newton per square metre by the 14th General Conference on Weights, one pascal is the pressure exerted by a force of magnitude one newton perpendicularly upon an area of one square metre. The unit of measurement called atmosphere or standard atmosphere is 101325 Pa and this value is often used as a reference pressure and specified as such in some national and international standards, such as ISO2787, ISO2533 and ISO5024. In contrast, IUPAC recommends the use of 100 kPa as a standard pressure when reporting the properties of substances, geophysicists use the gigapascal in measuring or calculating tectonic stresses and pressures within the Earth. Medical elastography measures tissue stiffness non-invasively with ultrasound or magnetic resonance imaging, in materials science and engineering, the pascal measures the stiffness, tensile strength and compressive strength of materials. In engineering use, because the pascal represents a small quantity. The pascal is also equivalent to the SI unit of energy density and this applies not only to the thermodynamics of pressurised gases, but also to the energy density of electric, magnetic, and gravitational fields. In measurements of sound pressure, or loudness of sound, one pascal is equal to 94 decibels SPL, the quietest sound a human can hear, known as the threshold of hearing, is 0 dB SPL, or 20 µPa. The airtightness of buildings is measured at 50 Pa, the units of atmospheric pressure commonly used in meteorology were formerly the bar, which was close to the average air pressure on Earth, and the millibar. Since the introduction of SI units, meteorologists generally measure pressures in hectopascals unit, exceptions include Canada and Portugal, which use kilopascals. In many other fields of science, the SI is preferred, many countries also use the millibar or hectopascal to give aviation altimeter settings. In practically all fields, the kilopascal is used instead. Centimetre of water Metric prefix Orders of magnitude Pascals law
14.
Pounds per square inch
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The pound per square inch or, more accurately, pound-force per square inch is a unit of pressure or of stress based on avoirdupois units. Now converting the psi to standard atmospheres,1 atm =101325 Pa =101325 Pa 6894.757293168 Pa / psi ≈14.70 psi Therefore,1 atmosphere is approximately 14.7 pounds per square inch. Pounds per square inch absolute is used to make it clear that the pressure is relative to a rather than the ambient atmospheric pressure. Since atmospheric pressure at sea level is around 14.7 psi, the converse is pounds per square inch gauge or pounds per square inch gage, indicating that the pressure is relative to atmospheric pressure. For example, a bicycle tire pumped up to 65 psi above atmospheric pressure. When gauge pressure is referenced to something other than ambient atmospheric pressure, the kilopound per square inch is a scaled unit derived from psi, equivalent to a thousand psi. Ksi are not widely used for gas pressures and they are mostly used in materials science, where the tensile strength of a material is measured as a large number of psi. The conversion in SI Units is 1 ksi =6.895 MPa, the megapound per square inch is another multiple equal to a million psi. It is used in mechanics for the modulus of the materials. The conversion in SI Units is 1 Mpsi =6.895 GPa, inch of water,0.036 psid Blood pressure – clinically normal human blood pressure,2.32 psig/1.55 psig Natural gas residential piped in for consumer appliance, 4–6 psig. Boost pressure provided by a turbocharger, 6–15 psig NFL football,12. 5–13.5 psig Atmospheric pressure at sea level,14
15.
Feedwater heater
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A feedwater heater is a power plant component used to pre-heat water delivered to a steam generating boiler. Preheating the feedwater reduces the irreversibilities involved in generation and therefore improves the thermodynamic efficiency of the system. This reduces plant operating costs and also helps to avoid thermal shock to the metal when the feedwater is introduced back into the steam cycle. In a steam plant, feedwater heaters allow the feedwater to be brought up to the saturation temperature very gradually. This minimizes the inevitable irreversibilities associated with transfer to the working fluid. See the article on the law of thermodynamics for a further discussion of such irreversibilities. The energy used to heat the feedwater is usually derived from steam extracted between the stages of the steam turbine, therefore, the steam that would be used to perform expansion work in the turbine is not utilized for that purpose. Feedwater heaters can also be open or closed heat exchangers, an open heat exchanger is one in which extracted steam is allowed to mix with the feedwater. This kind of heater will normally require a pump at both the feed inlet and outlet since the pressure in the heater is between the boiler pressure and the condenser pressure. A deaerator is a case of the open feedwater heater which is specifically designed to remove non-condensable gases from the feedwater. Closed feedwater heaters are typically shell and tube heat exchangers where the feedwater passes throughout the tubes and is heated by turbine extraction steam. These do not require separate pumps before and after the heater to boost the feedwater to the pressure of the steam as with an open heater. However, the steam must then be throttled to the condenser pressure. Many power plants incorporate a number of heaters and may use both open and closed components. Feedwater heaters are used in both fossil- and nuclear-fueled power plants, an economizer serves a similar purpose to a feedwater heater, but is technically different as it does not use cycle steam for heating. In fossil-fuel plants, the uses the lowest-temperature flue gas from the furnace to heat the water before it enters the boiler proper. This allows for the transfer between the furnace and the feedwater to occur across a smaller average temperature gradient. System efficiency is further increased when viewed with respect to actual energy content of the fuel
16.
Reactor pressure vessel
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A reactor pressure vessel in a nuclear power plant is the pressure vessel containing the nuclear reactor coolant, core shroud, and the reactor core. Not all power reactors have a pressure vessel. Power reactors are classified by the type of coolant rather than by the configuration of the reactor vessel used to contain the coolant. The classifications are, Light water reactor - Includes the pressurized water reactor, most nuclear power reactors are of this type. Graphite moderated reactor - Includes the Chernobyl reactor, which has an unusual reactor configuration compared to the vast majority of nuclear power plants in Russia. Gas cooled thermal reactor - Includes the advanced gas-cooled reactor, the gas cooled fast breeder reactor, an example of a gas cooled reactor is the British Magnox. Heavy water reactor - utilizes heavy water, or water with a higher than normal proportion of the isotope deuterium. However, D2O is more expensive and may be used as a main component, an example of a heavy water reactor is Canadas CANDU reactor. Liquid metal cooled reactor - utilizes a metal, such as sodium or a lead-bismuth alloy to cool the reactor core. Molten salt reactor - salts, typically fluorides of the alkali metals, operation is similar to metal-cooled reactors with high temperatures and low pressures, reducing pressure exerted on the reactor vessel versus water/steam-cooled designs. All pressurized water reactor pressure vessels share some features regardless of the particular design, the reactor vessel body is the largest component and is designed to contain the fuel assembly, coolant, and fittings to support coolant flow and support structures. It is usually cylindrical in shape and is open at the top to allow the fuel to be loaded and this structure is attached to the top of the reactor vessel body. It contains penetrations to allow the control rod driving mechanism to attach to the rods in the fuel assembly. The coolant level measurement probe also enters the vessel through the vessel head. The fuel assembly of nuclear fuel usually consisting of uranium or uranium/plutonium mixes and it is usually a rectangular block of gridded fuel rods. Protecting the inside of the vessel from fast neutron escaping from the assembly is a cylindrical shield wrapped around the fuel assembly. Reflectors send the neutrons back into the assembly to better utilize the fuel. The main purpose though is to protect the vessel from fast neutron induced damage that can make the vessel brittle, the RPV provides a critical role in safety of the PWR reactor and the materials used must be able to contain the reactor core at elevated temperatures and pressures
17.
Nuclear fuel
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Nuclear fuel is a substance that is used in nuclear power stations to produce heat to power turbines. Heat is created when nuclear fuel undergoes nuclear fission, most nuclear fuels contain heavy fissile elements that are capable of nuclear fission, such as uranium-235 or plutonium-239. When the unstable nuclei of atoms are hit by a slow-moving neutron, they split. These neutrons then go on to split more nuclei and this creates a self-sustaining chain reaction that is controlled in a nuclear reactor, or uncontrolled in a nuclear weapon. The processes involved in mining, refining, purifying, using, Nuclear fuel has the highest energy density of all practical fuel sources. Uranium dioxide is a black semiconducting solid and it can be made by reacting uranyl nitrate with a base to form a solid. It is heated to form U3O8 that can then be converted by heating in an argon / hydrogen mixture to form UO2, the UO2 is then mixed with an organic binder and pressed into pellets, these pellets are then fired at a much higher temperature to sinter the solid. The aim is to form a solid which has few pores. The thermal conductivity of uranium dioxide is low compared with that of zirconium metal. It is important to note that the corrosion of uranium dioxide in an environment is controlled by similar electrochemical processes to the galvanic corrosion of a metal surface. Mixed oxide, or MOX fuel, is a blend of plutonium, MOX fuel is an alternative to low enriched uranium fuel used in the light water reactors which predominate nuclear power generation. Some concern has been expressed that used MOX cores will introduce new disposal challenges, reprocessing of commercial nuclear fuel to make MOX was done in the Sellafield MOX Plant. As of 2015, MOX fuel is made in France, and to an extent in Russia, India. China plans to develop fast breeder reactors and reprocessing, reprocessing of spent commercial-reactor nuclear fuel has not been permitted in the United States due to nonproliferation considerations. It behaves like U-235 and its fission releases a similar amount of energy, the higher the burn-up, the more plutonium in the spent fuel, but the lower the fraction of fissile plutonium. Typically about one percent of the used fuel discharged from a reactor is plutonium, worldwide, some 70 tonnes of plutonium contained in used fuel is removed when refueling reactors each year. Metal fuels have the advantage of a higher heat conductivity than oxide fuels. Metal fuels have a history of use, stretching from the Clementine reactor in 1946 to many test
18.
Porosity
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Porosity or void fraction is a measure of the void spaces in a material, and is a fraction of the volume of voids over the total volume, between 0 and 1, or as a percentage between 0 and 100%. Strictly speaking, some measure the accessible void, the total amount of void space accessible from the surface. There are many ways to test porosity in a substance or part, the term porosity is used in multiple fields including pharmaceutics, ceramics, metallurgy, materials, manufacturing, earth sciences, soil mechanics and engineering. Void fraction usually varies from location to location in the flow channel and it fluctuates with time and its value is usually time averaged. In separated flow, it is related to flow rates of the gas and the liquid phase. It is defined by the ratio, ϕ = V V V T where VV is the volume of void-space and VT is the total or bulk volume of material, both the mathematical symbols ϕ and n are used to denote porosity. Porosity is a fraction between 0 and 1, typically ranging from less than 0.01 for solid granite to more than 0.5 for peat and it may also be represented in percent terms by multiplying the fraction by 100. The porosity of a rock, or sedimentary layer, is an important consideration when attempting to evaluate the potential volume of water or hydrocarbons it may contain. Sedimentary porosity is a function of many factors, including but not limited to, rate of burial, depth of burial, the nature of the connate fluids. The principal complication is that there is not a direct proportionality between porosity and hydraulic conductivity but rather an inferred proportionality, there is a clear proportionality between pore throat radii and hydraulic conductivity. Also, there tends to be a proportionality between pore throat radii and pore volume, if the proportionality between pore throat radii and porosity exists then a proportionality between porosity and hydraulic conductivity may exist. Well sorted materials have higher porosity than similarly sized poorly sorted materials, for tables of common porosity values for earth materials, see the further reading section in the Hydrogeology article. Consolidated rocks potentially have more complex dual porosities, as compared with alluvial sediment and this can be split into connected and unconnected porosity. Connected porosity is more easily measured through the volume of gas or liquid that can flow into the rock, porosity is the ratio of pore volume to its total volume. Porosity is controlled by, rock type, pore distribution, cementation, diagenetic history, porosity is not controlled by grain size, as the volume of between-grain space is related only to the method of grain packing. Rocks normally decrease in porosity with age and depth of burial, tertiary age Gulf Coast sandstones are in general more porous than Cambrian age sandstones. There are exceptions to this rule, usually because of the depth of burial and thermal history, porosity of surface soil typically decreases as particle size increases. This is due to soil formation in finer textured surface soils when subject to soil biological processes
19.
Control rod
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Control rods are used in nuclear reactors to control the fission rate of uranium and plutonium. They are composed of elements such as boron, silver. Because these elements have different capture cross sections for neutrons of varying energies, boiling water reactors, pressurized water reactors and heavy water reactors operate with thermal neutrons, while breeder reactors operate with fast neutrons. Control rods are used in control rod assemblies and inserted into guide tubes within a fuel element. This in turn affects the power, the amount of steam produced. Control rods often stand vertically within the core, in PWRs they are inserted from above, with the control rod drive mechanisms mounted on the reactor pressure vessel head. In BWRs, due to the necessity of a steam dryer above the core, the control rods are partially removed from the core to allow a chain reaction to occur. The number of control rods inserted and the distance to which they are inserted can be varied to control activity, typical shutdown time for modern reactors such as the European Pressurized Reactor or Advanced CANDU reactor is 2 seconds for 90% reduction, limited by decay heat. Chemical elements with a high neutron capture cross-section include silver. Other elements candidates include boron, cobalt, hafnium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium and lutetium. The material choice is influenced by the energy in the reactor, their resistance to neutron-induced swelling. The rods may have the form of tubes filled with neutron-absorbing pellets or powder and they can be made out of stainless steel or other neutron window materials such as zirconium, chromium, silicon carbide or cubic 11B15N. The burn up of the isotopes is another limiting lifespan factor. They may be reduced by capturing long isotope rows of the element or by not using neutron absorbers for trimming. For example, in pebble bed reactors or in possible new type 7lithium-moderated and -cooled reactors that use fuel, some rare earth elements are excellent neutron absorbers and are less rare than silver. Fission-produced xenon can be used after waiting for caesium to precipitate, cobalt-59 is also used as an absorber for winning of cobalt-60 for x-ray production. Control rods can also be constructed as thick turnable rods with a tungsten reflector, silver-indium-cadmium alloys, generally 80% Ag, 15% In and 5% Cd, are a common control rod material for pressurized water reactors. The somewhat different energy absorption regions of the make the alloy an excellent neutron absorber
20.
Boron carbide
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Boron carbide is an extremely hard boron–carbon ceramic, and covalent material used in tank armor, bulletproof vests, engine sabotage powders, as well as numerous industrial applications. With a Vickers Hardness of >30 GPa, it is one of the hardest known materials, behind cubic boron nitride, Boron carbide was discovered in 19th century as a by-product of reactions involving metal borides, however, its chemical formula was unknown. It was not until the 1930s that the composition was estimated as B4C. These features argued against a simple exact B4C empirical formula. Nuclear applications of boron carbide include shielding, control rod and shut down pellets, within control rods, boron carbide is often powdered, to increase its surface area. Boron carbide has a crystal structure typical of icosahedron-based borides. There, B12 icosahedra form a rhombohedral lattice unit surrounding a C-B-C chain that resides at the center of the unit cell and this structure is layered, the B12 icosahedra and bridging carbons form a network plane that spreads parallel to the c-plane and stacks along the c-axis. The lattice has two basic structure units – the B12 icosahedron and the B6 octahedron, because of the small size of the B6 octahedra, they cannot interconnect. Instead, they bond to the B12 icosahedra in the layer. Boron carbide is thus not a compound, but a family of compounds of different compositions. A common intermediate, which approximates a commonly found ratio of elements, is B12 = B6. 5C, in particular the crystal symmetry of the B4C composition and the non-metallic electrical character of the B13C2 composition. Boron carbide is known as a robust material having high hardness, high cross section for absorption of neutrons, stability to ionizing radiation and its Vickers hardness, Elastic Modulus and fracture toughness approach the corresponding values for diamond. As of 2015, boron carbide is the third hardest substance known, after diamond and cubic boron nitride, Boron carbide is a semiconductor, with electronic properties dominated by hopping-type transport. The energy band gap depends on composition as well as the degree of order, the band gap is estimated at 2.09 eV, with multiple mid-bandgap states which complicate the photoluminescence spectrum. Boron carbide was first synthesized by Henri Moissan in 1899, by reduction of boron trioxide either with carbon or magnesium in presence of carbon in an arc furnace. Padlocks Personal and vehicle anti-ballistic armor plating, high energy fuel for solid fuel Ramjets Zip_fuel. In brake linings of vehicles List of compounds with carbon number 1 Alan W. Weimer, Carbide, Nitride and Boride Materials Synthesis and Processing. National Pollutant Inventory – Boron and compounds NIST Chemistry Database Entry for Boron Carbide
21.
Radionuclide
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A radionuclide is an atom that has excess nuclear energy, making it unstable. During those processes, the radionuclide is said to undergo radioactive decay, the unstable nucleus is more stable following the emission, but will sometimes undergo further decay. Radioactive decay is a process at the level of single atoms. However, for a collection of atoms of an element the decay rate. The range of the half-lives of radioactive atoms have no known limits, Radionuclides occur naturally and are artificially produced in nuclear reactors, cyclotrons, particle accelerators or radionuclide generators. There are about 730 radionuclides with half-lives longer than 60 minutes, with the longest half lives are the 32 primordial radionuclides that have survived from the creation of the Solar System. Over 60 further radionuclides are detectable in nature, either as daughters of these, more than 2400 radionuclides have half-lives less than 60 minutes. Most of those are produced artificially, and have very short half-lives. For comparison, there are about 254 stable nuclides, even the lightest element, hydrogen, has a well-known radionuclide, tritium. Elements heavier than lead, and the elements technetium and promethium, unplanned exposure to radionuclides generally has a harmful effect on living organisms including humans, although low levels of exposure occur naturally without harm. However, radionuclides with suitable properties are used in medicine for both diagnosis and treatment. An imaging tracer made with radionuclides is called a radioactive tracer, a pharmaceutical drug made with radionuclides is called a radiopharmaceutical. On Earth, naturally occurring radionuclides fall into three categories, primordial radionuclides, secondary radionuclides, and cosmogenic radionuclides, Radionuclides are produced in stellar nucleosynthesis and supernova explosions along with stable nuclides. Most decay quickly but can still be observed astronomically and can play a part in understanding astronomic processes, primordial radionuclides, such as uranium and thorium, exist in the present time because their half-lives are so long they have not yet completely decayed. It is possible decay may be observed in other nuclides adding to this list of primordial radionuclides, secondary radionuclides are radiogenic isotopes derived from the decay of primordial radionuclides. They have shorter half-lives than primordial radionuclides and they arise in the decay chain of the primordial isotopes thorium-232, uranium-238 and uranium-235. Examples include the natural isotopes of polonium and radium, cosmogenic isotopes, such as carbon-14, are present because they are continually being formed in the atmosphere due to cosmic rays. Many of these radionuclides exist only in trace amounts in nature, secondary radionuclides will occur in proportion to their half-lives, so short-lived ones will be very rare
22.
Half-life
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Half-life is the time required for a quantity to reduce to half its initial value. The term is used in nuclear physics to describe how quickly unstable atoms undergo. The term is used more generally to characterize any type of exponential or non-exponential decay. For example, the medical sciences refer to the biological half-life of drugs, the converse of half-life is doubling time. The original term, half-life period, dating to Ernest Rutherfords discovery of the principle in 1907, was shortened to half-life in the early 1950s. Rutherford applied the principle of a radioactive elements half-life to studies of age determination of rocks by measuring the period of radium to lead-206. Half-life is constant over the lifetime of an exponentially decaying quantity, the accompanying table shows the reduction of a quantity as a function of the number of half-lives elapsed. A half-life usually describes the decay of discrete entities, such as radioactive atoms, in that case, it does not work to use the definition that states half-life is the time required for exactly half of the entities to decay. For example, if there are 3 radioactive atoms with a half-life of one second, instead, the half-life is defined in terms of probability, Half-life is the time required for exactly half of the entities to decay on average. In other words, the probability of a radioactive atom decaying within its half-life is 50%, for example, the image on the right is a simulation of many identical atoms undergoing radioactive decay. Note that after one half-life there are not exactly one-half of the remaining, only approximately. Nevertheless, when there are many identical atoms decaying, the law of large numbers suggests that it is a good approximation to say that half of the atoms remain after one half-life. There are various simple exercises that demonstrate probabilistic decay, for example involving flipping coins or running a computer program. The three parameters t1⁄2, τ, and λ are all related in the following way. Amount approaches zero as t approaches infinity as expected, some quantities decay by two exponential-decay processes simultaneously. There is a half-life describing any exponential-decay process, for example, The current flowing through an RC circuit or RL circuit decays with a half-life of RCln or lnL/R, respectively. For this example, the half time might be used instead of half life. In a first-order chemical reaction, the half-life of the reactant is ln/λ, in radioactive decay, the half-life is the length of time after which there is a 50% chance that an atom will have undergone nuclear decay
23.
Enriched uranium
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Enriched uranium is a type of uranium in which the percent composition of uranium-235 has been increased through the process of isotope separation. Natural uranium is 99. 284% 238U isotope, with 235U only constituting about 0. 711% of its weight, 235U is the only nuclide existing in nature that is fissile with thermal neutrons. Enriched uranium is a component for both civil nuclear power generation and military nuclear weapons. During the Manhattan Project enriched uranium was given the codename oralloy, the term oralloy is still occasionally used to refer to enriched uranium. There are about 2,000 tonnes of enriched uranium in the world, produced mostly for nuclear weapons, naval propulsion. At present,95 percent of the stocks of depleted uranium remain in secure storage. Uranium as it is directly from the Earth is not suitable as fuel for most nuclear reactors. Uranium is mined underground or in an open pit depending on the depth in which it is found. After the uranium ore is mined, it must go through a process to extract the uranium from the ore. 1% uranium. Naturally-occurring uranium is made of a mixture of U-235 and U-238, the U-235 is fissile meaning it is easily split with neutrons while the remainder is U-238, but in nature, more than 99% of the extracted ore is U-238. Most nuclear reactors require enriched uranium, which is uranium with higher concentrations of U-235 ranging between 3. 5% and 4. 5%, there are two commercial enrichment processes, gaseous diffusion and gas centrifugation. Both enrichment processes involve the use of uranium hexafluoride and produce enriched uranium oxide, reprocessed uranium is a product of nuclear fuel cycles involving nuclear reprocessing of spent fuel. Low-enriched uranium has a lower than 20% concentration of 235U, for instance, in light water reactors. Fresh LEU used in research reactors is usually enriched 12% to 19. 75% U-235, highly enriched uranium has a 20% or higher concentration of 235U. 4% 235U being required. For criticality experiments, enrichment of uranium to over 97% has been accomplished, the very first uranium bomb, Little Boy dropped by the United States on Hiroshima in 1945, used 64 kilograms of 80% enriched uranium. Wrapping the weapons fissile core in a neutron reflector can dramatically reduce the critical mass, because the core was surrounded by a good neutron reflector, at explosion it comprised almost 2.5 critical masses. The presence of too much of the 238U isotope inhibits the nuclear chain reaction that is responsible for the weapons power. The critical mass for 85% highly enriched uranium is about 50 kilograms, for the secondary of a large nuclear weapon, the higher critical mass of less-enriched uranium can be an advantage as it allows the core at explosion time to contain a larger amount of fuel
24.
Boiling water reactor safety systems
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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. This type of event is referred to as a pressure transient, in the limiting case of an ATWS derangement, high neutron power levels can occur for less than a second, after which actuation of SRVs will cause the pressure to rapidly drop off. Neutronic power will fall to far below nominal power even before ARI or SLCS actuation occurs, thermal power will be barely affected. However, the containment building does not protect the fuel during the fuel cycle. Most importantly, the spent fuel resides long periods of time outside the primary containment, a typical spent fuel storage pool can hold roughly five times the fuel in the core. Since reloads typically discharge one third of a core, much of the spent fuel stored in the pool will have had considerable decay time. But if the pool were to be drained of water, the fuel from the previous two refuelings would still be fresh enough to melt under decay heat. However, the cladding of this fuel could be ignited during the heatup. The resulting fire would spread to most or all of the fuel in the pool. The heat of combustion, in combination with heat, would probably drive borderline aged fuel into a molten condition. This would cause a release of products from the fuel matrix quite comparable to that of molten fuel. In addition, although confined, BWR spent fuel pools are almost always located outside of the primary containment, generation of hydrogen during the process would probably result in an explosion, damaging the secondary containment building. Thus, release to the atmosphere is more likely than for comparable accidents involving the reactor core, in addition, the RPS can automatically spin up the Emergency Core Cooling System upon detection of several signals. It does not require human intervention to operate, however, the reactor operators can override parts of the RPS if necessary. If an operator recognizes a deteriorating condition, and knows an automatic safety system will activate, they are trained to pre-emptively activate the safety system. If the reactor is at power or ascending to power, there are safety-related contingencies that may arise that necessitate a rapid shutdown of the reactor, or, in Western nuclear parlance, a SCRAM. The SCRAM is a manually triggered or automatically triggered rapid insertion of all control rods into the reactor, manual SCRAMs may be initiated by the reactor operators, while automatic SCRAMs are initiated upon, Turbine stop-valve or turbine control-valve closure. If turbine protection systems detect a significant anomaly, admission of steam is halted, Reactor rapid shutdown is in anticipation of a pressure transient that could increase reactivity
25.
Defence in depth
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Defence in depth is a military strategy that seeks to delay rather than prevent the advance of an attacker, buying time and causing additional casualties by yielding space. Rather than defeating an attacker with a single, strong defensive line, a defender can thus yield lightly defended territory in an effort to stress an attackers logistics or spread out a numerically superior attacking force. Defence in depth requires that a defender deploy their resources, such as fortifications, field works and military units at, although attackers may find it easier to breach the more weakly defended front line, as they advance, they continue to meet resistance. As they penetrate deeper, their flanks become vulnerable, and, should the advance stall, the defence in depth strategy is particularly effective against attackers able to concentrate their forces and attack a small number of places on an extended defensive line. Defenders that can back to a succession of prepared positions can extract a high price from the advancing enemy while themselves avoiding the danger of being overrun or outflanked. Delaying the enemy advance mitigates the attackers advantage of surprise and allows time to move defending units to make a defence, a well-planned defence in depth strategy will deploy forces in mutually supportive positions and in appropriate roles. For example, poorly trained troops may be deployed in static defences at the front line, defence in depth may allow a defender to maximise the defensive possibilities of natural terrain and other advantages. The disadvantages of defence in depth are that it may be unacceptable for a defender to plan to give ground to an attacker. This may be because vital military or economic resources are close to the front line or because yielding to an enemy is unacceptable for political or cultural reasons. In addition, the continuous retreats required by defence in depth require the defender to have a degree of mobility in order to retreat successfully. Edward Luttwak used the term to describe his theory of the strategy employed by the Late Roman army in the 3rd. Later examples of defence in depth might be European hill forts, during the Battle of Normandy, Wehrmacht forces utilized the bocage of the area to create successive lines of defences to slow the attacking Allies in hopes that reinforcements would arrive. The Pacific Theatre also had examples of defence in depth, with the Japanese inflicting heavy casualties on the Americans in the Battles of Tarawa, Saipan, Peleliu, Iwo Jima. The best modern example of a defence in depth is that of the Battle of Kursk. The initial German offensive never fully penetrated the Red Army lines, by contrast, the subsequent Red Army counter-offensive pushed the front line hundreds of miles westwards. Colonel Francis J. Kelly discussed the employment of defence in depth in Army Special Forces camps during the Vietnam War, while untested, this was also the planned NATO strategy in Europe during the Cold War at the Fulda Gap. Bandwagoning Culminating point Hedgehog defence List of military tactics Loss of Strength Gradient Scorched earth policy Soviet deep battle Strategic depth
26.
Radioactive decay
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A material containing such unstable nuclei is considered radioactive. Certain highly excited short-lived nuclear states can decay through neutron emission, or more rarely, however, for a collection of atoms, the collections expected decay rate is characterized in terms of their measured decay constants or half-lives. This is the basis of radiometric dating, the half-lives of radioactive atoms have no known upper limit, spanning a time range of over 55 orders of magnitude, from nearly instantaneous to far longer than the age of the universe. A radioactive nucleus with spin can have no defined orientation. If there are multiple particles produced during a single decay, as in decay, their relative angular distribution. Such a parent process could be a previous decay, or a nuclear reaction, the decaying nucleus is called the parent radionuclide, and the process produces at least one daughter nuclide. Except for gamma decay or internal conversion from an excited state. When the number of changes, an atom of a different chemical element is created. The first decay processes to be discovered were alpha decay, beta decay, alpha decay occurs when the nucleus ejects an alpha particle. This is the most common process of emitting nucleons, but highly excited nuclei can eject single nucleons, or in the case of cluster decay, specific light nuclei of other elements. Beta decay occurs when the nucleus emits an electron or positron, the nucleus may capture an orbiting electron, causing a proton to convert into a neutron in a process called electron capture. All of these result in a well-defined nuclear transmutation. By contrast, there are radioactive decay processes that do not result in a nuclear transmutation, another type of radioactive decay results in products that vary, appearing as two or more fragments of the original nucleus with a range of possible masses. For a summary table showing the number of stable and radioactive nuclides in each category, there are 29 naturally occurring chemical elements on Earth that are radioactive. They are those that contain 34 radionuclides that date before the time of formation of the solar system, well-known examples are uranium and thorium, but also included are naturally occurring long-lived radioisotopes, such as potassium-40. Radioactivity was discovered in 1896 by the French scientist Henri Becquerel and these materials glow in the dark after exposure to light, and he suspected that the glow produced in cathode ray tubes by X-rays might be associated with phosphorescence. He wrapped a photographic plate in black paper and placed various phosphorescent salts on it, all results were negative until he used uranium salts. The uranium salts caused a blackening of the plate in spite of the plate being wrapped in black paper and these radiations were given the name Becquerel Rays
27.
Neutron absorption
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Neutron capture is a nuclear reaction in which an atomic nucleus and one or more neutrons collide and merge to form a heavier nucleus. Since neutrons have no electric charge they can enter a more easily than positively charged protons. Neutron capture plays an important role in the nucleosynthesis of heavy elements. In stars it can proceed in two ways, as a rapid or a slow process, nuclei of masses greater than 56 cannot be formed by thermonuclear reactions, but can be formed by neutron capture. At small neutron flux, as in a reactor, a single neutron is captured by a nucleus. For example, when natural gold is irradiated by neutrons, the isotope 198Au is formed in an excited state. In this process, the number increases by one. This is written as a formula in the form 197Au+n → 198Au+γ, if thermal neutrons are used, the process is called thermal capture. The isotope 198Au is a beta emitter that decays into the mercury isotope 198Hg, in this process the atomic number rises by one. The r-process happens inside stars if the flux density is so high that the atomic nucleus has no time to decay via beta emission in between neutron captures. The mass number therefore rises by a large amount while the atomic number stays the same, only afterwards, the highly unstable nuclei decay via many β− decays to stable or unstable nuclei of high atomic number. It is usually measured in barns, absorption cross section is often highly dependent on neutron energy. As a generality, the likelihood of absorption is proportional to the time the neutron is in the vicinity of the nucleus, the time spent in the vicinity of the nucleus is inversely proportional to the relative velocity between the neutron and nucleus. Other more specific issues modify this general principle, the thermal energy of the nucleus also has an effect, as temperatures rise, Doppler broadening increases the chance of catching a resonance peak. In particular, the increase in uranium-238s ability to absorb neutrons at higher temperatures is a feedback mechanism that helps keep nuclear reactors under control. Neutron capture is involved in the formation of isotopes of chemical elements, as a consequence of this fact the energy of neutron capture intervenes in the standard enthalpy of formation of isotopes. Neutron activation analysis can be used to detect the chemical composition of materials. This is because different elements release different characteristic radiation when they absorb neutrons and this makes it useful in many fields related to mineral exploration and security
28.
Fukushima Daiichi nuclear disaster
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The Fukushima Daiichi nuclear disaster was an energy accident at the Fukushima I Nuclear Power Plant in Fukushima, initiated primarily by the tsunami following the Tōhoku earthquake on 11 March 2011. Immediately after the earthquake, the reactors automatically shut down their sustained fission reactions. However, the disabled the emergency generators that would have provided power to control. The insufficient cooling led to three nuclear meltdowns, hydrogen-air chemical explosions, and the release of material in Units 1,2 and 3 from 12 March to 15 March. Loss of cooling also caused the pool for storing spent fuel from Reactor 4 to overheat on 15 March due to the heat from the fuel rods. On 12 October 2012, TEPCO admitted for the first time that it had failed to take measures for fear of inviting lawsuits or protests against its nuclear plants. However, an estimated 1,600 deaths are believed to have occurred due to the resultant evacuation conditions, There are no clear plans for decommissioning the plant, but the plant management estimate is 30 or 40 years. Radiation levels of about 650 sieverts per hour have been detected in the containment vessel of reactor No.2, the Fukushima I Nuclear Power Plant comprised six separate boiling water reactors originally designed by General Electric and maintained by the Tokyo Electric Power Company. At the time of the Tōhoku earthquake on 11 March 2011, however, their spent fuel pools still required cooling. As the reactors were unable to power to run their own coolant pumps, emergency diesel generators came online, as designed, to power electronics. These operated nominally until the destroyed the generators for reactors 1–5. The largest tsunami wave was 13 meters high and hit 50 minutes after the earthquake, overwhelming the plants seawall. The moment of impact was recorded by a camera, water quickly flooded the low-lying rooms in which the emergency generators were housed. The flooded diesel generators failed soon afterwards, resulting in a loss of power to the coolant water pumps. The fuel rods would become hot enough to melt during the decay time period if an adequate heat sink was not available. After the secondary emergency pumps ran out, one day after the tsunami,12 March, the pumps stopped. The insufficient cooling led to meltdowns in reactors 1,2, and 3. It is estimated that the hot zirconium fuel cladding-water reaction in reactors 1–3 produced 800 to 1000 kilograms of hydrogen gas each
29.
Captain (naval)
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Captain is the name most often given in English-speaking navies to the rank corresponding to command of the largest ships. The rank is equal to the rank of colonel. Equivalent ranks worldwide include ship-of-the-line captain, captain of sea and war, captain at sea, the NATO rank code is OF-5, although the United States of America uses the code O-6 for the equivalent rank. O. The naval rank should not be confused with the army, air force, or marine ranks of captain, on large US ships, the executive officer may be a captain in rank, in which case it would be proper to address him by rank. Often the XO prefers to be called XO to avoid confusion with the CO, who is also a captain in rank and the captain of the ship. Captains with sea commands generally command ships of size or larger, the more senior the officer, the larger the ship. Even when an officer who is in the ships captains chain of command is present. The following articles deal with the rank of captain as it is used in various navies, Captain Captain Captain Capitaine de vaisseau Kapitän zur See Komandor Kapitan of the 1st rank Sea captain Post captain
30.
Hyman G. Rickover
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Admiral Hyman G. Rickover, U. S. Navy, directed the original development of naval nuclear propulsion and controlled its operations for three decades as director of Naval Reactors. In addition, he oversaw the development of the Shippingport Atomic Power Station, a naval officer who served in a flag rank for nearly 30 years – from 1953 to 1982 – Rickover was promoted to four-star admiral after 51 years of commissioned service. Vessels are now decommissioned and others are under construction, Rickover is the only person who has ever been awarded two Congressional Gold Medals. Rickover was born Chaim Godalia Rickover, to Abraham Rickover and Rachel Rickover and his parents later changed his name to Hyman, which, like Chaim, is derived from Chayyim, meaning life. He did not use his name, Godalia, but when required to list one for the Naval Academy oath. The family name Rickover is derived from the village and the estate of Ryki, located within 100 kilometres of Warsaw, decades later, the entire remaining Jewish communities of Ryki and Maków Mazowiecki were killed or otherwise perished during the Holocaust. Rickover took his first paid job at nine years of age and he graduated from grammar school at 14. While attending John Marshall High School in Chicago, Rickover held a job as a telegraph boy delivering Western Union telegrams. Congressman Adolph J. Sabath, himself a Czech Jewish immigrant, through the intervention of a family friend, Sabath nominated Rickover for appointment to the United States Naval Academy. Rickover was only an alternate for appointment, but through disciplined self-directed study and good fortune. Rickovers active duty career began in 1918, during a time when attending military academies was considered active duty service. On 2 June 1922, Rickover graduated 107th out of 540 midshipmen and was commissioned as an ensign and he joined the destroyer La Vallette on 5 September 1922. Rickover impressed his commanding officer with his work and efficiency. At Columbia, he met Ruth D. Masters, a Christian and graduate student in international law, shortly after marrying, Rickover wrote to his parents of his decision to become an Episcopalian, remaining so for the remainder of his life. Columbia was the first institution that encouraged me to think rather than memorize and my teachers were notable in that many had gained practical engineering experience outside the university and were able to share their experience with their students. I am grateful, among others, to Professors Morecroft, Hehre, much of what I have subsequently learned and accomplished in engineering is based on the solid foundation of principles I learned from them. I am therefore especially gratified by your invitation to return and speak this evening, Rickover preferred life on smaller ships, and he also knew that young officers in the submarine service were advancing quickly, so he went to Washington and volunteered for submarine duty. His application was turned down due to his age, at that time 29 years, fortunately for Rickover, he ran into his former commanding officer from Nevada while leaving the building, who interceded successfully on his behalf
31.
Argonne National Laboratory
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It is the largest national laboratory by size and scope in the Midwest. UChicago Argonne, LLC, the operator of the laboratory, brings together the expertise of the University of Chicago with Jacobs Engineering Group Inc, Argonne is a part of the expanding Illinois Technology and Research Corridor. Argonne formerly ran a facility called Argonne National Laboratory-West in Idaho next to the Idaho National Engineering. In 2005, the two Idaho-based laboratories merged to become the Idaho National Laboratory, Argonne has five main areas of focus. Argonne began in 1942 as the Metallurgical Laboratory at the University of Chicago, the Met Lab built Chicago Pile-1, the worlds first nuclear reactor, under the stands of a University of Chicago sports stadium. Considered unsafe, in 1943, CP-1 was reconstructed as CP-2, the lab was named after the surrounding Argonne Forest, which in turn was named after the Forest of Argonne in France where U. S. troops fought in World War I. Fermis pile was originally going to be constructed in the Argonne forest, and construction plans were set in motion, since speed was paramount, the project was moved to the squash court under Stagg Field, the football field on the campus of the University of Chicago. Fermi told them that he was sure of his calculations, which said that it would not lead to a runaway reaction, other activities were added to Argonne over the next five years. On July 1,1946, the Metallurgical Laboratory was formally re-chartered as Argonne National Laboratory for cooperative research in nucleonics, at the request of the U. S. Atomic Energy Commission, it began developing nuclear reactors for the peaceful nuclear energy program. A complete list of the designed and, in most cases, built and operated by Argonne can be viewed in the. Such alluring secrecy drew visitors both authorized—including King Leopold III of Belgium and Queen Frederica of Greece—and unauthorized, shortly past 1 a. m. on February 6,1951, Argonne guards discovered reporter Paul Harvey near the 10-foot perimeter fence, his coat tangled in the barbed wire. Searching his car, guards found a previously prepared four-page broadcast detailing the saga of his entrance into a classified hot zone. He was brought before a grand jury on charges of conspiracy to obtain information on national security and transmit it to the public. Not all nuclear technology went into developing reactors, however, remote manipulators designed to handle radioactive materials laid the groundwork for more complex machines used to clean up contaminated areas, sealed laboratories or caves. In addition to work, the laboratory maintained a strong presence in the basic research of physics. In 1955, Argonne chemists co-discovered the elements einsteinium and fermium, in 1962, laboratory chemists produced the first compound of the inert noble gas xenon, opening up a new field of chemical bonding research. In 1963, they discovered the hydrated electron, high-energy physics made a leap forward when Argonne was chosen as the site of the 12.5 GeV Zero Gradient Synchrotron, a proton accelerator that opened in 1963
32.
BORAX experiments
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They were performed using the five BORAX reactors that were designed and built by Argonne. BORAX-III was the first nuclear reactor to supply power to the grid in the United States in 1955. This series of tests began in 1952 with the construction of the BORAX-I nuclear reactor, BORAX-I experiment proved that a reactor using direct boiling of water would be practical, rather than unstable, because of the bubble formation in the core. Subsequently the reactor was used for power excursion tests which showed that rapid conversion of water to steam would safely control the reaction. The final, deliberately destructive test in 1954 produced a large power excursion that instead of the melting of a few fuel plates. However, this core meltdown and release of fuel and fission products provided additional useful data to improve mathematical models. The tests proved key safety principles of the design of nuclear power reactors. Design power of BORAX-I was 1.4 megawatts thermal, the BORAX-I design was a precursor to the SL-1 plant, which was sited nearby and began operations in 1958. The principles discovered in the BORAX-I experiments helped scientists understand the issues which contributed to the incident at SL-1 in 1961. The BORAX-II reactor was built in 1954, with an output of 6 MW. In March 1955 BORAX-II was intentionally destroyed by taking the reactor prompt critical, the design of BORAX-II was modified into BORAX-III with the addition of a turbine, proving that turbine contamination would not be a problem. It was linked to the power grid for about an hour on July 17,1955. BORAX-III provided 2,000 kW to power nearby Arco, Idaho, the BORAX test facility, thus Arco became the first city solely powered by nuclear energy. The reactor continued to be used for tests until 1956, bORAX-IV, built in 1956, explored the thorium fuel cycle and uranium-233 fuel with a power of 20 MW thermal. This experiment utilized fuel plates that were full of defects in order to explore long-term plant operation with damaged fuel plates. Radioactive gasses were released into the atmosphere, bORAX-V continued the work on boiling water reactor designs, including the use of a superheater. It operated from 1962 to 1964, test synopsis, The carried out by withdrawing four of the five control rods far enough to make the reactor critical at a very low power level. The fifth rod was then fired from the core by means of a spring, in this test, the rod was ejected in approximately 0.2 seconds
33.
GE BWR
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General Electrics BWR product line of Boiling Water Reactors represents the designs of a large percent of the fission reactors around the world. The progenitor of the BWR line was the 5MW Reactor at the Valiecitos Boiling-Water reactor in 1957. Elk River - 5x5 fuel rod bundle Lacrosse - 10x10 fuel rod bundle BWR Type 1, In 1955 GE developed this design into the 180MW Dresden 1 reactor, GE would further develop this design with Big Rock Point, and Humboldt Bay, but sharing the BWR1 classification. These three experimental designs used fuel rod bundles in 6x6, 8x8, 9x9, 11x11, 12x12, an example of designs later classified as Generation I reactor Humboldt Bay and Dodewaard had natural circulation. Type 1 was the first design with internal steam separation and it also had an isolation condenser, and pressure suppression containment. BWR Type 2,1963 500MW Included a large direct cycle, oyster Creek had a large direct cycle. BWR Type 3, Introduced in 1965 800MW Improved ECCS with spray, Dresden 2 and Browns Ferry had improved ECCS, spray and flood. They also had a reactor core isolation cooling system, BWR Type 4, Introduced in 19661, 100MW Increased power density 20%. BWR Type 5, Introduced in 1969 Improved ECCS valve flow control, a 1. 22GW electrical BWR6 has 177 control rods and 748 fuel assemblies for a total of 46,376 fuel rods. It had a gravity containment flooder, and they had options for a control room. ABWR, Higher safety margins, no external recirculation loops, reactor internal pumps and it also has fine motion control rod drives. ESBWR, Passive safety, natural circulation,1, 600MW It has a gravity flooder, isolation condenser, Improved 7x7 fuel bundle with 49 fuel rods, one of which is segmented. 8x8 fuel bundle with 63 fuel rods and 1 water rod, retrofit 8x8 fuel bundle Prepressurized and Barrier fuel bundles containing 62 and two water rods. Prepressurized at 3ATM with helium with a Barrier 8x8 fuel bundle with 58 to 62 fuel rods, a drywell Containment building which resembles an inverted lightbulb above the wetwell which is a steel torus containing water. Described as a configuration with the drywell forming a truncated cone on a concrete slab. Below is a cylindrical suppression chamber made of concrete rather than just sheet metal, bottom entry bottom mounted control rods allow refueling without removal of the control rods and drives, while also allowing drive testing with an open vessel prior to fuel loading. BWR allow lower primary coolant flow than PWR, jet pumps internal to the reactor vessel provide 2/3rds of the recirculation flow allowing the external recirculation flow loop to be small and compact compared to contemporary PWR designs. S. Economics of new power plants Pressurized water reactor Reduced moderation water reactor Advanced Heavy Water Reactor Other Gen III+ designs AP1000 ESBWR ABWR US-APWR ACR
34.
Torus
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In geometry, a torus is a surface of revolution generated by revolving a circle in three-dimensional space about an axis coplanar with the circle. If the axis of revolution does not touch the circle, the surface has a shape and is called a torus of revolution. Real-world examples of objects include inner tubes, swim rings, and the surface of a doughnut. A torus should not be confused with a solid torus, which is formed by rotating a disc, rather than a circle, a solid torus is a torus plus the volume inside the torus. Real-world approximations include doughnuts, vadai or vada, many lifebuoys, in topology, a ring torus is homeomorphic to the Cartesian product of two circles, S1 × S1, and the latter is taken to be the definition in that context. It is a compact 2-manifold of genus 1, the ring torus is one way to embed this space into three-dimensional Euclidean space, but another way to do this is the Cartesian product of the embedding of S1 in the plane. This produces an object called the Clifford torus, a surface in 4-space. In the field of topology, a torus is any space that is topologically equivalent to a torus. R is known as the radius and r is known as the minor radius. The ratio R divided by r is known as the aspect ratio, a doughnut has an aspect ratio of about 2 to 3. An implicit equation in Cartesian coordinates for a torus radially symmetric about the z-axis is 2 + z 2 = r 2, or the solution of f =0, algebraically eliminating the square root gives a quartic equation,2 =4 R2. The three different classes of standard tori correspond to the three aspect ratios between R and r, When R > r, the surface will be the familiar ring torus. R = r corresponds to the torus, which in effect is a torus with no hole. R < r describes the self-intersecting spindle torus, when R =0, the torus degenerates to the sphere. When R ≥ r, the interior 2 + z 2 < r 2 of this torus is diffeomorphic to a product of an Euclidean open disc, the losses in surface area and volume on the inner side of the tube exactly cancel out the gains on the outer side. In traditional spherical coordinates there are three measures, R, the distance from the center of the system, and θ and φ. As a torus has, effectively, two points, the centerpoints of the angles are moved, φ measures the same angle as it does in the spherical system. The center point of θ is moved to the center of r and these terms were first used in a discussion of the Earths magnetic field, where poloidal was used to denote the direction toward the poles
35.
Containment building
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A containment building, in its most common usage, is a reinforced steel or lead structure enclosing a nuclear reactor. It is designed, in any emergency, to contain the escape of steam or gas to a maximum pressure in the range of 275 to 550 kPa. Each nuclear plant in the US is designed to certain conditions which are spelled out as Design Basis Accidents in the Final Safety Analysis Report. The FSAR is available for viewing, usually at a public library near the nuclear plant. The containment building itself is typically a steel structure enclosing the reactor normally sealed off from the outside atmosphere. The steel is either free-standing or attached to the missile shield. This, combined with further failures, caused the release of up to 13 million curies of radioactive gas to atmosphere during the accident and these systems were necessary to keep the fuel cool after the reactor had been shut down. Hydrogen leaking from the containment mixed with air into a mixture which resulted in explosions in Unit 1,3 and 4. Containment systems for power reactors are distinguished by size, shape, materials used. The kind of containment used is determined by the type of reactor, generation of the reactor, suppression systems are critical to safety analysis and greatly affect the size of containment. Suppression refers to condensing the steam after a break has released it from the cooling system. Because decay heat does not go quickly, there must be some long term method of suppression. There are several designs, but for safety-analysis purposes containments are categorized as either large-dry, sub-atmospheric. For a pressurized water reactor, the containment also encloses the steam generators and the pressurizer, the missile shield around it is typically a tall cylindrical or domed building. Early designs including Siemens, Westinghouse, and Combustion Engineering had a mostly can-like shape built with reinforced concrete, as reactor designs have evolved, many nearly spherical containment designs for PWRs have also been constructed. Depending on the used, this is the most apparently logical design because a sphere is the best structure for simply containing a large pressure. Most current PWR designs involve some combination of the two, with a lower part and a half-spherical top. The spent fuel pool is outside of the containment building in most PWR designs, modern designs have also shifted more towards using steel containment structures
36.
Browns Ferry Nuclear Power Plant
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The Browns Ferry Nuclear Plant is located on the Tennessee River near Decatur and Athens, Alabama, on the north side of Wheeler Lake. The nuclear power plant is named after a ferry operated at the site until the middle of the 20th century. The site has three General Electric boiling water reactor nuclear generating units and is owned entirely by the Tennessee Valley Authority, Browns Ferry was TVAs first nuclear power plant, its approval occurred on June 17,1966 and construction began in September 1966. In 1974, the time of its operation, it was the largest nuclear plant in the world. It was the first nuclear plant in the world to more than 1 gigawatt of power. In 2006, the Nuclear Regulatory Commission renewed the licenses for all three reactors, extending them for a twenty years. The 2010 U. S. population within 10 miles of Browns Ferry was 39,930, the 2010 U. S. population within 50 miles was 977,942, an increase of 11.0 percent since 2000. Cities within 50 miles include Huntsville, at 5,01 PM on April 27,2011, all three reactors scrammed due to loss of external power caused by a tornado in the vicinity of the plant. Control rod insertion and cooling procedures operated as designed with no damage or release of radiation. Diesel backup generators provided power after a period of outage. An NRC Unusual Event, the lowest level of classification, was declared due to loss of power exceeding 15 minutes. Additionally, an oil leak was found on one generator. Due to widespread transmission grid damage from the storms, Browns Ferry was unable to power for the grid. Unit One is a 1,065 MWe BWR built by General Electric, construction started on Unit One September 12,1966 and originally came online on December 20,1973. It is licensed to operate through December 20,2033, however, Unit One was shut down for a year after a fire in 1975 damaged the unit. The unit was repaired and operated from 1976 through 1985. Units Two and Three were restarted in 1991 and 1995, respectively, starting in 2002, TVA undertook an effort to restore Unit One to operational status, spending $1.8 billion to do so. The NRC approved the restart of Unit 1 on May 15,2007, Reactor power-up and tests resumed on May 27 and the unit started supplying power to the electricity supply grid on June 2,2007, reaching full power on June 8
37.
Advanced boiling water reactor
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The advanced boiling water reactor is a Generation III boiling water reactor. The ABWR is currently offered by GE Hitachi Nuclear Energy and Toshiba, the ABWR generates electrical power by using steam to power a turbine connected to a generator, the steam is boiled from water using heat generated by fission reactions within nuclear fuel. The ABWR is the present state of the art in boiling water reactors, the first reactors were built on time and under budget in Japan, with others under construction there and in Taiwan. ABWRs are on order in the United States, including two reactors at the South Texas Project site, the standard ABWR plant design has a net electrical output of about 1.35 GW. The ABWR represents an evolutionary route for the BWR family, with numerous changes, only the RIP motor is located outside of the RPV in the ABWR. According to the Tier 1 Design Control Document, each RIP has a capacity of 6912 m3/h.80 s from receipt of an initiating signal, or ARI in a greater. The FMCRD also improves defense-in-depth in the event of primary hydraulic, a fully digital Reactor Protection System ensures a high level of reliability and simplification for safety condition detection and response. This system initiates rapid hydraulic insertion of control rods for shutdown when needed, two-out-of-four per parameter rapid shutdown logic ensures that nuisance rapid shutdowns are not triggered by single instrument failures. RPS can also trigger ARI, FMCRD rod run-in to shut down the chain reaction. The standby liquid control system actuation is provided as diverse logic in the event of an Anticipated Transient Without Scram. Fully digital reactor controls allow the room to easily and rapidly control plant operations. Separate redundant safety and non-safety related digital multiplexing buses allow for reliability and diversity of instrumentation, in particular, the reactor is automated for startup and for standard shutdown using automatic systems only. The Emergency Core Cooling System has been improved in areas, providing a very high level of defense-in-depth against accidents, contingencies. Previous BWRs had 2 divisions, and uncovery was predicted to occur for a time in the event of a severe accident. There exists an extremely thick basaltic reinforced concrete pad under the RPV that will catch and hold any heated core melt that might fall on that pad in extraordinarily contingent situations. The containment has been improved over the conventional Mark I type. This will keep containment pressure low, notably, the typical ABWR containment has numerous hardened layers between the interior of the primary containment and the outer shield wall, and is cubical in shape. One major enhancement is that the reactor has a standard safe shutdown earthquake acceleration of. 3G, further, seismic hardening is possible in earthquake-prone areas and has been done at the Lungmen facility in Taiwan which has been hardened up 0.4 g in any direction
38.
Borax
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Soid Borax, also known as sodium borate, sodium tetraborate, or disodium tetraborate, is an important boron compound, a mineral, and a salt of boric acid. Powdered borax is white, consisting of colorless crystals that dissolve easily in water. Borax has a variety of uses. It is a component of many detergents, cosmetics, and enamel glazes, in artisanal gold mining, the borax method is sometimes used as a substitute for toxic mercury in the gold extraction process. Borax was reportedly used by miners in parts of the Philippines in the 1900s. The term borax is used for a number of closely related minerals or chemical compounds that differ in their water content. Commercially sold borax is partially dehydrated, Borax was first discovered in dry lake beds in Tibet and was imported via the Silk Road to the Arabian Peninsula in the 8th Century AD. However, it is formulated as Na2·8H2O, since borax contains the 2− ion. In this structure, there are two four-coordinate boron atoms and two boron atoms. Borax is also converted to boric acid and other borates. When borax is added to a flame, it produces a green color. Borax is not used for purpose in fireworks due to the overwhelming yellow color of sodium. Boric acid is used to color methanol flames a transparent green, the English word borax is Latinized, the Middle English form was boras, from Old French boras, bourras. That may have been from medieval Latin baurach, borac, borax, or maybe directly from the Arabic, along with Spanish borrax and Italian borrace, the Arabic was بورق bauraq/bwrk, a word also used for borax. Traditional Arabic dictionaries say that it derives from the verb to glisten, which is also written بورق bwrq, but it seems to actually derive from the Persian būrah. The word borax is found in Arabic būraq, meaning white, which is from Middle Persian bwrk, another name for borax is tincal, from Sanskrit. The word tincal /ˈtɪŋkəl/ tinkle, or tincar /ˈtɪŋkər/ tinker, refers to crude borax, before it is purified, as mined from deposits in Tibet, Persia. The word was adopted in the 17th century from Malay tingkal and from Urdu/Persian/Arabic تنکار tinkār/tankār and these all appear to be related to the Sanskrit टांकण ṭānkaṇa
39.
Nuclear Regulatory Commission
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The Nuclear Regulatory Commission is an independent agency of the United States government tasked with protecting public health and safety related to nuclear energy. Established by the Energy Reorganization Act of 1974, the NRC began operations on January 19,1975 as one of two agencies to the United States Atomic Energy Commission. Prior to 1975 the Atomic Energy Commission was in charge of matters regarding radionuclides, the AEC was dissolved, because it was perceived as unduly favoring the industry it was charged with regulating. The NRC was formed as an independent commission to oversee nuclear energy matters, oversight of nuclear medicine, the U. S. AEC became the Energy Research and Development Administration in 1975, responsible for development and oversight of nuclear weapons. In 1977, ERDA became the United States Department of Energy, in 2000, the National Nuclear Security Administration was created as a subcomponent of DOE, responsible for nuclear weapons. Has, in critical areas, abdicated its role as a regulator altogether. To cite three examples, A1986 Congressional report found that NRC staff had provided valuable assistance to the utility seeking an operating license for the controversial Seabrook plant. The origins and development of NRC regulatory processes and policies are explained in five volumes of published by the University of California Press. These are, Controlling the Atom, The Beginnings of Nuclear Regulation 1946–1962, containing the Atom, Nuclear Regulation in a Changing Environment, 1963–1971. The NRC has produced a booklet, A Short History of Nuclear Regulation 1946–2009. Thomas Wellock, an academic, is the NRC historian. Before joining the NRC, Wellock wrote Critical Masses, Opposition to Nuclear Power in California, the NRC is headed by five Commissioners appointed by the President of the United States and confirmed by the United States Senate for five-year terms. One of them is designated by the President to be the Chairman, the current chairman is Kristine Svinicki. President Donald Trump designated Ms. Svinicki as Chairman of the NRC effective Jan, the NRC consists of the Commission on the one hand and offices of the Executive Director for Operations on the other. The Commission is divided into two committees and one Board, the Atomic Safety and Licensing Board Panel, as well as 8 commission staff offices, of these operations offices, NRCs major program components are the first five offices mentioned above. NRCs proposed FY2015 budget is $1,059.5 million and this is an increase of $3.6 million, including 65.1 FTE, compared to FY2014. NRC headquarters offices are located in unincorporated North Bethesda, Maryland, region I, located in King of Prussia, Pennsylvania, oversees the northeastern states. Region II, located in Atlanta, Georgia, oversees most of the southeastern states, region III, located in Lisle, Illinois, oversees the Midwest
40.
Economic Simplified Boiling Water Reactor
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All are designs by GE Hitachi Nuclear Energy, and are based on previous Boiling Water Reactor designs. The passive safety systems in an ESBWR operate without using any pumps, which creates increased design safety, integrity, there are no circulation pumps or associated piping, power supplies, heat exchangers, instrumentation, or controls needed for these systems. In events where the reactor coolant pressure boundary remains intact, the Isolation Condenser System is used to remove heat from the reactor. The ICS system is a loop system that connects the reactor pressure vessel to a heat exchanger located in the upper elevation of the reactor building. Steam leaves the reactor through the ICS piping and travels to the ICS heat exchangers which are submerged in a large pool, the steam is condensed in the heat exchangers and the denser condensate then flows back down to the reactor to complete the cooling loop. Reactor coolant is cycled through this path to provide continuous cooling. If the water level inside the pressure vessel drops to a predetermined level, due to the loss of water inventory, the reactor is depressurized. It consists of pools of water inside containment located above the reactor that are connected to the reactor pressure vessel. When the GDCS system is initiated, gravity forces water to flow from the pools into the reactor, the pools are sized to provide sufficient amounts of water to maintain the water at a level above the top of the nuclear fuel. The PCCS consists of a set of heat exchangers located in the portion of the reactor building. The steam from the reactor rises through the containment to the PCCS heat exchangers where the steam is condensed, the condensate then drains from the PCCS heat exchangers back to the GDCS pools where it completes the cycle and drains back to the reactor pressure vessel. Both the ICS and PCCS heat exchangers are submerged in a pool of water enough to provide 72 hours of reactor decay heat removal capability. The pool is vented to the atmosphere and is located outside of the containment, the combination of these features allows the pool to be refilled easily with low pressure water sources and installed piping. The reactor core is shorter than in conventional BWR plants to reduce the pressure drop over the fuel, there are 1,132 fuel rod bundles and the thermal power is 4,500 MWth in the standardized SBWR. The nominal output is rated at 1594 MWe gross and 1535 MWe net, in case of an accident, the ESBWR can remain in a safe, stable state for 72 hours without any operator action or even electrical power. Below the vessel, there is a structure that allows for cooling of the core during any very severe accident. These pipes facilitate cooling above and below the core with water. The final safety evaluation report accepted by the NRC reports an overall core damage frequency of 1.65 * 10−8 per year, the ESBWR received a positive Safety Evaluation Report and Final Design Approval on March 9,2011
41.
MWt
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The watt is a derived unit of power in the International System of Units defined as 1 joule per second and can be used to quantify the rate of energy transfer. Power has dimensions of M L2 T −3, when an objects velocity is held constant at one meter per second against constant opposing force of one newton the rate at which work is done is 1 watt. 1 W =1 V ⋅ A Two additional unit conversions for watt can be using the above equation. 1 W =1 V2 Ω =1 A2 ⋅ Ω Where ohm is the SI derived unit of electrical resistance, a person having a mass of 100 kilograms who climbs a 3-meter-high ladder in 5 seconds is doing work at a rate of about 600 watts. Mass times acceleration due to gravity times height divided by the time it takes to lift the object to the given height gives the rate of doing work or power. A laborer over the course of an 8-hour day can sustain an output of about 75 watts, higher power levels can be achieved for short intervals. The watt is named after the Scottish scientist James Watt for his contributions to the development of the steam engine, in 1960 the 11th General Conference on Weights and Measures adopted it for the measurement of power into the International System of Units. For additional examples of magnitude for multiples and submultiples of the watt, technologically important powers that are measured in femtowatts are typically found in reference to radio and radar receivers. For example, meaningful FM tuner performance figures for sensitivity, quieting and these input levels are often stated in dBf. This is 0.2739 microvolt across a 75-ohm load or 0.5477 microvolt across a 300-ohm load, the picowatt is equal to one trillionth of a watt. Technologically important powers that are measured in picowatts are typically used in reference to radio and radar receivers, acoustics, the nanowatt is equal to one billionth of a watt. Important powers that are measured in nanowatts are also used in reference to radio. The microwatt is equal to one millionth of a watt, compact solar cells for devices such as calculators and watches are typically measured in microwatts. The milliwatt is equal to one thousandth of a watt, a typical laser pointer outputs about five milliwatts of light power, whereas a typical hearing aid for people uses less than one milliwatt. Audio signals and other electronic signal levels are measured in dBm. The kilowatt is equal to one thousand watts and this unit is typically used to express the output power of engines and the power of electric motors, tools, machines, and heaters. It is also a unit used to express the electromagnetic power output of broadcast radio. One kilowatt is equal to 1.34 horsepower
42.
ABWR
–
The advanced boiling water reactor is a Generation III boiling water reactor. The ABWR is currently offered by GE Hitachi Nuclear Energy and Toshiba, the ABWR generates electrical power by using steam to power a turbine connected to a generator, the steam is boiled from water using heat generated by fission reactions within nuclear fuel. The ABWR is the present state of the art in boiling water reactors, the first reactors were built on time and under budget in Japan, with others under construction there and in Taiwan. ABWRs are on order in the United States, including two reactors at the South Texas Project site, the standard ABWR plant design has a net electrical output of about 1.35 GW. The ABWR represents an evolutionary route for the BWR family, with numerous changes, only the RIP motor is located outside of the RPV in the ABWR. According to the Tier 1 Design Control Document, each RIP has a capacity of 6912 m3/h.80 s from receipt of an initiating signal, or ARI in a greater. The FMCRD also improves defense-in-depth in the event of primary hydraulic, a fully digital Reactor Protection System ensures a high level of reliability and simplification for safety condition detection and response. This system initiates rapid hydraulic insertion of control rods for shutdown when needed, two-out-of-four per parameter rapid shutdown logic ensures that nuisance rapid shutdowns are not triggered by single instrument failures. RPS can also trigger ARI, FMCRD rod run-in to shut down the chain reaction. The standby liquid control system actuation is provided as diverse logic in the event of an Anticipated Transient Without Scram. Fully digital reactor controls allow the room to easily and rapidly control plant operations. Separate redundant safety and non-safety related digital multiplexing buses allow for reliability and diversity of instrumentation, in particular, the reactor is automated for startup and for standard shutdown using automatic systems only. The Emergency Core Cooling System has been improved in areas, providing a very high level of defense-in-depth against accidents, contingencies. Previous BWRs had 2 divisions, and uncovery was predicted to occur for a time in the event of a severe accident. There exists an extremely thick basaltic reinforced concrete pad under the RPV that will catch and hold any heated core melt that might fall on that pad in extraordinarily contingent situations. The containment has been improved over the conventional Mark I type. This will keep containment pressure low, notably, the typical ABWR containment has numerous hardened layers between the interior of the primary containment and the outer shield wall, and is cubical in shape. One major enhancement is that the reactor has a standard safe shutdown earthquake acceleration of. 3G, further, seismic hardening is possible in earthquake-prone areas and has been done at the Lungmen facility in Taiwan which has been hardened up 0.4 g in any direction
43.
Nuclear reactor safety system
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This article covers the technical aspects of active nuclear safety systems in the United States. For a general approach to safety, see nuclear safety. The three primary objectives of nuclear safety systems as defined by the U. S. Nuclear Regulatory Commission are to shut down the reactor, maintain it in a shutdown condition, a reactor protection system is designed to immediately terminate the nuclear reaction. By breaking the chain reaction, the source of heat is eliminated, other systems can then be used to remove decay heat from the core. All nuclear plants have some form of reactor protection system, control rods are a series of rods that can be quickly inserted into the reactor core to absorb neutrons and rapidly terminate the nuclear reaction. They are typically composed of actinides, lanthanides, transition metals, boiling water reactors are able to scram the reactor completely with the help of their control rods. In the case of a Loss of coolant accident, the water-loss of the cooling system can be compensated with normal water pumped into the cooling circuit. Pressurized water reactors on the hand have to use boron solution in addition to the control rods to shut down the reactor. In the case of problems with the rods, they are able to increase the normal concentration of boron in the coolant water rapidly. In the case of LOCA, PWRs flood the core with water that contains further boron. The essential service water system circulates the water cools the plant’s heat exchangers. Because this includes cooling the systems that remove decay heat from both the system and the spent fuel rod cooling ponds, the ESWS is a safety-critical system. Since the water is drawn from an adjacent river, the sea, or other large body of water. In locations without a body of water in which to dissipate the heat. Emergency core cooling systems are designed to shut down a nuclear reactor during accident conditions. The ECCS allows the plant to respond to a variety of accident conditions, 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. It is designed to monitor the level of coolant in the reactor vessel and 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
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Boric acid
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It has the chemical formula H3BO3, and exists in the form of colorless crystals or a white powder that dissolves in water. When occurring as a mineral, it is called sassolite, Boric acid, or sassolite, is found mainly in its free state in some volcanic districts, for example, in the Italian region of Tuscany, the Lipari Islands and the US state of Nevada. In these volcanic settings it issues, mixed with steam, from fissures in the ground and it is also found as a constituent of many naturally occurring minerals – borax, boracite, ulexite and colemanite. Boric acid and its salts are found in seawater and it is also found in plants, including almost all fruits. Boric acid was first prepared by Wilhelm Homberg from borax, by the action of mineral acids, however borates, including boric acid, have been used since the time of the Greeks for cleaning, preserving food, and other activities. When heated above 170 °C, it dehydrates, forming metaboric acid, H3BO3 → HBO2 + H2O Metaboric acid is a white, further heating leads to boron trioxide. H2B4O7 →2 B2O3 + H2O There are conflicting interpretations for the origin of the acidity of aqueous boric acid solutions, polyborate anions are formed at pH 7–10 if the boron concentration is higher than about 0.025 mol/L. The best known of these is the ion, found in the mineral borax. With polyols such as glycerol and mannitol the acidity of the solution is increased, with mannitol for example the pK decreases to 5.15. This is due to the formation of a chelate, −, Boric acid dissolves in anhydrous sulfuric acid, B3 + 6H2SO4 → 3H3O+ + 2HSO4− + B4− Boric acid reacts with alcohols to form borate esters, B3 where R is alkyl or aryl. A dehydrating agent, such as concentrated sulfuric acid is typically added, the B-O bond length is 136 pm and the O-H is 97 pm. The molecular point group is C3h, crystalline boric acid consists of layers of B3 molecules held together by hydrogen bonds of length 272 pm. The distance between two adjacent layers is 318 pm, based on mammalian median lethal dose rating of 2,660 mg/kg body mass, boric acid is only poisonous if taken internally or inhaled in large quantities. The Fourteenth Edition of the Merck Index indicates that the LD50 of boric acid is 5.14 g/kg for oral dosages given to rats, for comparisons sake, the LD50 of salt is reported to be 3.75 g/kg in rats according to the Merck Index. Humans have been known to die from amounts only a fraction of the LD50. Long term exposure to acid may be of more concern, causing kidney damage. Although it does not appear to be carcinogenic, studies in dogs have reported testicular atrophy after exposure to 32 mg/kg bw/day for 90 days and this level is far lower than the LD50. As a consequence, in August 2008, in the 30th ATP to EU directive 67/548/EEC, textile fiberglass is used to reinforce plastics in applications that range from boats, to industrial piping to computer circuit boards
