|
Core Shroud
A core shroud is a stainless steel cylinder surrounding a nuclear reactor core whose main function is to direct the cooling water flow. The nuclear reactor core is where the nuclear reactions take place. Because the reactions are exothermic, cool water is needed to prevent the reactor core from melting down. The core shroud helps by directing this cool water towards the reactor core, providing stability to the nuclear reactions. Structure The core shroud is composed of multiple cylindrical heat shield, thermal shields stacked on top of each other. In between each thermal shield is a horizontal, stainless steel cylindrical plate that helps keep the thermal shields in place. The plates are then welded together with the thermal shields so that they create one solid structure. rail fastening system, Vertical tie bolts are then used to reinforce each horizontal plate with their adjacent thermal shields, stabilizing the cylindrical core shroud. The thermal shields are needed because th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nuclear Reactor Core
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. The core also contains structural components, the means to both moderate the neutrons and control the reaction, and the means to transfer the heat from the fuel to where it is required, outside the core. Water-moderated reactors Inside the core of a typical pressurized water reactor or boiling water reactor are fuel rods with a diameter of a large gel-type ink pen, each about 4 m long, which 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. 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 lowe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nuclear Reaction
In nuclear physics and nuclear chemistry, a nuclear reaction is a process in which two atomic nucleus, nuclei, or a nucleus and an external subatomic particle, collide to produce one or more new nuclides. Thus, a nuclear reaction must cause a transformation of at least one nuclide to another. If a nucleus interacts with another nucleus or particle and they then separate without changing the nature of any nuclide, the process is simply referred to as a type of nuclear scattering, rather than a nuclear reaction. In principle, a reaction can involve more than two particles collision, colliding, but because the probability of three or more nuclei to meet at the same time at the same place is much less than for two nuclei, such an event is exceptionally rare (see triple alpha process for an example very close to a three-body nuclear reaction). The term "nuclear reaction" may refer either to a change in a nuclide induced by collision with another particle or to a spontaneous change of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Exothermic
In thermodynamics, an exothermic process () is a thermodynamic process or reaction that releases energy from the system to its surroundings, usually in the form of heat, but also in a form of light (e.g. a spark, flame, or flash), electricity (e.g. a battery), or sound (e.g. explosion heard when burning hydrogen). The term ''exothermic'' was first coined by 19th-century French chemist Marcellin Berthelot. The opposite of an exothermic process is an endothermic process, one that absorbs energy usually in the form of heat. The concept is frequently applied in the physical sciences to chemical reactions where chemical bond energy is converted to thermal energy (heat). Two types of chemical reactions Exothermic and endothermic describe two types of chemical reactions or systems found in nature, as follows: Exothermic After an exothermic reaction, more energy has been released to the surroundings than was absorbed to initiate and maintain the reaction. An example would be the burn ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Heat Shield
In thermodynamics, heat is defined as the form of energy crossing the boundary of a thermodynamic system by virtue of a temperature difference across the boundary. A thermodynamic system does not ''contain'' heat. Nevertheless, the term is also often used to refer to the thermal energy contained in a system as a component of its internal energy and that is reflected in the temperature of the system. For both uses of the term, heat is a form of energy. An example of formal vs. informal usage may be obtained from the right-hand photo, in which the metal bar is "conducting heat" from its hot end to its cold end, but if the metal bar is considered a thermodynamic system, then the energy flowing within the metal bar is called internal energy, not heat. The hot metal bar is also transferring heat to its surroundings, a correct statement for both the strict and loose meanings of ''heat''. Another example of informal usage is the term '' heat content'', used despite the fact that p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rail Fastening System
A rail fastening system is a means of fixing rails to railroad ties (North America) or sleepers (British Isles, Australasia, and Africa). The terms ''rail anchors'', ''tie plates'', ''chairs'' and ''track fasteners'' are used to refer to parts or all of a rail fastening system. The components of a rail fastening system may also be known collectively as other track material, or OTM for short. Various types of fastening have been used over the years. History and overview The earliest wooden rails were fixed to wooden sleepers by pegs through holes in the rail, or by nails. By the 18th century, cast iron rails had come into use, and also had holes in the rail itself to allow them to be fixed to a support. 18th century developments such as the flanged rail and fish bellied rail also had holes in the rail itself; when stone block sleepers were used the nails were driven into a wooden block which had been inserted into a recess in the block. The first chair for a rail is thought to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nuclear Fuel
Nuclear fuel is material 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 actinide elements that are capable of undergoing and sustaining nuclear fission. The three most relevant fissile isotopes are uranium-233, uranium-235 and plutonium-239. When the unstable nuclei of these atoms are hit by a slow-moving neutron, they frequently split, creating two daughter nuclei and two or three more neutrons. In that case, the neutrons released go on to split more nuclei. This creates a self-sustaining chain reaction that is controlled in a nuclear reactor, or uncontrolled in a nuclear weapon. Alternatively, if the nucleus absorbs the neutron without splitting, it creates a heavier nucleus with one additional neutron. The processes involved in mining, refining, purifying, using, and disposing of nuclear fuel are collectively known as the nuclear fuel cycle. Not all typ ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Steam Turbine
A steam turbine is a machine that extracts thermal energy from pressurized steam and uses it to do mechanical work on a rotating output shaft. Its modern manifestation was invented by Charles Parsons in 1884. Fabrication of a modern steam turbine involves advanced metalwork to form high-grade steel alloys into precision parts using technologies that first became available in the 20th century; continued advances in durability and efficiency of steam turbines remains central to the energy economics of the 21st century. The steam turbine is a form of heat engine that derives much of its improvement in thermodynamic efficiency from the use of multiple stages in the expansion of the steam, which results in a closer approach to the ideal reversible expansion process. Because the turbine generates rotary motion, it can be coupled to a generator to harness its motion into electricity. Such turbogenerators are the core of thermal power stations which can be fueled by fossil-fuels, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Stress Corrosion Cracking
Stress corrosion cracking (SCC) is the growth of crack formation in a corrosive environment. It can lead to unexpected and sudden failure of normally ductile metal alloys subjected to a tensile stress, especially at elevated temperature. SCC is highly chemically specific in that certain alloys are likely to undergo SCC only when exposed to a small number of chemical environments. The chemical environment that causes SCC for a given alloy is often one which is only mildly corrosive to the metal. Hence, metal parts with severe SCC can appear bright and shiny, while being filled with microscopic cracks. This factor makes it common for SCC to go undetected prior to failure. SCC often progresses rapidly, and is more common among alloys than pure metals. The specific environment is of crucial importance, and only very small concentrations of certain highly active chemicals are needed to produce catastrophic cracking, often leading to devastating and unexpected failure.ASM Internation ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nuclear Meltdown
A nuclear meltdown (core meltdown, core melt accident, meltdown or partial core melt) is a severe nuclear reactor accident that results in core damage from overheating. The term ''nuclear meltdown'' is not officially defined by the International Atomic Energy Agency or by the United States Nuclear Regulatory Commission. It has been defined to mean the accidental melting of the core of a nuclear reactor, however, and is in common usage a reference to the core's either complete or partial collapse. A core meltdown accident occurs when the heat generated by a nuclear reactor exceeds the heat removed by the cooling systems to the point where at least one nuclear fuel element exceeds its melting point. This differs from a fuel element failure, which is not caused by high temperatures. A meltdown may be caused by a loss of coolant, loss of coolant pressure, or low coolant flow rate or be the result of a criticality excursion in which the reactor is operated at a power level that exc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Anchor Bolt
Anchor bolts are used to connect structural and non-structural elements to concrete.. The connection can be made by a variety of different components: anchor bolts (also named fasteners), steel plates, or stiffeners. Anchor bolts transfer different types of load: tension forces and shear forces. A connection between structural elements can be represented by steel columns attached to a reinforced concrete foundation. A common case of a non-structural element attached to a structural one is the connection between a facade system and a reinforced concrete wall. Types Cast-in-place The simplest – and strongest – form of anchor bolt is cast-in-place, with its embedded end consisting of a standard hexagonal head bolt and washer, 90-bend, or some sort of forged or welded flange (see also stud welding). The last are used in concrete-steel composite structures as shear connectors. Other uses include anchoring machines to poured concrete floors and buildings to their c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fukushima Daiichi Nuclear Disaster
The was a nuclear accident in 2011 at the Fukushima Daiichi Nuclear Power Plant in Ōkuma, Fukushima, Japan. The proximate cause of the disaster was the 2011 Tōhoku earthquake and tsunami, which occurred on the afternoon of 11 March 2011 and remains the most powerful earthquake ever recorded in Japan. The earthquake triggered a powerful tsunami, with 13–14-meter-high waves damaging the nuclear power plant's emergency diesel generators, leading to a loss of electric power. The result was the most severe nuclear accident since the Chernobyl disaster in 1986, classified as level seven on the International Nuclear Event Scale (INES) after initially being classified as level five, and thus joining Chernobyl as the only other accident to receive such classification. While the 1957 explosion at the Mayak facility was the second worst by radioactivity released, the INES ranks incidents by impact on population, so Chernobyl (335,000 people evacuated) and Fukushima (154,000 evacuate ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
