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Plasma-facing Material
In nuclear fusion power research, the plasma-facing material (or materials) (PFM) is any material used to construct the plasma-facing components (PFC), those components exposed to the plasma within which nuclear fusion occurs, and particularly the material used for the lining the first wall or divertor region of the reactor vessel. Plasma-facing materials for fusion reactor designs must support the overall steps for energy generation, these include: #Generating heat through fusion, #Capturing heat in the first wall, #Transferring heat at a faster rate than capturing heat. #Generating electricity. In addition PFMs have to operate over the lifetime of a fusion reactor vessel by handling the harsh environmental conditions, such as: # Ion bombardment causing physical and chemical sputtering and therefore erosion. # Ion implantation causing displacement damage and chemical composition changes # High-heat fluxes (e.g. 10 MW/m^2) due to ELMS and other transients. # Limited tritium code ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Alcator C-Mod Tokamak Interior
Alcator C-Mod was a tokamak (a type of magnetically confined fusion device) that operated between 1991 and 2016 at the Massachusetts Institute of Technology (MIT) Plasma Science and Fusion Center (PSFC). Notable for its high toroidal magnetic field (of up to 8 Tesla), Alcator C-Mod holds the world record for volume averaged plasma pressure in a magnetically confined fusion device. Until its shutdown in 2016, it was one of the major fusion research facilities in the United States. Alcator C-Mod was the third of the Alcator (''Alto Campo Toro'', High Field Torus) tokamak series, following Alcator A (1973–1979) and Alcator C (1978–1987). It was the largest fusion reactor operated by any university and was an integral part of the larger Plasma Science and Fusion Center. History Alcator A In the late 1960s, magnetic-confinement fusion research at MIT was carried out on small-scale "table-top" experiments at the Research Laboratory for Electronics and the Francis Bitte ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Magnetic Confinement
Magnetic confinement fusion is an approach to generate thermonuclear fusion power that uses magnetic fields to confine fusion fuel in the form of a plasma. Magnetic confinement is one of two major branches of fusion energy research, along with inertial confinement fusion. The magnetic approach began in the 1940s and absorbed the majority of subsequent development. Fusion reactions combine light atomic nuclei such as hydrogen to form heavier ones such as helium, producing energy. In order to overcome the electrostatic repulsion between the nuclei, they must have a temperature of tens of millions of degrees, creating a plasma. In addition, the plasma must be contained at a sufficient density for a sufficient time, as specified by the Lawson criterion (triple product). Magnetic confinement fusion attempts to use the electrical conductivity of the plasma to contain it through interaction with magnetic fields. The magnetic pressure offsets the plasma pressure. Developing a suitable ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Beryllium
Beryllium is a chemical element with the symbol Be and atomic number 4. It is a steel-gray, strong, lightweight and brittle alkaline earth metal. It is a divalent element that occurs naturally only in combination with other elements to form minerals. Notable gemstones high in beryllium include beryl ( aquamarine, emerald) and chrysoberyl. It is a relatively rare element in the universe, usually occurring as a product of the spallation of larger atomic nuclei that have collided with cosmic rays. Within the cores of stars, beryllium is depleted as it is fused into heavier elements. Beryllium constitutes about 0.0004 percent by mass of Earth's crust. The world's annual beryllium production of 220 tons is usually manufactured by extraction from the mineral beryl, a difficult process because beryllium bonds strongly to oxygen. In structural applications, the combination of high flexural rigidity, thermal stability, thermal conductivity and low density (1.85 times that of water) ma ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Carbon Fibre Composite
Carbon fiber-reinforced polymers (American English), carbon-fibre-reinforced polymers (Commonwealth English), carbon-fiber-reinforced plastics, carbon-fiber reinforced-thermoplastic (CFRP, CRP, CFRTP), also known as carbon fiber, carbon composite, or just carbon, are extremely strong and light fiber-reinforced plastics that contain carbon fibers. CFRPs can be expensive to produce, but are commonly used wherever high strength-to-weight ratio and stiffness (rigidity) are required, such as aerospace, superstructures of ships, automotive, civil engineering, sports equipment, and an increasing number of consumer and technical applications. The binding polymer is often a thermoset resin such as epoxy, but other thermoset or thermoplastic polymers, such as polyester, vinyl ester, or nylon, are sometimes used. The properties of the final CFRP product can be affected by the type of additives introduced to the binding matrix (resin). The most common additive is silica, but other additi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Graphite
Graphite () is a crystalline form of the element carbon. It consists of stacked layers of graphene. Graphite occurs naturally and is the most stable form of carbon under standard conditions. Synthetic and natural graphite are consumed on large scale (300 kton/year, in 1989) for uses in pencils, lubricants, and electrodes. Under high pressures and temperatures it converts to diamond. It is a weak conductor of heat and electricity. Types and varieties Natural graphite The principal types of natural graphite, each occurring in different types of ore deposits, are * Crystalline small flakes of graphite (or flake graphite) occurs as isolated, flat, plate-like particles with hexagonal edges if unbroken. When broken the edges can be irregular or angular; * Amorphous graphite: very fine flake graphite is sometimes called amorphous; * Lump graphite (or vein graphite) occurs in fissure veins or fractures and appears as massive platy intergrowths of fibrous or acicular crystalline ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Boron Carbide
Boron carbide (chemical formula approximately B4C) is an extremely hard boron–carbon ceramic, a 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 and diamond. History Boron carbide was discovered in the 19th century as a by-product of reactions involving metal borides, but its chemical formula was unknown. It was not until the 1930s that the chemical composition was estimated as B4C. Controversy remained as to whether or not the material had this exact 4:1 stoichiometry, as, in practice the material is always slightly carbon-deficient with regard to this formula, and X-ray crystallography shows that its structure is highly complex, with a mixture of C-B-C chains and B12 icosahedra. These features argued against a very simple exact B4C empirical formula. Because of the B12 structural unit, the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Silicon Carbide
Silicon carbide (SiC), also known as carborundum (), is a hard chemical compound containing silicon and carbon. A semiconductor, it occurs in nature as the extremely rare mineral moissanite, but has been mass-produced as a powder and crystal since 1893 for use as an abrasive. Grains of silicon carbide can be bonded together by sintering to form very hard ceramics that are widely used in applications requiring high endurance, such as car brakes, car clutches and ceramic plates in bulletproof vests. Large single crystals of silicon carbide can be grown by the Lely method and they can be cut into gems known as synthetic moissanite. Electronic applications of silicon carbide such as light-emitting diodes (LEDs) and Cat's whisker detector, detectors in early radios were first demonstrated around 1907. SiC is used in semiconductor electronics devices that operate at high temperatures or high voltages, or both. Natural occurrence Naturally occurring moissanite is found in only minut ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Divertor
In nuclear fusion power research, a divertor is a device within a tokamak or a stellarator that allows the online removal of waste material from the plasma while the reactor is still operating. This allows control over the buildup of fusion products in the fuel, and removes impurities in the plasma that have entered into it from the vessel lining. The divertor was initially introduced during the earliest studies of fusion power systems in the 1950s. It was realized early on that successful fusion would result in heavier ions being created and left in the fuel (the so-called "fusion ash"). These impurities were responsible for the loss of heat, and caused other effects that made it more difficult to keep the reaction going. The divertor was proposed as a solution to this problem. Operating on the same principle as a mass spectrometer, the plasma passes through the divertor region where heavier ions are flung out of the fuel mass by centrifugal force, colliding with some sort of ab ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Heat Flux
Heat flux or thermal flux, sometimes also referred to as ''heat flux density'', heat-flow density or ''heat flow rate intensity'' is a flow of energy per unit area per unit time. In SI its units are watts per square metre (W/m2). It has both a direction and a magnitude, and so it is a vector quantity. To define the heat flux at a certain point in space, one takes the limiting case where the size of the surface becomes infinitesimally small. Heat flux is often denoted \vec_\mathrm, the subscript specifying ''heat'' flux, as opposed to ''mass'' or ''momentum'' flux. Fourier's law is an important application of these concepts. Fourier's law For most solids in usual conditions, heat is transported mainly by conduction and the heat flux is adequately described by Fourier's law. Fourier's law in one dimension \phi_\text = -k \frac where k is the thermal conductivity. The negative sign shows that heat flux moves from higher temperature regions to lower temperature regions. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nuclear Decommissioning
Nuclear decommissioning is the process whereby a nuclear facility is dismantled to the point that it no longer requires measures for radiation protection. The presence of radioactive material necessitates processes that are potentially occupationally hazardous, expensive, time-intensive, and present environmental risks that must be addressed to ensure radioactive materials are either transported elsewhere for storage or stored on-site in a safe manner.Benjamin K. Sovacool. "A Critical Evaluation of Nuclear Power and Renewable Electricity in Asia", ''Journal of Contemporary Asia'', Vol. 40, No. 3, August 2010, p. 373. The challenge in nuclear decommissioning is not just technical, but also economical and social. Decommissioning is an administrative and technical process. It includes clean-up of radioactive materials and progressive demolition of the facility. Once a facility is fully decommissioned, no radiological danger should persist. The costs of decommissioning are gene ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nuclear Waste
Radioactive waste is a type of hazardous waste that contains radioactive material. Radioactive waste is a result of many activities, including nuclear medicine, nuclear research, nuclear power generation, rare-earth mining, and nuclear weapons reprocessing. The storage and disposal of radioactive waste is regulated by government agencies in order to protect human health and the environment. Radioactive waste is broadly classified into low-level waste (LLW), such as paper, rags, tools, clothing, which contain small amounts of mostly short-lived radioactivity, intermediate-level waste (ILW), which contains higher amounts of radioactivity and requires some shielding, and high-level waste (HLW), which is highly radioactive and hot due to decay heat, so requires cooling and shielding. In nuclear reprocessing plants about 96% of spent nuclear fuel is recycled back into uranium-based and mixed-oxide (MOX) fuels. The residual 4% is minor actinides and fission products the latter of wh ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Induced Radioactivity
Induced radioactivity, also called artificial radioactivity or man-made radioactivity, is the process of using radiation to make a previously stable material radioactive. The husband and wife team of Irène Joliot-Curie and Frédéric Joliot-Curie discovered induced radioactivity in 1934, and they shared the 1935 Nobel Prize in Chemistry for this discovery. Irène Curie began her research with her parents, Marie Curie and Pierre Curie, studying the natural radioactivity found in radioactive isotopes. Irene branched off from the Curies to study turning stable isotopes into radioactive isotopes by bombarding the stable material with alpha particles (denoted α). The Joliot-Curies showed that when lighter elements, such as boron and aluminium, were bombarded with α-particles, the lighter elements continued to emit radiation even after the α−source was removed. They showed that this radiation consisted of particles carrying one unit positive charge with mass equal to that of an el ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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