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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, however it has been defined to mean the accidental melting of the core or fuel of a nuclear reactor, 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's power level exceeds its design limits. Once the fuel elements of a reactor b ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fukushima I By Digital Globe
may refer to: Japan * Fukushima Prefecture, Japanese prefecture **Fukushima, Fukushima, capital city of Fukushima Prefecture, Japan *** Fukushima University, national university in Japan ***Fukushima Station (Fukushima) in Fukushima, Fukushima ** Fukushima Airport, airport serving northern and central Fukushima Prefecture, Japan **Fukushima Daini Nuclear Power Plant, another nuclear power plant in Fukushima Prefecture, Japan. Now being decommissioned **Fukushima Daiichi Nuclear Power Plant, a disabled nuclear power plant in Fukushima Prefecture, Japan *** Fukushima Daiichi nuclear accident, 2011 nuclear accident at the Fukushima nuclear power plant, Japan *** Fukushima disaster cleanup, clean-up activities following the nuclear accidents, Fukushima, Japan ** 2016 Fukushima earthquake ** 2021 Fukushima earthquake Hokkaido *Fukushima, Hokkaido Osaka *Fukushima-ku, Osaka, ward * Fukushima Station Nagano Prefecture *Kiso-Fukushima Station *Fukushima-juku, former post to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Caesium-137
Caesium-137 (), cesium-137 (US), or radiocaesium, is a radioactive isotope of caesium that is formed as one of the more common fission products by the nuclear fission of uranium-235 and other fissionable isotopes in nuclear reactors and nuclear weapons. Trace quantities also originate from spontaneous fission of uranium-238. It is among the most problematic of the short-to-medium-lifetime fission products. Caesium-137 has a relatively low boiling point of and easily becomes volatile when released suddenly at high temperature, as in the case of the Chernobyl nuclear accident and with atomic explosions, and can travel very long distances in the air. After being deposited onto the soil as radioactive fallout, it moves and spreads easily in the environment because of the high water solubility of caesium's most common chemical compounds, which are salts. Caesium-137 was discovered by Glenn T. Seaborg and Margaret Melhase. Decay Caesium-137 has a half-life of about 30.04 y ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Loss-of-pressure-control Accident
A loss-of-pressure-control accident (LOPA) is a mode of failure for a nuclear reactor that involves the pressure of the confined coolant falling below specification. Most commercial types of nuclear reactor use a pressure vessel to maintain pressure in the reactor plant. This is necessary in a pressurized water reactor to prevent boiling in the core, which could lead to a nuclear meltdown. This is also necessary in other types of reactor plants to prevent moderators from having uncontrolled properties. Pressure is controlled in a pressurized water reactor to ensure that the core itself does not reach its boiling point in which the water will turn into steam and rapidly decrease the heat being transferred from the fuel to the moderator. By a combination of heaters and spray valves, pressure is controlled in the pressurizer vessel which is connected to the reactor plant. Because the pressurizer vessel and the reactor plant are connected, the pressure of the steam space pressurizes ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Decay Heat
Decay heat is the heat released as a result of radioactive decay. This heat is produced as an effect of radiation on materials: the energy of the alpha particle, alpha, Beta particle, beta or gamma radiation is converted into the thermal movement of atoms. Decay heat occurs naturally from decay of long-lived radioisotopes that are primordially present from the Earth's formation. In nuclear reactor engineering, decay heat continues to be generated after the reactor has been shut down (see SCRAM and nuclear chain reactions) and power generation has been suspended. The decay of the short-lived radioisotopes such as iodine-131 created in fission continues at high power for a time after shutdown (nuclear reactor), shut down. The major source of heat production in a newly shut down reactor is due to the beta decay of new radioactive elements recently produced from fission fragments in the fission process. Quantitatively, at the moment of reactor shutdown, decay heat from these radioact ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Electrical Generator
In electricity generation, a generator, also called an ''electric generator'', ''electrical generator'', and ''electromagnetic generator'' is an electromechanical device that converts mechanical energy to electrical energy for use in an external circuit. In most generators which are rotating machines, a source of kinetic power rotates the generator's shaft, and the generator produces an electric current at its output terminals which flows through an external circuit, powering electrical loads. Sources of mechanical energy used to drive generators include steam turbines, gas turbines, water turbines, internal combustion engines, wind turbines and even hand cranks. Generators produce nearly all of the electric power for worldwide electric power grids. The first electromagnetic generator, the Faraday disk, was invented in 1831 by British scientist Michael Faraday. The reverse conversion of electrical energy into mechanical energy is done by an electric motor, and motors a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Radiation Poisoning
Acute radiation syndrome (ARS), also known as radiation sickness or radiation poisoning, is a collection of health effects that are caused by being exposed to high amounts of ionizing radiation in a short period of time. Symptoms can start within an hour of exposure, and can last for several months. Early symptoms are usually nausea, vomiting and loss of appetite. In the following hours or weeks, initial symptoms may appear to improve, before the development of additional symptoms, after which either recovery or death follows. ARS involves a total dose of greater than 0.7 Gy (70 rad), that generally occurs from a source outside the body, delivered within a few minutes. Sources of such radiation can occur accidentally or intentionally. They may involve nuclear reactors, cyclotrons, certain devices used in cancer therapy, nuclear weapons, or radiological weapons. It is generally divided into three types: bone marrow, gastrointestinal, and neurovascular syndrome, with bone m ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Radioactive Fallout
Nuclear fallout is residual radioactive material that is created by the reactions producing a nuclear explosion. It is initially present in the radioactive cloud created by the explosion, and "falls out" of the cloud as it is moved by the atmosphere in the minutes, hours, and days after the explosion. The bulk of the radioactivity from nuclear fallout comes from fission products, which are created by the nuclear fission reactions of the nuclear device. Un-fissioned bomb fuel (such as plutonium and uranium), and radioactive isotopes created by neutron activation, make up a smaller amount of the radioactive content of fallout. The amount of fallout and its distribution is dependent on several factors, including the overall yield of the weapon, the fission yield of the weapon, the height of burst of the weapon, and meteorological conditions. Fallout can have serious human health consequences on both short- and long-term time scales, and can cause radioactive contamination far aw ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Radioactive Contamination
Radioactive contamination, also called radiological pollution, is the deposition of, or presence of Radioactive decay, radioactive substances on surfaces or within solids, liquids, or gases (including the human body), where their presence is unintended or undesirable (from the International Atomic Energy Agency (IAEA) definition). Such contamination presents a hazard because the radioactive decay of the contaminants produces ionizing radiation (namely alpha particle, alpha, beta particle, beta, gamma rays and free neutrons). The degree of hazard is determined by the concentration of the contaminants, the energy of the radiation being emitted, the type of radiation, and the proximity of the contamination to organs of the body. It is important to be clear that the contamination gives rise to the radiation hazard, and the terms "radiation" and "contamination" are not interchangeable. The sources of radioactive pollution can be classified into two groups: natural and man-made. Follo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Radioactive Material
A radionuclide (radioactive nuclide, radioisotope or radioactive isotope) is a nuclide that has excess numbers of either neutrons or protons, giving it excess nuclear energy, and making it unstable. This excess energy can be used in one of three ways: emitted from the nucleus as gamma radiation; transferred to one of its electrons to release it as a Internal conversion, conversion electron; or used to create and emit a new particle (alpha particle or beta particle) from the nucleus. During those processes, the radionuclide is said to undergo radioactive decay. These emissions are considered ionizing radiation because they are energetic enough to liberate an electron from another atom. The radioactive decay can produce a stable nuclide or will sometimes produce a new unstable radionuclide which may undergo further decay. Radioactive decay is a random process at the level of single atoms: it is impossible to predict when one particular atom will decay. However, for a collection of at ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Water Hammer
Hydraulic shock ( colloquial: water hammer; fluid hammer) is a pressure surge or wave caused when a fluid in motion is forced to stop or change direction suddenly: a momentum change. It is usually observed in a liquid but gases can also be affected. This phenomenon commonly occurs when a valve closes suddenly at an end of a pipeline system and a pressure wave propagates in the pipe. This pressure wave can cause major problems, from noise and vibration to pipe rupture or collapse. It is possible to reduce the effects of the water hammer pulses with accumulators, expansion tanks, surge tanks, blowoff valves, and other features. The effects can be avoided by ensuring that no valves will close too quickly with significant flow, but there are many situations that can cause the effect. Rough calculations can be made using the Zhukovsky (Joukowsky) equation, or more accurate ones using the method of characteristics. History In the 1st century B.C., Marcus Vitruvius Pollio ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hydrogen Explosion
Hydrogen safety covers the safe production, handling and use of hydrogen, particularly hydrogen gas fuel and liquid hydrogen. Hydrogen possesses the NFPA 704's highest rating of four on the flammability scale because it is flammable when mixed even in small amounts with ordinary air. Ignition can occur at a volumetric ratio of hydrogen to air as low as 4% due to the oxygen in the air and the simplicity and chemical properties of the reaction. However, hydrogen has no rating for innate hazard for reactivity or toxicity. The storage and use of hydrogen poses unique challenges due to its ease of leaking as a gaseous fuel, low-energy ignition, wide range of combustible fuel-air mixtures, buoyancy, and its ability to embrittle metals that must be accounted for to ensure safe operation. Liquid hydrogen poses additional challenges due to its increased density and the extremely low temperatures needed to keep it in liquid form. Moreover, its demand and use in industry—as rocket fuel, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fuel-coolant Interaction
A steam explosion is an explosion caused by violent boiling or flashing of water or ice into steam, occurring when water or ice is either superheated, rapidly heated by fine hot debris produced within it, or heated by the interaction of molten metals (as in a fuel–coolant interaction, or FCI, of molten nuclear-reactor fuel rods with water in a nuclear reactor core following a core-meltdown). Steam explosions are instances of explosive boiling. Pressure vessels, such as pressurized water (nuclear) reactors, that operate above atmospheric pressure can also provide the conditions for a steam explosion. The water changes from a solid or liquid to a gas with extreme speed, increasing dramatically in volume. A steam explosion sprays steam and boiling-hot water and the hot medium that heated it in all directions (if not otherwise confined, e.g. by the walls of a container), creating a danger of scalding and burning. Steam explosions are not normally chemical explosions, although a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
