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Boiling Water Reactor Safety Systems
Boiling water reactor safety systems are nuclear safety systems constructed within boiling water reactors in order to prevent or mitigate environmental and health hazards in the event of accident or natural disaster. Like the pressurized water reactor, the BWR reactor core continues to produce heat from radioactive decay after the Nuclear fission, fission reactions have stopped, making a nuclear meltdown, core damage incident possible in the event that all safety systems have failed and the core does not receive coolant. Also like the pressurized water reactor, a boiling water reactor has a negative void coefficient, that is, the neutron (and the thermal) output of the reactor decreases as the proportion of steam to liquid water increases inside the reactor. However, unlike a pressurized water reactor which contains no steam in the reactor core, a sudden increase in BWR steam pressure (caused, for example, by the actuation of the main steam isolation valve (MSIV) from the react ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nuclear Safety Systems
The three primary objectives of nuclear reactor safety systems as defined by the U.S. Nuclear Regulatory Commission are to shut down the reactor, maintain it in a shutdown condition and prevent the release of radioactive material. Reactor protection system (RPS) A reactor protection system is designed to immediately terminate the nuclear reaction. By breaking the nuclear 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 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, and boron, in various alloys with structural backing such as steel. In addition to being neutron absorbent, the alloys used also are required to have at least a low coefficient of thermal expansion so tha ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Delayed Neutron
In nuclear engineering, a delayed neutron is a neutron released not immediately during a nuclear fission event, but shortly afterward—ranging from milliseconds to several minutes later. These neutrons are emitted by excited daughter nuclei of certain beta-decaying fission products. In contrast, prompt neutrons are emitted almost instantaneously—within about 10−14 seconds—at the moment of fission. During fission, a heavy nucleus splits into two smaller, neutron-rich fragments (fission products), releasing several free neutrons known as prompt neutrons. Many of these fission products are radioactive and typically undergo beta decay to reach more stable configurations. In a small subset of cases, the beta decay of a fission product results in a daughter nucleus in an excited state with enough energy to emit a neutron. This neutron, emitted shortly after fission but delayed due to the beta decay process, is called a delayed neutron. The delay in neutron emission arises from ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nuclear Poison
In applications such as nuclear reactors, a neutron poison (also called a neutron absorber or a nuclear poison) is a substance with a large neutron absorption cross-section. In such applications, absorbing neutrons is normally an undesirable effect. However, neutron-absorbing materials, also called poisons, are intentionally inserted into some types of reactors in order to lower the high reactivity of their initial fresh fuel load. Some of these poisons deplete as they absorb neutrons during reactor operation, while others remain relatively constant. The capture of neutrons by short half-life fission products is known as reactor poisoning; neutron capture by long-lived or stable fission products is called reactor slagging. Transient fission product poisons Some of the fission products generated during nuclear reactions have a high neutron absorption capacity, such as xenon-135 (microscopic cross-section σ = 2,000,000 barns (b); up to 3 million barns in reacto ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Borate
A borate is any of a range of boron oxyanions, anions containing boron and oxygen, such as orthoborate , metaborate , or tetraborate ; or any salt of such anions, such as sodium metaborate, and borax . The name also refers to esters of such anions, such as trimethyl borate . Natural occurrence Borate ions occur, alone or with other anions, in many borate and borosilicate minerals such as borax, boracite, ulexite (boronatrocalcite) and colemanite. Borates also occur in seawater, contributing to the absorption of low-frequency sound in seawater. Common borate salts include sodium metaborate (NaBO2) and borax. Borax is soluble in water, so mineral deposits only occur in places with very low rainfall. Extensive deposits were found in Death Valley and shipped with twenty-mule teams from 1883 to 1889. In 1925, deposits were found at Boron, California on the edge of the Mojave Desert. The Atacama Desert in Chile also contains mineable borate concentrations. Borates ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sodium Pentaborate
Sodium pentaborate, more properly disodium decaborate, is a chemical compound of sodium, boron, and oxygen; a salt with elemental formula , , or . It is a colorless crystalline solid, soluble in water. The compound is often encountered or traded as hydrates , , or for ''n'' = 2, 4, 5, or other values. This formula is often misleading as some of the water molecules are actually hydroxyl groups covalently attached to boron atoms. The compound is used in agriculture as a boron supplement in fertilizer with various trade names such as Solubor and Aquabor. It has also been tested as an additive to improve plasma electrolytic oxidation of magnesium alloys. It is also used in nuclear reactors as a neutron absorber/poison. The name "sodium pentaborate" has also been used for a distinct compound with formula , better called trisodium pentaborate. Structure and preparation Dihydrate Sodium pentaborate "dihydrate" has the elemental formula , which can be parsed as or , however the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
ABWR
The advanced boiling water reactor (ABWR) is a Generation III boiling water reactor. The ABWR is currently offered by GE Hitachi Nuclear Energy (GEH) 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. Kashiwazaki-Kariwa unit 6 is considered the first Generation III reactor in the world. Boiling water reactors (BWRs) are the second most common form of light water reactor with a direct cycle design that uses fewer large steam supply components than the pressurized water reactor (PWR), which employs an indirect cycle. The ABWR is the present state of the art in boiling water reactors, and is the first Generation III reactor design to be fully built, with several reactors complete and operating. The first reactors were built on time and under budget in Japan, with others under construction there and in Taiwan. ABWRs were on orde ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Defense In Depth
Defence in depth (also known as deep defence or elastic defence) 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, defence in depth relies on the tendency of an attack to lose momentum over time or as it covers a larger area. A defender can thus yield lightly defended territory in an effort to stress an attacker's logistics or spread out a numerically superior attacking force. Once an attacker has lost momentum or is forced to spread out to pacify a large area, defensive counter-attacks can be mounted on the attacker's weak points, with the goal being to cause attrition or drive the attacker back to its original starting position. Strategy A conventional defence strategy would concentrate all military resources at a front line, which, if breached by an attacker, would leave the remaining defenders in d ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Washington, DC
Washington, D.C., formally the District of Columbia and commonly known as Washington or D.C., is the capital city and Federal district of the United States, federal district of the United States. The city is on the Potomac River, across from Virginia, and shares land borders with Maryland to its north and east. It was named after George Washington, the first president of the United States. The district is named for Columbia (personification), Columbia, the female National personification, personification of the nation. The Constitution of the United States, U.S. Constitution in 1789 called for the creation of a federal district under District of Columbia home rule, exclusive jurisdiction of the United States Congress, U.S. Congress. As such, Washington, D.C., is not part of any U.S. state, state, and is not one itself. The Residence Act, adopted on July 16, 1790, approved the creation of the Capital districts and territories, capital district along the Potomac River. The city ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
International Atomic Energy Agency
The International Atomic Energy Agency (IAEA) is an intergovernmental organization that seeks to promote the peaceful use of nuclear technology, nuclear energy and to inhibit its use for any military purpose, including nuclear weapons. It was established in 1957 as an autonomous international organization; though governed by its own founding treaty, the IAEA Statute, the organization reports to both the United Nations General Assembly, General Assembly and the United Nations Security Council, Security Council of the United Nations, and is headquartered at the United Nations Office at Vienna, UN Office at Vienna, Austria. The IAEA was created in response to growing international concern toward nuclear weapons, especially Cold War (1953–1962), amid rising tensions between the foremost nuclear powers, the United States and the Soviet Union. U.S. president Dwight D. Eisenhower's "Atoms for Peace, Atoms for Peace" speech, which called for the creation of an international organiza ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Curtiss-Wright
The Curtiss-Wright Corporation is an American manufacturer and services provider headquartered in Davidson, North Carolina, with factories and operations in and outside the United States. Created in 1929 from the consolidation (business), consolidation of Curtiss Aeroplane and Motor Company, Curtiss, Wright Aeronautical, Wright, and various supplier companies, the company was immediately the country's largest aviation firm and built more than 142,000 aircraft engines for the U.S. military during World War II. It no longer makes aircraft but still makes many related components, particularly actuators, Aircraft flight control system, aircraft controls, valves, and it provides surface-treatment services. It supplies equipment to the Aerospace manufacturer, commercial, Manufacturing, industrial, defense industry, defense, and energy markets. It makes parts for nuclear power, commercial and nuclear navy, naval nuclear power systems, industrial vehicles, and petroleum industry, oil- and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Steam Turbine
A steam turbine or steam turbine engine is a machine or heat engine that extracts thermal energy from pressurized steam and uses it to do mechanical work utilising a rotating output shaft. Its modern manifestation was invented by Sir Charles Parsons in 1884. It revolutionized marine propulsion and navigation to a significant extent. 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 largest steam turbine ever built is the 1,770 MW Arabelle steam turbine built by Arabelle Solutions (previously GE Steam Power), two units of which will be installed at Hinkley Point C Nuclear Power Station, England. The steam turbine is a form of heat engine that derives much of its improvement in thermodynamic efficiency from the u ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
