Nuclear Reactors Nuclear Power Plant Nuclear Reactor TechnologyUpdated November 2. Most nuclear electricity is generated using just two kinds of reactors which were developed in the 1. New designs are coming forward and some are in operation as the first generation reactors come to the end of their operating lifetimes. Over 1. 1 of the worlds electricity is produced from nuclear energy, more than from all sources worldwide in 1. This paper is about the main conventional types of nuclear reactor. For more advanced types, see Advanced Reactors and Small Reactors papers, and also Generation IV reactors. A nuclear reactor produces and controls the release of energy from splitting the atoms of certain elements. In a nuclear power reactor, the energy released is used as heat to make steam to generate electricity. In a research reactor the main purpose is to utilise the actual neutrons produced in the core. In most naval reactors, steam drives a turbine directly for propulsion. The principles for using nuclear power to produce electricity are the same for most types of reactor. The energy released from continuous fission of the atoms of the fuel is harnessed as heat in either a gas or water, and is used to produce steam. The steam is used to drive the turbines which produce electricity as in most fossil fuel plants. The worlds first nuclear reactors operated naturally in a uranium deposit about two billion years ago. These were in rich uranium orebodies and moderated by percolating rainwater. The 1. 7 known at Oklo in west Africa, each less than 1. W thermal, together consumed about six tonnes of that uranium. It is assumed that these were not unique worldwide. Today, reactors derived from designs originally developed for propelling submarines and large naval ships generate about 8. The main design is the pressurised water reactor PWR which has water at over 3. C under pressure in its primary coolingheat transfer circuit, and generates steam in a secondary circuit. The less numerous boiling water reactor BWR makes steam in the primary circuit above the reactor core, at similar temperatures and pressure. Both types use water as both coolant and moderator, to slow neutrons. Since water normally boils at 1. C, they have robust steel pressure vessels or tubes to enable the higher operating temperature. Another type uses heavy water, with deuterium atoms, as moderator. Hence the term light water is used to differentiate. Components of a nuclear reactor. Issuu is a digital publishing platform that makes it simple to publish magazines, catalogs, newspapers, books, and more online. Easily share your publications and get. With up to 200 more light on the road, Lucas HID gas discharge bulbs deliver a brighter driving experience. TecDoc 2 Quarter 2017 Parts Catalog, parts manual TecDoc 201704 Full Parts Catalog, parts book TecDoc 201704 Full Parts Catalog, download program TecDoc 201704. MERCEDES BENZ SMART EWAnet EPC 08. 2017 EPC ONLY WITH DATACARDS ENABLED want to buy it for 50 email us global. epcyandex. com Mercedes Benz EWAnet EPC. Microsoft Windows 10 10. 0. 16299. 15 Version 1709 Updated Sept 2017 Оригинальные образы от Microsoft MSDN Ru. There are several components common to most types of reactors Fuel.  Uranium is the basic fuel. Usually pellets of uranium oxide UO2 are arranged in tubes to form fuel rods. The rods are arranged into fuel assemblies in the reactor core.  In a 1. MWe class PWR there might be 5. In a new reactor with new fuel a neutron source is needed to get the reaction going. Usually this is beryllium mixed with polonium, radium or other alpha emitter. Alpha particles from the decay cause a release of neutrons from the beryllium as it turns to carbon 1. Restarting a reactor with some used fuel may not require this, as there may be enough neutrons to achieve criticality when control rods are removed. Moderator. Material in the core which slows down the neutrons released from fission so that they cause more fission. It is usually water, but may be heavy water or graphite. Control rods. These are made with neutron absorbing material such as cadmium, hafnium or boron, and are inserted or withdrawn from the core to control the rate of reaction, or to halt it. In some PWR reactors, special control rods are used to enable the core to sustain a low level of power efficiently.  Secondary control systems involve other neutron absorbers, usually boron in the coolant its concentration can be adjusted over time as the fuel burns up. PWR control rods are inserted from the top, BWR cruciform blades from the bottom of the core. In fission, most of the neutrons are released promptly, but some are delayed. These are crucial in enabling a chain reacting system or reactor to be controllable and to be able to be held precisely critical. Coolant. A fluid circulating through the core so as to transfer the heat from it. In light water reactors the water moderator functions also as primary coolant. Except in BWRs, there is secondary coolant circuit where the water becomes steam. See also later section on primary coolant characteristics.  A PWR has two to four primary coolant loops with pumps, driven either by steam or electricity Chinas Hualong One design has three, each driven by a 6. MW electric motor, with each pump set weighing 1. Pressure vessel or pressure tubes. Usually a robust steel vessel containing the reactor core and moderatorcoolant, but it may be a series of tubes holding the fuel and conveying the coolant through the surrounding moderator. Steam generator.  Part of the cooling system of pressurised water reactors PWR PHWR where the high pressure primary coolant bringing heat from the reactor is used to make steam for the turbine, in a secondary circuit. Essentially a heat exchanger like a motor car radiator Reactors have up to six loops, each with a steam generator.  Since 1. PWR reactors have had their steam generators replaced after 2. USA. These are large heat exchangers for transferring heat from one fluid to another here from high pressure primary circuit in PWR to secondary circuit where water turns to steam. Each structure weighs up to 8. N 1. 6, formed by neutron bombardment of oxygen, with half life of 7 seconds. The secondary water must flow through the support structures for the tubes. The whole thing needs to be designed so that the tubes dont vibrate and fret, operated so that deposits do not build up to impede the flow, and maintained chemically to avoid corrosion. Tubes which fail and leak are plugged, and surplus capacity is designed to allow for this. Leaks can be detected by monitoring N 1. Containment. The structure around the reactor and associated steam generators which is designed to protect it from outside intrusion and to protect those outside from the effects of radiation in case of any serious malfunction inside. It is typically a metre thick concrete and steel structure. Newer Russian and some other reactors install core melt localisation devices or core catchers under the pressure vessel to catch any melted core material in the event of a major accident. There are several different types of reactors as indicated in the following table. Nuclear power plants in commercial operation or operable. Reactor type. Main countries. Number. GWe. Fuel. Coolant. Moderator. Pressurised water reactor PWRUS, France, Japan, Russia, China. UO2waterwater. Boiling water reactor BWRUS, Japan, Sweden. UO2waterwater. Pressurised heavy water reactor PHWRCanada, India. UO2heavy waterheavy water. Gas cooled reactor AGR MagnoxUK1. U metal,enriched UO2. CO2graphite. Light water graphite reactor RBMK EGPRussia. UO2watergraphite. Fast neutron reactor FBRRussia. Pu. O2 and UO2liquid sodiumnone TOTAL4. IAEA data, end of 2. GWe capacity in thousands of megawatts grossFor reactors under construction, see information paper on Plans for New Reactors Worldwide. Fuelling a nuclear power reactor. Most reactors need to be shut down for refuelling, so that the reactor vessel can be opened up. In this case refuelling is at intervals of 1.