核电站事故归纳

A number of criteria and indicators are defined to assure coherent reporting of nuclear events by different official authorities. There are 7 levels on the INES scale; 3 incident-levels and 4 accident-levels. There is also a level 0.7– Major Accident6– Serious Accident5– Accident With Wider Consequences4– Accident With Local Consequences3– Serious Incident2– Incident1– Anomaly0– Deviation (No Safety Significance)Sources: Chernobyl: NRC 1987 and Medvedev 1990; Sellafield: Makhijani et al. eds. 1995, Chapter 8; Three Mile Island: TMI Commission 1979 ; Lagoona Beach (Fermi-I) Alexanderson, ed. 1979 and Fuller 1975; Idaho: Horan and Gammill 1963 and Brynes et al. 1961; Monju: press reports; Chalk River: John May 1989 and Weinberg 1994; Narora, press reports. Full references are available here.Nuclear power plant accidents with multiple fatalities and/or more than US$100 million in property damage, 1952-2011[4][10][17]/wiki/Nuclear_and_radiation_accidentsDate Location Description DeathsI-131Releasein 1,000Ci[18]Cost(inmillions2006$US)INESlevel[19]January 3, 1961 Idaho Falls, Idaho, USExplosion at SL-1, National Reactor Testing Station. Anadditional 1,100 Curies were released as fission products tothe atmosphere, but due to the remoteness, most of it wasrecovered and buried.3 0.08 22 4October 5, 1966 Frenchtown CharterTownship, Michigan,USPartial core meltdown of the Fermi 1 Reactor at the EnricoFermi Nuclear Generating Station. No radiation leakage intothe environment.December 7, 1975 Greifswald, EastGermanyElectrical error causes fire in the main trough thatdestroys control lines and five main coolant pumps0 443 3February 22, 1977 JaslovskéBohunice,CzechoslovakiaSevere corrosion of reactor and release ofradioactivity into the plant area, necessitating totaldecommission0 1,700 4March 28, 1979 Middletown,Pennsylvania, USLoss of coolant and partial core meltdown, seeThree Mile Island accident and Three Mile Islandaccident health effects0 0.017 2,400 5September 15, 1984 Athens, Alabama, USSafety violations, operator error, and design problems forcesix year outage at Browns Ferry Unit 20 110March 9, 1985 Athens, Alabama, US Instrumentation systems malfunction during startup, which ledto suspension of operations at all three Browns Ferry Units0 1,830April 11, 1986 Plymouth,Massachusetts, USRecurring equipment problems force emergency shutdown ofBoston Edison’s Pilgrim Nuclear Power Plant0 1,001April 26, 1986 Pripyat, UkraineSteam explosion and meltdown (see Chernobyldisaster) necessitating the evacuation of 300,000people from Kiev and dispersing radioactivematerial across Europe (see Chernobyl disastereffects)53 7000 6,700 7May 4, 1986 Hamm-Uentrop,GermanyExperimental THTR-300 reactor releases small amounts offission products (0.1 GBq Co-60, Cs-137, Pa-233) tosurrounding area0 0 267March 31, 1987 Delta, Pennsylvania,USPeach Bottom units 2 and 3 shutdown due to coolingmalfunctions and unexplained equipment problems0 400December 19, 1987 Lycoming, New York,USMalfunctions force Niagara Mohawk Power Corporation toshut down Nine Mile Point Unit 10 150March 17, 1989 Lusby, Maryland, USInspections at Calvert Cliff Units 1 and 2 reveal cracks atpressurized heater sleeves, forcing extended shutdowns0 120February 20, 1996 Waterford, Connecticut,USLeaking valve forces shutdown Millstone Nuclear Power PlantUnits 1 and 2, multiple equipment failures found0 254September 2, 1996 Crystal River, Florida,USBalance-of-plant equipment malfunction forces shutdown andextensive repairs at Crystal River Unit 30 384September 30, 1999 Ibaraki Prefecture,JapanWorkers at the Tokaimura uranium processingfacility added too many buckets of uranium directlyinto a precipitation tank, causing it to go critical,2 54 4killing two, and exposing one more to radiation levels above permissible limitsFebruary 16, 2002 Oak Harbor, Ohio, USSevere corrosion of control rod forces 24-month outage ofDavis-Besse reactor0 143 3August 9, 2004 Fukui Prefecture,JapanSteam explosion at Mihama Nuclear Power Plantkills 5 workers and injures dozens more5 9 1March 11, 2011 Ōkuma,Fukushima, JapanCooling failure in 3 reactors following anearthquake and a Hydrogen explosion atFukushima I Nuclear Power Plant0 6Nuclear meltdownnuclear meltdown is an informal term for a severe nuclear reactor accident that results in core damage from overheating. The term is not officially defined by the International Atomic Energy Agency[1] or by the U.S. Nuclear Regulatory Commission.[2] However, it has been defined to mean the accidental melting of the core of a nuclear reactor,[3] and is in common usage a reference to the core's either complete or partial collapse. "Core melt accident" and "partial core melt" are the analogous technical terms, though the severity of these nuclear accidents can vary in the extreme.A meltdown occurs when a severe failure of a nuclear power plant system prevents proper cooling of the reactor core, to the extent that the nuclear fuel assemblies overheat and melt, either partially or completely. A meltdown is considered very serious because of the potential that highly intense radioactive materials with long half-lives and lethal threat could be released into the environment.Light water reactorsTMI-2 Core End-State ConfigurationBefore the core of a light water nuclear reactor can bedamaged, two precursor events must have alreadyoccurred:∙ A limiting fault (or a set of compoundedemergency conditions) that leads to the failureof heat removal within the core (the loss ofcooling). Low water level uncovers the core,allowing it to heat up.∙Failure of the emergency core cooling system.The ECCS (Emergency Core Cooling System)is designed to rapidly cool the core and makeit safe in the event of the maximum fault (thedesign basis accident) that nuclear regulatorsand plant engineers could imagine.Other reactor typesOther types of reactors have different capabilities and safety profiles than the LWR does. Advanced varieties ofseveral of these reactors have the potential to be inherently safe.CANDU reactorsCANDU reactors, Canadian-invented deuterium-uranium design, are designed with at least one, and generally two, large low-temperature and low-pressure water reservoirs around their fuel/coolant channels. The first is the bulk heavy-water moderator (a separate system from the coolant), and the second is the light-water-filled shield tank. These backup heat sinks are sufficient to prevent either the fuel meltdown in the first place (using the moderator heat sink), or the breaching of the core vessel should the moderator eventually boil off (using the shield tank heat sink).[14] Other failure modes aside from fuel melt will probably occur in a CANDU rather than a meltdown, such as deformation of the calandria into a non-critical configuration. All CANDU reactors are located within standard Western containments as well.The CANDU ("CANada Deuterium Uranium") reactor is a Canadian-invented, pressurized heavy water reactor. The reactors are used in nuclear power plants to produce nuclear power from nuclear fuel. CANDU reactors were developed initially in the late 1950s and 1960s through a partnership between Atomic Energy of Canada Limited (AECL), the Hydro-Electric Power Commission of Ontario (now Ontario Power Generation), Canadian General Electric (now GE Canada), and other private industry participants.The acronym "CANDU", a registered trademark of Atomic Energy of Canada Limited, stands for "CAN adaD euterium U ranium". This is a reference to its deuterium-oxide (heavy water) moderator and its use of uranium fuel (originally, natural uranium). All current power reactors in Canada are of the CANDU type. Canada markets this power reactor abroad. In December 2009, the Canadian Federal Government announced that they would be seeking private investors for a partial sell-off of its CANDU division.[1]Qinshan Phase III Units 1 & 2, located in Zhejiang China (30.436 N 120.958 E): Two CANDU 6 reactors, designed by Atomic Energy of Canada Limited (AECL), owned and operated by the Third Qinshan Nuclear Power Company Limited. Photo courtesy of AECL.http://www.nuclearfaq.ca/Schematic Diagram of a CANDU reactor: The primary loop is in yellow and orange, the secondary in blue and red. The cool heavy water in the calandria can be seen in pink, along with partially inserted shutoff rods.Key1 Fuel bundle 8 Fueling machines2 Calandria (reactor core) 9 Heavy water moderator3 Adjuster rods 10 Pressure tube4 Heavy water pressure reservoir 11 Steam going to steam turbine5 Steam generator12 Cold water returning from turbine6 Light water pump13 Containment building made of reinforced concrete7 Heavy water pumpTritium is a radioactive form of hydrogen (H-3), with a half-life of 12.3 years. It is found in small amounts in nature (about 4 kg globally), created by cosmic ray interactions in the upper atmosphere. Tritium is considered to be a weak radionuclide because of the low energy of its radioactive emissions (beta particle energy 0 -19 keV).[29] The beta particles do not travel very far in air and do not penetrate skin; therefore the main biological hazard of tritium is due to its intake into the body (inhalation, ingestion, or absorption).Tritium is generated in all nuclear power designs; however, CANDU reactors generate more tritium in their coolant and moderator than light-water designs, due to neutron capture in heavy hydrogen. Some of this tritium escapes into containment and is generally recovered; however a small percentage (about 1%) escapes containment and constitutes a routine radioactive emission from CANDU plants (also higher than from an LWR of comparable size). Operation of a CANDU plant therefore includes monitoring of this effluent in the surrounding biota (and publishing the results), in order to ensure that emissions are maintained below regulatory limits.In some CANDU reactors the tritium concentration in the moderator is periodically reduced by an extraction process, in order to further reduce this risk. Typical tritium emissions from CANDU plants in Canada are less than 1% of the national regulatory limit, which is based upon the guidelines of the International Commission on Radiological Protection (ICRP)[30] (for example, the maximum permitted drinking water concentration for tritium in Canada,[31] 7000 Bq/L, corresponds to 1/10 of the ICRP's public dose limit). Tritium emissions from other CANDU plants are similarly low.[32][33]In general there is significant public controversy associated with radioactive emissions from nuclear power plants, and for CANDU plants one of the main concerns is tritium. In 2007 Greenpeace published a critique of tritium emissions from Canadian nuclear power plants by Dr. Ian Fairlie.[34] This report was disputed by Dr. Richard Osborne. [35]Gas-cooled reactors One type of Western reactor, known as the advanced gas-cooled reactor (or AGCR), built by the United Kingdom, is not very vulnerable to loss-of-cooling accidents or to core damage except in the most extreme of circumstances. By virtue of the relatively inert coolant (carbon dioxide), the large volume and high pressure of the coolant, and the relatively high heat transfer efficiency of the reactor, the time frame for core damage in the event of a limiting fault is measured in days. Restoration of some means of coolant flow will prevent core damage from occurring.Other types of highly advanced gas cooled reactors, generally known as high-temperature gas-cooled reactors (HTGRs) such as the Japanese High Temperature Test Reactor and the United States' Very High Temperature Reactor, are inherently safe, meaning that meltdown or other forms of core damage are physically impossible, due to the structure of the core, which consists of hexagonal prismatic blocks of silicon carbide reinforced graphite infused with TRISO or QUADRISO pellets of uranium, thorium, or mixed oxide buried underground in a helium-filled steel pressure vessel within a concrete containment. Though this type of reactor is not susceptible to meltdown, additional capabilities of heat removal are provided by using regular atmospheric airflow as a means of backup heat removal, by having it pass through a heat exchanger and rising into the atmosphere due to convection, achieving full residual heat removal. The VHTR is scheduled to prototyped and tested at Idaho National Laboratory within the next decade (as of 2009) as the design selected for the Next Generation Nuclear Plant by the US Department of Energy. This reactor will use a gas as a coolant, which can then be used for process heat (such as in hydrogen production) or for the driving of gas turbines and the generation of electricity.A similar highly-advanced gas cooled reactor originally designed by West Germany (the AVR reactor) and now developed by South Africa is known as the Pebble Bed Modular Reactor. It is an inherently safe design, meaning that core damage is physically impossible, due to the design of the fuel (spherical graphite "pebbles" arranged in abed within an metal RPV and filled with TRISO (or QUADRISO) pellets of uranium, thorium, or mixed oxide within). A prototype of a very similar type of reactor has been built by the Chinese, HTR-10, and has worked beyond researchers' expectations, leading the Chinese to announce plans to build a pair of follow-on, full-scale 250 MWe, inherently safe, power production reactors based on the same concept. (See Nuclear power in the People's Republic of China for more information.)Soviet Union-designed reactorsRBMKs: Soviet designed RBMKs, found only in Russia and the CIS and now shut down everywhere except Russia, do not have containment buildings, are naturally unstable (tending to dangerous power fluctuations), and also have ECCS systems that are considered grossly inadequate by Western safety standards.MKER The MKER is a modern Russian-engineered channel type reactor that is a distant descendant of the RBMK. It approaches the concept from a different and superior direction, optimizing the benefits, and fixing the flaws of the original RBMK design.Experimental or conceptual designs Some design concepts for nuclear reactors emphasize resistance to meltdown and operating safety. The PIUS (process inherent ultimate safety) designs, originally engineered by the Swedes in the late 1970s and early 1980s, are LWRs that by virtue of their design are resistant to core damage. No units have ever been built.Meltdowns that have occurred∙ A number of Soviet Navy nuclear submarines experienced nuclear meltdowns, including K-27, K-140, and K-431.∙There was also a fatal core meltdown at SL-1, an experimental U.S. military reactor in Idaho.The only large-scale nuclear meltdowns at civilian nuclear power plants∙the Lucens reactor, Switzerland, in 1969.∙the Three Mile Island accident in Pennsylvania, U.S.A., in 1979.∙the Chernobyl disaster at Chernobyl Nuclear Power Plant, Ukraine, U.S.S.R., in 1986.Other core meltdowns have occurred at:∙NRX (military), Ontario, Canada, in 1952∙EBR-I (military), Idaho, U.S.A., in 1955∙Windscale (military), Sellafield, England, in 1957 (see Windscale fire)∙Sodium Reactor Experiment, Santa Susana Field Laboratory, Simi Valley, California, U.S.A., in 1959 ∙Fermi 1 (civil), Michigan, U.S.A., in 1966∙A1 plant at Jaslovské Bohunice, Czechoslovakia, in 1977。