Nuclear Disasters free essay sample

Nuclear Disasters and Accidents Introduction: One of the scariest things about nuclear power is when something goes wrong and an accident occurs. Radiation is released into the environment and people get hurt. Two of the most famous nuclear accidents occurred at the Three Mile Island reactor 2 in the United States and the Chernobyl reactor 4 in the former Soviet Union. In this text we will discuss these two disasters, along with correcting a few common misconceptions about nuclear accidents. The Myth of a Reactor Explosion: It is impossible for any PWR or LWR nuclear reactor to explode like an atomic bomb. This is because in order for an uncontrolled chain reaction to occur that is similar to an atom bomb, the uranium fuel must be extremely enriched, much more than the 4% 235U that is present in regular, commercial nuclear reactor fuel. So, if it cant explode, what does happen in a nuclear reactor? The answer is what is called a meltdown. When a meltdown occurs in a reactor, the reactor melts. That is, the temperature rises in the core so much that the fuel rods actually turn to liquid, like ice turns into water when heated. If the core continued to heat, the reactor would get so hot that the steel walls of the core would also melt. In a complete reactor meltdown, the extremely hot (about 2700i Celsius) molten uranium fuel rods would melt through the bottom of the reactor and actually sink about 50 feet into the earth beneath the power plant. The molten uranium would react with groundwater, producing large explosions of radioactive steam and debris that would affect nearby towns and population centers. In general a nuclear meltdown would occurr if the reactor loses its coolant. This is what occured in the two disasters that we will discuss. Without coolant, the cores temperature would rise, resulting in the meltdown scenario we explained above. You may be wondering, Why cant they just drop the control rods in the reactor if it starts to get out of control? . The answer is that they can. The problem is that, even if the control rods are completely dropped in and the nuclear chain reaction stops, the reactor is still extremely hot and will not cool down unless coolant is put back in. The residual heat and the heat produced from the decay of the fission products are enough to drive the cores temperature up even if the nuclear chain reaction stops. Three Mile Island: Outside View of the Three Mile Island Nuclear Power Plant Photo Courtesy Nuclear Regulatory Commission On an island 10 miles from Harrisburg Pennsylvania resides the Three Mile Island Nuclear Power Station. There are two reactors at the plant, dubbed Unit 1 and Unit 2. One of them is inoperable. Unit 2 experienced a partial reactor meltdown on March 28, 1979. A partial nuclear meltdown is when the uranium fuel rods start to liquefy, but they do not fall through the reactor floor and breach the containment systems. The accident which occurred at Unit 2 is considered to be the worst nuclear disaster in US history. Why did it happen? There are many reasons for the accident, but the two main ones are simple human error and the failure of a rather minor valve in the reactor. In the following paragraphs, we will explain how it was possible for the accident to happen and both its psychological and physical effects on the American people. The accident at TMI (Three Mile Island) began at about four in the morning with the failure of one of the valves that controlled coolant flow into the reactor. Because of this, the amount of cool water entering the reactor decreased, and the core temperature rose. When this happened, automatic computerized systems engaged, and the reactor was automatically SCRAMmed. The nuclear chain reaction then stopped. This only slowed the rate at which the core temperature was increasing, however. The temperature was still rising because of residual heat in the reactor and energy released from the decaying fission products in the fuel rods. Because the pumps removing water from the core were still active, and a valve that controlled the cool water entering the core failed, water was leaving the core, but not coming in. This reduced the amount of coolant in the core. There wasnt enough coolant in the core, so the Emergency Core Cooling System automatically turned on. This should have provided enough extra coolant to make up for the stuck valve, except that the reactor operator, thinking that enough coolant was already in the core, shut it off too early. There still wasnt enough coolant, so the cores temperature kept increasing. A valve at the top of the core automatically opened to vent some of the steam in the core. This should have helped matters by removing the hot steam, but the valve didnt close properly. Because it didnt close, steam continued to vent from the reactor, further reducing the coolant level. The reactor operators should have known the valve didnt close, but the indicator in the control room was covered by a maintenance tag attached to a nearby switch. Because the operators didnt know that the valve had failed to close, they assumed that the situation was under control, as the core temperature had stopped rising with the first venting of steam from the core. They also thought that the coolant had been replaced in the core, because they didnt know that the pump outlets were closed. A few minutes later the core temperature began to rise again, and the Emergency Core Cooling System automatically switched on. Once again, an operator de-activated it, thinking the situation was under control. In reality, it was not. Soon, because of the coolant lost through the open valve at the top of the reactor, the core temperature began to rise again. At this point the fuel rods started to collapse from the intense heat inside the core. The operators knew something was wrong, but didnt understand what it was. This was about 5 minutes after the initial valve failure. It took almost 2 hours for someone to figure out that the valve releasing steam at the top of reactor hadnt closed properly. During those 2 hours, precious coolant continued to be released from the reactor a meltdown was underway. At approximately 6AM, an operator discovered the valve at the top of the core was open and closed it. During the day hydrogen gas began to accumulate inside the reactor and caused an explosion later in the afternoon. This explosion did not damage the containment systems, however. Two days later, the core was still not under operator control. A group of nuclear experts were asked to help evaluate the situation. They figured out that a lot of hydrogen gas had accumulated at the top of the core. This gas could have exploded, like the explosion on the first day of the accident, or it could have displaced the remaining coolant in the reactor, causing a complete nuclear reactor meltdown. No one really knew what to do about the hydrogen build-up. A hydrogen recombiner was used to remove some of the hydrogen, but it was not very effective. However, hydrogen also dissolves in water, which is what the coolant was composed of. Thus, over time the hydrogen that had collected at the top of the core completely dissolved in the coolant. Two weeks later the reactor was brought to a cold shutdown and the accident was over. No one was directly injured as a result of the accident. However, some radioactive gas and water were vented to the environment around the reactor. At one point, radioactive water was released into the Susquehanna river, which is a source of drinking water for nearby communities. No one is really sure what effects these radioactive releases might have had on people living near the power plant. Chernobyl: About 80 miles (130 km) north of Kiev, in what is now the Ukraine, is located the Chernobyl nuclear power plant. At this plant the worst reactor disaster to ever occur took place on April 26, 1986. It happened largely because normal reactor operations were suspended; an experiment was to take place in the reactor. As a result, normal safety guidelines were disregarded, and the accident occurred. However, as with most accidents of this type, it was a result of many small mistakes adding up to create a catastrophe. In the following paragraphs, we will outline just how the event transpired: Early in the day, before the test, the power output of the reactor was dropped in preparation for the upcoming test. Unexpectedly, the reactors power output dropped way too much, almost to zero. Because of this drop, some control rods were removed to bring the power back up. (As you recall from the fission power text, the more control rods there are in a reactor, the more free neutrons are absorbed and the less fissioning that goes on. So, more control rods means less energy and power output. The reactors power output raised up, and all appeared to be normal. More preparation for the test began later when two pumps were switched on in the cooling system. They increased water flow out of the reactor, and thus removed heat more quickly. They also caused the water level to lower in a component of the reactor called the steam separator. Because of the low level of water in the steam separator, the operator increa sed the amount of feed water coming into it, in the hopes that the water level would rise. Also, more control rods were taken out of the reactor to raise internal reactor temperature and pressure, lso in the hopes that it would cause the water level in the steam separator to rise. The water level in the steam separator began to rise, so the operator adjusted again the flow of feed water by lowering it. This decreased the amount of heat being removed from the reactor core. Because many control rods had been removed and the amount of heat being taken from the core by the coolant had been reduced, it began to get very hot. Also, there was relatively low pressure in the core because the amount of incoming water had been decreased. Because of the heat and the low pressure, coolant inside the core began to boil to form steam. The actual test began with the closing of the turbine feed valves. This should have caused an increase in pressure in the cooling system, which in turn would have caused a decrease in steam in the core. This should have lowered the reactivity in the core. Thus, the normal next step when closing the turbine feed valves was to retract more control rods, increasing reactivity in the core. This is what the operator at Chernobyl did. The only problem was that in this case there was no increase in pressure in the cooling system because of the earlier feed water reduction. This meant that there was already a normal amount of steam in the core, even with the turbine feed valves closed. Thus, by retracting more control rods to make up for a reduction in steam that didnt happen, the operator caused too much steam to be produced in the core. With the surplus of steam, the reactors power output increased. Soon, even more steam was being produced. The operator realized there was a problem and SCRAMmed the reactor, completely disabling all fission reactions. However, it was too late. The temperature and pressure inside the reactor had already risen dramatically, and the fuel rods had begun to shatter. After the fuel rods shattered, two explosions occurred as a result of liquid uranium reacting with steam and from fuel vapor expansion (caused by the intense heat). The reactor containment was broken, and the top of the reactor lifted off. With the containment broken, outside air began to enter the reactor. In this particular Soviet reactor, graphite was used as a moderator instead of water. (water was the coolant) As air entered the core, it reacted with the graphite. Graphite is essentially just carbon, so oxygen from the air chemically combined with the carbon to form CO (carbon monoxide). Carbon monoxide is flammable and soon caught fire. The fire emitted extremely radioactive smoke into the area surrounding the reactor. Additionally, the explosion ejected a portion of the reactor fuel into the surrounding atmosphere and countryside. This fuel contained both fission products and transuranic wastes. During the days following the accident, hundreds of people worked to quell the reactor fire and the escape of radioactive materials. Liquid nitrogen was pumped into the reactor core to cool it down. Helicopters dumped neutron-absorbing materials into the exposed core to prevent it from going critical. Sand and other fire-fighting materials were also dropped into the core to help stop the graphite fire. All in all, over 5000(metric) tons of material were dropped into the core. After the fires were brought under control, construction of what is called the sarcophagus began. The word sarcophagus is usually used to describe the elaborate coffins the ancient Egyptians used to entomb their dead. In this case, the sarcophagus is a structure erected from about 300,000 metric tons of concrete that surrounds the reactor. It was designed to contain the radioactive waste inside. It has served its purpose well, but, now, ten years after the accident, several flaws have been found in it. Holes have begun to appear in the roof, allowing rainwater to accumulate inside. This water can corrode the structure, further weakening it. Also, birds and other animals have been seen making homes in the sarcophagus. If they should ingest radioactive material, they could spread it around the countryside. Additionally, with time the sarcophagus has become worn down. It is conceivable that an intense event like an earthquake, tornado, or plane crash directly on the sarcophagus could lead to its collapse. This would be catastrophic, as radioactive dust would once again rain down on the surrounding areas. Scientists and engineers are working on ways to repair or replace the structure. One of the great tragedies of the accident was that the Soviet government tried to cover it up. Clouds of fallout were traveling towards major population centers such as Minsk, and no one was warned. No one outside the Soviet Union knew about the accident until two days later, when scientists in Sweden detected massive amount of radiation being blown from the east. The effects of the disaster at Chernobyl were very widespread. The World Health Organization (WHO) found that the radiation release from the Chernobyl accident was 200 times that of the Hiroshima and Nagasaki nuclear bombs combined. The fallout was also far-reaching. For a time, radiation levels in a Scotland were 10,000 times the norm. 30 lives were directly lost during the accident or within a few months after it. Many of these lives were those of the workers trying to put out the graphite fire and were lost from radiation poisoning. The radiation released has also had long-term effects on the cancer incidence rate of the surrounding population. According to the Ukrainian Radiological Institute over 2500 deaths resulted from the Chernobyl incident. The WHO has found a significant increase in cancer in the surrounding area. For example, in 1986 (the year of the accident), 2 cases of childhood thyroid cancer occurred in the Gomel administrative district of the Ukraine (this is the region around the plant). In 1993 there were 42 cases, which is 21 times the rate in 1986. The rate of thyroid cancer is particularly high after the Chernobyl accident because much of the radiation was emitted in the form iodine-131, which collects in the thyroid gland, especially in young children. Other cancer incidence rates didnt seem to be affected. For example, leukemia was no more prevalent after the accident than before. What caused the accident? This is a very hard question to answer. The obvious one is operator error. The operator was not very familiar with the reactor and hadnt been trained enough. Additionally, when the accident occurred, normal safety rules were not being followed because they were running a test. For example, regulations required that at least 15 control rods always remain in the reactor. When the explosion occurred, less than 10 were present. This happened because many of the rods were removed to raise power output. This was one of the direct causes of the accident. Also, the reactor itself was not designed well and was prone to abrupt and massive power surges. Fermi I Breeder Reactor The Fermi I reactor was a breeder located at Lagoona Beach, 30 miles from Detroit. On October 5, 1966, high temperatures were measured (700 compared to normal 580? F) and radiation alarms sounded involving two fuel rod subassemblies. The reactor scrammed and there was indication of fuel melting. After a month of sweating, they tested out enough subassemblies to limit the damage to 6 subassemblies. By January 67 they had learned that 4 subassemblies were damaged with two stuck together, but it took until May to remove the assemblies. When they had checked the sodium flow earlier, they had detected a clapping noise. In August 67 they were able to lower a eriscope device into the meltdown pan and found that a piece of zirconium cladding had come loose and was blocking the sodium coolant nozzles. The zirconium cladding was part of the lining of the meltdown cone designed to direct the distribution of fuel material should a meltdown of the fuel occur. Such structures are necessary in a breeder reactor because of the possibliity of molten fuel reassembling itself in a cr itical configuration. This is not a possibility in an ordinary light water reactor because of the low level of enrichment of the uranium, but a fast breeder reactor is operated with a much higher level of enrichment. The phrase China syndrome was coined in regard to this accident as they were contemplating the possibilities should a meltdown of fuel with critical reassembly take place. The uncontrolled fission reaction could create enough heat to melt its way into the earth, and some engineer remarked it could go all the way to China. With ingenious tools designed and built for the purpose, the piece of zirconium was fished out in April of 1968. In May of 1970, the reactor was ready to resume operation, but a sodium explosion delayed it until July of 1970. In October it finally reached a level of 200 Mwatts. The total cost of the repair was about $132 million. In August of 1972 upon denial of the extension of its operating license, the shutdown process for the plant was initiated. Subject: Calendar of Nuclear Accidents and Events (Updated 21st March) Calendar of Nuclear Accidents Below is a calendar that shows the threat that humanity faces from the atom bomb and the nuclear fuel cycle. This calendar gives some examples of the everyday nuclear incidents that have occurred all over the world. It demonstrates how technological failures coupled with human error risk public health and the environment on an almost daily basis. January 1-1992: Four tons of heavy water spilt at Rajasthan nuclear power plant (India) 2-1993: Leak at Kozloduy nuclear power plant, release of radioactive steam (Bulgaria) 3-1961: Explosion in reactor Idaho Falls (USA); three people killed 4-1965: 6. 5 kg plutonium sludge released from Savannah River reprocessing plant (USA) 5-1976: Two workers killed by radioactive carbon dioxide at Bohunice nuclear power plant (Slovakia) 6-1981: Accident at La Hague reprocessing plant (France) 7-1974: Explosion at Leningrad nuclear power plant (Russia) -1975: Release of radioactivity from Mihama nuclear power plant (Japan) 9-1993: Radioactive release from leaking fuel rods at Perry nuclear power plant (USA) 10-1987: Nuclear transport accident in the UK 11-1985: In Heilbronn (Germany), a Pershing-II nuclear missile catches fire, three people killed 12-1960: Technicians trying to restart a reactor at Savannah River reprocessing plant almost send it out of control (USA) 13-1964: A B-52 plane crashes with nuclear bombs on board in Maryland (USA) 14-1969: USS Enterprise, nuclear aircraft-carrier, suffers fires and explosions, killing 28 crew members 15- 6-1990: Loss of offsite power with multiple equipment failures at Dresden nuclear power plant (USA) 17-1966: A B-52 plane crashes in Spain causing plutonium contamination 18-1989: Eight workers are contaminated at Savannah River reprocessing plant (USA) 19-1992: Radioactive leak, reactor shut-down at Kola nuclear power plant (Russia) 20-1993: Technical failure at Paluel causes subcooling accident (France) 21-1969: Technical failure at Swiss experimental nuclear reactor causes release of radioactive water 22-1992: Technical failure in shut-down system at Balakovo nuclear power plant (Russia) 23- 1978: Radioactive helium released from Colorado reactor (USA) 24-1978: Soviet nuclear-powered satellite Cosmos-954 crashes in Canada 25-1982: Steam generator ruptures at R. E. Ginna nuclear power plant (USA) 26-1988: Dangerous temperature rise in a nuclear reactor on board a British submarine 27-1992: Leak causes a shut-down at Darlington nuclear power plant (Canada) 28-1990: Pump failure during a shut-down at Gravelines nuclear power plant (France) 29-1961: A B-52 plane carrying nuclear bombs crashes, the bombs do not explode but three of the eight crew members are killed (USA) 30- 31 -1996: Leakage of radiation due to human error and technical failure at Dimitrovgrad nuclear research centre (Russia) February 1-1982: Release of 100 cubic metres of radioactive water from Salem nuclear power plant (USA) 2-1993: Breakdown of cooling system for two hours at Kola nuclear power plant (Russia) 3-1992: Failure of cooling pumps at Kozloduy nuclear power plant (Bulgaria) 4- -1986: Amber alert (indicating an emergency in one building and a threat to the rest of the plant) at Sellafield reprocessing plant, UK 6-1974: Explosion and radiation leak at Leningrad nuclear power plant, three people killed (Russia) 7- 8-1991: Release of radioactivity from Fukui nuclear power plant (Japan) 9-1991: Rupture of steam generator pipe causes release of radioactivity at Mihama nuclear power plant (Japan) 10-1992: Technical failure in pump system at Zaporozhe nuclear power plant (Ukraine) 11-1986: Release of 13 tonnes of radioactive carbon dioxide from Transfynydd nuclear power plant (UK) 12-1968: A B-52 plane with nuclear bombs on board crashes near Toronto (Canada) 13-1960: First French nuclear test 14- 5-1993: Spillage of 18,000 litres of heavy water at Darlington nuclear power plant (Canada) 16-1973: Container filled with Cobalt-60 lost in the North Sea 17-1984: Accident at Kozloduy nuclear power plant (Bulgaria) 18-1988: Report of core melt in the nuclear reactor of the Soviet Ice-Breaker Rossiya 19-1986: Three workers suffer contamination at the Sellafield reprocessing plant (UK) 20-1990: Eight employees receive radiation exposure at Point Lepreau (Canada ) 21-1976: Accident at Bohunice nuclear power plant (Slovakia) 22-1993: High pressure steam accident kills one worker and injures two others at Fukushima nuclear power plant (Japan) 23-1981: Accidental explosion of a Pershing-II missile in Germany 24-1972: Accident on board Soviet nuclear-powered submarine causes vessel to lose all power 25-1983: Failure of automatic shut-down at Salem nuclear power plant (USA) 26-1988: Increased levels of radioactivity at Bohunice nuclear power plant (Slovakia) 27-1983: Nuclear powered satellite falls into the Indian Ocean 28-1992: Software failure in the control computer at Embalse nuclear power plant (Argentina) March 1-1954: Fall-out of US nuclear weapons test Bravo contaminates the inhabitants of the Pacific island of Rongelap. 2-1994: Breakdown of cooling system at Kola nuclear power plant (Russia) 3-1992: Technical failure at Novovoronezh nuclear power plant (Russia) 4-1977: Kozloduy nuclear power plant affected by an earthquake (Bulgaria) 5- 6-1985: Emergency cooling system out of order at the Grohnde nuclear power plant (Germany) 7- 8-1972: Radioactive water has to be pumped out of the Indian Point nuclear power plant (USA) 9-1992: Fire at Kola nuclear power plant (Russia) 0-1956: A B-47 plane disappears with nuclear weapons on board in the Atlantic Ocean 11-1958: A B-47 plane loses nuclear bomb in South Carolina (USA) 12-1981: Tornado washes nuclear waste from Moruroa into the lagoon (Pacific) 13-1986: US nuclear submarine runs aground and suffers damage 14-1961: A B-52 plane crashes with nuclear bombs on board in California (USA) 15-1989: Technical failure of fuel roads at Pickering nuclear power plant (Canada) 16- 17-1984: Emergency cooling system at San Onofere nuclear power plant fails (USA) 18-1987: Fire and release of radioactivity at Australian nuclear research facility 19- 20-1977: Temperature increase at Rancho Seco nuclear power plant (USA) 21-1984: Soviet nuclear submarine collides with US aircraft carrier Kitty Hawk 22-1975: Fire in reactor at Browns Ferry nuclear power plant (USA) 23- 4-1992: Incident with radiation leakage, shut-down of reactor at Leningrad nuclear power plant (Russia) 25-1992: Technical failure at Leningrad nuclear power plant (Russia) 26-1991: Refuelling accident at Wuergassen nuclear power plant (Germany) 27- 28-1979: Partial core meltdown at Three Mile Island nuclear power plant (USA) 29-1992: Failure of shut-down system at Ignalina nuclear power plant (Lithuania) 30- 31-1992: Automatic shut-down due to failure of pump system at Kalinin nuclear power plant (Russia) April 1-1989: Control rod failure at Gravelines nuclear power plant (France) 2-1979: Two workers suffer radioactive contamination at Tokaimura nuclear complex (Japan) 3-1960: Melting of fuel elements cause a release of radioactivity at the Test Reactor at Waltz Mills (USA) 4- 5- 6-1993: Explosion at the Tomsk-7 nuclear complex (Russia) -1992: Failure of automatic shut-down system at Novovoronezh nuc lear power plant (Russia) 8-1989: Soviet nuclear submarine Komsomolets sinks off Norway 9-1981: US-nuclear submarine George Washington crashes against a freighter ship 10-1963: US-nuclear submarine sinks with 123 crew members in the Atlantic 11-1950: A B-29 plane crashes in New Mexico, thirteen people killed. 12-1970: Soviet nuclear submarine sinks in the Atlantic 13-1979: Fire in the generator of the Baersbeck nuclear power plant (Sweden) 14-1970: Soviet nuclear submarine sinks with 52 crew members in Indian ocean 15-1983: Incident at Turkey Point nuclear power plant (USA) 16-1992: Technical failure of reactor shut-down system at Kola nuclear power plant (Russia) 17-1970: Incident involving a vehicle at a French nuclear test site in the South Pacific causes a plutonium spillage into the ocean. 8-1992: Technical failure during refuelling at Kola nuclear power plant (Russia) 19-1984: Technical failure at Sequoyah nuclear power plant causes spillage of radioactive coolant water. (USA) 20-1973: Thousands of cubic meters of radioactive waste flow out of Hanford nuclear weapons complex (USA) 21-1964: US-satellite disperses 1. 2. kg plutonium into the atmosphere. 22-1983: Reactor shut-down due to failure of fuel rods at Kursk nuclear power plant (Russia) 23-1991: Lost of offsite power cause technical failure at Vermont Yankee nuclear submarine (USA) 24- 25-1990: Flooding of building due to increase of coolant level at Bohunice nuclear power plant (Slovakia) 26-1986: Explosion of reactor 4 at Chernobyl nuclear power plant; the worst civilian nuclear accident to date. 27- 8-1988: Release of 5000 Curies of tritium gas from the Bruyere le Chatel military nuclear complex (France) 29-1986: US-nuclear submarine Atlanta hits the ground off Gibralta 30-1992: Breakdown of cooling system at Novovoronezh nuclear power plant (Russia) May 1-1992: Technical failure at Ignalina nuclear power plant (Lithuania) 2-1979: Technical fault at the Oyster Creek nuclear power plant triggers emergency shut-down (USA) 3-1974: Leakage at Hanford nuclear weapons complex (USA) 4-1986: Release of radiation from Hamm-Uentrop nuclear power plant (Germany) 5-1987: Pershing nuclear missile ends up in a ditch after a transport accident at Heilbronn (Germany) 6-1989: Fire of pump equipment at Bohunice nuclear power plant (Slovakia) 7-1992: Failure of emergency system at Smolensk nuclear power plant (Russia) 8-1964: First Chinese nuclear test -1992: Technical failure of cooling system at Hatch nuclear power plant (USA) 10-1965: Release of eight cubic metres of cooling water from Savannah River reprocessing plant (USA) 11-1969: Fire at Rocky Flats nuclear weapons plant causes plutonium to spontaneously ignite. (USA) 12-1984: Uncontrolled power surge at Bohunice nuclear power plant (Slovakia) 13-1992: Tube leak causes a radioactive release of 12 Curies of radioactivity from Tarapur nuclear power station (India) 14-1986: The power lines to the Palo Verde nuclear power plant are sabota ged (USA) 15- 16-1992: Reactor shut-down at Kola nuclear power plant (Russia) 17-1984: Fire on board the US-nuclear submarine Guitarro 18-1968: Accident during launch of US satellite, radioactive materials fall into ocean near Califiornia coast 19- 20-1974: First Indian nuclear test 1-1968: US-nuclear submarine Scorpion sinks off the Acores, 99 people die 22-1957: Human error causes a B-36 plane to release a nuclear bomb in New Mexico 23-1958: Accident and release of radioactivity at the Chalk River experimental reactor (Canada) 24-1968: Incident on board of Soviet nuclear submarine K- 27, 5 crew members killed by radiation release 25- 26-1990: During refuelling, five cubic meters of radioactive water spilled at the Fessenheim nuclear power plant (France) 27-1993: Reactor shut-down due to breakdown of cooling system at Kola nuclear power plant (Russia) 28-1970: Collision of the US-nuclear submarine Daniel Boone 29- 30- 31- June -1991: Failure of core cooling system at Belleville nuc lear power plant (France) 2-1992: Total failure of centralised control system at the Smolensk nuclear power plant (Russia) 3-1980: Computer fault causes full-scale alert for US Military Strategic Command 4-1989: Fire in the cables of the cooling pumps at the Bohunice nuclear power plant (Slovakia) 5-1989: 6-1994: Fire at Beloyarsk nuclear power plant (Russia) 7-1960: Fire in a BOMARC-rocket in New Jersey causes plutonium release into the atmosphere (USA) 8-1992: Failure of cooling system at Kola nuclear power plant (Russia) 9-1985: Malfunction in the cooling system at Davis Blesse nuclear power plant (USA) 10-1985: Collision of a British nuclear submarine off the coast of Florida (USA) 11-1989: Spent fuel element dropped in the storage pool and damaged at Kruemmel nuclear power plant (Germany) 12- 13- 14- 5-1992: Technical failure at Sizewell nuclear power plant (UK) 16-1988: Technical failure at Zorita nuclear power plant (Spain) 17-1967: First Chinese hydrogen nuclear bomb test 18 -1978: Release of two tons of radioactive steam from Brunsbuettel nuclear power plant (Germany) 19-1992: Leak in pipe conducting sea water to cooling system at Leningrad nuclear power plant (Russia) 20-1985 Collision of two trucks carrying nuclear bombs in Scotland (UK) 21- 22- 23-1986: Twelve people receive `slight plutonium contamination while inspecting a store room at Tokaimura nuclear complex (Japan) 24-1992: Technical failure of control system at Leningrad nuclear power plant (Russia) 25- 6-1989: Fire and reactor damage in a Soviet submarine 27-1985: Explosion and steam leakage killed 14 workers at Balakovo nuclear power plant (Russia) 28- 29-1991: Power limited due to error between actual and indicated power at Pickering nuclear power plant(Canada). 30-1983: Total loss of coolant at Embalse nuclear power plant (Argentina) July 1-1983: Technical failure causes release of Iodine-131 from Phillipsburg nuclear power plant (Germany) 2-1966: French nuclear testing in the South Paci fic begins 3-1981: Fire at North Anna nuclear power plant (USA) 4-1961: Incident on board of Soviet nuclear submarine K- 19, radiation release kills 9 crew members 5- -1959: US plane carrying nuclear weapons crashes and catches on fire 7- 8- 9-1991: Flaw in cooling system at Wurgassen nuclear power plant (Russia) 10-1991: Leakage of radiation at Bilibino nuclear power plant (Russia) 11- 12-1993: Failure of control system at Susquehanna nuclear power plant (USA) 13- 14-1992: Reactor shut-down due to failure of cooling system at Novovoronezh nuclear power plant (Russia) 15- 16-1945: First explosion of a nuclear bomb (Trinity) in New Mexico (USA) 17-1991: Reactor shut-down due to break of control system at Sendai nuclear power plant (Japan) 18-1991: Steam leakage causes reactor shut-down at Paks nuclear power plant (Hungary) 19- 0-1992: Leakage of radiation due to breakdown of cooling system at Ignalina nuclear power plant (Lithuania) 21- 22-1992: Two workers contaminated at Dampierre nuclear power plant (France) 23- 24-1989: Refuelling accident at Isar nuclear power plant (Germany) 25-1946: US nuclear test Baker causes unexpected plutonium contamination on target vessels 26-1992: Temperature rise in storage pool at Gravelines nuclear power plant (France) 27-1956: US plane crashes into nuclear ammunition storage in the UK 28-1957: US plane loses two nuclear bombs in the Atlantic 29- 30-1986: Human error causes the nuclear warhead to be knocked off a Pershing rocket (Germany) 31-1993: Refuelling machine malfunctions at the Wylfa nuclear power plant (UK) August -1983: An engineer receives a fatal radiation dose at a research reactor in Argentina 2-1987: Elevated radiation level after Soviet nuclear test 3-1983: Argentinean engineer dies from radiation dose received two days earlier 4- 5-1950: B-29 plane with nuclear weapons on board crashes; 19 people killed (USA) 6-1945: Nuclear bomb dropped on the Japanese city of Hiroshima 7- 8- 9-1945: Nuclear bomb dropped on t he Japanese city of Nagasaki 10-1985: Explosion on board a Soviet nuclear submarine 11-1988: Damage detected at Atucha nuclear power plant (Argentina) 12- 13- 14-1989: Instrumentation and control failure at Grand Gulf nuclear power plant (USA) 15-1992: 6-1991: Eight control rods show delays in emergency shut- down insertion time at Millstone Point nuclear power plant (USA) 17-1991: Automatic shut-down due to technical problems at Sendai nuclear power plant (Japan) 18-1953: First explosion of Soviet hydrogen bomb 19-1986: Flooding at the Cattenom nuclear power plant (France) 20-1974 Incident at Beznau nuclear power plant (Switzerland) 21-1980: Accident on board Soviet nuclear submarine, believed to kill at least nine crew members 22-1992: Failure of shut-down system at Novovoronezh nuclear power plant (Russia) 23- 24- 25-1984: French freighter sinks in the English Channel with 375 tonnes of uraniumhexafluoride on board 26-1989: Technical failure at Ignalina nuclear power plant (Lithu ania) 27-1990: Cable fire causes loss of control of the position of control rods at Chernobyl nuclear power plant (Ukraine) 28-1992: Fire in electro-generator at St. Alban nuclear power plant (France) 29-1949: First explosion of Soviet atomic bomb 30-1985: Fire in a barrel of radioactive waste at Karlsruhe nuclear complex (Germany) 31-1985: Fire at Fukushima nuclear power plant during routine shut-down (Japan) September 1-1993: Fire at Balakovo nuclear power plant (Russia) 2- 3-1974: Release of radioactive water at Los Alamos nuclear weapons Laboratory (USA) 4-1988: Fire at Perry nuclear power plant (USA) 5-1988: Fire at Ignalina nuclear power plant (Lithuania) 6-1991: Incident and steam leak during refueling at Barsebeck nuclear power plant (Sweden) 7- 8- 9-1989: Control rod failure at Olkiluoto nuclear power plant (Finland) 10- 1-1957: 15 kgs of plutonium catch fire at Rocky Flats nuclear weapons complex (USA) 12-1992: Leakage of radioactive water at Kola nuclear power plant (Russia) 13-1987: 249 people are contaminated in Brazil, due to handling discarded nuclear medical equipment, four people subsequently die 14-1991: Leakage at Kozloduy nucl ear power plant (Bulgaria) 15-1986: Fire on board a US plane carrying nuclear weapons 16-1990: Superphenix Fast Breeder Reactor is closed down due to technical failures (France) 17-1988: Nuclear weapons convoy road accident kills one person (UK) 18-1988: Technical failure at Stade nuclear power plant (Germany) 19-1984: Collision of a Soviet nuclear submarine 20-1977: US-nuclear submarine Ray hits the sea-bed, three crew members are injured 21-1989: Manual shut-down of WNP nuclear power plant (USA) 22-1980: Pump failure causes accidental release of radioactive water at La Hague reprocessing plant (France) 23-1969: Radioactive contamination of atmosphere during the unsuccessful launch of a Soviet spaceship. 24-1973: 35 workers at the Sellafield reprocessing plant are contaminated following a technical failure (UK) 25-1955: First Soviet underwater nuclear explosion near Novaya Zemlya (Arctic Ocean) 26- 27-1974: Soviet nuclear-capable destroyer sinks in the Black Sea 28-1990: Cables for reactor control and protection system supply overheat at Bohunice nuclear power plant (Slovakia) 29-1957: Thousands of square miles contaminated by accident at the Chelyabinsk nuclear complex (Russia) 30-1990: Failure of reactor core cooling system at Palisades nuclear power plant (USA) October -1983: Technical failure and human error cause accident at Blayas nuclear power plant(France) 2-1968: Leakage at La Hague reprocessing plant (France) 3-1952: First UK nuclear test 4-1981: Release of 300-times the normal discharge level of Iodine-131 at Sellafield reprocessing plant (UK) 5-1966: Partial core meltdown at the Fermi fast breeder reactor (USA) 6-1986: Soviet nuclear submarine sinks off the coast of Bermuda 7-1984: Emergency shut-down of Paks nuclear power plant (Hungary) 8-1985: Accidental radioactive release into the sea from Hinkley Point nuclear power station (UK) 9-1991: Technical failure at Yugno-Ukrainskaya nuclear power plant (Ukraine) 10-1957: Three tonnes of uranium catch fire at the Windscale reprocessing plant (now Sellafield UK) 11-1957: US nuclear bomber crashes in Florida and catches fire 12- 13-1977: Sea water runs into the cooling circuit of Hunterston nuclear power plant (UK) 14-1953: Fall-out from British nuclear test Totem contaminates Aborigines in the Australian desert 15-1988: French officials carry out an experiment to test the effects of releasing 7000 Curies of radioactivity 16-1964: First Chinese nuclear test 7-1969: Fuel elements melt at St Laurent des Eaux nuclear power plant (France) 18-1991: Technical failure at Zapor ozhe nuclear power plant (Ukraine) 19-1991: Offsite power failure at Smolensk nuclear power plant (Russia) 20- 21-1991: Fire on board Sceptre nuclear submarine in Scotland 22-1993: Instrumentation and Control failure at Saint Alban nuclear power plant (France) 23-1989: Failure of core cooling system at Dresdan nuclear power plant (USA) 24- 25-1991: Failure of shut-down system during refuelling at Novovoronezh nuclear power plant (Russia) 26-1991: Incident during refueling at Vogtle nuclear power plant (USA) 27-1991: Technical failure of shut-down system at Zaporozhe nuclear power plant (Ukraine) 28- 29-1991: Technical failure causes automatic shut-down at Kalinin nuclear power plant (Russia) 30-1991: 1-1986: US-nuclear submarine Augusta involved in collision November 1-1992: Cracks in cooling system equipment at Brunsbuttel nuclear power plant (Germany) 2-1982: Nuclear missile transporter crashes killing one person and injuring two others (Germany) 3-1990: Failure of core cooling eq uipment at Doel nuclear power plant (Belgium) 4-1970: Explosion on board a nuclear-capable US-destroyer kills two sailors 5-1967: UK nuclear-powered ballistic missile submarine `HMS Repulse runs aground 30 minutes after its launch 6- 7-1967: Release of radioactivity at Grenoble nuclear power plant (France) 8- 9-1955: Core meltdown at EBR fast breeder reactor (USA) 10- 1-1988: Accident during refueling on board of Soviet nuclear powered ice-breaker Lenin 12-1993: London Convention bans the dumping of nuclear waste into the sea 13-1974: Karen Silkwood, a worker at a US nuclear plant, dies mysteriously on her way to hand important documents to a Trade Union Official and a journalist 14-1989: Breakdown of fuel rod control system at Oconee nuclear power plant (USA) 15-1989: Fire on board US-nuclear submarine Finback 16-1983: Sellafield reprocessing plant discharges highly radioactive wastes directly into the sea (UK) 17- 18-1991: Reactor shut-down due to technical failure at Balakovo nuc lear power plant (Russia) 19-1980: US nuclear-missile almost launched during a drill exercise. 20-1989: Fire in turbine equipment at Kozloduy nuclear power plant (Bulgaria) 21- 22- 3-1991: Leak of 190,000 litres of water from cooling system, reactor shut-down at Oconee nuclear power plant (USA) 24-1989: Technical failure nearly causes core meltdown at Greifswald nuclear power plant (Germany) 25-1991: Failure of cooling system causes automatic reactor shut-down at Kursk nuclear power plant (Russia) 26-1958: B-47 plane catches fire, destroying one nuclear weapon (USA) 27-1991: Disfunction of automatic shut-down system at Bilibino nuclear power plant (Russia) 28-1991: Failure of control system causes reactor shut- down at Kursk nuclear power plant (Russia) 29-1982: US nuclear submarine collides with US-destroyer 30-1975: 1. 5 million Curies released from Leningrad nuclear power plant (Russia) December -1991: Technical failure at Beloyarsk nuclear power plant (Russia) 2-1949: US experim ent Green Run contaminates communities up to 70 miles away from the Hanford nuclear weapons complex (USA) 3-1988: Explosion at the Burghfield Atomic Weapons Establishment (UK) 4-1990: 2 workers irradiated during refuelling at Blayais nuclear power plant (France) 5-1965: Plane crashes with nuclear bombs on board off the coast of Japan 6-1991: Failure of control system during refuelling causes reactor shut-down at Smolensk nuclear power plant (Russia) 7-1991: Failure of cooling system at Kola nuclear power plant (Russia) 8-1995: Fire due to leakage of sodium coolant from Monju fast breeder reactor, Japanese nuclear industry attempts to cover up full extent of accident, reactor shut-down 9-1986: Explosion at Surry nuclear power plant, four people killed (USA). 0-1991: Failure of turbo-generator causes reactor shut- down at Balakovo nuclear power plant (Russia) 11-1991: Human error causes failure of automatic reactor shut-down equipment at Kola nuclear power plant (Russia) 12-1952: Worl ds first major nuclear reactor disaster, Chalk River experimental reactor (Canada) 13-1988: Four of the eight emergency installations discovered out of order at Brokdorf nuclear power plant (Germany) 14-1991: Technical failure causes automatic shut-down at Balakovo nuclear power plant (Russia) 15-1991: Technical failure at Kalinin nuclear power plant (Russia) 16-1991: Technical failure at Kola nuclear power plant (Russia) 17-1987: Severe incident at Biblis nuclear power plant (Germany) 18-1984: Fire at Kalinin nuclear power plant (Russia) 19-1980: Plutonium transport accident in the USA 0-1990: Control element discovered damaged at Novovoronezh nuclear power plant (Russia) 21-1991: Radiation leakage at Kolskaya nuclear power plant (Russia) 22-1987: Accidental release of 50 tonnes of water from Atucha nuclear power plant (Argentina) 23-1988: Two control rods jammed at Blayais nuclear power plant (France) 24-1991: Reactor shut-down due to technical failure at Kalinin nuclear power pla nt (Russia) 25-1992: Radioactive water leakage at Beloyarsk nuclear power plant (Russia) 26- 27-1991: Automatic shut-down Balakovo nuclear power plant (Russia) 28-1990: Incident and radiation leakage at Leningrad nuclear power plant (Russia) 29- 30-1988: Reactor shut-down due to failure of control equipment at Pilgrim nuclear power plant (USA) 31-1978: Fire and loss of reactor control, 8 workers irradiated at Beloyarsk nuclear power plant (Russia) Nuclear and Chemical Accidents Though nuclear power is a good source of energy and is generally not a threat, there have been instances when security measures have failed. Nuclear meltdowns can cause dangerous radiation to escape into the surrounding environment. 1952 Dec. 12, Chalk River, nr. Ottawa, Canada: a partial meltdown of the reactors uranium fuel core resulted after the accidental removal of four control rods. Although millions of gallons of radioactive water accumulated inside the reactor, there were no injuries. 1953 Love Canal, nr. Niagara Falls, N. Y. : was destroyed by waste from chemical plants. By the 1990s, the town had been cleaned up enough for families to begin moving back to the area. 1957 Oct. 7, Windscale Pile No. 1, north of Liverpool, England: fire in a graphite-cooled reactor spewed radiation over the countryside, contaminating a 200-square-mile area. South Ural Mountains: explosion of radioactive wastes at Soviet nuclear weapons factory 12 mi from city of Kyshtym forced the evacuation of over 10,000 people from a contaminated area. No casualties were reported by Soviet officials. 1976 nr. Greifswald, East Germany: radioactive core of reactor in the Lubmin nuclear power plant nearly melted down due to the failure of safety systems during a fire. 1979 March 28, Three Mile Island, nr. Harrisburg, Pa. : one of two reactors lost its coolant, which caused overheating and partial meltdown of its uranium core. Some radioactive water and gases were released. This was the worst accident in U. S. nuclear-reactor history. 1984 Dec. , Bhopal, India: toxic gas, methyl isocyanate, seeped from Union Carbide insecticide plant, killing more than 2,000 and injuring about 150,000. 1986 April 26, Chernobyl, nr. Kiev, Ukraine: explosion and fire in the graphite core of one of four reactors released radioactive material that spread over part of the Sov iet Union, eastern Europe, Scandinavia, and later western Europe. 31 claimed dead. Total casualties are unknown. Worst such accident to date. 1987 Sept. 18, Goiania, Brazil: 244 people contaminated with cesium-137 from a cancer-therapy machine that had been sold as scrap. Four people died in worst radiation disaster in Western Hemisphere. 1999 Sept. 0, Tokaimura, Japan: uncontrolled chain reaction in a uranium-processing nuclear fuel plant spewed high levels of radioactive gas into the air, killing two workers and seriously injuring one other. 2004 Aug. 9, Mihama, Japan: nonradioactive steam leaked from a nuclear power plant, killing four workers and severely burning seven others. 2007 July 17, Kashiwazaki, Japan: radiation leaks, burst pipes, and fires at a major nuclear power plant followed a 6. 8 magnitude earthquake near Niigata. Japanese officials, frustrated at the plant operators delay in reporting the damage, closed the plant a week later until its safety could be confirmed. Further investigation revealed that the plant had unknowingly been built directly on top of an active seismic fault. 2008 February 7, Port Wentworth, Georgia: an explosion fueled by combustible sugar dust killed 13 people and injured several others at the Imperial Sugar plant near Savannah. Information Please ® Database,  © 2007 Pearson Education, Inc. All rights reserved. Droughts and Heat Waves Disasters Fires and Explosions Read more: Nuclear and Chemical Accidents — Infoplease. com http://www. infoplease. com/ipa/A0001457. html#ixzz1EmtUxatg Disasters: Nuclear Accidents ________________________________________ ________________________________________ Of all the environmental disaster events that humans are capable of causing, nuclear disasters have the greatest damage potential. The radiation release associated with a nuclear disaster poses significant acute and chronic risks in the immediate environs and chronic risk over a wide geographic area. Radioactive contamination, which typically becomes airborne, is long-lived, with half-lives guaranteeing contamination for hundreds of years. Concerns over potential nuclear disasters center on nuclear reactors, typically those used to generate electric power. Other concerns involve the transport of nuclear waste and the temporary storage of spent radioactive fuel at nuclear power plants. The fear that terrorists would target a radiation source or create a dirty bomb capable of dispersing radiation over a populated area was added to these concerns following the 2001 terrorist attacks on New York City and Washington, D. C. Radioactive emissions of particular concern include strontium-90 and cesium-137, both having thirty-year-plus half-lives, and iodine-131, having a short half-life of eight days but known to cause thyroid cancer. In addition to being highly radioactive, cesium-137 is mistaken for potassium by living organisms. This means that it is passed on up the food chain and bioaccumulated by that process. Strontium-90 mimics the properties of calcium and is deposited in bones where it may either cause cancer or damage bone marrow cells. The Chernobyl Disaster Concern became reality at 1:23 A. M. on April 25, 1986, when the worst civil nuclear catastrophe in history occurred at the nuclear power plant at Chernobyl, Soviet Union (which is now in Ukraine). More than thirty people were killed immediately. The radiation release was thirty to forty times that of the atomic bombs dropped on Japan during World War II. Hundreds of thousands of people were ultimately evacuated from the most heavily contaminated zone surrounding Chernobyl. Radiation spread to encompass almost all of Europe and Asia Minor; the world first learned of the disaster when a nuclear facility in Sweden recorded abnormal radiation levels. Chernobyl had four RBMK-type reactors. These reactors suffer from instability at low power and are susceptible to rapid, difficult-to-control power increases. The accident occurred as workers were testing reactor number four. The test was being conducted improperly; as few as six control rods were in place despite orders stating that a minimum of thirty rods were necessary to maintain control, and the reactors emergency cooling system had been shut down as part of the test. An operator error caused the reactors power to drop below specified levels, setting off a catastrophic power surge that caused fuel rods to rupture, triggering explosions that first destroyed the reactor core and then blew apart the reactors massive steel and concrete containment structure. The health impacts of the Chernobyl explosion will never be fully known. It is estimated that some three million people still live in contaminated areas and almost ten housand people still live in Chernobyl itself. The plant itself was not fully shut down until nearly fifteen years after the disaster. Studies by the Belarus Ministry of Health, located approximately eighty miles south of Chernobyl, found that rates of thyroid cancer began to soar in contaminated regions in 1990, four years after the radiation release. Gomel, Belarus, the most highly contaminated region studied, reported thirty-eight cases in 1991. Gomel normally recorded only one to two cases per year. Health officials in Turkey, 930 miles to the south, reported that leukemia rates are twelve times higher than before the Chenobyl accident. Three Mile Island The thriller China Syndrome, which warned that a nuclear power plant meltdown would blow a hole through the earth all the way to China and render an area the size of Pennsylvania permanently uninhabitable had been playing for eleven days when, at 4:00 am on March 28, 1979, Reactor #2 at the Three Mile Island (TMI) nuclear power plant suffered a partial meltdown. The plant was just downriver from Harrisburg, Pennsylvania. Film story, reality, and perception all interplayed to create near national panic. The accident occurred sequentially. A minor problem caused the temperature of the primary coolant to rise. In one second, the reactor shut down but a relief valve that was supposed to close after ten seconds remained open. Plant instrumentation showed operators that a close valve signal had been sent. There was no instrumentation to tell them the valve itself was still open. The reactors primary coolant drained away and the reactor core suffered serious damage. Fuel rods were damaged, leaking radioactive material into the cooling water and a high temperature chemical reaction created bubbles of hydrogen gas. One of these bubbles burned, creating fears that a larger hydrogen bubble would explode, possibly breaching the plants containment structure. Some gases were purposefully vented into the atmosphere. It took nearly a full month the bring the reactor into cold shutdown status. That said, there was never danger of a massive explosion and hundreds of readings taken by the Pennsylvania Department of Environmental Resources showed almost no iodine, and all readings were far below health limits. There was, however, widespread panic including a unordered mass evacuation. The greatest problem at TMI was a total failure of communication. Internal radioactivity levels, for example, were reported as ambient (outdoor) air readings. The many health studies following TMI showed no evidence of abnormal cancer rates. For eighteen years, the Pennsylvania Department of Health maintained a registry of 30,000 people who lived within five miles of TMI; it Acivil defense worker is using Geiger counter to check radiation level near a school building following the accidental radiation leak from the nearby Three Mile Island nuclear power plant. Schoolchildren are being evacuated via bus. ( ©Wally McNamee/Corbis. Reproduced by permission. ) found no evidence on unusual health trends. TMIs only health effect was psychological stress related to the accident. While there were few long-term health effects, there is no doubt that the accident at TMI permanently changed both the nuclear industry and the Nuclear Regulatory Commission (NRC). Public fear and distrust increased, the NRC notes in a fact sheet on TMI, Regulations and oversight became broader and more robust, and management of the plants was scrutinized more carefully. Nuclear Submarines On August 12, 2000, an explosion in a torpedo tube sank the giant Russian nuclear submarine Kursk and its crew of 118 in the Barents Sea. Russian officials described the sinking as a catastrophe that developed at lightning Two cooling towers at the Three Mile Island nuclear plant. ( ©W. Cody/Corbis. Reproduced by permission. ) speed. A week later, divers opened the rear hatch of the sub but found no survivors. It took salvagers two years, but the Kursk and her two nuclear reactors was raised. The Kursk was the sixth nuclear submarine to have sunk since 1963. The others all came to rest on the oc ean floor at depths of more than 4,500 feet, far below where most marine life lives. They include two former Soviet submarines—one that sank east of Bermuda in 1986 and another that went down in the Bay of Biscay in 1970—and two U. S. nuclear submarines—the U. S. S. Thresher and U. S. S. Scorpion —which sank in the 1960s at the height of the Cold War. U. S. Navy officials report there is little likelihood of radioactive release from the U. S. ships. Reactor fuel elements in American submarines are made of materials that are extremely corrosion resistant, even in sea water. The protective cladding on the fuel elements corrodes only a few millionths of an inch per year, meaning the reactor core could remain submerged in sea water for centuries without releases of fission products while the radioactivity decays. Comprehensive deep ocean radiological monitoring operations were conducted at the Thresher site in 1965, 1977, 1983, and again in 1986. None of the samples obtained showed any evidence of release of radioactivity from the reactor fuel elements. Internet Resources Nave, C. R. Hyper Physics. Available from http://hyperphysics. phy-astr. gsu. edu/hbase/hframe. html . Public Citizen. Decades of Delay: The NRCs Failure to Stockpile Potassium Iodide Protect the Public Health and Safety Available from http://www. citizen. org/cmep/energy_enviro_nuclear/nuclear_power_plants reactor_safety/articles. cfm? ID=4433 . Subnet. USS Thre sher (SSN-593). Available from http://www. subnet. com/fleet/ssn593. htm . U. S. Nuclear Regulatory Commission. Fact Sheet on the Accident at the Chernobyl Nuclear Power Plant. Available from http://www. nrc. gov/reading-rm/doc-collections/fact-sheets/fschernobyl. tml . U. S. Nuclear Regulatory Commission. Fact Sheet on the Accident at Three Mile Island. Available from http://www. nrc. gov/reading-rm/doc-collections/fact-sheets/3mile-isle. h ml . Richard M. Stapleton Fears of terrorist attacks on nuclear power plants have prompted state and local health offices to distribute supplies of potassium iodide pills, known as KI, to be taken in the event of a release of radioactive materials. KI blocks the intake of radioactive iodine by the thyroid and helps prevent thyroid cancer. The pills were provided by the Nuclear Regulatory Commission. ________________________________________ ________________________________________ Read more: Disasters: Nuclear Accidents water, effects, environmental, history, world, power, life, health, The Chernobyl Disaster, Three Mile Island, Nuclear Submarines http://www. pollutionissues. om/Co-Ea/Disasters-Nuclear-Accidents. html#ixzz1Emu1kkxC Major Nuclear Power Plant Accidents December 12, 1952 A partial meltdown of a reactors uranium core at the Chalk River plant near Ottawa, Canada, resulted after the accidental removal of four control rods. Although millions of gallons of radioactive water poured into the reactor, t here were no injuries. October 1957 Fire destroyed the core of a plutonium-producing reactor at Britains Windscale nuclear complex since renamed Sellafield sending clouds of radioactivity into the atmosphere. An official report said the leaked radiation could have caused dozens of cancer deaths in the vicinity of Liverpool. Winter 1957-58 A serious accident occurred during the winter of 1957-58 near the town of Kyshtym in the Urals. A Russian scientist who first reported the disaster estimated that hundreds died from radiation sickness. January 3, 1961 Three technicians died at a U. S. plant in Idaho Falls in an accident at an experimental reactor. July 4, 1961 The captain and seven crew members died when radiation spread through the Soviet Unions first nuclear-powered submarine. A pipe in the control system of one of the two reactors had ruptured. October 5, 1966 The core of an experimental reactor near Detroit, Mich. , melted partially when a sodium cooling system failed. January 21, 1969 A coolant malfunction from an experimental underground reactor at Lucens Vad, Switzerland, releases a large amount of radiation into a cave, which was then sealed. December 7, 1975 At the Lubmin nuclear power complex on the Baltic coast in the former East Germany, a short-circuit caused by an electricians mistake started a fire. Some news reports said there was almost a meltdown of the reactor core. March 28, 1979 Near Harrisburg, Pennsylvania, Americas worst nuclear accident occurred. A partial meltdown of one of the reactors forced the evacuation of the residents after radioactive gas escaped into the atmosphere. February 11, 1981 Eight workers are contaminated when more than 100,000 gallons of radioactive coolant fluid leaks into the contaminant building of the Tennessee Valley Authoritys Sequoyah 1 plant in Tennessee. April 25, 1981 Officials said around 45 workers were exposed to radioactivity during repairs to a plant at Tsuruga, Japan. April 26, 1986 The worlds worst nuclear accident occurred after an explosion and fire at the Chernobyl nuclear power plant. It released radiation over much of Europe. Thirty-one people died iin the immediate aftermath of the explosion. Hundreds of thousands of residents were moved from the area and a similar number are belived to have suffered from the effects of radiation exposure. March 24, 1992 At the Sosnovy Bor station near St. Petersburg, Russia, radioactive iodine escaped into the atmosphere. A loss of pressure in a reactor channel was the source of the accident. November 1992 In Frances most serious nuclear accident, three workers were contaminated after entering a nuclear particle accelerator in Forbach without protective clothing. Executives were jailed in 1993 for failing to take proper safety measures. November 1995 Japans Monju prototype fast-breeder nuclear reactor leaked two to three tons of sodium from the reactors secondary cooling system. March 1997 The state-run Power Reactor and Nuclear Fuel Development Corporation reprocessing plant at Tokaimura, Japan, contaminated at least 35 workers