Chernobyl all-time worst nuclear accident | Human World | EarthSky Chernobyl all-time worst nuclear accident By EarthSky Voices in Human World | April 26, 2016 The meltdown at the Chernobyl Nuclear Power Plant on April 26, 1986 exposed 572 million people to radiation. It was far worse than the 2011 Fukushima accident. After one reactor at the Chernobyl nuclear power plant caught fire and exploded in 1986, the whole site was encased in a concrete sarcophagus. Photo: Vladimir Repik/Reuters By Timothy J. Jorgensen , Georgetown University The 1986 Chernobyl and 2011 Fukushima nuclear power plant accidents both share the notorious distinction of attaining the highest accident rating on the International Atomic Energy Agency (IAEA) scale of nuclear accidents . No other reactor incident has ever received this Level 7 “major accident” designation in the history of nuclear power. Chernobyl and Fukushima earned it because both involved core meltdowns that released significant amounts of radioactivity to their surroundings. Both of these accidents involved evacuation of hundreds of thousands of residents.

Both still have people waiting to return to their homes. And both left a legacy of large-scale radioactive contamination of the environment that will persist for years to come, despite ongoing cleanup efforts. So the tendency is to think of these accidents as similar events that happened in different countries, 25 years apart. But the IAEA scale isn’t designed to measure public health impact. In terms of health ramifications, these two nuclear accidents were not even in the same league. While Fukushima involved radioactivity exposures to hundred of thousands of people, Chernobyl exposed hundreds of millions. And millions of those received substantially more exposure than the people of Fukushima. On the occasion of the 30th anniversary of the April 26, 1986 Chernobyl accident in Ukraine, we do well to reflect on the health burden it caused – and compare it with what we expect to see from Japan’s Fukushima nuclear accident. As I report in my book “ Strange Glow: The Story of Radiation ,” from a public health standpoint, there’s really no comparison between the two events. Chernobyl reactor No. 4 building.

Photo credit: Vadim Mouchkin, IAEA/Flickr Higher doses of radiation, more health harm Chernobyl was by far the worst reactor accident of all time. A total of 127 reactor workers, firemen and emergency personnel on site sustained radiation doses sufficient to cause radiation sickness (over 1,000 mSv); some received doses high enough to be lethal (over 5,000 mSv). Over the subsequent six months, 54 died from their radiation exposure . And it’s been estimated that 22 of the 110,645 cleanup workers may have contracted fatal leukemias over the next 25 years. In contrast, at Fukushima, there were no radiation doses high enough to produce radiation sickness, even among the reactor core workers. Two Fukushima workers who had leaky respirators received effective doses of 590 mSv and 640 mSv . That’s above the Japanese occupational limit for conducting lifesaving rescue work (250 mSv), but still below the threshold for radiation sickness (1,000 mSv).

Due to their exposure, the two workers’ lifetime cancer risks will increase about 3 percent (from the 25 percent background cancer risk rate to about 28 percent), but they are unlikely to experience other health consequences. Beyond just the plant workers, over 572 million people among 40 different countries got at least some exposure to Chernobyl radioactivity. (Neither the United States nor Japan was among the exposed countries.) It took two decades to fully assess the cancer consequences to these people. Finally, in 2006, an international team of scientists completed a comprehensive analysis of the dose and health data and reported on the cancer deaths that could be attributed to Chernobyl radioactivity. Their detailed analysis included countrywide estimates of individual radiation doses in all 40 exposed countries, and regionwide estimates for the most highly contaminated regions of the most highly contaminated countries (Belarus, Russian Federation and Ukraine). Using statistical models, the scientists predicted a total of 22,800 radiation-induced cancers, excluding thyroid cancers, among this group of 572 million people.

Thyroid cancer warranted separate special scrutiny, as we will discuss presently; this hormonally important gland is uniquely affected by a specific radioactive isotope, iodine-131. So that’s 22,800 non-thyroid cancers in addition to the approximately 194 million cancer cases that would normally be expected in a population of that size, even in the absence of a Chernobyl accident. The increase from 194,000,000 to 194,022,800 is a 0.01 percent rise in the overall cancer rate. That’s too small to have any measurable impact on the cancer incidence rates for any national cancer registries, so these predicted values will likely remain theoretical. A doctor checks the thyroid glands of Belarussian children. Photo credit: Reuters Chernobyl’s iodine-131 thyroid effects far worse Unfortunately, at Chernobyl, the one type of cancer that could have easily been prevented was not. The population surrounding Chernobyl was not warned that iodine-131 – a radioactive fission product that can enter the food chain – had contaminated milk and other locally produced agricultural products.

Consequently, people ate iodine-131-contaminated food, resulting in thyroid cancers. For the local population, iodine-131 exposure was a worst-case scenario because they were already suffering from an iodine-deficient diet ; their iodine-starved thyroids sucked up any iodine that became available. This extremely unfortunate situation would not have happened in countries such as the United States or Japan, where diets are richer in iodine. Thyroid cancer is rare, with a low background incidence compared to other cancers. So excess thyroid cancers due to iodine-131 can be more readily spotted in cancer registries. And this, in fact, has been the case for Chernobyl. Beginning five years after the accident, an increase in the rate of thyroid cancers started and continued rising over the following decades. Scientists estimate that there will ultimately be about 16,000 excess thyroid cancers produced as a result of iodine-131 exposure from Chernobyl. At Fukushima, in contrast, there was much less iodine-131 exposure. The affected population was smaller, local people were advised to avoid local dairy products due to possible contamination and they did not have iodine-deficient diets.

Consequently, typical radiation doses to the thyroid were low. Iodine-131 uptake into the thyroids of exposed people was measured and the doses were estimated to average just 4.2 mSv for children and 3.5 mSv for adults – levels comparable to annual background radiation doses of approximately 3.0 mSv per year. Contrast this to Chernobyl, where a significant proportion of the local population received thyroid doses in excess of 200 mSv – 50 times more – well high enough to see appreciable amounts of excess thyroid cancer. So at Fukushima, where iodine-131 doses approached background levels, we wouldn’t expect thyroid cancer to present the problem that it did at Chernobyl. Nevertheless, there has already been one report that claims there is an increase in thyroid cancer among Fukushima residents at just four years post-accident. That’s earlier than would be expected based on the Chernobyl experience . And the study’s design has been criticized as flawed for a number of scientific reasons, including the comparison methods used . Thus, this report of excess thyroid cancers must be considered suspect until better data arrive .

Health effects of the Chernobyl disaster are still felt 30 years on. Photo credit: Garanich/Reuters Chernobyl has no comparison In short, Chernobyl is by far the worst nuclear power plant accident of all time. It was a totally human-made event – a “safety” test gone terribly awry – made worse by incompetent workers who did all the wrong things when attempting to avert a meltdown. Fukushima in contrast, was an unfortunate natural disaster – caused by a tsunami that flooded reactor basements – and the workers acted responsibly to mitigate the damage despite loss of electrical power. April 26, 1986 was the darkest day in the history of nuclear power. Thirty years later, there is no rival that comes even close to Chernobyl in terms of public health consequences; certainly not Fukushima. We must be vigilant to ensure nothing like Chernobyl ever happens again. We don’t want to be “celebrating” any more anniversaries like this one. Timothy J.

Jorgensen , Director of the Health Physics and Radiation Protection Graduate Program and Associate Professor of Radiation Medicine, Georgetown University 10 Worst Nuclear Disasters in History - YouTube 10 Worst Nuclear Disasters in History Want to watch this again later? Sign in to add this video to a playlist. Need to report the video? Sign in to report inappropriate content. The interactive transcript could not be loaded. Loading... Rating is available when the video has been rented. This feature is not available right now. Please try again later. Published on Mar 29, 2016 The world's biggest & most powerful nuclear disasters of all time! Nothing compares to these nuclear accidents that devastated places like Fukushima, Chernobyl, & Windscale. Today's video was done in collaboration with World 5 List! Check out their video on “The Most Radioactive Sites in the World” by clicking here: And don't forget to subscribe to their channel by clicking here: Subscribe to They Will Kill You for new videos: Full image attributions available here: Number 10: Myak Located in northeastern Russia, Mayak is an industrial complex that experienced an accident in 1957 known as the Kyshtym Disaster.

During this disaster, an explosion caused 100 tons of radioactive waste to be released into the environment, exposing more than 400,000 people to radiation. The International Nuclear Event Scale measured it as a 6, meaning it was the third worst nuclear disaster of all time. The only two that were worse were Fukushima & Chernobyl. As it was operated by the Soviet Union, the activities at Myak were top secret & the public was not immediately informed about its happenings. A week after the explosion, 10,000 people from the surrounding area were evacuated, though they still did not know what was going on. While it is not entirely clear how many health issues can be attributed to this incident, some believe that as many as around 8,000 people died over a 30-year span. Others estimates count anywhere between 50 to 200 fatalities. But even before the accident actually took place, dangerous material was released into a nearby river that also subjected the area to high radioactive exposure. Other accidents at the complex have put humans & the environment at risk as well.

From 1953 till 2000, dozens of minor accidents as well as two major ones occurred at Myak. At one point, a dried up polluted lake called Lake Karachay began releasing radioactive particles into surrounding bodies of water during a heavy rainstorm in 1967. Heavy winds spread dust & radioactive material from the lake over to the town of Ozyorsk. Number 9: The Santa Susana Field Laboratory Located in the Simi Valley of Southern California, the Santa Susana Field Laboratory was used from 1949 until 2006. The complex had many uses over the years. It was used to research government-sponsored liquid metals, to develop liquid propellant rocket engines for NASA, & to house nuclear reactors. Over the years, four of the ten nuclear reactors experienced accidents. In July, 1959, one of the worst nuclear reactor accidents in U.S. history occurred at the site. After the site saw a nuclear meltdown, it released what is believed to be an enormous amount of radioactivity. The exact amount was never specified. Some estimates say that it was as much as 458 times the amount released during the Three Mile Island disaster of 1979.

Earlier that year, the same AE6 Nuclear Reactor was leaking fission gas, which was likely to be the cause of the meltdown that occurred months later. In 2006, scientists & researchers concluded that contamination from the accidents as well as sodium burn pits—which were used to clean sodium contaminated objects—might have been responsible for as many as 300 to 1,8000 cancer deaths. Number 8: Three Mile Island Mentioned earlier, this accident garnered much national attention & occurred in 1979 at the Three Mile Island Nuclear Generating Station in Dauphin County, Pennsylvania. On March 28th, 1979, a mechanical failure at the site resulted in nuclear reactor coolant being leaked from one of the reactors. When all was said & done, a large amount of radioactive gases & iodine was released into the environment. The exact amount has not been explicitly made known. The extent of the damage was so bad that initially, all pregnant women & young children within a five-mile radius of Three Mile Island were evacuated. It eventually extended to a 20-mile & ultimately a 30-mile radius.

About 140,000 of the 635,000 people in the area chose to evacuate, & many of these folks returned within weeks of the accident. An investigation found that the accident occurred due to human miscalculations & a valve malfunction. The cleanup effort lasted four years, from 1979 till 1993. Aside from the health & environmental toll the accident took, it also badly damaged the development of nuclear energy. Plans to build 51 nuclear reactors were canceled & it wasn’t until 2012 that another nuclear power plant was authorized for construction. Category 11 Worst Nuclear Accidents | TakePart 11 Worst Nuclear Accidents A snapshot of the most frightening nuclear meltdowns, contaminations, and explosions in history. May 23, 2012 Share 11 Nuclear Disasters Since the Manhattan Project began in the late 1930s, nations have experimented with nuclear power and fuel refinement. Unfortunately, there have been quite a few mishaps, accidents and tragedies.

The International Atomic Energy Agency (IAEA) classifies these disasters on the International Nuclear and Radiological Event Scale , a seven-point scale ranging from one (an "anomaly") to seven (an "major accident"). We have compiled the worst 11. (Photo: Superstock/Getty Images) Windscale Pile, Great Britain—INES Level 5, 1957 Britain experimented with a side-loading, air-and-graphite cooled reactor in its race to build an atomic bomb. The reactor caught fire because the technicians had little experience handling superheated graphite. Failing to put out the fire with carbon dioxide, the reactor's technicians were eventually successful in killing the flames with water, according to one of the physicists . Over 16 tons of uranium fuel remains in the reactor; it will be decontaminated in 2037. (Photo: Gamma-Keystone/Getty Images) Chernobyl, Ukraine—INES Level 7, 1986 The Chernobyl disaster caused 53 direct deaths, and countless chronic illnesses. Technicians were conducting experimental shutdowns when an unexpected power surge caused the containment vessel to burst and the building to explode. Radioactive clouds quickly spread across Europe.

The estimated cost of containing the disaster was $235 billion. In 2011, Igor Gramotkin, former director of the Chernobyl Atomic Energy Station, claimed that it would take 20,000 years for the 19 miles surrounding Chernobyl to be habitable. (Photo: Gamma Rapho/Getty Images) Saint Laurent des Eaux, France—INES Level 4, 1980 In a graphite-annealing incident, the reactor at Saint Laurent experienced a brief heat excursion. France’s worst accident ever may have caused traces of plutonium to be left in the Loire River. (Photo: Alain Jocard/Getty Images) 3 Mile Island, Pennsylvania—INES Level 5, 1979 According to the Nuclear Regulatory Commission , the worst nuclear accident in U.S. history occurred when a stuck relief valve, caused by control flaws and human error, allowed tons of reactor coolant to escape, thereby resulting in a partial meltdown. Forty thousand gallons of contaminated waste spilled into the Susquehanna River near Harrisburg, Pennsylvania.

(Photo: Jeff Fusco/Getty Images) Jaslovske Bohunice, Slovakia—INES Level 4, 1977 According to the World Nuclear Association , Slovakian scientists failed to properly operate this reactor by forgetting to take out contaminated silica packs—thereby causing fuel rods to overheat. In attempting to cool the machine, the entire reactor was contaminated. It will be fully decontaminated in 2033. (Photo: Bloomberg/Getty Images) Chalk River, Canada—INES Level 5, 1952 The first nuclear reactor located outside of the U.S. experienced an accident two years after opening. A combination of mechanical problems and human error led to a power surge and a loss of reactor coolant. This resulted in a hydrogen explosion in the reactor. The reactor vessel roof was blown off and 4,500 tons of radioactive water pooled in the basement.

This date in science: Chernobyl worst nuclear accident of all time – Witches Of The Craft® This date in science: Chernobyl worst nuclear accident of all time This date in science: Chernobyl worst nuclear accident of all time The meltdown at the Chernobyl Nuclear Power Plant on April 26, 1986 exposed 572 million people to radiation. It was far worse than the 2011 Fukushima accident. By Timothy J. Jorgensen , Georgetown University The 1986 Chernobyl and 2011 Fukushima nuclear power plant accidents both share the notorious distinction of attaining the highest accident rating on the International Atomic Energy Agency (IAEA) scale of nuclear accidents. No other reactor incident has ever received this Level 7 “major accident” designation in the history of nuclear power. Chernobyl and Fukushima earned it because both involved core meltdowns that released significant amounts of radioactivity to their surroundings. Both of these accidents involved evacuation of hundreds of thousands of residents. Both still have people waiting to return to their homes. And both left a legacy of large-scale radioactive contamination of the environment that will persist for years to come, despite ongoing cleanup efforts.

So the tendency is to think of these accidents as similar events that happened in different countries, 25 years apart. But the IAEA scale isn’t designed to measure public health impact. In terms of health ramifications, these two nuclear accidents were not even in the same league. While Fukushima involved radioactivity exposures to hundred of thousands of people, Chernoby l exposed hundreds of millions. And millions of those received substantially more exposure than the people of Fukushima. On the occasion of the 30th anniversary of the April 26, 1986 Chernobyl accident in Ukraine, we do well to reflect on the health burden it caused – and compare it with what we expect to see from Japan’s Fukushima nuclear accident. As I report in my book “Strange Glow: The Story of Radiation,” from a public health standpoint, there’s really no comparison between the two events. Higher doses of radiation, more health harm Chernobyl was by far the worst reactor accident of all time.

A total of 127 reactor workers, firemen and emergency personnel on site sustained radiation doses sufficient to cause radiation sickness (over 1,000 mSv); some received doses high enough to be lethal (over 5,000 mSv). Over the subsequent six months, 54 died from their radiation exposure. And it’s been estimated that 22 of the 110,645 cleanup workers may have contracted fatal leukemias over the next 25 years. In contrast, at Fukushima, there were no radiation doses high enough to produce radiation sickness, even among the reactor core workers. Two Fukushima workers who had leaky respirators received effective doses of 590 mSv and 640 mSv. That’s above the Japanese occupational limit for conducting lifesaving rescue work (250 mSv), but still below the threshold for radiation sickness (1,000 mSv). Due to their exposure, the two workers’ lifetime cancer risks will increase about 3 percent (from the 25 percent background cancer risk rate to about 28 percent), but they are unlikely to experience other health consequences.

Beyond just the plant workers, over 572 million people among 40 different countries got at least some exposure to Chernobyl radioactivity. (Neither the United States nor Japan was among the exposed countries.) It took two decades to fully assess the cancer consequences to these people. Finally, in 2006, an international team of scientists completed a comprehensive analysis of the dose and health data and reported on the cancer deaths that could be attributed to Chernobyl radioactivity. Their detailed analysis included countrywide estimates of individual radiation doses in all 40 exposed countries, and regionwide estimates for the most highly contaminated regions of the most highly contaminated countries (Belarus, Russian Federation and Ukraine). Using statistical models, the scientists predicted a total of 22,800 radiation-induced cancers, excluding thyroid cancers, among this group of 572 million people. Thyroid cancer warranted separate special scrutiny, as we will discuss presently; this hormonally important gland is uniquely affected by a specific radioactive isotope, iodine-131.

So that’s 22,800 non-thyroid cancers in addition to the approximately 194 million cancer cases that would normally be expected in a population of that size, even in the absence of a Chernobyl accident. The increase from 194,000,000 to 194,022,800 is a 0.01 percent rise in the overall cancer rate. That’s too small to have any measurable impact on the cancer incidence rates for any national cancer registries, so these predicted values will likely remain theoretical. Chernobyl’s iodine-131 thyroid effects far worse Unfortunately, at Chernobyl, the one type of cancer that could have easily been prevented was not. The population surrounding Chernobyl was not warned that iodine-131 – a radioactive fission product that can enter the food chain – had contaminated milk and other locally produced agricultural products. Consequently, people ate iodine-131-contaminated food, resulting in thyroid cancers.

For the local population, iodine-131 exposure was a worst-case scenario because they were already suffering from an iodine-deficient diet; their iodine-starved thyroids sucked up any iodine that became available. This extremely unfortunate situation would not have happened in countries such as the United States or Japan, where diets are richer in iodine. Thyroid cancer is rare, with a low background incidence compared to other cancers. So excess thyroid cancers due to iodine-131 can be more readily spotted in cancer registries. And this, in fact, has been the case for Chernobyl. Beginning five years after the accident, an increase in the rate of thyroid cancers started and continued rising over the following decades. Scientists estimate that there will ultimately be about 16,000 excess thyroid cancers produced as a result of iodine-131 exposure from Chernobyl. At Fukushima, in contrast, there was much less iodine-131 exposure. The affected population was smaller, local people were advised to avoid local dairy products due to possible contamination and they did not have iodine-deficient diets. Consequently, typical radiation doses to the thyroid were low.

Iodine-131 uptake into the thyroids of exposed people was measured and the doses were estimated to average just 4.2 mSv for children and 3.5 mSv for adults – levels comparable to annual background radiation doses of approximately 3.0 mSv per year. Contrast this to Chernobyl, where a significant proportion of the local population received thyroid doses in excess of 200 mSv – 50 times more – well high enough to see appreciable amounts of excess thyroid cancer. So at Fukushima, where iodine-131 doses approached background levels, we wouldn’t expect thyroid cancer to present the problem that it did at Chernobyl. Nevertheless, there has already been one report that claims there is an increase in thyroid cancer among Fukushima residents at just four years post-accident. That’s earlier than would be expected based on the Chernobyl experience. And the study’s design has been criticized as flawed for a number of scientific reasons, including the comparison methods used. Thus, this report of excess thyroid cancers must be considered suspect until better data arrive.

Chernobyl has no comparison In short, Chernobyl is by far the worst nuclear power plant accident of all time. It was a totally human-made event – a “safety” test gone terribly awry – made worse by incompetent workers who did all the wrong things when attempting to avert a meltdown. Fukushima in contrast, was an unfortunate natural disaster – caused by a tsunami that flooded reactor basements – and the workers acted responsibly to mitigate the damage despite loss of electrical power. April 26, 1986 was the darkest day in the history of nuclear power. Thirty years later, there is no rival that comes even close to Chernobyl in terms of public health consequences; certainly not Fukushima. We must be vigilant to ensure nothing like Chernobyl ever happens again. We don’t want to be “celebrating” any more anniversaries like this one. Author Timothy J. Jorgensen , Director of the Health Physics and Radiation Protection Graduate Program and Associate Professor of Radiation Medicine, Georgetown University This article was originally published on The Conversation . Read the original article .

Share With Others Chernobyl remains the worst nuclear accident of all time - Times of India Times of India 'Fire' volcano erupts in Mexico Chernobyl remains the worst nuclear accident of all time In 1986 Chernobyl nuclear plant in Ukraine witnessed the worst nuclear accident in history. It is the only incident which is marked level 7 in the INES (International Nuclear and Radiological Event Scale- the scale for measuring severity of a nuclear disaster). TNN | Mar 13, 2011, 02.49 AM IST In 1986 Chernobyl nuclear plant in Ukraine witnessed the worst nuclear accident in history. It is the only incident which is marked level 7 in the INES (International Nuclear and Radiological Event Scale- the scale for measuring severity of a nuclear disaster). The accident happened during a routine test when the reactor witnessed an unexpected surge in power, while the safety systems were turned off. It caused a full blown meltdown. The USSR tried to downplay the incident and there is no exact estimate of the casualties. It is however believed that the accident caused more than 50 deaths while the release of radioactive substances lead to the death of another 4,000 people.

The government had to relocate about 200,000 people. The second worst nuclear plant disaster which is marked level 6 by INES also took place in USSR. The accident took place in 1957 in a military nuclear plant near Kyshtym, in Russia. Although there was no immediate causality, the explosion in the plant's waste tank resulted in the release of several tons of nuclear waste into the environment. A week after the incident the government started relocating people when mysterious skin diseases were reported by some inhabitants of the locality. The environmental impact and the exact number of victims are not known. Two other significant nuclear plant accidents took place in UK and the United States, both level 5. In the UK incident, in 1957 a nuclear reactor in Windscale caught fire and released radioactive substances into the environment. Britain's worst nuclear accident is linked to about 200 cancer deaths. America's major nuclear disaster took place in the Three Mile Island nuclear plant when a plumbing failure resulted in draining of the cooling water. This resulted in the reactor core overheating which led to the release of radioactive gases. The situation was brought under control and so far no death is directly linked to the accident.

RELATED Rating Nuclear Accidents and Incidents: Which Were the Worst? | PBS NewsHour Rating Nuclear Accidents and Incidents: Which Were the Worst? EMAIL BY Talea Miller March 18, 2011 at 11:40 AM EST With three reactors having at least partial meltdowns at the Fukushima Daiichi power plant in Japan, the country raised the alert level from four to five on a seven-point international scale for atomic incidents Friday. The International Atomic Energy Agency uses the International Nuclear and Radiological Event Scale to assess the damage done by nuclear accidents. Learn more about the event scale below, and read about some of the worst nuclear disasters in history: The INES scale, image by the International Atomic Energy Agency Level 7 Major Accident: A major release of radioactive material with widespread health and environmental effects requiring implementation of planned and extended countermeasures. Incidents: 1986 — Chernobyl, Ukraine A nuclear reactor located at a power plant in Chernobyl experienced a steam explosion and fire that caused a meltdown, releasing massive quantities of radioactive material. A significant fraction of the reactor core inventory was released, and contaminated areas of Belarus, Ukraine and the Russian Federation. There were widespread health and environmental effects.

Nuclear Energy Agency reports there were 31 fatalities immediately following the incident , with latent deaths estimated at between 9,000 and 33,000 over the 70 years after, based on current radiation dose risks. More than five million people received low whole-body doses of radiation, about 1,000 emergency workers received the highest doses of radiation, some of them fatal. By 2002, more than 4,000 thyroid cancer cases were diagnosed among people who were children at the time and ingested radioactive iodine, often through contaminated milk. Level 6 Serious Accident: A significant release of radioactive material likely to require implementation of planned countermeasures. Incidents: 1957 — Kyshtym, Soviet Union An explosion at a Soviet nuclear weapons plant in Kyshtym resulted in the release of “significant” radioactive material to the environment. The incident forced the evacuation of over 10,000 people from the area contaminated by the blast. Level 5 Accident with Wider Consequences: A limited release of radioactive material likely to require implementation of some planned countermeasures and several deaths from radiation.

Incidents: 1987–Goiânia, Brazil Four people died and six received some doses of radiation from an abandoned highly radioactive medical teletherapy source that ruptured. 1979–Three Mile Island, Pennsylvania A cooling malfunction caused part of the core to melt in a reactor, resulting in a limited off-site release of radioactivity over a multi-state area. Doses off-site were less than normal background radiation. The Nuclear Regulatory Commission determined the accident “led to no deaths or injuries to plant workers or members of the nearby community.” 1957–Windscale Pile, Great Britain A fire in a reactor core resulted in a limited off-site release of radioactivity. Radioactive dust was detected in Belgium, Germany and Norway. It caused an estimated 200 cases of cancer in Britain. 1952– Chalk River, Canada The first-ever accident at a nuclear reactor. A reactor shutoff rod failure, combined with several worker errors, led to a major power excursion of more than double the reactor’s rated output. Former President Jimmy Carter , then a U.S. Navy officer based in Schenectady, New York, was among those dispatched by the U.S.

to help in the emergency response. Level 4 Accident with Local Consequences: A minor release of radioactive material unlikely to result in implementation of planned countermeasures other than local food controls. Incidents: 2006 — Fleurus, Belgium Severe health effects for a worker at a commercial irradiation facility as a result of high doses of radiation. 1999 — Tokaimura, Japan An accident at a uranium processing plant in Tokaimura exposed 55 workers to radiation; one died. 1993 –Tomsk, Russia Pressure buildup led to an explosive mechanical failure. No deaths were reported after the explosion, and no one was evacuated from the contaminated region. 1980 — Saint Laurent des Eaux, France A fuel rupture resulted in a minor off-site release of radioactivity. 1977– JaslovskÃ© Bohunice, Slovak Republic Damaged fuel integrity, extensive corrosion damage of fuel cladding and release of radioactivity.

Information sources include: EPA, IAEA Chernobyl: Facts About the Nuclear Disaster Chernobyl: Facts About the Nuclear Disaster By Marc Lallanilla, Live Science Contributor | September 25, 2013 07:09pm ET MORE The expolsion at the Chernobyl Nuclear Power Plant is among the worst nuclear accidents the world has ever witnessed. Credit: USSR In the early morning hours of April 26, 1986, the Chernobyl nuclear power plant in Ukraine (formerly part of the Soviet Union) exploded, creating what has been described as the worst nuclear disaster the world has ever seen. Even after many years of scientific research and government investigation, there are still many unanswered questions about the Chernobyl accident — especially regarding the long-term health impacts that the massive radiation leak will have on those who were exposed. Where is Chernobyl? Located about 81 miles (130 km) north of the city of Kiev, Ukraine, and about 12 miles (20 km) south of the border with Belarus, the four reactors at the Chernobyl Nuclear Power Plant were designed and built during the 1970s and 1980s.

A manmade reservoir, roughly 8.5 square miles (22 sq. km) in size and fed by the Pripyat River, was created to provide cooling water for the reactor. The nearest town to the power plant was the newly built city of Pripyat, which housed almost 50,000 people in 1986, according to the World Nuclear Association . A smaller town, Chornobyl, was home to about 12,000 residents. The remainder of the region was primarily farms and woodland. The Chernobyl plant used four Soviet-designed RBMK-1000 nuclear reactors — a design that's now universally recognized as inherently flawed. RBMK reactors use enriched U-235 uranium fuel to heat water, creating steam that drives the reactors' turbines and generates electricity. In most nuclear reactors, where water is used as a coolant and to moderate the reactivity of the nuclear core, as the core heats up and produces more steam, the increase in steam bubbles or "voids" in the water reduces the reactivity in the nuclear core. This is an important safety feature found in most reactors built in the United States and other Western nations.

But not in the RBMK-1000, which used graphite to moderate the core's reactivity and to keep a continuous nuclear reaction occurring in the core. As the nuclear core heated and produced more steam bubbles, the core became more reactive, not less, creating a positive-feedback loop that engineers refer to as a "positive-void coefficient." What happened? The day before the Chernobyl nuclear disaster , plant operators were preparing for a one-time shutdown to perform routine maintenance on reactor number 4. In violation of safety regulations, operators disabled plant equipment including the automatic shutdown mechanisms, according to the U.N. Scientific Committee on the Effects of Atomic Radiation (UNSCEAR). At 1:23 a.m. on April 26, when extremely hot nuclear fuel rods were lowered into cooling water, an immense amount of steam was created, which — because of the RBMK reactors' design flaws — created more reactivity in the nuclear core of reactor number 4. The resultant power surge caused an immense explosion that detached the 1,000-ton plate covering the reactor core, releasing radiation into the atmosphere and cutting off the flow of coolant into the reactor.

A few seconds later, a second explosion of even greater power than the first blew the reactor building apart and spewed burning graphite and other parts of the reactor core around the plant, starting a number of intense fires around the damaged reactor and reactor number 3, which was still operating at the time of the explosions. Radioactive fallout The explosions killed two plant workers, who were the first of several workers to die within hours of the accident. For the next several days, as emergency crews tried desperately to contain the fires and radiation leaks, the death toll climbed as plant workers succumbed to acute radiation sickness. Most of the radiation released from the failed nuclear reactor was from iodine-131, cesium-134 and cesium-137. Iodine-131 has a relatively short half-life of eight days, according to UNSCEAR, but is rapidly ingested through the air and tends to localize in the thyroid gland. Cesium isotopes have longer half-lives (cesium-137 has a half-life of 30 years) and are a concern for years after their release into the environment.

On April 27, the residents of Pripyat were evacuated — about 36 hours after the accident had occurred. By that time, many were already complaining about vomiting, headaches and other signs of radiation sickness. Officials eventually closed off an 18-mile (30 km) area around the plant; residents were told they would be able to return after a few days, so many left their personal belongings and valuables behind. Health effects Twenty-eight of the workers at Chernobyl died in the four months following the accident, according to the U.S. Nuclear Regulatory Commission (NRC), including some heroic workers who knew they were exposing themselves to deadly levels of radiation in order to secure the facility from further radiation leaks. The prevailing winds at the time of the accident were from the south and east, so much of the radiation plume traveled northwest toward Belarus. Nonetheless, Soviet authorities were slow to release information about the severity of the disaster to the outside world. But when radiation alarms began to go off at a nuclear plant in Sweden, authorities were forced to reveal the full extent of the crisis.

Within three months of the Chernobyl accident, a total of 31 people died from radiation exposure or other direct effects of the disaster, according to the NRC, UNSCEAR and other sources. More than 6,000 cases of thyroid cancer may eventually be linked to radiation exposure in Ukraine, Belarus and Russia, though the precise number of cases that are directly caused by the Chernobyl accident is difficult (if not impossible) to ascertain. Surprisingly, the overall rate of cancer deaths and other health effects related to Chernobyl's radiation leak is lower than was initially feared. "The majority of the five million residents living in contaminated areas … received very small radiation doses comparable to natural background levels (0.1 rem per year)," according to an NRC report. "Today the available evidence does not strongly connect the accident to radiation-induced increases of leukemia or solid cancer, other than thyroid cancer." Some experts have claimed that unsubstantiated fear of radiation poisoning led to greater suffering than the actual disaster. For example, many doctors throughout Eastern Europe and the Soviet Union advised pregnant women to undergo abortions to avoid bearing children with birth defects or other disorders, though the actual level of radiation exposure these women experienced were too low to cause any problems.

Even the United Nations published a report on the effects of the Chernobyl accident that was so "full of unsubstantiated statements that have no support in scientific assessments," according to the chairman of UNSCEAR, that it was eventually dismissed by most authorities. Dead forest at the Chernobyl site. Credit: dreamstime Environmental impacts Shortly after the radiation leaks from Chernobyl occurred, the trees in the woodlands surrounding the plant were killed by high levels of radiation. This region came to be known as the "Red Forest" because the dead trees turned a bright ginger color. The trees were eventually bulldozed and buried in trenches. The damaged reactor was hastily sealed in a concrete sarcophagus intended to contain the remaining radiation: How effective this sarcophagus has been — and will continue to be into the future — is a subject of intense scientific debate. Plans to construct a safer and more permanent containment structure around the reactor have yet to be implemented. Despite the contamination of the site — and the inherent risks in operating a reactor with serious design flaws — the Chernobyl nuclear plant continued operation for many years, until its last reactor was shut down in December of 2000.

The plant, the ghost towns of Pripyat and Chernobyl, and a large area surrounding the plant known as the "zone of alienation" are largely off-limits to humans. There are, however, exceptions: A few hundred former residents of the area have returned to their former homes, despite the risks of radiation exposure. Scientists, government officials and other personnel are allowed on the site for inspections and other purposes. And in 2011, Ukraine opened up the area to tourists who want to see firsthand the after-effects of the disaster. Chernobyl today The region today is widely known as one of the world's most unique wildlife sanctuaries. Thriving populations of wolves, deer, lynx, beaver, eagles, boar, elk, bears and other animals have been documented in the dense woodlands that now surround the silent plant. Only a handful of radiation effects, such as stunted trees growing in the zone of highest radiation and animals with high levels of cesium-137 in their bodies, are known to occur.

[ Infographic: Chernobyl Nuclear Disaster 25 Years Later ] But that's not to suggest that the area has returned to normal, or will at any point in the near future. Because of the long-lived radiation in the region surrounding the former Chernobyl Nuclear Power Plant, the area won't be safe for human habitation for at least 20,000 years. History’s Worst Nuclear Disasters - History in the Headlines History’s Worst Nuclear Disasters March 18, 2011 By Jennie Cohen Three Mile Island History’s Worst Nuclear Disasters Author History’s Worst Nuclear Disasters URL Google The earthquake that shook Japan on March 11, 2011, stirred up a devastating tsunami that blasted coastal cities with walls of water, shifted the Earth’s axis and has been blamed for thousands of deaths. It also triggered what many are calling the worst disaster of its kind since the incident at Chernobyl, a virtual byword for the risks that come with harnessing nuclear energy. As experts scramble to stem the mounting crisis in Japan, we take a look at four of the most devastating nuclear accidents to date.

Chernobyl (April 26, 1986) Built in the late 1970s about 65 miles north of Kiev in the Ukraine, the Chernobyl plant was one of the largest and oldest nuclear power plants in the world. The explosion and subsequent meltdown that occurred there in April 1986 would claim thousands of lives, cause countless birth defects and unleash a thyroid cancer epidemic on the region. However, it would take years for the full story behind the catastrophe to emerge. A bungled experiment at one of the facility’s four reactors created a sudden power surge, which in turn led to a series of blasts that blew the 1,000-ton steel top off of the reactor. A lethal cloud of radioactive material gathered over the nearby town of Pripyat—which was not evacuated until 36 hours after the explosion—before wafting over large parts of Europe. Soviet officials tried to keep the disaster under wraps, but on April 28 Swedish radiation monitoring stations located more than 800 miles from Chernobyl reported radiation levels 40 percent higher than normal.

In the opening days of the crisis, 32 people died at Chernobyl and dozens more suffered radiation burns. The radiation that escaped into the atmosphere–equivalent to several times that produced by the atomic bombs dropped on Hiroshima and Nagasaki–contaminated millions of acres of forest and farmland. The full human toll from the calamity is still being tallied, but experts believe that thousands of people died and as many as 70,000 suffered severe poisoning. In addition, a large area of land may not be livable for as much as 150 years, including the 18-mile radius around Chernobyl–home to some 150,000 people who had to be permanently relocated. In 2000, the last working reactors at Chernobyl were shut down and the plant was officially closed. Kyshtym (September 29, 1957) In the years following World War II, the Soviet Union constructed dozens of covert facilities—many of them hastily and shoddily built—in an effort to strengthen their nuclear arsenal.

One of these, the Mayak nuclear fuel processing plant in the Russian town of Ozyorsk, became the site of a major disaster when the cooling system in a waste storage tank failed, causing the dried radioactive material it contained to overheat and explode. A plume of deadly particles swelled above Ozyorsk and the surrounding region, eventually spanning some 300 square miles. A full week passed before the affected zone’s 10,000 residents were evacuated; because the plant was shrouded in secrecy, they received no explanation for their abrupt and permanent resettlement. By that time, reports had surfaced of mysterious ailments, including people’s skin sloughing off from exposed body parts. Instead of acknowledging what had happened in the disaster’s aftermath, the Soviet government created the East-Ural Nature Reserve in the contaminated area and prohibited unauthorized access to it. In 1979, the Russian biologist and dissident Zhores Medvedev made waves by exposing the accident’s lasting effects, but it was not until 1990 that reports documenting the event were declassified. According to estimates, 200 people died of cancer because of exposure to radiation, and thousands more may have suffered from related illnesses.

The Mayak incident has come to be associated with the nearby town of Kyshtym because Ozyorsk did not appear on any official maps at the time. Three Mile Island (March 28, 1979) The most serious nuclear accident in U.S. history took place at the Three Mile Island plant near Harrisburg, Pennsylvania, a brand-new facility lauded for its state-of-the-art design, efficiency and affordability during an era of energy crises. It began when a pressure valve in one of the reactors failed to close, allowing cooling water–contaminated with radiation–to drain into adjoining buildings. Control room operators made critical errors as they struggled to contain the crisis, and by early morning the core had heated to over 4,000 degrees–just 1,000 degrees short of meltdown. As radioactive steam began pouring out of the plant, word of the incident leaked to the outside world. The plant’s parent company downplayed the event, claiming that no radiation had been detected off plant grounds, but within days radiation levels were elevated over a four-county zone. Pennsylvania Governor Richard Thornburgh ordered the evacuation of pregnant women and small children from the area.

On March 31, plant workers were able to address the problems and ended the threat of a meltdown. Although no deaths or injuries were reported, there has been an ongoing controversy over whether the radiation released at Three Mile Island led to increased cancer and infant mortality rates in the region. The incident also eroded the American public’s faith in nuclear power, inspiring many demonstrations, and increased awareness of the need for emergency preparedness at the state and local levels. Windscale (October 10, 1957) Designed to produce plutonium and other materials for the country’s burgeoning nuclear weapons program, Britain’s first nuclear reactor, known as Windscale, was built in northwest England in the late 1940s. On October 10, 1957, workers conducting standard maintenance at the massive facility noticed rising temperatures. Upon further inspection, they discovered that the reactor’s uranium-filled graphite core had caught fire. Worse, it had likely been ablaze for two days, releasing dangerous contaminants into the atmosphere. With the reactor on the verge of collapse, plant operators risked their lives to fight the flames with cooling fans, carbon dioxide and water.

The fire finally died out on October 12, but by that time a radioactive cloud was already spreading across the United Kingdom and Europe. While no evacuations occurred, officials prohibited the sale of milk from the affected area for roughly a month. Scientists estimate that, over the long term, radioactive fallout from the Windscale fire may have caused some 240 cases of cancer. An inquiry that began within days of the accident concluded that the blaze had been both avoidable and mishandled. The complete report was suppressed for several decades, however, in part because it may have compromised Britain’s efforts to cooperate with the United States on nuclear weapons development. Tags

Question: What was the worst nuclear accident of all time?
Answer: Chernobyl