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By: History.com Editors

Updated: April 23, 2021 | Original: April 24, 2018

Chernobyl is a nuclear power plant in Ukraine that was the site of a disastrous nuclear accident on April 26, 1986. A routine test at the power plant went horribly wrong, and two massive explosions blew the 1,000-ton roof off one of the plant’s reactors, releasing 400 times more radiation than the atomic bomb dropped on Hiroshima. The worst nuclear disaster in history killed two workers in the explosions and, within months, at least 28 more would be dead by acute radiation exposure. Eventually, thousands of people would show signs of health effects—including cancer—from the fallout.

The Chernobyl disaster not only stoked fears over the dangers of nuclear power, it also exposed the Soviet government’s lack of openness to the Soviet people and the international community. The meltdown and its aftermath drained the Soviet Union of billions in clean-up costs, led to the loss of a primary energy source and dealt a serious blow to national pride.

Then-Soviet leader Mikhail Gorbachev would later say that he thought the Chernobyl meltdown, “even more than my launch of perestroika , was perhaps the real cause of the collapse of the Soviet Union five years later.”

Where Is Chernobyl?

Chernobyl is located in northern Ukraine, about 80 miles north of Kiev. A small town, Pripyat, was constructed a few miles from the site of the nuclear plant to accommodate workers and their families.

Construction of the Chernobyl power plant began in 1977, when the country was still part of the Soviet Union. By 1983, four reactors had been completed, and the addition of two more reactors was planned in subsequent years.

What Happened at Chernobyl?

A routine exercise to test whether an emergency water cooling system would work during a power loss started at 1:23 a.m. on April 26.

Within seconds, an uncontrolled reaction caused pressure to build up in Reactor No. 4 in the form of steam. The steam blasted the roof off the reactor, releasing plumes of radiation and chunks of burning, radioactive debris.

About two to three seconds later, a second explosion hurled out additional fuel. A fire started at the roof of Reactor No. 3, risking a breach at that facility. Automatic safety systems that would normally have kicked into action did not because they had been shut down prior to the test.

READ MORE: Chernobyl Disaster: The Meltdown by the Minute

Firefighters arrived at the scene within minutes and began to fight the blaze without gear to protect them from radiation. Many of them would soon number among the 28 killed by acute radiation exposure.

Eyewitness accounts of the firefighters who had helped battle the fires described the radiation as “tasting like metal,” and feeling pain like pins and needles on their faces, according to the CBC documentary series, Witness . Days later, many of those firefighters would be dead.

It wasn’t until 5 a.m. the following day that Reactor No. 3 was shut down. Some 24 hours later, Reactors No. 1 and 2 were also shut down.

By the afternoon of April 26, the Soviet government had mobilized troops to help fight the blaze. Some were dropped at the rooftop of the reactor to furiously shovel debris off the facility and spray water on the exposed reactor to keep it cool.

The workers were picked up within seconds to minimize their radiation exposure. It would take nearly two weeks to extinguish all the fires using sand, lead and nitrogen.

Pripyat Evacuated

Meanwhile, life went on as usual for almost a day in the neighboring town of Pripyat. Aside from the sight of trucks cleaning the streets with foam, there were initially few signs of the disaster unfolding just miles away.

It wasn’t until the next day, April 27, when the government began evacuations of Pripyat’s 50,000 residents. Residents were told they would be away for just a few days, so they took very little with them. Most would never return to their homes.

Soviet Secrecy

It took days for Soviet leadership to inform the international community that the disaster had occurred. The Soviet government made no official statement about the global-scale accident until Swedish leaders demanded an explanation when operators of a nuclear power plant in Stockholm registered unusually high radiation levels near their plant.

Finally, on April 28, the Kremlin reported that there had been an accident at Chernobyl and that authorities were handling it. The statement was followed by a state broadcast detailing the U.S. nuclear accident at Three Mile Island and other nuclear incidents in western countries.

Three days later, Soviet May Day parades to celebrate workers went ahead as usual in Moscow, Kiev and Belarus’ capital Minsk—even as hazardous amounts of radiation were still streaming from the wrecked power plant.

Most people, even within the Ukraine, were still unaware of the accident, the deaths, and the hasty evacuations of Pripyat.

READ MORE: The Chernobyl Cover-Up: How Officials Botched Evacuating an Irradiated City

Chernobyl Disaster Spewed Radiation

The damaged plant released a large quantity of radioactive substances, including iodine-131, cesium-137, plutonium and strontium-90, into the air for over a period of 10 days.

The radioactive cloud was deposited nearby as dust and debris, but was also carried by wind over the Ukraine, Belarus, Russia, Scandinavia and other parts of Europe.

In an attempt to contain the fallout, on May 14, Soviet leader Mikhail Gorbachev ordered the dispatch of hundreds of thousands of people, including firefighters, military reservists and miners, to the site to aid in clean-up. The corps worked steadily, often with inadequate protective gear, through 1989 to clear debris and contain the disaster.

Chernobyl Sarcophagus

Over a hurried construction period of 206 days, crews erected a steel and cement sarcophagus to entomb the damaged reactor and contain any further release of radiation.

As former liquidator, Yaroslav Melnik, told the BBC in January 2017, “We worked in three shifts, but only for five to seven minutes at a time because of the danger. After finishing, we’d throw our clothes in the garbage.”

Starting in 2010, an international consortium organized the building of a bigger, more secure sarcophagus for the site. The 35,000-ton New Safe Confinement was built on tracks and then slid over the damaged reactor and existing sarcophagus in November 2016.

After the installation of the new structure, radiation near the plant dropped to just one-tenth of previous levels, according to official figures. The structure was designed to contain the radioactive debris for 100 years.

Chernobyl Elephant’s Foot

Deep within the basement of Reactor 4 lies the Chernobyl Elephant’s Foot, a huge mass of melted concrete, sand and highly radioactive nuclear fuel.

The mass was named for its wrinkled appearance, which reminded some observers of the wrinkled skin of an elephant’s leg and foot.

In the 1980s, the Elephant’s Foot gave off an estimated 10,000 roentgens of radiation each hour, enough to kill a person three feet away in less than two minutes. By 2001, that rate had dropped to roughly 800 roentgens per hour.

How Many People Died in Chernobyl?

Ukraine’s government declared in 1995 that 125,000 people had died from the effects of Chernobyl radiation. A 2005 report from the United Nations Chernobyl Forum estimated that while fewer than 50 people were killed in the months following the accident, up to 9,000 people could eventually die from excess cancer deaths linked to radiation exposure from Chernobyl.

As of 2005, according to the Union of Concerned Scientists , some 6,000 thyroid cancers and 15 thyroid cancer deaths had been attributed to Chernobyl.

Health effects from the Chernobyl disaster remain unclear, apart from the initial 30 people the Soviet government confirmed killed from the explosions and acute radiation exposure. No official government studies were conducted following the explosion to assess its effects on workers, the liquidators and nearby populations.

A 2011 study by the U.S. National Institutes of Health concluded that exposure to radioactive iodine-131 from Chernobyl fallout was likely responsible for thyroid cancers that were still being reported among people who were children or adolescents at the time of the accident.

Chernobyl Exclusion Zone

Apart from the ever-unfolding human toll from the disaster, the Chernobyl accident also left behind a huge area of radiation-tainted land.

A 770-mile-wide Chernobyl Exclusion Zone around the site isn’t considered safe for human habitation and can’t be used for logging or agriculture due to contaminated plants and soil. By 2017, however, entrepreneurs found a new use for the territory.

In December 2017, a Ukrainian-German company, Solar Chernobyl, announced construction of a massive solar power plant in the abandoned territory. The one-megawatt power plant, built just a few hundred feet from the damaged Reactor 4, was fitted with 3,800 photovoltaic panels. The Ukrainian government said that a collection of companies planned to eventually develop up to 99 more megawatts of solar power at the site.

That’s a lot of power, but still not close to the former output of the ruined nuclear power plant. At the time of the accident Chernobyl’s four reactors could generate 1,000 megawatts each .

Chernobyl Animals Thrive

Meanwhile, wildlife, including boars, wolves, beavers and bison, showed signs of flourishing at the Chernobyl site, according to an April 2016 study .

The researchers pointed out that while radiation exposure couldn’t be good for the animals, the benefits of the absence of humans outweighed radiation risk.

Chernobyl Today

Humans, on the other hand, aren’t expected to repopulate the area any time soon. Ukrainian authorities have said it will not be safe for people to live in the Chernobyl Exclusion Zone for more than 24,000 years.

Today tourists can visit the site, which appears frozen in time, apart from signs of looting, natural weathering and the encroachment of nature.

“Chernobyl: The True Scale of the Accident,” September 5, 2005, World Health Organization . Chernobyl Accident 1986, updated November 2016, World Nuclear Association “Health Effects of the Chernobyl Accident: An Overview,” April 2006, World Health Organization . “Chernobyl’s Legacy 30 Years On,” by Tom Burridge, April 26, 2016, BBC News “Higher Cancer Risk Continues After Chernobyl,” March 17, 2011, National Institutes of Health . “How Many Cancer Deaths Did Chernobyl Really Cause?” by Lisbeth Gronlund, Union of Concerned Scientists . “Animals Rule Chernobyl Three Decades After Nuclear Disaster,” by John Wendle, April 18, 2016, National Geographic . “A Nuclear Disaster That Brought Down an Empire,” April 26, 2016, The Economist . “World’s Largest Moveable Steel Structure Shelters Sarcophagus at Chernobyl,” April 27, 2017, PhysOrg/Pacific Northwest National Laboratory . “Pictures: ‘Liquidators’ Endured Chernobyl 25 Years Ago,” by Marianne Lavelle, April 27, 2011, National Geographic . “Chernobyl: Timeline of a Nuclear Nightmare,” by Kim Hjelmgaard, USA Today . “A Vast New Tomb for the Most Dangerous Disaster Site in the World,” by Christian Borys, January 3, 2017, BBC Future Now . “The Lessons of Chernobyl May Be Different Than We Thought,” by Ryan Faith, April 26, 2016, Vice News . “25 Years After Chernobyl, We Don’t Know How Many Died,” by Roger Highfield, April 21, 2011, New Scientist . “Chernobyl’s Transformation Into a Massive Solar Plant Is Almost Complete,” by David Nield, January 13, 2018, Science Alert . “The Famous Photo of Chernobyl’s Most Dangerous Radioactive Material Was a Selfie.” January 24, 2016, Atlas Obscura .

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people in protective clothing using devices to measure for radiation

The cleanup of the area surrounding the Chernobyl nuclear disaster is expected to continue for decades, while parts may remain uninhabitable for thousands of years.

The Chernobyl disaster: What happened, and the long-term impacts

The accident at a nuclear power plant in Ukraine shocked the world, permanently altered a region, and leaves many questions unanswered.

On April 25 and 26, 1986, the worst nuclear accident in history unfolded in what is now northern Ukraine as a reactor at a nuclear power plant exploded and burned. Shrouded in secrecy, the incident was a watershed moment in both the Cold War and the history of nuclear power . More than 30 years on, scientists estimate the zone around the former plant will not be habitable for up to 20,000 years .

The disaster took place near the city of Chernobyl in the former USSR, which invested heavily in nuclear power after World War II. Starting in 1977, Soviet scientists installed four RBMK nuclear reactors at the power plant, which is located just south of what is now Ukraine’s border with Belarus.

A few months after reactor 4 of the Chernobyl nuclear power plant went up in toxic flames in 1986, it was encased in a concrete and steel "sarcophagus" to contain the radioactive material inside. That aging structure, seen here, was covered with a larger, newer containment housing in 2016.

On April 25, 1986, routine maintenance was scheduled at V.I. Lenin Nuclear Power Station’s fourth reactor, and workers planned to use the downtime to test whether the reactor could still be cooled if the plant lost power. During the test, however, workers violated safety protocols and power surged inside the plant. Despite attempts to shut down the reactor entirely, another power surge caused a chain reaction of explosions inside. Finally, the nuclear core itself was exposed, spewing radioactive material into the atmosphere.

Firefighters attempted to put out a series of blazes at the plant, and eventually helicopters dumped sand and other materials in an attempt to squelch the fires and contain the contamination. Despite the death of two people in the explosions, the hospitalization of workers and firefighters, and the danger from fallout and fire, no one in the surrounding areas—including the nearby city of Pripyat , which was built in the 1970s to house workers at the plant—was evacuated until about 36 hours after the disaster began.

Publicizing a nuclear accident was considered a significant political risk, but by then it was too late: The meltdown had already spread radiation as far as Sweden, where officials at another nuclear plant began to ask about what was happening in the USSR. After first denying any accident, the Soviets finally made a brief announcement on April 28.

A child who was only one-year old at the time of the Chernobyl disaster undergoes an ultrasound test to see if there are any long-term effects of possible radiation exposure.

Historic disaster

Soon, the world realized that it was witnessing a historic event. Up to 30 percent of Chernobyl’s 190 metric tons of uranium was now in the atmosphere, and the Soviet Union eventually evacuated 335,000 people, establishing a 19-mile-wide “exclusion zone” around the reactor.

At least 28 people initially died as a result of the accident, while more than 100 were injured. The United Nations Scientific Committee on the Effects of Atomic Radiation has reported that more than 6,000 children and adolescents developed thyroid cancer after being exposed to radiation from the incident, although some experts have challenged that claim .

International researchers have predicted that ultimately, around 4,000 people exposed to high levels of radiation could succumb to radiation-related cancer, while about 5,000 people exposed to lower levels of radiation may suffer the same fate. Yet the full consequences of the accident, including impacts on mental health and even subsequent generations, remain highly debated and under study.

What remains of the reactor is now inside a massive steel containment structure deployed in late 2016. Containment efforts and monitoring continue and cleanup is expected to last until at least 2065.

The city of Pripyat was built to house workers of the nuclear power plant in the 1970s. It has been an abandoned ghost town since the accident, and is now used as a laboratory to study fallout patterns.

Long-term impacts

The impact of the disaster on the surrounding forest and wildlife also remains an area of active research. In the immediate aftermath of the accident, an area of about four square miles became known as the “Red Forest” because so many trees turned reddish-brown and died after absorbing high levels of radiation.

Today, the exclusion zone is eerily quiet, yet full of life. Though many trees have regrown, scientists have found evidence of elevated levels of cataracts and albinism, and lower rates of beneficial bacteria, among some wildlife species in the area in recent years . Yet, due to the exclusion of human activity around the shuttered power plant, the numbers of some wildlife, from lynxes to elk, have increased . In 2015, scientists estimated there were seven times more wolves in the exclusion zone than in nearby comparable reserves, thanks to humans’ absence.

The Chernobyl disaster had other fallout: The economic and political toll hastened the end of the USSR and fueled a global anti-nuclear movement. The disaster has been estimated to cost some $235 billion in damages . What is now Belarus, which saw 23 percent of its territory contaminated by the accident, lost about a fifth of its agricultural land. At the height of disaster response efforts, in 1991, Belarus spent 22 percent of its total budget dealing with Chernobyl.

Today, Chernobyl beckons to tourists who are intrigued by its history and its danger. But though Chernobyl symbolizes the potential devastation of nuclear power, Russia never quite moved beyond its legacy—or its technology. As of 2019, there are still 11 operational RBMK reactors in Russia.

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Chernobyl accident summary

Chernobyl accident , Accident at the Chernobyl (Ukraine) nuclear power station in the Soviet Union, the worst disaster in the history of nuclear power generation. On April 25–26, 1986, technicians attempted a poorly designed experiment, causing the chain reaction in the core to go out of control. The reactor’s lid was blown off, and large amounts of radioactive material were released into the atmosphere. A partial meltdown of the core also occurred. A cover-up was attempted, but, after Swedish monitoring stations reported abnormally high levels of wind-transported radioactivity, the Soviet government admitted the truth. As many as 49 people may have died in the initial explosions. Beyond these immediate deaths, several thousand radiation-induced illnesses and cancer deaths were expected in the long term. The incident set off an international outcry over the dangers posed by radioactive emissions.

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Chernobyl: the true scale of the accident

20 years later a un report provides definitive answers and ways to repair lives.

A total of up to 4000 people could eventually die of radiation exposure from the Chernobyl nuclear power plant (NPP) accident nearly 20 years ago, an international team of more than 100 scientists has concluded.

As of mid-2005, however, fewer than 50 deaths had been directly attributed to radiation from the disaster, almost all being highly exposed rescue workers, many who died within months of the accident but others who died as late as 2004.

The new numbers are presented in a landmark digest report, “Chernobyl’s Legacy: Health, Environmental and Socio-Economic Impacts,” just released by the Chernobyl Forum. The digest, based on a three-volume, 600-page report and incorporating the work of hundreds of scientists, economists and health experts, assesses the 20-year impact of the largest nuclear accident in history. The Forum is made up of 8 UN specialized agencies, including the International Atomic Energy Agency (IAEA), World Health Organization (WHO), United Nations Development Programme (UNDP), Food and Agriculture Organization (FAO), United Nations Environment Programme (UNEP), United Nations Office for the Coordination of Humanitarian Affairs (UN-OCHA), United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR), and the World Bank, as well as the governments of Belarus, the Russian Federation and Ukraine.

“This compilation of the latest research can help to settle the outstanding questions about how much death, disease and economic fallout really resulted from the Chernobyl accident,” explains Dr. Burton Bennett, chairman of the Chernobyl Forum and an authority on radiation effects. “The governments of the three most-affected countries have realized that they need to find a clear way forward, and that progress must be based on a sound consensus about environmental, health and economic consequences and some good advice and support from the international community.”

Bennett continued: “This was a very serious accident with major health consequences, especially for thousands of workers exposed in the early days who received very high radiation doses, and for the thousands more stricken with thyroid cancer. By and large, however, we have not found profound negative health impacts to the rest of the population in surrounding areas, nor have we found widespread contamination that would continue to pose a substantial threat to human health, within a few exceptional, restricted areas.”

The Forum’s report aims to help the affected countries understand the true scale of the accident's consequences and also suggests ways the governments of Belarus, the Russian Federation and Ukraine might address major economic and social problems stemming from the accident. Members of the Forum, including representatives of the three governments, will meet September 6 and 7 in Vienna at an unprecedented gathering of the world’s experts on Chernobyl, radiation effects and protection, to consider these findings and recommendations.

Major study findings

Dozens of important findings are included in the massive report:

Approximately 1000 on-site reactor staff and emergency workers were heavily exposed to high-level radiation on the first day of the accident; among the more than 200 000 emergency and recovery operation workers exposed during the period from 1986-1987, an estimated 2200 radiation-caused deaths can be expected during their lifetime.
An estimated five million people currently live in areas of Belarus, Russia and Ukraine that are contaminated with radionuclides due to the accident; about 100 000 of them live in areas classified in the past by government authorities as areas of “strict control”. The existing “zoning” definitions need to be revisited and relaxed in light of the new findings.
About 4000 cases of thyroid cancer, mainly in children and adolescents at the time of the accident, have resulted from the accident’s contamination and at least nine children died of thyroid cancer; however the survival rate among such cancer victims, judging from experience in Belarus, has been almost 99%.
Most emergency workers and people living in contaminated areas received relatively low whole body radiation doses, comparable to natural background levels. As a consequence, no evidence or likelihood of decreased fertility among the affected population has been found, nor has there been any evidence of increases in congenital malformations that can be attributed to radiation exposure.
Poverty, “lifestyle” diseases now rampant in the former Soviet Union and mental health problems pose a far greater threat to local communities than does radiation exposure.
Relocation proved a “deeply traumatic experience” for some 350,000 people moved out of the affected areas. Although 116 000 were moved from the most heavily impacted area immediately after the accident, later relocations did little to reduce radiation exposure.
Persistent myths and misperceptions about the threat of radiation have resulted in “paralyzing fatalism” among residents of affected areas.
Ambitious rehabilitation and social benefit programs started by the former Soviet Union, and continued by Belarus, Russia and Ukraine, need reformulation due to changes in radiation conditions, poor targeting and funding shortages.
Structural elements of the sarcophagus built to contain the damaged reactor have degraded, posing a risk of collapse and the release of radioactive dust;
A comprehensive plan to dispose of tons of high-level radioactive waste at and around the Chernobyl NPP site, in accordance with current safety standards, has yet to be defined.

Alongside radiation-induced deaths and diseases, the report labels the mental health impact of Chernobyl as “the largest public health problem created by the accident” and partially attributes this damaging psychological impact to a lack of accurate information. These problems manifest as negative self-assessments of health, belief in a shortened life expectancy, lack of initiative, and dependency on assistance from the state.

“Two decades after the Chernobyl accident, residents in the affected areas still lack the information they need to lead the healthy and productive lives that are possible,” explains Louisa Vinton, Chernobyl focal point at the UNDP. “We are advising our partner governments that they must reach people with accurate information, not only about how to live safely in regions of low-level contamination, but also about leading healthy lifestyles and creating new livelihoods.” But, says Dr Michael Repacholi, Manager of WHO's Radiation Program, “the sum total of the Chernobyl Forum is a reassuring message.”

He explains that there have been 4000 cases of thyroid cancer, mainly in children, but that except for nine deaths, all of them have recovered. "Otherwise, the team of international experts found no evidence for any increases in the incidence of leukemia and cancer among affected residents."

The international experts have estimated that radiation could cause up to about 4000 eventual deaths among the higher-exposed Chernobyl populations, i.e., emergency workers from 1986-1987, evacuees and residents of the most contaminated areas. This number contains both the known radiation-induced cancer and leukaemia deaths and a statistical prediction, based on estimates of the radiation doses received by these populations. As about quarter of people die from spontaneous cancer not caused by Chernobyl radiation, the radiation-induced increase of only about 3% will be difficult to observe. However, in the most exposed cohorts of emergency and recovery operation workers some increase of particular cancer forms (e.g., leukemia) in particular time periods has already been observed. The predictions use six decades of scientific experience with the effects of such doses, explained Repacholi.

Repacholi concludes that “the health effects of the accident were potentially horrific, but when you add them up using validated conclusions from good science, the public health effects were not nearly as substantial as had at first been feared.”

The report’s estimate for the eventual number of deaths is far lower than earlier, well-publicized speculations that radiation exposure would claim tens of thousands of lives. But the 4000 figure is not far different from estimates made in 1986 by Soviet scientists, according to Dr Mikhail Balonov, a radiation expert with the International Atomic Energy Agency in Vienna, who was a scientist in the former Soviet Union at the time of the accident.

As for environmental impact, the reports are also reassuring, for the scientific assessments show that, except for the still closed, highly contaminated 30 kilometer area surrounding the reactor, and some closed lakes and restricted forests, radiation levels have mostly returned to acceptable levels. “In most areas the problems are economic and psychological, not health or environmental,” reports Balonov, the scientific secretary of the Chernobyl Forum effort who has been involved with Chernobyl recovery since the disaster occurred.

Recommendations

Recommendations call for focusing assistance efforts on highly contaminated areas and redesigning government programs to help those genuinely in need. Suggested changes would shift programs away from those that foster “dependency” and a “victim” mentality, and replacing them with initiatives that encourage opportunity, support local development, and give people confidence in their futures.

In the health area, the Forum report calls for continued close monitoring of workers who recovered from Acute Radiation Syndrome (ARS) and other highly exposed emergency personnel. The Report also calls for focused screening of children exposed to radioiodine for thyroid cancer and highly exposed clean-up workers for non-thyroid cancers. However, existing screening programs should be evaluated for cost-effectiveness, since the incidence of spontaneous thyroid cancers is increasing significantly as the target population ages. Moreover, high quality cancer registries need continuing government support.

In the environmental realm, the Report calls for long term monitoring of caesium and strontium radionuclides to assess human exposure and food contamination and to analyse the impacts of remedial actions and radiation-reduction countermeasures. Better information needs to be provided to the public about the persistence of radioactive contamination in certain food products and about food preparation methods that reduce radionuclide intake. Restrictions on harvesting of some wild food products are still needed in some areas.

Also in the realm of protecting the environment, the Report calls for an “integrated waste management program for the Shelter, the Chernobyl NPP site and the Exclusion Zone” to ensure application of consistent management and capacity for all types of radioactive waste. Waste storage and disposal must be dealt with in a comprehensive manner across the entire Exclusion Zone, according to the Report.

In areas where human exposure is not high, no remediation needs to be done, points out Balonov. “If we do not expect health or environmental effects, we should not waste resources and effort on low priority, low contamination areas,” he explains. “We need to focus our efforts and resources on real problems.”

One key recommendation addresses the fact that large parts of the population, especially in rural areas, still lack accurate information and emphasizes the need to find better ways both to inform the public and to overcome the lack of credibility that hampered previous efforts. Even though accurate information has been available for years, either it has not reached those who need it or people do not trust and accept the information and do not act upon it, according to the Report.

This recommendation calls for targeting information to specific audiences, including community leaders and health care workers, along with a broader strategy that promotes healthy lifestyles as well as information about how to reduce internal and external radiation exposures and address the main causes of disease and mortality.

In the socioeconomic sphere, the Report recommends a new development approach that helps individuals to “take control of their own lives and communities to take control of their own futures.” The Governments, the Report states, must streamline and refocus Chernobyl programs through more targeted benefits, elimination of unnecessary benefits to people in less contaminated areas, improving primary health care, support for safe food production techniques, and encouragement for investment and private sector development, including small and medium-size enterprises.

Notes Vinton, “The most important need is for accurate information on healthy lifestyles, together with better regulations to promote small, rural businesses. Poverty is the real danger. We need to take steps to empower people.”

Answers to Longstanding Questions

How much radiation were people exposed to as a result of the accident.

With the exception of on-site reactor staff and emergency workers exposed on 26 April, most recovery operation workers and those living in contaminated territories received relatively low whole body radiation doses, comparable to background radiation levels and lower than the average doses received by residents in some parts of the world having high natural background radiation levels.

For the majority of the five million people living in the contaminated areas, exposures are within the recommended dose limit for the general public, though about 100 000 residents still receive more. Remediation of those areas and application of some agricultural countermeasures continues. Further reduction of exposure levels will be slow, but most exposure from the accident has already occurred.

How many people died and how many more are likely to die in the future?

The total number of deaths already attributable to Chernobyl or expected in the future over the lifetime of emergency workers and local residents in the most contaminated areas is estimated to be about 4000. This includes some 50 emergency workers who died of acute radiation syndrome and nine children who died of thyroid cancer, and an estimated total of 3940 deaths from radiation-induced cancer and leukemia among the 200 000 emergency workers from 1986-1987, 116 000 evacuees and 270 000 residents of the most contaminated areas (total about 600 000). These three major cohorts were subjected to higher doses of radiation amongst all the people exposed to Chernobyl radiation.

The estimated 4000 casualties may occur during the lifetime of about 600 000 people under consideration. As about quarter of them will eventually die from spontaneous cancer not caused by Chernobyl radiation, the radiation-induced increase of about 3% will be difficult to observe. However, in the most highly exposed cohorts of emergency and recovery operation workers, some increase in particular cancers (e.g., leukemia) has already been observed.

Confusion about the impact has arisen owing to the fact that thousands of people in the affected areas have died of natural causes. Also, widespread expectations of ill health and a tendency to attribute all health problems to radiation exposure have led local residents to assume that Chernobyl related fatalities were much higher than they actually were.

What diseases have already occurred or might occur in the future?

Residents who ate food contaminated with radioactive iodine in the days immediately after the accident received relatively high doses to the thyroid gland. This was especially true of children who drank milk from cows who had eaten contaminated grass. Since iodine concentrates in the thyroid gland, this was a major cause of the high incidence of thyroid cancer in children.

Several recent studies suggest a slight increase in the incidence of leukemia among emergency workers, but not in children or adult residents of contaminated areas. A slight increase in solid cancers and possibly circulatory system diseases was noted, but needs to be evaluated further because of the possible indirect influence of such factors as smoking, alcohol, stress and unhealthy lifestyle.

Have there been or will there be any inherited or reproductive effects?

Because of the relatively low doses to residents of contaminated territories, no evidence or likelihood of decreased fertility has been seen among males or females. Also, because the doses were so low, there was no evidence of any effect on the number of stillbirths, adverse pregnancy outcomes, delivery complications or overall health of children. A modest but steady increase in reported congenital malformations in both contaminated and uncontaminated areas of Belarus appears related to better reporting, not radiation.

Did the trauma of rapid relocation cause persistent psychological or mental health problems?

Stress symptoms, depression, anxiety and medically unexplained physical symptoms have been reported, including self-perceived poor health. The designation of the affected population as “victims” rather than “survivors” has led them to perceive themselves as helpless, weak and lacking control over their future. This, in turn, has led either to over cautious behavior and exaggerated health concerns, or to reckless conduct, such as consumption of mushrooms, berries and game from areas still designated as highly contaminated, overuse of alcohol and tobacco, and unprotected promiscuous sexual activity.

What was the environmental impact?

Ecosystems affected by Chernobyl have been studied and monitored extensively for the past two decades. Major releases of radionuclides continued for ten days and contaminated more than 200 000 square kilometers of Europe. The extent of deposition varied depending on whether it was raining when contaminated air masses passed.

Most of the strontium and plutonium isotopes were deposited within 100 kilometres of the damaged reactor. Radioactive iodine, of great concern after the accident, has a short half-life, and has now decayed away. Strontium and caesium, with a longer half life of 30 years, persist and will remain a concern for decades to come. Although plutonium isotopes and americium 241 will persist perhaps for thousands of years, their contribution to human exposure is low.

What is the scope of urban contamination?

Open surfaces, such as roads, lawns and roofs, were most heavily contaminated. Residents of Pripyat, the city nearest to Chernobyl, were quickly evacuated, reducing their potential exposure to radioactive materials. Wind, rain and human activity has reduced surface contamination, but led to secondary contamination of sewage and sludge systems. Radiation in air above settled areas returned to background levels, though levels remain higher where soils have remained undisturbed.

How contaminated are agricultural areas?

Weathering, physical decay, migration of radionuclides down the soil and reductions in bioavailability have led to a significant reduction in the transfer of radionuclides to plants and animals. Radioactive iodine, rapidly absorbed from grasses and animal feed into milk, was an early concern and elevated levels were seen in some parts of the former Soviet Union and Southern Europe, but, given the nuclide’s short half life, this concern abated quickly. Currently and for the long term, radiocaesium, present in milk, meat and some plant foods, remains the most significant concern for internal human exposure, but, with the exception of a few areas, concentrations fall within safe levels.

What is the extent of forest contamination?

Following the accident, animals and vegetation in forest and mountain areas had high absorption of radiocaesium, with persistent high levels in mushrooms, berries and game. Because exposure from agricultural products has declined, the relative importance of exposure from forest products has increased and will only decline as radioactive materials migrate downward into the soil and slowly decay. The high transfer of radiocaesium from lichen to reindeer meat to humans was seen in the Artic and sub-Arctic areas, with high contamination of reindeer meat in Finland, Norway, Russia, and Sweden. The concerned governments imposed some restrictions on hunting, including scheduling hunting season when animals have lower meat contamination.

How contaminated are the aquatic systems?

Contamination of surface waters throughout much of Europe declined quickly through dilution, physical decay, and absorption of radionuclides in bed sediments and catchment soils. Because of bioaccumulation in the aquatic food chain, though, elevated concentrations of radiocaesium were found in fish from lakes as far away as Germany and Scandinavia. Comparable levels of radiostrontium, which concentrates in fish bone, not in muscle, were not significant for humans. Levels in fish and waters are currently low, except in areas with “closed” lakes with no outflowing streams. In those lakes, levels of radiocaesium in fish will remain high for decades and, therefore, restrictions on fishing there should be maintained.

What environmental countermeasures and remediation have been taken?

The most effective early agricultural countermeasure was removing contaminated pasture grasses from animal diets and monitoring milk for radiation levels. Treatment of land for fodder crops, clean feeding and use of Cs-binders (that prevented the transfer of radiocaesium from fodder to milk) led to large reductions in contamination and permitted agriculture to continue, though some increase in radionuclide content of plant and animal products has been measured since the mid-1990s when economic problems forced a cutback in treatments. Some agricultural lands in the three countries have been taken out of use until remediation is undertaken.

A number of measures applied to forests in affected countries and in Scandinavia have reduced human exposure, including restrictions on access to forest areas, on harvesting of food products such as game, berries and mushrooms, and on the public collection of firewood, along with changes in hunting to avoid consumption of game meat where seasonal levels of radiocaesium may be high. Low income levels in some areas cause local residents to disregard these rules.

What were radiation-induced effects on plants and animals?

Increased mortality of coniferous plants, soil invertebrates and mammals and reproductive losses in plants and animals were seen in high exposure areas up to a distance of 20-30 kilometers. Outside that zone, no acute radiation-induced effects have been reported. With reductions of exposure levels, biological populations have been recovering, though the genetic effects of radiation were seen in both somatic and germ cells of plants and animals. Prohibiting agricultural and industrial activities in the exclusion zone permitted many plant and animal populations to expand and created, paradoxically, “a unique sanctuary for biodiversity.”

Does dismantlement of the Shelter and management of radioactive waste pose further environmental problems?

The protective shelter was erected quickly, which led to some imperfections in the shelter itself and did not permit gathering complete data on the stability of the damaged unit. Also, some structural parts of the shelter have corroded in the past two decades. The main potential hazard posed by the shelter is the possible collapse of its top structures and the release of radioactive dust.

Strengthening those unstable structures has been performed recently, and construction of a New Safe Confinement covering the existing shelter that should serve for more than 100 years, starts in near future. The new cover will allow dismantlement of the current shelter, removal of the radioactive fuel mass from the damaged unit and, eventually, decommissioning of the damaged reactor.

A comprehensive strategy still has to be developed for dealing with the high level and long-lived radioactive waste from past remediation activities. Much of this waste was placed in temporary storage in trenches and landfills that do not meet current waste safety requirements.

What was the economic cost?

Because of policies in place at the time of the explosion and the inflation and economic disruptions that followed the break-up of the Soviet Union, precise costs have been impossible to calculate. A variety of estimates from the 1990s placed the costs over two decades at hundreds of billions of dollars. These costs included direct damage, expenditures related to recovery and mitigation, resettlement of people, social protection and health care for the affected population, research on environment, health and the production of clean food, radiation monitoring, as well as indirect losses due to removing agricultural lands and forests from use and the closing of agriculture and industrial facilities, and such additional costs as cancellation of the nuclear power program in Belarus and the additional costs of energy from the loss of power from Chernobyl. The costs have created a huge drain on the budgets of the three countries involved.

What were the main consequences for the local economy?

Agriculture was hardest hit, with 784 320 hectares taken from production. Timber production was halted in 694,200 hectares of forest. Remediation made “clean food” production possible in many areas but led to higher costs in the form of fertilizers, additives and special cultivation processes. Even where farming is safe, the stigma associated with Chernobyl caused marketing problems and led to falling revenues, declining production and the closure of some facilities. Combined with disruptions due to the collapse of the Soviet Union, recession, and new market mechanisms, the region’s economy suffered, resulting in lower living standards, unemployment and increased poverty. All agricultural areas, whether affected by radiation or not, proved vulnerable.

Poverty is especially acute in affected areas. Wages for agricultural workers tend to be low and employment outside of agriculture is limited. Many skilled and educated workers, especially younger workers, left the region. Also, the business environment discourages entrepreneurial ventures and private investment is low.

What impact did Chernobyl and the aftermath have on local communities?

More than 350 000 people have been relocated away from the most severely contaminated areas, 116 000 of them immediately after the accident. Even when people were compensated for losses, given free houses and a choice of resettlement location, the experience was traumatic and left many with no employment and a belief that they have no place in society. Surveys show that those who remained or returned to their homes coped better with the aftermath than those who were resettled. Tensions between new and old residents of resettlement villages also contributed to the ostracism felt by the newcomers. The demographic structure of the affected areas became skewed since many skilled, educated and entrepreneurial workers, often younger, left the areas leaving behind an older population with few of the skills needed for economic recovery.

The older population has meant that deaths exceed births, which reinforces the perception that these areas are dangerous places to live. Even when pay is high, schools, hospitals and other essential public services are short of qualified specialists.

What has been the impact on individuals?

According to the Forum’s report on health, “the mental health impact of Chernobyl is the largest public health problem unleashed by the accident to date.” People in the affected areas report negative assessments of their health and well-being, coupled with an exaggerated sense of the danger to their health from radiation exposure and a belief in a shorter life expectancy. Anxiety over the health effects of radiation shows no signs of diminishing and may even be spreading. Life expectancy has been declining across the former Soviet Union, due to cardiovascular disease, injuries and poisoning, and not radiation-related illness.

How have governments responded?

The resettlement and rehabilitation programs launched in Soviet conditions proved unsustainable after 1991 and funding for projects declined, leaving many projects unfinished and abandoned and many of the promised benefits under funded. Also, benefits were offered to broad categories of “Chernobyl victims” that expanded to seven million now receiving or eligible for pensions, special allowances and health benefits, including free holidays and guaranteed allowances. Chernobyl benefits deprive other areas of public spending of resources, but scaling down benefits or targeting only high-risk groups is unpopular and presents political problems.

Given significant reduction of radiation levels during past twenty years, governments need to revisit the classification of contaminated zones. Many areas previously considered to be at risk are in fact safe for habitation and cultivation. Current delineations are far more restrictive than demonstrated radiation levels can justify.

The report identifies the need to sharpen priorities and streamline the programs to target the most needy, noting that reallocating resources is likely to face “strong resistance from vested interests". One suggestion calls for a “buy out” of the entitlement to benefits in return for lump sum start-up financing for small businesses.

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Frequently Asked Chernobyl Questions

1. what caused the chernobyl accident.

On April 26, 1986, the Number Four RBMK reactor at the nuclear power plant at Chernobyl, Ukraine, went out of control during a test at low-power, leading to an explosion and fire that demolished the reactor building and released large amounts of radiation into the atmosphere. Safety measures were ignored, the uranium fuel in the reactor overheated and melted through the protective barriers. RBMK reactors do not have what is known as a containment structure, a concrete and steel dome over the reactor itself designed to keep radiation inside the plant in the event of such an accident. Consequently, radioactive elements including plutonium, iodine, strontium and caesium were scattered over a wide area. In addition, the graphite blocks used as a moderating material in the RBMK caught fire at high temperature as air entered the reactor core, which contributed to emission of radioactive materials into the environment.

2. How many people died as an immediate result of the accident?

The initial explosion resulted in the death of two workers. Twenty-eight of the firemen and emergency clean-up workers died in the first three months after the explosion from Acute Radiation Sickness and one of cardiac arrest.

3. How many people were evacuated?

The entire town of Pripyat (population 49 360), which lay only three kilometres from the plant was completely evacuated 36 hours after the accident. During the subsequent weeks and months an additional 67 000 people were evacuated from their homes in contaminated areas and relocated on government order. In total some 200 000 people are believed to have been relocated as a result of the accident.

4. What are the major health effects for exposed populations?

There have been at least 1800 documented cases of thyroid cancer children who were between 0 and 14 years of age when the accident occurred., which is far higher than normal. The thyroid gland of young children is particularly susceptible to the uptake of radioactive iodine, which can trigger cancers, treatable both by surgery and medication. Health studies of the registered cleanup workers called in (so-called “liquidators”) have failed to show any direct correlation between their radiation exposure and an increase in other forms of cancer or disease. The psychological affects of Chernobyl were and remain widespread and profound, and have resulted for instance in suicides, drinking problems and apathy.

5. What radioactive elements were emitted into the environment?

There were over 100 radioactive elements released into the atmosphere when Chernobyl’s fourth reactor exploded. Most of these were short lived and decayed (reduced in radioactivity) very quickly. Iodine, strontium and caesium were the most dangerous of the elements released, and have half-lives of 8 days, 29 years, and 30 years respectively. The isotopes Strontium-90 and Caesium-137 are therefore still present in the area to this day. While iodine is linked to thyroid cancer, Strontium can lead to leukaemia. Caesium is the element that travelled the farthest and lasts the longest. This element affects the entire body and especially can harm the liver and spleen.

6. How large an area was affected by the radioactive fallout?

Some 150,000 square kilometres in Belarus, Russia and Ukraine are contaminated and stretch northward of the plant site as far as 500 kilometres. An area spanning 30 kilometres around the plant is considered the “exclusion zone” and is essentially uninhabited. Radioactive fallout scattered over much of the northern hemisphere via wind and storm patterns, but the amounts dispersed were in many instances insignificant.

7. How was this area cleaned up after the accident?

Emergency workers (liquidators) were drafted into the area and helped to clean up the plant premises and the surrounding area. These workers were mostly plant employees, Ukrainian fire-fighters plus many soldiers and miners from Russia, Belarus, Ukraine and other parts of the former Soviet Union. The exact number of liquidators is unknown because there are no completely accurate records of the people involved in the clean-up. The Russian registries list approximately 400,000 liquidators as of 1991 and approximately 600,000 people were granted the status of “liquidator”. These 600,000 individuals received special benefits because of their involvement, on- and off-site, in tackling the accident’s aftermath. The duties of the liquidators varied. They worked on decontamination and major construction projects, including the establishment of settlements and towns for plant workers and evacuees. They also built waste repositories, dams, water filtration systems and the “sarcophagus”, which entombs the entire fourth reactor to contain the remaining radioactive material.

8. Was the rest of Europe/the world affected?

Scandinavian countries and other parts of the world were affected by the radioactive releases from Chernobyl. Caesium and other radioactive isotopes were blown by wind northward into Sweden and Finland and over other parts of the northern hemisphere to some extent. During the first three weeks after the accident, the level of radiation in the atmosphere in several places around the globe was above normal; but these levels quickly receded. No studies have been able to point to a direct link between Chernobyl and increased cancer risks or other health problems outside the immediately affected republics of Ukraine, Belarus and the Russian Federation.

9. What happened to the environment and animals after the accident?

Mutations did occur in plants and animals after the plant explosion. Leaves changed shape and some animals were born with physical deformities. Despite the increased radiation levels, rare species are now returning in large numbers to the area. These animals include beavers, moose, wolves and wild boar, plus species of birds.

10. Is it safe to visit the area now?

One may certainly visit the Chernobyl area, including even the exclusion zone, which is a 30 kilometre radius surrounding the plant, all of whose reactors are now closed. Although some of the radioactive isotopes released into the atmosphere still linger (such as Strontium-90 and Caesium-137), they are at tolerable exposure levels for limited periods of time. Some residents of the exclusion zone have returned to their homes at their own free will, and they live in areas with higher than normal environmental radiation levels. However, these levels are not fatal. Exposure to low but unusual levels of radiation over a period of time is less dangerous than exposure to a huge amount at once, and studies have been unable to link any direct increase in cancer risks to chronic low-level exposure.

11. What was done to ensure the safety of other RBMK reactors, so that this scenario will not present itself again?

Lessons learned from the accident were a significant driving force behind a decade of IAEA assistance to the countries of Central and Eastern Europe and the former Soviet Union. Much of this work focused on identifying the weaknesses in and improving the design safety of VVR and RBMK reactors. Upgrading was performed on all RBMK units to eliminate the design deficiencies which contributed to the Chernobyl accident, to improve shutdown mechanisms and heighten general safety awareness among staff. Just as important as the design safety work has been the focus on operational safety and on systems of regulatory oversight.

12. How do the inhabitants live now?

There are 187 small communities in the exclusion zone that remain virtually abandoned to this day. A few inhabitants chose to return to their homes in the exclusion zone, but children are not allowed to live in this area. The evacuated population lives mainly in newly constructed towns such as Slavutich in areas with very little or no contamination.

13. What will happen to the plant now that it is closed?

On December 15, 2000, the last reactor in operation at the Chernobyl site was shut down and the phase of decommissioning began. This involves the removal and disposal of fuel and wastes, decontamination of the plant and the area surrounding it, including any soil and water that may be radioactive. There are three retired reactors to be decommissioned on site, a project expected to take several decades. The project will be conducted under the supervision of the Ukrainian government. The IAEA will assist by providing planning, engineering and administrative advice. The fate of the fourth reactor where the tragic accident occurred in 1986 is as yet undetermined.

14. What is the state of the protective shelter built around the fourth reactor?

Under extremely hazardous conditions, thousands of "Liquidators" worked to contain the remains of the fourth reactor. The shelter surrounding the reactor was completed less than six months after the explosion during peak radioactivity levels. The massive concrete and steel "Sarcophagus", quickly constructed using "arms length" methods, has deteriorated over the years, creating a potentially hazardous situation. Several repairs were made to the current shelter, including the stabilisation of the ventilation stack and reinforcement of the roof. In addition, a plan for the construction of a more secure and permanent structure to be built around the existing Sarcophagus was drafted; work has already begun on the infrastructure of this new shelter. The plan, called the Shelter Implementation Plan, is a project of the Chernobyl Shelter Fund. Both efforts, whose combined expected expenditures over the next eight or nine years exceed $765 million, are administered by the European Bank for Reconstruction and Development.

In Focus: Chernobyl
The Chernobyl Forum: 2003-2005

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Chernobyl Disaster

On the morning of 26th April, 1986, the unit 4 reactor at the Chernobyl Nuclear Power Plant in Pripyat, Ukraine exploded, releasing large amounts of radiation in the surrounding region. Ukraine was part of the Soviet Union then, which would have long-term consequences for the super-state in the years to come.

Along with the Fukushima Reactor Incident in Japan, The Chernobyl Disaster is the worst nuclear disaster to have occurred.

Now with the Russian invasion of Ukraine in full swing, the fate of the Chernobyl power plant hangs in the balance as the Russian army had surrounded the perimeter of the plant on 24th February 2022, preventing maintenance work from continuing.

For now this article will give details of the timeline of the events that took place on that fateful day as well as the impact of the disaster within the context of the IAS Exam .

Chernobyl Disaster- Download PDF Here

Timeline of the Chernobyl Disaster

On April 25, 1986, the Chernobyl Power plant had reached 50% capacity in power generation. When another power plant in the region went offline, a request was made in the afternoon of April 25 and further power down was allowed after 10 PM.
At 12:05 AM on April 26, the power was at around 23%. 30 minutes later the power fell to a near-zero level, probably due to a change of regulator.
At 01:00 the power stabilized to 6% and it was decided that the test would be run at that level.
Everyone went to their instruments and at 01:23:04 the turbine generator run down test began. Everything went completely normal.
At 01:23:40 the Senior Reactor Chief Control Engineer L.F. Toptunov pressed the emergency shutdown button as planned to end the test.
Instead of the plant shutting down, there was a power surge which jumped from 7% to 17%. The power surge continued beyond normal levels as a result, the automatic control rods suffered damage and they chammed.
At 01:23:47 AM, the fuel channels ruptured and the reactor exploded.

What was the cause of the Chernobyl Reactor Explosion?

The reactor had several design flaws which made the reactor unstable to begin with at the time of the test. The interaction of hot fuel with the cooling water led to fragmentation in the fuel along with rapid steam production causing pressure to build up.

The pressure build up caused the 1000 tons cover plate of the reactor to become detached, rupturing fuel channels and jamming the control rods. The intense steam generation spread through the entire core, which was fed by water dumped due to the rupture of the emergency cooling mechanisms. This caused a steam explosion and released fission products into the air.

A few seconds later, a second explosion blasted fragments from the fuel tower. These fragments included hot graphite which was lethal to touch.

Impact of the Chernobyl Disaster

The accident resulted in the largest radioactive release into the environment ever recorded . large quantities of radioactive dust was released into the atmosphere for 10 days, which would have adverse social and economic effects for the populations of Belarus, Ukraine and Russia.

All the xenon gas, half of iodine, caesium, 5% of remaining radioactive material was released in the incident. The released material was carried by dust and debris but the remaining lighter material was carried over by winds to Russia, Belarus and to some extent Scandinavia and rest of Western Europe

The town of Pripyat in its entirety was evacuated on 27 April. About 45,000 residents were relocated to safe-zones. By 14 May about 116,000 people who were within a 30-kilometre radius had been evacuated. A few of these returned to unofficially live within the contaminated zone with adverse effects to their health.

Following the disaster, more than 220,000 people were resettled into safe zones which had little to no contamination. The initial Chernobyl exclusion zone of 30 kms was further extended to cover 4300 square kilometres. The extension of the safe zone was to protect from the extensive radiation that had blanketed the region.

Frequently Asked Questions about Chernobyl Disaster

What caused the chernobyl disaster, is chernobyl still active, how many people died in the chernobyl accident.

To know more about other Government Exams , visit the linked article. For more preparation materials they can refer to the links given in the table below:





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Three Mile Island and Chernobyl: What Went Wrong and Why Today's Reactors Are Safe

Authors: Jack Spencer and Nicolas Loris

Select a Section 1 /0

This Saturday marks the 30th anniversary of the partial meltdown of the Three Mile Island (TMI) nuclear reactor. This occasion is a good time to consider the advances in nuclear power safety since that time and discuss the misinformation about this incident and the 1986 nuclear accident in Chernobyl, Ukraine, which is often associated with TMI.

Three Mile Island : What Happened

On March 28, 1979, a cooling circuit pump in the non-nuclear section of Three Mile Island's second station (TMI-2) malfunctioned, causing the reactor's primary coolant to heat and internal pressure to rise. Within seconds, the automated response mechanism thrust control rods into the reactor and shut down the core. An escape valve opened to release pressure but failed to close properly. Control room operators only saw that a "close" command was sent to the relief valve, but nothing displayed the valve's actual position. [1] With the valve open, coolant escaped through the pressurizer, sending misinformation to operators that there was too much pressure in the coolant system. Operators then shut down the water pumps to relieve the "pressure."

Operators allowed coolant levels inside the reactor to fall, leaving the uranium core exposed, dry, and intensely hot. Even though inserting control rods halted the fission process, the TMI-2 reactor core continued to generate about 160 megawatts of "decay" heat, declining over the next three hours to 20 megawatts. [2] Approximately one-third of the TMI-2 reactor was exposed and began to melt.

By the time operators discovered what was happening, superheated and partially radioactive steam built up in auxiliary tanks, which operators then moved to waste tanks through compressors and pipes. The compressors leaked. The steam leakage released a radiation dose equivalent to that of a chest X-ray scan, about one-third of the radiation humans absorb in one year from naturally occurring background radiation. [3] No damage to any person, animal, or plant was ever found. [4]

The Outcome

The local population of 2 million people received an average estimated dose of about 1 millirem--miniscule compared to the 100-125 millirems that each person receives annually from naturally occurring background radiation in the area. Nationally, the average person receives 360 millirems per year. [5]

No significant radiation effects on humans, animals, or plants were found. In fact, thorough investigation and sample testing of air, water, milk, vegetation, and soil found that there were negligible effects and concluded that the radiation was safely contained. [6] The most recent and comprehensive study was a 13-year evaluation of 32,000 people living in the area that found no adverse health effects or links to cancer. [7]

Technological Improvements and Lessons Learned

A number of technological and procedural changes have been implemented by industry and the Nuclear Regulatory Commission (NRC) to considerably reduce the risk of a meltdown since the 1979 incident. These include:

Plant design and equipment upgrades, including fire protection, auxiliary feedwater systems, containment building isolation, and automatic plant shut down capabilities;
Enhanced emergency preparedness, including closer coordination between federal, state, and local agencies;
Integration of NRC observations, findings, and conclusions about plant performance and management into public reports;
Regular plant performance analysis by senior NRC managers who identify plants that require additional regulatory attention;
Expansion of NRC's resident inspector program, whereby at least two inspectors live nearby and work exclusively at each plant;
Expanded performance- and safety-oriented inspections;
Additional accident safety equipment to mitigate and monitor conditions during accidents; and [8]
Establishment of the Institute for Nuclear Power Operators, an industry-created non-profit organization that evaluates plants, promotes training and information sharing, and helps individual plants overcome technical issues.

Chernobyl : What Happened

Seven years after the incident at Three Mile Island, on April 25, 1986, a crew of engineers with little background in reactor physics began an experiment at the Chernobyl nuclear station. They sought to determine how long the plant's turbines' inertia could provide power if the main electrical supply to the station was cut. Operators chose to deactivate automatic shutdown mechanisms to carry out their experiment. [9]

The four Chernobyl reactors were known to become unstable at low power settings, [10] and the engineers' experiment caused the reactors to become exactly that. When the operators cut power and switched to the energy from turbine inertia, the coolant pump system failed, causing heat and extreme steam pressure to build inside the reactor core. The reactor experienced a power surge and exploded, blowing off the cover lid of the reactor building, and spewed radioactive gasses and flames for nine days.

The episode was exacerbated by a second design flaw: The Chernobyl reactors lacked fully enclosed containment buildings, a basic safety installation for commercial reactors in the U.S. [11]

Chernobyl was the result of human error and poor design. Of the approximately 50 fatalities, most were rescue workers who entered contaminated areas without being informed of the danger.

The World Heath Organization says that up to 4,000 fatalities could ultimately result from Chernobyl-related cancers. Though these could still emerge, as yet, they have not. The primary health effect was a spike in thyroid cancer among children, with 4,000-5,000 children diagnosed with the cancer between 1992 and 2002. Of these, 15 children unfortunately died. Though these deaths were unquestionably tragic, no clear evidence indicates any increase in other cancers among the most heavily affected populations.

Interestingly, the World Health Organization has also identified a condition called "paralyzing fatalism," which is caused by "persistent myths and misperceptions about the threat of radiation." [12] In other words, the propagation of ignorance by anti-nuclear activists has caused more harm to the affected populations than has the radioactive fallout from the actual accident. Residents of the area assumed a role of "chronic dependency" and developed an entitlement mentality because of the meltdown. [13]

Technology Improvements and Lessons Learned

Comparing the technology of the nuclear reactor at Chernobyl to U.S. reactors is not fair. First, the graphite-moderated, water-cooled reactor at Chernobyl maintained a high positive void coefficient. While the scientific explanation [14] of this characteristic is not important, its real-life application is. Essentially, it means that under certain conditions, coolant inefficiency can cause heightened reactivity. In other words, its reactivity can rapidly increase as its coolant heats (or is lost) resulting in more fissions, higher temperatures, and ultimately meltdown. [15]

This is in direct contrast to the light-water reactors used in the United States, which would shut down under such conditions. U.S. reactors use water to both cool and moderate the reactor. The coolant keeps the temperature from rising too much, and the moderator is used to sustain the nuclear reaction. As the nuclear reaction occurs, the water heats up and becomes a less efficient moderator (cool water facilitates fission better than hot water), thus causing the reaction to slow down and the reactor to cool. This characteristic makes light water reactors inherently safe and is why a Chernobyl-like reactor could never be licensed in the U.S.

Given the inherent problems with the Chernobyl reactor design, many technological changes and safety regulations were put in place to prevent another Chernobyl-like meltdown from occurring. Designers renovated the reactor to make it more stable at lower power, have the automatic shutdown operations activate quicker, and have automated and other safety mechanisms installed. [16]

Chernobyl also led to the formation of a number of international efforts to promote nuclear power plant safety through better training, coordination, and implantation of best practices. The World Association of Nuclear Operators is one such organization and includes every entity in the world that operates a nuclear power plant.

Myths Persist

The circumstances, causes, and conditions of the Chernobyl meltdown are far removed from the American experience. Important lessons should be taken from both accidents. Thankfully, many improvements in the technology and regulatory safety of nuclear reactors are among them.

Jack Spencer is Research Fellow in Nuclear Energy and Nicolas D. Loris is a Research Assistant in the Thomas A. Roe Institute for Economic Policy Studies at The Heritage Foundation.

[1] World Nuclear Association, "Three Mile Island: 1979," March 2001, at http://www.world-nuclear.org/info/inf36.html (March 26, 2009).

[2] Smithsonian Institution, National Museum of American History, "Three Mile Island: The Inside Story," at http://americanhistory. si.edu/tmi/tmi03.htm (March 26, 2009).

[3] American Nuclear Society, "What Happened and What Didn't in the TMI-2 Accident," at http://www.ans.org/pi/resources/sptopics /tmi/whathappened.html (March 26, 2009).

[4] U.S. Nuclear Regulatory Commission, "Fact Sheet on the Three Mile Island Accident," http://www.nrc.gov/reading-rm/doc-collections/fact-sheets/3mile-isle.html (March 26, 2009).

[5] United States Department of Energy, Office of Civilian Radioactive Waste Management, "Facts About Radiation," OCRWM Fact Sheet , January 2005, at http://www.ocrwm.doe.gov/factsheets/doeymp0403.shtml (November 6, 2008).

[6] Nuclear Regulatory Commission, "Fact Sheet on the Three Mile Island Accident."

[7] World Nuclear Association, "Three Mile Island: 1979."

[8] Fact Sheet on the Three Mile Island Accident" Nuclear Regulatory Commission at http://www.nrc.gov/reading-rm/doc-collections/fact-sheets/3mile-isle.html (June 24, 2008).

[9] For full description of what caused the accident at Chernobyl, see Richard Rhodes, Nuclear Renewal (New York: Penguin Books, 1993), ch. 5.

[10] World Nuclear Association, "Chernobyl Accident," May 2008, at http://www.world-nuclear.org/info/chernobyl/inf07.html (March 26, 2009).

[11] Simon Rippon et al., "The Chernobyl Accident," Nuclear News , June 1986, at /static/reportimages/5484F39EEAE25F81A8685A27103E7A0A.pdf (March 26, 2009).

[12] Press release, "Chernobyl: The True Scale of the Accident," World Health Organization, International Atomic Energy Agency, and U.N. Development Programme, September 5, 2005, at http://www.who.int/mediacentre/news/releases/2005/pr38/en/print.html (November 6, 2008).

[13] World Nuclear Association, "Chernobyl Accident."

[14] "Neutron Kinetics of the Chernobyl Accident," ENS News , Summer 2006, at http://www.euronuclear.org/e-news/e-news-13/neutron-kinetics.htm (March 27, 2009).

[15] International Atomic Energy Agency, "The Chernobyl Accident: Updating of INSAG-1," 1992, at http://www-pub.iaea.org/MTCD /publications/PDF/Pub913e_web.pdf (August 27, 2008).

Senior Research Fellow for Energy and Environmental Policy

Former Deputy Director, Thomas A. Roe Institute

The best environmental outcomes are achieved through innovation, economic freedom, respect for private property rights, and the primary role of states in environmental protection.

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