Chernobyl Accident – An Overview

The Chernobyl Accident, caused by a faulty Soviet reactor configuration combined with significant plant operator errors was a direct result of the lack of safety and protection environment. The Chernobyl 4 reactor was damaged by the accident, which killed 30 operators and firefighters within three months and resulted in several more deaths. One person was killed on the spot, while another died in the hospital shortly after.

Chernobyl Nuclear Plant and Location

Located about 130 km north of Kiev, Ukraine, and about 20 km south of the Belarusian border, the Chernobyl Power plant consisted of four nuclear reactors of the RBMK-1000 design, each capable of generating 1,000 megawatts of electricity. Reactors 1 and 2 were built between 1970 and 1977, while reactors 3 and 4 were completed in 1983. At the time of the accident, two new RBMK reactors were under construction at the site. An artificial lake of about 22 km² was built to the southeast of the plant, alongside the river Pripyat, to cool the reactors.

1986 Chernobyl Accident

On April 25-26, 1986, engineers at the Chernobyl nuclear power plant, during routine maintenance, planned to use the downtime to test whether the Chernobyl reactor 4 could still be cooled if the plant lost power. However, they violated safety protocols during the test and removed most of the control rods from the reactor’s core. They also turned off the reactor’s power-regulating mechanism and emergency protection equipment, enabling the reactor to operate at a very low power of 7%. As a result, the reactors became highly unstable, and power surged inside the plant.

The power surge caused a dramatic increase in heat, breaking some of the fuel pressure tubes. The hot fuel particles reacted with water and caused a steam explosion, which lifted the 1,000-metric-ton cover off the top of the reactor, rupturing the remaining 1,660 pressure tubes. Despite attempts to completely shut down the reactor, another power surge set off a chain reaction that resulted in a second explosion which finally exposed the reactor core to the environment. As a result, large volumes of radioactive waste, including the significant short-lived iodine-131 and the long-lived caesium-137, were released into the atmosphere and carried to great distances by air currents.

Firefighters tried to extinguish a number of blazes at the plant, and helicopters were eventually dispatched to drop sand and other materials in an attempt to put out the fires and contain the contamination. However, two plant employees died in the blast on the night of the disaster. Thirty-six hours later, the Soviet Union began evacuating people in the surrounding areas, including the nearby city of Pripyat, which was constructed in the 1970s to accommodate workers at the plant.

Immediate Effect

The fire at the site burned for 10 days, releasing the largest uncontrolled radioactive materials into the environment. As a result, a total of about 350,000 people were eventually evacuated, and a circular exclusion zone based on the nuclear facility with a radius of around 18.6 miles (30 km) was established, which was later modified and extended to cover 4,300 km² in the years following the accident. Within a few weeks, 28 people, including 6 firefighters, died from acute radiation syndrome (ARS). ARS develops when a person is exposed to more than 700 milligrays (mGy) in a short time (usually minutes). Apart from the initial death of 30 people, more than 100 people were injured.

The Soviets, however, refrained from publicizing the nuclear accident and denied its occurrence. But it was too late as the radiation from the meltdown had already travelled as far as Sweden, where workers at another nuclear plant suspected something was happening in the USSR. Finally, on April 28, the Soviets made a brief announcement concerning the accident. The world soon realized something historic had happened. Up to 30% of the 190 metric tons of uranium contained at Chernobyl was now in the atmosphere. The Chernobyl accident caused severe social and economic disruption for vast populations in Belarus, Russia, Ukraine, and to a lesser extent over Scandinavia and Europe.

However, before the remaining three reactors could be restarted, a cleaning up process was carried out to clear the radioactivity at the plant, and about 200,000 people called liquidators from all over the Soviet Union took part in the recovery and clean-up, which was done between 1986 and 1987. The damaged reactor was also covered more permanently during the clean-up. According to a report, the liquidators were exposed to high radiation levels, averaging around 100 millisieverts (mSv). Some 20,000 liquidators received about 250 mSv, with a few receiving approximately 500 mSv. The number of liquidators eventually grew above 600,000, but most only absorbed minor amounts of radiation. The 1000 emergency workers and onsite personnel received the highest doses of radiation during the first day of the accident.

According to the most recent estimate provided by the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR), inhabitants of ‘strict radiation control’ areas (population 216,000) received an average radiation dose of 31 mSv in the years 1986 to 2005. In the ‘contaminated’ areas (population 6.4 million), an average of 9 mSv was recorded.

Long Term Effect

The Chernobyl disaster affected many things; 23% of Belarusian territory was contaminated due to radiation, and about a fifth of its agricultural land was lost. Many trees in an area of about four square miles from the site (known as the Red Forest) were also affected as they turned reddish-brown and died after absorbing high levels of radiation. Essential bacterias were lost, and the environment close to the plant became polluted with dangerous radioactive materials. The disaster likewise hastened the end of the USSR and fueled a global anti-nuclear movement.

In February 2003, the IAEA, in collaboration with seven other UN organizations as well as the competent authorities of Belarus, the Russian Federation, and Ukraine, established what is known as the Chernobyl Forum. The Forum later reported that some European doctors advised pregnant women to have abortions because of radiation exposure and congenital disabilities, even though radiation levels were extremely below those likely to cause teratogenic effects. As a result of such wrong advice, more than 1 million abortions were carried out in the Soviet Union and Europe.

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. Apart from 5000 thyroid cancers that resulted in 15 deaths, the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) has found that “there is no evidence of a major public health impact attributable to radiation exposure two decades after the accident.”

However, the absence of human activity around the shuttered power plant has led to increased wildlife such as elk, wolves, and lynxes. In 2015, scientists estimated there were seven times more wolves in the exclusion zone than in nearby comparable reserves. Many trees have likewise regrown, though scientists have recently discovered signs of increased levels of cataracts and albinism, as well as lower frequencies of helpful bacteria, in some wildlife species in the area. Today, Chernobyl attracts tourists interested in both its history and its danger.

The remains of the Chernobyl reactor, including the 200 tonnes of highly radioactive material deep within it, are now buried inside a massive steel containment structure deployed in late 2016. The steel containment, having been built adjacent and then moved into place on rails,  is 110 meters high, 165 meters long, and spans 260 meters, covering both the unit 4 reactor and the hastily-built 1986 structure. However, containment efforts and monitoring continue, and clean-up is expected to last until at least 2065.


  • Belarus spent 22% of its entire budget dealing with the Chernobyl accident.
  • Despite the Chernobyl accident, Russia has never moved beyond its technology. Russia still has 11 operating RBMK reactors as of 2019.
  • By early 2011, the Chernobyl Shelter Fund, established in 1997, had received €864 million from worldwide contributors for this project and previous work.
  • Around the year 2000, the Chernobyl nuclear power plant was eventually shut down.

The Chernobyl nuclear accident is the world’s worst nuclear accident recorded in history and has been estimated to cost some $235 billion in damages. According to the health effects provided by an annexe to the UNSCEAR 2008 report that was released in 2011, the effects of the Chernobyl accident are many and varied. More than 30 years on, scientists estimate the zone around the former plant will not be habitable for up to 20,000 years. However, the impact of the disaster on the surrounding forest and wildlife remains an area of active research.

Akshay Dinesh

As a student, I love writing articles that teach and guide others. My interests encompass a wide range of educational subjects, and I strive to cover as many topics and explanations as possible in my writing. You can reach me at akshay[at] for any questions.

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