Everything You Need To Know About Chernobyl

by Yashvardhan Sharma

Yesterday, on 26 April 2020, we marked the 34th International Chernobyl Disaster Remembrance Day. In remembrance of the events that unfolded thirty-four years ago and the families that were affected by this calamity, let us commemorate the survivors and victims of this disastrous event understand what happened.

“The nuclear meltdown at Chernobyl was perhaps the true collapse of the USSR.”

-Erstwhile General Secretary of the Communist Party and Leader of USSR, Mikhail Gorbachev (2005)


It was the cold war era, and the US and Soviet Union (USSR) were engaged in a neverending arms race. Both countries were heavily investing in arms production and development, and after the use of ‘little boy’ and ‘fat man’ by the US in Hiroshima and Nagasaki at the end of World War 2, USSR started investing heavily in nuclear weapons and research.

Soviets tried to catch up with the US by developing the Tsar Bomba in 1961, which was 3,333 times more powerful than the atomic bomb dropped in Nagasaki. However, the US took the lead once again with more advanced and efficient technology.

Amidst this arms race, there was one, arguably, positive side effect- nuclear energy. Both these superpowers were using nuclear energy to generate electricity and hence had set up various nuclear power plans across their nation.

The Working of a Nuclear Reactor

Before we move on to what happened that night, we need to understand two crucial things- the basic functioning of a nuclear reactor and the turbine safety test.

A nuclear power plant essentially produces electricity using steam, which then turns a turbine which produces electricity. In the nuclear reactor, a concept of fission is used. When an unstable element such as Uranium-235, is put together with other U-235 atoms, the neutrons strike it’s surrounding neutrons and the force of this impact releases a tremendous amount of energy. This energy, when controlled, is used to make electricity.

A turbine safety test is extremely crucial in a nuclear power plant. This test is to be run to make sure the safety of the power plant in case of a defect. It ensures the cooling of the core would continue even in the case of a power outage.

If a defect is present, the turbine should slow down but continue to produce electricity. This electricity is necessary to work the circulation pump and control rods and to provide lighting for the control room and control panel.

This supply of electricity is essential for the safety of the reactor, and on no account should it fail. Because it takes twenty seconds for the control rods to reach their most extreme position in the case of a defect, it is of vital importance to know whether the turbine can produce the necessary electricity for those twenty seconds, until the emergency generator is able to take over the supply of electricity.

The Disaster

Now, the Vladimir I. Lenin Nuclear Power Station, or popularly known as Chernobyl was built in December 1983. Remarkably, the test was declared operational just after its construction was complete. While the Soviets celebrated this as a victory, the fact was that the necessary safety checks and tests were ignored. The abovementioned turbine test was one of them.

There are several people who played an extremely vital role in the incident. Victor Bryukhanov, who served as the manager of the construction of the Chernobyl Nuclear Power Plant and the director of the plant from 1970 to 1986; Anatoly Dyatlov, deputy chief engineer of the Chernobyl Nuclear Power Plant and the supervisor of the catastrophic safety test which resulted in the 1986 Chernobyl; and Nikolai Formin, Chief Engineer of the Chernobyl Power Plant.

The safety test had been tried thrice before 26th April 1986 and failed all three times. This test was necessary to ensure efficient working on the power plant even in times of emergencies. So, the administration decided to try this test once again on 25th April 1986.

By 2 pm, the nuclear plant’s power was reduced to half from the standard power of the plant, 3,600 MW to 1,600 MW. At this point in time, the plant was stable and ready to be lowered to 700MW and to comply with the safety test. The test required the power to be lowered to 700MW to check the functioning of the plant in such a scenario.

Then, a call was received by Formin from the power grid officials in Kyiv stating that they cannot afford any further reductions in the power, and, thus, the power in the area cannot be reduced to 700MW for another 10 hours (after midnight). Now, any competent management and administration would have called off the test for another day but that was not the case here. They insisted on holding the test that night and continued to prepare for it.

One major flaw in this decision was the fact that the change in the shift was accounted for. After midnight, the night shift staff was working at the power plant. Now, these guys weren’t nuclear physicists but actually engineers. They were handed out a set of instructions and asked to perform the experiment.

Due to the soviet system and their way of working, the staff couldn’t refuse to follow instructions of their superiors and followed whatever they were asked to do. So, when Dyatlov asked the twenty-five-year-old, Leonid Toptunov, the operator of the night, who joined the plant only four months ago and was responsible for controlling and stabilizing the reactor, to perform this nuclear safety test, he had to do it.

Workstation at the Chernobyl Power Plant

The four Chernobyl reactors were pressurized water reactors of the Soviet RBMK design, or Reactor BolshoMoshchnosty Kanalny (RBMK), meaning “high-power channel reactor.”

Designed to produce both plutonium and electric power, they were very different from standard commercial designs, employing a unique combination of a graphite moderator and a water coolant.

The reactors also were highly unstable at low power, primarily owing to control rod design and “positive void coefficient” factors that accelerated nuclear chain reaction and power output if the reactors lost cooling water. These factors all contributed to an uncontrollable power surge that led to the destruction of Chernobyl 4.

At 01:23:45 that night the power surge caused a sudden increase in heat, which ruptured some of the pressure tubes containing fuel. 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 rest of the 1,660 pressure tubes, causing a second explosion and exposing the reactor core to the environment. The graphite moderator burned for 10 days, releasing a large amount of gamma radiation into the atmosphere.

At 01:30 the first response action by the administration at the plant was to call for the fire brigade, who came from the town of Pripyat, just a couple of miles from the station. Dyatlov also called for the water pumps in the area to be manually opened for it to cool down and refused to believe that the core had been blown off. Initially, it was believed that only the roof had been blown away. Since such an event of the explosion of the reactor’s core had never happened thus it was hard to describe the situation at the time.

Now, using a dosimeter (the device that measures dose uptake of external ionizing radiation) they tried measuring the radiation in the atmosphere which was reported to be 3.6 roentgen. This number wasn’t too high to be an extremely cautious amount, but still dangerous. Little did they realize, the dosimeter they used, it’s upper limit was actually 3.6 roentgen and it could not indicate a higher roentgen count.

When later a larger dosimeter was called, the actual reading of the radiation in Chernobyl was 15,000 roentgen. This new reading is twice the radiation of the Hiroshima atomic bomb, released every hour. If, say, it had been 24 hours since the explosion, they had experienced the same radiation as 48 fat man bombs (Hiroshima bombs).

Explosion at the Chernobyl Nuclear Plant

How were the remains of this radioactive explosion cleaned?

Emergency workers (liquidators) were drafted into the area and helped to clean up the plant premises and the surrounding area. These men were mainly aged 35-40 and were mostly firemen, soldiers, and miners from parts of the erstwhile 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.

Liquidators in their uniforms

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.

Liquidators clearing the graphite from the roof of the plant


“The accident at the Chernobyl nuclear plant…has painfully affected the Soviet people, and shocked the international community. For the first time, we confront the real force of nuclear energy, out of control.”

-Mikhail Gorbachev

The accident caused the largest uncontrolled radioactive release into the environment ever recorded for any civilian operation, and large quantities of radioactive substances were released into the air for about 10 days. This caused serious social and economic disruption for large populations in Belarus, Russia, and Ukraine.

Radiation’s Effects on Personal Health

The United Nations body reviewing the effects of atomic radiation on human health and the environment has said that a quarter of all thyroid cancer cases among patients, who were children at the time of the Chernobyl accident 32 years ago, are “probably” due to high doses of radiation received during and after the event.

Psychological Effects

  • The Chernobyl accident led to extensive relocation of people, loss of economic stability, and long-term threats to health in current and possibly future generations. Widespread feelings of worry and confusion, as well as a lack of physical and emotional well-being, were commonplace. High levels of stress, anxiety, and medically unexplained physical symptoms continue to be reported among those affected by the accident.

  • This has resulted in excessive health concerns or reckless behavior, such as the overuse of alcohol and tobacco, or the consumption of mushrooms, berries, and game from areas still designated as having high levels of radioactive cesium.

Economic Effects

Over the next 30 years, Chernobyl's cost grew to $700 billion due to the following reasons :

  1. The damage directly caused by the accident.

  2. The cost of sealing off the reactor. The initial sarcophagus began crumbling. The European Bank for Reconstruction and Development and a group of foreign donors funded a Safe Confinement building that cost 2 billion euros.

  3. The creation of an exclusion zone of 30 kilometers around the power plant.

  4. The resettlement of 200,000 people.

  5. Health care for many of the 10 million people exposed to radiation.

  6. Seven million people are still receiving benefit payments in Russia, Ukraine, and Belarus. That costs Ukraine at least 5% of its annual budget and Belarus at least 6% of its budget.

  7. Research to find out how to make contaminated food safe.

  8. The monitoring of environmental radiation levels.

  9. Toxic waste clean-up and disposal of radioactive waste.

  10. Removing radioactive material from farmland and forests.

  11. Making up for loss of power from the Chernobyl plant itself. Unit 4 was shut down. Reactors 1, 2, and 3 were restarted in October 1986. They produced power until December 2000.

  12. The cancellation of Belarus’s nuclear power program. Belarus estimates total losses of $235 billion.

The accident couldn't have happened at a worse time. The Berlin Wall came crashing down in 1990, ending the Soviet Union. Both Ukraine and Belarus had been former U.S.S.R. satellite countries.

Now, they were protesting and demanding independence. With the policies of “Glasnost” and “Perestroika” by Gorbachev, the Soviet system was restructured and more liberal by now. Ukraine had been the "breadbasket" of the Soviet world. The accident destroyed this role. There were few small businesses to take its place.

The accident made new business development more difficult. Few companies wanted to invest in an area threatened by radiation. Logically speaking, who would want to buy a product marked "Made in Chernobyl".

Effect on Food Supply

However, the United Nations study found significant shortcomings in the Soviet Union’s implementation of countermeasures. “In the first few weeks, management of animal fodder and milk production (including prohibiting the consumption of fresh milk) would have helped significantly to reduce doses to the thyroid due to radioiodine,” according to the study.

How did Soviet power plants compare with their American counterparts?

“The world has already been overwhelmed by one Chernobyl and one exclusion zone. It cannot afford it anymore. It must learn its lessons from what happened in and around Chernobyl on April 26, 1986.”

Serhii Plokhy, Historian and Professor of Ukrainian history at Harvard University.

A 2004 report by the National Academy of Sciences (NAS)-

“The first key difference is in how the plants are designed and built. All U.S. power reactors have extensive safety features to prevent large-scale accidents and radioactive releases. The Chernobyl reactor had no such features and was unstable at low power levels.”

“Second, federal regulations require extensive emergency preparedness planning for all U.S. nuclear energy facilities. Including:

  • Stringent emergency preparedness plans. Key personnel at all U.S. power reactors work with surrounding populations on an ongoing basis to prepare for orderly and speedy evacuation in the unlikely event of an accident.

  • Alert and notification. Chernobyl plant operators concealed the accident from authorities and the local population, and thus the government did not even begin limited evacuations until about 36 hours after the accident. In the United States, nuclear power plant operators are required to alert local authorities and make recommendations for protecting the public within 15 minutes of identifying conditions that might lead to a significant release—even if such a release has not occurred by that time. The U.S. Nuclear Regulatory Commission posts resident inspectors at every nuclear power plant site to ensure the plants are following federal safety requirements.

  • Protecting the food chain. Since authorities did not promptly disclose details of the Chernobyl accident, many people unknowingly consumed contaminated milk and food. This would not be the case in the United States. As it did following the Three Mile Island nuclear accident in 1979, the federal government would carefully monitor and test food and water supplies that potentially could become contaminated. Under existing federal programs and regulations, the government would quarantine and remove from public consumption any unsafe food or water. In addition, after the accident at the Fukushima Daiichi reactors in Japan in March 2011, the U.S. strengthened protections of the public from contaminated milk and food by conducting specialized training and drills with farmers and agricultural producers.”


  1. https://www.thebalance.com/chernobyl-nuclear-power-plant-disaster-economic-impact-3306335

  2. https://www-pub.iaea.org/MTCD/publications/PDF/Pub1239_web.pdf

  3. https://www.who.int/ionizing_radiation/chernobyl/backgrounder/en/

  4. https://www.iaea.org/newscenter/focus/chernobyl/faqs

  5. https://nei.org/resources/fact-sheets/chernobyl-accident-and-its-consequences

  6. https://www.iaea.org/sites/default/files/25204744759.pdf

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Created by Yashvardhan Sharma and Amogh Narain Agarwal.