What Happened in the Chernobyl Disaster? Chernobyl Disaster Details

Before we get to the bone part of the issue, it is necessary to talk about nuclear power plants and how nuclear energy is produced; During nuclear power generation, neutrons hit uranium-235 cores in reactors. A uranium-235 nucleus swallows a neutron, turning into uranium-236, which is very unstable and divides immediately. This fission event results in new neutrons and energy. The energy generated in this way is called "nuclear energy". Newly emerged neutrons hit other Uranium-235 nuclei, causing them to split. In this way, energy is produced continuously. This event is called chain reaction, and this is how "nuclear energy" is obtained.

Where is Chernobyl?

In its real name; The Vladimir Ilyich Lenin Nuclear Power Plant, or Chernobyl Nuclear Power Plant, is an RMBK(High Power Channel-type Reactor) nuclear reactor that opened in 1970 in northern Ukraine, near the kiev city of Pripyat.

Chernobyl Chernobyl

What Happened That Night at the Chernobyl Nuclear Power Plant?

The security systems were deliberately disabled to avoid blocking reactor power. Reactor power was reduced to 25% below its capacity to carry out the experiment. When this procedure went according to plan, the reactor power level dropped below 1%. So the energy had to be cut off gradually. But 30 seconds after the experiment began, an unexpected energy wave was encountered. The reactor's emergency system (which was supposed to stop the chain reaction) did not work. There was a sudden heat spike in the reactor's fuel, and there was a huge explosion. The 1,000-ton hatch that covered the reactor blew up. As the heat soared above 2000°C, the fuel rods melted. That's when the graphite that covered the reactor caught fire, continuing to burn for nine days, causing huge amounts of radiation to be released into the environment. The accident released more radiation than the nuclear bomb that deliberately dropped on Hiroshima, Japan, in August 1945.


What was the purpose of the test at the plant?

The operating team planned to test whether the turbines could generate enough energy to keep the refrigerant pumps running until the emergency diesel generator is activated in the face of a possible power loss.

How to Prevent a Nuclear Leak

Initial attempts to extinguish the burning reactor included firefighters responding to the reactor with cold water. That effort was ended 10 hours later. More than 30 military helicopters flew over the burning reactor from April 27 to May 5. A mixture of 2,400 tons of lead, 1,800 tons of sand and boron was released from these helicopters to contain the fire and trap radiation. These efforts did not yield results, but in fact made the situation even more dire: The heat accumulated under the materials left by the helicopters. With the radiation scattered around the environment, the temperature in the reactor increased once again. In the final phase of the fire fight, the reactor core was cooled with nitrogen. The fire and radioactive emissions were only brought under control on May 6.


Try Steps

Reduction of reactor power to 700-1000 MW th,

Directing all steam production to one of two turbines,

Decommissioning one of the turbines,

Use of refrigerant pumps as loads to transfer the deflation energy of the turbine-generator system,

Observance of voltage drop.

With Detailed Narration

At 01:00 on April 25, the power of the reactor began to be reduced. At 1:00 p.m., reactor power was reduced to 50%. As a result of the test, one of the turbines was disabled, all steam was shipped to the other turbine. The emergency cooling system has been disabled. Due to energy needs, the reactor was activated for 9 hours in this case. Power down at 11:10 p.m. It's starting to go down to 700 MW th.

April 26, 00:28 Low power local automatic power control is difficult, so global auto power mode has been switched, but the power level has dropped to 30 MW th because the power stop setting is not set to 700 MW th. Steam production in the heart decreased and Xenon concentration increased.

At 1:00 a.m., more control bars were pulled up than operating instructions allow. The reactor could only be stabilized at 200 MW th power because the excess reactivity was too low. Although the operation of RBMK reactors at this power level is inconvenient in terms of safety, it was decided to conduct the experiment.

At 01:03, two recirculation pumps were activated, which were on the bench. The increased flow amount caused a decrease in steam production, decreased water levels in steam separators and reduced system pressure. The control bars were pulled even higher to meet the negative reactivity generated by the decrease in the amount of steam.

At 01:19, the amount of feed water flow was increased to three times the normal value to increase the water level in the steam separators.

At 01:20, the amount of steam approaching zero in the cooling channels brought the cooler temperature closer to the saturation temperature throughout the entire channel.

At 01:19:58, steam bypass valves were closed to normalize system pressure.

At 01:22:10, it was decided that the water level in the steam separators had come to its normal value and the supply water flow was abruptly reduced to 2/3 of the thermal equilibrium value. Already close to saturation temperature, the cooler temperature rose and began to boil in the canals.

At 01:22:10, the control bars were pulled down to keep the power level constant against the positive reactivity generated by the steam production that started suddenly.

01:22:45 Steam production has been stopped, system pressure has been restored to the desired value. Neutron flux was found to accumulate in the upper reaches of the heart, leaving less negative reactivity than safety criteria predicted to stop the reactor immediately. In this case, the reactor should have been stopped immediately, but the decision was made to continue the experiment.

At 01:23:04, the steam valve to turbine 8, which was earmarked for the experiment, was closed. Already the safety system that automatically stopped the reactor was shut down, so the system pressure increased, the amount of coolers passing through the heart began to decrease, which led to the boiling starting from the channel entrance. In addition, the reactor was in an unstable area in terms of operating power and thermohydrolic.

At 01:23:21, the power was found to be rising slowly.

At 1:23:40 a.m., the emergency stop signal caught fire in the control table. The operator pressed the reactor stop button and the control rods began to move downwards.

At 01:23:44, the power level reached 100 times the nominal value in 4 seconds. The slow rate at which the control bars fell did not prevent the power from rising.


As a result of the uncontrolled rise of power, fuels overheated, the fuel envelope melted, hot parts came into contact with water, causing a steam explosion. The shock of the explosion lifted the 1,000-ton reactor cover, the control rods popped out of the heart, about 30% of the fuel in the heart melted and disintegrated. A few seconds after the first explosion, there was a second explosion. Although the reason for this is not fully understood, it is suggested that it may be the result of a number of chemical reactions, such as graphite-vapor interaction.

What are the current consequences of the Chernobyl Disaster?

After the disaster, countries in the region experienced increases in rates of thyroid cancer, leukemia, other types of cancer, cataracts and congenital pathological disorders in infants. In addition to psychological disorders, problems arose due to exclusions in social relations. 120,000 people in groups exposed to high levels of radiation were at risk of dying from cancer. Even in a 2011 study 25 years after the accident, 93 percent of the milk examined identified long-lasting isotope cesium-137 well above the acceptable level. By 2004, 4,000 children under the age of 18 had cases of thyroid cancer in Ukraine, Russia and Belarus. According to official reports, between 9,000 and 30,000 to 60,000 people have contracted the deadly types of cancer caused by Chernobyl, according to independent scientists.

Chernobyl Disaster Map


How was the Republic of Turkey affected by the disaster?

On April 28, it was heading towards the southern and central regions of Scandinavia with north-west winds. On Saturday (May 3rd), the contaminated air mass, along with much of Europe, swept through Bulgaria and Greece into Thrace. The contaminated air mass, which drifted east from Chernobyl with a second oscillation, crossed the Black Sea from the north of the Crimean Peninsula on May 7-9 and reached the north-eastern coast of Turkey.

The movement of the radioactive cloud was caused by current atmospheric conditions and prevailing wind directions. Therefore, the radioactive effect did not show a homogeneous distribution. This resulted in the largest nuclear reactor accident ever caused most of Turkey to emerge unaffected. However, the effects that create economic, social and political problems all over the world continue despite the years since the accident.



Precipitation in the affected countries during the passing of the cloud is the most important reason why that country is exposed to radioactive contamination. Therefore, Turkey felt the effect of radioactivity caused by the Chernobyl reactor mainly due to rainfall in thrace and eastern Black Sea regions during the periods when it was above the cloud, especially in some areas of the Black Sea Region where hazelnut, tobacco and tea were produced. Therefore, measures to mitigate radiation effects were taken for parts of Thrace and the Black Sea regions.

Against the very short-lived I-131 radioisotope in Thrace during the transition period of the radioactive cloud, in the affected areas, animals in the pasture are kept in barns to prevent eating grass affected by radioactive precipitation and fed with uncontagged dry and artificial feed; a number of measures were intervened, such as collecting some contaminated milk (in Edirne and its region) and making white cheese.

Radioactive cesium, which has a much longer physical half-life than radioactive iodine, was especially struggled in tea, the most important agricultural product of the Black Sea Region. Tea, which is the indispensable habit of most Turkish people, was successful in eliminating the effects of radioactive contamination as a result of this audit program, which resulted in the destruction of 58,000 tons of tea, taking into account a great economic loss to prevent it from causing speculative interpretations, although it is not harmful to health by controlling it.

How the Soviet Union Intervened in the Accident

The Soviet Union did not publicly report the true extent of the disaster in the first few days to prevent the seeming panic in the country, officials said. Senior plant managers who tried to cover up the truth also played a part in this (They were then tried and punished.) As of April 27, pripyat, a city of 49,360 people 132 kilometers east of Kiev, the closest settlement to Chernobyl, was evacuated. In the following weeks and months, 67,000 indigenous people in areas contaminated with radioactive material were evacuated on a state order. By May, authorities had extended the restricted area to 30 kilometers. The reactor's highly radioactivity remnants were covered with a solid arch roof made of steel and concrete to prevent damage they would continue to inflict. After the explosion, more than 600,000 Soviet citizens took part in efforts such as extinguishing fires, cleaning the area from radioactive pollution and building arch roofs, either by sacrificing themselves for what they wanted or because they were deployed.


Number of Casualties Announced and Undisclosed

A report by the International Atomic Energy Agency examined the environmental consequences of the accident. According to the UNSCEAR report, 64 out of 4,000 people who were exposed to high doses of radiation from the accident by 2008 were confirmed to have died as a result of radiation. The Chernobyl Forum compiled information on 200,000 emergency responders, 116,000 rescued people and 270,000 evacuees from contaminated areas. When the deaths of 50 emergency responders who died shortly after the accident due to acute radiation syndrome and those who died from thyroid cancer and radiation-related cancer due to radiation were combined, the number of deaths was 3940. An estimated nine of them were children and died of leukemia, but the crucial point is that they are not children. The government of the Soviet Union has always concealed the real weakness with its data that misleals the reports and does not give the actual figures.

What Was Done to Prevent a Disaster Like Chernobyl From Happening Again?

The Chernobyl explosion was followed by important work to identify weaknesses of RBMK-type reactors and improve design safety. In order to eliminate the design flaws that were part of the Chernobyl accident, all RBMK reactors in other Soviet republics at the time were inspected and strengthened. In addition, closing systems that did not function as expected during the accident at Chernobyl were developed and a number of new inspection mechanisms were created.


Are there people residing near Chernobyl today?

The 20-mile evacuation site around Chernobyl's infamous fourth reactor is still deserted. However, some 2,000 locals voluntarily returned to their abandoned homes in and around Pripyat, preferring to live in poor conditions rather than leave their land.


In 2016, one of the region's 90-year-old locals explained, "The secret to longevity is not to leave the land where you were born, even if you have been poisoned." However, authorities do not allow children to reside in the area.

Visiting Chernobyl

Although some of the radioactive isotopes released into the atmosphere by the explosion still retain their presence near Chernobyl, they are at a level that the body can tolerate if exposed for a short period of time. Therefore, visits to towns around Chernobyl are allowed. There are even regular tours to these areas. For those who want to breathe the air of 'abandoned creepy Soviet towns', Ukraine's doors are wide open. It is possible to book a tour online for fees starting at $89 and experience this unusual place.


Sarcophagus Protection

A huge "sarcophagus" (hatch) was built of concrete around reactor 4, which was damaged after the explosion. This sarcophagus, which encloses the damaged nuclear reactor, was designed to prevent further radiation from being released into the atmosphere. At first, it was intended to install a cooling plate to keep the damaged reactor under control, preventing the still-hot reactor fuel from drilling a hole in the foundation of the reactor. Coal miners were deployed to open this tunnel under the reactor. On June 24, 400 coal miners drilled a 168-meter-long tunnel under the reactor. Construction of the sarcop cantin surrounding the reactor was completed in November 1986, using 7,000 tons of steel and 410,000 m3 of concrete.


The Life of Sarcophagus Protection

The sarcophagus was designed to operate only for 20 to 30 years. The biggest problem is its instability. The rusting of the bearing beams of the lahtin, which was hastyly completed, threatens the integrity of the structure. The water seeps through the holes above the roof into the sarcoph, and after exposure to radiation, it mixes from the reactor floor into the ground below. Scientists predict that chernobyl itself would cause a nuclear disaster as great as chernobyl itself due to the precision of the protection shield. We don't have a definitive estimate of the amount of fuel left inside the reactor, but our estimates suggest there's 95% more than the initial content. It also contains thousands of square meters of nuclear waste from particles of the dilapidated reactor building and radiation soil thrown into the sarcophage.

Chernobyl Array and Unpublishation Request

The Russian government reacted to the Chernobly series, which resonated widely around the world. The Communist Party of Russia has called for the show to be taken off the air in the country. Stating that the show is full of made-up scenes, the Russian government announced that they will be shooting a new version in which the truth will be told. Sergey Malinkovic, chief executive of the Communist Party of Russia, announced that they had applied to the Russian Federal Information Technology and Mass Communication Supervision Agency, referring to the series they want banned.

"The real tragedy is that the Chernobyl series is an ideological manipulation of HBO," he said.

Sabotage Allegations

As we mentioned in the title, it is only a claim, but having points that make sense also leaves questions in one's mind. Due to the Cold War between the United States and the Soviet Union from 1947 to 1991, the Chernobyl Plant was positioned near a radar system. In the event of a possible bombing, missile attack, precautions could be taken because the radar systems were in operation, special protection systems had already been designed. There was nothing wrong with that. But there was a factory built near the reactors. This factory was used in the production of basic-use items fed from reactors, and the factory was adjacent to the nuclear warehouse. So the dangerous chemicals and the factory devices that were accessible to everyone were at the same point. At this risky point, he said, the Cold War literally turned into a hot front with close contact, and these seemingly innocent factories were positioned there to cover up a nuclear missile project, "Grossman."

Sabotage Allegations and CIA Virus Attack

The CIA, the U.S. Central Intelligence Agency, was aware of this tiny-looking giant project of the Soviet Union. At the time, CIA officials admitted that the United States was trying to render some systems dysfunctional by conducting virus attacks on Soviet computer systems. The disaster at Chernobyl was the tragic result of what the CIA described as 'failed attempts' in those years. The CIA succeeded in the virus attacks, and the cause of the vital Fourth Reactor at Chernobyl was unknownly in a failure position, and then that explosion occurred.

20 Years Before the Chernobyl Disaster; Mayak Nuclear Power Plant Disaster

In September 1957, a massive radioactive cloud spread hundreds of miles away in an explosion at the Secret Mayak nuclear fuel plant near Kishtim in the Ural Mountains. Some areas were evacuated after the blast, which affected nearly 250,000 people. Dozens of workers at the nuclear plant and more than 200 others in the surrounding area died of acute radiation syndrome.

"The Soviet Union was able to remain silent in Kishtim, the biggest nuclear disaster to date, unlike Chernobyl," says US journalist Adam Higginbotham, author of "Midnight in Chernobyl." Historian Serhii Plokhii, director of Harvard University's Ukraine Research Institute, says Kishism is a smaller-scale disaster than Chernobyl, but it has caused a major nuclear pollution. On September 29, 1957, engineers at the Mayak nuclear plant began their shifts as usual. It seemed like it was no different than any other day.

In a documentary about the accident, published years later, chemical engineer Anna Sharova described what happened on the day of the explosion: "We had shifts between 1pm and 7pm. We were working in the lab and there wasn't a lot of work because it was Sunday. "Suddenly we heard a lightning bolt, the windows exploded, the windows of the doors were smashed. When we looked out, we saw a giant cloud." Anna heard the explosion was caused by overheating in one of the tanks containing high-density nuclear waste.


However, employees at the nuclear plant were not allowed to ask questions about what happened. No one could say a word about the accident to anyone else. No information could go beyond the walls. Historian Serhii Plokhii says silence at the time was "the standard protocol of the Soviet Union." Mayak's involvement as part of the Soviet military program increased the pressure for secrecy. "There was a close connection between the production of atomic bombs and the construction of reactors manufactured by the army for the use of civilians," Plokhii says. The construction of mayak, the site where the first Soviet nuclear bomb was produced, was launched in great secrecy in 1946. Almost a city was built for the accommodation of workers working in Mayak. The city, whose first name was Chelyabinsk-40 (City-40), was later called Ozerks, but it was not included in the USSR maps. When the nuclear reactor exploded in 1957, no one knew about Mayak or the Ozerks. Not only the Soviets, but the United States remained silent about what happened.

America's Awareness

"The Americans, despite the traces of the explosion and some findings of radiation pollution, said nothing because they were preparing for giant nuclear projects at the time. They didn't want to ring the alarm bells." This secrecy lasted nearly 20 years – until a Russian dissident spoke about the accident. Through his work in the late 1950s, Zhores Medvedev was the first scientist to inform the international community about serious nuclear accidents in the Ural Mountains. Biochemist and historian Medvedev told the BBC Witness programme in September 2016: "There was not enough system for measuring the temperature in the reactors. That's when the regulation system in one of the tanks stopped, and when the heat reached a certain level, the tank exploded. "Exactly how many people were affected by the blast, how many people died, the numbers related to them were never disclosed.

" Medvedev, who researched nuclear in a laboratory in Moscow, was one of the few Soviet experts to investigate nuclear pollution in the region. He was among the few people in the world who knew what really happened in Kishtim. Opposition scientist Medvedev later went into exile in London, England, and nearly 20 years later published an article in 1976 in which he talked about the Kishtim disaster. However, John Hill, then head of the UK Atomic Energy Agency, denied the allegations in the article. The European country was unhappy with the negative news about nuclear energy. Medvedev did not back down and struggled to uncover more concrete information about what happened in Kistim. He has published more documents that could show the impact on humans, animals and plants.


In his 1980 book "Nuclear Accidents in the Urals", he compiled all these findings. John Hill has denied wrongdoing, but after the Chernobyl disaster, the nuclear industry became more open to criticism. Before Medvedev died in November 2018, he always argued that until the nuclear waste problem is solved, the world will not be ready for nuclear power generation.