On April 25, 1986, the fourth power unit of the Chernobyl NPP was scheduled for an experimental shutdown to study the possibility of using the inertia of the turbine generator in the event of a power loss. Despite the fact that the technical circumstances did not align with the test plan, it was not canceled.
The experiment began on April 26 at 01:23. The situation spiraled out of control. At 01:25, two explosions rang out within an interval of a few seconds. The reactor was completely destroyed. More than 30 fire outbreaks flared up. The main ones were extinguished within an hour, and the fires were completely liquidated by 5:00 AM on April 26.
However, an intense fire later broke out in the central hall of the 4th unit, which was fought with the use of helicopters until May 10.
At the time of the accident, 17 employees were in the building of the 4th power unit. Valeriy Khodemchuk, the senior operator of the reactor hall, died under the rubble. On the afternoon of April 26, adjuster Volodymyr Shashenok died from radiation exposure. Eleven other employees received radiation doses; they all died from radiation sickness by May 20, 1986, in Moscow Hospital No. 6. Another 14 staff members received doses that caused 3rd and 4th-degree radiation sickness.
The day after the accident, a government commission decided on the immediate shutdown of the 1st and 2nd power units and the evacuation of the population of Pripyat (the so-called 10-kilometer zone).
A KGB report stated that as of 8:00 AM on April 28, the radiation level at the 3rd and 4th power units was 1000–2600 microroentgens per second, and in certain areas of the city, it was 30–160. At this point in the document, Volodymyr Shcherbytsky made his now-famous note: "What does this mean?". This eloquently demonstrates that even the highest-ranking officials did not fully comprehend the danger.
Military personnel were immediately deployed for liquidation work. The first to arrive at the scene were several dozen soldiers and officers of the Civil Defense Regiment of the Kyiv Military District with radiation reconnaissance devices and an army kit for equipment decontamination, a mobile unit of chemical troops, and a separate company for radiation and chemical reconnaissance. In total, 600,000 people participated in the liquidation efforts. Due to exposure, many of them fell ill.
Firefighters arrived "with bare hands," without any protective gear, such as special isolating gas masks, which allowed radioactive substances to enter their respiratory tracts. It was the firefighters who stopped another potential disaster—a hydrogen explosion. The total activity of radioisotopes released into the air after the Chernobyl accident was 30–40 times greater than in Hiroshima. Nearly 8.5 million people were exposed to radiation.
The first official local report of the accident appeared only 36 hours later—at noon on April 27, Pripyat radio announced a "temporary evacuation" of the residents of Pripyat, the city closest to the NPP with a population of about 50,000.
The city was divided into 5 sectors. In each, responsible parties were appointed. Staff members went door-to-door, recommending that residents close windows and balconies, turn off electrical appliances, shut off water and gas, and take personal belongings, valuables, documents, and food for the immediate future. Other items, such as dishes, toys, and pets, were not allowed to be taken. From the memoirs of Lyudmila Kharitonova: "The parting with pets—cats, dogs—was tragic. Cats, tails out, looked into people's eyes and meowed; dogs howled, trying to break into the buses. But taking animals was strictly forbidden. Their fur was highly radioactive."
To reduce luggage and prevent panic, people were told they could return home in three days. At 1:50 PM, residents gathered near their building entrances, and buses began arriving at 2:00 PM. By 4:30 PM, the evacuation was complete. 44,500 people were removed. 5,000 remained in Pripyat to carry out urgent work.
On the evening of May 1, the wind from Chernobyl turned toward Kyiv. The radiation background in the city began to rise rapidly. Nevertheless, the parade took place. On May 2, the Soviet leadership decided to evacuate the population from a 30-kilometer zone around the Chernobyl plant—on the 6th day after the accident.
By May 6, more than 115,000 people were evacuated from the 30-kilometer zone. This territory suffered the most from radiation. Later, it became known as the Chernobyl Exclusion Zone, which included the north of the Poliske and Ivankiv districts of the Kyiv region (where the plant, Chernobyl, and Pripyat are located), as well as part of the Zhytomyr region up to the border with Belarus. Hundreds of small villages in the center of the contamination were leveled by bulldozers.
Most people were resettled in neighboring districts of the Kyiv region. For NPP workers and their families, the construction of Ukraine's youngest city, Slavutych, began at the end of 1986. Construction was completed in record time, with the first residents moving in during 1987–1988.
Information policy in the first weeks following the disaster sowed distrust toward the authorities. The government, along with central and republican press and television, maintained silence about the accident until it began to be discussed abroad and it became clear that the accident could not be hidden.
Thus, the first official report in the USSR, under pressure from the international community, was made only on April 28. At 9:00 PM, the main television news program "Vremya" laconically reported: "An accident has occurred at the Chernobyl nuclear power station. One of the atomic reactors has been damaged. Measures are being taken to liquidate the consequences of the accident. Assistance is being provided to the victims. A government commission has been established." It was difficult to understand the true scale of the tragedy from this report.
Similarly, early reports in Ukrainian media were extremely sparse. For instance, the newspaper "Pravda Ukrainy" on April 29, 1986, placed a report from the Council of Ministers of the USSR on the third page: "An accident has occurred at the Chernobyl nuclear power station. One of the atomic reactors is damaged..."
The next day, newspapers provided slightly more detailed but no more informative reports. The first advice on self-protection appeared in "Pravda Ukrainy" on May 9. The article "Recommended Safety Measures" transcribed a radio interview with the then-Minister of Health Anatoliy Romanenko, which stated: "Our main enemy is dust... In recent days, there have been fewer children playing in the streets. This is correct. Although there is practically no direct danger of radiation today, let us protect them primarily from dust."
General Secretary Mikhail Gorbachev addressed the Chernobyl accident only on May 14! The following day, Gorbachev's statement was reprinted by Ukrainian publications.
The Chernobyl disaster became one of the catalysts for the collapse of the USSR. The accident was the last straw that broke the camel's back of human patience. The government's concealment of the truth sowed doubt even among the most loyal supporters.
Furthermore, Moscow's attempts to hide the truth strengthened the opposition national-democratic movement in Ukraine, joined by environmental activists fighting against pollution.
In many regions of Ukraine, people began to hold protest actions against the construction of new and the operation of old nuclear power plants.
The first public organizations formed around the theme of the Chernobyl accident. Soon, two such organizations—"Green World" and the "Chernobyl" Union—turned into a political force.
Despite KGB opposition, on April 26, 1988, the first unauthorized demonstration took place in Kyiv under slogans such as "NPPs out of Ukraine" and "We don't want dead zones." Shortly after, the empire built on lies fell.
Chernobyl also definitively undermined the economic foundations of the Soviet Union.