TASS FACTBOX. April 26, 2021 marks 35 years since the Chernobyl nuclear power plant disaster (near the town of Pripyat, the Kiev Region of the Ukrainian Soviet Socialist Republic, currently the Vyshgorod district of the Kiev Region of Ukraine). It went down in history as the worst-ever nuclear power plant catastrophe.

Chernobyl Nuclear Power Plant's History

On June 29, 1966, the USSR Council of Ministers issued a decree approving a plan for commissioning nuclear power plants through 1977. The document specifically included the construction of nuclear power plants in Ukraine. One of the sites was selected 4 km from the village of Kopachi and 15 km from the city of Chernobyl, near the Yanov railway station (Chernigov-Ovruch line).

On February 4, 1970, construction began of a new city of Pripyat, 3 km from the future nuclear power plant site, for the plant's maintenance personnel. The city had a projected population of up to 85,000. In May of that year, excavation work began on the site of the foundation for the first power unit.

On August 1, 1977, the first fuel assembly was loaded into Unit 1, which housed an RBMK-1000 nuclear reactor, marking the beginning of its physical startup. The power startup took place on September 26 of that year. On September 9, 1982, the plant experienced its first accident. During a test run of Unit 1 following scheduled maintenance, one of the reactor's fuel channels failed, deforming the graphite stack in the core. No one was injured. The damage from the emergency took approximately three months to eliminate.

The 1986 Disaster

In the early hours of April 26, 1986, tests were being conducted at Unit 4 of the Chernobyl Nuclear Power Plant, during which the reactor's emergency cooling system was shut down as planned. The reactor could not be safely shut down; at 1:23 a.m. Moscow time, an explosion and fire occurred in the unit. The accident was the worst disaster in the history of nuclear power: the reactor core was completely destroyed, the building partially collapsed, and a significant release of radioactive materials into the environment occurred. One person - pump operator Valery Khodemchuk - died in the explosion (his body was not recovered from the rubble). That morning, automation system engineer Vladimir Shashenok died in the medical unit from burns and a spinal injury.

An intense fire lasted ten days, during which time the total release of radioactive materials into the environment amounted to approximately 14 exabecquerels (approximately 380 million curies). An area of more than 200,000 square kilometers was contaminated, 70% of which was in Ukraine, Belarus, and Russia. The most contaminated areas were the northern regions of the Kiev and Zhitomir regions of the Ukrainian SSR, the Gomel region of the Byelorussian SSR, and the Bryansk region of the RSFSR. Radioactive fallout occurred in the Leningrad region, Mordovia, and Chuvashia. Subsequent contamination was noted in the Arctic regions of the Soviet Union, Norway, Finland, and Sweden.

Official Reaction of the Soviet Authorities

The first brief official report of the emergency was released by TASS on April 28, 1986. According to former General Secretary of the Communist Party’s Central Committee Mikhail Gorbachev, in a 2006 interview with the BBC, the May 1 celebrations in Kiev and other cities were not cancelled because the country's leadership did not have a full picture of what had happened and feared likely panic among the population. It was only on May 14 that Gorbachev made a televised address in which he revealed the true scale of the incident.

Disaster Management

Immediately after the accident, the plant's operations were suspended. The disabled reactor, containing burning graphite, was covered from helicopters with a mixture of boron carbide, lead, and dolomite. After the active phase of the accident had subsided, it was covered with latex, rubber, and other dust-absorbing solutions. (By the end of June 1986, approximately 11,400 tons of dry and liquid materials had been dropped.)

On April 27, the city of Pripyat (47,500 people) was evacuated, followed by the population of the 10-kilometer exclusion zone around the Chernobyl Nuclear Power Plant in the next few days. In total, approximately 116,000 people were resettled from 188 villages within the 30-kilometer exclusion zone around the plant during May 1986. Between July and November 1986, the "Shelter" facility - a concrete sarcophagus over 50 meters high and measuring 200 by 200 meters - was constructed to cover Unit 4 of the Chernobyl Nuclear Power Plant. After this, radioactive emissions ceased.

Probe into the Causes

The government panel of inquiry into the causes of the disaster placed the responsibility on the management and personnel of the Chernobyl Nuclear Power Plant. The International Atomic Energy Agency’s International Nuclear Safety Advisory Group (INSAG) confirmed the findings of the Soviet commission in its 1986 report.

Medical Consequences

According to a report by the expert group of the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR), approximately 600 personnel at the nuclear power plant site received high doses of radiation on the day of the accident. Of these, 134 were exposed to particularly significant radiation, and 28 died of radiation sickness within a few months of the accident. Another 22 people from this group died by the end of the 2010s from various causes not necessarily related to radiation exposure.

Currently, the National Radiation and Epidemiological Registry (NRER) of Russia lists more than 710,000 people exposed to radiation as a result of the Chernobyl disaster.

The NPP’s Further Operation

Following decontamination work, three units were restarted - Unit 1 on October 1, 1986, Unit 2 on November 5, 1986, and Unit 3 on December 4, 1987. On October 2, 1986, the Central Committee of the Communist Party and the Council of Ministers adopted a resolution to build a new city for Chernobyl NPP employees, 50 km east of the damaged nuclear power plant. In 1987, the city was named Slavutich.

After the collapse of the Soviet Union, the Chernobyl NPP was integrated into the power grid of independent Ukraine.

Memorable Day

Since 2004, the CIS member states have observed April 26 as International Day of Remembrance of the Victims of Radiation Accidents and Disasters. Since 2012, April 26 has also been observed in Russia as the Day of Participants in the Elimination of the Consequences of Radiation Accidents and Disasters and Remembrance of the Victims of These Accidents and Disasters.