The international service of Czech Radio 
29-11-2020, 11:21 UTC

Accident at Chernobyl Nuclear Power Plant
On 26th April 1986 at 1.23.49 AM Moscow time an accident occurred at the ChNPP Unit 4. The accident was the severest one in the entire history of the nuclear power industry. The reactor core and the safety systems were destroyed and the majority of the core bearing structures was damaged.
The reactor started releasing radiation to the environment and the adjoining area was contaminated by active core fragments with pieces of fuel rods, graphite, and structural elements. The first dose values measured around the destroyed Unit 4 and throughout the ChNPP territory were startling. Close to the Unit 4 the gamma-exposure rate reached 2000 R/hour. Dose rates in the reactor exceeded 5000 R/hour. Only 31 victims were officially recorded by the Soviet government at the time of the accident.
The radioactive particles spreaded throughout Europe in serious amounts and in lesser amounts across the entire northern hemisphere, including Canada and the United States. The Kremlin for almost three days thought they could keep it a secret from the world and cover up the accident. On April 30 Moscow newspaper Pravda breaks Soviet silence and announced the Chernobyl accident. The Soviet government was secretly approaching Sweden, West Germany and Britain for advice on putting out the graphite fire in nuclear reactor core. It took 12 days and 10,0000 tons of sand, lead, clay and boron dropped from helicopters to diminish the fire which was pouring 150 million curies of radioactivity into the air. The helicopter pilots died from radiation and the helicopters became se radioactive that they had to be abandoned with other radioactive vehiclesand equipment in the Zone. Water was channelled through the remainder of the emergency cooling system to cool the core.
The thousands of people participated in the cleanup and building of the sarcophagus. The cleanup people, who were called liquidators, were often army conscriptors and soldiers age 18 to 30 who had no choice and had insufficient protective clothing.