THE START OF THE INCIDENT

The Chernobyl nuclear disaster began early in the early hours of Saturday 26 April 1986 within the Chernobyl Nuclear Power Plant. An explosion and fire released large quantities of radioactive contamination into the atmosphere, which spread over much of Western USSR and Europe.

The disaster began during a systems test at reactor number four of the Chernobyl plant. There was a sudden surge of power output, and when an emergency shutdown was attempted a more extreme spike in power output occurred, which led a reactor vessel to rupture and a series of explosions. These events exposed the graphite moderator of the reactor to air, causing it to ignite.

The resulting fire sent a plume of highly radioactive smoke into the atmosphere and went on to drift over large parts of the western Soviet Union and Europe. According to official post-Soviet data about 60% of the radioactive fallout landed in Belarus.

Legasov was called in almost immediately to lead the investigation due to his expertise in radiochemistry. He was also chosen due to his statement that pointed to the problems of the RBMK-1000 reactors and the risks of operating such nuclear reactors, And thus he was put in charge to investigate the disaster and develop measures to control the spread of radiation.