The Chernobyl nuclear disaster

In April 1986 a reactor exploded at the Chernobyl nuclear power plant in Ukraine, in the USSR, causing the worst nuclear accident ever. Sergii Mirnyi was in charge of a monitoring unit which measured radiation levels in the 30 km exclusion zone around the plant.

(Photo: The Chernobyl plant shortly after the explosion in 1986. Credit: Getty Images)