Chernobyl is located on the border between Ukraine and Belarus. In April 1986, a testing error caused an explosion at the Chernobyl nuclear power station, releasing 190 tons of radioactive gases. Despite the disaster, Soviet authorities waited over 36 hours to evacuate the area, exposing children and others who remained. The radiation spread over much of the northern hemisphere and contaminated 150,000 square kilometers across Belarus, Russia, and Ukraine, exposing over 7 million people.