Dmitry Kalmykov is a Ukrainian scientist who has dedicated his life to investigating environmental disasters, first at Chornobyl and now in Semipalatinsk, Kazakhstan - formerly the Soviet Union's primary nuclear weapons testing site. Against the backdrop of war in Ukraine and the long shadow of a nuclear conflict across the region, Dmitry worries about the possibility of nuclear war becoming a reality. Subscribe to The Guardian on YouTube ► http://bit.ly/subscribegdn The Guardian publishes