On April 26, 1986, Soviet engineers at the Chernobyl nuclear power plant were conducting a safety test . Doomed by a fatal design flaw and pushed to the limit by human negligence, reactor 4 exploded amid an attempted shutdown during a routine procedure, setting off a chain of events that ultimately released radioactive material hundreds of times greater than that of the atomic bomb dropped on Hiroshima.

Although the accident occurred north of Kyiv , Ukraine , near the border with Belarus, radioactive fallout was soon detected throughout northern and central Europe. Yet the Soviets did what they could to prevent the spread of information that would reveal the true horror of what had occurred.

For decades, researchers, political leaders and advocacy groups have worked to uncover the story of the explosion.…