Fire at America's nuclear site, emergency declared as radioactive leak fears erupt

A fire at America's Savannah River National Laboratory in South Carolina triggered a Site Area Emergency, temporary restrictions on air, rail and river traffic, and fears of radioactive contamination. One employee was hospitalised with minor injuries. The fire was extinguished, and officials reported no detectable contamination outside the affected facility. The emergency was lifted later. Why did a fire at a nuclear research laboratory trigger such a serious response? How can radioactive material spread? And what do past nuclear incidents teach us about the dangers of contamination? We examine the incident, the science of radiation, the history of the Savannah River Site and the questions which are yet to answer.