Learn about gamma rays, including how they travel and their potential impact on the human body at different distances from a radioactive source, from a series of animations in this video from NOVA: Building Chernobyl’s MegaTomb. Thirty years after a 1986 nuclear reactor explosion released lethal radiation into Ukraine’s environment, engineers are building a new structure. Designed to contain radiation from the reactor’s unspent uranium fuel, a massive arch will replace “the sarcophagus,” the name given to the steel-and-concrete shelter hastily built to seal the reactor just after it exploded. To reduce worker exposure to high levels of gamma radiation, the arch is being constructed 300 yards away from the sarcophagus. This resource is part of the NOVA Collection.