Watch historic footage from Chernobyl, Ukraine, site of the world’s worst nuclear power plant disaster, and learn about a new structure being built to prevent radiation from escaping into the environment, in this media gallery from NOVA: Building Chernobyl’s MegaTomb. Thirty years after the Soviet government first sealed Chernobyl’s damaged reactor and contained the harmful gases, two French construction companies joined forces to build a massive arch to slide over the original structure and confine the radioactive debris. An American company is also developing robotic cranes suspended from the arch to later dismantle the reactor. This resource is part of the NOVA Collection.