"NARRATOR: In 1986, in what was the Soviet Republic of Ukraine, the Chernobyl nuclear reactor exploded, releasing 400 times more radioactive material than the Hiroshima Bomb. Thirty workers died; 50,000 people fled the nearest city, and the radioactive fallout spread over Europe. It was the world's worst nuclear accident. Thirty years later, its hastily built enclosure is crumbling. In a race against time, engineers are struggling to prevent another catastrophic release of deadly radioactive debris into the environment."