In 1986, in the heart of Ukraine, the Chernobyl nuclear reactor exploded, releasing 400 times more radiation than the Hiroshima Bomb. It was the world's worst nuclear disaster. Thirty workers died, 50,000 people fled the nearest city, and radioactive fallout made an area larger than Long Island a no-go zone. Hastily, a so-called "sarcophagus" was built to contain the radioactive materials that lingered at the site after the explosion. But 30 years later, the sarcophagus is crumbling, and another disaster at Chernobyl looms. Now, an international team of engineers is racing the clock to assemble one of the most ambitious superstructures ever built—an extraordinary 40,000 ton, $1.5 billion dome to encase the crumbling remains of the Chernobyl nuclear reactor. Battling arctic winter weather—and lethal radiation—this is the inside story of the epic race to build Chernobyl's MegaTomb.

Water. Turn on the faucet and it's always there. Without it we perish. But how safe is our tap water? In this special report narrated by Joe Morton, NOVA investigates what happened in Flint, Michigan, when local officials changed the city's water source to save money, but overlooked a critical treatment process. As the water pipes corroded, lead leached into the system, exposing the community—including thousands of children—to dangerous levels of poison. NOVA uncovers the science behind this manmade disaster— from the intricacies of water chemistry to the biology of lead poisoning to the misuse of science itself. NOVA follows ordinary citizens and independent scientists who exposed the danger lurking in Flint's water and confronted those who turned a blind eye. And discover the disturbing truth that reaches far beyond Flint—water systems across the country are similarly vulnerable. How can we protect ourselves from poisoned water?