On April 26, 1986, in a remote corner of Ukraine, 400 times more radioactive material was released into the atmosphere than Hiroshima. What exactly happened inside the Chernobyl power plant that led to the disaster? That’s the focus of HBO’s mini series “Chernobyl,” which has been nominated for 19 Emmys. Craig Mazin is the creator, writer and executive producer. He’s been nominated for writing.