Today's Close-Up S2017E23 - Banning Nuclear Arms: Ideal vs. Reality

The world's first treaty placing a legal ban on nuclear weapons was passed on July 7th. But nuclear states such as the United States, along with Japan and 27 other countries under the US nuclear umbrella, didn't sign it. Can a "nuclear-free world" be realized? We hear what the head of the UN's disarmament office has to say.