The world has survived 520 above-ground nuclear blasts and another 800 underground tests in the last 70 years. The most lethal radioactives go inert the fastest. If/when the roof caves in on the North Korean mountain, only a few dribbles will escape, and the prevailing winds will probably take those dribbles out to sea. You’ll get more extra radiation by going to Denver for a day.
Yep, those overly worried about radioactivity need to get a half-life.