north korea s claim of testing a hydrogen bomb is false. here s what josh kirby said moments ago. we have consistently made clear we ll not accept north korea as a nuclear armed state. so want to be speaking with former ambassador to the u.n. bill richardson in a moment but beginning with colleague frances rivera with a closer look at hydrogen bombs, frances. certainly. a lot of people asking what exactly is a hydrogen bomb. it is called a thermonuclear weapon and use fusion. that s when atoms fuse together to release energy and hydrogen bombs can be hundreds times more destructive than atomic bombs. atomic bomb splitting a larger in two and here it fuses two atoms into a larger one and just how strong can be they be?