What are the chances of a nuclear attack in our current lifetimes today?

with over 30,000 nuclear warheads on this planet and a few going out to terrorists, and with 3 false-alarm scares in which a countdown was initiated to launch all nuclear weapons from their silos to the U.S. and russia....on a 1-100% chance what do u think the chances are of a nuclear bomb detonating in our current lifetimes?