By the way being at ground zero doesn't mean that anyone will take damage from an explosion:
http://www.history.com/news/the-man...wo-atomic-bombs
Around 8:15 that morning, Yamaguchi was walking to Mitsubishi’s shipyard a final time when he heard the drone of an aircraft overhead. Looking skyward, he saw an American B-29 bomber soar over the city and drop a small object connected to a parachute. Suddenly, the sky erupted in a blaze of light, which Yamaguchi later described as resembling the “the lightning of a huge magnesium flare.” He had just enough time to dive into a ditch before an ear-splitting boom rang out. The shock wave that accompanied it sucked Yamaguchi from the ground, spun him in the air like a tornado and sent him hurtling into a nearby potato patch.
He’d been less than two miles from ground zero.