Survivors called it PIKADON ~ Light then Thunder.
Another good read for all you book worms is "The Day The Bomb Fell" nothing to do with Japanin WWII but a scary ride on the US having wayward Nuclear bombs drop out of aircraft when they weren't supposed to one I think was on US soil with 4 of the 5 fail safes failing leaving one hanging there or 1 step away from a detonation....interesting read.
Recently I just watched a doco on a Titan Missile silo fire in the 80's now that was scary moment the explosions of all the fuel going up not the warhead it blew the 700 tonne silo hatch clean off the warhead landing outside the silo had the bomb detonated then the loss of life would have been horrendous as it was @50 died.
1980 Damascus Titan missile explosion - Wikipedia
Chilling PBS Doc Recounts The Nuclear Accident That Nearly Destroyed A