The duration of the heat radiation from the bomb is so short, just a few thousandths of a second, that there is no time for the energy falling on a surface to be dissipated by thermal defusion; the flash burn is typically a surface effect.
Psychiatry - A reversal of the normal fusion of (spec. life and death) instincts
The separation of the life instinct from the death instinct as part of the process of maturing into an adult