How did Jack Bauer survive the nuclear bomb detonation in Season 2? He was near the nuclear bomb when it went off.
Bauer jumps with 1:30 mins left on the counter. Given the plane is a Cessna Caravan that cruises at 210 miles per hour. So if we assume that they were indeed flying at top speed, that's 5.25 miles from the blast radius. Bonus points if Mason decides to crash the plane before detonation to reduce the air burst effect.
View the following Nuclear Blast Effect Calculator if you want the exact juicy nuclear effect radii. Nuclear Effect Calculator of 475 kiloton bomb in the Mojave
Bauer also lands into a valley, with the ground effectively forming too thick a barrier for direct radiation emission to penetrate. So being outside the blast radius and protected from both the air blast and immediate nuclear emission particles, assuming that Jack doesn't stick around to get passive radiation poisoning/cancer, it's not completely outrageous that he survives.
Alternatively perhaps he climbed into a refrigerator, with another certain whip carrying protagonist...