Nuclear Anomaly

 is a perk added to Fallout 3 with the Broken Steel add-on.

With this perk you erupt into a devastating nuclear explosion whenever your health is reduced to 20 or less. Note that any allies in the vicinity will also suffer the effects of the blast!

Bugs

 * When playing on Normal+ difficulty, you can be killed BY the explosion before the health regain activates. This makes choosing the perk dangerous. (Confirmed on 360)