Rad Absorption (Broken Steel)

 is a perk added to Fallout 3 with the Broken Steel DLC.

With this perk, your Radiation level slowly decreases automatically over time (1 rad every 10 seconds). The actual effectiveness of this perk varies, because mostly, player characters at a level this high will have a house with a My First Infirmary that can instantly cure all rads. It's as simple as fast-traveling to the house, curing all rads, and returning to whence you came, and you won't have wasted a perk.