Nerves of Steel (Broken Steel)

 is a perk added to Fallout 3 with the Broken Steel add-on. It also appears as a perk in Fallout: New Vegas.

It increases the regeneration rate of Action Points by 20%.

Fallout: New Vegas
The perk was retooled in Fallout New Vegas to make it far more effective than the lackluster version in Fallout 3. According to the New Vegas GECK the perk now increases the regeneration rate of Action Points by +20%.

Bugs
It has been reported that the perk is non-functional in Fallout 3 on both the PC and Xbox 360 with the version 1.5 patch issued for Broken Steel, but this is inaccurate. While the perk does function, the increase in action point regeneration rate is extremely low (amounting to 1 additional AP per 10 seconds).

PC users can alter the regeneration bonus associated with this perk by using the G.E.C.K. to edit the script DLC03APRegenScript. For users who do not know how to do so, a simple plugin can be found here.

[PC patch 1.20.352] If you don't equip a weapon, this perk will not take effect.