The Power of the Atom

 is a Fallout 3 quest. It is also an Xbox 360 and PC achievement.

Objectives and walkthrough
It is given to you by sheriff Lucas Simms, who wants you to disarm the the nuclear bomb in the middle of Megaton or by Mister Burke, who wants you to help him detonate it, as his employer, Allistair Tenpenny, considers it a blight on the landscape of the Capital Wasteland. Burke can be found in Moriarty's Saloon in Megaton casually sitting in the corner.

If you warn Simms of Mr. Burke's plan, Simms will attempt to arrest him. One of two things can happen. As Simms turns to lead Mr. Burke to jail, Mr. Burke pulls a silenced 10mm Pistol on him. If you don't act fast, Simms is killed, and although you can kill Burke afterwards, he says his friends will avenge him. If you are quick enough, you can kill Burke as soon as he pulls out his gun. To do this, be ready to enter VATS the instant Burke draws and try to take him out in one shot; if it takes two shots, Burke can still kill Simms. However, if Lucas Simms dies you can still complete the quest by talking with his son, Harden Simms, after disarming the bomb.

Afterwards, you gain Karma, and Simms thanks you for watching his back. If you play as a female character and have the Black Widow perk you can seduce Burke into getting another person to do the job and taking you out of the city, he will even send you love letters.

Rig Megaton's atomic bomb to explode
To do it, you have to put a Fusion Pulse Charge given to you by Burke inside the bomb. Your Explosives skill must be 25 or higher for you to attempt it; Mentats can be used to boost your statistic.

It has been confirmed that the Japanese version of Fallout 3 does not have this quest; Mr. Burke will not appear and the player cannot get the Fusion Pulse Charge. The only options are to disarm the nuke or ignore it.

Report to Mister Burke in Tenpenny Tower
After rigging the bomb, meet Burke at Tenpenny Tower, which is southwest of Megaton. There you can observe the explosion from a safe distance together with Burke and Tenpenny.

Disarm Megaton's atomic bomb
Lucas Simms wants you to disarm Megaton's bomb. Your Explosives skill must be at least 25 to attempt this. If you are successful you get a cash reward and the keys to your own Megaton shack. The cash reward is usually 100 caps, but with a successful use of your speech skill on Lucas (before you actually disarm the bomb) you can talk him into 500 caps instead.

By equipping the Raider Blastmaster Helmet (+5 to skill) and/or using Mentats (+5 to PE, which results in a +10 to skill) it's possible to disarm the bomb even with minimal base skill.

(After disarming the bomb, many mercs appear in your path because there's a reward for your head by Allistair Tenpenny)

To get some Mentats, go and find Leo. He is mostly at the Water Plant. If you successfully use Speech on him, he will give his stash away for free.

You can also find Mentats in the Vault 101 Overseer office.