The Power of the Atom

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

Objectives and walkthrough
This quest 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.

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.
 * Note: it is advisable to get the Strength Bobble Head from Lucas Simms' home before you detonate the bomb.

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.

The reason it is not in the Japanese version is because it is considered culturally insensitive to remind people of a time when their cities were bombed, especially since people continue to suffer radiation poisoning effects to this day.

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.

Mr. Burke will give player the privilege to push the button to detonate the bomb. Doing so instantly gives the player a Karma of -1000. If your karma before it was 0 or negative, -1000 karma will instantly lead to the lowest possible karma in the game.

If the Lone Wanderer helps Roy Phillips take over Tenpenny Tower in the quest Tenpenny Tower prior to completing Power of the Atom, Lone Wanderer may still complete Power of the Atom. When you return to the top floor penthouse, you will stumble onto Roy Phillips and Mr. Burke having a conversation. Roy is intimidated by Mr. Burke and the fact that he made his way to the top floor. Roy agrees with Burke on the matter of blowing up Megaton and also states that he could use a man like Burke, thus Burke begins a new partnership with Roy Phillips.

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.

Mr. Burke would leave Megaton after you defuse the bomb. As a result of disarming the bomb, Talon Company mercenaries hired by Mr. Burke will randomly appear to kill you.

Boosting Explosive Skill
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.

To get some Mentats, go and find Leo Stahl. He is at the Water Processing Plant during the night. 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. You can also buy Mentats at Craterside Supply.

Dealing with Mr. Burke
This section of the quest is entirely optional.

You can kill Burke after speaking to him, without talking to Simms first, killing him will result in good karma and you can avoid risking Simms.

Report Mr. Burke to Lucas Simms
After speaking to Burke, a new dialogue option will become available when speaking with Lucas Simms, which can result in him confronting Burke about the plot to destroy Megaton. Take care not to "cry wolf," so to Speak, because he will not believe you if you rescind your initial warning. Lucas Simms will tell you to follow after informing you that you're about to see wasteland justice first hand. Simms will attempt to arrest him. Burke will deny the allegations, but will eventually agree to be detained and suggest that Lucas "Lead the way." As Simms turns to lead Burke to jail, Burke pulls a silenced 10mm Pistol on him.

For some players, probably due to low karma, Lucas Simms will not believe you when you try to report Burke, and tell you to stop bothering him before he arrests you for "disturbing the peace" (although he never actually arrests you).

You can try to save him by killing Burke. 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. If you kill Burke before he kills Lucas, the sheriff will thank you afterward.

The Scoped .44 Magnum at point blank or any other high powered weapon* can kill Burke with only one or two headshots, depending on skills with the weapon you choose, perks (such as Sniper and Gunslinger), luck and chems such as Psycho or certain food. If you're lucky, you can time it so that Burke has started drawing his gun but not fired yet - and thus it is possible to draw his attention so that he turns to face you, giving you extra time to shoot him (which can be crucial even in VATS), instead of shooting Simms. Either way, unless you're completely inept at shooting or have very poor weapons on hand, Burke should not be an issue so long as you can enter VATS fast enough.

(*Whilst Burke might be close enough to take the entirety of a shotgun blast, the use thereof in the bar area is not recommended, as unless you shoot towards the wall rather than over the bar itself as the pellets may strike bystanders. Obviously, explosive weapons are right out. You'll want something accurate and powerful.)

If you don't act fast, Simms is killed. Afterward Mr. Burke gives you a threat and disappears. You can kill Burke before he disappears, he says his friends will avenge him. If you let Burke kill Lucas Simms, then you kill Burke, you can loot both bodies. This will get you a Silenced 10mm Pistol and a Chinese Assault Rifle, plus some caps, ammo, and other assorted items. If Lucas Simms dies you can still complete this quest by talking with his son, Harden Simms, after disarming the bomb.

Neither option will result in a negative reactions from the townspeople, though they may comment "better him than me" if they see it take place.

Seduce Mr. Burke
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.

As a female with the Black Widow perk, you may also seduce him into changing his mind, which results in him sending you love letters, or persuading him to give you 500 more caps upon detonation of the bomb.

It is reported that using the Black Widow Perk to seduce Burke still results in him putting a hit out on you. (I received 4 love letters total then while exploring the area southeast of Tenpenny tower was attacked by 3 hitmen. They wore Talon Company Armor but were labeled as regular hitmen.)

Destroyed Megaton
If you travel to Megaton after you chose to Detonate the atomic bomb, you'll also find the broken remains of the Protectron Robot (Deputy Weld) with its speech unit still functioning. Ironically it still loops the "the bomb is perfectly safe" line just as it had before the incident.

You'll find a blemished Moira Brown who survived the detonation. She explains how it was lucky that she wasn't in the area when the bomb went off, however she was hit by some of the radiation, thus turning her into a ghoul.

The shattered remnants of Megaton itself is normally inaccessible. On the PC, it is possible to use console to again access to the old Megaton. Fast travel to Megaton, then enter the "tcl" console command, then go into the ground, you should see a drainage grate that says it goes to Megaton. Enter this and you will be taken to the version of Megaton as it was before the detonation of the nuke.