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The Vault - Fallout Wiki
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For the Fallout 4 main quest, see Mass Fusion (quest).
Mass Fusion
Mass Fusion logo.png
Company data
Fusion wells
Fusion engines
Fusion cores
CountryUnited States of America
HeadquartersMass Fusion building
LocationsMass Fusion disposal site
Mass Fusion containment shed

Power. People. Perfect. Mass Fusion

Mass Fusion was a pre-War energy provider and leader in the safe handling and disposal of nuclear waste.


Before the Great War, Mass Fusion was Boston's premiere utility, providing power to all of Massachusetts, providing a lucrative line of fusion wells, engines, and cores.[1][2] It was founded in 2043 by Karl Oslow, after spending six years cutting his teeth as an electrical engineer with Poseidon Energy. Oslow decided he'd had enough with traditional methods of energy distribution and founded Mass Fusion to begin realizing his vision: Power to the people.[3] His Cleanpower Initiative focused on developing affordable sources of energy based on nuclear principles, and by 2053 his efforts bore fruit, as the first "fusion" distribution boxes and sources of power entered the market. Through cunning and dedication, Oslow's company eventually cornered the energy market in Massachusetts, becoming the primary power provider for the state by 2070.[4]

In truth, the company was lying through its teeth about selling clean, fusion power. The junction boxes and plutonium wells were all fundamentally fission-based, provided with lead shielding to protect the users from irradiation. Unfortunately, imperfect shielding was all too common and radiation poisoning was a real risk among consumers. The company, of course, vehemently denied these accusations. Nausea, vomiting, hair loss, radiation burns? That's not their Cleanpower, they would say.[5] It wasn't until 2066 and the unveiling of the first power armor fusion cell[6] that the company truly started providing fusion power, but even then, legacy infrastructure was too commonplace to be cheaply replaced. Mass Fusion continued to operate containment facilities[7] and dumping grounds in rural Massachusetts, hiding the radioactive waste from prying eyes.[8]

However, Mass Fusion and its CEO were on the verge of making a breakthrough: The Cleanpower Initiative would finally create the first sustainable, clean fusion reactor. Through the use of a beryllium agitator, this reactor would be able to provide over 22,000 megawatts to Massachusetts and allow the company to finally stop lying. The brainchild of Karl Oslow and Noel Chandrich, the project was accelerated following Oslow's contacts with the military and the request for a power source beyond anything made before. Chandrich's protest went unheard and the project was accelerated. Thanks to Kathy Hathaway's work on graphene shielding, the installation of the agitator was made possible[9] and the switch was finally thrown on July 30, 2077.[10] By August 29, the reaction was confirmed as stable.[11] Chandrich was fired a week later, with a non-compete agreement to boot, while Oslow let the jingoism get the better of him... Making Mass Fusion different from Poseidon in name only.[12]

Perhaps for this reason, Poseidon Energy was attempting to buy out Mass Fusion shortly before the War cut their operations short.[13]



Power. People. Perfect. Mass Fusion

We Keep Boston Running



Signs and displays


The products of Mass Fusion appear in Fallout 4 and Fallout 76.


  1. Fallout 4 Vault Dweller's Survival Guide Collector's Edition p.477-479: "[15.01] Mass Fusion Building
    Before the war, Mass Fusion was the primary power supplier to Boston and most of the Commonwealth. It is the tallest building in Boston. With the proceeds from an enormously lucrative line of fusion wells, engines, and cores, this structure—their corporate headquarters—was built. Since the war, the structure has fallen into disrepair, though the reactor level hasn’t yet been breached.
    At ground level, Gunners fight through the rubble-strewn streets. Should you arrive on the roof (when the quest is active), prepare to fight your chosen rival faction, and hunt down a few choice items (including a Nuka Cherry). Beware the oil, gas leaks, and explosive barrels, or use them to your advantage."
    (Fallout 4 Vault Dweller's Survival Guide Map)
  2. Fallout 4 loading screen hints: "Before the Great War, Mass Fusion was Boston's premiere utility, providing power to all of Massachusetts."
  3. Mass Fusion building terminals; Executive Research Lab Terminal, Personal IntraMail 07-30-77: "To: K. Oslow
    From: N. Chandrich, Research Lead
    As per your instructions, the Beryllium Agitator has been installed in our primary reactor on sub-level 01. I've also increased security on all of the keyreaders in the building, so you'll need your executive keycard handy if you want to use any of the elevators.
    I'd like to go on official record that I am opposed to accelerating the project's schedule. I find it disturbing that current events (e.g. global unrest) hasn't had an effect on your decision. While I realize your recent contact with the U.S. Military may be making it difficult to follow a rational course of action, I strongly urge you to reconsider.
    I thought this is exactly why you left Poseidon, Karl."
  4. Mass Fusion building terminals; Customer Service Terminal, Company History: "In the spring of 2043, Karl Oslow dared to dream of limitless power being supplied to countless homes from a single power plant. After spending six years years cutting his teeth as an electrical engineer with Poseidon Energy, Mr. Oslow decided he'd had enough with traditional methods of energy distribution and founded Mass Fusion to begin realizing his vision.
    After only a decade of research, Mass Fusion's Cleanpower Initiative transitioned from dream to reality and the switches were thrown. The people of Boston embraced this new technology, and by 2070, Mass Fusion became the primary power provider for all of Massachusetts. Now, as we look to the future, Mass Fusion hopes to bring ten more power plants online in the next several decades.
    To open a new account and begin enjoying the benefits of your nuclear tomorrow, please see one of our Mass Fusion Customer Service Representatives today!"
  5. Mass Fusion building terminals; Customer Service Terminal, I'm Feeling Sick: "Many individuals assume that the fusion distribution box in their home may present a danger to its occupants. While the device gives off a trace amount of radiation, we can assure you that it's completely safe. If you're experiencing the following symptoms, we give you our word you that they are in no way related to our Cleanpower technology: Nausea, vomiting, diarrhea, headache, fever, dizziness and disorientation, weakness, fatigue, hair loss, poor wound healing, low blood pressure, skin flaking or burns."
  6. Fallout Bible 0: "2066 Summer Adding further insult to the Chinese-American relations, the first crude fusion cell is unveiled, one of the results of the Power Armor project. Devices designed for the fusion cell begin to be manufactured. Incorporating fusion power into the general US infrastructure begins, but the process is too slow to supply power to the regions that need it. Nearly thirteen years later, few sections of the United States were supplied with fusion power."
  7. Fallout 4 Vault Dweller's Survival Guide Collector's Edition p.281: "[2.13] Mass Fusion Containment Shed
    Mass Fusion is the leader in the safe handling and disposal of radioactive waste. Except here the place is overrun with Feral Ghouls and spilled barrels. Check the outside balcony for a cooler (Novice). Inspect the supervisor’s terminal (Novice) to unlock the security door. Check the secure area for a toolbox (Novice) and a gate to a steamer trunk."
    (Fallout 4 Vault Dweller's Survival Guide Map)
  8. Fallout 4 Vault Dweller's Survival Guide Collector's Edition p.355: "[5.06] Mass Fusion Disposal Site
    This was the property of Mass Fusion and used as a disposal site for coolants and other liquids. As much of the poisons were buried at this site, pressure has built up and the irradiated pools around the shores of the lake have bubbling gasses. Be wise: Wear radioactive protective gear at all times. Be perceptive: Locate the steamer trunk in the treehouse to the northeast. Be extra perceptive: There’s a Mini Nuke inside the large tire by the yellow digging machine."
    (Fallout 4 Vault Dweller's Survival Guide)
  9. Mass Fusion building terminals
  10. Mass Fusion building terminals
  11. Mass Fusion building terminals
  12. Mass Fusion building terminals
  13. Danse: ""Poseidon Energy was one of the largest power companies on the East Coast. I heard they were trying to buy out Mass Fusion right before the war began.""
    (Danse's dialogue) Note: location comment; Poseidon Energy, generator room - the part past the raider defenses.