Nuclear Power

Nuclear fusion is a fuel source mentioned across the Fallout series.

Mentions
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 * Nuclear propulsion: After the introduction of fission-powered cars, fusion engines started to dominate the market. After the war, if the cars are damaged, their engines may explode. Batteries also became common, as fusion energy cells allowed them to be easily recharged on the go.  After the Great War, most fission-powered vehicles were volatile, potentially exploding if struck.
 * Power generation: Home nuclear reactors were built under the "Fission Pal" brand. Vaults also used fission generators for power generation.
 * Nuclear weapons: Fission could produce extremely powerful explosions in a relatively compact package. A fission-based weapon is found in the Mojave Wasteland. The United States also developed man-portable nuclear catapult, the M42 Fat Man, capable of delivering miniature nuclear munitions at range.
 * Portable power generation: The dominant form of power generation were portable fusion generators, such as the ones produced by GDA Fusion for household power generation. This kind of technology was also developed after the Great War by certain wasteland organizations, like Rivet City.
 * Microfusion power units are also sometimes referred to as batteries, especially when installed in appliances. These have the same effect and can provide a lasting supply of energy and keep the device independent of the existing energy grid.
 * Robotics: Fusion piles were used to power certain advanced robot types, such as the Robobrain and Assaultron combat robots.
 * Fusion core: A standardized high-grade, long-term nuclear battery used in a variety of military and civilian applications.
 * Large scale energy generation: One of the major potential uses of fusion energy, pre-War United States experienced some limited success with scaling the technology up to fusion generators, capable of powering entire buildings and providing backup power for Vaults. Nuka-Cola Corporation paired multiple fusion reactors to meet the energy demands of Nuka-World, the corporation's flagship amusement park. Mass Fusion was developing an experimental reactor before the Great War that could provide power at a large enough scale to replace conventional fission power plants. However, their work was never completed. The key obstacle was the energy required to trigger the reaction and make it self-sustaining. Mass Fusion's chief achievement was the creation of the beryllium agitator, which would allow the fusion reaction to be jumpstarted much more easily. It is possible to start the reactions conventionally, although doing so requires prohibitively large amounts of energy: Robert House would require the power output of the restored Hoover Dam to restart Lucky 38's reactor. Another issue, especially with systems used in non-standard role like the Prydwen, is cooling.  A sustained reaction requires a constant supply of coolant, which can be problematic to obtain.
 * The military used fusion power to a great extent. The Appalachian Automated Launch System in particular reduced on a combination of onsite fusion reactors and megacells to provide power to its nuclear silos, with the most common types used being military-grade Class-VIII and Class-IV fusion reactors connected in a closed circuit, capable of serving as the silos' primary power source indefinitely. Vault-Tec profited from its role as a strategic defense contractor, obtaining compact fusion power systems from the military for use in its facilities. -->

Behind the scenes
The Fallout Bible comments on a fusion research increase in 2060.