Vault Star super-reactor

The Vault-Tec Vault Star super-reactor is a high-performance energy source.

Background
It was developed by the Vault-Tec corporation for use in vaults and other facilities requiring a high powered energy source, such as the automated missile silos of the Appalachian Automated Launch System or the Vault 94 G.E.C.K. wing. It consists of three distinct elements: The core, containing the nuclear rods, a shield that provides radiation protection and additional connections, and a platform for mounting the entire reactor.

It is classified by the military as a class-VIII reactor and is used in automated facilities, such as the aforementioned Appalachian missile silos, to provide power indefinitely. To maintain redundancy, it's usually paired with multiple Class-IV fusion reactors, mega cells, and connections to civilian infrastructure. Vault-Tec instead classifies it as a Class-VI fusion reactor, with an operational lifespan of 200+ years. Both can be maintained by automated systems, with little to no need for human oversight.