Fission Battery (Fallout 3)

Fission Battery is one of the ingredients in constructing the Railway Rifle. Fission Batteries can be found all over the wastes, usually in Tool Boxes or destroyed Robots.

Note
The Fission Battery is required for the Reilly's Rangers (quest) near the end of the quest at the top of the Statesman Hotel. One can be found inside the Statesman Hotel but it is much easier to keep one extra in inventory and bring it along for the quest.