Uranium

Category:Resources
Highly radioactive, primarily used in fission-based weapons.
Used in: Missile Launcher modules as a one-time cost, and also consumed in creating the Fission Missile variant on a per-warhead basis once you have researched Fission Missiles.
(spoilers!)
 
Common sources: Bonuses from surveying Anomalies, destroying enemy ships, purchases from Trade factions on the cheap (e.g. CXTA, Kyrnan, or Island Traders).
Remarks: Unless investing heavily in fission-missile combat, you may wish to sell your Uranium for whatever you need the most. The Nimion desire it the most and will pay in Gold ; The Ermyr Defenders and Wiskamug desire it somewhat less and pay in Copper and Yttrium, respectively.