Uranium Nitride - sswelm/KSPInterstellar GitHub Wiki
A fuel used in tier 2 "Sethlans" fission reactors. It can be made with the ISRU Refinery using the Uranium Ammonolysis (which takes UF4 and Ammonia and makes Uranium Nitride).
This fuel should be an improvement over UF4 due to UN2 being safer (partially due to molecular stability and strength) and has a denser fuel potential while also being more thermally conductive than traditional Uranium-235 based fuels. At one time Uranium Nitride was considered as a potential fuel for cars, but that pesky radiation thing was always a lingering concern. Thus, Kerbals decided to utilize it as a reactor fuel for rockets (although nothing limits you from using it for a land vehicle).