Adds processing of Plutonium, which is created from nuclear fission of Uranium. It can be used to extract even more energy or incinerate enemies with new ammunition.
It seems you don't have the breeder fuel cell unlocked yet. I don't even see MOX fuel in there. And also I see there are some other mods which might affect whether the cells are available to be selected and where in the menu they are placed
Thanks for the answer, yes you are right there is a "collision".
The problem was deeper, 4 mods coexisted together.
I don't know how it's possible, but it's true, they influenced each other.
Problem solved.
