I have installed both mods. Realistic Reactors and Plutonium Energy. Since I don't know where this bug is originated, I have opened this bug report on both mods.
I have produced thousands of Breeder fuel cells from used up uranium cells. After that I had to find out that no reactor accepts these fuel cells. :(
Maybe it is touching the issue that there are two breeder reactors to research and I have researched both of them.
