What mods have you tried to add? Also, check for a IDConflicts.txt file whenever trying to add mods. If that's in your Minecraft folder, you'll have to do some config editing to resolve the conflicts. Just make sure you change the ID's of the mod that's being adding, not the one that's already in. And make sure you have any needed core mods, as KingTriaxx mentioned. That's one thing that's easy to miss.
BIg Reactors, if used properly, can produce quite a bit of RF. the highest I've done messing around in a test world was about 500 RF/t, but I've heard of them getting into the thousands.
BIg Reactors, if used properly, can produce quite a bit of RF. the highest I've done messing around in a test world was about 500 RF/t, but I've heard of them getting into the thousands.