So the problem is caused because PlutoniumEnergy uses prefix for plutonium items. It removes many mod conflicts, but breaks some of the mod compatibilities, like this one.
So the problem is on RTG side.
Making RTG aware of that prefixed pu238 is easy enough.
No idea why you choose to prefix common items though. It only breakes mod compatibility and confuses players with several different versions of the same item similar to the dozen different copper ores Minecraft used to have.
