One day, I had a dream of finding some Plutonium (It was obviously a minecraft dream). That's when I got the idea of a suggestion for Plutonium Ore. It generates in a similar way that Uranium Ore does, only that it is slightly rarer and can only ever be found below sea level. When mined, (can be mined with the same tools Uranium can be) it will drop Plutonium. This can be used to make Plutonium Cells, which are basically Uranium Cells but much more powerful. Unlike Uranium Cells, Plutonium Cells can not be re-enriched and will dissappear once used up. As they are more powerful, you will have to monitor your Nuclear Reactor more often so that it doesn't overheat. It's crafting recipe is the same as Uranium Cells, accept using Plutonium instead of Uranium.
Hope you like my idea!