Something happens when you place the uranium in the reactor, because without uranium that something doesn't happen PERIOD, its a nuclear reactor so working in any other way its stupid (Or at the very least it would not be a stupid nuclear reactor in the first place, and don't bother with the part that you can use other radioactive stuff [In case you actually can of course], because the only "Nuclear" material in Ic2 its uranium). Saying that uranium produce energy its slightly accurate, because without it nothing would be produced (Although when you start looking at the details its where it shows thats its actually the heat from the uranium that produces the energy).
What is that something that happens when you place a Uranium in the reactor? In minecraft its anyones guess to determine what happens inside it until al suddenly decides to make an essay explaining how the nuclear reactor (in minecraft) works in detail... In my head, the Nuclear planner its only half of whats happening in the nuclear reactor, the other half happens somewhere hidden inside the nuclear reactor working like "Magic".
And please, there are two types of magic in game logic:
There is "Ohhhh Magiiiicc" which is under the realm of Harry Potter and shit with wands and all that.
And then there is "Magic" in which something simply works and you don't have a good explanation or reason as to why its working. An example of this is the BC Quarry, out of fucking nowhere it appears a lot of cranes and drills and metal tubes and shit that drills blocks below it and then it "Magically" appears in the original quarry block you placed. See you know there is a logic to all of it, and its quite possible for it to happen, but you can really explain how it happens. (Especially the part in which all of those cranes and drills and metal tubes and shit appears from a small block)
And rick, forget anything you knew about the old nuclear reactors, since al effort was exactly to make it completely different from the old layouts of nuclear reactors so they don't all look like the same or worked remotely the same.