I am looking right at my reactor terminal in survival mode however when I press K it opens up my inventory and I cant put uranium in the reactor (I am using a small reactor on a small ship). My friend has the same problem but it works fine on a large ship.
The small reactor has only one opening which can be used to access its inventory. At first glance the side with the opening can be mistaken for a base it is supposed to stand on. Make sure you build your reactor oriented in a way that the side with the opening is accessible (or connected to a conveyor system powered by an already running generator and connected to a storage container containing uranium ingots).