It can be controlled by having a button on each one or having a temperature sensor connected to the reactor. To control the control rods, which will make the reaction heat up, you'll need to use 2 polysilicon with one having mode 0 and the other having mode 1. This dispense either uranium or nuclear waste, depending on the fuel rod's time in the reactor before ejection. To remove a fuel rod from the reactor, place a polysilicon set to flip-flop mode and trigger it. The reactor itself does not give off radiation even with the fuel so there's no worries in that. For maximum steam output, it must have 4 pieces of uranium inside. The reactor can be automatically refueled using microcontrollers or delay wires, some example microcontroller refuelling code can be found here.
