This is my design for an 8-reactor power plant with a limited fuel input of only one cell at a time, reducing wasted fuel cells. It also includes a buffer steam storage system. It works perfectly under maximum load (and is great for aesthetic addicts). This system can run indefinitely as long as Nuclear Cells are continuously fed into the loop belt. The inserters for fueling the reactors and the logistics system run on a separate solar-powered network with accumulators.
If you want the plant to be fully self-sufficient, you can place a few solar panels and accumulators in the empty space below the underground pipes where the pumps are supposted to go. This ensures the pumps never lose power under heavy load, preventing the entire base from entering a death spiral.
For the power plant to operate on its own, you need at least 8 Nuclear Cells continuously fed into the loop belt. Each inserter will take one cell and place it into its respective steel chest. Once all 8 chests contain one cell, the inserters will feed the reactors whenever the temperature drops too low.
The activation temperature is set to 800°C because the reactor experiences a brief interruption in stable power generation every 3.5 minutes if the temperature falls too low (req. of 600°C) The reactor then needs time to heat back up before it can supply at least 500°C heat to the heat exchangers to create steam.
(You can change this limit in the Decider Combinator, but I do not recommend it.)