A practical compact nuclear power plant for regular Factorio run that is built small at first and expanded along with energy requirements of the factory.
Images: https://imgur.com/a/WWnTB
Discussion: https://redd.it/6iphc3
Blueprint Browser: http://fbpviewer.trakos.pl/b/1nEPY4nl7cW70VD5JD-HZSx68OU
Since the addition of the second reactor gives the highest boost (40 MW -> 160 MW - 400% increase), the starting setup should have at least 2 reactors.
When you feel that it's the time to expand your station, add another couple of reactors. Adding even numbers of reactors gives most efficient results And add Turbine Expansion Segment on both ends of the power plant.
Each pair of reactors requires 2 turbine expansion segments to be added. Make sure to expand the heat pipe line along with your reactor if it wasn't 5 tiles thick from the beginning.
You can expand it up to 10 reactors to get 1.4 GW. This amount of power will satisfy player's needs in most cases. Further expansion is limited by design in exchange for being compact, modular and good-looking.
Once you research the Kovarex enrichment process, you can add a Service Bay that will make your plant self-sustainable in terms of Uranium-235.
To feed the station it will require Uranium-238 and Iron Plates shipments in 16-10 ratio.