Future-proof even your very first first nuclear reactor setup. Place as few as one or two reactors at first, and expand as needed.
Place the first three blueprints as a new plant, or as an in-place upgrade to the previous blueprint.
When you have 4 reactors and need to place the next set, place the tileable blueprint underneath your 4 reactors. Place this blueprint as many times as needed. Have 1 offshore pump for every 8 nuclear reactors.
The display plates help you plan ahead with placement.
Building numbers have the correct ratios and the reactors have fuel limits set so that no resources are wasted. There's also an isolated power network with a solar panel for the fuel inserters, so that the system can fuel itself up the first time or after an outage.