You can't count on wafers being exactly at the same size, so you build your machinery in a way that precise sizes aren't important, only relative measures within a wafer is.
You can't count on alignment measurements, so you build your machines to use the only alignment invariant available, that is the size of a single wafer (and call it self-aligning).
You can't count on features having any specific size. They vary wildly, in proportions that in any other specialization of engineering would be disastrous. So, you just manufacture them, test after the fact, and throw away the parts that do not comply.
The entire field of IC manufacturing is about how to not need measurements and be resilient to errors.
Also, I don't know much about nuclear reactor design, but I'd be very surprised if they used measurements with several algarisms.
Have s look at an IC engine and the tolerances required for an engine to work.
Let alone say correctly designing nuclear rectors to handle two phase flow in its cooling loops.