Without Kovarex 1 ore ~ 0.0007 U235 ~ 56MJ
With Kovarex 1 ore ~ 0.1014 U238 ~ 507MJ
Kovarex increases uranium ore energy potential 9 times. And it is multiplicative with x4 reactor adjacency bonus, resulting in ~2GJ / 1 uranium ore. Let me remind you that 1 coal produces 4MJ of electrical power, liquefaction gives ~50% increase, oil isn't a big boost.
Small field of 200000 ore -> 20000 U238 -> ~29 reactor-days (almost 1 month)
Array of 10 reactors will provide 1.44GW (sky-high value for many players, as I believe) for 3 days from 1 small uranium spot.
1 drill without any upgrades mines 0.2625 uranium ore/sec. In 200 seconds (cell's lifetime) it will mine 52.5 ore -> 5.25 U238 -> 3.28125 cells.
With Mining productivity 11 and 3 Speed modules 3 it will produce exactly 10 cells, i.e. 1 boosted drill will fuel 10 reactors, providing 1.44GW energy.
Based on all these numbers, do you think that nuclear power production requires a radical nerf? And, if yes, let's discuss how it could be done.
Personally I think that there are 2 absolutely broken mechanics in the game : nuclear power and modules. And they work great together, spoiling late game : infinite nuclear power causes all this absurd productivity-speed beaconed setups, which should be justified only at the most critical points, not in furnaces.
P.S. Nuclear power itself is super-awesome, but numbers and some recipes are weird.