This is what I meant. If you wanted to make a setup that does not require any player intervention, simply feed ore to the bottom and do what you will with the result. This will only put out u235 once the belt fills, it takes time, but its maintenance free so long as the ore supply continues.
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You can prime kovarex build using the new splitter priority units. Setup correctly, the u235 can recirculate the kovarex centrifuges until the belts are full, then the splitter priority will yield the excess, never starving the system.