I would suggest that the Uranium Research is not a prerequisite for Kovarex enrichment.

(Maybe it's just because I decided to play with science requirements x 10, I'm going to need 300+ U235 just to do the research to unlock Kovarex...)

Yep, that's due to x10 science requirements. The default Kovarex cost is 1500; with one U235 providing 45 packs this comes down to 34 U235 (probably less, since you can and should use productivity modules at this point) - the cost balancing I did does take into account the absurdly low rate of U235 production prior to Kovarex.

Sorry, but won't fix that now.

Understood :)