Yes,less effective.Nope,not less,than alone.
Damage? I'm pretty sure,that almost everybody with a brain learned several reactor config for several situations and not getting any damage.Still,If they didn't,they will have less damage as well as a smaller amount of energy.That's fair.
You are simply not getting it... BOTH Points.
No double posts!
Also, a fresh Uranium cell will work for 2hrs 46min 40sec, thats about 10k seconds, in a second 20 ticks happen and for every tick the Uranium cell produces heat to nearby components and reactor hull. IF you end up cutting some of those 10k Seconds then less ticks happens which mean less heat its produced per cell, its quite possible that a certain nuclear reactor setting that regularly would just meltdown if they run for those 10k seconds, would not melt with what you are proposing, and that is DUMB.
Do you get it now? You are taking the wrong approach, next time try with the "Durr hurr Uranium cell efficiency when placed next to another uranium cell is too op please nerf!" and just maybe it would not be so dumb like what you are proposing.