Looks like 2 “packets” of 15 RU/t, but you need 1+ “packet” of 16 RU/t to run the Centrifuge.
I would recommend using Steel Stuff instead of Bronze for this particular Task. Material and Tier are not really the same thing in GT6, you can mix and match them as long as the ranges in the Tooltips are overlapping/touching.
Now that I look at it, maybe you just need better Boilers and Burning Boxes, there is a conversion loss between Steam and the Turbines of 1/3rd, and it might be rounding away one Energy Unit per Tick somewhere.
Aaaaand now I remember, your Boilers might have calcified because you do not use Distilled Water, right? That will cause Energy Loss at the Heat->Steam Conversion, knocking off the balance of your otherwise obviously correctly calculated Setup.