Centrifuges appear to credit processing time from when fuel rods are created until you remove the rods. I started processing in 10 centrifuges, then went on a multi-day excursion. Normally it takes about 4 to 5 seconds per percent of the processing, or about 40 to 50 seconds (real time) per 10% completion of rod processing. However, when I returned, I removed the finished rods and started the next processing cycle by adding the new uranium and starting each chamber. Then I repeated for the other 9 centrifuges. It doesn't matter if you remove the rods then add uranium or vice-versa, when I finish all 10 centirfuges (4 chambers each), I can then do the entire thing immediately again without waiting for the processing time. Starting a 3rd round does not result in the skipped waiting time. Thought you'd want to know.
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