I have made my own version of the reactor planner, which supports the
latest IC2 Experimental reactor components, and here it is for open beta testing:
(link removed, see bottom of post for new link)
Since I haven't viewed the IC2 source code (and I don't really expect to be allowed to), there's a good chance I have some things wrong related to nuances of internal sequencing of events during a reactor tick (especially regarding heat exchangers and the last reactor tick as fuel cells become depleted), but as far as I could tell, it's about right for simple cases.
Please try it out and let me know what I've got wrong, or if you have questions about it, etc.
Edit: this is now on GitHub: https://github.com/MauveCloud/Ic2ExpReactorPlanner/releases