I didn't catch this before (since I didn't have much interest in actually using the mod), but that should be (IReactorComponent)acceptor.stack.getItem() instead of (IReactorComponent)stack.getItem(), otherwise you're altering the heat on the rod itself (which has no effect). I think you'll also want to use acceptor.x and acceptor.y in the call to alterHeat, otherwise overheating an adjacent component may cause the rod to break instead of the overheated component.
Also, it seems like you left this in the code for both Coaxium rods and Cesium rods (I hope you don't mind that I peeked with jd-gui). For all I know, maybe you want coaxium rods to heat adjacent components but not directly heat the reactor, but otherwise, you might want to strip out that whole section from the Coaxium rod class.
Hmm... I'll have to double check that, thanks! And yeah, I'm fine with the jd-gui thing