Depending on what nuke design you're using, the tree farm may be significantly cheaper, and won't cost you uranium to run. Plus, once you get it all set up and automated with a fully heated boiler, you have 144 MJ/t, constantly, with zero maintenance. (well, some of it might be needed to convert the logs into planks/charcoal, but most of it is available to you. Which, with AE's current rate of exchange, could power a network using up to 720 energy units.