You need to automate nuke production, so you need to automate nuclear fuel. The reactors produce more plutonium if they run at a higher temperature. Then you can use the rocket silo to automatically place down rockets, which will inherit the source and target coords from the silo. Then you just load the rockets up with nukes and fuel and have them fire on a timer or something. You will need to also automate rockets, so your nuke setup needs to produce enough graphene to run itself.