Im very skeptical it would get anywhere near that. Besides tritium I know the reactors need certain shielding that gets worn out and becomes radioactive. tritium can be made from fission plants and fusion makes radioactive elements but given everything else we have seen with technology I am doubting these are going to play off each other in a net positive way that can just be kept on going. Its in some ways a lot like wind/solar/water. The sunlight/wind/maybetidal is unlimited but the materials for the collectors are not and have to be replaced. We are really good at using up energy sources and there are like 8 billion of us.