And did you really state that taking uranium out of granite is economical? The granite you want to mine is worth more than the uranium in it, not to mention that it would take more energy to mine it than you would get from it. There are only 3-10 part per million of uranium in granite.
Have you read this?:
http://nuclearinfo.net/Nuclearpower/UraniuamDistribution
The Rossing mine in Nambia mines Uranium at an Ore concentration of 300 ppm at an energy cost 500 times less than the energy it delivers with current thermal-spectrum reactors. If the energy cost increases in inverse proportion to the Ore concentration, shales and phosphates, with a Uranium abundance of 10 - 20 ppm, could be mined with an energy gain of 16 - 32.
Extrapolating from that, the energy gain is 1.6 for every ppm of uranium. As you say, granite contains 3-10 ppm of uranium. Therefore, mining granite for its uranium would provide an energy gain of 4.8 to 16. That would be without improving current reactor thermal-efficiency at all, and without improving current reactor breeding efficiency at all (all fission-reactors fueled with a mixture of U235 and U238 breed to some extent).
Running a uranium economy off of such a low-grade ore would, of course, in the real world provide incentive to improve fuel-efficiency (thermal; breeding-ratio; etc.) of reactors (even thermal-spectrum reactors can have their breeding-efficiencies improved). Thus, in the real world, the energy gain from mining granite for uranium would likely be higher than 4.8 to 16.
It's your link. I was quoting you and commenting on it.