Excellent summary by Charles Barton of this question at “The Nuclear Green Revolution”
… Thus global Uranium land resources will be sufficient to supply the human population of the world for a few million years.
In addition, the sea contains a huge amount of disolved uranium. This is a sustainable resource because every year 32,000 tons of uranium flows into the sea. The Japanese have developed a uranium recovery from seawater technology, that is estimated to produce uranium at the cost of $100 a pound. Thus by adding to energy efficiency at a faster rate than the growth of energy demands, we can supply all human energy needs with the sustainable 32,000 for a very long period of time. We human beings are not as sustainable as uranium.
So far I have not mentioned thorium, which is in some respects an even better nuclear fuel than uranium. Geologists tell us that there is somewhere between three to four times as much thorium as uranium in the earth’s crust. We know a lot less about how much thorium can be recovered compared to uranium. Think in terms of several millions of years.
Humanity thus can look forward to a future of nuclear power that would reach out for millions of years of nuclear power. That power would assure everyone a high energy lifestyle.
More, rather than less, energy, can be in our future.