How long can uranium last?

If US were to replace fossil fuels with nuclear power we would require somewhere between 500 GW of reactor power. However this only looks at the problem from the viewpoint which treats annual demand as continuous, where as it fluxuates almosrt continuously.  The 500 GW is only useful in determining how much reactor fuel the US would require if it were to obtain a years supply of electricity solely from nuclear power.  

Let us assume that future nuclear reactors will burn nuclear fuel efficiently.   Nuclear fuel includes Fissionable U-233, U-235, and Pu-239 as well as Fissile Th-232 and U-238.  Efficient reactors breed Th-232 and U-238.  Efficient reactors can produce 1 GW of electricity for a year from one ton of Th-232 or U-239.   That means that all of the electricity currently consumed in the United States, could be produced by 500 tons of nuclear fuel.  In addition if transportation and Industry relied directly on nuclear power , or indirectly through electricity, as little as another 500 tons of fuel could produce 80% of the American economy.

International shipping could be conducted by nuclear powered ships, while within the United States, freight could be carried by electrical intercity rail.  High speed electrical passanger trains could replace local air travel.  Molten salt reactors can produce up to 1200 C heat for industrial use, while MSRs could aqlso be used to produce Hydrogen, if more heat is required.

So the annual expendature of 1000 tones of would bring the United States into the post-carbon age.  

How much nuclear fuel do we have?   In January 1968 the USAEC extimated that the United States possessed a $500 a pound Uranium reserve, of 4.7 billion tons of Uranium at the 1968 price of $500 a pound.  $500 a pound translates into $3000 a pound.  This seems like quite a lot, but $3000 might get you 4 GWh of electricity from a molten salt breeder reactor.  That is not expensive, and would have far fewer environmental consequences than any form of renewable energy.  

Thus from Uranium alone, the United States would be able to power its economy for 4.7 mmillion years.  There is no reason to think that the rest of the world is less well endowed with Uranium than the United States.  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.