Other opinions
Since uranium is ubiquitous and plentiful in the earth's crust, its availability is determined almost entirely by the willingness to find it. Thus, while today's low uranium cost equates to about 50 years of assured resources (3.1 Mt) using conventional reactors at the current usage rate, a doubling of the market price increases this time roughly ten-fold. In all, conventional estimated resources account for about 250 years' supply (16.2 Mt) at the current consumption rate. This does not include advanced uranium-extraction scenarios (phosphate deposits accounting for 22 Mt, seawater accounting for up to 4000 Mt) that require 10-15 times the current market price.
The Canadian Nuclear FAQ
Lots of other interesting info at this site, too.