There is a pratically unlimited quantity if cost is no object. But for cost to be no object, breeder reactors are needed. For burner reactors, fuel cost will begin to be seriously affected rather quickly if we try to supply a 100% nuclear world economy with only terrestrial U sources. That economy would go through in excess of 1 million tonnes of natural uranium per year to supply the current world average primary energy demand of 18 TW (about 6000 3 MW(th) reactors.) This could exhaust known terrestrial uranium resources (not proven reserves) in less than a decade.
Breeders, as I said, would greatly extend the terrestrial U resource, both by getting 100x as much energy per unit of natural uranium, and by allowing resources 100x as dilute to be economically exploited.
Breeders, as I said, would greatly extend the terrestrial U resource, both by getting 100x as much energy per unit of natural uranium, and by allowing resources 100x as dilute to be economically exploited.