Of critical concern for the future of nuclear-fission power are the magnitude of the supplies of uranium and the state of technological devel­opment toward the achievement of breeder reactors. The reactors now in operation and under construction, or on order, are almost exclusively light-water reactors having so small a conversion factor that they are es­sentially burners, consuming only about 1 per cent of whole uranium.

Rafford L. Faulkner (1968), director of the Division of Raw Ma­terials, aec, has estimated that by 1980 the requirements for nuclear fuel in the United States (allowing for an 8-year advance supply) would amount to 650,000 tons of U3Os. Against this figure, his maximum esti­mate of reserves was 660,000 tons. His requirements estimate, however, was based on an earlier estimate of a 1980 power capacity of 95,000 megawatts, instead of the revised higher estimate of 145,000. The corre­sponding estimate of uranium supplies for the world outside the Commu­nist bloc was 1,575,000 tons of U308. Most of this will doubtless be re­quired by the nuclear power developments outside the United States.

From such data, it appears that with the types of reactors already in operation, or being built, or on order, an acute shortage of uranium sup­plies is likely to occur within the next 25 years.

Offsetting this is the breeder reactor program. Initially, this was pur­sued at a leisurely pace, but within the last 5 years a sense of alarm has arisen so that now something approaching a crash program is under way. Even so, the earliest prototype large-scale breeders are not expected to go into operation until about 1985.

It appears, therefore, that nuclear power from the fission reaction, were it to continue to be based principally on 2S5U, would be relatively short-lived—probably less than a century. However, if a transition to breeder reactors can be made before it is too late, the supplies of uranium and of thorium in rocks having contents of 50 grams or more per metric ton are of a magnitude hundreds of times larger than the total supply of

fossil fuels. Hence, with breeder reactors, there is promise of an adequate industrial energy supply for a much longer period than would be the case for other exhaustible energy sources.