AbstractThe power costs of three hypothetical reactor sites are analyzed to compare the site costs of conventionally fueled fast and thermal reactors with thorium-blanketed breeders and233U fueled light-water reactors (LWR’s). Since the most critical parameter is time, three case variations are considered. The site start-up is considered coincident with the commercial introduction of the fast reactor; and alternatively, where site start-up occurs jive and ten years after the commercial introduction of the breeder. The cost comparisons also consider the effect of U3O8price increases. The value of233U produced by thorium-blanketed breeders exceeds that of the Pu produced by238U blanketed breeders. Since the power costs of the LWR's are lower than the breeders until the price of U3O8increases, early development of the breeders may be contingent upon implementation of the crossed-progeny fueling.