[en] Since the start of the nuclear power era studies have been performed of how to utilise the uranium energy resource in the most effective way. Only about one percent of the energy potential of uranium is utilised in the light water reactors of today. To improve the utilization other types of reactors are needed. With fast reactors theoretically 50-100 times more energy can be extracted from the uranium. This will require reprocessing of the uranium and multiple recycling of the plutonium. Plutonium and uranium can also be recycled in light water reactors, but this will only improve the uranium utilisation by about 20 %. Recycling of plutonium on a routine basis is presently only done in France. The development of fast reactors has been going on since the end of the 1940ies. During the 1970ies the planning was that a large number of fast reactors and their associated fuel cycle facilities would be in operation by the year 2000. The development has, however, for different reasons been much slower than planned. The general assessment today is that fast reactor, if they will be realised, will hardly give an important contribution to energy production until after 2050. Nuclear power production has instead been dominated by light water reactors similar to the ones in use in Sweden. Light water reactors are believed to continue to dominate during the next decades. To start a fast reactor system plutonium (or highly enriched uranium) will be needed. Such plutonium is contained in spent nuclear fuel from light water reactors. This raises the question: Should the spent nuclear fuel be stored so that the potential energy resource in the fuel can be used in the future instead of disposing of it as a waste? The answer to this question will depend on when the material will be useful, i.e. when fast reactors have been introduced on a large scale. It will also depend on the demand for plutonium at this time, i.e. will plutonium be a scarce redundant resource at this point of time. In this context it should be considered that fast reactors will generate their own plutonium, as breeder reactors. Plutonium from other reactors will thus only be needed for the first years of operation. To provide a basis for the answer to the question if the Swedish spent fuel is a resource or a waste this report provides an overview of the present development status for fast reactors and their potential for large scale commercial use. It further describes the impact on the Swedish system for management of spent nuclear fuel if the fuel were to be reprocessed and the uranium and plutonium reused as fuel for fast reactors or for the present reactors