Alternatives for closing the nuclear fuel cycle: Comparative analysis of the long term aspects of economy, ecology and risk with the potential for improvement through multinational solutions

The overall duration of the back end of the nuclear fuel cycle is fixed by the feasibility of final waste disposal to be achieved through a waiting period of 30 to 50 years. During this period of time the radioactive decay will reduce the radiation and specific heat release of the fission products to manageable levels. The necessary waiting period has to be bridged by interim storage, either in the form of spent fuel elements or as concentrated high level waste. The transition point between these two forms is the reprocessing step. The cooling time between unloading the spent fuel elements from the reactor and reprocessing is the decisive variable for optimization. The effect of the cooling time was investigated by studying the two boundary cases: 2 years' cooling time as a minimum, and 45 years' cooling time as the practical maximum. Evidently, deferral of the reprocessing step and general application of interim storage for the spent fuel elements offer considerable advantages, mainly a cost reduction by a factor of 5 for the back end solution and flexibility; this permits freedom of decision with respect to type, time scheduling and location of the subsequent disposal measures. The decisions regarding the principal route, strategy and political procedures for the back end of the nuclear fuel cycle must conform with the overall objective of developing nuclear energy into a desirable, unrestricted and practically unlimited option for the long term supply of electricity to cover the ever increasing demands of mankind. To facilitate the necessary transition from ineffective thermal reactor application to the fast breeder technique, spent fuel elements from the prevailing thermal reactors must eventually be reprocessed and the plutonium reserved as inventory for the startup of breeder capacity under conditions that do not result in excessive capital charges. 2 figs, 1 tab