Why Faster is Better On Minor Actinide Transmutation in Hard Neutron

Sammanfattning: In this thesis, options for efficient transmutation of transuranium elements are discussed. The focus is on plutonium, americium and curium mainly because of their long-term contribution to the radiotoxicity of spent nuclear fuel. Two innovative helium-cooled core designs are proposed, dedicated to the transmutation of actinides. The performance of the more promising of the two is studied in realistic transient fuel cycle scenarios. During the 1150 day irradiation cycle, a minor actinide consumption of 355 kg/GWth·year is achieved. An analysis of the efficiency of spallation neutron sources in helium-cooled cores is also performed. It is shown that the proton source efficiency, ??, is improved by about 10% when helium is used as coolant, rather than lead-bismuth eutectic. Further, a proposal is made to transmute actinides in the upper part of a BWR core. A net consumption of transuranics is shown possible in the BWR park already when 50% of the BWR fuel is of the proposed evolutionary type.The thesis concludes that efficient transmutation of transuranic elements in dedicated helium-cooled subcritical cores is possible. But, in many instances fuel cycles without dedicated cores may lead to comparable final states. Especially, the evolutionary BWRfuel proposed seems interesting.