Why Faster is Better : On Minor Actinide Transmutation in Hard Neutron

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, ψ∗, 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.QC 2010082

RED-IMPACT : Impact of Partitioning, Transmutation and Waste Reduction Technologies on the Final Nuclear Waste Disposal

The impact of Partitioning and Transmutation (P&T) and waste reduction technologies on the nuclear waste management and particularly on the dinal disposal has been analysed within the EU-funded RED-IMPACT project. The partnership collects 23 organisations drawn from European nuclear industry, waste agencies, research centres and universities. Five representative scenarios, ranging from direct disposal of the spent fuel to fully closed cycles (including Minor Actinide (MA) recycling) with fast neutron reactors or Accelerator-Driven Systems (ADS), were chosen in the project to cover a wide range of representatice waste streams, fuel cycle facilities and process performances. High and intermediate level waste streams, have been evaluated for all of these scenatios with the aim of analysing the impact on geological disposal in different host formations such as granite, clay and salt. For each scenatio and waste stream, specific waste pachage forms have been proposed and their main characteristics identified. Both equilibrium and transition analyses have been applied to those scenatios. The performed assessments habe addressed parameters such as the total radioactive and radiotoxic inventory, discharges furing reprocessing, thermal power and radiation emissin of the waste packages, corrosion of matrices, transport of radioisotopes through the engineered and geological barriers of the resultung doses from the repository. The major conclusions of this study can be summarized as follows: [...