An exergy based assessment of the efficiency of nuclear fuel cycles

Abstract

As energy systems worldwide change to mitigate against climate change, the sustainability of electricity production methods is becoming increasingly relevant. Nuclear energy is constrained by the need for the efficient conversion of uranium to electricity to define itself as sustainable. The thermodynamic measure of available energy of work – exergy – is used to analyse nuclear fuel cycle processes by accounting for material and energy flows over whole conversion chains. This study proposes that a more comprehensive definition of nuclear exergy is needed to account for the additional exergy released in nuclear decay. This allows the extension of nuclear exergy analysis to the back end of the nuclear fuel cycle and novel decay heat applications. Furthermore, nuclear decay exergy is shown to add approximately 10% to previous definitions of the exergy of fissile isotopes which accounts for the additional energy released by fission products in decay. To aid future research an evaluation of this nuclear decay exergy is performed for 3000+ nuclear isotopes. The new definition of nuclear exergy is employed in investigating the sustainability of advanced nuclear fuel cycles. This analysis uses quantitative exergy efficiency metrics and Sankey diagrams to represent certain sustainability trade-offs numerically and visually.