Modelling the Swiss Nuclear Fuel Cycle at Hourly Resolution

This report documents the technical continuation of P. Tessier's semester project [1] on the integration of fast neutron reactors (FNR) and nuclear fusion into the Swiss 2050 energy mix, modelled with the EnergyScope optimisation framework [2]. Two extensions are presented. First, the underlying model is ported from EnergyScope's monthly-resolution formulation to the hourly, typical-days (TD) formulation of EnergyScope TD, addressing a limitation explicitly identified at the end of the original project. The transition requires re-expressing all nuclear capacity-factor profiles at hourly granularity, introducing explicit baseload constraints for each reactor technology, and translating the renewable-generation bounds and the operational GWP ceiling (4,200 ktCO2-eq/y, sourced from the Swiss Federal Perspectives Énergétiques 2050) into the same hourly summation form. Second, the nuclear fuel-cycle representation is extended beyond a single lumped waste stream: interim storage, reprocessing (with recovery of uranium, plutonium and vitrified high-activity waste), MOX fabrication and long-term geological disposal are introduced as distinct technologies, each parametrised and sourced from institutional references (swissnuclear/Nagra, ZWILAG, Orano, the World Nuclear Association, and the INL Advanced Fuel Cycle Cost Basis). A unit ambiguity in Tessier's model-the conflation of an energy ratio (2.7027 GWh th /GWh elec) with a mass in kg/GWh elec-is identified and corrected, yielding a revised spent-fuel output coefficient of 3.3858 kg/GWh elec that anchors the downstream mass balance. Together, these extensions track Switzerland's projected spentfuel stock-2,960,000 kg of heavy metal, corresponding to lifetime reactor production minus material already reprocessed abroad-through to its possible end states, whether direct geological disposal or reprocessing and partial reuse as FNR fuel. This report is intended as a technical and methodological reference: it documents what was modelled, how, and on what basis, rather than presenting a scenario analysis, which is left as a natural next step for future work.