Electricity systems are facing a major transition process from fossil based generation to renewable energy sources (RES). In the European Union target quotas for renewable energy generation have been agreed for the 2030 horizon. While there is consensus about the need for this transition, the future role of nuclear power is highly uncertain. This work explores the role of nuclear energy in an electricity system complying with elevated RES generation quotas. The impact of the long term operation (LTO) of the Spanish nuclear fleet on the electricity system costs, the revenue of nuclear operators, investment decisions in new generation capacity and the CO2 balance are also analysed. Furthermore, the benefits of the flexible operation of nuclear plants are studied.
Results indicate that the nuclear LTO drastically reduces the CO2 intensity of electricity production, but the system requires additional generation and storage capacity investments to reach high RES quotas diminishing the revenue of the nuclear generators.