Integrating nuclear Small Modular Reactors into low-carbon energy systems: an illustration using a recent European R&D initiative

The race to develop Small Modular Reactors (SMRs) is in full swing around the world. SMRs are nuclear reactors with a power output of a few hundred MWe incorporating high modularisation and standardisation by design, thus facilitating economies of in-series production. SMR technologies have the potential to strongly contribute to decarbonisation of the energy sector but are yet to be deployed. Considered at a local or regional scale, SMRs can be fully integrated in innovative hybrid energy systems (HES), including variable renewables and nuclear energy in the form of electricity, heat or hydrogen, energy storage systems, heat networks, and power grids. These systems must operate flexibly to ensure the stability of energy networks. These integrated energy systems are currently under development, however, in Europe, studies on such systems remain limited. In this context, a European Industrial Alliance on Small Modular Reactors, launched by the European Commission in 2024, pointed out significant R&D gaps to be tackled to make these energy systems ready for deployment. Therefore, TANDEM, a Euratom-funded project was carried out between 2022 and 2025 to help fill these gaps. The project has delivered methodologies and tools for the assessment of HES and validated and demonstrated them on case studies for decarbonisation. The project enabled first evaluation considerations of the technical performance and economic viability of such systems. It then covered nuclear safety aspects and environmental impact. Finally, it investigated citizen engagement and Education & Training needs to prepare the workforce required for developing and deploying these energy systems.