The project first studied the energy market and its projections, as well as the European energy policies. It led to define the generic configurations of two Hybrid Energy Systems (HESs) to be studied by the project. The first confguration is related to a district heating network and power supply for a large urban area. The second one is an energy hub in an industrial perspective; the HES for the energy hub is inspired from a harbour-like infrastructure.
The project has developed a TANDEM open-source modelica-based library gathering the models of the HES components. The TANDEM library has been made publicly available in a git repository (
https://gitlab.pam-retd.fr/tandem/tandem/(s’ouvre dans une nouvelle fenêtre)) under the 3-clause BSD-license slightly modified. The documentation containing the Modelica model description has also been released by the project. Based on this library, simulators of the two hybrid energy systems configured in TANDEM have been developed by coupling different Modelica models of components to simulate the dynamic physical behaviour of the systems.
In parallel, the project also developped the modelling of the SMR use-case in TANDEM with system thermal-hydraulics codes, ATHLET and CATHARE. The use-case relies on an academic concept, called E-SMR, developed by the ELSMOR Euratom project. A coupling between the ATHLET and CATHARE modelling with some component models of the modelica-based library was set also up.
The extension of the deterministic safety analysis to take into account the hybridization impact on SMR safety consists in identifying the event initiators specific to the hybridization combining the SMR reactor and its balance of plant. Several transients, related to Design Basic Conditions (DBC), have been identified as relevant for analysing the impact of hybridization on nuclear reactor behaviour. The detailed analysis of the hybridization transients, directly linked to a variation of the electricity or heat loads, simulated with the ATHLET-based and CATHARE3-based coupling, was carried out during the project. It was concluded that the hybridization was not expected to adversely affect the severity of the DBC-1 to 3 transients simulated in the framework of the TANDEM project.
The two generic HESs configured by the project were derived in three study cases defined in local European energy contexts, in Finland and Czech Republic for the first configuration, and in France for the second one corresponding to a virtual harbour. The Backbone and PERSEE tools in stand-alone were implemeted in these three study cases in order to carry out a constraint-based optimization process, considering the minimization of CO2 emissions and total costs, to size the various HES components. The analysis of these three study cases shows that SMRs can be a relevant option to decarbonize HESs. However, it is important to be aware that the results obtained for the study cases deeply rely on the assumptions taken into account in the optimization calculations, and are likely to be affected by the assumptions and uncertainties associated with the optimization input parameters. To complement this techno-economics study, sensitivity and impact analyses of the optimization results to the assumptions and uncertainties - related to economical and technological parameters, and methodology – have been carried out.
Regarding citizen engagement, four citizen events supported by the TANDEM project were organized between 2024 and 2025 in collaboration with context-specific organizations, in FInland, Czech Republic and Belgium. The analysis of the event process and results allowed to provide practical insights and findings to industry and public organizations. Citizen engagement is a strategic and long-term effort.
Regarding Education & Training (E&T), strategic recommendations were build upon the findings of the TANDEM project’s E&T gap analysis in the domain of the design and safety of SMRs and HESs. They aim to ensure the timely readiness of a qualified SMR workforce.
All the work results carried out in TANDEM resulted in technical, economic and societal recommendations and policy briefs on the integration of SMRs within hybrid energy systems for industry, R&D teams, TSOs, regulators, NGOs and policy makers.
