Modelling Nuclear Hybrid Energy Systems: Objectives, architecture, and applications of the TANDEM Modelica library

In the context of the energy transition, tighter integration of energy production and consumption through multiple energy vectors represents a promising pathway to improve resource utilisation and efficiency. Nuclear Hybrid Energy Systems (NHES), where nuclear reactors are coupled to different end-user segments, are seen as a valuable response. This article presents an overview of the TANDEM Modelica library, an open-source modelling tool developed under the Euratom-funded TANDEM project to support the simulation and analysis of NHES. It is based on the object-oriented language Modelica, which allows assembling NHES simulators from independently developed models through a plug-and-play approach. In this work, we present the objectives and anticipated requirements of the tool, while practical applications showcase the library’s capability to simulate complex dynamics under various operating scenarios. It also outlines the methodological approach to numerically couple dynamic models with external tools (i.e., thermal-hydraulic codes for safety analyses and techno-economic optimisation frameworks). The library proved to be a valuable tool within the broader framework of NHES analysis, which aims at supporting decision-makers evaluating the deployment of such systems in decarbonisation strategies. Future developments aim at expanding the library’s contents in terms of available technologies and assessing model fidelity through verification and validation efforts.