Sustainability Challenges of Small Modular Reactors in Distributed Energy Systems

Abstract Small Modular Reactors (SMRs) are emerging as a promising technological option to support both the decarbonization and decentralization of energy systems. Defined by the International Atomic Energy Agency (IAEA) as advanced reactors producing up to 300 MW(e) per module, SMRs are characterized by their reduced size, modular design, and potential for factory-based manufacturing and deployment in remote or off-grid locations. Their integration into distributed energy resource (DER) systems could help achieve climate and energy security goals, especially within the framework of Sustainable Development Goals (SDGs) and European climate policy. However, the legal and institutional frameworks governing SMRs remain fragmented, both internationally and at the European and national levels. This chapter critically assesses the extent to which existing legal regimes—covering nuclear safety, environmental protection, and energy governance—are equipped to regulate SMRs in accordance with the principles of sustainable development. It identifies key legal vulnerabilities, including definitional ambiguity, regulatory inertia, and insufficient public participation, and evaluates how emerging regulations address issues of energy justice, intergenerational equity, and environmental integrity. Drawing on a comparative analysis of European Union law and selected national frameworks (notably France, Canada, the United States, and the United Kingdom), the chapter highlights the urgent need for harmonized legal standards tailored to SMRs. It argues for the integration of democratic governance mechanisms and distributive fairness into future SMR regulation, with a view to enhancing both the legitimacy and sustainability of nuclear innovation in decentralized energy models.