SMRSiMa: SMR Waste Management and Siting: Summary Report

There are multiple SMR-related projects ongoing in Finland. Cities such as Helsinki, Kerava and Kuopio are looking into options for decarbonising heat production with the use of district heating reactors. With the emergence of SMRs, new actors have entered the Finnish nuclear sector including municipalities and their energy companies, industries looking for deploy SMRs and domestic and international SMR vendors. These developments also raise multiple new questions, such as: Can SMRs be sited close to urban areas safely? How do they differ from conventional nuclear power plants? Do the new actors have the necessary competences to deploy and operate the SMRs? Does the nuclear waste management differ from the current reactors? The objective of the SMR siting and waste management (SMRSiMa) project was to answer some of these questions, and to assess how prepared Finland is for SMR deployment.

SMRSiMa was a joint project between VTT, LUT and GTK. The focus areas of the project were SMR: 1) spent nuclear fuel (SNF) characterisation, 2) waste management, 3) geological siting considerations, 4) stakeholder engagement and 5) organisational aspects. The work focused mainly on light-water-reactor SMRs. The objective of this report was to summarise the work carried out in the focus areas between 2022–2026 in the KYT2022 and SAFER2028 projects. By bringing together results previously published across multiple research reports and articles, this report provides a consolidated view of the key project findings.

Modelling with Serpent and the coupled Serpent–Ants sequence indicated that discharge burnup and fuel enrichment are the dominant factors influencing LWR SMR spent nuclear fuel (SNF). For most LWR SMR designs these parameters are comparable to conventional nuclear power plants, resulting in broadly similar SNF characteristics. The smaller SMR core size can increase neutron leakage and more variation in axial burnups. From a nuclear waste management perspective, this indicates that when burnup and enrichment are close to current reactors, existing disposal methods remain applicable. However, deviations in these parameters alter radionuclide inventories, decay heat and post irradiation reactivity, which may influence engineered barrier requirements and repository footprint. In such cases, quantitative analyses are required to determine the implications for disposal system design.

It is possible that multiple reactors will be operated in multiple locations by different organisations. Furthermore, the current license holders cannot be forced to incorporate new nuclear waste generated by these new operators. Thus, new license holders must plan how they want their nuclear waste to be managed; will it be carried out in a new central location or locally at the SMR sites? New license holders and operators also need to build nuclear organisations and safety culture from scratch and ensure that they have the competencies to operate SMRs safely.

Geological investigations remain essential for ensuring the safety of SMR reactor sites and their corresponding waste disposal facilities and are already embedded in current Finnish siting practices. As the SMR industry matures, these investigations can be tailored to assess the suitability of specific host rock conditions. New geological site‑characterisation methods offer more efficient approaches that can still meet safety requirements. Deep borehole disposal carries the greatest uncertainties and requires further R&D but could offer an option for disposal of smaller nuclear waste inventories for the new operators.

Societal and stakeholder aspects were also examined to understand public attitudes, stakeholder expectations, and the social conditions influencing SMR siting and waste management. Surveys in major cities and interviews with local stakeholders revealed mixed views toward SMRs, with clear differences across demographic groups and strong emphasis on transparency and the responsibilities of potential host municipalities. The work highlighted the importance of early, continuous and well-structured engagement processes, as well as the need to communicate risks, benefits and waste management obligations clearly.

Finally, the Nuclear Energy Act was under renewal during the writing of this report. The draft legislation introduces a more flexible and risk based licensing framework, intended to also accommodate SMRs while maintaining high safety standards. Key changes include potential streamlining of early phase licensing steps, and updated requirements for site evaluation, waste management planning and stakeholder engagement. The renewal also outlines new possibilities, such as re-use nuclear waste and processing of waste abroad under specific conditions enabling closed SMR fuel cycles in the future. While the final content of the Act may still evolve, the proposed framework is expected to support more efficient SMR deployment while ensuring robust oversight throughout the entire lifecycle of the facility.