SMRSiMa: SMR Waste Management and Siting Waste characteristics and organisational aspects

Small modular nuclear reactors (SMRs) are seen as one solution for producing low carbon energy and heat. What effect SMR technologies have on waste characteristics and disposal, how the management could be organised in practice as well as societal engagement have been studied in Finland as part of the national research programme SAFER2028 National Nuclear Safety and Waste Management Research Programme 2023–2028. The focus of the work has been on SMRs based on lightwater technology.

One key element that has been studied with numerical modelling is the potential effect of the smaller reactor core size of SMRs on spent fuel characteristics. In order to do this, multi-cycle full-core 3D calculations were performed with Serpent – Ants sequence. Preliminary results with the case study (LDR lite benchmark) indicate that the axial burnup profile does not have any flat segment, in contrast to those of large PWR cores, but the impact on the integral features of spent fuel assemblies seemed to be small. However, further post-processing will be needed to, e.g., verify the impact on spent fuel reactivity for criticality safety analysis and to segregate the effect of modelling accuracy against computational issues.

Organisational models for arranging the SMR waste management in Finland are generally regulated by the Finnish Nuclear Energy Act and Directive 2011/70. The renewal of the Nuclear Energy Act is ongoing. The study discusses different models for organising and financing SMR waste management including models that are applicable and in use currently, but also alternative models that are not in line with the current Nuclear Energy Act. Alternative models are limited, e.g., by import and export bans and partly also by formulation of the waste management obligation (in the case of fuel leasing agreements). The applicability of any organisational model will also depend heavily on the sufficient expertise of the organisation and robustness of the business case.

This study also identifies potential challenges in regards to the safety oversight of organizational, management, and leadership aspects throughout the SMR lifecycle. It includes a review of existing public material, and four future scenarios based on interviews with Finnish nuclear experts. These findings were discussed with STUK and the OECD NEA Working Group on Human and Organizational Factors (WGHOF) SMRs task group.