Pienet modulaariset ydinreaktorit kaukolämmön tuotannossa: vaikutukset seisakkitoimintoihin

Small Modular Reactors (SMRs) present a promising pathway for decarbonising the district heating sector. However, the adaptation of conventional nuclear power plant (NPP) outage operations, such as maintenance, refuelling and in-service-inspections (ISI) remain under-explored for SMR applications. The required devices, tools, and procedures developed for large-scale NPPs are not inherently applicable to SMRs due to differences in scale, modular function, and deployment context, requiring careful evaluation of their implications for design requirements to ensure safe and cost-effective implementation. This thesis ex-amines how the design features of SMRs can impact the functional design re-quirements (FDRs) established by conventional NPPs. A comprehensive review of nuclear outage operations was conducted to establish the typical phases, operations, performance indicators and requirements that define conventional NPP outages. In addition, the general state of SMR technologies was briefly discussed from which the LDR-50 was selected for a more in-depth review. From this foundation a set of six primary FDR domains (accessibility, maintainability, inspectability, testability, radiation protection and human factors engineering) was defined. These FDRs were then used to formulate a causal analytical framework that links design attributes, functional requirements and outage performance. Based on this framework two comparative analysis matrices were created to identify and evaluate the mechanisms through which SMR design features can impact operational outcomes. The results demonstrate consistent and non-contradictory impacts across all FDR domains, indicating that the analysed design features influence outage performance through stable and predictable mechanisms. These findings suggest that the predictable nature of the impacts on outage per-formance is inherently beneficial to the modular fabrication, fleet deployment and short construction time aspects of certain SMR technologies. As such, the derived framework presents itself as a useful tool for determining the feasibility of design choices in the conceptual design of future SMR technologies.