Development of a Plant Layout and Simulation for a Power Circuit for New-Generation Nuclear Reactors

This thesis analyses the relationship between next-generation modular nuclear reactors and energy conversion systems, with particular reference to the Balance of Plant (BoP) and Brayton-cycle modelling. After outlining the energy context and the role of nuclear power in a low-carbon mix, the work develops a benchmark of the main SMR and MMR concepts, used to select three representative case studies: AMR, eVinci and OTRERA 300. The methodological approach treats the reactor as a characterised heat source, defined by thermal power, hot-side temperature, heat-transfer fluid and interface constraints. On this basis, the BoP is the object of analysis. Thermo-fluid dynamic modelling was carried out in THERMOFLEX through a reverse-engineering procedure in which pressure ratio is the key parametric variable, while working-fluid mass flow rate is determined iteratively according to source constraints. For AMR, a multi-fluid analysis was performed using air, helium, nitrogen and CO2, comparing simple and recuperated layouts. Results show a strong sensitivity to working fluid: helium gives the highest net efficiencies, air and nitrogen show intermediate and stable behaviour, whereas CO2, though less favourable in the simple cycle, shows significant potential in the recuperated one. For eVinci, modelled as an open-air Brayton cycle, net efficiency increases with pressure ratio, while the recuperator is mainly beneficial at low PR values. For OTRERA 300, modelled as a closed nitrogen Brayton cycle, internal heat recovery is advantageous across the PR range, with maximum performance in a recuperated configuration at intermediate PR. Overall, the thesis shows that BoP performance depends not only on source thermal level, but also on working fluid, cycle structure and internal heat recovery. Its main contribution lies in defining a coherent methodological framework for interpreting the relationship between reactor concept and conversion-system performance.