Ultra-small modular reactor: Economic and design analysis

Abstract

This thesis presents the pre-conceptual computational and economic analysis of a high-temperature (>1300 K), ultra-small (<10 MWe) modular reactor with a coupled high-efficiency (>50%) thermophotovoltaic (TPV) power block. Inspired by decreasing costs in TPV manufacturing, the integration of the TPV power block would allow for improved electrification efficiency over the heat cycles of traditional nuclear power plants. Further, by not requiring a pressure vessel and coolant loops, a USMR powered plant could feature significantly lower capital costs and be would be impervious to many of the major accident scenarios of typical plants. However, allowing for heat removal solely through radiative and passive convective cooling puts steep limitations on the USMR operational power densities and the selection of materials. This thesis reports on three phases of the USMR study: an initial sampling of the design space, a comprehensive economic analysis, and a focused study on improving fuel utilization. The preliminary sampling of the design space was performed using coupled thermal and neutronic analysis on a simplified model and resulted in the decision to focus on uranium carbide and uranium nitride fuels as the most promising fuel candidates. A top-down differential economic analysis, utilizing the Gen IV International Forum cost estimation guidelines and the Energy Economic Database, showed that USMR could potentially outperform larger plants in levelized cost of electricity, an extraordinary feat for a microreactor. An examination of power scaling factors and learning curves was also undertaken and suggests that there is a route for multi-unit siting to overcome loss of economies of scale for the USMR. The economic analysis highlighted fuel utilization as a major factor in USMR cost which led to a more focused exploration of the USMR design space, examining the tradeoff between maximum power density and fuel utilization while varying the moderation ratio of the core. This led to a converged design that could potentially produce electricity with a levelized cost as low as $39 per MWhr, as compared to the $93 per MWhr cost of the typical generation III+ nuclear plant.