Small modular reactors (SMRs) are a promising new technology due to their potential benefits to cost, ease of manufacturing, and safety. One such SMR is the NuScale Power Module (NPM), a pressurized light water reactor driven by natural convection. Previous works have shown that organic fluids like methanol and ethanol, when used in an organic regenerative transcritical cycle (ORTC), can have superior performance in mid-grade waste heat applications, such as the waste heat from the NPM, compared to more common fluids like water and CO2. A design for an ORTC secondary power cycle to be integrated with the NPM has also been presented in previous works.&nbsp;In this study, we outline the component models used to model the integrated primary and secondary power cycles. The specifics of the primary cycle model and the cost model used are proprietary. Then, we perform a global economic optimization of a model of the integrated primary and secondary power cycles using a random search, as well as differential evolution and dual annealing algorithms, and we compare the resulting design points from these algorithms. Many of the best designs identified from this optimization lie boundaries of where a hidden (not explicit) constraint is violated, making the optimization problem difficult.The results of this optimization show potential reductions in levelized cost of energy (LCOE) of nearly 20%. The viability of these optimal design points is dependent on their ability to avoid these constraints during operation, so a small region around one of the presented design points is further investigated for operational stability and sensitivity to variation in the design parameters. A pump vapor constraint is violated by many points in this small region, so a locally-valid explicit formulation of this hidden constraint is derived from the computational model. This explicit constraint can be used in further optimization, uncertainty quantification, and design analysis work to convert the optimization problem from a hidden constraint optimization to an explicitly-constrained problem, which will be essential for reducing computational load as many more integrated cycle solutions are needed and higher-fidelity component models be implemented in the future.The secondary cycle design points presented here may significantly reduce the LCOE of the NuScale SMR but warrant further techno-economic analysis and experimental validation. Future work will focus on this experimental validation of methanol as a working fluid in a transcritical Rankine cycle and uncertainty quantification and design sensitivity around the identified optimal design point.

Economic Optimization of an Integrated Regenerative Transcritical Cycle With a Small Modular Reactor

Paper Proceedings: https://asmedigitalcollection.asme.org/IMECE/IMECE2021/volume/85543

ASME 2021 International Mechanical Engineering Congress and Exposition (IMECE2021)

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