Small Modular Reactor Thermal Performance Improvement With Addition of a High Temperature Gas Reactor Superheater

Reheating steam from a Small Modular Reactor (SMR) is explored in order to increase efficiency and power output. A thermal source in the form of a High Temperature Gas Reactor (HTGR) is considered. Engineering challenges include proof-of-principle, reactor sizing, evaluation, and feasibility. The proposed thermodynamic process modifications have been evaluated for a range of inlet steam quality conditions. The evaluation of the steam tube dimensions and number of optimal tubes have been calculated utilizing the so-called Log Mean Temperature Difference method. Subsequently, the performance of the steam tubes was further analyzed within a RELAP5 model to investigate two phase boiling flow thermal phenomena. Detailed calculations include a non-uniform axial heat flux distribution based on published results for the tri-structural isotropic fuel system (TRISO). Non-uniform axial heat flux served as the non-uniform heat source boundary condition in the computer model for the High Temperature Gas Reactor. The work shows that the proposed modifications are not only feasible but also show significant improvement for power output in the amount of over 50%, and increase of the power cycle efficiency of over 14%.