Steam Reheat in Nuclear Power Plants

In this work, reheating steam from a commercial nuclear power plant 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 water vapor and liquid fluid 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. 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 calculations validate improvement in system thermal performance. Moreover, thermal radiation transport between the tube wall surface and the steam flow was evaluated for optically thick steam.

The work shows that the proposed modifications are not only feasible but also show increase of the power cycle efficiency of over 10%. Significant improvement is concluded for power output and exergy in the amount of over 50%.