Influence of HTR Core Inlet and Outlet Temperatures on Hydrogen Generation Efficiency Using the Sulfur-Iodine Water-Splitting Cycle

The performance of hydrogen production via thermochemical cycles is typically evaluated using thermal efficiency. In this study, the sulfur-iodine cycle with heat supplied by a high-temperature reactor (HTR) is analyzed. Two cases are examined: one flow sheet designed by General Atomics in the United States, the other by Commissariat à l'énergie atomique et aux énergies alternatives in France. In each case, HTR helium inlet and outlet temperatures are specified. Differences in these temperature specifications lead to process variations between the flow sheets and in how the hydrogen processes interface with the nuclear heat source. Two principal conclusions result from the analysis. First, the thermal efficiency tends to plateau above a certain outlet helium temperature. This is a characteristic effect of the method of Öztürk et al. for sulfuric acid decomposition. Second, it is clear that it is impractical to discuss efficiencies for the hydrogen process that are independent of defined operating parameters of the HTR.