Exploring iodine-sulfur and hybrid sulfur cycles for integration of hydrogen production and power generation in high temperature gas-cooled reactors and life cycle assessment

As a clean and sustainable energy carrier, hydrogen production through nuclear energy has garnered significant attention in recent years. High temperature gas-cooled reactors (HTGRs) coupled with thermochemical iodine-sulfur (I-S) and hybrid sulfur (HyS) cycles represent one of the most viable methodologies for hydrogen production from nuclear energy. In this study, an integrated system encompassing nuclear energy, power generation, and hydrogen production was developed through process simulation, utilizing experimental data from the I-S and HyS cycles to optimize the energy-matching model. The optimal energy ratios of hydrogen and electricity produced for the I-S and HyS integrated systems are 0.80 and 0.6, respectively. The life cycle assessment (LCA) results indicate that the IS and HyS hydrogen production processes contribute 3.13E-02 kg CO2 eq/kg H2 and 5.84E-02 kg CO2 /kg H2 to the global warming potential (GWP), respectively. Among the six indicators related to environmental impact-namely, GWP; acidification potential (AP); eutrophication potential (EP); ozone layer depletion potential (ODP); human toxicity potential (HTP); and photochemical ozone creation potential (POCP)-the integrated HyS cycle for hydrogen production and power generation surpasses the I-S cycle, demonstrating greater potential for development. Extending the lifetime of nuclear fuel components significantly mitigates the AP and GWP of hydrogen production systems.