Study of two innovative hydrogen and electricity co-production systems based on very-high-temperature gas-cooled reactors

The coupling of the iodine-sulfur (IS) cycle and the very-high-temperature gas-cooled reactor (VHTR) is an advanced nuclear hydrogen production process. This study proposes two innovative hydrogen and electricity co-production systems based on VHTRs using the IS cycle and the helium closed Brayton cycle to produce hydrogen and to generate electricity. A thermodynamic model is established, and the influence of crucial parameters on system performance are analyzed. The optimal combination of these parameters under certain constraints is studied to maximize the hydrogen-electricity efficiency, and the thermodynamic performance of the two schemes is compared. The results show that the suggested control ranges of mass flow rate ratio for Schemes 1 and 2 are 0.031-0.75 and 0.075-0.70, and the corresponding hydrogen production rates are 17.4-295.6 and 42.2-319.6 mol/s. The net output work of the two schemes is close, and the reactor inlet temperature of Scheme 2 is usually higher than that of Scheme 1. As the hydrogen production rate increases, the hydrogen-electricity and exergy efficiencies of both schemes decrease. Scheme 2 has an advantage over Scheme 1 in overall efficiency owing to its high cycle efficiency, and the advantage is greater with an increasing hydrogen production rate.