This study presents a new design, and thermodynamic and engineering analyses of the H2SO4 decomposition section of the sulphur-iodine thermochemical cycle for producing hydrogen. Excess oxygen is used as an energy vector in various direct contact adiabatic equipment and shell and tube heat exchangers are eliminated as much as possible. Thermodynamic (energy and exergy) and cost analyses have been carried out. The results show that energetic and exergetic efficiencies are 64.2% and 64.0% respectively and typical cost is 3.3$(1990) per kmol SO2 for 4$US(1990)/GJ nuclear heat cost.