Massive hydrogen production featuring high efficiency, CO2 free, and cost effectiveness is a crucial challenge for the hydrogen economy. Nuclear hydrogen production through thermochemical iodine sulfur (IS) process is a potential candidate for this purpose. Chemical reaction kinetics data are indispensable for developing a high-performance reactor as well as the scaling up of the process. The apparent kinetics of the reaction under simulated recycling conditions of IS closed cycle operation was studied by initial rate method. The effects of key parameters, including agitation speed, SO2 partial pressure, I-2 concentration, and reaction temperature, on reaction rate, were systematically investigated by measuring the variation in SO2 pressure with reaction time. Initial rate analysis method indicated that the Bunsen reaction rates were 0.23 +/- 0.01 and 0.77 +/- 0.01 order with respect to SO2 pressure and I-2 concentration. The apparent activation energy was 5.86 +/- 0.21 kJ/mol. Based on these results, an exponential rate expression of the Bunsen reaction was established. In addition, a simplified method for calculation of kinetics parameters was proposed and compared with conventional techniques. Experimental results provide theoretical basis for design and development of Bunsen reactors and for elucidating the reaction process. (C) 2017 Published by Elsevier Ltd on behalf of Hydrogen Energy Publications LLC.