Amongst various thermochemical water splitting processes the Sulfur- Iodine hydrogen production process (SI cycle) is currently the leading candidate. The current flow sheet for this cycle is very complex and from analysis point implementation of the flowsheet to another code is almost impossible without simplifications to the flow sheet. In this work the simplified modeling of the SI cycle, the main chemical reactions are modeled with an appropriate simplification. A simulation methodology is presented to interface the heat transfer from nuclear reactor heat exchanger to the chemical reactions accounting the sensible heat, evaporation process and heat of reactions.