Nuclear-based hydrogen production via thermochemical water decomposition using a copper-chlorine (Cu-Cl) cycle consists of a series of chemical reactions in which water is split into hydrogen and oxygen as the net result. This is accomplished through reactions involving intermediate copper and chlorine compounds, which are recycled. This cycle consists of three thermally driven reactions and one electrochemical reaction. The cycle involves five steps: (1) HCl(g) production using such equipment as a fluidized bed, (2) oxygen production, (3) copper(Cu) production, (4) drying, and (5) hydrogen production. A chemical reaction takes place in each step, except drying. In this study, the HCl(g) production step of the Cu-Cl cycle for hydrogen production as well as its operational and environmental conditions are defined, and a comprehensive thermodynamic analysis is performed, incorporating energy and exergy and considering relevant chemical reactions. The performance of the fluidized bed is evaluated through energy and exergy efficiencies, and various parametric studies on energetic and exergetic aspects with variable reaction and reference-environment temperatures are carried out. (C) 2008 The Institution of Chemical Engineers. Published by Elsevier B.V All rights reserved.