The Japan Atomic Energy Agency (JAEA) is performing research and development on the thermochemical water-splitting iodine-sulfur (IS) process for hydrogen production with the use of heat (temperatures close to 1000 degrees C) from a nuclear reactor process plant. Such temperatures can be supplied by a High Temperature Gas-cooled Reactor (HTGR) process. JAENs activity covers the control of the process for continuous hydrogen production, processing procedures for hydrogen iodide (HI) decomposition, and a preliminary screening of corrosion resistant process materials. The present status of the R&D program is reported herein, with particular attention to flowsheet studies of the process using membranes for the HI processing. (c) 2006 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.