Current R&D on the thermochemical water splitting iodine-sulfur (IS) process in Japan Atomic Energy Agency (JAEA) is summarized. Reactors were fabricated with industrial materials and verified by test operations: a Bunsen reactor, a H2SO4 decomposer, and a HI decomposer. Component materials of the reactors were stable in the operation environment. Small amount of H2SO4 in the anolyte solution in an electro-electrodialysis (EED) cell had no negative impact on cell performance parameters. Relationship between cell solution composition and temperature and cell parameters was formulated by experimental data. Demonstration of the test facility with process design of 100 L/h hydrogen production is performed to verify integrity of process components and stability of hydrogen production. Tests of sections were first conducted individually to show material processing rates were controllable. Based on the result, an 8-h continuous operation of the total IS process was performed in February 2016 with H-2 production rate of 10 L/h. Demonstrations are planned for longer operation period and higher H2 production rate after improvement of components to prevent troubles. (C) 2017 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.