The Japan Atomic Energy Agency has been conducting R & D on high-temperature gas-cooled reactor (HTGR) technology and also on thermo-chemical water splitting hydrogen production technology by using an iodine-sulfur cycle (IS process) in the high temperature engineering test reactor (HTTR) project. The sulfuric acid (H2SO4) decomposer is one of the key equipments in the IS process, in which concentrated sulfuric acid is evaporated and decomposed into SO3and H2O with the heat of high temperature helium gas supplied by HTGR. A concept of the decomposer consisting of multiblock-type heat exchanger made of SiC ceramics was proposed, and its feasibility was examined by preliminary analyses of thermal-hydraulic and structural strength and test-fabrication of SiC block components as well as elementary tests of seal performance in SiC blocks and metal flanges.
