DESIGN OF A STEAM REFORMING SYSTEM TO BE CONNECTED TO THE HTTR

摘要

Top priority objective for developing the first heat utilization system to be connected to the HTTR is to demonstrate technical feasibility of a nuclear process heat utilization system for production of hydrogen for the first time in the world. Major issues to be resolved for coupling the heat utilization system to the HTTR are l)to develop safety philosophy for reasonably and reliably ensuring safety of the nuclear reactor, 2)to develop control design concept for the total system of the nuclear reactor and heat utilization system because thermal dynamics of endothermic chemical reactor to be heated by nuclear heat is much different from the nuclear reactor, 3)to develop helium -heated components and 4)to develop enhanced hydrogen production technoligies for achieving competitiveness to a fossil-fired plant.rnA steam reforming hydrogen production system was studied as one of the first priority candidates for an HTTR-heat utilization system due to matured technology in fossil-fired plants and since technical solutions demonstrated by the coupling of the steam reforming system to the HTTR will contribute to all other hydrogen production systems.rnBasic design philosophy for the HTTR-steam reforming system is that the steam reforming plant downstream of an intermediate secondary helium loop is designed at the same safety level as fossil-fired plants and therefore the secondary helium loop was selected as a safety barrier to the HTTR nuclear reactor.rnJAERI has been conducting several studies to develop a framework of the HTTR-steam reforming system. Key design achievements were as follows.rn1) Hydrogen production performance was improved to achieve the competitiveness to the fossil-fired by applying new concepts of steam reformer and optimizing heat and material balance conditions of the system.rn2) A natural convection type of steam generator was allocated downstream the steam reformer in the secondary helium loop to achieve sufficient system controllability with accomodating the large difference in thermal dynamics as mentioned above, and to form the safety barrier by the secondary helium loop.rn3) Basic safety design criteria for fire and explosion originated at the steam reforming plant were developed.