Nuclear energy has been proposed as an energy source to produce hydrogen (H-2) from water. An examination of systems issues in this paper indicates that the infrastructure of H-2 consumption is now compatible with the production of H-2 by nuclear reactors. Alternative H-2 production processes were examined to define the requirements such processes would impose on the nuclear reactor. These requirements include supplying heat at a near-constant high temperature, providing a low-pressure interface with the H-2 production processes, isolating the nuclear plant from the chemical plant, and avoiding tritium contamination of the H-2 product. A reactor concept-the advanced high-temperature reactor-was developed to match these requirements for H-2 production. Published by Elsevier Science Ltd on behalf of the International Association for Hydrogen Energy.