An Assessment of Reactor Types for Thermochemical Hydrogen Production

Abstract

Nuclear energy has been proposed as a heat source for producing hydrogen from water using a sulfur-iodine thermochemical cycle. This document presents an assessment of the suitability of various reactor types for this application. The basic requirement for the reactor is the delivery of 900 C heat to a process interface heat exchanger. Ideally, the reactor heat source should not in itself present any significant design, safety, operational, or economic issues. This study found that Pressurized and Boiling Water Reactors, Organic-Cooled Reactors, and Gas-Core Reactors were unsuitable for the intended application. Although Alkali Metal-Cooled and Liquid-Core Reactors are possible candidates, they present significant development risks for the required conditions. Heavy Metal-Cooled Reactors and Molten Salt-Cooled Reactors have the potential to meet requirements, however, the cost and time required for their development may be appreciable. Gas-Cooled Reactors (GCRs) have been successfully operated in the required 900 C coolant temperature range, and do not present any obvious design, safety, operational, or economic issues. Altogether, the GCRs approach appears to be very well suited as a heat source for the intended application, and no major development work is identified. This study recommends using the Gas-Cooled Reactor as the baseline reactor concept for a sulfur-iodine cycle for hydrogen generation.4

Review of Nuclear Thermal Propulsion Systems

“…Similar to RHTP systems, temperatures and thus exhaust velocities can be enhanced by choosing a liquid fission reactor core instead of a solid one [25,55]. In such a reactor, the fissile fuel may either be a molten metal (plutonium in a molten carrier metal, e.g.…”

“…lead), a molten fissile salt (uranium fluoride in a molten carrier salt like lithium fluoride), or a solution/emulsion of the latter (uranium oxide in e.g. water) [55]. In the reference, these concepts are assumed to have advantages for use as a closed fission plant.…”

Very High Efficiency Reactor (VHER) Concepts for Electrical Power Generation and Hydrogen Production

“…For the iodinesulfur process, temperatures greater than 850°C are required (Brown, et al, 2002;Marshall, 2002).…”