Hydrogen Generation

Conventional water electrolysis is a well-commercialized technology. Carbon emission from this form of hydrogen generation depends upon the source of the electricity; when nuclear energy is used those emissions are completely eliminated from the process.

High-temperature steam electrolysis is an advanced technology currently under development. This technology reverses the process in solid oxide fuel cells to produce hydrogen from steam. When coupled to a high temperature gas-cooled reactor, this process can potentially increase efficiencies by 45 to 50 percent compared to conventional electrolysis.

A number of thermo-chemical water splitting cycles have been identified in recent years. These cycles essentially split water into hydrogen and oxygen through a series of heat driven chemical reactions. Early progress, including bench scale testing, of the leading cycles best suited for the high temperature gas-cooled reactor is under development in the U.S., Japan, France and other countries. In the thermo-chemical processes, only water, heat and electricity (as a utility) are needed to produce hydrogen and oxygen. Although many of these cycles have been identified, most of the current development work is focused on the sulfur-iodine (SI) process.

Hybrid cycles combine the thermo-chemical and electrolytic reactions for water splitting. This technology offers the possibility of lower temperature process reactions and/or the possibility of using electricity as a substitute for one of the chemical reactions.

Steam methane reforming is the most economical and widespread process for hydrogen production in use today. The Steam methane reforming process requires temperatures in the range of 800º to 850ºC, which is most often provided by burning natural gas. A high temperature gas-cooled reactor could provide the energy for the Steam methane reforming process eliminating nearly 30 percent of the natural gas use in the overall process. Use of the high-temperature nuclear reactor as the heat source would eliminate carbon dioxide emissions and result in efficiencies approaching 80 percent.