A lower-temperature iodine-westinghouse-ispra sulfur process for thermochemical production of hydrogen

Thermochemical processes are the primary candidates to produce hydrogen (H ₂) using nuclear energy. In a thermochemical process, a series of chemical reactions occur in which the net result is heat plus water yields oxygen (O ₂) and H ₂. The leading thermochemical processes [Westinghouse (hybrid), sulfur-iodine, and Ispra Mark 13] require heat inputs at temperatures of ∼850°C. Each of these processes has the same chemical reaction (dissociation of sulfuric acid into H ₂O, O ₂ and SO ₂) that requires high-temperature heat but different lower-temperature chemical reactions. The high temperatures are at the upper limits of high-temperature nuclear reactor technology. The use of inorganic separations membranes is proposed to drive the dissociation reaction to completion at lower temperatures and higher pressures. If peak temperatures can be reduced by 100 to 150°C, existing reactor technology can be used to provide the necessary heat for H ₂ production. Hydrogen produced using nuclear reactors then becomes a much more viable near-term industrial option. If process pressures can be increased, there are expected to be reductions in capital cost and improvements in efficiency.