Aside from the target storage regions being underground, geologic carbon sequestration (GCS) and radioactive waste disposal (RWD) share little in common in North America. The large volume of carbon dioxide (CO{sub 2}) needed to be sequestered along with its relatively benign health effects present a sharp contrast to the limited volumes and hazardous nature of high-level radioactive waste (RW). There is well-documented capacity in North America for 100 years or more of sequestration of CO{sub 2} from coal-fired power plants. Aside from economics, the challenges of GCS include lack of fully established legal and regulatory framework for ownership of injected CO{sub 2}, the need for an expanded pipeline infrastructure, and public acceptance of the technology. As for RW, the USA had proposed the unsaturated tuffs of Yucca Mountain, Nevada, as the region's first high-level RWD site before removing it from consideration in early 2009. The Canadian RW program is currently evolving with options that range from geologic disposal to both decentralized and centralized permanent storage in surface facilities. Both the USA and Canada have established legal and regulatory frameworks for RWD. The most challenging technical issue for RWD is the need to predict repository performance on extremely long time scales …

Thermochemical processes are being developed to provide global-scale quantities of hydrogen. A variant on sulfur-based thermochemical cycles is the Hybrid Sulfur (HyS) Process, which uses a sulfur dioxide depolarized electrolyzer (SDE) to produce the hydrogen. In the HyS Process, sulfur dioxide is oxidized in the presence of water at the electrolyzer anode to produce sulfuric acid and protons. The protons are transported through a cation-exchange membrane electrolyte to the cathode and are reduced to form hydrogen. In the second stage of the process, the sulfuric acid by-product from the electrolyzer is thermally decomposed at high temperature to produce sulfur dioxide and oxygen. The two gases are separated and the sulfur dioxide recycled to the electrolyzer for oxidation. The Savannah River National Laboratory (SRNL) has been exploring a fuel-cell design concept for the SDE using an anolyte feed comprised of concentrated sulfuric acid saturated with sulfur dioxide. The advantages of this design concept include high electrochemical efficiency and small footprint compared to a parallel-plate electrolyzer design. This paper will provide a summary of recent advances in the development of the SDE for the HyS process.