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NUCLEAR HYDROGEN PRODUCTION PROGRAMME IN THE UNITED STATES
Introduction
The Nuclear Hydrogen Production Programme is focused on demonstrating the economic,
commercial-scale production of hydrogen using process heat derived from nuclear energy. The
programme collaborates with the Generation IV Nuclear Energy Systems Initiative (Gen-IV) to study
potential nuclear energy configurations and evaluate deployment scenarios to meet future needs for
increased hydrogen consumption. High operating temperatures and improved efficiencies make the
Next Generation Nuclear Plant (NGNP) ideal for producing hydrogen, particularly because of its
passive safety and high temperatures. Five major technologies that can utilise nuclear energy to make
hydrogen are low temperature electrolysis, high temperature steam electrolysis, thermochemical hybrid
cycles, pure thermochemical cycles, and steam methane reforming. The maximum environmental
benefits of low temperature electrolysis are realised when a non-emitting technology, such as nuclear
energy, is used to produce the electricity. However, there are inherent inefficiencies in producing
hydrogen using electricity alone. NHI is not investigating low temperature electrolysis applications;
however, the DOE Office of Energy Efficiency and Renewable Energy (EERE) is funding projects to
demonstrate the feasibility and economics of the technology. Steam reformation of methane currently
produces most (about 95%) of the hydrogen produced in the United States. This process is efficient but
has the environmental drawback of producing large quantities of carbon dioxide as a by-product.
In addition, valuable primary energy sources are consumed in this process thus doing little to reduce
the United States’ dependence on foreign energy sources. As a result, NHI is not investigating any
steam reforming applications associated with nuclear power.
NHI research and development (R&D) approach
The NHI programme has devoted most of its resources to developing two classes of high temperature
hydrogen production technologies: high temperature electrolysis and thermochemical water-splitting
cycles. HTE, or steam electrolysis, promises higher efficiencies than standard electrolysis, which is
employed commercially today. The new high-temperature design involves many technical challenges,
including the development of high-temperature materials and membranes. Thermochemical cycles
offer the potential for high efficiency hydrogen production at large-scale production rates, but the
technology is relatively immature. The highest priority cycles are the sulphur-based cycles
(sulphur-iodine and hybrid sulphur). R&D under NHI focuses on the development of the high
temperature water-splitting technologies that can be driven by advanced nuclear systems and on the
underlying science supporting these advanced technologies. Investigating and demonstrating these
nuclear-based systems will require advances in materials and systems technology to produce
hydrogen using thermochemical cycles and high-temperature electrolysis such as high-temperature
and corrosive resistant materials development and advanced chemical systems analysis.
High-temperature electrolysis
The HTE process is analogous to running a fuel cell in reverse. Due to the energy content already
added to the gas, electrolysis of high temperature steam requires less energy than electrolysis of water.
The process is very efficient at the high temperatures available from advanced reactors (> 750°C). All
HTE activities, led by Idaho National Laboratory (INL), are co-ordinated with other DOE research
activities on solid oxide fuel cell materials and technology development. In 2007 and 2008 INL
operated an integrated laboratory-scale experiment demonstrating the feasibility of HTE. However,
both tests were characterised by rapid degradation of electrolysis cell output. This identified that the
need to determine the causes of cell degradation and ways to improve longevity are the major
challenges facing this technology.
Sulphur-iodine cycle
The sulphur-iodine (S-I) cycle is a three-step process to thermochemically split water: i) a chemical
reaction of sulphur-dioxide, iodine and water forms hydriodic acid (HI) and sulphuric acid (H 2 SO 4 );
ii) high-temperature (450°C) process heat from an advanced nuclear reactor decomposes the HI to
release hydrogen and recover iodine; iii) high-temperature (850°C) process heat from an advanced
34 NUCLEAR PRODUCTION OF HYDROGEN – © OECD/NEA 2010