Nuclear plants may be clean hydrogen source
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Nuclear power as a hydrogen source
 HYDROGEN POWER TEST – Hydrogen powers fuel cells, such as this one in Argonne's Fuel Cell Test Facility. Chemical engineer Sara Yu and engineering specialist Edward Polzin are testing this fuel-cell stack. |
"The only energy technology that can generate that much additional electricity without producing greenhouse gases is nuclear power," Walters said.
But no one expects electrolysis to do it all. "Together with steam reforming, electrolysis," he said, "is more likely a near-term hydrogen source as the market gets going. In the long term, there's greater potential for developing advanced nuclear power plants to provide the heat for centralized hydrogen production on the scale needed."
Ultimately, nuclear power could become the vital link in the energy supply chain. This vision has emerged as one element in the U.S. Department of Energy's Generation-IV Nuclear deliberations. In collaboration with 10 other nations, the Generation-IV program is developing an international consensus on research and development for the next phase of nuclear energy. Nuclear power is no longer viewed as solely a source of electricity.
"Future advanced reactors can provide heat for manufacturing hydrogen," said Argonne nuclear engineer David Wade. "Nuclear energy is the only way we know to generate large amounts of heat without burning large amounts of fossil fuel. But today's nuclear power plants don't produce enough heat."
Coolant outlet temperatures from today's reactors are about 400 degrees Celsius (750 degrees Fahrenheit). But a number of advanced reactors types with outlet temperatures as high as 900 degrees C (1,650 degrees F) are being developed for deployment in 20 or 30 years.
One technology that the Generation IV program recommends for further development is the liquid-metal-cooled fast reactor. These reactors can not only provide heat for steam reforming of methane, but they also can create new nuclear fuel by converting the non-fissile portion of natural uranium into fissile plutonium.
"If nuclear power is to provide the bulk of energy to manufacture hydrogen on a global scale," Wade said, "we'll need to create new fuel, because existing natural supplies will be exhausted in 50 years."
Sodium-cooled fast reactors, he said, can produce peak outlet temperatures of about 600 degrees C (1,100 degrees F), hot enough for steam reforming. Operating experience with them has been excellent. Argonne operated Experimental Breeder Reactor II safely and reliably for 30 years at Argonne-West in Idaho.
The Russian nuclear program, he said, is developing a lead-cooled fast reactor that could provide temperatures of 850 to 900 degrees C (1,560 to 1,650 degrees F), hot enough to support a third hydrogen-manufacturing technology, the thermochemical cracking of water.
Cracking water for hydrogen
Thermochemical cracking is being developed around the world, Wade said. Typically, this process uses temperatures of 700 to 900 degrees C (1,290 to 1,650 degrees F) in combination with chemical reagents to break water into hydrogen and oxygen. The chemicals are recycled. The only input is water, and the only outputs are hydrogen and oxygen.
Gas-cooled, high-temperature reactors that operate at about 900 degrees C (1,650 degrees F) are a likely heat source for thermochemical water splitting for hydrogen. A few are currently operating in Great Britain and France, but they are being phased out because they are not economically competitive. A second class of gas-cooled reactors was developed in the United States and Germany. South Africa expects to have a commercial prototype ready for the market within a decade, and Japan is planning a pilot-scale demonstration with a high temperature helium-cooled nuclear reactor as the heat source.
Thermochemical processes have not yet been commercialized, Wade said, mainly because steam reforming is more economical and can supply the existing market. But recent concerns about the environment and energy independence have revived interest in greenhouse-gas-free processes.
"Transition to a hydrogen economy created by nuclear power could take three or more decades", Wade said. "But, it could provide a clean, abundant and affordable fuel supply for transportation and homes and industry."
For more information, please contact Catherine Foster (630/252-5580 or media@anl.gov) at Argonne.
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