Today, an annual world production of hydrogen is about 52.6 million tons, and almost all of it (96%) comes from processing of fossil fuels – natural gas, oil or coal which leads to significant CO₂ emissions – from 11 to 20 kg for every kilogram of H₂. Most of the hydrogen is used in the chemical industry and production of fertilizers, but transition to a low-carbon economy requires new technologies for industrial-scale hydrogen production, without a carbon footprint.
There are several methods for hydrogen production. The simplest is alkaline electrolysis, when water is decomposed into oxygen and hydrogen affected by an electric current. This technology is well developed but requires a lot of energy and very ineffective. High-temperature steam electrolysis is more promising: part of the energy is supplied in the form of heat, which reduces electricity consumption by almost a third and increases overall efficiency. Another option is the thermochemical sulfur-iodine cycle when water is decomposed into elements in a chain of reactions at very high temperatures. This method is potentially effective but requires complex equipment and work with aggressive reagents.
The researchers from the University of Pisa have studied the possibility of using nuclear power plants for hydrogen production, in particular, new-generation reactors capable of operating at temperatures up to 1,000 °C. Having analyzed various technologies, they came to the conclusion that high-temperature steam electrolysis has the greatest potential: it provides high efficiency (up to 43%) and completely eliminates harmful emissions. The key element of the system is an intermediate heat exchanger that safely transfers heat from the reactor to the hydrogen production plant, isolating them from each other.
An economic analysis using the IAEA HEEP program showed that the cost of hydrogen when using nuclear technologies can range from $2.71 to $3.57 per kilogram, which is comparable, and, in some cases, even more profitable, compared to the other low-carbon methods. So, hydrogen production using solar and wind-powered electrolysis costs about 6.61 Euros per kilogram. At the same time, nuclear power plants provide stable operation with a capacity utilization factor of over 90%, which significantly distinguishes them from variable renewable energy sources. From an environmental point of view, such schemes are not inferior to “green” hydrogen: CO₂ emissions are only 0.3–0.8 kg per kilogram. Finally, nuclear energy is not weather-dependent but is capable of producing large volumes around the clock. Scientists offer to focus efforts on bringing high-temperature steam electrolysis to an industrial level, as well as developing the concept of “hydrogen islands” — the specialized sites where nuclear reactors will operate exclusively for production of H₂.
