Hydrogen Production from Nuclear Energy

In this chapter, the role of hydrogen as a clean energy carrier is discussed. In the first part of the chapter, a historical perspective on hydrogen exploration, production, and use is presented. It appears that the modern world evolved from a mechanization period (when heat engines were developed to generate motive force from fossil fuels) to an electrification era (when the motive power developed by power plants is converted to electricity to supply large national or regional grids) and to a hydrogenation era (when the energy from primary sources is converted by clean processes to hydrogen as an energy carrier). It is argued that the hydrogenation era just started and will be implemented during the first century of the current millennium. Furthermore, this section reviews the main national/regional research programs deployed in the last 20 years on hydrogen research. Various uses of hydrogen including as energy carrier in transportation sector, energy storage medium, and greenhouse gas reduction agent are discussed in detail. It is shown for a case study of comprehensive life cycle analysis that among six vehicle types hydrogen and fuel cell vehicles show the greatest potential. Also, the use of ammonia as synthetic fuel produced from clean hydrogen and nitrogen represents an attractive alternative to conventional fuels for vehicles.

In this chapter the role of nuclear energy in hydrogen production at large scale is discussed. In the first part of the chapter various routes of hydrogen generation using nuclear energy are described. Five routes are identified for hydrogen generation by water splitting, among which four are based on thermal energy derived from nuclear reactor, while the fifth is based on the radiolytic effect (that is, disintegration of water molecule under the impact of nuclear radiation). The role of hydrogen as energy storage medium for load levelling of the regional electrical grid is extensively discussed. It is shown that hydrogen production when electricity demand is low, storage and its use in fuel cell for power generation when electricity demand is high, represents a very attractive method for effective generation of electricity in regional grids, which reduces the costs and decreases the environmental production when nuclear energy is the primary source. Large-scale hydrogen production is also essential for petrochemical operations and heavy (nonconventional) oil upgrading, or oil-sand extraction/processing procedures. Hydrogen option represents a potential solution for transportation sector where it can be used either directly (hydrogen is stored onboard of vehicles) or indirectly (hydrogen is converted in a synthetic fuel such as gasoline, diesel, methanol, or ammonia). All means of transportation can benefit from hydrogen as energy carrier; in this chapter the road, rail, and air transport are analyzed in detail.

In this chapter, worldwide research efforts on advanced nuclear energy systems for power, heat, and hydrogen generation are presented. It is shown that the next generation of nuclear reactors will create a new energy paradigm shift by significantly improving the fuel utilization efficiency of nuclear reactors via increased operating temperatures and a reactor’s capability to cogenerate high-temperature process heat, power, and hydrogen. In former generations of nuclear plants, the coolant temperature was typically limited to ~300 °C leaving only larger size scale-up as the option for efficiency increases and cost per kWh reductions.

Generation of hydrogen via coal gasification, natural gas reforming, and petroleum naphtha reforming is used by many countries as a transitional phase towards a fully implemented hydrogen infrastructure which will use extraction of hydrogen from water. The Generation IV International Forum (GIF) was formed as an initiative of the US Department of Energy to lead an international cooperation on development of the next generation of nuclear reactors with hydrogen production capabilities. Six reactor concepts were selected by GIF as the most promising for commercial implementation. In addition, there are two major research and development efforts worldwide on thermochemical water splitting processes: the sulfur–iodine cycle and the copper–chlorine cycle.

In this chapter, water electrolysis technology and its applications for nuclear hydrogen production are discussed. In the first part of the chapter, a general classification of water electrolysis systems is given, the fundamentals of water electrolysis are explained, and the relevant notions are introduced. Calculations of reversible potentials and over-potentials have a major importance in electrolyzers’ design and modeling. Some technological aspects of four types of electrolyzers are discussed: alkaline, proton exchange membrane, solid oxide electrolyzers with oxygen-ion and with proton conduction. Some special types of electrolyzers—hybrid electrolysis systems—are presented. The chapter ends with a discussion of possible nuclear-electrolytic hydrogen plant configurations as stand-alone systems installed at future nuclear reactor sites dedicated to large-scale hydrogen production.

This chapter presents and analyzes thermochemical cycles, which are promising methods of nuclear produced hydrogen at a large scale. The introduction presents the origins of concepts and a historical perspective on the technology development. In the first part, the most important aspects and fundamental concepts for cycle modeling and synthesis are introduced and detailed. The discussion proceeds from single-step thermochemical water-splitting processes, to two-step and multi-step processes, followed by a presentation of hybrid cycles. Relevant analysis methods are introduced in the context of each type of cycle presentation. These concepts include chemical equilibrium, chemical kinetics, reaction rate and yield, and others. Analysis of the practicality of chemical reactions is established based on their yield. A large number of reactions and thermochemical cycles are compiled, categorized, and discussed. In total, the chapter presents 122 thermochemical cycles, 25 hybrid cycles, and six special cycles (assisted with photonic or nuclear radiation).

The most important reactions, encountered in pure and hybrid cycles, are analyzed in detail. For example, both the Deacon reaction and H₂SO₄ decomposition methods are the most encountered oxygen-evolving reactions. Hydrogen iodide decomposition has a major role as a hydrogen-evolving reaction. The Bunsen reaction is also significant. In thermochemical cycle synthesis and assessment, it is important to account for the energy associated with chemical separation, chemical recycling, and material transport; this is explained and exemplified in the chapter. Another discussion involves cycle synthesis and a down selection process, a methodology that systematically leads to identification of the most promising cycles. A comparative assessment of cycles is presented and the use of exergy as a potential analysis tool is introduced. The final part of the chapter refers to three thermochemical plants which are considered as the most promising. These are plants based on the sulfur–iodine cycle, the hybrid sulfur cycle, and the hybrid copper–chlorine cycle. Some bench-scale or pilot plants exist for the sulfur–iodine and hybrid sulfur plants and they are in the course of development for the copper–chlorine cycle.

In this chapter, the hybrid copper–chlorine (Cu–Cl) cycle for hydrogen production is examined in detail. The historical perspective of this cycle development is presented in Sect. 6.1. A precursor of the cycle was proposed in 1974, which uses a non-electrochemical, non-thermochemical disproportionation of cuprous chloride; this process is based on complexation and chelating schemes that generate the desired products. Electrochemical hydrogen generation from hydrochloric acid and cuprous chloride electrolysis is one of the latest cycle developments for engineering scale-up. This process simplifies the separation steps and it has been proven by test-bench experiments. Two reactors were mainly studied for the hydrolysis reaction, which is a crucial cycle step: fluidized bed and spray reactor. Both are interesting schemes proposed for scaling up the cycle. At the University of Ontario Institute of Technology, a scaled up laboratory facility has been developed for each cycle step.

In total, seven cycle variants are examined in this chapter. The variants, including a copper electrowinning step, were studied mostly since 2003; much progress has been made in the development of the processes. Because electrowinning implies difficult separation of chemicals, it appears less feasible for large-scale implementation.

This chapter presents a detailed treatment of all relevant processes, such as electrochemical disproportionation, electrochemical chlorination, complexation, dehydration, drying, crystallization, hydrolysis, fluidized bed hydrodynamics and heat transfer, spray drying hydrodynamics and heat transfer, multiphase processes in reactors, thermochemical chlorination, thermolysis, heat recovery from molten salt, and special heat exchangers, as well as system integration of the unit operations.

Integration of the chemical plant with heat pumps and heat engines may have promising potential to substantially increase the overall hydrogen production efficiency. An interesting option is to use integrated heat pumps based on thermochemical processes such as a steam–methane reaction, or vapor compression heat pumps with CuCl as a working fluid.

Material research is also important for cycle development. Several corrosion-resistant coatings were developed—as explained in the chapter—and assessed experimentally by various methods. Various auxiliary systems are required for a full-scale plant. One item of major interest is separation of hydrochloric acid from an HCl/steam mixture exiting the hydrolysis reactor for purposes of recycling; this aspect is also detailed in a section of this chapter. Various concepts for a full-size plant and its equipment are presented, as well as simulation results with ASPEN Plus software. Other aspects are also discussed such as reliability, control, safety, environmental impact, and life cycle assessment. The overview in this chapter concludes that the Cu–Cl cycle is a promising candidate for large-scale hydrogen production with nuclear reactors.

In this chapter, various integrated systems for nuclear hydrogen production are presented. Generation IV nuclear reactors and their conceptual processes are presented. Particular attention is given to VHTR and SWCR reactors, which represent two different alternatives for future development of nuclear-based hydrogen production at a large scale. The VHTR integrated system will generate hydrogen by methods adapted to high-temperature heat requirements of over 1,100 K. The SWCR is suitable for processes at intermediate temperatures at around 800 K. Due to its higher temperature, the VHTR (and its variants) can be used with high-temperature electrolysis, as well as the sulfur–iodine and hybrid sulfur thermochemical cycle, and the copper–chlorine cycle as well. The hybrid copper–chlorine cycle is adaptable for the linkage with lower temperature nuclear reactors. Selected integrated systems for nuclear-based conversion of coal and natural gas to hydrogen are also presented. These systems are relevant during the transition period until a future hydrogen economy is implemented. A system that integrates a nuclear reactor with a copper–chlorine cycle and a desalination process is also presented. This type of integration is attractive because it produces fresh water from brackish or sea water which is then used partially as process water for hydrogen production and partially for drinking water.

Nuclear hydrogen production includes technologies with both old roots and new emerging directions: nuclear power plants and hydrogen production processes. Hydrogen production from water or hydrocarbons has been established since the early twentieth century. Also, nuclear energy for commercial electricity generation at a large scale has been established over 50 years ago. Novel technologies of hydrogen production at a large scale have emerged recently such as high-temperature electrolysis and thermochemical cycles. A new generation of nuclear reactors is being developed through the Generation IV International Forum (GIF) with advanced designs and innovations for high-temperature process heat generation and advanced fuel cycles. Both fast and thermal neutron spectra are under development. In addition, nuclear fusion to generate high-temperature heat has achieved significant progress and is viewed as a major technology of the future. In this chapter, various trends and future emerging opportunities with nuclear hydrogen production are reviewed. One of the important issues is the development of advanced fuels for thermal and fast neutron spectra. TRISO fuel particles are one of the promising developments while pebble bed reactor designs are also significant. Intermediate heat exchangers will have a crucial role for heat transfer and radioactive particle isolation from the nuclear core to downstream processes. Advanced power generation cycles including combined and supercritical cycles represent an important development for effective power and hydrogen cogeneration.