Demonstration Advances to Produce Hydrogen Using Molten Salt Reactor Nuclear Technology

Terrestrial Energy USA, a company that is developing a fourth-generation molten salt nuclear reactor, has joined forces with Southern Co. and several U.S. Department of Energy (DOE) national labs, in a research and development (R&D) project that seeks to pin down whether its reactor technology can produce hydrogen efficiently using nuclear heat and power. 

The two-year-long project will examine how efficiently and economically Terrestial’s Integral Molten Salt Reactor (IMSR) power plant can produce industrial-scale hydrogen. It will test a hybrid sulfur process, which is a carbon-free method of generating hydrogen from water and “may be more efficient than high-temperature steam electrolysis,” Terrestrial said in a statement on September 5. 

Essentially, the project “intends to demonstrate the commercial and industrial-scale viability of pairing the hybrid sulfur process with an IMSR power plant for large-scale production of hydrogen with zero greenhouse-gas emissions,” it noted. 

The R&D demonstration follows two decades of research at the DOE’s Savannah River National Laboratory (SRNL). Sandia National Laboratories and Idaho National Laboratory will also collaborate on the project. 

Hydrogen’s Game-Changing Potential

The use of hydrogen as an energy carrier has gained tremendous attention recently owing largely to the element’s high flexibility. Hydrogen—the most abundant and lightest of elements—is odorless and nontoxic, and it has the highest energy content of common fuels by weight, which means it can be used in a full range of applications, from power generation to transportation and industry. 

However, it is not found freely in nature and must be extracted (produced, or “reformed”) via a separate energy source (such as power, heat, or light). The bulk of hydrogen is today produced using fossil energy, mostly by steam methane reforming of natural gas. Other widespread hydrogen-producing processes include partial oxidation and autothermal reforming. 

Several experts at the World Gas Conference in Washington, D.C., this June noted hydrogen’s emerging—and potentially “game-changing”—use for storage of renewable electricity (converted via water electrolysis). In that process, hydrogen can be converted to power and power converted to hydrogen. Hydrogen could also replace fossil fuels in the chemical industry, if captured carbon is combined with the element and used as chemical feedstock. Some experts noted that hydrogen can also be used to electrify applications that currently use diesel, and where batteries aren’t a viable solution, such as to power heavy-duty transport—such as non-electrified trains or maritime transport. Others said that hydrogen could also be used for decentralized power production in a future energy system. 

As Terrestial noted on Wednesday, by 2020, the hydrogen market is expected to reach $200 billion. 

The Promise of Molten Salt Reactors 

Interest in molten salt reactor technology has also kicked up of late. Molten salt reactors under consideration for future licensing by the Office of New Reactors, an arm of the U.S. Nuclear Regulatory Commission (NRC), use either solid fuel or liquid fuel (fuel mixed with molten salt). The NRC notes that at least four molten-salt reactor designs are under development—Flibe Energy’s 600-MWth LFTR (liquid-fluoride thorium reactor), Martingale’s 557-MWth ThorCon, Transatomic Power’s 1,250-MWth TAP (Transatomic Power), and Terrestial’s 400-MWth IMSR. “The thermal spectrum liquid fuel reactors use a fluoride salt and some employ on-line removal of fission products and possibly actinides. Some have unique ways of adding fissile and fertile material,” notes an April 2018 report from Brookhaven National Laboratory’s Nuclear Science and Technology Department. 

Terrestial’s IMSR, which is a thermal-spectrum, graphite-moderated, molten-fluoride-salt reactor system, incorporates and refines many aspects of molten salt reactor operation demonstrated by Oak Ridge National Laboratory in the 1960s. According to the company, the small modular reactor “extends the applicability of nuclear energy beyond its current footprint in on-grid electric power markets,” to include chemical synthesis and desalination. The technology—which it says “can be brought to market in the 2020s”—also “promises to increase industrial competitiveness and energy security while concurrently driving deep decarbonization by displacing fossil fuel combustion across a broad industrial front.”

According to SRNL, hybrid sulfur hydrogen generation is a two-step thermo-chemical cycle based on sulfur oxidation/reduction. A key step in the reaction is electrochemical water splitting using a sulfur dioxide–depolarized electrolyzer. SRNL says the demonstration could develop a “plausible path” to producing hydrogen gas using both thermal and electrical energy (78% thermal energy and 22% electrical energy) at a cost of less than $2/kilogram of hydrogen. Molten salt reactors are the “best choice” for high turn-down electrical power generation efficiency, it says. In a June 13, 2018, presentation, SRNL noted that total funding for the project to demonstrate the hybrid sulfur hydrogen production process integrated with a molten salt reactor would be equally cost-shared. The DOE’s share is $525,000 and industry would pick up the remaining $525,000. 

SRNL noted, however, that key barriers the project will face include the levelized cost of hydrogen, system energy efficiency, and total capital investment.

For Terrestial, the demonstration with a major utility like Southern Co. will be pivotal to bring its technology to industrial markets. “Using an IMSR power plant to produce hydrogen more efficiently and economically, is just one of many industrial applications of IMSR power plants beyond electricity generation,” said Simon Irish, CEO of Terrestrial Energy USA. “Removing carbon from the production of hydrogen helps bring deep decarbonization into reach. It points the way to the production of carbon-neutral transport fuels and zero-emissions fertilizers.”

In a statement on Wednesday, Noah Meeks, Southern Company research engineer and project manager, also lauded the demonstration’s significance. “This is a potentially high-impact project that couples the benefits of molten salt reactors with the development of an advanced water-splitting process for hydrogen generation,” he said. “With its history of innovation, Southern Company is looking forward to exploring this new technology with Terrestrial Energy USA.”

—Sonal Patel is a POWER associate editor (@sonalcpatel, @POWERmagazine)