On January 24, the nuclear energy company Terrestrial Energy USA informed the United States Nuclear Regulatory Commission of its plans “to license a small modular, advanced nuclear reactor in the United States.” Many steps later – sometime in the 2020s – the American subsidiary of the privately held Canadian company Terrestrial Energy, Inc., hopes to bring its IMSR technology to market. IMSR is the acronym for integral molten salt reactor. The IMSR stands apart from conventional nuclear technology on several dimensions. On the dimension of operating temperature, the IMSR is hot enough that it can be beneficially integrated with high-temperature industrial processes. According to the company’s research, ammonia production could be a candidate for such integration.
Molten salt reactor (MSR) technology has its roots in work performed at Oak Ridge National Laboratory in the U.S. in the 1960s, ‘70s, and ‘80s. The IMSR is a descendant of DMSR — “denatured” MSR technology, which involves the use of a “low enriched” amalgam of uranium isotopes. The most fundamental departure for the technology is that the nuclear fuel is a salt, such as uranium tetrafluoride, that is maintained in a molten state. The fuel generates heat via nuclear fission, as is the case with conventional reactors. However, instead of using a separate working fluid to convey heat from the reactor core to a steam turbine, the MSR conveys heat by circulating the molten fuel itself.
On its website, Terrestrial Energy states that the IMSR design has major advantages such as enhanced safety, reduced generation of radioactive waste, and less susceptibility to the uncontrolled proliferation of nuclear technology. It also has an economic profile that Terrestrial hopes will change the calculus for investors in nuclear energy. This comes substantially from the reactor’s 600 degree Celsius operating temperature. Whereas the 300 degree C temperature found in a conventional reactor is geared exclusively toward production of steam for electricity generation, the MSR’s elevated temperature can be applied to a variety of industrial processes. In a recent speech, Terrestrial’s Board Chairman Hugh MacDiarmid mentioned potential applications “in the petrochemical and refining industries, in ammonia production, in hydrogen production, in clean steel production, natural resource extraction, [and] desalination.”
The MSR technology will allow the business definition of a nuclear plant to expand from electricity generation as a sole product to provision of usable heat for multiple purposes. “Our output is dramatically more useful than the output of a conventional nuclear plant,” MacDiarmid said, “for the simple reason that it is hotter, can be coupled simply to many industrial applications, and is easily delivered over many kilometres to the point of need.” In other words, the heat can be shared across a variety of applications that are chosen and operated according to a dynamic algorithm that maximizes the creation of financial value.
A previous post on AmmoniaEnergy.org linked to a 2013 paper by scientists at the National Renewable Energy Laboratory and Idaho National Laboratory in the U.S. The paper surveyed the field of nuclear-renewable hybrid energy systems, defined as “integrated facilities comprised of nuclear reactors, renewable energy generation, and industrial processes that can simultaneously address the need for grid flexibility, greenhouse gas emission reductions, and optimal use of investment capital.” An integrated MSR-ammonia plant would not fit this definition since it does not include a renewable energy component, but it clearly involves a closely related form of hybridization.
The economic rationale for hybridization has its origin in the energy gradient that is inherent in ammonia production. In thermodynamic terms, the diatomic nitrogen in the atmosphere is at a very low state of embedded chemical energy. The ammonia molecule, by contrast, is at a relatively high state of embedded energy. (This is why it can serve as a fuel.) To transform low-energy diatomic nitrogen into high-energy NH3, an external source of energy must be supplied. Natural gas represents a low-cost form of such energy and has the added benefit of supplying the hydrogen needed for the reaction. These factors constitute a challenging economic bar for competing ammonia synthesis processes to clear.
The 600 degree heat produced by a molten salt reactor represents an alternative source of energy to drive the ammonia reaction, specifically through the use of high-temperature electrolysis (HTE). As reported in an AmmoniaEnergy.org post on concentrated solar fuels, the elevated temperature in an HTE reactor allows a reduction in the amount of electricity needed for electrolysis to occur. If heat can be supplied at a sufficiently high temperature and a sufficiently low cost, it may be possible for an HTE-based system to compete with the conventional ammonia process.
Terrestrial Energy USA has been working with Idaho National Laboratory in the U.S. to model the economics of MSR-based hybrid energy systems. In a brief interview today, John Kutsch, Terrestrial Energy USA’s Vice President of Business Development, said, “We want to know, is something like ammonia production not just technically feasible but a practical financial play?” The work is not complete, but Kutsch said the company is very encouraged by the results to date.
The Fortune magazine contributor James Conca identifies Terrestrial Energy within a new vanguard of nuclear energy companies that are moving forward with advanced reactor designs. In an article published on February 5, he gives small modular reactors prominent mention on a list of “trailblazing” nuclear energy technologies, and mentions Terrestrial Energy’s state of technological development as evidence that “new reactor designs are pretty advanced and ready to be rolled out.” The article describes several bills now receiving consideration in the U.S. Congress that would encourage new investment in nuclear energy.