TerraPower’s second advanced reactor design is the Molten Chloride Fast Reactor (MCFR) technology. This project answers a multitude of challenges by expanding the ability of nuclear reactor technology to decarbonize the economy in sectors beyond electricity. The MCFR project has the potential to be a relatively low-cost reactor that can operate safely in new, higher temperature regimes. This means the technology can do more than generate electricity; it offers benefits to potential alternative markets, such as providing carbon-free heat for industrial processes, and thermal storage.
Natrium reactors are uranium fueled. No Natrium reactor—from the demonstration plant, to the first set of commercial plants, or the subsequent larger plants—will use plutonium as a fuel. Both the demonstration plant and the first set of commercial plants will run on high-assay low-enriched uranium (HALEU). Natrium plants will not require reprocessing and will run on a once-through fuel cycle that limits the risk of weapons proliferation. Natrium technology will, nonetheless, reduce the volume of waste per megawatt hour of energy produced at the back end of the fuel cycle, by five times, without any reprocessing because of the efficiency with which it uses the fuel.
TerraPower plans to build the 345 MWe Advanced Reactor Demonstration Program (ARDP) demonstration reactor with an integrated energy storage system and to market subsequent commercial reactors with a similar design and size.
Depending upon market conditions, future generations of Natrium reactors could be larger designs, up to the GW scale. Doing so could allow the reactors to take advantage of the benefits of “breed-and-burn” designs that would allow the plants to be refueled with natural unenriched uranium or even depleted uranium. By enabling refueling to occur with these enrichment plant wastes or unenriched materials, the risk of proliferation from exported reactors is further reduced. Inside the reactor core, the reactor does convert some U-238 into a fissile isotope (Pu-239), which it then uses as fuel with uniquely high efficiency before removal. This is the same basic process that occurs in the current generation of light water pressurized reactors, which have been successfully exported around the world.
From its beginnings over a decade ago, TerraPower has made reduction of weapons risks a foundational principle. Ethical global exportability is one of the keys to addressing human poverty and climate change. With the participation of retired weapons laboratory directors and their expert personnel, TerraPower laid out the once-through fuel cycle approach that avoids reprocessing, keeps used fuel intact and countable, makes fuel reloads a rare, monitorable event, and eventually reduces need for enrichment plants. The simplified total fuel infrastructure also reduces the opportunities for theft, terrorist actions or accidents during fuel transport by an order of magnitude relative to reprocessing-based approaches.
The Natrium design introduces many new inherent safety features that prevent accidents. No pumps and emergency power are needed to maintain safe conditions after shutdown. The reactor has what is called a global negative temperature coefficient and automatically seeks safe low power conditions in the case of an unexpected high temperature excursion. This has been shown theoretically and experimentally for a sodium-cooled reactor using metal fuel. An unrecognized but very important feature of the reactor is that it operates at very low internal pressures, thus simplifying the fabrication of the vessel and other components as well as reducing the consequences of any component failure. The design offers several additional safety features, but the net implication is that large exclusion zones are no longer needed and siting options greatly expanded.
The first generation 345 MWe Natrium reactors will use uranium with about the same utilization as light water reactors. The breed-and-burn process that occurs within the 600 MWe reactor makes several times more efficient use of uranium resources, though the identification of large uranium resources makes this a relatively unimportant issue. The ultimate 1000 MWe Natrium reactor should make about 33 times more electrical energy per ton of mined uranium than present day light water reactors without the need for reprocessing.
The Natrium Demonstration Plant will prove out the systems and operations for the first generation of 345 MWe plants as well as qualifying many components for the larger breed-and-burn plants that follow. The plant will be started and initially checked out with the type of “sodium wetted” fuel that has been used before, including at INL. A transition to new higher performance fuel will then be made to achieve full commercial operations. The Natrium Demo is based on decades of sodium reactor operations and on a decade of focused development sponsored at national labs, universities, and companies.
The public-private partnership, or cooperative agreement, for the design and construction of a Natrium Demonstration Project was approved by DOE. The agreement calls for startup in seven years from signing. This aggressive schedule assumes funding is provided on the “S-curve” needed for on-time completion.
Conclusion
With the momentum toward meaningful action on global climate change such as the climate talks get under way, many countries have been investing in low-carbon energy sources to fuel their economies. From wind turbines and solar panels to new forms of biofuels and hydropower, a mix of generation types will be vital to meeting global energy demand in a responsible and sustainable way. However, it has been argued that the current renewable energy sources is still struggling with satisfying the continuously increasing demand of energy without using the conventional energy resources, for instance, fossil fuel, which give major negative impacts on the environment. Nuclear power plants provide 20% of the electricity consumed in the United States with extreme reliability, turned on and providing significant power over 90% of the time. This performance exceeds, on average, that achieved with almost all other forms of electricity generation. The safety record in the United States is also remarkably good, with no harm to operators or the public. Compared to the conventional reactors capturing only about 1 percent of the energy potential of their fuel, TWR represents a new class of nuclear reactor. Conceptually, TWR reactor design allows TWR to utilize depleted uranium as their primary fuel. These innovations greatly simplify the nuclear fuel cycle by eliminating or reducing the need for enrichment, reprocessing, and waste storage and disposal. Fissile fuel is both produced and then consumed in-reactor, greatly improving the fuel efficiency of the TWR and resource availability for the reactor. It’s the only carbon-free energy source that can reliably deliver power day and night, through every season, almost anywhere on earth, that has been proven to work on a large scale.
References
[1] W. A. Sahlman et al., "TerraPower." Harvard Business School, Case 813-108, November 2012 (Revised December 2013).
[2] D. Primack, "Bill Gates' Clean Energy Plan Isn't Ready for Primetime," Fortune, 1 Dec 15.
[3] R. A. Guth, "A Window into the Nuclear Future," Wall Street Journal, 28 Feb 11.
[4] K. Fehrenbacher, "TerraPower: How The Traveling Wave Nuclear Reactor Works," Gigaom, 15 Feb 10.
[5] T. Ellis et al., "Traveling-Wave Reactors: A Truly Sustainable and Full-Scale Resource for Global Energy Needs," Proc. Int. Cong. Advances in Nuclear Power Plants (ICAPP), San Diego, California, Paper No. 10189, 13 Jun 10.
[6] W. N. Cottingham and D. A. Greenwood, An Introduction to Nuclear Physics, 2nd Ed. (Cambridge University Press, 2001), pp.115-125.
