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December 2015, No. 3 Vol. LII, Sustainable Energy

The Problems We Face

In 2015, the United Nations adopted 17 Sustainable Development Goals (SDGs) for the world. These are summarized broadly as ending poverty, ensuring access to food, clean water, energy, global health and education, achieving gender equality, securing decent work for all, building resilient infrastructure, reducing income inequality, promoting urban development, sustainable consumption and production, finding climate change solutions, preserving the oceans, preventing deforestation, and implementing? frameworks to reach these goals, including the creation of a global partnership for sustainable development.

There is no doubt that these are lofty goals. The question arises, however, of how the United Nations and Member States approach these issues, and how to assign relative importance to potential solutions.

I would propose that the development of small modular molten salt reactors (MSRs), including the denatured variety, would have the potential to advance several SDGs simultaneously.

Atomic Power Concepts

One of the seemingly unlikely solutions to these pressing problems may in fact be atomic power, although not in its current form. The key principles of nuclear power generation are based on the force that holds the parts of an atom together. If an atom is unstable, it will try to reach a more stable state by breaking apart. The atom can be naturally unstable or can be made unstable when additional neutrons are added to the nucleus.

When an atom becomes more stable and releases particles, it also releases immense amounts of energy that can be used to generate enough heat in a closed system to power a turbine. Radiation, which is often misunderstood, is largely naturally-occurring. There are several types of radiation that all have different effects and uses.

Concerns with nuclear power stem from three major sources: nuclear warheads and their proliferation, core meltdowns and system failures, and nuclear waste. These are all valid points that may be addressed through a conceptual and fundamental rethinking of the way atomic power is generated.

Small Modular Molten Salt Reactors: A Solution for Our Times

MSRs were pursued in the United States largely between the 1950s and 1970s. Unlike current reactors they offered unique solutions to many challenges that conventional reactors face.
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• Salts were already in a molten state, making the term ¡°meltdown¡± irrelevant. If the system is overheating, the salts are passively drained into a cooling tank.
• Radioactive materials form stable bonds in the system. Volatile materials are constantly removed.
• MSRs operate at atmospheric pressure, making incidents such as the 2011 nuclear meltdowns in Fukushima, Japan, impossible.
• Many MSRs have the ability to break down existing nuclear waste in their converter design.
• MSR systems can utilize fissile material much more efficiently than standard nuclear reactors.
• MSRs can be used for load following without excess reactivity due to strong negative void and temperature coefficients.
• Terrestrial thorium, a potential fertile material for MSR use, is about three times as abundant as uranium in the Earth¡¯s crust. Thorium, which is currently treated as a waste product in rare earth mining and has relatively little commercial value, can be extracted using dredge mining (as opposed to more invasive means) or even extracted from the oceans. ?
• MSR systems can potentially operate in a denatured form, making them more proliferation-resistant than other MSR or traditional designs.
• These designs can operate in a completely closed-loop form with a Rankine or Brayton turbine, eliminating the need to be near large bodies of water such as with current reactors.
• The technology is scalable, potentially modular, and can be deployed on a large scale once commercialization efforts are underway.

There are many variations of this design, but this is the model that has undergone the most research and experimentation.

One of the designs that deserves closer examination is the Denatured Molten Salt Reactor that can operate as a fuel source for several years without human interference. This would also allow for a quicker, safer deployment of the technology around the globe with fewer concerns for proliferation.
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The basic design of the MSR looks like this:

Applications of MSRs

The variety of applications of MSRs is perhaps the most important reason to develop this technology, which has the ability to provide electricity, water, medical isotopes and energy for food production, diminish current stockpiles of nuclear waste, and provide power in remote locations, among other uses.

Power and Water for All

Due to the nature of the challenges that Earth faces, it is necessary first and foremost to ensure adequate access to electricity, water and sanitation for all. MSRs have the unique ability to do this. Since the types of fuels that can be used in the system vary greatly, the efficiency and fuel utilization are orders of magnitude higher than with standard uranium reactors, and the technology is widely applicable across a range of uses, it is hard to discount the plausibility of MSRs in the future development of mankind.

Additionally, since radioactive materials are completely removed from the power generation system, operating at over 100¡ã C, it will be possible to purify water and sterilize waste with excess heat. This can be done in places near the ocean, such as California, and provide clean water for human consumption.

Disaster Response and Microgrids

Since these reactors can be modular and scalable, they can be reduced to a size that can be manufactured and deployed on a large scale to power operations that do not have access to traditional infrastructure. This would include military bases, developing nations, and disaster response facilities in places where the infrastructure has been damaged. The nature of these reactors is that they are able to match their loads, making them an ideal candidate for short-term grid operation.

Medical Isotope Production

As a by-product of reactor operation and some of its fuel decay chains, medical isotopes are also created. These can be used as medicine, in research for advanced Alpha Particle Targeting treatment, for radiographs, as well as a number of other medical uses. Thorium has already been a subject of research in the United Kingdom. Additionally, current radioisotope production is concentrated in aging reactors in South Africa and Canada. Having a local source for these isotopes would prove to be beneficial for affordable use across many nations.

Cleaning Up Nuclear Waste and Preventing Proliferation

As mentioned earlier, various MSRs have different capabilities, and some of them are uniquely suited for nuclear waste and proliferation. Some companies in the United States are focusing on creating ¡°burner¡± reactors. These systems are able to maintain a higher power density and use nuclear waste as a fuel source for the reaction. This would allow us to deplete current stockpiles into transuranics that have a fraction of the reactivity of current waste. We would not have to worry about mining, separating, and manufacturing additional fuel and could instead use up the existing energy stored in it that traditional reactors are unable to use.

Other MSRs, however, want to focus on preventing nuclear proliferation. In standard MSRs with chemical processing for a two-fluid design, there is a separation of some of the isotopes to increase the neutron economy of the reactor. This step, however, allows for the potential to separate out this material and use it in radioactive armaments. Although difficult, it is still possible. To remedy this, the denatured MSR was developed in 1979-1980. This system may be modified to use a single tank of fuel without separation, have a small hindrance to the conversion ratio of fertile to fissile material, and would have enough denatured uranium to maintain a composition that is unsuitable for nuclear bombs. This design, once tested and completed, could be sent anywhere in the world with much less concern for proliferation. This could help to provide power and water to some of the nations that most desperately need it.

Beyond Earth

Finally, applications of this technology can be expanded beyond Earth. MSRs could become a strong candidate for power systems used to sustain human life or robotic missions in space. Energy, heat and water purification systems could be streamlined and the reactor could potentially operate for several years without human intervention. Waste water could be processed and sterilized, allowing its use for a sustainable system supporting life outside Earth.

There are many problems and issues facing the planet and its inhabitants. Finding solutions for any one of them can be a daunting task, let alone solutions that could help to achieve several development goals. Properly utilized atomic power can save lives and resources, and it is time for a fundamental re-examination of its applications and further development of peaceful atomic research. MSRs represent a revival of an old idea that proved to be one of the single best ways to provide safe, clean energy for millennia to come.?