Andrew Yang, like many of the 2020 Democratic President’s hopes, has an ambitious plan to wean America off fossil fuels. Unlike many other candidates, an integral part of his plan to combat climate change is to use nuclear energy – thorium in particular. According to Yang, thorium is “superior to uranium on many levels”. But Yang is not alone; Thorium boosters have been extolling their supposed virtues for years.
Do the claims about thorium really continue? The bulletin reached out to Nicholas R. Brown, an associate professor in the Department of Nuclear Engineering at the University of Tennessee, to investigate five common claims about next-generation thorium and nuclear reactors. Brown’s answers are below.
While existing and new nuclear reactors in the US may indeed be part of a long-term carbon-free energy mix, the general public has good reason to be skeptical that thorium can or should play a role in the future.
Claim: Thorium reactors would be more economical than conventional uranium reactors, especially because thorium is more abundant than uranium, has more energy potential than uranium and does not need to be enriched.
Not correct. Although thorium is more abundant than uranium, the cost of uranium is a small fraction of the total cost of nuclear energy. The economics of nuclear power are determined by the capital cost of the facility, and building a power plant with a thorium reactor is no cheaper than building a power plant with a uranium reactor. In addition, the use of thorium in existing reactors is technically feasible, but would not bring clear commercial benefit and would require other new infrastructure.
In addition, there is technically no thorium reactor. Thorium has no isotopes that easily split to produce energy. Thorium cannot be used directly as fuel, but is a fertile core that can be converted into uranium in a reactor. Thorium only becomes useful as a nuclear fuel after it has been converted to uranium. Even for a reactor using thorium in its fuel cycle, most of the energy produced would actually come from uranium fission.
Claim: Next generation thorium reactors would be safer than current reactors.
Right, but misleading. Nuclear energy is already very safe, and Yang is right about it. The current US nuclear fleet generates around 20 percent of all electricity in the US and has an excellent safety record despite accidents like Three Mile Island. When it comes to new reactors, while some next-generation designs may offer potential safety advantages over current reactors, they can operate in either thorium-uranium or uranium-plutonium fuel cycles. Thus, the benefits depend on the inherent safety of the next generation designs, not the use of thorium.
Claim: The waste from thorium reactors would be easier to handle than the waste from today’s uranium reactors.
Not correct. A comprehensive 2014 study by the US Department of Energy found that thorium-uranium fuel cycle wastes had radioactivity similar to that of uranium-plutonium fuel cycles after 100 years and actually had higher waste radioactivity after 100,000 years.
Claim: Thorium would be more resistant to proliferation than current reactors – you can’t make nuclear weapons out of it.
Not correct. A 2012 study funded by the National Nuclear Security Administration found that the by-products of a thorium fuel cycle, particularly uranium 233, could potentially be an attractive material for making nuclear weapons. A study published in Nature by the University of Cambridge in 2012 also concluded that thorium fuel cycles pose a significant risk of proliferation.
Claim: Building new nuclear reactors is likely to be necessary if the United States is to achieve net zero emissions by 2049.
True. Nuclear power is already the primary low-carbon energy source for base load electricity generation. Although sun and wind have their place in the energy mix, the main advantage of nuclear energy is that it is not intermittent, as is the case with sun and wind, so it is almost always available without the need for energy storage. Hence, new nuclear reactors will be needed to both replace aging ones and meet a net zero CO2 emissions target. However, thorium-uranium fuel cycles do not offer any inherent advantages over uranium-plutonium fuel cycles, so the new reactors do not need to run on thorium.
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