Research quantifies the health and climate value of the U.S. nuclear fleet

May 9, 2023, 7:00AMNuclear News
A still from a video posted by MIT that illustrates the air pollution that would be generated over one year by a grid with no nuclear power. (Credit: MIT)

Nuclear power is the single largest source of clean energy in the United States, but how can the value of “clean” be measured? Two recent reports by researchers at the Massachusetts Institute of Technology and Pacific Northwest National Laboratory, respectively, measured the clean energy benefits of nuclear energy in different ways: the benefits to human health from the air pollution avoided and the future economic value of avoided carbon emissions.

Carbon value: PNNL earth scientist Son H. Kim worked with the Joint Global Change Research Institute (JGCRI), a partnership between PNNL and the University of Maryland, to quantify the contribution of existing nuclear reactors toward the country’s climate goals, both now and with decades of extended operation. The results, published in the ANS journal Nuclear Technology in 2021, received fresh attention in a feature article published on May 2 by PNNL.

“Our existing nuclear power plants are aging, and with their current 60-year lifetimes, nearly all of them will be gone by 2050,” Kim is quoted as saying in the PNNL article. “It’s ironic. We have a net zero goal to reach by 2050, yet our single largest source of carbon-free electricity is at risk of closure.”

New reactor deployments would mitigate that risk, and work that Kim published in an August 2022 report for the Department of Energy’s Office of Nuclear Energy used similar computational tools to model the potential capacity—and thus carbon value—provided by new nuclear reactors under different assumptions.

Mitigation cost savings, or carbon value, are measured as dollars saved by reducing greenhouse gas emissions. Kim’s 2021 research put the value of existing nuclear plant lifetime license extensions from 40 to a maximum of 100 years at between $330 billion and $500 billion (at 100 years) under a scenario that limits global temperature to 2°C. Every gigawatt, roughly equivalent to one large light water reactor in the current fleet, translated to $5 billion saved because it was produced without carbon emissions that would require future mitigation.

In his work published in 2022, Kim focused on the deployment of new nuclear plants under different nuclear plant capital cost scenarios and different U.S. carbon mitigation policies and economy-wide net-zero emission goals. The nuclear capital costs assumed ranged from $6,600 to $2,600 per kilowatt, and the projected nuclear power capacity under different cost assumptions ranged from 130 GW to 240 GW in 2050 and 90 GW to 450 GW in 2100 in a reference scenario without a carbon tax or economy-wide emissions goal. In fact, Kim concluded that “lowering the nuclear capital cost was always beneficial for the expanded deployment of nuclear energy no matter the carbon tax level, and in the long term, an aggressive reduction of the nuclear cost had a relatively greater impact on nuclear expansion than the carbon penalty.”

Kim also found that a $50 per ton of CO2 carbon tax would be equivalent to reducing the nuclear capital cost by $1,000 per kilowatt.

Kim concluded that “By 2100, the nuclear share of electricity was 50 percent or more with low cost nuclear under carbon mitigation efforts. The longevity of nuclear power technologies and the sustained investments of competitive nuclear power contributed to the accumulation of total nuclear power capacity and high nuclear shares over time. Reductions in the capital cost of nuclear power technologies had a clear and pronounced impact on the expanded deployment of nuclear power under all scenarios.”

Air pollution health effects: Without nuclear power, how would the pattern of air pollution shift, and who would be affected? Researchers at MIT took on those questions in a study published last month in Nature Energy and described in an MIT News article published the same day. To carry out research, which was supported in part by the Environmental Protection Agency, they used an energy grid dispatch model to investigate what would happen if every nuclear power plant in the country was shut down and other sources such as coal, natural gas, and renewable energy had to meet the energy needs for an entire year.

Not surprisingly, given experience in New York, California, Germany, and other places where nuclear power plants have been shut down, their analysis showed that air pollution would increase as coal, gas, and oil sources ramp up to compensate for lost nuclear power.

The team inputted available data on each plant’s emissions and energy costs throughout an entire year. They ran the model under scenarios that included an energy grid with no nuclear power, a baseline grid including existing nuclear power plants, and a hypothetical grid with no nuclear power but with “additional renewable sources that are expected to be added by 2030.”

Because air pollution doesn’t stay where it is released, data from each simulation were combined with an atmospheric chemistry model to map how emissions move around the country and vary by season. These results were overlaid on maps of population density. A video published by MIT illustrates the results over one full year. For populations in the path of that pollution, the researchers calculated the risk of premature death based on degree of exposure and found that a grid without nuclear power would cause an additional 5,200 pollution-related deaths over just one year, compared with the baseline grid, according to MIT.

Air pollution worsened in every scenario without nuclear power, mainly affecting regions in the eastern United States. Even under a scenario with higher renewable energy by the year 2030, “there is still a slight increase in air pollution in some parts of the country, resulting in a total of 260 pollution-related deaths over one year,” according to MIT.

The researchers also calculated that more people are also likely to die prematurely due to climate impacts from the increase in carbon dioxide emissions. The climate-related effects from additional carbon dioxide could lead to 160,000 additional deaths over the next century.

When they looked at the populations directly affected by increased pollution, the researchers found that black communities—a disproportionate number of which are near fossil fuel plants—would experience the greatest exposure.

“This adds one more layer to the environmental health and social impacts equation when you’re thinking about nuclear shutdowns, where the conversation often focuses on local risks due to accidents and mining or long-term climate impacts,” said lead author Lyssa Freese, a graduate student in MIT’s Department of Earth, Atmospheric, and Planetary Sciences (EAPS).

“In the debate over keeping nuclear power plants open, air quality has not been a focus of that discussion,” added study author Noelle Selin, a professor in MIT’s Institute for Data, Systems, and Society and EAPS. “What we found was that air pollution from fossil fuel plants is so damaging, that anything that increases it, such as a nuclear shutdown, is going to have substantial impacts, and for some people more than others.”

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