As the United States grapples with an aging nuclear power infrastructure, policymakers face the tough decision of whether to retire or retrofit the reactors that currently generate nearly 20% of the nation’s electricity. With 92 reactors in operation, the US boasts the largest nuclear fleet worldwide, but many of these facilities have been running for over 50 years and are nearing the end of their expected lifetimes. While nuclear energy is considered a low-carbon alternative to fossil fuels like coal, oil, and natural gas, a new study by MIT researchers adds another dimension to this debate: the impact on air quality.
The study, published in the journal Nature Energy, examines a hypothetical scenario in which all nuclear power plants in the US are shut down and replaced by other energy sources, such as coal, natural gas, and renewables, for an entire year. The results suggest that air pollution would indeed increase as fossil fuel usage ramps up to compensate for the loss of nuclear power. The team quantified this impact, estimating that an additional 5,200 pollution-related deaths could occur over a single year as a direct consequence of the increased air pollution.
If more renewable energy sources were to become available to the grid, as anticipated by 2030, air pollution would be mitigated, but not entirely eliminated. Even under a scenario with significantly more renewable energy, the researchers found a slight increase in air pollution in some regions, resulting in 260 pollution-related deaths over one year. The study also highlights that Black or African American communities, who disproportionately reside near fossil-fuel plants, would be most exposed to the increased pollution levels.
Lead author Lyssa Freese, a graduate student in MIT’s Department of Earth, Atmospheric and Planetary Sciences (EAPS), emphasized that this research adds another layer to the ongoing debate about the environmental health and social impacts of nuclear power plant shutdowns. The conversation surrounding these shutdowns has primarily revolved around local risks due to accidents, mining, and long-term climate impacts.
“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 (IDSS) and EAPS. She further explained that the air pollution caused by fossil fuel plants is so harmful that any increase, such as that resulting from a nuclear shutdown, will have significant impacts on some populations more than others.
As nuclear power plants have closed in the past, fossil fuel use has increased to compensate for the loss of electricity generation. This phenomenon can be observed in historical instances such as the 1985 closure of reactors in the Tennessee Valley which prompted a spike in coal use and the 2012 shutdown of a plant in California leading to an increase in natural gas consumption. Similarly, in Germany, where nuclear power has almost completely been phased out, coal-fired power initially increased to fill the gap.
Observing these trends, a team of researchers from MIT set out to investigate how the U.S. energy grid would respond if nuclear power were entirely phased out. “We wanted to think about what future changes were expected in the energy grid,” said Freese. “We knew that coal use was declining, and there was a lot of work already looking at the impact of what that would have on air quality. But no one had looked at air quality and nuclear power, which we also noticed was on the decline.”
To analyze the impact of a nuclear power phase-out on air quality and public health, the team utilized an energy grid dispatch model developed by their colleague Jenn. The model simulates the production of every power plant in the country, running continuously to estimate the hourly energy demands in 64 regions across the nation. Functioning similarly to the actual energy market, the model prioritizes plants producing the cheapest energy at any given time, adjusting their production levels up or down accordingly.
The researchers fed the model available data on each plant’s changing emissions and energy costs throughout an entire year. They then ran the model under different scenarios: an energy grid with no nuclear power, a baseline grid similar to today’s grid that includes nuclear power, and a grid with no nuclear power that also incorporates additional renewable sources expected to be added by 2030.
Each simulation was combined with an atmospheric chemistry model to simulate how each plant’s various emissions travel around the country. The research team overlaid these tracks onto maps of population density to examine the impact on populations exposed to pollution. The risk of premature death was calculated for individuals in the path of pollution based on their degree of exposure.
The experts analyzed the effects of shutting down nuclear power plants in the United States and discovered that this action could potentially lead to thousands of pollution-related deaths, as well as hundreds of thousands of premature deaths due to climate change impacts in the coming century.
The research team found a strong correlation between the absence of nuclear power and a decline in air quality. This is particularly evident in the East Coast region, where the majority of the country’s nuclear power plants are located.
With these plants out of operation, the study revealed an increased reliance on coal and gas-fired power plants. Consequently, this shift in power production led to a significant increase in air pollution, resulting in an estimated 5,200 pollution-related deaths across the nation in comparison to the baseline scenario.
The study also highlighted the long-term consequences of such actions on climate change. As the power grid attempts to compensate for the absence of nuclear power, carbon dioxide emissions are likely to rise. The researchers calculated that this increase in emissions could lead to an additional 160,000 premature deaths over the next 100 years due to the exacerbated effects of climate change.
“We need to be thoughtful about how we’re retiring nuclear power plants if we are trying to think about them as part of an energy system,” said Freese. “Shutting down something that doesn’t have direct emissions itself can still lead to increases in emissions, because the grid system will respond.”
Selin emphasized the need for a greater focus on renewable energy sources. “This might mean that we need to deploy even more renewables, in order to fill the hole left by nuclear, which is essentially a zero-emissions energy source. Otherwise, we will have a reduction in air quality that we weren’t necessarily counting on.”
This in-depth analysis sheds light on the potential consequences of phasing out nuclear power in the United States, taking into account the impact on air quality, public health, and the nation’s energy infrastructure. By examining the interplay between different energy sources and their emissions, the study helps policymakers and energy industry stakeholders make informed decisions about the future of nuclear power and its role in the energy mix.
The research was partially supported by the U.S. Environmental Protection Agency, which further emphasizes the gravity of these findings and their implications for both environmental and public health policy.
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