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Nuclear Energy Helps Cut Emission of Nitrogen Oxides, Sulfur Dioxide
Nuclear energy has played a key role in America’s clean-air program for decades. Like hydroelectric power and renewables, nuclear power plants are considered a clean-air energy source because they do not burn anything or emit criteria pollutants regulated by the Clean Air Act. Nearly one-third of total U.S. electricity—30 percent—comes from clean-air sources, and nuclear energy accounts for a large part of that. Because nuclear plants are major contributors to our nation’s electricity supply—generating nearly 20 percent—they also are major contributors to improving our air quality. Only 10 percent of clean-air electricity in the United States comes from sources other than nuclear energy.

Nuclear power plants have helped states meet air-quality standards. Federal air-quality regulations limit pollution through emission “caps” and “permits,” which set a fixed amount of emissions allowed for a range of activities, including electricity production.

As the economy and population grow, electricity demand increases as well. Emissions, however, are not allowed to increase. In fact, the long-term goal is to decrease the emission of criteria pollutants, not just prevent them from increasing. A state or region can more easily remain within its emission caps and still meet its electricity needs when clean-air energy sources are used as much as possible. Improved nuclear plant performance through increased efficiency has helped states reduce air pollution to a greater degree and at a lower cost than expected.

The government has developed extensive regulations to reduce various emissions, including NO_x, associated with ground-level ozone. The EPA created the Ozone Transport Commission and the NO_x Budget Program under the Clean Air Act amendments of 1990 to help reduce ground-level ozone in the northeast and mid-Atlantic states.

This program requires a phased, state-based approach to reduce emissions significantly. Its market-based cap-and-trade program has been effective.

Under this program, NO_x emissions were 4.4 million tons lower in 2005 than the base year of 1990¹. For perspective, nuclear energy prevented the emission of nearly 1 million tons of NO_x in the year 2006. In addition, NO_x emissions prevented by nuclear energy were double those prevented by all other renewable energy sources in 2006.²

The federal government also created regulations to reduce SO₂, associated with acid rain. Nuclear power plants help to meet the SO₂ restrictions imposed by Title IV of the Clean Air Act amendments of 1990.

Under this program, SO₂ emissions were 5.68 million tons lower than the base year of 1990. Nuclear energy avoided the emission of 3.12 million tons in 2006. In addition, the SO₂ emissions prevented by nuclear energy in 2006 were nearly three times those prevented by all other renewables.

New Clean Air Standards Will Increase Competitiveness of New Reactors
EPA established the Clean Air Interstate Rule and the Clean Air Mercury Rule in 2005 to dramatically reduce nitrogen oxides, sulfur dioxide, ozone, particulates and mercury. These regulations will require coal plants, which meet about half of U.S. electricity demand, to invest as much as $50 billion in pollution-control equipment, but it may not be cost-effective to retrofit these controls on older fossil plants.

Regional electric system operators, public utility commissions and electric company executives are jointly responsible for meeting electric demands that are projected to increase by 30 percent by 2030. To do so, new baseload generation, both coal and nuclear, is in the planning stage.

Faced with increased coal-plant compliance costs to meet EPA’s tough new clean-air rules and future costs to meet likely carbon constraints, policymakers and electric companies may look increasingly to nuclear energy to meet a larger percentage of expected baseload demand growth.

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¹ Contributions of 1990 Clean Air Act measured as changes from the 1990 baseline emissions. Data provided by the Energy Information Administration.

² Emissions avoided are calculated using regional and national fossil fuel emissions rates from the Environmental Protection Agency and plant generation data from the Energy Information Administration. Updated: 4/07

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