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Natural Radiation in Wastes From Coal-Fired Power Plants

Fly ash, bottom ash and boiler slag from coal-fired power plants contain small amounts of naturally occurring radioactive material.

  • Naturally radioactive materials that were in coal before processing mostly end up in fly ash, bottom ash and boiler slag.
  • About 80 to 90 percent of fly ash, bottom ash and boiler slag is non-radioactive minerals, typically silicon, aluminum, iron and calcium.

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About Natural Radiation in Wastes From Coal-Fired Power Plants

In 2012, approximately 37 percent of the United States electricity was created by burning coal. Like all rocks, coal contains small amounts of radioactive material that are found naturally in the environment.

Diagram of a coal-fired power plant.

Diagram of a coal-fired power plant.

When coal burns, most of the radioactive material does not burn and ends up in three types of wastes:

  • Fly ash is carried by hot gases and trapped by stack filters. It is the largest of the coal combustion wastes (about half) by weight.
  • Bottom ash is too large or heavy to be carried by gases and settles to the bottom of the boiler. Just over ten percent of coal combustion waste is bottom ash.

  • Boiler slag is formed when ash melts under the intense heat of combustion and collects at the bottom of the boiler and in exhaust stack filters. It makes up about two percent of coal combustion waste.

Generally, these wastes are only slightly more radioactive than the average soil in the U.S.

While 99 percent of fly ash is captured by filters, small amounts can escape into the air. Government regulations require power plants to limit the amount of fly ash that escapes into the environment and to dispose of collected ash properly.

A survey by the American Coal Ash Association showed that about 45 percent of all fly ash, bottom ash and boiler slag was reused. Its use depended on the characteristics of the waste. Just over 60 percent of collected fly ash was used in concrete and blended cement. Almost 70 percent of bottom ash was used for concrete, blended cement and to fill structures or embankments. About 80 percent of boiler slag was used as blasting grit or roofing granules.

Fly ash, bottom ash and boiler slag can also be used to fill structures or embankments, in snow and ice control, as waste stabilization/solidification, or as aggregate.

Bottom ash Boiler slag Different colors of fly ash.
Bottom ash Boiler slag
Source: American Coal Ash Association

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Rules and Guidance

U.S. Environmental Protection Agency (EPA)

EPA develops standards for coal-fired power plants under the Clean Air Act, Clean Water Act, Safe Drinking Water Act, Resource Conservation and Recovery Act and the Comprehensive Environmental Response, Compensation, and Liability Act. EPA has primary responsibility for setting federal radiation standards for exposure to naturally occurring radioactive materials.

The States

Each state has one or more programs to address radiation protection, including naturally occurring radioactive materials. Most states control public exposure to radioactive materials through programs implementing federal environmental laws such as the Clean Air Act and the Clean Water Act. Find your state radiation program contact exit EPA.

U.S. Department of Energy (DOE)

DOE provides grants for research and studies on coal-fired plants and on clean coal technologies.

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What you can do

The amount of natural radiation in wastes from coal-fired power plants is so small that no precautions need to be taken.

There are other harmful emissions from power plants and industrial sources that are regulated. You can learn more about EPA's air pollution standards by visiting the Plain English Guide to the Clean Air Act.

If you are concerned about air quality from any type of emission, you can track the Air Quality Index for your area at the government's AirNow website.

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Where to learn more

Coal Ash
August 12, 2014. U.S. Environmental Protection Agency
This webpage provides information about coal ash and coal combustion residuals (CCR).
AIRNow
August 12, 2014. Cross-Agency U.S. Government Website
This webpage provides information about air quality in your area.
The Plain English Guide to the Clean Air Act
August 12, 2014. U.S. Environmental Protection Agency 
This webpage provides basic information about the Clean Air Act in easy to understand language.
Coal Combustion: Nuclear Resource or Danger  exit EPA
August 12, 2014. Oak Ridge National Laboratory, UT Battelle for the U.S. Department of Energy
This article discusses the radioactive pollution associated with the burning of coal.
TENORM: Coal Combustion Residuals
August 12, 2014. U.S. Environmental Protection Agency
This webpage provides a description of technologically enhanced naturally occurring radioactive material and links to more information.
Clean Coal Research
August 12, 2014. U.S. Department of Energy
This webpage provides information on DOE's clean coal research and development efforts.
Cleaner Power Plants
August 12, 2014. U.S. Environmental Protection Agency
This webpage provides information on setting standards for toxic emissions from power plants.
Overview of the Clean Air Act and Air Pollution
August 12, 2014. U.S. Environmental Protection Agency
This website provides information about EPA's air pollution standards.
American Coal Ash Association (ACCA) Survey Report (PDF) (1 p, 94 K About PDF) exit EPA
August 12, 2014. American Coal Ash Association.
This chart contains the results of a survey of coal combustion companies about the amount of combustion residuals produced and the amount reused.
Summary of the Clean Water Act
August 12, 2014. U.S. Environmental Protection Agency
This website provides information about the Clean Water Act.
Safe Drinking Water Act (SDWA)
August 12, 2014. U.S. Environmental Protection Agency
This website provides information about EPA?s standards for drinking water.
Summary of the Resource Conservation and Recovery Act
August 12, 2014. U.S. Environmental Protection Agency
This website provides information about EPA?s authority to control hazardous waste.
Superfund: CERCLA Overview
August 12, 2014. U.S. Environmental Protection Agency
This website provides information about the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA).

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