Description of Source:
Uranium ore generally contains less than 1% uranium. Thus, the process used to extract the uranium from the ore generates a large amount of waste. This waste is called uranium mill tailings. Tailings are collected in impoundments that vary in size from 20 to 400 acres. The radium contained within the mill tailings decays and emits Radon-222, a radioactive gas known to cause lung cancer in people. This Subpart applies to uranium mill tailings piles that are no longer operational. However, this Subpart does not apply to any uranium mill tailings pile regulated by the Nuclear Regulatory Commission under title II of the Uranium Mill Tailings Radiation Control Act of 1978. This Subpart does apply to the 24 abandoned uranium mill tailings piles controlled by the U.S. Department of Energy and regulated under Title I of the Uranium Mill Tailings Radiation Control Act.

Radon-222, a radioactive gas, is created by the decay of the radium found in uranium mill tailings. This gas can be released both during and after the processing of uranium ores. Radon-222 is known to cause cancer in people. Inactive tailings piles must be stabilized to minimize the release of Radon-222 into the air.

The Standard: 
Radon-222 emissions to the ambient air from a uranium mill tailings pile that is no longer operational shall not exceed more than 20 picocuries per square meter per second of Radon-222.

Reporting Requirements: 
Owners and operators of uranium mill tailings piles must conduct radon emissions testing. The results of these tests, as well as a description of the control measures taken to reduce the radon emissions from the pile, must be submitted to EPA in writing.

More Information:
Electronic Code of Federal Regulations (e-CFE): 40 CFR 61, Subpart T
EPA Radiation Protection Division NESHAPs Home Page