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Air and Water:  

Subpart W: Operating Uranium Mill Tailings


Subpart W protects the public and the environment from the emission of radon-222 from uranium mills and their associated tailings. The standard limits radon-222 emissions rate to 20 picocuries per square meter per second and requires that new tailings impoundments meet one of the two following work practice standards:

  1. There are two impoundments in operation at any time (including existing impoundments), each of which cannot be larger than 40 acres. Tailings management and disposal is by phased disposal.
  2. Tailings are immediately dewatered and disposed of with no more than 10 acres uncovered at any time. Operators must also follow applicable requirements in 40 CFR 192.32.

Since uranium ore generally contains less than 1 percent uranium, uranium milling produces large quantities of tailings. These tailings are collected in impoundments that vary in size from 20 to 400 acres. The tailings contain large amounts of radium, and therefore, they emit large quantities of radon.

There are 26 NRC-licensed uranium mills in the western United States. As the price of uranium continues to increase, more mines are being considered, both in the western United States, and in areas not usually associated with uranium mining, such as Virginia.

Owners or operators must test emissions and report to EPA annually.

In addition there are general requirements, which all facilities subject to any NESHAP must meet, 40CFR61, Subpart A: General Provisions Exit EPA Disclaimer.

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