---
kind: "section"
citation: "40 C.F.R. § 61.221"
title: "40"
number: "61.221"
heading: "Definitions."
url: "https://uscodex.org/cfr/40/61.221"
---

# §61.221. Definitions.


As used in this subpart, all terms not defined here have the meanings given them in the Clean Air Act or [subpart A of part 61](/cfr/40/part61-subpartA.md). The following terms shall have the following specific meanings:

- (a) Long term stabilization means the addition of material on a uranium mill tailings pile for the purpose of ensuring compliance with the requirements of [40 CFR 192.02(a)](/cfr/40/192.02.md?p=a). These actions shall be considered complete when the Nuclear Regulatory Commission determines that the requirements of [40 CFR 192.02(a)](/cfr/40/192.02.md?p=a) have been met.
- (b) Operational means a uranium mill tailings pile that is licensed to accept additional tailings, and those tailings can be added without violating subpart W or any other Federal, state or local rule or law. A pile cannot be considered operational if it is filled to capacity or the mill it accepts tailings from has been dismantled or otherwise decommissioned.
- (c) Residual radioactive materials shall have the same meaning as in section 101(7) of the Uranium Mill Tailings Radiation Control Act of 1978, [42 U.S.C. 7911(7)](/usc/42/7911.md?p=7).
- (d) Tailings shall have the same meaning as in section 101(8) of the Uranium Mill Tailings Radiation Control Act of 1978, [42 U.S.C. 7911(8)](/usc/42/7911.md?p=8).
- (e) In significant part means in a manner that is not reasonably expected to materially (i.e., more than de minimis) interfere with compliance with the 20 pCi/m 2-s flux standard as expeditiously as practicable considering technological feasibility (including factors beyond the control of the licensee).

## Notes

### Amendments

[54 FR 51702, Dec. 15, 1989, as amended at 59 FR 36301, July 15, 1994]

### Source

Source: 54 FR 51702, Dec. 15, 1989, unless otherwise noted.

### Authority

Authority: 42 U.S.C. 7401 et seq.

### Source

Source: 38 FR 8826, Apr. 6, 1973, unless otherwise noted.

### Amendments

[54 FR 51702, Dec. 15, 1989, as amended at 59 FR 36301, July 15, 1994]