10 C.F.R. § 11.7
As used in this part:
Terms defined in parts 10, 25, 50, 70, 72, 73, and 95 of this chapter have the same meaning when used in this part.
NRC-"R" special nuclear material access authorization means an administrative determination based upon a Tier 3 background investigation that an individual in the course of employment is eligible to work at a job falling within the criterion of § 11.11(a)(2) .
NRC-"U" special nuclear material access authorization means an administrative determination based upon a Tier 5 background investigation that an individual in the course of employment is eligible to work at a job falling within the criterion of § 11.11(a)(1) or § 11.13 .
Special nuclear material access authorization means an administrative determination that an individual (including a contractor or consultant) who is employed by or is an applicant for employment with an affected Commission contractor, licensee of the Commission, or contractor of a licensee of the Commission may work at a job which affords access to or control over special nuclear material and that permitting the individual to work at that job would not be inimical to the common defense and security.
10 C.F.R. §11.7