Document: 10 CFR Part 20
Document ID: f9fa227e-b871-4624-b491-d8e41103d10e
Document Type: cfr
Title: Definitions.
Source: 10 CFR Part 20
Source URL: https://www.ecfr.gov/current/title-10/part-20/section-20.1003
Revision Date: 
Chapter: 
Section ID: 20.1003
CFR Part: 20
CFR Title: 10

Content:
iformly. For calculating the effective dose equivalent, the values of w T are: Organ Dose Weighting Factors Organ or tissue w T Gonads 0.25 Breast 0.15 Red bone marrow 0.12 Lung 0.12 Thyroid 0.03 Bone surfaces 0.03 Remainder 1 0.30 Whole Body 2 1.00 1 0.30 results from 0.06 for each of 5 “remainder” organs (excluding the skin and the lens of the eye) that receive the highest doses. 2 For the purpose of weighting the external whole body dose (for adding it to the internal dose), a single weighting factor, w T = 1.0, has been specified. The use of other weighting factors for external exposure will be approved on a case-by-case basis until such time as specific guidance is issued. Whole body means, for purposes of external exposure, head, trunk (including male gonads), arms above the elbow, or legs above the knee. Working level (WL) is any combination of short-lived radon daughters (for radon-222: polonium-218, lead-214, bismuth-214, and polonium-214; and for radon-220: polonium-216, lead-212, bismuth-212, and polonium-212) in 1 liter of air that will result in the ultimate emission of 1.3 × 10 5 MeV of potential alpha particle energy. Working level month (WLM) means an exposure to 1 working level for 170 hours (2,000 working hours per year/12 months per year = approximately 170 hours per month). Year means the period of time beginning in January used to determine compliance with the provisions of this part. The licensee may change the starting date of the year used to determine compliance by the licensee provided that the change is made at the beginning of the year and that no day is omitted or duplicated in consecutive years. [ 56 FR 23391 , May 21, 1991, as amended at 57 FR 57878 , Dec. 8, 1992; 58 FR 7736 , Feb. 9, 1993; 60 FR 36043 , July 13, 1995; 60 FR 48625 , Sept. 20, 1995; 61 FR 65127 , Dec. 10, 1996; 62 FR 4133 , Jan. 29, 1997; 62 FR 39087 , July 21, 1997; 63 FR 39481 , July 23, 1998; 64 FR 54556 , Oct. 7, 1999; 66 FR 55789 , Nov. 2, 2001; 67 FR 16304 ,