radguide

29 Radiation for Radionuclide Users Regulatory Limits for Occupational Exposure Many of the recommendations of the ICRP and other radiation protection groups regarding radiation exposure have been incorporated into regulatory requirements by various countries. In the United States, the annual radiation exposure limits are found in Title 10, Part 20 of the Code of Federal Regulations (10CFR20), or equivalent state regulations. These limits are based on external, internal, and external plus internal exposures. To better understand the annual occupational exposure limits set by the appropriate regulatory agency, the definitions of these limits need to be discussed. These definitions are presented in this section. External Dose Shallow-Dose Equivalent (SDE) is the external dose to the skin of the whole-body or extremity from an external source of radioactive material. This value is the dose equivalent at a tissue depth of 0.007 cm. (7 mg/cm2) averaged over an area of 1 cm 2. Eye Dose Equivalent (LDE) is the dose equivalent to the lens of the eye from an external source of radioactive material. This value is the dose equivalent at a tissue depth of 0.3 cm. (300 mg/cm 2 ). Deep-Dose Equivalent (DDE) is the external whole-body dose from an external source of radioactive material. This value is the dose equivalent at a tissue depth of 1 cm. (1000 mg/cm 2 ). Internal Dose Committed Dose Equivalent (CDE) is the dose equivalent to organs or tissue that will be received from an intake of radioactive material. Committed Effective Dose Equivalent (CEDE) is the dose equivalent for the whole-body from an intake of radioactive material. External Plus Internal Dose Total Organ Dose Equivalent (TODE) is the dose equivalent to the maximally exposed organ or tissue from external and internal sources of radioactive material combined. TODE = DDE + CDE Total Effective Dose Equivalent (TEDE) is the dose equivalent to the whole-body from the combination of external and internal sources of radioactive material. TEDE = DDE + CEDE