Document: NRC Regulatory Guide
Document ID: 96baa826-d3bb-478b-8f38-e74500f6d433
Document Type: regulatory_guide
Title: 06/2009 (Rev. 2)
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML0911/ML091170109.pdf
Revision Date: 2023-06
Chapter: 
Section ID: RG-1.21
CFR Part: 
CFR Title: 

Content:
re than twice the height of adjacent solid structures, or releases made from heights sufficiently above adjacent solid structures that building wake effects are minimal or absent. exposure pathway—A mechanism by which radioactive material is transferred from the (local) environment to humans. There are three commonly recognized exposure pathways; inhalation, ingestion, and direct radiation. For example, ingestion is an exposure pathway, and it may include dose contributions from one or more routes of exposure. For example, one route of exposure that may contribute to the ingestion exposure pathway is often referred to as grass-cow-milk-infant- thyroid route of exposure. ground-level release—A gaseous effluent release made from a height that is at—or less than—the height of adjacent solid structures, or where the degree of plume rise is unknown or is otherwise insufficient to avoid building wake effects. Rev. 2 of RG 1.21, Page 44 ground water—All water in the surface soil, the subsurface soil, or any other subsurface water. Ground water is simply water in the ground regardless of its quality, including saline, brackish, or fresh water. Ground water can be moisture in the ground that is above the regional water table in the unsaturated (or vadose) zone, or ground water can be at and below the water table in the saturated zone. hypothetical exposure pathway—An exposure pathway in which one or more of the components involved in the transfer of a radionuclide from the environment to the human does not actually exist at the specified location, or if a real human does not consume, inhale, or otherwise become exposed to the radioactive material. For example, the grass-cow-milk-infant-thyroid route of exposure (associated with the ingestion exposure pathway) would be considered a hypothetical exposure pathway if the grass, the cow, or the milk did not actually exist at a specified location or if an infant did not actually consume the milk. impacted areas—Means