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:
ition), the evaluation should consider the magnitude of release originating as an elevated release and the magnitude of release originating as a ground-level release. For example, a close-in, downwind location in one sector may have a higher χ/Q (i.e., less dispersion) for a ground-level release; however, the majority of the source term may be originating as an elevated release, causing a higher concentration (χ) at a more distant location, possibly in a different sector. See Regulatory Guide 1.111 for a more complete discussion of release height. 3.4 Aquatic Dispersion (Surface Waters) Liquid radioactive effluents may be disposed in accordance with 10 CFR 20.2001, “General Requirements,” into a variety of receiving surface water bodies, including non-tidal rivers, lakes, reservoirs, settling ponds, cooling ponds, estuaries, and open coastal waters. This effluent is dispersed by various mechanisms (i.e., turbulent mixing, stream flow in the water bodies, and internal circulation or flow-through in lakes, reservoirs, and cooling ponds). Parameters influencing the dispersion patterns and concentrations near a site include the direction and speed of flow of currents, both natural and plant- induced, in the receiving water; the intensity of turbulent mixing; the size, geometry, and bottom topography of the receiving water; the location of effluent discharge in relation to the receiving water surface and shoreline; the amount of recirculation of previously discharged effluent; the characteristics of suspended and bottom sediments; and sediment sorption properties. Regulatory Guide 1.113, “Estimating Aquatic Dispersion of Effluents from Accidental and Routine Releases for the Purpose of Implementing Appendix I” (Ref. 30), describes calculational models for estimating aquatic dispersion to surface water Rev. 2 of RG 1.21, Page 21 bodies. However, the dispersion characteristics may be highly site dependent and local characteristics should be considered when