Document: NRC Regulatory Guide
Document ID: c9ebcbb0-96c4-4d29-be51-5acae9cc858a
Document Type: regulatory_guide
Title: Estimating Aquatic Dispersion of Effluents from Accidental and Routine Reactor Releases for the Purpose of Implementing Appendix I (Rev. 1)
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML0037/ML003740390.pdf
Revision Date: 2023-06
Chapter: 
Section ID: RG-1.113
CFR Part: 
CFR Title: 

Content:
ription are defined in the "List of Symbols" following the appendix. 1. INITIAL DILUTION Initial dilution of liquid radioactive effluents (e.g., dilution upon discharge to the receiving water body) is often accomplished by using relatively high-velocity surface or sub merged jets or multiport diffusers. Mathematical modeling of such discharges requires solution of the conservation equations applicable to buoyant jets. These equations are solved routinely as a part of the near-field analysis for thermal discharges. Initial dilution rates for water borne radionuclides should be obtained directly as an integral part of the thermal analysis. Applicable near-field models are In comnon usage throughout the industry and are not dis cussed in detail herein. Jirka et al. (Ref. 1) and Dunn et al. (Ref. 2) discuss in detail the theory and ranges of applicability of near-field models. These references should be consulted for guidance in determining the modeling approach to be used for a specific problem. General remarks on surface and submerged jet discharges are presented below. For surface discharges, acceptable initial dilution analyses may be obtained from the models of Stolzenbach and Harleman (Ref. 3), Stolzenbach et al. (Ref. 4), Prych (Ref. 5), Shirazi and Davis (Ref. 6), and Pritchard (Refs. 7 and 8). Dilution estimates for surface discharges require a careful assessment of the adverse effects of shoreline and bottom interference. Methods for estimating the magnitude of these boundary effects under given receiving water conditions are discussed in detail in Reference 1. Estimates of dilution from submerged discharges require careful analysis of the flow con ditions in the immediate vicinity of the discharge. The two possible flow conditions, stable o1% unstable, depend on the discharge and receiving water characteristics. Under stable conditions the discharge, upon reaching the free surface, spreads laterally in the form of a stable density current. As a result, there