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:
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 is little re-entrainment of previously discharged water. Such stable discharges can be characterized as "deep-water." Unstable or "shallow-water" discharges are characterized by counterflow which causes re-entrainment of previously mixed effluent into the discharge jet. Application of deep-water jet models to shallow-water discharges can result in serious overestimation of initial dilution. References 1, 9, and 10 discuss in detail the behavior of stable and unstable discharges and stability criteria for various types of submerged discharges. In practice, the results of a stability analysis will determine whether a "deep water" or "shallow-water" model should be used for a given discharge-receiving water system. For deep-water (stable) conditions the commonly used submerged Jet models of Koh and Fan (Ref. 11) and Hirst (Ref. 12) and similar models are applicable provided the thickness of the buoyant surface layer is taken Into account. For shallow-water (unstable) conditions the above models (and other similar deep-water models) are not applicable and their use will result in predicting excessively high dilution. The models of Lee et al. (Ref. 10) and Jirka and Harleman (Ref. 9), with appropriate stability analyses, are directly applicable to either deep- or shallow-water discharges. 2. NONTIDAL RIVERS a. Model Formulations (1) Steady-State Stream Tube Model Application of the models herein is restricted to those portions of the river removed from influences of the discharge. Initial dilution near the point of discharge is usually con trolled by turbulent mixing induced by momentum effects of the discharge jet. Techniques for the determination of initial dilution were discussed in Section 1 of this appendix. 1.113-4 For nontidal rivers the flow is assumed to be uniform