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:
proach, tidal currents are explicitly included as advective transport mechanisms. Leendertse and co-workers (Refs. 29-34) have shown that in this case, reasonable estimates of longitudinal and lateral turbulent dispersion coefficients may be based on Elder's (Ref. 19) formulas for steady open-channel flow. The applicability of numerical models and the techniques for establishing horizontal mixing coefficients are discussed further in Sections 4.c and 4.d. 1.113-16 4. ESTUARIES Transport of contaminants in estuaries differs from that in rivers because of oscillatory tidal advection and the nontidal gravitational circulation induced by salinity differences. An important consequence of.these differences is that there is transport of material upstream from the discharge point in estuaries, the maximum upstream penetration being limited to the general region of oceanic salt intrusion. a. One-Dimensional Models For purposes of radionuclide transport prediction, reduction of the estuarine problem to a single dimension (longitudinal) produces satisfactory results, except in the lower reaches of the estuary, where circulation is clearly two or three dimensional. The one-dimensional simpli fication Is accomplished by averaging over the estuary cross-section. The resulting constituent transport equation is katJAC) + -,-(AIC) -kfi"'AE4) XC (23) where ýA(x,t). is the cross-sectional area; E(x) ans the sectionally'averaged, one-dimensional longitudinal dispersion coefficient; and , , U(x,t) is the sectionally averaged longitudinal velocity. Both simple and elaborate methods of solving Equation (23) exist. The simplest models depend on the "tidally averaged" approximation, in which the tidal oscillations are not included explicitly, but are considered to be responsible for large-scale longitudinal diffusion. The more elaborate "real-time" models consider the actual tidal flow to be advective, with longitudinal-diffusion occurring through motions having time scales considerably