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:
ments are known constants. This is the most realistic assumption for this model, pro vided the model is extended to the headwaters of the estuary and to the ocean. In practice, the model can easily be extended from the headwaters to the ocean by fine grid spacing in the area near the discharge and by coarse spacing farther away--in the regions of less interest. 1.113-20 A useful application of this model occurs where there are recycle streams such as municipal water withdrawal and return. The recirculation with partial or total removal of cer tain radionuclides could be important for heavily used tidal and nontidal waterways. (4) Intratidal Numerical Models The tidally averaged models are often subject to error because of uncertainty in the longitudinal dispersion coefficient. A more acceptable approach is the intratidal model, in which velocity, water level, and concentration in the estuary are simultaneously solved for, the tidal velocity being retained explicitly as an advective transport mechanism. In such a model, the longitudinal diffusion coefficient is better defined on the basis of physical princi ples and is less important than in the tidally averaged case. The model solutions are suitable for digital computation and do not require excessive computer resources. Included are models such as the Dailey-Harleman (Ref. 49) one-dimensional finite element model, the Lee-Harleman (Ref. 50) finite difference model, and the Eraslan (Ref. 51) one-dimensional donor cell model. Basically, these models solve the one-dimensional equations of mass, momentum, and constituent conservation, 8 a Source - 0 (32) ax + + + g3 + 0 (33) 1a + __ Ia aC -. _(A-P-)- XC(34) aax(AC axi7 ax where b is the width of the estuary at the water surface; Ch is the Chezy coefficient; Rh is the hydraulic radius; and C is the water surface location above an undisturbed level datum. Concentration boundary conditions can be treated realistically in the intratidal formu lation. The upstream boundary