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:
ensionless cumulative discharge; i x/ý is the dimensionless concentration relative to the fully mixed value; and i - is the dimensionless downstream distance. The utility of the dimensionless form is illustrated in Figure 2, which shows near and far-shore concentrations resulting from a near-shore point discharge. For a given downstream location and given flow parameters, the dimensionless concentration for either shoreline may be obtained directly from the two curves. The near-shore concentration exhibits the expected x"1/2 dependence for two-dimensional mixing until the influence of the far shore if felt. Both curves in Figure 2 approach unity (complete sectional mixing) for large values of x. Hence, for a given set of flow parameters, the downstream distance to sectional homogeneity ("mixing distance") can be estimated directly. (Note that the mixing distance for a shoreline discharge is four times the mixing distance for a centerline discharge.) (2) Transient Release Model The transient release model is formulated in this guide only for the case of a vertical line source in a straight rectangular channel, since Its primary purpose Is to furnish informa tion on the time-dependent behav or of non-continuous releases. However, the model can be extended to treat other source configurations in stream tube coordinates as employed in Section 2.a.(l) of this appendix. Application'of the model requires the determination of the longitudinal turbulent dif fusion coefficient Kx, in addition to the parameters necessary for the steady-state model in the previous section. The longitudinal dispersion coefficient should be obtained by site-specific tracer experiments. However, crude estimates of Kx may be obtained from the following formula, which is similar to that for the lateral diffusion coefficient (Ref. 19): 1.113-9 10 z 0 z 00 z _U o . 10- t! w / w F/ io-1 I ,t 10-4 10-3 I0- 2 IV-1 DIMENSIONLESS DOWNSTREAM DISTANCE . D FIGURE 2. DIMENSIONLESS CONCENTRATION OF NONDECAYING