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:
tant but much more difficult to quantify, Is the influence of meteorological driving forces. These forces include the direct effects of both meso-scale and synoptic-scale wind systems and the indirect effects of seasonal variations in heating or cooling and coastal river discharges. As a result of these factors, the flow variability in oceanic coastal waters contains components having magnitudes and characteristic time scales greater than those of the near-shore waters of the Great Lakes. In practice, the choice of transport modeling techniques applicable to a given ocean coastal region depends, to a large extent, on the level of knowledge of local near-shore current climatology. A particular model choice and range of model parameters should be demonstrated to include, to the extent practical, the effects of the important scales of flow variability. For synoptic scale fluctuations in flow patterns, it will often be necessary to perform transport calculations for conditions "typical" of various seasons or wind patterns. For a given set of conditions, however, the choice of modeling techniques is further deter mined by the interpretation of the role of tidal currents in the mixing process. The interpre tation depends on the averaging period used to define the velocity field. If the averaging time is long compared to the tidal period, tidal currents cannot contribute to the advective trans port, since their contributions to the mean flow field have been removed by the averaging. Tidal effects would be contained solely in "tidally averaged" turbulent diffusion coefficients. This result is largely a mathematical artifact that assigns the actual advective effects of tidal currents to large-scale turbulent diffusion. Nevertheless, if detailed descriptions of the field of radionuclide concentrations are not required, it is possible to construct quasi steady-state transport models that are valid for time scales larger than the tidal period and smaller than those associated