Document: NRC Regulatory Guide
Document ID: f4c5fb1d-efb9-4168-9804-5ad3f6f64d06
Document Type: regulatory_guide
Title: Reporting Procedure for Mathematical Models Selected To Predict Heated Effluent Dispersion in Natural Water Bodies
Source: NRC Regulatory Guide Division 4
Source URL: https://www.nrc.gov/docs/ML0037/ML003739535.pdf
Revision Date: 2023-06
Chapter: 
Section ID: RG-4.4
CFR Part: 
CFR Title: 

Content:
type tend to produce thin surface plumes of large areal extent, which are efficient in transferring heat to the stniosphre. Currently, many discharge structures are being designed to maximize dilution near the outfall while minimizing detectable surface plume area in the far-field. The result has been submerged structures with *Wge or multiple high-velocity exit ports. Outfalls of this type are called diffusers, and they utilize a high discharge velocity to produce intensive mechanical mixing in the near-field. Details of engineering design for outfall structures ame generally unnecessary for thermal discharge modeling problems. However, consideration must be given to outfall geometry, that is, the size and shape of the exit port(s) or canal and its location and orientation relative to some fixed coordinate system. The choice of coordinate system is arbitrary, but a system is usually selected that simplifies the mathematics of the model. In addition to outfall geometry, several oth-r plant design factors must be known for modleling purposes. These include the heat rejection rate, temperature rise of the discharge relative to the Intake, the volumetric flow rate of cooling water, and the initial discharge velocity. If not directly measurable, the discharge velocity can be estimated from the volumetric flow rate and the exit port cross-sectional area and orientation. 3. Environmental Factors Governing Thermal Diprso Thiree factors or physical processes govern the thermal dispersion of heated effluents in natural environments: "* entrainment "* turbulent diffusion "* surface heat exchange Advection is another major process that directly influenrces tin size, shape, and distribution of heated effluents. The interactive Woe played by advective phenomena such as nilent currents Is discussed below, but only to the extent that advection affects dispersion proceses a.Esiralninnet Consider first the hypothetical case of a nonbuoyant discharge into a stagnant homogeneous