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:
lly to the surface, with drawal is from the hypolimnion, and vertical gradients are more pronounced than horizontal gradients. These models are less accurate for reservoirs that have seasonal turnover and subse quent unstratified periods. Furthermore, these models are incapabl.e of simulating certain impor tant effects, such as horizontal mixing in the vicinity of a power plant discharge. 1.113-38 TinO.1 vr- 10 CSS"C° 0 i+1n2 T f-Iwtef4If9tmhI time) Vt 0 0.2 0.4 0.6 0.8 1.0 1.2 1.6 1.8 2.0 TIME/FLUSHING TIME 9 FIGURE 14. BUILDUP OF RADIOISOTOPES IN COMPLETELY MIXED MODEL (NORMALIZED) K 1.0 (AD LAP 0.6 0.4 F .4 0.2 0 ,r- 0.1 wP 4 LL 0 VT U wA :I- 2 2 01 1 i tf 11 lg-.1-312 10-1 1 10, ()210 HALF-LIFE/FLUSHING TIME FIGURE 15. DIMENSIONLESS TIME TO REACH 99% OF STEADY-SATE CONCENTRATION 1t4 COMPLýETELY MIXED CASE .J£ or ( Where both vertical and horizontal effects are important, more complicated models are war Anted. For example, the EPA Reservoir Model (Ref. 58) allows for the horizontal segmentation "_6f the reservoir. Each reservoir segment is solved in the vertical direction. Inputs from upstream and downstream segments are coupled empirically to account for density flows. Another useful model is the reservoir model of Ryan and Harleman (Ref. 59). In this model, the one-dimensional horizontal solution in the surface layer is coupled with a one-dimensional solution in the vertical direction. Effects of discharge mixing, surface cooling, and lateral gradients are calculated in the surface layer solution. Vertically stratified flows and selec tive withdrawals are handled by the vertical solution. The model is most useful for cooling reservoirs where stratification is strong. 6. WATER USE For identifying liquid pathways to man for realistic evaluations of the doses from normal releases from nuclear power plants, it is necessary to locate water users, identify types of uses, and estimate usage to a distance of 50 miles from a site. Because of high usage rates along