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:
nto bounded water bodies. For the sake of simplicity, the present discussion is limited to point discharges. However, If W is interpreted as source strength per unit length, or per unit area, line and plane sources, respectively, may be treated by integration of Equation (17) over the source dimensions. The predictive capabilities of this model are limited because of the spatial variations in the flow field under actual conditions and because there are large uncertainties in the diffusion coefficients Cy and ez (or. equivalently, n. the standard deviations ay and az). Studies in the Great Lakes and other large lakes suggest that "representative" near-shore values of ey are roughly in the range of 500 to 1000 Cm 2/sec (0.5 to 1.1 ft 2/sec) and that cz is in the range 1 to 30 cm2/sec (0.001 to 0.030 ft 2/sec) (Refs. 23 and 28). These values are typical only 1.113-12 of the near-shore zone. Furthermore, there is evidence to suggest that the C is reasonahly cnn stant for discharge plume widths exceeding about 50m (- 165 ft) (Ref. 23). Pence Richardson's "four-thirds power law" should not be used to describe the lateral diffusion coefficient without justification on the basis of site-specific tracer studies. Figure 3 shows centerline and shoreline values of x/W calculated from Equation (17) for the case of a point source discharging at the surface 500 m (1640 ft) offshore into a 10 cm/sec (0.3 ft/sec) current. The horizontal and vertical mixing coefficients are 1000 cm2/sec I (1.1 ft 2/sec) and 5 cm2/sec (0.005 ft 2/sec), respectively. The depth is 10 m. The centerline concentrations decrease inversely with distance from the source, x-1, for about the first 10 km (6 miles), beyond which the concentration decrease is approximately x-1/2. The dilution factor, DF, is given by DF W/(xq) (18) where qp is the volumetric discharge rate of the effluent. The dilution factor, for example, at 10 km (6 miles) downcurrent is approximately 7 for a 52 m3/sec (1,830 ft 3/sec) discharge.