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:
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 RADIONUCLIDE DISCHARGE AT THE SHORELINE vs DIMENSIONLESS DOWNSTREAM DISTANCE 1 10 6 Kx = ou*d, (13) where d is the river depth; u* is the shear velocity; and 0 is a dimensionless constant. (Again, the user is not restricted to the use of this formula. A number of alternative approaches have been published.) cor straight rectangular stream channels, o has a value of about 5.93. The value of s, however, increases in curved channels and in general must be determined by field studies (Refs. 20-22). The two-dimensional coefficient, Kx, is usually much smaller in magnitude than the one-dimensional coefficient, E, as described later. The usefulness of the transient model, even for simplified rectangular geometry, is that it allows analysis of the dispersion of material released In a realistic fashion. In the case of short-duration batch releases, spreading in the direction of flow may be an important. mechanism for effluent dispersion, which is not included in the steady-state continuous release model. 3. OPEN COASTS a. Great Lakes (1) Discussion Field studies in the Great Lakes have shown that coastal currents are predominantly parallel to the shore and have typical speeds of 10 to 20 cm/sec (0.2 to 0.4 knots). These cur rents usually persist in one direction for several days. Then, in direct response to wind shifts, they quickly reverse and persist in the opposite direction for several days. The stagnation time at reversal seldom exceeds a few hours (Refs. 23 and 24). The studies further suggest that each reversal of the coastal current is accompanied by a large-scale mass exchange with offshore waters that effectively removes pollutants from the shore zone. Possible physical mechanisms responsible for this behavior are discussed by Csanady (Refs. 25 and 26). Observations