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:
F 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. This result suggests that, for a nondecaying substance, the downstream concen tration reduction in lake plumes parallel to the shore is rather small. This is consistent with observations reported for several of the Great Lakes (Ref. 23). It should be kept in mind that the dilution calculated above is for the far field and does not include possible additional dilu tion arising from initial mixing in the near field. For a given location, the presence of a plume might be periodic. Therefore, long term average dilution factors can be estimated from the above model by multiplying the solution by an appropriate flow-field frequency function. Asdiscussed previously, observations suggest that the directional distribution of Great Lakes coastal currents is approximately bimodal. In such a case, long-term dilution factors would be about twice those calculated from Equatior (17). It is emphasized, however, that the presence of reversing currents at a given site should be demonstrated by field observations of flow patterns before credit is taken for concentration reduction attributable to intermittent plume behavior. (b) Transient Source Model For other than a continuous source, the transient form of the constituent trans port equation must be solved. In this case, diffusive transport in the direction of flow may be important, especially for short-duration releases, whereas it is unimportant in the case of con tinuous releases. For an instantaneous release of a finite quantity of material from a vertical line source at x a 0, y - ys9 Into a lake of known steady longshore current u, a simple transient model can be formulated: c. exp +,, \ , x + ex~p ,st /- (19) where d is the depth; M is the amount of activity released (in curies); t is the time after the release; and the other