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:
the longitudinal mixing, and Equation (39) is appropriate. 1.113-25 E(x~t) - 77nUtRh 5/6 (39) 5. IMPOUNDMENTS There are two basic types of cooling ponds. The first is a closed-loop system in which the thermal effluent is cooled in the pond and recirculated through the power plant condensers. Some water ("blowdown") must be removed from the pond to limit the dissolved solids concentration to an acceptable level. Fresh water ( make-up") must be added to the pond to compensate for evapo ration and blowdown. The second type of cooling pond is a flow-through system in which there is little or no recirculation of effluent through the power plant. The effluent is discharged to the pond which, In turn, discharges to a larger body of receiving water. The pond serves as a holding reservoir, allowing effluent to cool before entering the receiving water. The source of radionuclides may either be located on the impoundment or upstream on a tributary of the impoundment. For the simplest models, this distinction is irrelevant because concentration is based on flow through the impoundment and does not depend on the placement of the input. In the case of the upstream plant, the source term W is the rate of radionuclide entering with the flow at the boundary of the reservoir. Figure 6 illustrates a closed-loop cooling pond. Water for cooling is drawn through the intake, circulated through condensers, and returned to the pond via the discharge. There are two important hydrological parameters of this system. The first is the internal recirculation time constant associated with the flushing of the pond by the makeup and blowdown streams. The second is the time constant associated with the decay of radioisotopes. ;Figure 7 illustrates the flow-through pond. The hydraulics of this pond are simpler than the closed-loop pond, since no recirculation occurs between intake and discharge. In this case, the only hydraulic time constant is that associated with the travel time from the plant