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:
Y-STATE CONCENTRATIONS IN COMPLETELY MIXED AND PLUG-FLOW MODELS \I- K hi 0 lF u z ur-l . . . ..... | Evaporation - I - Malmuo I". % + Evapoation Concetrt~OionC =1CJO BtOwdOwn Out - Q Concentrationl -C travel' time V 'lb FIGUIA2 10. PLUG-FLOW MODEL 1 .113-32 K t - 7ý2; Makeup In - % + Evaporation Cl Concentmion - 0 w C3 -C 2 + BIowdoam Out a %b Conicenmitaon -C 2 Plant Pumpin Raw % FIGURE 111. PARTIALLY MIXED MODEL 1.113-33 J2 +(47) Figure 12 shows the relative concentration C/Co as a function of T and R. Notice that K the asymptotic forms of Equation (47) for R - 0 reduce to the completely mixed case: C T ( 5 -C ___T" and for R = to the plug-flow case: C exp ( - ln2/r) (46) (4) Stratified Reservoir Lumped Parameter Model A simple model based on an approach of Trent (Ref. 56) is useful for a gross approxi mation of the mixing processes in stratified reservoirs that have seasonal turnover. The lake is assumed to have two layers, each totally mixed (Figure 13). Water can flow into and be withdrawn from either layer, but the layers do'not mix during stratified flow periods.- The volume of each layer is assumed constant during the period of stratification or during unstratified floo. Turn over is assumed to mix the two layers-totally and instantaneously. This assumption is reasonable for systems in which the turnover-time is small compared to the residence time. Input data needed for this model are as follows: Stratified Period 1. Length of stratified period 2. Volume of epilimnion and hypolimnion (constant over period) 3. Inflow and withdrawal (same), aither'layer 4. Concentration in inflow 5. Half-life of constituent Unstratified Period 1. Length of unstratified period 2. Total volume of reservoir (constant over period) 3. Inflow and withdrawal (same) 4. Concentration in inflow 5. Half-life of constituent The model is initialized with concentration C(o) at time t 0 0. The first period, (O<t<t,), corresponds to stratified conditions. Concentration in the epilimnion