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:
that will be exposed to normal releases of radionuclides within 50 radial miles of a plant should be identified. Present and projected future contact by humans and fish should be estimated. The use of river system simulation models such as HEC-3 to adjust historic streamflows and to synthesize existing and potential future water use can provide acceptable estimates of the spatial and temporal distributions of streamflows at the locations for which estimates of average radionuclide concentrations are required. Two basic assumptions are required. First, it is assumed that the period of recorded historical streamflow selected for simulation is representa tive of conditions to be expected in the future. Secondly, it is assumed that it is necessary to adjust historical streamflows for the effects of reservoirs and diversions. If both of these assumptions are not supported by historical basin water usage, no adjustments are necessary. Furthermore, if projected water use cannot be expected to alter streamflows in a way such as to require basin simulation, no flow adjustments are necessary. Water use should be estimated, on a monthly basis, for present and projected future con ditions. Local, state, or regional agencies often maintain records of such use, and such infor mation should be summarized and appropriately annotated. These same agencies have in many cases made projections of future usage; these projections should be summarized and annotated. Where existing records or locally projected usage information is not available or is con sidered unreliable, conservative estimates may be made from population projections and forecasted per capita usage estimates of agencies such as the U.S. Geological Survey or the Water Resources Council. Where population or water use forecasts are at variance with other forecasts submitted by the applicant, the bases for the differences should be provided. Although conservative estimates are sometimes required to ensure that the