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:
It is seldom pos sible to obtain analytical solutions for time-dependent flow fields or for complex receiving water geometry. Consequently, any analytical solution should be carefully assessed by the applicant to ascertain the conditions under which the model might be a valid predictive tool. Simplified models do not necessarily produce conservative results. If such models are used, it is the applicant's responsibility to demonstrate their degree of conservatism. The staff's position on such demonstration is presented in Section C of this guide. In identifying liquid pathways to man, applicants should identify the location of water users, the types of uses, and the usage estimated out to a distance of 50 miles from the site. Because of high usage rates along many streams and estuaries, the effects of water usage on the spatial and temporal distribution of flows should be estimated. In addition, water usage up stream of a nuclear plant can alter flows at or downstream of the plant. This guide presents an acceptable methodology for evaluating water usage and the consequences thereof on streams and estuaries receiving routine or accidental releases of radionuclides from nuclear power plants. The ability of suspended and bottom sediments to absorb and adsorb radioactive nuclides from solution, thereby concentrating otherwise dilute species of ions, may create a significant pathway to man. Sorption by sediment is also an important mechanism for reducing the area of influence of plant releases. Unfortunately, the state of the art in evaluating sediment-related effects is less advanced than in other engineering disciplines. Consequently, the transport models discussed in this guide do not explicitly include sediment uptake mechanisms. Until reliable generalized sediment uptake and transport models become available, the NRC staff will rely on existing field studies and the staff's and consultants' experience to determine the level of conservatism or realism of the