Document: NRC Regulatory Guide
Document ID: 96baa826-d3bb-478b-8f38-e74500f6d433
Document Type: regulatory_guide
Title: 06/2009 (Rev. 2)
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML0911/ML091170109.pdf
Revision Date: 2023-06
Chapter: 
Section ID: RG-1.21
CFR Part: 
CFR Title: 

Content:
lly reach the local water table. The dispersion of this material depends on the local subsurface geology and hydrogeologic characteristics. Liquid releases into the subsurface will be transported as a function of ground water flow processes and conditions (e.g., hydraulic gradients, permeability, porosity, and geochemical processes) and will eventually be released to the unrestricted area. A ground water site conceptual model should be developed to predict the subsurface water flow parameters to include direction and rate and to be used as the basis for estimating the dispersion of abnormal releases of liquid effluents into ground water (see Regulatory Guide 4.1). References that can be used in developing an adequate ground water site conceptual model include the following: 1. ANSI/American Nuclear Society (ANS) 2.17, “Evaluation of Subsurface Radionuclide Transport at Commercial Nuclear Power Production Facilities” (Ref. 31); 2. NUREG/CR-6948, “Integrated Ground-Water Monitoring Strategy for NRC-Licensed Facilities and Sites,” issued November 2007 (Ref. 32); and 3. Electric Power Research Institute (EPRI) Report No. 1011730, “Ground Water Monitoring Guidance for Nuclear Power Plants, issued September 2005 (Ref. 33). 4. NUREG/CR-6805, “A Comprehensive Strategy of Hydrogeology Modeling and Uncertainty Analysis for Nuclear Facilities and Sites,” July, 2003 (Ref 54). 5. EPRI Report No. 1015118, “Ground Water Protection Guidelines for Nuclear Power Plants,” Electric Power Research Institute, Palo Alto, CA, November 2007 (Ref 34). Simple analytical models or more rigorous numerical codes (i.e., simulations) may be used to evaluate subsurface transport following a release. These models and codes will depend on the release rate, Rev. 2 of RG 1.21, Page 22 depth of the release, depth to the local water table, ground water flow directions, ground water flow rates, geochemical conditions, and other geochemical processes (e.g., geochemical retardation).