Document: NRC Regulatory Guide
Document ID: 42f2dcf0-38ba-4f75-84d4-e60f4bbf9162
Document Type: regulatory_guide
Title: Assessment of Abnormal Radionuclide Discharges in Ground Water to the Unrestricted Area at Nuclear Power Plant Sites Appendix-Simple Ground Water Model for Estimating Offsite Tritium Activity Flux + HISTORY - HISTORY 12/2015 – DG-4025-Proposed New Guide
Source: NRC Regulatory Guide Division 4
Source URL: https://www.nrc.gov/docs/ML1523/ML15237A388.pdf
Revision Date: 2023-06
Chapter: 
Section ID: RG-4.25
CFR Part: 
CFR Title: 

Content:
American Petroleum Institute (API) standards may be purchased through their Web site at: http://global.ihs.com/?RID=API1&MID=Q023 or by contacting API Headquarters at 1220 L Street, NW Washington, DC 20005-4070 USA Phone 202-682-8000, Web Site: http://www.api.org/ or E-Mail: standards@api.org. DG-4025, Appendix Page 1 APPENDIX Simple Ground Water Model for Estimating Offsite Tritium Activity Flux This appendix provides a simple ground-water flow and transport model for estimating offsite tritium (Hydrogen-3) activity flux at commercial nuclear power plant sites. This model is provided in a spreadsheet format to facilitate identification of model inputs and outputs, and is in ADAMS at Accession No. ML15086A566). The model building process is as follows: 1. Develop a conceptual site model for the site as specified in ANSI/ANS-2.17-10. 2. Assess the available site characterization and monitoring data to assist in constructing a transect (cross section) where the activity flux will be estimated. 3. Construct a series of transects between the monitoring wells normal to the approximate direction of ground water flow leaving the site. 4. Determine from the site characterization data how the hydrogeologic units can be represented. For example, is there layering in the soil and geologic media, and how variable are the properties within each hydrogeologic unit (e.g., (K) the hydraulic conductivity)? If so, discretize the transect to accommodate these variations and any hydrogeologic unit layering. If not, are the hydrogeologic units sufficiently uniform in material properties to represent them as separate units with uniform hydraulic properties (e.g., hydraulic conductivity (K) and hydraulic gradient (I) normal to the transect)? If so, represent the transect by a stack of blocks at each well location representing the layering at that location – each block will be the thickness of the layer that it represents. If not, discretize the transect to accommodate these variations