Document: NRC Regulatory Guide
Document ID: a094549d-8685-4dad-b90f-c28c7d279a53
Document Type: regulatory_guide
Title: Geologic and Geotechnical Site Characterization Investigations for Nuclear Power Plants + HISTORY – HISTORY 08/2021 – DG-1392 , Proposed Revision 3 07/2014 – Periodic Review of Revision 2 – Reviewed with no issues identified 02/2001 – DG-1101 , Proposed Revision 2 (Rev. 3)
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML2119/ML21194A176.pdf
Revision Date: 2023-05
Chapter: 
Section ID: RG-1.132
CFR Part: 
CFR Title: 

Content:
y in rock, qualitative indication of changes of density in soils. May be run in empty or fluid-filled holes. Effects of borehole size and density of drilling fluid must be accounted for. Presently not suitable for qualitative estimate of density in soils other than those of rock-like character. Cannot be used in cased boreholes. Borehole cameras Film-type or television camera in a suitable protective container is used for observation of walls of borehole. Detection and mapping of joints, seams, cavities, or other visually observable features in rock. Can be used in empty uncased holes or in boreholes filled with clear water. Results are affected by any condition that impairs visibility. Borehole televiewer A rotating acoustic signal illuminates the borehole wall, and reflected signals are recorded. Detection and mapping of joints, seams, cavities, or other observable features in rock. Can be used in mud-filled boreholes. Transparency of borehole fluid is not essential. DG-1392, Appendix D, Page D-1 APPENDIX D SPACING AND DEPTH OF SUBSURFACE EXPLORATIONS FOR FOUNDATIONS OF SAFETY-RELATED1 ENGINEERED STRUCTURES STRUCTURE SPACING OF BORINGS2 OR SOUNDINGS MINIMUM DEPTH OF PENETRATION General For favorable, uniform geologic conditions, where continuity of subsurface strata is found, the recommended spacing is as indicated for the type of structure. At least three borings should be at locations within the footprint of every safety-related structure, unless other reliable information is available in the immediate vicinity or otherwise justifiable. Where variable conditions are found, spacing should be smaller, as needed, to obtain a clear picture of soil or rock properties and their variability. Where cavities or other discontinuities of engineering significance may occur, the normal exploratory work should be supplemented by borings or soundings at a spacing small enough to detect such features. The depth of borings should be determined on the basis of the type of