Document: NRC Regulatory Guide
Document ID: 8b2255d1-47a9-4dfe-ba41-568c561a89ee
Document Type: regulatory_guide
Title: Inspection of Water-Control Structures Associated with Nuclear Power Plants + HISTORY – HISTORY 01/2015 – DG-1245 , Proposed Revision 2 (Rev. 2)
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML1325/ML13255A435.pdf
Revision Date: 2023-06
Chapter: 
Section ID: RG-1.127
CFR Part: 
CFR Title: 

Content:
kage of spillways, or settlement of the dam crest account for approximately 34 percent of all failures. 2. Foundation defects, including settlement and slope instability, cause about 30 percent of all failures. 3. Seepage around hydraulic structures (i.e., piping), such as pipes and spillways; through animal burrows; around roots of woody vegetation; and through cracks in dams, levees, and water control structures account for 20 percent of the failures. 4. The remaining 16 percent are the result of a variety of issues including structural failure, improper materials used in construction, and inadequate or improper maintenance. In many cases, periodic inspection and monitoring programs could have identified the precursor conditions in time to take corrective action and avert some of the failures. Pre-Decisional DG-1245, Page 4 Thorough physical examination is an essential part of the inspection and monitoring program. The optimal frequency of inspections depends on the size, age, and condition of the facilities; the character of the foundation; and the regional geological setting. The potential impact the failure of the water control structure would have on the nuclear power plant or the proximity of the structure to populated areas should also be considered when formulating inspection periodicity. The search for superficial signs of distress such as longitudinal and transverse cracks is only one phase of an inspection and monitoring program. Possible internal degradation may be probed by various portable instruments such as soniscopes, hydrophones, television, and borehole cameras. It is important that these observations be correlated closely with measurements from embedded devices, if available. Embankments placed against or covered by structures are particularly vulnerable areas that should be monitored. They may be susceptible to internal erosion at the planes of contact. Attention should also be focused on the slopes of the reservoir behind the dam or levee