Significance of Acoustic and Electrical Logging Studies at Nuclear Power Plants

Extensive geotechnical investigations are carried out for designing crucial structures of a nuclear power plant (NPP). As these structures enforce heavy loads on the foundation, it is imperative to evaluate the properties of subsurface rocks up to sufficient depth to ensure the plant’s safety. A primary requirement for design of nuclear power plants is they withstand dynamic loads up to a predefined intensity of ground motion, without endangering their safety. The properties of foundation materials are therefore of paramount importance as they can affect the structural safety. It is here, where in addition to surface geophysical techniques, electrical and acoustic borehole geophysical logging techniques play a major role in assessing the suitability of foundation. The subsurface parameters evaluated from these studies include electrical resistivity, primary and shear wave velocities, and dynamic moduli of elasticity which form the basis of deriving the input design values for the structure. Additionally, these methods also determine the location of weak zones. This paper highlights the importance of borehole geophysical logging in assessing the foundation for NPP with two CWPRS case studies, where suitability of foundation critical structures was determined.