Acoustic emissions (AE) and elastic wave (P-wave) velocities were measured on granite and marble under triaxial compression. The triaxial chamber capable of accommodating many AE sensors was made and transducer vessels measuring seismic wave velocities in axial and lateral direction simultaneously were devised. The measured AE parameters such as AE hit and amplitude were analyzed synthetically and quantitatively to determine the fracture process of rock. Moreover, AE source locating was carried out by considering the anisotropy and change of elastic wave velocity according to the applied stress state. The Kaiser effect was verified at constant confining pressure as well as at multistage confining pressures. Experimental MethodRock Specimen. Rock specimens used in the test were granites and marbles from Korea. Specimens were NX core of diameter 53-54 mm and length to diameter ratio was about 2. Both ends of specimens were ground parallel to within 0.02 mm and specimens were dried at 105°C before testing. Physical properties of rock specimens used in the test are shown in Table 1.Testing Method. Tests were carried out on a 200 ton capacity universal testing machine. Specimens were mounted in triaxial chamber as shown Fig. 1.Two strain gages and six AE sensors (Piezoelectric transducer, PZT) were attached to the specimen. Small size of the PZT allows many AE channels to be set in the limited space of triaxial chamber. The specimen was coated with silicon in order to prevent hydraulic oil penetrating the rock specimen. Signals from strain gages and PZT are transmitted from the chamber by plugs.

Steam generator (SG) tubes are pressure boundaries which separate the secondary unit from the primary one in nuclear power plants, so that they play a critical role in safe operation of nuclear power plants. Eddy current testing (ECT) is widely used in in-service inspection as well as pre-service inspection of the SG tubes. The interpretation of ECT signals, however, is truly a difficult task since ECT signals is changed not only by the flaws in SG tube but also by the variation in material properties such as conductivity and permeability. In the present work, the changes in ECT signals induced by the variation of the conductivity and the permeability of SG tube were simulated by using two dimensional electromagnetic finite element modeling. The results can be used for the discrimination of non-relevant ECT signals.