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This thesis presents a multi-purpose sensor concept viable for the simultaneous measurement of pressure, temperature and thickness of plate structures. It also establishes the knowledge base necessary for future sensor design. Thermal-Acousto Photonic Non-Destructive Evaluation (TAP-NDE) is employed to remotely initiate and acquire interrogating ultrasonic waves. Parameters including pressure, temperature and plate thickness are determined through exploring the dispersion features of the interrogating waves. A theoretical study is performed, through which a modified wave propagation theory applicable to homogeneous, isotropic, linear elastic materials is formulated along with an associated numerical model. A numerical scheme for solving the model is also developed using FEMLAB, a finite element based PDE solver. Gabor Wavelet Transform (GWT) is employed to map numerical time waveforms into the joint time-frequency domain. Wave time-frequency information enables dispersion curves to be extracted and material pressure, temperature and thickness to be determined. A sensor configuration design integrating the wave generation and sensing components of the proven TAP-NDE technology is also developed. Conclusions of the research are drawn from wave dispersion obtained corresponding to the following ranges of parameters: 300-500kHz for frequency, 25-300oC for temperature, 1-3mm for plate thickness, and 6 10 1?? - 7 1 10 ?? N/m for pressure. Each of the three parameters considered in the study has a different level of impact on plate wave dispersion. Plate thickness is found to have the most impact on wave dispersion, followed by temperature of the plate. The effect attributable to pressure is the least prominent among the three parameters considered. Plate thickness and temperature can be readily measured while simultaneously resolved using dispersion curves. However, pressure variation can only be differentiated when the plate is smaller than 1mm in thickness. It is observed that the thicker the plate, the faster the frequency group velocity. Also, the group velocities of all frequency components considered are seen to increase with increasing temperature, but decrease with increasing pressure.

In recent years, the desperate need for reliable clean and relatively small power demand has emerged for edge-of-grid or off-grid regions to keep pace with development demands. A salient technology that has gained much attention for this purpose is the Small Modular Reactors, i.e., SMRs. SMRs differ from conventional Nuclear Power Plants (NPPs) in many aspects, specifically the enclosing structure of the reactor. The burial depth of the SMR structure is expected to reach great depths. For example, the substructure depth reaches 30 m in the SMR design proposed by NuScale (NuScale Power, 2020). Consequently, seismic analysis of deeply embedded structures with a relatively small footprint has been identified as one of the challenges to the safe implementation of SMR technology (DIS-16-04, 2016). Such structures are expected to be more sensitive to surface wave propagation and the seismic interaction with nearby substructures and nonstructural elements such as pipelines. This dissertation develops analytical and numerical methods to analyze the seismic earth pressure exerted on the SMR substructure by considering the effects of seismic surface waves, structure-soil-structure interaction (SSSI), and the interaction with nearby pipelines. The three-dimensional wave propagation theory is employed in the analysis. Solutions for the earth pressure induced by Rayleigh waves are obtained for substructures deeply embedded into homogeneous or multilayered soil profiles. In addition, the effect of thin soil layer (stiff or soft) soils in a soil profile is investigated in the presence of Rayleigh waves. Furthermore, additional earth pressure due to SSSI is examined, and a simplified procedure is proposed based on the three-dimensional wave propagation theory and a guided flow chart to track seismic wave interference. The SSSI analysis yields solutions for the optimal distance between substructures corresponding to the minimum SSSI in new designs. The interaction between substructures and nearby pipelines is explored numerically using the Spectral Element Method. SPECFEM2D software is adopted to perform the analysis, where the three-dimensional wave propagation is successfully implemented. Based on the analysis for pipelines with different configurations, general conclusions are drawn regarding the additional earth pressure on substructures and pipelines based on a comprehensive parametric study of various parameters. In addition, this research also provides an approach to determine the backfill configuration and the selection of backfill materials, which could minimize the seismic amplitudes transmitted to substructures. / Thesis / Doctor of Philosophy (PhD) / Small Modular Reactors (SMRs) are the cornerstone of recent developments in the nuclear industry. However, the SMRs technology faces several safety-related challenges, which includes the earthquake hazards related to the large embedment depth of the enclosing structure. In particular, the major concerns are about the risks related to seismic surface waves as well as the seismic interaction between nearby structural and non-structural elements (e.g., pipelines). The thesis addressed these major concerns by developing analytical and numerical methods to complement the analysis for the integrity of SMRs with sufficient seismic resistance. The solutions are verified and benchmarked using data in the literature. Future researches are suggested to further improve seismic analysis of SMRs.