Quantification of the Effective Detectable Period for Concrete Voids of CLP by Lock-In Thermography

Abstract

This study is to inspect the voids between the concrete containment building and the containment liner plate (CLP) in the light-water reactor type nuclear power plant with lock-in thermography (LIT) inspection technology. For that, a finite element method (FEM) model containing concrete voids was created, and the thermal distribution change of the CLP surface was simulated through numerical analysis simulation of various LIT inspection conditions and converted with real-time thermography data. For the simulated temperature distribution image and the amplitude and phase images calculated by the four-point method, the signal-to-noise ratio (SNR) is analyzed based on the sound area and void areas. As a result, the difference in SNR according to the size of voids was remarkable, and the effective detectable period (EDP), which was common to each inspection condition, was derived. Furthermore, a CLP concrete mockup identical to the model shape is produced, and the thermal image of the EDP is analyzed through the experiment with the same analysis technique, and the results are compared. Although there are some differences between the numerical analysis conditions and the experimental environments, the deduction and utilization of EDP through FEM simulation are considered useful approaches to applying LIT to inspect concrete voids on the back of the CLP.

Quantitative Investigation of Containment Liner Plate Thinning with Combined Thermal Wave Signal and Image Processing in Thermography Testing

“…LIT is a technology that simultaneously stimulates sinusoidal heat as a heat source across the entire surface of the object to be inspected and senses the IR signal emitted from the surface with an IR camera. Using sinusoidal waveforms results in the ability to preserve the shape and frequency, while the only deviation from the reference wave will be the magnitude and phase delay [23]. Defect detection is possible by demodulating this phase change and comparing and analyzing the difference between the sound area and the defective area.…”

Evaluation of Preferences for a Thermal-Camera-Based Abnormal Situation Detection Service via the Integrated Fuzzy AHP/TOPSIS Model

“…This indicates diverse thermography-based image analysis studies for preventing safety accidents in road and transportation. Some studies have also diagnosed buildings using thermal cameras, including detection of issues in building exteriors (e.g., corrosion of steel bars in concrete structures of buildings) [38,39] and diagnosis of thermal bridges in buildings [40][41][42][43][44]. In relation to HW, one study analyzed the effects of the performance and variability of thermal cameras on changes in the body surface temperature of horses [45].…”

Lateral Heat Distribution Characteristics of CLP S275 Using Gaussian FFT Algorithm in Optical Thermographic Testing

“…If corrosion occurs in the CLP, it progresses to a thinning defect. If maintenance is not carried out properly and thinning continues, it will eventually lead to breakage and cause significant damage [4]. For this reason, real-time maintenance of the CLP is essential.…”