Research On PWR Stainless Steel Cladding Weld Defects Detection In Pulsed Eddy Current Thermography Testing Technology

With the rapid development of China’s nuclear power industry, researchers are paying more and more attention to nuclear safety studies. As a significant barrier to stop the leak of highly radioactive material, the stainless steel cladding of pressurized water reactor is of great significance for nuclear safety. In China, during the construction phase of the nuclear power plant, the stainless steel cladding always present problems like pool leak, which is in stainless steel welds and the binding site, and this kind of problems also occur at the operation of the system. At present, there are some limitations in non-destructive testing methods for stainless steel weld defect detection. As a new non-destructive testing technology, the technology of pulsed eddy current thermography detection has many advantages, such as non-contact, high efficiency, single large area detection, etc., and this technology is widely arousing researchers’ attention at home and abroad.Based on the weld defect detection of pressurized stainless steel water reactor, this paper will make systematic study about the pulsed eddy current thermography detection technology through the methods of numerical simulation, experimental validation, experimental data processing. These study methods can achieve the effective detection of common stainless steel weld defects. The main contents are as follows:(1) Study the detection principle of the pulsed eddy current thermography testing technology. By introducing the pulsed eddy current thermography detection technology to detect defects on the surface and sub-surface, we can understand the working principle of the pulsed eddy current thermography detected. According to the relevant factors and existing experimental conditions, we will set up experimental platform, and make sure the rationality of the experimental platform by experimental verification.(2) Make numerical simulation of pulsed eddy current thermography detection to detect stainless steel weld defects. Simulate and analyze several common stainless steel weld defects detection by multi-physics simulation software COMSOL. Analyze and summarize the simulation results and defect detection features of sub-surface and surface crack defects, non-fusion defects, and porosity defects. By simulating and analyzing pulsed eddy current thermography detection to detect quantitative detection of stainless steel weld defects, provide theoretical support for the quantitative detection of defects in subsequent studies.(3) Study algorithm about thermal image data processing. Secondary heat balance method and normalization method are proposed to suppress the impact of uneven thermal emissivity. Processing the thermal image sequence data by Fourier transform thermal image processing method and thermal image sequences blind signal separation algorithm, we can extract useful information of the thermal entire response process, strengthen defect characteristics, and dig out more information about defects features. Contrast traditional pulsed eddy current testing technology by simulation。(4) Experiment and detect stainless steel weld artificial defects and natural defect. Artificial defects specimens are mainly used to evaluate pulsed eddy current thermography testing system for feasibility and sensitivity, and calibrate equipment. Natural defect specimens are mainly used to verify the accuracy of defect detection. Finally, there give some suggestions for improving the entire detection experiments, and provide a reference for subsequent further study.