Phased Array Ultrasonic Inspection Technique for Cast Austenitic Stainless Steel Parts of Nuclear Power Plants

Abstract

For safety operation of nuclear power plants, soundness assurance of structures has been strongly required. In order to evaluate properties of inner defects at plant structures quantitatively, non-destructive inspection using ultrasonic testing (UT) has performed an important role for plant maintenances. At nuclear power plants, there are many structures made of cast austenitic stainless steel (e.g. casings, valve gages, pipes and so on). However, UT has not achieved enough accuracy measurement at cast stainless steels due to the noise from large grains. In order to overcome the problem, we have developed comprehensively analyzable phased array ultrasonic testing (PAUT) system. We have been noticing that dependency of echo intensity from defect is different from grain noises when PAUT conditions (for example, ultrasonic incident angles and focal depths) were continuously changed. Analyzing the tendency of echoes from comprehensive PAUT conditions, defect echoes could be distinguished from the noises. Meanwhile, in order to minimize the inspection time on-site, we have developed the algorithms and the full matrix capture (FMC) data acquisition system. In this paper, the authors confirmed the detectability of the PAUT system applying cast austenitic stainless steel (316 stainless steel) specimens which have sand-blasted surface and 3 slits which made by electric discharge machining (EDM).

Development of a 16-Channel Broadband Piezoelectric Micro Ultrasonic Transducer Array Probe for Pipeline Butt-Welded Defect Detection

“…In 2009, Li et al developed an ultrasonic phased array system for automatic flaw detection of the pipeline girth welds [ 27 ]. In 2016, Yamamoto et al developed a phased-array ultrasonic inspection system (PAUT) with a 2 MHz, 128-element array probe, which can inspect cast austenitic stainless steel parts in nuclear power plants and distinguish defect echoes from the noises, offering slit sizing error of less than 2 mm [ 28 ]. In 2019, Fu et al designed a 2.5 MHz 64-element binary matrix array probe and a 2.25 MHz 64-element single-wire array probe to detect defects in the stub butt welds of the China Fusion Engineering Testing Reactor (CFETR) vacuum vessel (VV) body and port, achieving width detection sensitivity of 0.2 mm [ 29 ].…”

Compact Multi-Element Ultrasonic Transducer for Inspecting Split Pins in Nuclear Power Plants

“…Trampus (Trampus, 2019) adopted a smart phase array UT probe to detect radial fatigue cracks in a nozzle radius. Yamamoto et al (Yamamoto et al, 2016) developed a phased array ultrasonic inspection technique for monitoring cast austenitic stainless steel parts in nuclear power plants. Fu et al (Fu et al, 2019) designed a 2.5 MHz 64 el dual-element matrix array probe and a 2.25 MHz 64 el single-linear array probe for the inspection of vertical defects in the butt-joint welds of CFETR vacuum vessel port stubs.…”

Evaluation of Interface Defects in Inaccessible Reactor Shrink Fit Nozzle Welds Using Ultrasonic Waves

“…However, achieving the purpose of online monitoring for nuclear power plant components still has a long way to go. Recently, PAUT was employed for precise defect detection and sizing [2]. Nuclear power plant components inspection by LRUT such as nuclear power plant valves [3,4], pipes [5][6][7][8][9][10] and steam generator tubes [11][12][13][14] has been reported.…”