Abstract
Polyethylene (PE) pipe, particularly high-density polyethylene (HDPE) pipe, has been successfully utilized to transport cooling water for both non-safety- and safety-related applications in nuclear power plant (NPP). Though ASME Code Case N755, which is the first code case related to NPP HDPE pipe, requires a thorough nondestructive examination (NDE) of HDPE joints. However, no executable regulations presently exist because of the lack of a feasible NDE technique for HDPE pipe in NPP. This work presents a review of current developments in NDE technology for both HDPE pipe in NPP with a diameter of less than 400 mm and that of a larger size. For the former category, phased array ultrasonic technique is proven effective for inspecting typical defects in HDPE pipe, and is thus used in Chinese national standards GB/T 29460 and GB/T 29461. A defect-recognition technique is developed based on pattern recognition, and a safety assessment principle is summarized from the database of destructive testing. On the other hand, recent research and practical studies reveal that in current ultrasonic-inspection technology, the absence of effective ultrasonic inspection for large size was lack of consideration of the viscoelasticity effect of PE on acoustic wave propagation in current ultrasonic inspection technology. Furthermore, main technical problems were analyzed in the paper to achieve an effective ultrasonic test method in accordance to the safety and efficiency requirements of related regulations and standards. Finally, the development trend and challenges of NDE test technology for HDPE in NPP are discussed.
Highlights
Most of Chinese mainland’s electricity is produced from fossil fuels, predominantly coal
Lack of reliable nondestructive examination (NDE) method is the main barrier for ensuring the long-term safety of High density polyethylene (HDPE) pipe in nuclear power plant (NPP)
This paper reviewed current development in nondestructive test technology for PE pipe, and the main conclusions are drawn as follows: 1) Phased array ultrasonic inspection technique exhibits great advantages for the detection of all typical defects in both EF joints and butt fusion (BF) joints, especially for cold welding
Summary
Most of Chinese mainland’s electricity is produced from fossil fuels, predominantly coal. Nuclear power in China is under vigorous development due to its excellent advantages of high input-output energy ratio, low pollution emission, and long operation life [1]. Metallic piping, such as carbon steel piping, is historically the most commonly used piping for pressurized cooling water transportation. N-755 requires that visual examination, hydrostatic test, and nondestructive examination (NDE) shall be conducted on all pipe fusion joints before operation [7]. The existing ultrasonic testing technology encountered new challenges and obstacles when it was applied for inspecting PE pipe joint of a larger diameter in NPP. Prospects of NDE technology development for PE pipe in NPP were further discussed
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