Stress Distribution and Safety Evaluation of Pipeline in Ice Plug of Nuclear Power

Effect of Cyclic Ice Plug Deformation on Microstructure and Mechanical Behaviors of Nuclear-Grade Low-Carbon Tubular Steel

“…Here, an outer jacket device is fixed at a chosen position on the pipe's outer surface, serving as a reservoir for storing the refrigerant (liquid nitrogen) during the ice plugging procedure. When liquid nitrogen is introduced into the annulus surrounding the pipe, it exchanges heat with the liquid medium (water) inside the pipe, causing the water to cool and freeze from the pipe wall radially inward, eventually forming an ice plug capable of withstanding a certain pressure to block the pipe and isolate upstream and downstream maintenance equipment [6,9]. The formation of the ice plug primarily involves two stages: firstly, the heat transfer process between the media on either side of the pipe wall; secondly, the phase transition process wherein the water inside the pipe wall freezes when its temperature drops below 0 • C. During the ice plug test, the stress variation in the pipe wall is monitored using a cryogenic strain gauge and a stress-strain tester.…”

“…Ice plugging technology involves the localized cooling of a system pipeline requiring isolation using refrigerants, such as liquid nitrogen or dry ice, causing the liquid medium within that segment to freeze, forming a stable ice plug within the pipe, thereby achieving fluid isolation [ 7 , 8 ]. During the replacement of pressure piping in a heavy-water reactor (HWR) nuclear power plant, it is necessary to establish isolation between the pressure piping and the main heat transfer system [ 9 ]. However, due to equipment construction, there is no isolation valve present between the pressure piping and the main heat transfer piping.…”

“…Consequently, traditional isolation methods would require additional investment in materials and equipment and potentially even partial equipment shutdown, resulting in significant economic losses. In contrast, ice plug technology offers an effective solution by isolating the piping without the need to shut down or discharge the entire system, thereby reducing the risk of radioactive material leakage [ 8 , 9 ]. This technique boasts simplicity, safety, and economic benefits, further enhancing the maintenance capabilities of nuclear power plants [ 6 , 8 , 9 ].…”

“…In contrast, ice plug technology offers an effective solution by isolating the piping without the need to shut down or discharge the entire system, thereby reducing the risk of radioactive material leakage [ 8 , 9 ]. This technique boasts simplicity, safety, and economic benefits, further enhancing the maintenance capabilities of nuclear power plants [ 6 , 8 , 9 ]. However, the formation of an ice plug within a pipe involves large temperature gradients and rapid local freezing processes.…”

Formation Rate and Energy Efficiency of Ice Plug in Pipelines Driven by the Cascade Utilization of Cold Energy

“…It is worth noting, however, that the volume of water increased during the freezing process [11]. Zhang et al [12] investigated the effects of the cooling rate on the maximum internal pressure and the stress of the pipe. For example, the stress of the pipe increased from 164 MPa to 253 MPa with a cooling rate of 0.1795 to 0.7158 • C/min.…”