Research on Corrosion Analysis of Displacement Measurement System for Nuclear Power Plant Containment with Invar Steel Wire Material

To address the issues of corrosion and fracture of the monitoring wires in the containment shell displacement measurement system of a certain nuclear power plant, it is urgently necessary to select a suitable monitoring wire for on-site use. To achieve this, this paper first establishes experimental environmental parameters based on statistical data from the on-site environment of the nuclear power plant and reference standards. Secondly, experimental materials and methods are determined through literature review and practical investigation: A salt spray accelerated corrosion aging test was developed for four types of nickel-iron alloy (Invar) wires (4J29, 4J32, 4J36, S4J32A), stainless steel, and TM-V221 bisphenol A epoxy pultruded resin (carbon fiber), aiming to assess the corrosion condition, corrosion resistance, quality changes, and mechanical property variations of different types of monitoring wires. The test results indicate that the corrosion condition and corrosion resistance of stainless steel and carbon fiber materials are superior to those of Invar materials. The degree of corrosion in Invar materials ranges from slight to severe, with the corrosion resistance time being longest for 4J29, followed by S4J32A, and then 4J36. Regarding maximum strength, tensile strength, and yield strength, the order from strongest to weakest is Invar materials 4J29 and 4J32, carbon fiber materials, stainless steel materials, and Invar materials 4J36 and S4J32A. This experiment provides a data foundation and experimental basis for the selection of alternative monitoring wire materials for nuclear power plants.