Abstract
There have been incidents recently where stress corrosion cracking (SCC) observed in the dissimilar metal weld (DMW) joints connecting the reactor pressure vessel (RPV) nozzle with the hot leg pipe. Due to the complex microstructure and mechanical heterogeneity in the weld region, dissimilar metal weld joints are more susceptible to SCC than the bulk steels in the simulated high temperature water environment of pressurized water reactor (PWR). Tensile residual stress (RS), in addition to operating loads, has a great contribution to SCC crack growth. Limited experimental conditions, varied influence factors and diverging experimental data make it difficult to accurately predict the SCC behavior of DMW joints with complex geometry, material configuration, operating loads and crack shape. Based on the film slip/dissolution oxidation model and elastic-plastic finite element method (EPFEM), an approach is developed to quantitatively predict the SCC growth rate of a RPV outlet nozzle DMW joint. Moreover, this approach is expected to be a pre-analytical tool for SCC experiment of DMW joints in PWR primary water environment.
Highlights
Dissimilar metal weld (DMW) joints are widely used to connect the low alloy steel (LAS) nozzles to austenitic stainless steel (SS) pipes in primary water systems of pressurized water reactors (PWR)
Failures show that nickel-based alloy and its associated weld metals are more susceptible to Stress corrosion cracking (SCC) in the simulated high temperature water environments of PWR [2,3,4]
To quantitatively estimate SCC growth rate of the flaws in DMW joints, the local opening stress, plastic strain and J-integral ahead of crack front are investigated
Summary
Dissimilar metal weld (DMW) joints are widely used to connect the low alloy steel (LAS) nozzles to austenitic stainless steel (SS) pipes in primary water systems of pressurized water reactors (PWR). The film slip/dissolution oxidation model is widely regarded as a reasonable description of SCC growth estimation in the nickel-based alloys in high temperature oxygenated environment [7]. In this model, the strain rate at crack tip is usually used as a unique factor to describe the mechanical condition. In this paper, based on the film slip/dissolution oxidation model and EPFEM, an approach is developed to quantitatively predict the SCC growth rate of a RPV outlet nozzle DMW, which services in complex operating loads and welding residual stress. Note that only the hoop stress for an axial crack was applied in the weld region
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