An extended finite element method‐based representative model for primary water stress corrosion cracking of a control rod driving mechanism penetration nozzle

Abstract

Primary water stress corrosion cracking incidents have been reported in nuclear reactors over the past several decades. Garud et al developed an empirical equation to express primary water stress corrosion cracking (PWSCC) initiation time by using experimental data. This strain rate damage model has been used in multiple simulation studies. Some of these studies used the extended finite element method (XFEM) to simulate the PWSCC propagation in Alloy 600. However, several studies showed that the accuracy of XFEM depends on the mesh quality. Different mesh qualities can change the heat flux of a welding procedure, leading to different weld residual stresses. We performed a parametric study on PWSCC initiation and propagation of a control rod driving mechanism by using different mesh qualities.The major variables explored here are number of elements per bead, number of circumferential elements, and number of weld beads. Finally, an XFEM-based representative model was suggested for PWSCC initiation and propagation simulation.

Prognosis methods of stress corrosion cracking under harsh environmental conditions

“…The results show that the plastic zone is affected by stress intensity factors, yield strength, and hardening exponent “n" of the materials. Lee [ 143 ] discusses a parametric study on primary water stress corrosion cracking (PWSCC) initiation and propagation of a control rod driving mechanism by using different mesh qualities. The study aims to suggest an XFEM-based representative model for PWSCC initiation and propagation simulation.…”

Degradation‐based reliability analysis of magnetic jack type control rod drive mechanism

“…Song et al 9 fitted the thermal aging data of the CRDM coil stack assembly based on the Arrhenius regression model and explored the effect of temperature on the life of the coil stack assembly. Hertz 10 carried out the tooth wear research of the CRDM latch assembly, Lee and Chan 11 and Lee et al, 12 simulated the residual stress of the CRDM guide tube J-weld by different finite element methods and simulated the stress corrosion cracking of this J-weld. The studies mainly focus on the reliability assessment of the control system with respect to the CRDM, the aging analysis of the electrical components and the analysis of the stress corrosion cracking mechanism of the welds, and no reliability assessment work has been carried out for the key structural components (latch assembly) of the CRDM.…”

“…3. If the shape function of Gamma process can be expressed as a linear function that is 𝜐(𝑡) = 𝑎𝑡, 𝑎 ≥ 0, the mean and variance of Δ𝐷 𝑖 𝑗 can be formulated as Equation (12) and Equation ( 13), respectively. The solution of the arithmetic mean of 𝑢 𝑗 (𝑗 = 1, 2, … , 𝑛) is the estimated value of the scale parameter of the Gamma process, which is expressed as Equation (14).…”