   In JEAC4206 which prescribes the methodology for assessing the structural integrity of reactor pressure vessels (RPVs), an under-clad crack (UCC) at the inner surface of RPV is postulated. Some papers present that the stress intensity factor (*K~I~*) of the deepest point of UCC increases due to plasticity of cladding under PTS events based on a series of parametric finite element analyses (FEAs). However, the effect of cladding on the fracture mechanics evaluation was not experimentally understood. In this study, to investigate the effect of cladding on fracture mechanics evaluation, we performed experiments and FEAs for three-point bending tests with UCC in RPV steel. The material used in this study was a low-copper RPV steel (0.03wt.%Cu) with weld-overlay cladding corresponding to 308 stainless steel. The fatigue pre-crack for UCC was introduced after the welding. From a series of three-point bending tests, load-displacement curve was obtained to validate the FEA method on RPV steels with cladding. In FEA, considering the solidification texture formed in the weld-overlay cladding procedure, the anisotropy of Young’s modulus of cladding is taken into account to improve the accuracy of FEA results. Through the comparison in load-displacement curves between experiments and FEAs, we could confirm that the anisotropy of cladding has an important role for FEAs including UCC. In addition, we evaluate the effect of cladding on the fracture mechanics parameters for discussing the plasticity constraint due to cladding.

 


Constraint Effect on Fracture Mechanics Evaluation for an Under-Clad Crack in a Reactor Pressure Vessel Steel

Division / Sponsors: 
Pressure Vessels & Piping (PVP)


Paper Proceedings: https://asmedigitalcollection.asme.org/PVP/PVP2020/volume/83815

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