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RESEARCH PAPERS

Unified Interpretation of Crack Growth Rates of Ni-base Alloys in LWR Environments

[+] Author and Article Information
Zhanpeng Lu

Fracture and Reliability Research Institute, Graduate School of Engineering, Tohoku University, Aramaki Aoba 6-6-11-717, Aoba-ku, Sendai/980-8579, Japanzhanpeng@rift.mech.tohoku.ac.jp

Tetsuo Shoji

Fracture and Reliability Research Institute, Graduate School of Engineering, Tohoku University, Aramaki Aoba 6-6-11-717, Aoba-ku, Sendai/980-8579, Japantshoji@rift.mech.tohoku.ac.jp

J. Pressure Vessel Technol 128(3), 318-327 (Aug 08, 2005) (10 pages) doi:10.1115/1.2217964 History: Received April 25, 2004; Revised August 08, 2005

Primary water stress corrosion cracking (PWSCC) of vessel penetrations (VP) fabricated from nickel based alloys such as alloy 600 and alloy 182 weld metal has created a great demand for elucidation of the cracking mechanism and for development of life prediction technologies. The generalized FRI crack growth rate (CGR) formulation was proposed, based on a deformation/oxidation mechanism and a theoretical crack tip strain rate equation derived by the authors. The effects of crack tip oxidation and crack tip mechanics and of their interactions on crack growth can be quantified. Experimental and actual plant data of CGR for alloy 600 in PWR primary water, which are sometimes scattered in CGR-K diagrams, are interpreted with the generalized CGR formulation, emphasizing the effects of temperature, K, yield strength and variations of K with time. It is suggested that it is essential to determine the type of dependency of CGR on K for accurate flaw disposition. The generalized formulation provides a unique parameter for interpreting CGRs as well as a unified method for predicting CGRs within a narrow scattered band even under various testing parameters, which is the basis for accurately predicting component life.

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Copyright © 2006 by American Society of Mechanical Engineers
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References

Figures

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Figure 8

Experimental (4) and calculated CGR data in terms of K for alloy 182 in simulated PWR primary water

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Figure 9

Experimental (12,16-17) and predicted CGR-YS curves for alloy 600 in simulated PWR and BWR environments

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Figure 10

Experimental CGR data (4,12,15-17) and predicted values based on the FRI generalized CGR model for nickel base alloys and weld metals in LWR environments

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Figure 11

Field CGR data for nickel base alloys and weldments from EDF, Cook 2 and Ringhal unit 3 (4,9-10), along with values predicted by different CGR models (here n is taken to be 2 in the calculation for the weldment)

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Figure 1

Schematic of the general sub-processes for SCC propagation in high temperature waters

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Figure 2

Calculated Kth as a function of r for materials with various values of YS, which is determined as the K value where crack tip plastic strain rate becomes zero

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Figure 3

Numerical analysis of crack tip strain in terms of K for materials with different YS

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Figure 4

Numerical analysis of CGR as a function of K for two materials with different values of YS and n

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Figure 5

Numerical analysis of the effects of κa or m on CGR for different values of YS using Eq. 17

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Figure 6

Experimental (12,16-17) and calculated CTSRs for alloy 600 in simulated PWR and BWR environments

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Figure 7

Experimental (15,17) and calculated CGR-K curves for alloy 600 in simulated PWR primary water

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