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Research Papers: Materials and Fabrication

Quantitative Estimation of the Growth of Environmentally Assisted Cracks at Flaws in Light Water Reactor Components

[+] Author and Article Information
H. Xue

Fracture and Reliability Research Institute, Tohoku University, Sendai 980-8579, Japan and School of Mechanical Engineering, Xi'an University of Science and Technology, Xi'an 710054, China

Y. Sato, T. Shoji

Fracture and Reliability Research Institute, Tohoku University, Sendai 980-8579, Japan

J. Pressure Vessel Technol 131(1), 011404 (Nov 26, 2008) (9 pages) doi:10.1115/1.3027458 History: Received June 13, 2007; Revised January 22, 2008; Published November 26, 2008

Since environmentally assisted cracking (EAC) is an important degradation mechanism affecting the structural materials of nuclear power plants, numerous EAC experiments have been performed in the past three decades using standard specimens in simulated high temperature water environments to evaluate the various core materials used in light water reactors (LWRs). However, the environment, the condition of the material, and the mechanical properties near flaws in LWR components are not absolutely equivalent to those near the crack tip in standard specimens; thus, more research needs to be done before EAC growth in an actual LWR component can be accurately estimated using existing experimental EAC data. By combining the film slip-dissolution/oxidation model with the elastic-plastic finite element method and existing experimental EAC data, we have derived a method by which an estimation of EAC growth at flaws in actual LWR components can be made. In this paper we propose and discuss the use of this method. The results show that this new method basically concurs with the Fracture Research Institute (FRI) model in evaluating EAC growth across a semi-elliptic crack front under a simple tensile load and is also in approximate agreement with the experimental results obtained in evaluating EAC growth along a semi-elliptic crack front under complex loading conditions. The approach is expected to form a bridge between predicting EAC growth rate in core materials and evaluating EAC growth in key structural components in LWRs, and it is also expected that it can be used as a pre-analytical tool for EAC experiments using nonstandard specimens.

Copyright © 2009 by American Society of Mechanical Engineers
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Figures

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Figure 1

Schematic illustration of the oxidation current density transients at the crack tip

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Figure 2

Theoretical basis for quantitatively estimating EAC growth in a light water reactor

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Figure 3

Framework of the evaluation process

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Figure 4

Geometrical shape and size of a specimen with an elliptical crack

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Figure 5

Mesh of the specimen

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Figure 6

Crack driving force across the crack front: (a) KI across the crack front and (b) J across the crack front

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Figure 7

Variation in tensile plastic strain with crack growth across the crack front

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Figure 8

EAC crack growth rate across the crack front

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Figure 9

Estimation of EAC growth across a crack front based on the proposed approach

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Figure 10

Estimated result of EAC growth along the crack front based on the FRI model

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Figure 11

Geometry size of the pipe specimen with two inner axial surface cracks

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Figure 12

FEM model of the specimen: (a) whole model and (b) submodel

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Figure 13

Mesh used for the specimen: (a) mesh used for the whole model and (b) mesh used for the submodel

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Figure 14

Crack driving force across the crack front: (a) KI across the crack front and (b) J across the crack front

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Figure 15

Variation in tensile plastic strain with crack growth along the crack front

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Figure 16

EAC crack growth rate along the crack front

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Figure 17

Estimated result of EAC growth along the crack front based on the proposed approach

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Figure 18

Pipe specimen with two inner axial cracks

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Figure 19

EAC experimental result

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