WRC 404:1995

$26.65

Fatigue Crack Growth of Low-Alloy Steels in Light Water Reactor Environments: Report 1, Report 2 and Report 3

Published By	Publication Date	Number of Pages
WRC	1995	61

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Description

Part 1: Fatigue Crack Growth of Low-Alloy Steels in Light Water Reactor Environments – Report 1: Environmentally-Assisted Cracking of Ferritic Steels in Aqueous Environments: An Interpretive Review

It has been recognized for many years that the environment surrounding a fatigue specimen (or structural component) can interact in a manner that can degrade the fatigue response. This is true for both the processes of fatigue crack initiation and fatigue crack propagation (FCP). Following the pioneering work of Kondo and co-workers over twenty years ago, a phenomenon generally known as environmentally-assisted cracking (EAC) has received a great deal of attention in the nuclear industry worldwide because it has the potential to cause significant severe in-service crack extension. For example, Anderson et al have shown that some cracks smaller than those that can be reliably detected are predicted to grow to unacceptable sizes when subjected to the maximum fatigue usage factors allowed by Section III of the ASME Boiler and Pressure Vessel Code (hereafter called the Code) and the present EAC curves from Section XI of the Code.

Fatigue Crack Growth of Low-Alloy Steels in Light Water Reactor Environments – Report 2: Modeling of Fatigue Crack Growth Rate for Ferritic Steels in Light Water Reactor Environments

This paper presents the methodology and results of an effort to analyze and model a large set of fatigue crack propagation data on A508 Class 2 and Class 3 and A533B pressure vessel steel in light water reactor (LWR) environments. The data were from a variety of laboratories worldwide, in most cases contributed to the EPRI Database on Environmentally Assisted Cracking (EAC). The data were analyzed in a consistent manner using the computer code FATDAC, which minimizes the scatter arising from numerical differentiation during fatigue data reduction. The models were developed in the time domain, then converted to the more conventional da/dN vs ?K form. Two modes of corrosion fatigue crack growth behavior were identified and modeled, one about a factor of two faster than the rates in air and independent of loading rate and the other up to two orders of magnitude faster and strongly dependent on loading rate. Variables such as material sulfur content, sulfide inclusion morphology, water chemistry, R-ratio, load rise time, stress intensity range, temperature, electrochemical potential, and flow velocity affect both the probability of observing the highly enhanced crack growth rates and the rates themselves. Representative crack propagation models are developed and presented in this paper together with supporting data.

Fatigue Crack Growth of Low-Alloy Steels in Light Water Reactor Environments – Report 3: Technical Basis for a Revised Fatigue Crack Growth Rate Reference Curve for Ferritic Steels in Light Water Reactor Environments

This paper presents the technical basis for improved fatigue crack propagation reference curves for pressure vessel and related ferritic steels in light water reactor (LWR) environments. The primary improvements over previous reference curves are explicit modeling of load rise time effects, calibration to a much larger set of data analyzed in a consistent manner, and adjustment of the reference curves to be conservative over the range of reactor operating temperatures. The reference curves are proposed for inclusion in the non-mandatory Appendix A of the ASME Pressure Vessel Code, Section XI. Important variables that are not explicitly included in the reference curves are discussed.

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