Effect of Uneven Crack Front on Crack Tip Mechanics and the Implication to Stress Corrosion Crack Growth

2009 ◽  
Author(s):  
He Xue ◽  
Zhanpeng Lu ◽  
Hiroyoshi Murakami ◽  
Tetsuo Shoji
Keyword(s):  
Growth Rate ◽  
Crack Growth Rate ◽  
Stress Corrosion ◽  
Crack Growth ◽  
Crack Front ◽  
Pressurized Water Reactor ◽  
Element Analysis ◽  
Pressurized Water ◽  
Water Reactor ◽  
Nickel Base

Uneven crack fronts have been observed in laboratory stress corrosion cracking tests. For example, cracking fronts of nickel-base alloys tested in simulated boiling water reactor (BWR) and pressurized water reactor (PWR) environments could exhibit uneven crack front. Analyzing the effect of an uneven crack front on further crack growth is important for quantification of crack growth. Finite-Element analysis shows that the local KI distribution can be significantly affected by the shape and size of the uneven crack front. Stress intensity factor at the locally extended crack front can be significantly reduced. Since generally there is a nonlinear CGR versus KI relationship, it is expected that crack growth rate at the locally extended crack front can be significantly different from those in the neighboring areas. There could be several patterns for the growth of an uneven crack front. For example, once initiated, the crack growth rate in areas other than the locally protruded front would become higher and then the whole crack front would tend to become uniform. On the other hand, if the crack growth in other areas is still low, there is a possibility that the crack growth rate at the front tip would slow down.

Fatigue Crack Growth Rate of Medium and Low Sulfur Ferritic Steels in Pressurized Water Reactor Primary Water Environments

2003 ◽  
Author(s):  
Ernest D. Eason ◽  
Edward E. Nelson ◽  
Graham B. Heys
Keyword(s):  
Growth Rate ◽  
Fatigue Crack ◽  
Crack Growth Rate ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Pressurized Water Reactor ◽  
Pressurized Water ◽  
Water Reactor ◽  
Primary Water ◽  
Low Sulfur

Models of fatigue crack growth rates for medium and low sulfur ferritic pressure vessel steels in pressurized water reactor (PWR) primary environments are developed based on a recent collection of UK data and the EPRI Database for Environmentally Assisted Cracking (EDEAC). The combined UK and EDEAC database contains a broader range of experimental conditions specific to PWRs than either database by itself. Both probabilistic and conventional crack growth rate models are developed that reduce unnecessary conservatism for medium and low sulfur PWR primary water applications and eliminate the explicit dependence on rise time that caused difficulties applying prior models.

Fatigue Crack Growth Rate of Medium and Low Sulfur Ferritic Steels in Pressurized Water Reactor Primary Water Environments

2003 ◽  
Vol 125 (4) ◽  
pp. 385-392
Author(s):  
Ernest D. Eason ◽  
Edward E. Nelson ◽  
Graham B. Heys
Keyword(s):  
Growth Rate ◽  
Fatigue Crack ◽  
Crack Growth Rate ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Pressurized Water Reactor ◽  
Pressurized Water ◽  
Water Reactor ◽  
Primary Water ◽  
Low Sulfur

Models of fatigue crack growth rates for medium and low sulfur ferritic pressure vessel steels in pressurized water reactor (PWR) primary environments are developed based on a recent collection of UK data and the EPRI Database for Environmentally Assisted Cracking (EDEAC). The combined UK and EDEAC database contains a broader range of experimental conditions specific to PWRs than either database by itself. Both probabilistic and conventional crack growth rate models are developed that reduce unnecessary conservatism for medium and low sulfur PWR primary water applications and eliminate the explicit dependence on rise time that caused difficulties applying prior models.

Effects of Dissolved Hydrogen on Crack Growth Rate of Warm-Rolled 316L Austenitic Stainless Steel in Primary Water Condition

2015 ◽  
Author(s):  
Kyoung Joon Choi ◽  
Seung Chang Yoo ◽  
Taeho Kim ◽  
Seong Sik Hwang ◽  
Min Jae Choi ◽  
...  
Keyword(s):  
Growth Rate ◽  
Stainless Steel ◽  
Crack Growth Rate ◽  
Crack Growth ◽  
Hydrogen Concentration ◽  
Pressurized Water Reactor ◽  
Pressurized Water ◽  
Water Condition ◽  
Primary Water ◽  
Dissolved Hydrogen

With the extension of pressurized water reactor’s design life or continued operation, more careful study on the integrity of the internal structures needs to be pursued. In this study, warm-rolling and heat-treatment were applied to 316L stainless steel, in order to simulate the effect of radiation damage such as hardening and radiation-induced grain boundary segregation. And, the crack growth rate testing under constant load condition was performed in the primary water conditions of a pressurized water reactor. Also, in order to investigate the effect of dissolved hydrogen on the crack growth, the dissolved hydrogen concentration was varied between 30 to 50 cc/kg in simulated primary water condition of a pressurized water reactor. The warm-rolled specimens showed the higher crack growth rate than as-received one. Also, the crack growth rate increased as the dissolved hydrogen concentration increases.

Negative Load Ratio Fatigue Crack Growth Rate Testing on Austenitic Stainless Steel in a Simulated Primary Water Environment

2015 ◽  
Author(s):  
Norman Platts ◽  
David R. Tice ◽  
Wenzhong Zhang
Keyword(s):  
Growth Rate ◽  
Fatigue Crack ◽  
Crack Growth Rate ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Fatigue Crack Growth Rate ◽  
Loading Test ◽  
Element Analysis ◽  
Pressurized Water ◽  
Test Methodology

Light water reactor coolant environments are known to significantly enhance the fatigue crack growth rate of austenitic stainless steels. However, most available data in these high temperature pressurized water environments have been derived using specimens tested at positive load ratios, whilst many plant transients involve significant compressive as well as tensile stresses. The extent to which the compressive loading impacts on the environmental enhancement of fatigue crack growth and more importantly on the processes leading to retardation of those enhanced rates is therefore unclear, potentially leading to excessive conservatism in current assessment methodologies. A test methodology using corner cracked tensile specimens has been developed which provides significant advantages over more conventional specimen geometries in terms of autoclave testing at negative load ratios. Finite element analysis of the specimen geometry has been performed to generate effective stress intensity factors, Keff, for specimens loaded in fully reverse loading. Test data generated in both air and water are compared to conventional compact tension specimen data to validate the test methodology.

scholarly journals Crack Growth Rate Testing With Instrumented Bolt-Load Compact Tension Specimens Under Chloride-Induced Stress Corrosion Cracking Conditions in Spent Nuclear Fuel Canisters

2017 ◽  
Author(s):  
Andrew J. Duncan ◽  
Poh-Sang Lam ◽  
Robert L. Sindelar ◽  
Joe T. Carter
Keyword(s):  
Growth Rate ◽  
Crack Growth Rate ◽  
Stress Corrosion ◽  
Crack Growth ◽  
Stress Corrosion Cracking ◽  
Crack Front ◽  
Spent Nuclear Fuel ◽  
Compact Tension ◽  
Corrosion Cracking ◽  
Induced Stress

Stress corrosion cracking (SCC) may occur when chloride-bearing salts and/or dust deliquesce on the external surface of the spent nuclear fuel (SNF) canister at weld residual stress regions. An SCC growth rate test is developed using instrumented bolt-load compact tension specimens using the American Society for Testing Materials (ASTM) specification E1681 with an experimental apparatus that allows an initially dried salt to deliquesce and infuse naturally to the crack front under temperature and humidity parameters relevant to the canister storage environmental conditions. The shakedown tests were conducted over a range of relative humidity controlled by the guidance in ASTM E104 at 50 °C with salt assemblages of (1) mixture of artificial dust and deliquescent salts (2) a mixture of artificial dust and salt from dehydrated sea water. After five months exposure the specimens were examined for evidence of chloride induced stress corrosion cracking (CISCC) and observations are reported for both salt/dust mixtures. The test specimen and apparatus designs will be modified to enhance the interaction between the deliquescing salt and the crack front for more accurate characterization of the crack growth rate as a function of stress intensity factor, which is an essential input to the determination of in-service inspection frequency of SNF canisters.

Technical Basis for Revisions to ASME Section XI Acceptance Standards for Surface Flaws in Piping in Stress Corrosion Cracking Susceptible Materials

2009 ◽  
Author(s):  
Douglas A. Scarth ◽  
Katsumasa Miyazaki ◽  
Kunio Hasegawa ◽  
Warren H. Bamford
Keyword(s):  
Stress Corrosion ◽  
Crack Growth ◽  
Stress Corrosion Cracking ◽  
Corrosion Cracking ◽  
Pressurized Water Reactor ◽  
Planar Surface ◽  
Pressurized Water ◽  
Water Reactor ◽  
Crack Growth Mechanism ◽  
Technical Basis

Acceptance Standards for flaws in piping are provided in Section XI of the ASME B&PV Code to permit acceptance of relatively small flaws without the need to perform an analytical evaluation. The Acceptance Standards are based on maintaining large margins against failure, and are based on the assumption that flaw growth will be insignificant. The assumption of a small amount of flaw growth is justified when fatigue crack growth is the only crack growth mechanism. However, when stress corrosion cracking is operative, flaw growth could be significant. This conclusion was illustrated by comparison of the crack growth results due to fatigue and stress corrosion cracking in Pressurized Water Reactor (PWR), and Boiling Water Reactor (BWR), coolant environments. For this reason, IWB-3514 of Section XI prohibits use of the Acceptance Standards for planar surface-connected flaws that are detected in piping materials that are susceptible to stress corrosion cracking and are in reactor coolant environments. As part of a recent Code revision to include new Acceptance Standards tables for flaws in piping, restrictions on use of the Acceptance Standards of IWB-3514 have been refined and clarified. The recent Code revision now specifies different restrictions and requirements for use of the Acceptance Standards for such planar surface-connected flaws detected by preservice and inservice examination. In addition, similar restrictions have been imposed on use of the new Acceptance Standards for such planar surface-connected flaws in Class 2 piping in IWC-3514 of Section XI. The technical basis for the restrictions and requirements for use of the Acceptance Standards for planar surface-connected flaws in piping materials that are susceptible to stress corrosion cracking is provided in this paper.

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