Making something out of nothing: Enhanced flaw tolerance and rupture resistance in elastomer–void “negative” composites

A typical multipurpose canister (MPC) is made of austenitic stainless steel and is loaded with spent nuclear fuel assemblies. The canister may be subject to service-induced degradation when it is exposed to aggressive atmospheric environments during a possibly long-term storage period if the permanent repository is yet to be identified and readied. Because heat treatment for stress relief is not required for the construction of an MPC, stress corrosion cracking may be initiated on the canister surface in the welds or in the heat affected zone. An acceptance criteria methodology is being developed for flaw disposition should the crack-like defects be detected by periodic Inservice Inspection. The first-order instability flaw sizes has been determined with bounding flaw configurations, that is, through-wall axial or circumferential cracks, and part-through-wall long axial flaw or 360° circumferential crack. The procedure recommended by the American Petroleum Institute (API) 579 Fitness-for-Service code (Second Edition) is used to estimate the instability crack length or depth by implementing the failure assessment diagram (FAD) methodology. The welding residual stresses are mostly unknown and are therefore estimated with the API 579 procedure. It is demonstrated in this paper that the residual stress has significant impact on the instability length or depth of the crack. The findings will limit the applicability of the flaw tolerance obtained from limit load approach where residual stress is ignored and only ligament yielding is considered.

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Comparison of International Codes for a Fatigue Crack Growth Flaw Tolerance Sample Problem

10.1115/pvp2021-61651 ◽

2021 ◽

Author(s):

Gary L. Stevens

Keyword(s):

Fatigue Crack ◽

Fatigue Crack Growth ◽

Crack Growth ◽

Large Diameter ◽

Sample Problem ◽

Pressurized Water ◽

Typical Application ◽

Flaw Tolerance ◽

Asme Code ◽

The Impact

Abstract As part of the development of American Society of Mechanical Engineers Code Case N-809 [1], a series of sample calculations were performed to gain experience in using the Code Case methods and to determine the impact on a typical application. Specifically, the application of N-809 in a fatigue crack growth analysis was evaluated for a large diameter austenitic pipe in a pressurized water reactor coolant system main loop using the current analytical evaluation procedures in Appendix C of Section XI of the ASME Code [2]. The same example problem was previously used to evaluate the reference fatigue crack growth curves during the development of N-809, as well as to compare N-809 methods to similar methods adopted by the Japan Society of Mechanical Engineers. The previous example problem used to evaluate N-809 during its development was embellished and has been used to evaluate additional proposed ASME Code changes. For example, the Electric Power Research Institute investigated possible improvements to ASME Code, Section XI, Nonmandatory Appendix L [3], and the previous N-809 example problem formed the basis for flaw tolerance calculations to evaluate those proposed improvements [4]. In addition, the ASME Code Section XI, Working Group on Flaw Evaluation Reference Curves continues to evaluate additional research data and related improvements to N-809 and other fatigue crack growth rate methods. As a part of these Code investigations, EPRI performed calculations for the Appendix L flaw tolerance sample problem using three international codes and standards to evaluate fatigue crack growth (da/dN) curves for PWR environments: (1) ASME Code Case N-809, (2) JSME Code methods [5], and (3) the French RSE-M method [6]. The results of these comparative calculations are presented and discussed in this paper.

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A Flaw Tolerance Concept for Plant Maintenance Using Virtual Fatigue Crack Growth Curve

Volume 1A: Codes and Standards ◽

10.1115/pvp2013-97851 ◽

2013 ◽

Cited By ~ 7

Author(s):

Masayuki Kamaya ◽

Takao Nakamura

Keyword(s):

Fatigue Crack ◽

Fatigue Life ◽

Fatigue Crack Growth ◽

Crack Growth ◽

Growth Curve ◽

Growth Behavior ◽

Plant Design ◽

Flaw Tolerance ◽

Plant Maintenance ◽

Crack Growth Curve

Incorporation of the flaw tolerance concept in plant design and maintenance is discussed in order to consider the reduction in fatigue life due to the high-temperature water environment of class 1 components of NPPs. The flaw tolerance concept has been included in Section XI of the ASME BPVC. The structural factor (safety factor) for the flaw evaluation is considered in the stress, whereas it was considered in the design fatigue curve in Section III of the ASME BPVC. In order to apply the flaw tolerance concept to plant design and maintenance, it is necessary to assume the crack initiation and growth behavior. In this study, first, crack initiation and growth behavior during fatigue tests was reviewed and a relationship between the crack growth and fatigue life was quantified. Then, the safety factor was considered in the crack growth curve. It was shown that the crack size could be correlated to the usage factor and the flaw tolerance concept was reasonably considered in the plant maintenance by using the proposed virtual fatigue crack growth curve.

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Flaw Tolerance of Nuclear Intermediate Filament Lamina under Extreme Mechanical Deformation

ACS Nano ◽

10.1021/nn200107u ◽

2011 ◽

Vol 5 (4) ◽

pp. 3034-3042 ◽

Cited By ~ 32

Author(s):

Zhao Qin ◽

Markus J. Buehler

Keyword(s):

Intermediate Filament ◽

Mechanical Deformation ◽

Flaw Tolerance

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Flaw Tolerance Evaluation of CASS Piping Materials

Volume 1: Codes and Standards ◽

10.1115/pvp2009-77421 ◽

2009 ◽

Author(s):

Timothy J. Griesbach ◽

Vikram Marthandam ◽

Haiyang Qian ◽

Patrick O’Regan

Keyword(s):

Fracture Toughness ◽

Weld Metal ◽

Thermal Aging ◽

Prolonged Exposure ◽

Delta Ferrite ◽

Acceptance Criteria ◽

Centrifugally Cast ◽

Reactor Coolant ◽

Flaw Tolerance ◽

Asme Code

Prolonged exposure of cast austenitic stainless steels (CASS) to reactor coolant operating temperatures has been shown to lead to some degree of thermal aging embrittlement (reduction in fracture toughness of the material as a function of time). The fracture toughness data for the most severely aged CASS materials were found to be similar to those reported for some austenitic stainless steel weld metal, in particular weld metal from submerged arc welds (SAW). Such similarity offers the possibility for applying periodic inservice inspection flaw acceptance criteria, currently referenced in the ASME Code Section XI, Subsection IWB, for SAW and shielded metal arc weld (SMAW), to CASS component inservice inspection results. This paper presents the data to support both the proposed screening criteria (based on J-R crack growth resistance) for evaluation of the potential significance of the effects of thermal aging embrittlement for Class 1 reactor coolant system and primary pressure boundary CASS components, for those situations where the effects of thermal aging embrittlement are found to be potentially significant. The fitness for continued service is based on the comparison of the limiting fracture toughness data for Type 316 SAW welds and the lower-bound fracture toughness data reported for high-molybdenum, high delta-ferrite, statically and centrifugally-cast CASS materials. These comparisons and the associated flaw acceptance criteria can be used to justify exemptions from current ASME Code Section XI inservice inspection requirements through flaw tolerance evaluation (e.g., see ASME Nuclear Code Case N-481).

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In-Service Inspection Strategy for Alloy X-750 BWR Jet Pump Beams Based Upon Linear Elastic Fracture Mechanics Analysis

Volume 6: Materials and Fabrication, Parts A and B ◽

10.1115/pvp2009-77131 ◽

2009 ◽

Author(s):

Daniel V. Sommerville ◽

Hardayal Mehta ◽

Robert Carter ◽

Jonathon Kubiak

Keyword(s):

Fracture Mechanics ◽

Pump Beam ◽

Operating Experience ◽

Linear Elastic Fracture Mechanics ◽

Jet Pump ◽

Linear Elastic ◽

Flaw Tolerance ◽

Beam Design ◽

Jet Pumps ◽

Elastic Fracture

Jet pumps in a boiling water reactor (BWR) are located in the annulus region between the core shroud and the reactor vessel wall and provide core flow to control reactor power. Between 16 and 24 jet pumps are included in BWR/3 through BWR/6 plants, depending on the plant rating. The inlet mixer assembly of the jet pump is secured in place with a hold down mechanism called a jet pump beam. This beam is fabricated of alloy X-750 and tensioned to 58–74% of the yield stress of the material, depending on the beam design. In recent years, more attention has been placed upon inter-granular stress corrosion cracking (IGSCC) of alloy X-750 BWR internal components as a result of in-service cracking and failures. BWR plant owners have implemented actions to manage IGSCC of jet pump beams and assemblies through increased inspections and changes to process specifications for X-750. However, a thorough understanding of the flaw tolerance of the jet pump beam was not available to guide the periodicity of inspections as well as to define critical flaw sizes needed to validate the capability of inspection techniques. This paper describes a linear elastic fracture mechanics (LEFM) evaluation in which the flaw tolerance of the existing jet pump beam designs is established and used to recommend inspection frequencies for the jet pump beam. Industry operating experience is used to assess the credibility of the results obtained from this evaluation. This work illustrates an example of the use of LEFM to develop a technically defensible basis for the required inspection regions and the frequency of inspection for an alloy X-750 BWR internal component and helps to establish the necessary sensitivity of non-destructive examination technology to be used to examine the component.

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Application of ASME Code Section XI Appendix L Using 3-D Finite Element Analyses

Volume 1: Codes and Standards ◽

10.1115/pvp2020-21729 ◽

2020 ◽

Author(s):

Charles Fourcade ◽

Minji Fong ◽

James Axline ◽

Do Jun Shim ◽

Chris Lohse ◽

...

Keyword(s):

Finite Element Analysis ◽

Finite Element ◽

Crack Growth ◽

Cyclic Stress ◽

Finite Element Analyses ◽

Element Analysis ◽

Aspect Ratios ◽

Flaw Tolerance ◽

Asme Code ◽

Stress Ratios

Abstract As part of a fatigue management program for subsequent license renewal, a flaw tolerance evaluation based on ASME Code, Section XI, Appendix L may be performed. The current ASME Code, Section XI, Appendix L flaw tolerance methodology requires determination of the flaw aspect ratio for initial flaw size calculation. The flaw aspect ratios listed in ASME Section XI, Appendix L, Table L-3210-2, for austenitic piping for example, are listed as a function of the membrane-to-gradient cyclic stress ratio. The Code does not explicitly describe how to determine the ratio, especially when utilizing complex finite element analyses (FEA), involving different loading conditions (i.e. thermal transients, piping loads, pressure, etc.). The intent of the paper is to describe the methods being employed to determine the membrane-to-gradient cyclic stress ratios, and the corresponding flaw aspect ratios (a/l) listed in Table L-3210-2, when using finite element analysis methodology. Included will be a sample Appendix L evaluation, using finite element analysis of a pressurized water reactor (PWR) pressurizer surge line, including crack growth calculations for circumferential flaws in stainless steel piping. Based on this example, it has been demonstrated that, unless correctly separated, the membrane-to-gradient cyclic stress ratios can result in extremely long initial flaw lengths, and correspondingly short crack growth durations.

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Effects of Structure and Property Variations Within Hierarchal Biomineralized Composites Using Finite Element Methods

Volume 14: Emerging Technologies; Materials: Genetics to Structures; Safety Engineering and Risk Analysis ◽

10.1115/imece2016-67612 ◽

2016 ◽

Author(s):

Matt Nelms ◽

Ken Livi ◽

Bryan Crawford ◽

A. M. Rajendran ◽

Wayne Hodo

Keyword(s):

Finite Element ◽

High Strength ◽

Elastic Response ◽

Science And Engineering ◽

Structure And Property ◽

Alligator Gar ◽

Flaw Tolerance ◽

Delamination Resistance ◽

Abalone Shell ◽

Atractosteus Spatula

Biological materials (biomaterials) have had a marked increase in interest from the material science and engineering community due to unique characteristics and properties that are typically sought after in traditional engineering materials. During the last few decades, research on biomineralized composites such as abalone shell, fish armor, turtle shell, and human bone revealed that those biological systems possess a carefully arranged multilayered composite structure. Unlike metals, ceramics, and traditional composite materials; biomineralized composites often possess enhanced characteristics such as, penetration resistance high toughness, flaw tolerance energy dissipation, damage mitigation, and delamination resistance all while achieving high strength-to-weight ratios. In this research experimentally driven finite element modeling was used to investigate the elastic response for the biocomposite structure. The Atractosteus spatula (Alligator gar) was used as the model structure for determining the elastic properties.

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