bluuebunny/crossref_metadata_2025 huggingface dataset:
Strategies for Application of Reliability and Integrity Management for Inservice Inspection of Compact Heat Exchangers in High Temperature Reactors
Authors: Keating Robert , McKillop Suzanne , Jentz Ian
Published: October 2021

The U.S. Department of Energy has recently completed a research program to support the development of the compact heat exchanger (CHX) for use in high temperature advanced reactors. The project was executed by an Integrated Research Project (IRP) and includes team members from the University of Wisconsin–Madison, University of Michigan, Georgia Institute of Technology, University of Idaho, North Carolina State University, Oregon State University, Electric Power Research Institute, MPR Associates, and heat exchangers manufacturers CompRex and Vacuum Process Engineering.

The objective of the research was to enable the use of compact heat exchanger designs in high temperature advanced reactor service in order to improve plant efficiency and economics. A necessary step for achieving this objective is to ensure that the ASME Boiler and Pressure Vessel Code, Section III has rules for the construction of CHXs for nuclear service. However, construction rules alone are not sufficient to deploy a compact heat exchanger in an advanced reactor. ASME Section XI Rules for the Inservice Inspection (ISI) of a heat exchanger in an operating nuclear reactor will be required, and mostly likely ISI will be conducted in according with ASME Section XI, Division 2, Reliability and Integrity Management (RIM) methodology, which is a non-deterministic, technology neutral, approach to inservice inspection.

Since a RIM based ISI program is developed by an owner considering the entire reactor technology safety case, owners will need specific information regarding the performance, failure modes, reliability, and inspection options for compact heat exchangers. Previously, ICONE27-1139 provided strategies for inservice inspection of compact heat exchanger that outlined how an owner can use the planned IRP research to support the development of an ISI program that includes compact heat exchangers.

Now that the IRP research is completed, this paper updates the earlier strategy to reflect the results of the research. Failure mechanisms for compact heat exchanger are unique and not widely understood. The IRP has studied the failure mechanisms, monitoring and inspection technologies and this research may be used to enable an owner/operator of an advanced nuclear reactor to develop a RIM based inservice program.
Vibration Propagation Analysis of Periodic Pipeline With Crack Defects
Authors: Wang Donghui , Zeng Qingna , Zang Fenggang , Zhang Yixiong
Published: October 2021

In this paper, the vibration propagation characteristic is investigated for periodic composite pipeline with crack damage. A novel modified transfer matrix method (TMM) is developed to investigate transverse Band Gap structures (BGs) considering fluid structure interaction, and validated by frequency response function (FRF) for finite period. Field transfer matrix is developed for straight pipeline conveying fluid, and point transfer matrix is derived for circumferential cracks damage based on spring hinge model, which could estimate the equivalent rotational stiffness by local flexibility coefficient method. It’s demonstrated that the existence of small crack damage has negligible effect on BGs, while severe crack damage has significant influence on vibration propagation even it only exists in a single cell. Meanwhile, the difference of FRF between cracked and perfect pipeline provides new idea in diagnosing the crack status. The influence of crack damage on BGs is mainly attributed to the equivalent rotational stiffness. Location of crack damage could affect the stiffness ratio of composite pipeline, and result in the change of original BGs. This study enriches the theoretical TMM for pipeline systems vibration with crack damage, and provides some reference for the stability design of periodic pipeline structures.
General Metal to Metal Static Seals Leak Tightness Overview - R&D Processes, FEA and Tests and Further Code Implementation
Authors: Lutkiewicz Przemyslaw , Robertson David , Lee Sam (Kwok Lun)
Published: October 2021

Latest development in oil and gas industry is focused on higher pressure and temperature. In addition, standard oil and gas components are more frequent adapted to the other applications like aerospace, food processing, renewable energy. For those conditions, tightness is even more critical than before. In the existing codes the requirements for different tightness classes can be find as well as detailed fugitive emission test descriptions. However, the complete design methodology for HPHT seal solution is still missing. There is no engineering procedure/methodology in the code which will link the design concept, R&D process to the prototype and real tests results. The method which will predict tightness for each size and each configuration/condition is not there. Therefore, there is an urgent need to understand the leakage phenomena and describe it by simplified and safe engineering method. Method, which will connect the design concept with real behavior and be in agreement (or conservative) with test results. By having such method, it will be possible to understand better the sealing mechanism in the existing solutions as well as designing new robust, simple, and cheap (optimized) solutions. There are some more or less accurate methods/rules which are already existing in the supplier companies. There is also more and more research about the continuum flow between two surfaces in contact. Based on those sources in this paper we will present the concept for metal to metal sealing solution designing methodology which can be implemented for future revision of the designing codes. The method which can be used simply and effectively and help to understand the current designs and further R&Ds. Presented here design concept, will be described based on example. The example will go through the process from design concept to the real component tightness test.
Use of Synthetic Flaws to Assess Pipeline Seam Weld Inspection Performance
Authors: Krynicki Joseph W. , Peng Lujian , Gonzalez Gustavo , Thirumalai Neeraj
Published: October 2021

Pipeline seam welds are often inspected using ultrasonic In-Line Inspection (ILI) technologies. The measurement performance specification of an ultrasonic ILI tool is based on simple, planar, machined notches which are very reproducible, but are not representative of the complex flaw morphologies that occur naturally in seams such as hook cracks and tilted lack of fusion flaws. In order to assess ILI performance on naturally occurring flaws, “in-the-ditch” Nondestructive Testing (ITD NDT) is performed to validate a subset of the population of ILI reported features.

Due to the limited number, type, and dimensional (height and length) uncertainty of these flaws, the field validation approach has limitations in terms of efficiency and accuracy in determining ILI detection capabilities and sizing performance.

Recently, specialized synthetic flaw fabrication technology has been developed and provides complex, natural crack-like morphologies with reliable and reproducible size dimensions. Effective validation spools with flaws (of representative geometries) can be achieved through engineered designs that consider the number, size and shape of manufactured flaws. This enables owners to quickly and reliably assess the performance of both ILI tools and ITD NDT operators.

Assessing performance with the synthetic flaw approach provides results that are more comprehensive and cost-effective compared to the typical field validation approach alone. This is because the flaw population is designed rather than randomly selected from excavation data.

This paper addresses the design, use and field experience with validation spools. This paper will present the performance of ILI tools and UT examiners based on synthetic flaw qualification exams, and how this supports related ILI and operator validation work.
ASME Section III Standards Committee Fatigue Action Plan
Authors: McKillop Suzanne , Donavin Paul , Keating Robert
Published: October 2021

The ASME Code, Section III, provides rules for the evaluation of cyclic loading that include evaluations of fatigue. These rules were first developed in the 1960s along with the original development of Section III. Since then, technology and analytical advancements have improved our understanding of the fatigue phenomenon. As an example, the developments in environmentally assisted fatigue (EAF) have become a major consideration in the low-cycle fatigue for light water reactors and plant life extension.

Fatigue usage has an outsized impact on the overall cost and complexity of nuclear plants, which goes beyond just the qualification of ASME components. For example, pipe break locations, pipe whip restraints, and inservice inspections are, in part, based on fatigue analysis results. Therefore, it is important that fatigue analyses provide the most realistic assessment of fatigue with appropriate conservatism.

The Section III Standards Committee has been working to keep the Code up to date with the latest research, analysis tools and fatigue data. In 2017, a Fatigue Steering Committee was formed to provide a venue for stakeholders to identify and coordinate development of updated fatigue design criteria, analysis methods, and their associated physical and thermo-mechanical properties for application to Section III of the ASME BPV Code. The stakeholders include many international organizations including the Japan Society of Mechanical Engineers. Many PVP papers have been used as the basis for the Fatigue Action Plan items. The Steering Committee completed its work in 2019 with the adoption of a Fatigue Action Plan, which provided a vision for advanced fatigue approaches. The Fatigue Action Plan recommended specific Code actions and activities to guide and coordinate the Code actions in the area of fatigue.

This paper outlines the overall Fatigue Action Plan and provides an update on the implementation progress. Section III has already accomplished several actions on the Fatigue Action Plan by publishing numerous Code Cases and Code revisions that have improved the analysis tools available to designers to address fatigue. This paper provides an overview and introduction to these Code Cases and other tools for designers.

The Fatigue Action Plan was largely based on addressing the need for the light water reactor fleet to address low cycle thermal fatigue. The Committee also recognizes that going forward the Fatigue Action Plan must address the needs of the growing advanced reactor community as well as other users of the Code. The paper discusses these needs and Section III plans to meet these future needs.
Verification of Accuracy of the Beam Model and Resistant Moment Generated by Base Uplifting of Flat-Bottom Cylindrical Shell Tanks
Authors: Yoshida Yuichi , Taniguchi Tomoyo , Nakashima Teruhiro
Published: October 2021

A purposes of this study are to confirm usefulness of the beam model (Malhotra and Veletsos, 1994) and to check if resistant moment generated by the base uplifting can be a function as a restoring mechanism against the overturning moment. First, this study shows an example of a result of force-displacement relationship calculated by the beam model (Malhotra and Veletsos, 1994), an estimation method of resistant moment and results of the FEM analysis. Next, this study tries to verify the beam model. The relationship between uplift width and uplift displacement calculated by the beam model is compared with the results of FEM analysis. Furthermore, the relationship between uplift force and uplift displacement calculated by the beam model is also compared with the results of the FEM analysis. These comparisons verify the accuracy of the beam model. After that, this study tries to verify resistant moment generated by the base uplifting by comparing with the overturning moment. These verifications imply usefulness of the beam model and existence of a restoration mechanism related to the movement of the content liquid.
Safety Assessment of Long Term Serviced Pressure Vessels: A Case Study of Typical Refining and Chemical Plants in China
Authors: Han Zhiyuan , Xie Guoshan , Jiang Haiyi , Li Xiaowei
Published: October 2021

The safety and risk of the long term serviced pressure vessels, especially which serviced more than 20 years, has become one of the most concerned issues in refining and chemical industry and government safety supervision in China. According to the Chinese pressure vessel safety specification TSG 21-2016 “Supervision Regulation on Safety Technology for Stationary Pressure Vessel”, if necessary, safety assessment should be performed for the pressure vessel which reaches the design service life or exceeds 20 years without a definite design life. However, the safety and risk conditions of most pressure vessels have little changes after long term serviced because their failure modes are time-independent. Thus the key problem is to identify the devices with the time-dependent failure modes and assess them based on the failure modes. This study provided a case study on 16 typical refining and chemical plants including 1870 pressure vessels serviced more than 20 years. The quantitative risk and damage mechanisms were calculated based on API 581, the time-dependent and time-independent failure modes were identified, and the typical pressure vessels were assessed based on API 579. Taking the high pressure hydrogenation plant as an example, this study gave the detailed assessment results and conclusions. The results and suggestions in this study are essential for the safety supervision and extending life of long term serviced pressure vessels in China.
Comparison of International Codes for a Fatigue Crack Growth Flaw Tolerance Sample Problem
Authors: Stevens Gary L.
Published: October 2021

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.
Research on Modal Parameter Identification of Fuel Assembly Based on POD Method
Authors: Huang Xuan , Cai Fengchun , Liu Shuai , Feng Zhipeng , Liu Jian , Jiang Xiaozhou , Zhang Ke
Published: October 2021

In order to obtain accurate modal parameters of fuel assembly in the seismic test of fuel assembly, the finite element model of fuel assembly is taken as the research object, and the sine sweep signal is used as the excitation to act on the node of the model. On the basis of the transient dynamic analysis results, the transfer function of fuel assembly is obtained by using proper orthogonal decomposition (POD) method, and the modal parameters of the fuel assembly are identified by the least square iteration method, and the frequency, damping ratio and vibration mode of the fuel assembly in each mode are obtained. The transfer function obtained by this method and the transfer function calculated by single node response are used to identify the modal parameters respectively, and the results are compared with those of numerical calculation. The analysis results show that compared with single point response calculation, POD method can extract the key information of multiple nodes in time and space domain, and the calculation results of modal parameter identification are more accurate. This method can be used to identify the modal parameters of the subsequent fuel assembly test, and improve the utilization of the test data and the accuracy of the test results.
Stress Intensity Factor Predictions at Clad Interfaces
Authors: Brayshaw W. J. , James P. , Pellereau B.
Published: October 2021

Where a crack has grown such that it crosses a material interface, such as in a clad pressure vessel, there is an additional assessment requirement, above the surface and depth points to evaluate the material interface region. This is typically in terms of fatigue crack growth behaviour and crack extension by ductile tearing.

Generally, elastic stress intensity factor (KI) solutions, such as those in R6, only consider the surface and deepest point locations, and therefore do not provide a methodology to account for any interactions at material interfaces. Therefore, for a material interface, an assessment may look to describe the region by the maximum of the surface or deepest point values, or it may be argued to be represented by the value from either the surface or deepest point, depending on which is geometrically closer. However, this has the potential to lead to overly conservative interpretations in terms of KI and the elastic-plastic equivalent, KJ, at the material interfaces, depending on the fracture toughness and growth laws used.

The work presented here investigates the influence of the clad to plate interface on stress intensity factor under elastic (KI) and elastic-plastic (KJ) conditions for a number of defect geometries, loading conditions and material properties. The results presented in this paper seek to provide guidance on the suitability of KI and KJ for the surface and deepest points, extracted from models containing only plate material properties, to describe the behavior of a crack which crosses a material interface region in a clad pressure vessel wall.
Seismic Failure Modes and Loss of Containment in Industrial Equipment
Authors: Corritore Daniele , Paolacci Fabrizio
Published: October 2021

Major accidents in industrial plants and storage sites may be triggered by seismic events, due to the damage of process equipment resulting in a loss of containment. A quantitative seismic risk analysis is used to demonstrate the risks (individual, societal, economic, and environmental) caused by an activity involving dangerous substances, in the case of earthquakes. Starting from the seismic hazard curve of the site in which the plant is placed, the risk is evaluated through the seismic vulnerability assessment of the equipment, generally expressed in terms of fragility curves. The risk calculation necessarily involves the effects of the content release from a critical unit (e.g., tanks, columns, etc...), which can provoke important effects on the surrounding elements and community. For each critical unit, a set of relevant failure modes and damage states associated with the release of material should be defined. While for steel storage tanks, these failure modes and relationship damage state/loss of containment are available and used, the same cannot be said for the other typologies of industrial equipment as columns, horizontal vessels, compressors, furnaces, etc... This paper aims to provide a criterion to determine damage states and loss of containment resulting from the structural seismic damage for different categories of industrial equipment. This problem has been solved in a deterministic way by introducing a “damage state/loss of containment” correlation matrices. The definition of these correlation matrices for the most critical types of equipment makes it possible to fill a gap that existed in the seismic risk evaluation procedure of an industrial plant, also allowing to evaluate the mean annual frequency of exceeding a certain loss of containment from a critical unit due to the earthquakes.
Estimation of the Threshold Toughness in Acid Environments (KIEAC) By Using Circumferential Notched Tensile Specimens (CNT)
Authors: Arroyo B. , Álvarez J. A. , Gutiérrez-Solana F. , Cayón A. , Cicero S. , Andrea L. , Lacalle R.
Published: October 2021

Medium and high-strength steels working in harsh environments are susceptible of suffering of mechanical properties loss due to hydrogen presence. In order to avoid catastrophic failures, the estimation of the fracture toughness in environment is necessary, but sometimes it is not convenient the use of standard tests; an alternative to the aforementioned traditional fracture mechanics specimens are Circumferential Notched Tensile specimens (CNT), which consist of cylindrical tensile specimens that incorporate a circumferential notch. In this work, CNT specimens subjected to acid aggressive environments, generated by cathodic polarization, are used to estimate the fracture toughness in environment, KIEAC.

For this purpose, two methodologies, one proposed by Singh Raman et al. in the 2000’s and another by Cayón et al. in the 2010’s, are compared. Both formulations rely on similar classic fracture mechanics bases, differing mainly in the way to correct the effects of non-centering of the ligament, caused by asymmetries in the growth of annular cracks in CNT specimens. Both are finally validated to estimate KIEAC, showing good accuracy within the ±L15%.
Error Estimates in Extrapolation of Creep Rupture Data: Applied to an Austenitic Stainless Steel
Authors: Sandström Rolf , He Junjing
Published: October 2021

Precise time extrapolation of creep rupture data is a requirement for components operating at high temperatures. Although qualified models have been available for many years, there has been no way of quantifying the magnitude of the error in the results. To make an error analysis meaningful, requirements on the first and second derivatives are introduced, which are taken into account in the optimization of the model of the predicted creep rupture values. Formulae for the error are presented both for the case when the extrapolated values are interpolated from a master curve and when the values are extrapolated from the master curve.

The criteria have been applied with a time-temperature parameter for the austenitic creep resistant stainless steel Super304H (18Cr9Ni3CuNbN). The results showed a stable behavior with limited oscillating of the creep rupture curves. The prediction automatically fulfilled the post-assessments tests (PATs) proposed by the European Collaborative Creep Committee (ECCC), which are considered to be quite severe requirements.
Can the Four-Hour Installation Dwell Time Be Reduced?
Authors: Girão Carlos D. , Meira Igor , Veiga José Carlos
Published: October 2021

A correct bolted flanged joint tightening procedure includes retorquing to restore short-term creep relaxation and embedment losses; the ASME PCC-1-2019 Tightening Method recommends a minimum of 4 hours of dwell time before retightening the bolts.

It is known that in an industrial plant, maintenance costs come mostly from process downtime in addition to the labor and the tools necessary to perform the operation. Reducing the retorque waiting time would make installation quicker and avoid additional — and unnecessary — costs, returning the plant to revenue operation sooner.

This paper explores whether different gasket styles should have the same dwell time between the installation and retorque, and what would be the dwell time to minimize plant downtime without compromising the gasket performance.

The study was performed using a test rig based on a 4” class 300 ASME B16.5 flange equipped with eight strain-gauged bolts that correlates bolt elongation with applied stress. Four dwell times (15min, 1h, 4h and 24h) and different gasket styles and materials such as PTFE, CFG and metallic gaskets were tested. Additionally, two ASME PCC – 1 installation methods were compared and reported: Legacy Cross-Pattern Numbering System and Alternative Assembly Pattern #3. The former is the typical method for flanged joint tightening operations, while the latter offers a simpler, faster execution.
European Project ATLAS+: Large Scale Fracture Mechanics Tests on Ferritic Pipes
Authors: Dahl Anna , Vincent Willy
Published: October 2021

The 4-years European project ATLAS+ (Advanced Structural Integrity Assessment Tools for Safe long Term Operation) has been launched in June 2017. One of its objectives is to study the transferability of material ductile properties from small scale specimens to large scale components and validate some advanced tools for structural integrity assessment.

The study of properties transferability is based on a wide experimental program which includes a full set of fracture experiments conducted on conventional fracture specimens and large scale components (mainly pipes).

Three materials are considered in the program: a ferritic steel WB36 typical from secondary feed water line in German PWR reactors, an aged stainless steel austenitic weld representative of EPR design and a typical VVER austenitic dissimilar weld (DMW).

This paper describes preparation, realization, fractographic expertise and analysis of large scale tests performed on the ferritic steel WB 36 (15NiCuMoNb5). These large scale tests consisted of four point bending tests on piping’s conducted at room temperature. Two configurations of cracks (shape, size and location) were tested. With the first configuration (FP1), with a through wall crack, a large ductile tearing was obtained. For the second configuration (FP2), with an external semi-elliptical crack, cleavage was obtained after a limited ductile tearing.
Research on Fire Test Method of High Pressure Hydrogen Storage Cylinders for Transportation
Authors: Li Jun , Li Xiang , Li Jiepu , Zhao Baodi , Gu Chunlin , Guan Jian
Published: October 2021

As important equipment in the entire hydrogen industry chain, composite hydrogen storage cylinders for transportation have developed rapidly in recent years. The fire test is used to verify the explosion resistance of gas cylinders under specified fire conditions. Compared to steel gas cylinder, composite gas cylinder is more dangerous in the fire condition. The wound layer, as the main pressure-bearing structure of the composite hydrogen storage cylinder, is inflammable. In the case of fire, the mechanical properties of the cylinder will degrade quickly due to the high temperature. If the gas inside the cylinder cannot be discharged in time, the cylinder explosion will occur. Currently, some relevant standards or standard drafts have been drawn up by the international organizations, which are useful for formulating Chinese standard for hydrogen storage cylinders for transportation. The applicable scope of the standards was discussed in this paper, such as composite cylinder type, working pressure, nominal volume and design life, etc. The fire test methods of composite gas cylinders in various standards were compared and analyzed, such as experiment method, cylinder placement method, cylinder filling requirements, fuel selection, fire source setting, temperature measurement requirements, and qualified indicators, etc. Finally, the challenges for development of composite hydrogen storage cylinders and compressed hydrogen storage systems in China were proposed.
Evaluation of Brittle Crack Arrest Toughness for Highly-Irradiated Reactor Pressure Vessel Steels
Authors: Iwata Keiko , Hata Kuniki , Tobita Tohru , Hirota Takatoshi , Takamizawa Hisashi , Chimi Yasuhiro , Nishiyama Yutaka
Published: October 2021

The crack arrest fracture toughness, KIa, values for highly-irradiated reactor pressure vessel (RPV) steels are estimated according to the linear relationship between crack arrest toughness reference temperature, TKIa, and the temperature corresponding to a fixed arrest load, equal to 4 kN, TFa4kN, obtained by instrumented Charpy impact test. The relationship between TKIa derived from the instrumented Charpy impact test and fracture toughness reference temperature, To, was expressed as an equation proposed in a previous study. The coefficients in the equation could be fine-tuned to obtain a better fitting curve using the present experimental data and previous KIa data. The KIa curve for RPV;A533B class 1 steels irradiated up to 1.3 × 1020 n/cm2 (E > 1 MeV) was compared with a KIR curve defined in JEAC4206-2016. The KIR curve was always lower than the 1%ile curve of KIa for these irradiated RPV steels. This result indicates that the conservatism of the method defined in JEAC4206-2016 to evaluate KIa using the KIR curve is confirmed for highly-irradiated RPV steels.
Crack Growth Resistance of Actual Pipe Weldments Exposed to a High Pressure Mixture of Hydrogen and Natural Gas
Authors: Benoit Guillaume , Bertheau Denis , Hénaff Gilbert , Alvarez Laurent
Published: October 2021

In a context of reduction of greenhouse gas emission, the development of hydrogen as an energy carrier implies the transport of large quantity of hydrogen gas over long distances. The option of using the existing Natural Gas (NG) network raises the question of the amount of hydrogen gas that can be blended with natural gas while ensuring safe operating conditions for the pipe, especially in presence of crack-like defects. With this respect, the present study was undertaken in order to get a first assessment of the impact of the hydrogen gas content in natural gas on the crack growth resistance of pipeline girth welds. With this aim, fracture toughness and fatigue crack propagation tests were carried out at RT on a servo-hydraulic machine equipped with a pressure vessel. The CT samples used in these tests were extracted from different actual circular welds (respectively 350 and 900 mm pipe diameter, 7 and 13 mm thickness) representative of those present in the network so that the crack plane is located in the joint (Weld Centre Line so far). Two couples of steel and welding process were studied, namely a modern pipe steel L485 (X70) welded by mechanized welding process (GMAW) and a vintage pipe (X60) carbon steel with a manual cellulosic electrode process (SMAW). Two environmental conditions were considered so far, namely representative NG including 9 minor species and a 25%H -NG blend with a total pressure of 8.5 MPa. The fracture toughness for both types of welds results indicate no significant effect of hydrogen on the K values, while the plastic opening and the CTOD values are affected at different degrees. Besides, fatigue crack growth rates are enhanced by more than one order of magnitude in the 25%H -NG mixture in the high ΔK region as compared to NG. Fractographic observations are presented to support these results.
An Assessment of Engineering Knowledge Management Regarding Retention and Maintenance
Authors: Farrell Ronald S. , Ezekoye L. Ike
Published: October 2021

The importance for an organization to retain and maintain business knowledge is well known. As such, there are many knowledge management (KM) resources available including educational materials and tools for general business practices such as enterprise computer and cloud applications. Despite all the available resources, there remain challenges within KM organization strategies and adoption practices that need attention. For instance, author Jay Liebowitz warns in his book, Knowledge Retention: Strategies and Solutions, that organizations are experiencing knowledge bleed as baby boomers retire and younger workers take over the work. The focus of this paper is twofold, (a) evaluate Liebowitz’s warning within the practice of engineering, and (b) assess the challenge of retaining and maintaining engineering expertise for the long term. The authors, each with over forty years of engineering experience, have observed that engineering departments are aware of the benefit of capturing current and legacy knowledge but often fail to do so. Instead, the habitual practice of business as usual remains the default. For instance, the capture of enterprise engineering methodology is attempted only when experienced and seasoned expert engineers are very close to retiring when it is generally too late to be effective, that is if any exit strategy exists at all. In addition, the maintenance of crucial engineering tools, especially those developed in house, relies on very few product line expert engineers with no one to assume the highly technical role upon attrition. A possible consequence of this habitual practice is to frustrate younger workers who are asked to assume an expert’s role too soon and unprepared. This frustration frequently leads young talents in search of competing firms that do a better job with their engineering KM. Instead of ineffective practices, the authors explore strategies for engineering knowledge retention and for putting good practice into place. Additionally, potential benefits to the company are discussed with regards to efficient knowledge capture and the grooming and retention of future expert engineers.
Temperature Dependent Failure Behaviour of Components Containing Crack Fields: An Experimental and Numerical Approach
Authors: Weihe Stefan , Stumpfrock Ludwig , Weber Ulrich , Gauder Patrick , Seidenfuss Michael
Published: October 2021

The indications of a high quantity of cracks from non-destructive testing measurements were determined in a root cause analysis as hydrogen flakes positioned in segregated zones in the base material of pressure vessels of Belgian nuclear power plants. Because of the laminar and quasi-laminar orientations of this hydrogen flakes with an inclination up to 16° to the pressure retaining surface the crack tips undergo predominantly mixed-mode loading conditions under internal pressure and the induced stress and strain fields of the single crack tips influence each other. In a former paper, the failure behavior of crack fields under mixed mode loading conditions was investigated at RT (Room Temperature) and −100°C, the upper shelf and the lower transition phase of the steel 22NiMoCr3-7, respectively. In this paper, the failure behavior of crack fields is investigated for many different levels of material toughness (from to upper shelf to the lower shelf region) on experiments with different artificial manufactured crack fields. Therefore, numerical simulations are carried out with extended micromechanical based damage mechanics models. For the description of ductile failure the Rousselier model is used and the Beremin model to calculate the probability of cleavage fracture. To account the sensitivity for low stress triaxiality damage by shear loading, the damage mechanics model was enhanced with a term to account for damage evolution by shear. For numerical simulations in the transition region of brittle-to-ductile failure a coupled damage mechanics model (enhanced Rousselier & Beremin) will be used. In this paper, the current state of the ongoing research project is presented.
Comparative Assessments of Different Leakage-Rate Models for ATLAS+
Authors: Williams P. T. , Bass B. R. , Dillström P. , Gill P. , Daniels B. , Lammert R. , Wackenhut G.
Published: October 2021

In support of the Euratom research and training program Advanced Structural Integrity Assessment Tools for Safe Long Term Operation (ATLAS+), this paper presents a comparative assessment of both conservative and best-estimate leakage-rate models carried out using the recently-developed Leak Analysis of Piping – OCI (LOCI™) code. Studies are reported comparing the LOCI™ results with the XPIPE™ code developed by Materialprüfungsanstalt (MPA) Universität Stuttgart and a new leakage-rate code developed by Jacobs. All participants in this study are members of the ATLAS+ consortium.

In the context of a leak-before-break (LBB) assessment where emphasis is placed on the detection of small leakage rates, the distinction between conservative and best-estimate models can be very important. This classification can provide guidance on where these models can be appropriately applied in terms of understanding margins and uncertainties. Country-specific regulatory requirements for an LBB assessment can also play an important role in model selection. A conservative leakage-rate model is required to consistently underestimate the actual leakage rate and is typically applied in deterministic procedures. A best-estimate leakage-rate model places greater emphasis on predictive accuracy. In a probabilistic framework, the model’s estimated solutions can serve as a measure of central tendency (mean, median, or mode) for a prescribed statistical distribution characterizing the uncertainties in leakage-rate predictions.

In a more general probabilistic analysis, model inputs and their associated statistical distributions are sometimes proposed which have conservative values for parameters to ensure that some extreme cases are not underrepresented. However, conservatism can lead to overestimates of the probability of leakage or rupture and, thereby, invalidate the model. Moreover, conservatism at a subsystem level could potentially become non-conservative when implemented at the system or framework level.
Development and Validation of Radiant Heat Systems to Test RAM Packages Under Non-Uniform Thermal Environments
Authors: Mendoza Hector , Gill Walter , Figueroa Victor G. , Sanborn Scott
Published: October 2021

Certification of radioactive material (RAM) packages for storage and transportation requires multiple tiers of testing that simulate accident conditions in order to assure safety. One of these key testing aspects focuses on container response to thermal insults when a package includes materials that decompose, combust, or change phase between −40 °C and 800 °C. Thermal insult for RAM packages during testing can be imposed from a direct pool fire, but it can also be imposed using a furnace or a radiant heat system. Depending on variables such as scale, heating rates, desired environment, intended diagnostics, cost, etc., each of the different methods possess their advantages and disadvantages. While a direct fire can be the closest method to represent a plausible insult, incorporating comprehensive diagnostics in a controlled fire test can pose various challenges due to the nature of a fire. Radiant heat setups can instead be used to impose a comparable heat flux on a test specimen in a controlled manner that allows more comprehensive diagnostics. With radiant heat setups, however, challenges can arise when attempting to impose desired non-uniform heat fluxes that would account for specimen orientation and position in a simulated accident scenario. This work describes the development, implementation, and validation of a series of techniques used by Sandia National Laboratories to create prescribed non-uniform thermal environments using radiant heat sources for RAM packages as large as a 55-gallon drum.
Validation of Modern Finite Analysis Methods for Glassy Polymers Using Historical Studies
Authors: Kemper Bart
Published: October 2021

The current method for designing acrylic pressure vessel components relies upon an empirical method developed through experimentation during the 1960’s and 70’s. The method is detailed in ASME PVHO-1, Safety Standard for Pressure Vessels for Human Occupancy. One of the factors restricting the design methodology to experimental correlation was the structural dimensions. Thick wall pressure vessel geometry prevented the use of conventional Section VIII pressure vessel calculations, which assumes thin wall pressure vessels. Early Finite Element Analysis (FEA) models of acrylic windows could not be validated through experimentation. This was attributed to the viscoelastic properties of acrylics. The resulting experiment-based PVHO-1 Safety Standard has a proven safety record but is not readily updated. This paper re-examines some of the work used to develop PVHO-1 to demonstrate modern nonlinear FEA and V&V techniques can predict the results of the original work. In doing so, this work also validates the use of FEA going forward for Design By Analysis (DBA) using Verification and Validation (V&V) for newer materials, shapes, and applications.
Explicit Finite Element Fatigue Crack Growth Analysis of An Instrumentation Ring Under Thermal Transient Loading
Authors: Selling Joshua B. B. , Holliday James E. , Damiani Thomas M.
Published: October 2021

ASME PVP conference papers from 2007 and 2008 (References [1] and [2]) discuss fatigue analyses related to 304 stainless steel instrumentation spacer rings (rings) that had cracked while installed in a thermal fatigue test loop. The rings contain circular radial penetrations extending through the ring that allow access for instrumentation probes to monitor the fluid temperature and pressure. Routine inspection of the test loop revealed actively growing cracks in each port that appeared to start near the inner diameter (ID) of the ring. In this work, three-dimensional finite element analysis (FEA) thermal and fully-elastic structural Abaqus models were made from the available test measurements. The commercial crack modeling software, Franc3D, was used to complete an M-integral based fatigue crack growth (FCG) analysis. An assumed initial crack was inserted in a single port of interest near the ID of the FEA model. The crack was explicitly grown in an automated fashion over iterative growth steps. The explicit FCG analysis was able to match the directional path and final flaw size seen in the destructive evaluation metallographic images of the rings with the assumed input parameters exceptionally well, including shifting directions and splitting the crack without need of user input. The results of this work indicate that an explicit FCG analysis is feasible for a non-trivial thermal-structural problem.
Qualification Challenges for Additive Manufacturing in High Temperature Nuclear Applications
Authors: McMurtrey Michael , Messner Mark
Published: October 2021

There is an increasing interest in using additive manufacturing for structural materials, including pressure-retaining components. This requires that the manufacturing methods be included in Codes and Standards, such as the Boiler Pressure Vessel Code. This work is already moving forward with the development of a Section III Division 1 Code Case to include 316 stainless steel that is manufactured using powder bed fusion, an additive manufacturing technique. However, Code Cases will become significantly more challenging when time-dependent properties must be considered, such as in Section III, Division 5. Section III, Division 5 requires design models based on creep as well as creep-fatigue interaction. Testing for this is time intensive and costly. Additive manufacturing properties are a result of feedstock material as well as processing methods/parameters. The individual machines take what used to be centralized material fabrication (into large plates of castings) and spread the process out to many separate facilities. This decentralized fabrication, paired with the rapidly changing landscape of additive techniques and equipment manufacturers, has created difficulty in quality control and producing code cases. For low-temperature code cases, this has been circumvented by requiring witness specimens that meet specified property requirements. Additional witness specimens to cover time-dependent properties would significantly increase the cost and delay processes, so similar methods may not be effective for high temperature applications. This paper covers fabrication and modeling/simulation challenges associated with qualification of additive manufacturing processes for high-temperature structural materials.
Application of Leak-Before-Break to Small Diameter Stainless Steel Piping in PWRs
Authors: Cofie Nathaniel G. , Dedhia Dilip , Shim Do Jun
Published: October 2021

Traditionally, leak-before-break (LBB) analysis has been applied to large diameter main loop piping in pressurized water reactors (PWRs) to address the dynamic effects of pipe break required by the General Design Criteria 4, Appendix A of 10CFR50.

Recently, however, LBB is being sought for Class 1 pressure boundary piping systems such as the safety injection and residual heat removal systems which have small diameter piping (12-inch NPS and less) to mitigate the effect of dynamic loads on reactor internals and other concerns. In NUREG-1061, Volume 3, it is stated that LBB approach means the application of fracture mechanics to demonstrate that high energy fluid piping is unlikely to experience double-ended ruptures or their equivalent as longitudinal or diagonal splits. In application of traditional LBB to large diameter piping, only circumferential flaws are considered since it is generally believed that leaks through axial flaws for such piping are relatively large in comparison to circumferential flaws. However, this may not be the case for small diameter piping.

This paper examines the application of LBB to small diameter stainless steel piping in PWRs by determining the leak rate requirements to meet the criteria specified in SRP 3.6.3 and NUREG-1061, Volume 3 for both circumferential and axial flaws.
Effect of Hydrogen on Tensile Properties of 304L Stainless Steel at Cryogenic Temperatures
Authors: Merkel Daniel R. , Nickerson Ethan K. , Seffens Robert J. , Simmons Kevin L. , San Marchi Chris , Kagay Brian J. , Ronevich Joseph A.
Published: October 2021

Safe and efficient hydrogen storage and distribution are key attributes to realizing hydrogen as an alternative energy carrier to traditional fossil fuels. To this end, cryogenic liquid and cryo-compressed gaseous hydrogen are considered high energy density alternatives to ambient temperature gas. However, these alternatives have significant material demands to overcome extreme temperature (20 K) and pressure (700 bar) as well as hydrogen effects. Austenitic stainless steels are widely used for cryogenic pressure vessels owing to relatively high ductility even at 4 K. However, the influence of hydrogen on mechanical properties at cryogenic temperatures has rarely been studied. In this study, the tensile properties of 304L austenitic stainless steel with internal hydrogen were evaluated at 20 K, 77 K, and 113 K. Test specimens were saturated with internal hydrogen to concentration of 140 wtppm in a high pressure environment at elevated temperature, a process called thermal precharging. While lower temperature in known to increase strength properties and reduced elongation at fracture, the presence of internal hydrogen increased both strength and elongation at fracture, but reduced ductility. Magnetic evaluation of the uniformly strained region of the test specimens suggest that hydrogen mitigates the strain-induced transformation to α’-martensite. Brittle fracture features and secondary cracking indicative of hydrogen embrittlement were observed on the fracture surfaces of hydrogen-precharged specimens, which is consistent with the loss of ductility.