bluuebunny/crossref_metadata_2025_split huggingface dataset:
Investigations of In-Plane Fluidelastic Instability in a Multi-Span U-Bend Test Rig: Tests in Two-Phase Flow
Authors: Feenstra Paul , Sawadogo Teguewinde , Smith Bruce , Janzen Victor , McLellan Anne , Cothron Helen , Kil Sean 
Published: November 2019

Abstract
Tests to study FluidElastic Instability (FEI) in an array of U-bend tubes were recently completed in the Multi-Span U-Bend (MSUB) test rig at Canadian Nuclear Laboratories (CNL). These tests were sponsored by the Electric Power Research Institute (EPRI) and were designed to study In-Plane (IP or streamwise) FEI of steam generator tubes in two-phase cross flow. This instability mechanism was first observed in previous research tests by Atomic Energy of Canada Limited (AECL). Although AECL planned additional research into IP FEI, this mechanism was not thought to be a serious practical concern until it recently caused severe damage to tubes in a new replacement steam-generator. The MSUB tests were conducted both with flows of air and two-phase liquid/vapour Refrigerant 134a. With 22 flexible U-bend tubes supported by a configurable flat-bar arrangement, the tests were focused on the effects of support geometry and tube-to-support interaction. Data was recorded from 33 dynamic signals from accelerometers, displacement probes, force transducers, and void-fraction probes. The paper describes the experimental test setup and reviews some of the initial test results and their implications for steam-generator users and researchers. Tests with two-phase Freon refrigerant (R-134a) are presented here.
Technical Basis for Maximum Allowable Indentation Depths in HDPE Pipes for Proposed ASME Section III Code Case on Alternative Requirements to Appendix XXVI for Inspection and Repair
Authors: Scarth Douglas , Krishnaswamy Prabhat , Rush Phillip , Munson Douglas 
Published: November 2019

Abstract
Mandatory Appendix XXVI of Section III of the ASME B&PV Code contains rules for the construction of Class 3 polyethylene pressure piping systems. The scope is limited to buried portions of Class 3 service water or buried portions of Class 3 cooling water systems, consisting of PE4710 High Density Polyethylene (HDPE) materials. The minimum Pennsylvania Notched Test (PENT) rating for the HDPE material is 2,000 hours. Appendix XXVI contains acceptance standards for the maximum allowable depths of gouges, cuts or other surface conditions that are characterized as indentations. The acceptance standards are considered to be very restrictive, in particular for large diameter HDPE pipes. Less restrictive maximum allowable indentation depths for pipes with a minimum PENT rating of 2,000 hours were developed based on use of results from tests performed on pressurized HDPE pipes containing flaws in the parent material. These maximum allowable indentation depths were implemented into the new Section III Code Case N-891 on alternative requirements to Appendix XXVI for inspection and repair. The technical basis for the maximum allowable indentation depths is described in this paper.
A Flexible Tool for Modeling Thermal Loading in Printed Circuit Heat Exchangers
Authors: Jentz Ian W. , Anderson Mark H. 
Published: November 2019

Abstract
Compact and thermally efficient, Printed Circuit Heat Exchangers (PCHEs) are favored for use in next generation nuclear power plants. Containing thousands of small working fluid channels distributed in a solid 316H or 800H block, PCHEs can handle high pressures and operating temperatures required by generation IV nuclear plants. Advanced nuclear reactors will require the certification of a nuclear service PCHE design by construction codes, such as BPVC Sec-3. Compliance with this standard requires Creep fatigue and ratcheting analyses be performed for expected loading service transients. Realizing this analysis in PCHEs requires a simplified and flexible modeling approach that can be run over dozens of transients for multiple heat exchanger geometries. The Rich Environment Heatex-changer Transient (REHT) model is being developed to provide a full PCHE model needed to properly resolve Sec-3 loading conditions without the complexity inherent in resolving all facets of the PCHE geometry. This work introduces the thermohydraulic model that is the core of the REHT model. An example problem modeling an experimental scaled PCHE is presented. The ability of the REHT model to simulate fluid flow through a directional varying microchannel core of two heat exchanging streams is demonstrated. The REHT model resolves PCHE thermohydraulics using simple model definitions and minimum computational overhead, making it an ideal design tool.
Fitness-for-Service Assessment of Externally Corroded Convection Coil Tube
Authors: van Zyl Gys , Al-Salmi Abdullatif 
Published: November 2019

Abstract
During inspection of a heating coil in the convection section of a steam reformer, significant thickness loss due to external corrosion was discovered in a large number of tubes.
In order to optimize the scope of repairs and ensure further safe operation, a level 3 fitness-for-service and remaining life analysis were performed in accordance with API-579.
This paper will describe the fitness-for-service assessment that was performed, first using an idealized geometry, and thereafter using the actual corroded geometry of a removed tube. The procedure used to estimate the remaining life of the damaged coil will also be presented.
New Model for Ductile Rupture Under Cyclic Loading Conditions
Authors: Remmal Al Mahdi , Marie Stéphane , Leblond Jean-Baptiste 
Published: November 2019

Abstract
Experiments have shown that ductile failure occurs sooner under cyclic loading conditions than under monotone ones. This reduction of ductility probably arises from an effect called “ratcheting of the porosity” that consists of a continued increase of the mean porosity during each cycle with the number of cycles. Improved micromechanical simulations confirmed this interpretation. The same work also contained a proof that Gurson’s classical model for porous ductile materials does not predict any ratcheting of the porosity. In a recent work [6], the authors proposed a Gurson-type “layer model” better fit than Gurson’s original one for the description of the ductile behavior under cyclic loading conditions, using the theory of sequential limit analysis. A very good agreement was obtained between the model predictions and the results of the micromechanical simulations for a rigid-hardenable material. However, the ratcheting of the porosity is a consequence of both hardening and elasticity, and sequential limit analysis is strictly applicable in the absence of elasticity. In this work, we make a proposal to take into account elasticity in the layer model through the definition of a new objective stress rate leading to an accurate expression of the porosity rate accounting for both elasticity and plasticity. This proposal is assessed through comparison of its predictions with the results of some new micromechanical simulations performed for matrices exhibiting both elasticity and all types of hardening: isotropic, kinematic and mixed, to better comply with the hypothesis made to derive the model.
Critical Review of Strain Measures for Characterisation of Fatigue Damage in ASME Section III Fatigue Assessments
Authors: Leary Daniel , Currie Chris , Wright Keith 
Published: November 2019

Abstract
Rules for fatigue evaluation of nuclear pressure vessels and piping components are provided in Subsection NB of Section III of the ASME code. The code prescribed fatigue procedure requires the comparison of an alternating stress amplitude with fatigue allowables (design fatigue curves), usually derived through uniaxial specimen testing. For elastic assessments of multiaxial loading, typical from thermal shocks, a Tresca stress is used to characterise the stress field into a single effective stress measure for comparison with ASME fatigue allowables. For nonlinear elastic-plastic assessments, Appendix XIII-3440(b) of Section III specifies that “the numerically maximum principal total strain range” (interpreted as Maximum Total Principal (MTP) strain range) should be used for comparison with fatigue allowables.
Two alternative methods for the characterisation of multiaxial strain fields are presented in the ASME code. Section VIII Division 2 provides alternative rules for the construction of pressure vessels, with Part 5 specifying the use of a Von Mises based Effective Strain Range (ESR) for elastic-plastic analysis. Section III Division 5 Subsection NBB provides rules for the assessment of components at elevated temperatures, also specifying the use of a Von Mises based Equivalent Total Strain Range (ETSR) measure. The two alternative strain measures are differentiated by their treatment of the elastic strain contribution. In the ESR method an equivalent elastic strain is calculated and summated with the plastic strain component. In the ETSR method the total strain (elastic plus plastic) is used thus evaluating the elastic and plastic contributions simultaneously. More complex critical plane approaches have also been proposed in recent years to better characterise multiaxial loading conditions.
This paper presents a comparison of the various ASME specified strain measures and simplified critical plane approaches for fatigue evaluation of complex multiaxial loading. In support of this comparison, predictions of initiation lives to 0.254 mm defect in the stepped pipe specimen reported in PVP2004-2748 are provided to quantify the additional conservatism contained in elastic-plastic fatigue assessments of nuclear components. Predictions use the methodology presented in the companion paper PVP2019-93847 for the generation of short crack fatigue curves and the associated modification to environmental enhancement factors.
It is concluded that use of the ASME specified strain measures, in conjunction with lower bound stress-strain data, conservatively underestimate the initiation life to a 0.254 mm defect by a factor of four for the example considered. However, use of more complex critical plane strain measures were observed to provide significant improvement in prediction accuracy of elastic-plastic fatigue evaluations.
Reactor Vessel Hazard Assessment Case Study
Authors: Edel Matthew , Van Zyl Gys , Atarji Abdulrahman 
Published: November 2019

Abstract
Operation of a multi-tubular reactor vessel includes some inherent risks and potential hazards. Multi-tubular reactors tend to be large vessels that contain hydrocarbons under pressure. Some potential hazards that may ensue from potential vessel failure include fragments (i.e., debris), blast loads, and heat.
This paper involves the discussion of a case study of a multi-tubular reactor vessel that sustained corrosion cracks on full penetration groove welds near the top and bottom heads. A hazard analysis is conducted that considered various potential scenarios associated with an accidental head failure. The structural response of the vessel is determined using mechanics of materials-based finite element analysis (FEA) models. Blast loads emanating from the vessel as the pressurized water/steam escaped the vessel through a failed opening are estimated. Projectile trajectories for fragments of weldment launched from the failed circumferential weld are also calculated. The results of the models lead to recommended safe standoff distances and potential mitigation options.
Consideration on Fatigue Crack Growth Thresholds Under Negative Stress Ratio
Authors: Hasegawa Kunio , Usami Saburo , Lacroix Valery 
Published: November 2019

Abstract
Fatigue crack growth thresholds ΔKth are provided by several fitness-for-service (FFS) codes. When evaluating cracked components subjected to cyclic loading, maximum stress intensity factor Kmax and/or minimum stress intensity factor Kmin are required. However, the definitions of the thresholds ΔKth under negative stress ratio R are not clearly written, except for BS (British Standards) 7910. In addition, the ΔKth are given by constant values under negative R. Fatigue crack growth rates under negative stress ratio is recommended to use maximum stress intensity factor Kmax by ASTM (American Society of Testing and Materials) E 647, because of the Kmax being close to crack driving force. Therefore, it deems that the ΔKth under negative R seems to be Kmax.
This paper shows that the Kmax converted by the ΔKth are not constant values under negative R based on the survey of experimental data. The Kmax decreases with decreasing the stress ratio R. Therefore, the ΔKth for the FFS codes are less conservative. As experimental data under negative stress ratio R were taken by Kmax – Kmin, the definition of the threshold ΔKth is benefit to use Kmax – Kmin, instead of Kmax.
Low-Cycle Fatigue of Pipe Components: Markl’s Method Revisited
Authors: Pei Xianjun , Dong Pingsha , Song Shaopin 
Published: November 2019

Abstract
In the 1950’s Markl et al. conducted numerous fatigue test of welded piping components that were later used to develop the ASME B31 and other piping design codes. To analyze low cycle fatigue data, Markl proposed an extrapolation method to obtain the pseudo-elastic stress for fatigue data analysis. In this paper, this extrapolation method is revisited to figure out its underlining mechanism, application scope and limitation. Two sets of fatigue data representing 4 point bending and cantilever bending condition are analyzed to support the study. A structural strain method is then proposed as an improvement and generalization of Markl’s approach, which can correlate large amount weldment fatigue data in both low-cycle and high-cycle regime by defining an equivalent structural strain parameter.
Evaluation of the Fatigue Strength of Notched Geometries Using a Microstructural Model and Generative Algorithms
Authors: Balbín Molina J. A. , Larrosa N. O. , Chaves V. 
Published: November 2019

Abstract
In this work, the assessment of a short crack emanating from arbitrarily shaped notches under Mode I loading is done. A parametric algorithmic tool is used to create a wide range of different two dimensional notch shapes for the evaluation of notch fatigue strength by means of the Distributed Dislocation Technique. Comparisons between V-notches, U-notches and semi-elliptical notches establishing similar geometrical parametric relations are shown, so that the simplicity and versatility of the designed tool is demonstrated. This useful properties and advantages make this tool applicable to industrial problems such as the modelling and assessment of the effect of corrosion pits on fatigue strength.
Technical Basis for Master Curve for Fatigue Crack Growth of Ferritic Steels in High-Pressure Gaseous Hydrogen in ASME Section VIII-3 Code
Authors: San Marchi Chris , Ronevich Joseph , Bortot Paolo , Wada Yoru , Felbaum John , Rana Mahendra 
Published: November 2019

Abstract
The design of pressure vessels for high-pressure gaseous hydrogen service per ASME Boiler and Pressure Vessel Code Section VIII Division 3 requires measurement of fatigue crack growth rates in situ in gaseous hydrogen at the design pressure. These measurements are challenging and only a few laboratories in the world are equipped to make these measurements, especially in gaseous hydrogen at pressure in excess of 100 MPa. However, sufficient data is now available to show that common pressure vessel steels (e.g., SA-372 and SA-723) show similar fatigue crack growth rates when the maximum applied stress intensity factor is significantly less than the elastic-plastic fracture toughness. Indeed, the measured rates are sufficiently consistent that a master curve for fatigue crack growth in gaseous hydrogen can be established for steels with tensile strength less than 915 MPa. In this overview, published reports of fatigue crack growth rate data in gaseous hydrogen are reviewed. These data are used to formulate a two-part master curve for fatigue crack growth in high-pressure (106 MPa) gaseous hydrogen, following the classic power-law formulation for fatigue crack growth and a term that accounts for the loading ratio (R). The bounds on applicability of the master curve are discussed, including the relationship between hydrogen-assisted fracture and tensile strength of these steels. These data have been used in developing ASME VIII-3 Code Case 2938. Additionally, a phenomenological term for pressure can be added to the master curve and it is shown that the same master curve formulation captures the behavior of pressure vessel and pipeline steels at significantly lower pressure.
Development of an Apparatus for Chloride Induced Stress Corrosion Cracking Test Using Immersion Method With Constant Displacement Condition
Authors: Jeong Jae-Yoon , Lee Myeong-Woo , Kim Yun-Jae , Sindelar Robert , Duncan Andrew 
Published: November 2019

Abstract
This paper presents a new test method for assessing chloride induced stress corrosion cracking occurred in metal canisters used for storing spent nuclear fuels. The material applied to experiment is austenitic stainless steel, SS304 similarly used on manufacturing canisters and the experiment is carried out with immersing a compact tension specimen to chloride solution made up with artificial sea salt. Constant displacement condition using bolt tightening is applied to the test and a load is measured as a function of time using a load cell. Five specimens are used for the experiment at temperature of 50 °C for several months and stress intensity factor is calculated through the measured relaxed load and crack length on fractured surface of the specimen. Crack growth rate is presented in terms of test periods and consequently this apparatus suggests a method for evaluating structural integrity of chloride stress corrosion cracking.
Inconel X-750 Spacer Fitness-for-Service
Authors: Lau Winnie , Scarth Douglas , Doddihal Preeti 
Published: November 2019

Abstract
The CANDU1 (CANada Deuterium Uranium) reactor core consists of 380–480 horizontal Zr-Nb pressure tubes, which support fuel bundles and provide pressurized heavy water cooling. The pressure tubes are supported by fuel channel annulus spacers, which maintain the gap between the hot pressure tube and colder calandria tube while providing a means of leak detection through the annulus gas system. Research and testing in this area have shown that spacer material degradation in later life operation could impact the ability of the component to meet its design requirements. This paper presents a fitness-for-service strategy that could be utilized in demonstrating continued safe operation of these components. Fitness-for-service is based on analysis of crush tests on ex-service spacers to determine the load carrying capacity projected into the future and endurance tests to determine fatigue life. This paper describes these technical approaches and their application in fitness-for-service evaluation of spacers in CANDU operating plants to satisfy requirements for an annulus spacer surveillance program under Clause 12.5 of the CSA Standard N285.4-14.
Investigation of Relationship Between Microhardness and Charpy Impact Energy for Temper Bead Welding Qualification: Part 1
Authors: Smith Boeing , Ramirez Antonio J. , McCracken Steven L. , Tate Stephen 
Published: November 2019

Abstract
Temper bead (TB) welding is often used as an alternative to post weld heat treatment (PWHT) for repair of pressure vessels and piping in the nuclear power industry. Historically, qualification of TB welding procedures has employed the Charpy V-notch test to ensure acceptable heat-affected-zone (HAZ) impact properties. The 2004 Edition of ASME Section IX provided a new provision in QW-290 that allows temper bead qualification using a peak hardness criterion. The peak hardness provision is appropriate for industries such as oil and gas, where peak allowable hardness is specified to ensure adequate resistance to sulfide stress cracking in sour service environments. However, a peak hardness criterion is not appropriate where impact properties are specified for resistance to brittle fracture during low temperature conditions that can occur during certain postulated accident scenarios at a nuclear power plant.
Work at the Electric Power Research Institute (EPRI) and The Ohio State University (OSU) show that a hardness drop protocol can be used to demonstrate acceptable impact properties in the HAZ of a temper bead weld. This paper presents a quantitative correlation between hardness measurements and HAZ microstructures with presumed optimum impact properties using a hardness drop approach. The overarching goal is to develop a hardness test protocol for temper bead weld procedure qualification for applications where impact properties are specified.
Integrated Smart Seismic Risks Management
Authors: Ciucci Mariano , Marino Alessandra , Paolacci Fabrizio , Bursi Oreste S. 
Published: November 2019

Abstract
Recent events outlined the relevance of the interactions between industrial and natural hazards (NATECH) particularly for that concern seismic risk. EU regulation, namely Directive 2012/18/EU, among its new elements explicitly requires the analysis of NATECH hazards. The development of a risk analysis methodology for major hazard industrial plants allows the individuation of critical elements of the plants with regard to seismic actions. The following implementation of smart technologies (sensors, actuators, innovative systems for seismic protection) to the critical elements allows a relevant reduction of major hazards and related consequences.
Ratcheting due to Thermal Stratification
Authors: Adibi-Asl R. , O’Kane D. , Chen E. 
Published: November 2019

Abstract
Thermal ratcheting is required to be checked by most of the piping design codes, specifically the ASME B&PV Code. For cases where the variation of temperature distribution is not uniform, the existing ratchet check methodology for piping is inadequate and therefore the finite element analysis (FEA) is often used to perform ratchet checks. Thermal stratification, in which cold and hot fluid flows are layered in a relatively steady state condition, is a good example of non-linear/non-uniform temperature distribution across the pipe.
This paper develops straightforward equations to address thermal stratification in piping. Finite element analysis is used to benchmark the results.
A Design Guideline for Random Excitation Forces due to Two-Phase Cross Flow in Tube Bundles
Authors: Taylor Colette E. , Pettigrew Michel J. 
Published: November 2019

Abstract
This paper re-examines the available experimental data to investigate the random excitation forces that affect tube bundles exposed to two-phase cross flow. Much of the experimental data generated over the past four decades has been gathered in an attempt to understand the parametric dependence of the random two-phase forces. The data includes air-water, steam-water and various Freons used in a variety of test sections with either strain gauges to measure the tube amplitude or force tranducers to measure the reaction forces. A review of previous work in this area finds that some authors claim a strong flow regime dependence, while others suggest that this dependence is weak. This work takes a detailed look at this discrepancy and finds that a single design guideline does not adequately bound all flow regimes. As a result, two dimensionless upper bounds are proposed.