bluuebunny/crossref_metadata_2025 huggingface dataset:
Analysis of Residual Stress Distribution Characteristics at Nozzle Weld in Pressure Vessel and Pipe Components
Authors: Song Shaopin , Dong Pingsha
Published: November 2019

In order to achieve a better understanding of residual stress distribution characteristics associated with nozzle welds, this paper focuses on the identification of key parameters that contribute to the development of through-thickness membrane and bending components. This is because, as demonstrated in recent publications by the same authors (Song and Dong, 2016–2017), statically equivalent membrane and bending content in a given residual stress distribution play a far more critical role in fracture driving force calculation in Fitness-for-Service (FFS) assessment. To do so, a recent detailed investigation to residual stress distributions in nozzle welds is presented in this paper, covering nozzle radius to wall thickness ratio from 2 to 50, heat input from 400 J/mm to 1000 J/mm, weld joint types including set-in nozzle weld and set-on nozzle weld. By means of a residual stress decomposition technique, controlling parameters that govern through-thickness membrane and bending stresses have been identified, which are nozzle radius to wall thickness ratio (r/t) and linear heat input parameter (Q). Then, a unified functional form for representing through-thickness residual stress profile in nozzle weld is presented for supporting fitness for service assessment, e.g., by means of API 579-RP.
Improving Fatigue Properties of High Pressure Tubes in TP316L Compared to Sandvik HP120
Authors: Froböse Thomas
Published: November 2019

High pressure tubes are used in many industrial applications. Examples are “waterjet cutting” and “hydrogen fuel handling”. In “high pressure application’s”, pressures are handled around 800 bar. The tube dimension 9,53 mm × 3,16 mm is a typical “high pressure” dimension. This dimension can be found in many “waterjet cutting machines”.

Tube is a important component in any “high pressure application”. Tubes are typically used in a fatigue environment. The tube needs to survive a certain number of pressure cycles. It is important to increase the number of “cycles” to extend the lifetime of the tube and as a result, the lifetime of the equipment. Higher lifetime rates greatly reduce planned maintenance and reduce risk of unplanned equipment breakdowns.

The investigation and development to increase the fatigue properties on existing grades (mainly TP316L is this example) is a foundation to the development of a “new high pressure grade” with specific mechanical Properties.

In order to prove the fatigue properties fatigue tests have been carried out under synchronized conditions, using different tubes in comparison grades. In the production of seamless tubes, there are different production methods to create different material properties. Combinations of these methods for each grade are tested and results measured relating to grain size, defect level and surface surface condition are recorded.

The test tubes are produced in different production flow with different surface conditions to develop a comparison between surface conditions and the resulting fatigue related results. Two different grades TP316L and HP120 have been used to prove the test results in combination to material grades.

Different tube samples run on a fatigue test bench. The test pressure is set at 3.000 bar with a sinus curve at 6 Hz.

The results give a development guideline to reach the most advanced tube product for fatigue related applications.
Full Structural Weld Overlay on a Super Emergency Feedwater Nozzle at the Dukovany Nuclear Power Plant
Authors: McCracken Steven L. , Palán Marek , Mlynář Pavel , Mohr Nicholas
Published: November 2019

A weld overlay (WOL) following the general guidelines of ASME Code Case N-740-2 was successfully installed in March of 2018 on a dissimilar metal weld joining the super emergency feedwater1 piping to steam generator (SG) at the Dukovany nuclear power plant (NPP) in the Czech Republic. The repair was necessary due to stress corrosion cracking detected in the super emergency feedwater nozzle to safe-end dissimilar metal weld. This was the first WOL installed in the Czech Republic and represents a significant step towards further acceptance of this proven repair technology in Europe. The WOL repair approach was accepted by the Czech regulator, and two different inspection agencies, following successful mockup demonstrations, welding procedure qualification, nondestructive examination demonstrations and weld residual stress analyses. This paper describes the preparatory work as well as field deployment of WOLs in the Czech Republic.
Prediction of Flow-Accelerated Corrosion/Erosion in High-Speed Ejectors Using a CFD Model
Authors: Das Saurish , Sarkar Suranjan , Lee Gary H. , Junxiong Ong
Published: November 2019

In high-velocity ejector systems containing liquid droplets, ejector walls are sometimes damaged by flow-accelerated corrosion/erosion. Velocity, droplet size, impact angle etc. are the most important parameters affecting flow-accelerated (FA) corrosion/erosion. In our plant operation, we had experienced FA corrosion/erosion and consequent failure even with very low impact angle. To understand the leak/ failure, we have adopted the Euler-Euler multiphase model-based CFD approach. In the Euler-Euler multiphase model, the liquid droplets are modelled as dispersed phase while the gas-steam is modelled as a continuous phase. To capture the droplet dynamics very accurately, appropriate correlations for drag, lift and wall lubrication force have been chosen. In CFD simulations we have observed liquid film formation at the ejector wall. The liquid film moves along the ejector wall creates a very high wall shear-stress. In the location of high wall shear-stress, one can expect high FA corrosion/erosion and consequent leak. Qualitative comparison of the X-ray image of the actual equipment with the CFD results for wall-shear stress shows very good agreement in terms of predicting leak location. Moreover, we have varied the droplet size and the liquid fraction in the upstream of the ejector. Qualitatively we have observed that with increase in droplet size the material removal rate increases, however, the affected area of the leak decreases. The more liquid in the system increases the wall-shear stress very rapidly. The present CFD model is useful for predicting the leak-prone location and taking predictive actions (e.g. cladding the wall with a high-grade material).
The Evolution of Bulged Areas in the Cylindrical Section of Coke Drums
Authors: Araque Egler , Love Darren , Park Stephen , Rutt Daryl , Moret Tapia Armando , Clark Rick
Published: November 2019

In recent years the understanding of the relationship between drum damage and bulge sharpness has improved significantly. The authors of this paper developed a new parameter called bulge sharpness and have previously shown the relationship between sharpness and observed damage. Further to this study, the authors have exhaustively studied the evolution of stress cracking (elephant skin) on mid-course bulges and have estimated the likelihood of finding a particular type of surface damage based on the observed sharpness levels. This correlation has led to a proposed scale to categorize stress cracking into three levels: minor, intermediate, and significant. In addition, the progression of bulge sharpness over time was analyzed and it was determined through statistical modeling that bulge sharpness can have a range of rates of change or sharpness growth rates: low, medium, and high. These sharpness growth rates were subsequently studied and their relationship with overall cycle times analyzed. The study also shows that individual coke drums can experience different sharpness growth rates and there can be a distribution of these rates. To determine when repairs should be conducted, coke drum operators must consider the expected operational run. While the random nature of coke drum damage can defy such targets, bulge sharpness growth assessments can be used to better define when repairs should be conducted. Understanding current bulge sharpness levels, year-over-year sharpness growth rates and their distribution, can significantly assist in targeting areas of concern for optimized repair strategies and can also be used to avoid unnecessary repairs.
Flaw Evaluation Procedure for Cast Austenitic Stainless Steel Materials Using a Newly Developed Statistical Thermal Aging Model
Authors: Uddin M. , Sallaberry C. , Wilkowski G.
Published: November 2019

Thermal embrittlement of some cast austenitic stainless steels (CASS) occurs at reactor operating temperatures can lead to a reduction in the fracture toughness and increase in strength. Some aged CASS materials have the potential to have exceedingly low toughness and also show high variability due to the nature of their microstructure or compositional variation within the casting. Because of their low aged toughness with the variability, flaw evaluations of CASS material need to be done with an understanding of the materials aged condition, especially since most US PWR nuclear plants have been given plant life extensions for 60-year operation, and consideration of further extension to 80 years is underway.

In this paper, a flaw evaluation procedure for CASS materials is presented using a new statistical model developed to predict the toughness of fully aged CASS using the material’s chemical composition. The new statistical model was developed based on the experimental toughness using standard 1T CT specimens (generally in the L-C orientation) at 288C to 320C and chemical compositions of the CF8m CASS materials. While the detail development of the model is beyond the scope of this paper, a brief validation of predicted toughness using chemical compositions is presented in this paper. Using the predicted toughness, a flaw evaluation procedure was developed using the Dimensionless-Plastic-Zone-Parameter (DPZP) analysis to determine when limit-load is applicable and also approximate the elastic-plastic correction factor (Z-factor) that needs to be applied to the limit-load solution to predict the failure stress for CASS pipe and fittings with a circumferential surface crack. Variability within a single casting was also determined from available test results which was included in the procedure to determine Z-factor. The procedure was then validated against several CF8m pipe test results which include various pipe diameters, crack sizes, ferrite contents, failure modes (i.e., limit load or EPFM), etc. The as-developed flaw evaluation procedure was also used to determine the Z-factors for four different pipe diameters for a database of 274 pipe/elbows in US PWR plants (whose chemical compositions were known) — essentially solving 1096 sample problems to understand what range of Z-factors might exists in US PWR plants (for CF8m CASS materials) considering all variations in pipe dimensions, ferrite contents, materials’ toughness, etc. Finally, the applicability of the CF8m-based statistical model for use with CF3 and CF8 CASS materials was also investigated by comparing the predictions with available test results.
Novel Mitigation Technique to Reduce Stress at Pipe Welds Caused by Acoustic Induced Vibrations (AIV)
Authors: Ridens Brandon L. , Simons Sarah B.
Published: November 2019

Within blowdown and pressure relieving systems, a phenomenon known as acoustic induced vibrations (AIV) increases the risk of costly failures at branch connections, pipe supports and other discontinuities downstream of pressure relieving devices. Broadband pressure fluctuations generated during these AIV events lead to elevated stresses at welded connections. Based on recent research, modeling and measuring the effects of AIV in piping systems, it is possible to reduce the dynamic pressure fluctuations that cause AIV closer to the excitation source. This can lead to more cost effective and efficient means of reducing the likelihood of failures caused by AIV.

This paper will discuss the results of full-scale testing of a novel mitigation technique that reduces pressure fluctuations that cause AIV. The reduction in dynamic pressure leads to significant lowering of the overall stresses near the pipe welds at discontinuities. In addition, results indicate that a reduction in dynamic pressure can be obtained with the mitigation technique tested to a level acceptable by current screening methods.
Finite-Element Analysis of Contact Stress at the Bearing Surfaces in Bolted Joints (Effect of Flange Bolt Shape and Dimensions)
Authors: Shirakawa Atsushi , Sawa Toshiyuki
Published: November 2019

A higher bolt preload is desirable for higher integrity of bolted joints. However, the bearing surface in the joints could be permanently deformed under a higher preload and the bolt preload decreases with an increase of permanent deformation. Various materials are used as clamped parts, so the permanent plastic deformation should be examined for each material clamped parts. In addition, the critical contact stresses should be examined for various clamped materials. In the previous paper, it was found that the relationship between the contact stress when the plastic deformation initiated, and the compressive proof stress of the clamped parts is linear. However, this conclusion was due to the specific bolt shape and dimensions. In the present paper, the effects of shape and dimensions of bolt head on the contact stress and deformation are examined. This applies to normal and undercut type bolts with sloped bearing surfaces. FEM calculations were used and the clamped part materials were steel and aluminum alloy. Also, a new contact area ratio at the bearing surface is defined and investigated because the nominal contact area is different from the actual contact area when the bolt bearing surface is sloped. Finally, discussion is made on an appropriate contact area, and critical contact stress at the bearing surface as well as suitable bolt shape and bolt head dimensions.
A Case Study: A Systems Approach for 20ksi Equipment Qualification
Authors: Raney James B. , Walz Gregg , Kaminski Dennis
Published: November 2019

Beginning in August 2013, Anadarko Petroleum formed the “20A Project Initiative” for qualifying 20 ksi equipment for a Deepwater Gulf of Mexico (GoM) development. This paper will cover the systems approach used for the qualification (verification, validation and quality) of a system of components, including sub-assemblies and assemblies that are required for a 20 ksi development. The systems approach begins with the framework and management of this framework inside the overall development process. The systems approach categorizes each component by mode of operation (many pieces of equipment are used in multiple operational modes). These modes of operation are Drilling, Completions, Production and Intervention, and are the engineering systems used to manage the qualification of over 200 components to industry standards and U.S. government requirements. The functional requirements for each component are defined and vendors selected. Each component is then stewarded through a project-management process for design, verification, validation and quality. This process culminates with the integration of these components back into a system that can be qualified for use in an HPHT environment. This paper addresses the submittal to regulatory authority for approval to use the newly developed and qualified 20 ksi equipment for a deepwater GoM development.

This project ends in 2019. This six-year development journey presented challenges and achieved breakthrough technologies for the industry. This journey, its organizational approach using systems engineering techniques and integration processes are presented.
Effect of Deformation of Core Elements of Fast Reactor Core to the Seismic Response
Authors: Iwasaki Akihisa , Matsubara Shinichiro , Kawamura Kazuteru , Harada Hidenori , Yamamoto Tomohiko
Published: November 2019

Core elements of a fast reactor are self-standing on the core support structure and not restrained in the axial direction. When the earthquake occurs, it is necessary to consider vertical behavior and horizontal displacement of the core elements simultaneously. In the core seismic analysis, a three dimensional core vibration behavior was evaluated by considering fluid structure interaction, collision with adjacent core elements and vertical displacement and verified by a series of vibration tests. But the evaluation had a assumption of straightness of each core elements which may be bowed due to thermal expansion and swelling under restraint of the horizontal direction between the upper pad and lower structure (Entrance Nozzle). If the core elements are deformed in its plant operation, they may push each other against its adjacent core elements. The large horizontal interference forces may work to decrease the vertical displacement of the core elements.

In this study, to grasp and estimate the behavior under the deformed core elements under the earthquake motion, a three dimensional seismic analysis model consist of all of core elements with consideration of the effect of deformed core elements were prepared, analyzed and verified by hexagonal-matrix tests with 37 core elements and single row mock-up models with 7 core elements. These test results show that the rising displacements decrease with increased deformation and no rising occurs when the deformations exceed a threshold.

In this paper, the effect of bending deformation due to thermal expansion and swelling on the rising displacement of the core elements was shown by seismic experiments.
Development of Active Vibration Damping Device Adjusting TMD to Various Periodic Bands of Seismic Waves
Authors: Watanabe Kota , Miura Nanako , Sone Akira
Published: November 2019

There are many high-rise buildings all over the world, especially urban areas. Their usage is diverse, such as offices and residences. Therefore, earthquake countermeasures for high-rise buildings are indispensable. It is known that a tuned mass damper (TMD), which is mainly installed for countermeasures against wind shaking, does not show sufficient damping effect when large earthquake occurs or when higher modes vibration is excited. In addition, when exceeding the drive limit of the TMD in resonance, the TMD may collide against the stopper and deteriorate the response of the building. There are some researches targeting building with TMD, and many of them aim at developing new devices. However, installing a new equipment instead of TMD requires a lot of cost and construction period. Therefore, in this research, an active device that can be attached to TMD is developed. Moreover, validity is examined by numerical simulation. In this paper, parameters of the passive elements are verified as a basic research of the proposed device.
Dynamic Response Analysis of Beam Mode Vibration of Piping System due to Turbulent Flow Around Bend
Authors: Kataoka Shunji , Matsuura Kota , Qian Shaoxiang
Published: November 2019

Prevention of piping vibrations during design stage has attracted attention recent years. Though the piping vibration occurs due to various mechanisms, the vibration due to fluid turbulence is one of a major topic discussed. The pressure fluctuation due to fluid turbulence occurs around flow discontinuities such as branches, elbows, flow expansions and valves, and the fluctuation can cause the piping vibration and both shell mode and beam mode vibration can occur. Guideline published by Energy Institute UK[1] (EI-AVIFF) shows a method to check the possibility of piping vibration due to flow induced turbulence and it gives some information on recommended piping span. The method is quite useful for screening purpose to select the piping system with potential vibration risks. However, it is known that the guideline is based on very conservative assumptions, as 90-degree miter bend, and it results in overdesign of piping systems, so more detailed vibration assessment approach succeeding the screening is demanded.

In this paper, the method of detailed beam-mode piping vibration assessment using finite element dynamic structural analysis and Large Eddy Simulation (LES) based CFD are discussed. As an example, LES based CFD analyses were conducted on 90 degrees single miter bend, long and short elbow. The resultant pressure fluctuations are compared to past published report and good agreement was confirmed. The CFD results were reorganized and piping dynamic analysis were conducted. Based on these analysis results, the detailed piping vibration risk assessment method using CFD and dynamic structural analysis are proposed.
Advances Towards Elastic-Perfectly Plastic Simulation of the Core of Printed Circuit Heat Exchangers
Authors: Katz Alon , Ranjan Devesh
Published: November 2019

Printed circuit heat exchangers (PCHEs) are used in a number of novel nuclear reactor designs. In order to use a PCHE as a primary coolant confinement unit in the United States, the stress and strain must be modeled under realistic service loads, and shown to remain within limits imposed by ASME standards. Due to the complex geometry and multi-length scale features, direct simulation of the stress and strain in a utility scale PCHE is not practical because of the large number of degrees of freedom. This work presents an algorithm to model damage to the core region of a PCHE using planar 2D formulation and realistic service loads. We compare how closely the results from three different planar formulations match the results of a corresponding 3D model. We also explore other ways of reducing the size of the numerical model required to accurately simulate the stress and strain in the core region of a PCHE. Finally, we perform strain-limits evaluation on a core region of a PCHE using fully temperature coupled, elastic perfectly plastic material properties, and realistic service loads, obtained from plant dynamics code of sodium cooled fast reactor coupled with a supercritical CO2 Brayton cycle. For our analyses, we used CSIMSOFT Trelis: a commercial meshing software, Multi Object Oriented Solver Environment (MOOSE): an open source finite elements solver, and Paraview: an open source post processing tool. Our methodology is presented and discussed in sufficient detail so that the work can be reproduced by others.
Characterization of Piezoelectric Material Properties Using Atomistic Simulations
Authors: Park Y. H. , Hijazi I.
Published: November 2019

Damage monitoring in pipes and pressure vessels are important to ensure safety and reliability of these structures. Structural damage monitoring based on an actuator-sensor system is a promising technology to obtain real-time information for structural condition. Since piezoelectric materials in electromechanical systems can detect mechanical responses such stress and deformation as a sensor or perform a defined work as an actuator, piezoelectric actuators/sensors are extensively used in damage detection. In the design of piezoelectric actuators and sensors, it is important to know the properties of the piezoelectric material, in particular, piezoelectric constants to predict its actuation/sensing performance. In this study we determine a piezoelectric constant of ZnO using molecular dynamics simulations. We introduced a shell degree of freedom to the core-only atomic potential to enable polarization of the ion caused by an electric field. This modeling technique allowed for accurate piezoelectric response of the molecular structure.
A Proposal of Inelastic Constitutive Equations of Lead Alloys Used for Structural Tests Simulating Severe Accident Conditions
Authors: Hashidate Ryuta , Onizawa Takashi , Wakai Takashi , Kasahara Naoto
Published: November 2019

This paper studies inelastic stress-strain relationship equation and creep rupture equation and creep strain equation of 99%lead-1% antimony alloy. Under the severe accident conditions, structural materials of nuclear power plants are subjected to excessive high temperature. Although it is very essential to clarify how the structure collapses under the severe accident conditions, there’re no experimental evidences of failure modes and the failure mechanisms in such high temperatures are not clarified. However, it is very difficult and expensive to perform structural tests using actual structural materials, such as austenitic stainless steels. Therefore, the authors propose to use lead alloys instead of actual structural materials. Because the strength of such alloys is much poorer than that of the actual structural materials, failure can be observed at much low temperature and by much small load.

For demonstration of analogy between the failure mechanisms of lead alloy structure at low temperature and those of the actual structures at extremely elevated temperature, numerical analyses are required. The authors proposes inelastic constitutive equations of lead alloy based on a series of material tests. Nonlinear numerical analyses, e.g. finite element analyses, can be performed using the proposed equations.
Buckling and Fatigue Evaluation of Braced Piping Support by Numerical Analysis
Authors: Shimazu Ryuya , Sakai Michiya
Published: November 2019

Buckling and fatigue evaluation of braced piping supports was conducted using numerical analysis. Buckling and fatigue occurred on the piping support during vibration and static load tests. A numerical model for the evaluation was developed, and the load–displacement relationship and local strain obtained by the numerical analysis were in good agreement with experimental results. Thus, the numerical model was validated. Buckling and fatigue evaluations were subsequently conducted using the model. In the buckling evaluation, the experimental buckling load was in good agreement with that obtained by Johnson’s formula. Fatigue evaluation was conducted to investigate whether fatigue crack had occurred before the rupture on the piping support. The linear cumulative damage was calculated, suggesting the possibility of fatigue crack formation. Ductile rupture was considered to occur after the fatigue crack formation.
An Update on Quantifying Bolt Relaxation During High Temperature Operation
Authors: Brown Warren , Knight Nathan
Published: November 2019

A summary of testing related to bolt relaxation, which occurs at temperatures above 230°C (450°F) was presented in a previous paper. The work has since been extended to include lower temperature data for common bolting materials. This paper provides a summary of the additional work performed and further observations regarding the acceptable design limits for A193-B7 and A193-B7M bolt materials. In addition, a conclusion regarding the recommendations made in API RP751 comparing A193-B7 and A193-B7M relaxation is made.
HPHT Equipment Stress Intensity Calculation Based Upon the API 579/ASME FFS and ABAQUS J Integral Fracture Mechanics Basis
Authors: Lim Jong IL , Han Young-Hoon
Published: November 2019

Fatigue sensitive pressure containing components in the oil & gas industry requires a life cycle assessment. High Pressure High Temperature (HPHT) equipment designed using API 17TR8 and ASME Section VIII Division 3 are evaluated for cyclic fatigue crack growth per API 579/ASME FFS-1 fitness for service level 3 assessment. The level 3 assessment requires more advanced stress analysis to define the state of stress at critical locations and a defined initial flaw for cycle growth assessment. The cyclic crack growth in pressure containing equipment depends on the alternating crack tip stress intensity values for the defined load histogram. Therefore, in this paper, the stress intensity at crack tip is calculated using two approaches for 20ksi pressure equipment. The first approach is to utilize linear elastic stresses obtained from a three-dimensional finite element evaluation, where the stress profiles are used as an input to Signal FFS (fitness for service) Quest software, to calculate stress intensity at crack tip. The second approach utilizes a J-integral based on fracture mechanics analysis considering a pressure penetration on cracked surfaces. Although there is a difficulty in representing the complete production load histogram applying the J-integral solution, this paper provides evaluation of the two methods for comparison of results. It also demonstrates the feasibility of application to pressure vessel equipment.
Tensile Behavior of 82/182 Filler, Butter and Heat-Affected-Zones in a 508 LAS - 316 SS Dissimilar Weld: Tensile Test, Material Model and Finite Element Model Validation
Authors: Mohanty Subhasish , Listwan Joseph , Majumdar Saurindranath , Natesan Krishnamurti
Published: November 2019

In this paper we present the room temperature tensile test results for 82/182 Filler, Butter Weld and Heat-Affected-Zone in a 508 LAS − 316 SS Dissimilar Weld (DW). Also we present the associated tensile properties and material hardening model parameters; those can be used for future component level stress analysis modes. In addition, we present the finite element (FE) model of the uniaxial DW tensile-test specimens to validate the accuracy of the estimated material model parameters. Through the FE model results, we also explain the importance of various offset strain yield stress in capturing the material behavior in a mechanistic (using FE) modeling approach particularly while modeling the plasticity driven low-strain-amplitude low-cycle-fatigue damage of a structural component.
Hydrogen Induced Cracking of a Dissimilar Weld in a Hydrogen Manufacturing Plant
Authors: Park Neil , Penso Jorge
Published: November 2019

A hydrogen manufacturing plant experienced circumferential cracking at the dissimilar weld on the outlet header. The outlet header was a cold wall design and the dissimilar weld was between HP40 modified and carbon ½ Mo steels. The resultant failure investigation found the cause to be hydrogen induced cracking of the dissimilar weld at the fusion boundary zone. The hydrogen was generated from the CO2 corrosion which occurred due to operating the tubes below the dew point and the hydrogen was trapped in the steel by the CO chemisorption onto the steel. The following paper outlines the failure investigation and the fitness for service conducted to maintain the running of the plant.
PTS Evaluation Case Study Considering Actual Through-Wall Fracture Toughness Distribution
Authors: Yamamoto Masato , Nagai Masaki
Published: November 2019

The surveillance test specified in JEAC4201 requires the fracture toughness evaluation of base metal at 1/4-T thickness and T-L orientation, where the initial fracture toughness generally is the minimum in whole thickness at any orientation. In the present study, actual through-wall fracture toughness distribution from a commercial RPV base metal on both of T-L and L-S (actual through crack orientation) orientations were evaluated from Zion Unit 1, which was decommissioned after 25 years (15EFPY) commercial operation. A base metal block of 40mm(T) × 216mm(L) × 216mm(S) was retrieved from belt line region by effort of ORNL and provided to CRIEPI under the USA - Japan collaborative agreement on civil nuclear research framework called CNWG. Through-wall fracture toughness distribution was characterized by means of the Master Curve method utilized by 4mm thickness C(T) “Mini-C(T)” specimens. Near surface material possessed significantly high fracture toughness at amount of 40 degrees Celsius lower reference temperature (To) than those in center thickness locations, despite of higher neutron fluence gained during service operation. Pressurized thermal shock evaluation by probabilistic fracture mechanics code PASCAL4 demonstrated that through-wall fracture probability can be remarkably lowered by considering through-wall fracture toughness distribution.
Effect of Coolant Water Temperature of ECCS on Failure Probability of RPV
Authors: Katsuyama Jinya , Masaki Koichi , Lu Kai , Watanabe Tadashi , Li Yinsheng
Published: November 2019

For reactor pressure vessels (RPVs) of pressurized water reactors, temperature of the coolant water in the emergency core cooling system (ECCS) may influence the structural integrity of the RPV during pressurized thermal shock (PTS) events. By focusing on a mitigation measure to raise the coolant water temperature of ECCS for aged RPVs to reduce the effect of thermal shock due to PTS events, we performed thermal hydraulic analyses and probabilistic fracture mechanics analyses by using RELAP5 and PASCAL4, respectively. The analysis results show that the failure probability of RPV decreased dramatically when the coolant temperature in accumulator as well as in the high- and low-pressure injection systems (HPI/LPI) was increased, although the increase in coolant temperature in the HPI/LPI only did not lead to a decrease in the failure probability.
Vibration Control of Buildings Using Series Rolling-Pendulum Tuned Mass Dampers
Authors: Wang Jer-Fu , Chen Chun-Hung , Chang Chang-Ching , Lin Chi-Chang
Published: November 2019

This paper proposes a passive vibration control device, series rolling-pendulum tuned mass damper (SRPTMD), with a “ball-in-ball” configuration. A conventional pendulum TMD (PTMD) generally requires a long cable length that usually exceeds one-story height for high-rise buildings. A rolling-pendulum TMD (RPTMD) is a mass that can roll on a base with a curvature instead of swaying with a cable, significantly reducing the requirement of vertical rooms. In addition, a ball-in-ball SRPTMD is equivalent to a system with two degrees of freedom in series. This study aimed to derive equations of motion of the primary building-SRPTMD system, conduct a parametric study for SRPTMD, and investigate the structural control performance of an SRPTMD. Results showed that an SRPTMD performed similarly to an RPTMD. One advantage of an SRPTMD is that the fundamental natural frequency of an SRPTMD can be altered to a certain extent by changing the radius ratio of the inner ball to the outer ball, whereas the natural frequency of an RPTMD can only be altered by changing the curvature of its base, which is far more difficult. Another advantage is that the two modal frequencies of an SRPTMD can be manipulated by selecting a specific set of radius ratios between the base, the outer ball, and the inner ball, which means that an SRPTMD has higher potential on multiple modes control.
Technical Basis for Expansion of ASME BPVC Section XI, KIC Curve Applicability
Authors: Xu Hongqing , Palm Nathan , Udyawar Anees
Published: November 2019

When the Appendix G methodology, fracture toughness criteria for protection against failure, was first adopted by ASME Section III in 1972, it included a lower-bound Kir curve for ferritic steels with specified minimum room-temperature yield strength up to 50 ksi. In 1977, Section III Appendix G added a requirement to obtain fracture-toughness data for at least three heats (base metal, weld metal, and heat-affected zone) if the KIR curve is used for ferritic steels with specified minimum room-temperature yield strength between 50 and 90 ksi. The three-heat data requirement has not changed when the lower bound curve was adopted by Section XI, or when the lower-bound crack initiation toughness curve was changed from the dynamic Kir curve to the static KIc curve during the 2000s. Based on the accumulation of fracture-mechanics data of ferritic steels with specified minimum yield strength between 50 ksi and 90 ksi and their use for Class 1 pressure vessel production, Section XI recently expanded the applicability of the KIc curve to SA-508 Grade 2 Class 2, SA-508 Grade 3 Class 2, SA-533 Type A Class 2, and SA-533 Type B Class 2 whose specified minimum room-temperature yield strength is 65 ksi or 70 ksi. This paper describes the technical basis including the fracture-mechanics data to support the expansion of the applicability of the KIc curve by ASME Section XI.
High Temperature Hydrogen Attack: New NDE Advanced Capabilities — Development and Feedback
Authors: Le Nevé Charles , Loyan Sophie , Le Jeune Léonard , Mahaut Steve , Demonte Serge , Chauveau Daniel , Renaud Romain , Tessier Manuel , Nourrit Nicolas , Le Guellaut Anthony
Published: November 2019

In petroleum industry, hydrogen is used in many assets. With temperature and pressure, hydrogen can damage materials. This damage is called High Temperature Hydrogen Attack (HTHA) and is a time dependent degradation mechanism that can affect the integrity of steels used for pressure containment operating above about 400°F (204°C). HTHA has caused major accidents in Petroleum Industry.

API RP 941 [1] currently provides guidance for steel selection (and so susceptibility to attack) in relation to temperature and ppH2 via Nelson curves. In the last edition, 4 stages of degradation for both base metal and weld metal are described.

In the past, only stage III was detectable by the combination of different Ultrasonic methods which were known as AUBT – Advanced Ultrasonic Backscatter Technique. But, capability of detection was limited to defects above 500–1000μm, correspondent to small fissures. So, it was impossible to detect early stage of degradation as steel grain size (around 50μm).

For several years, performances of non-destructive techniques have rapidly increased and new advanced ultrasonic technologies are available such as:

- Phased Array Ultrasonic Techniques (PAUT)

- Time Of Flight Diffraction (TOFD)

- Total Focusing Method (TFM)

This paper describes latest techniques and results obtained by Total and French Welding Institute in laboratory, and discuss the efficiency of the methods, over real HTHA degradation blocks. An overview of TFM is also proposed by CEA who work on innovating development to increase the performance of this technique.
Fracture Mechanics Analysis of a PWR Under PTS Using XFEM and Input From TRACE
Authors: Mora Diego F. , Mukin Roman , Costa Garrido Oriol , Niffenegger Markus
Published: November 2019

In this paper, an integrity assessment of a reference Reactor Pressure Vessel (RPV) under Pressurized Thermal Shock (PTS) is performed. The assessment is based on a multi-step simulation scheme, which includes the thermo-hydraulic, thermo-mechanical and fracture mechanics analyses. The proposed strategy uses a three dimensional (3D) finite element model (FEM) of the RPV with the Abaqus code to solve the thermo-mechanical problem for the scenario of a Large-Break Loss-of-Coolant Accident (LBLOCA). In order to obtain the boundary conditions for the thermal analysis, the thermo-hydraulic results from a 3D RPV model developed in the system code TRACE are used. The fracture mechanics analysis is carried out on submodels defined on the areas of interest. Submodels containing cracks or flaws are also located in regions of the RPV where there might be a concentration of stresses during the PTS. The calculation of stress intensity factor (SIF) makes use of the eXtended FEM (XFEM) approach. The computed SIF of the postulated cracks at the inner surface of the RPV wall are compared with the ASME fracture toughness curve of the embrittled RPV material.

For different transient scenarios, the boundary conditions were previously calculated with a computational fluid dynamics (CFD) model. However, cross-verification of the results has shown consistency of both CFD and TRACE models. Moreover, the use of the later is very convenient for the integrity analyses as it is clearly less computationally expensive than CFD. Therefore, it can be used to calculate different PTS scenarios including different break sizes and break locations. The main findings from fracture mechanics analyses of the RPV subjected to LBLOCA are summarized and compared. The presented results also allow us to study the influence of the dynamic cooling plume on the stress intensity factor in more detail than with the conventional one-dimensional method. However, the plumes calculated with both approaches are different. How much this difference affects the integrity assessment of the RPV is discussed in the paper.
Application of Gaussian Process Regression for the Accuracy Assessment of a Three-Dimensional Strain-Based Model
Authors: Li Yueying , Li Yong , Hassanien Sherif , Okoloekwe Chike , Adeeb Samer
Published: November 2019

Dents are one of the common integrity threats of long-distance transmission pipelines. The current CSA Z662 standard assesses dents based on the dent depth. However, the severity of dent features is a function of many factors. Most recently, numerical modeling via finite element analysis (FEA) has been utilized to assess dent severity, however the approach is computationally expensive. Recently, the authors’ research group developed a robust but much simplified analytical model to evaluate the strains in dented pipes based on the geometry of the deformed pipe. When the strain distribution predicted using the analytical model is benchmarked against the strains by nonlinear FEA they showed a good agreement with certain error. The procedure, however, predicts more conservative results in terms of the maximum equivalent plastic strain (PEEQ). In order to estimate the accuracy in the recently developed model, a series of nonlinear FEA pipe indentation simulations were conducted using the finite element analysis tool, ABAQUS and compared with the analytical prediction.

This paper presents an application of a Bayesian machine learning method named Gaussian Process Regression (GPR) for the accuracy assessment of the developed analytical model for dent strain assessment, quantifying the error in comparison with the FEA in terms of the maximum PEEQ. The Gaussian Process (GP) model holds many advantages such as easy coding, prediction with probability interpretation, and self-adaptive acquisition of hyper-parameters.

By varying the dent depth and the indenter radius, this paper provides a model that quantifies the error in the developed analytical model. The proposed model can be utilized to rapidly determine the severity of a dent along with the accuracy of the prediction. This analysis method can also serve as a reference for other analytical expressions.
Crack Growth Rate Model for CISCC of Stainless Steel Canisters
Authors: Broussard John E. , Bryan Charles , Sindelar Robert , Lam Poh-Sang
Published: November 2019

This paper provides a technical basis for a crack growth rate (CGR) for use in performing evaluations of cracking in stainless steel canister materials. The source of crack initiation and growth is deposition of chloride aerosols on the canister surface followed by deliquescence leading to a brine solution. The brine solution attacks the stainless steel surface, leading to pitting; in the presence of tensile stress (such as residual tensile stress due to welding), stress corrosion cracking can occur. The CGR will be used for evaluating flaw growth under a proposed ASME Boiler and Pressure Vessel Code Case covering stainless steel canisters.
Effect of Phase Velocities Prediction on Fluidelastic Instability of a Cantilever Pipe Subjected to Gas-Liquid Flow
Authors: Ortiz-Vidal L. Enrique
Published: November 2019

The effect of the phase velocity models on the prediction of fluidelastic instability of a cantilever pipe subjected to gas-liquid internal flow is studied. According to the accepted fluidelastic formulation, a two-phase flow correlation is needed to relate phase velocities in order to solve the system equation. In this study, seven reported correlations, including the homogeneous no-slip model, are used to study the effect of phase velocities prediction on fluidelastic instability parameters, specifically, critical mixture-velocity and critical frequency. Comparisons between simulations and previously reported experiments are performed. Results show that the correlation selection plays an important role in critical mixture-velocity predictions. On the other hand, the critical frequency is less sensitive to the correlation.
Uncertainties in Pressurized Thermal Shock Analyses
Authors: Niffenegger M. , Costa Garrido O. , Mora D. F. , Qian G. , Mukin R. , Sharabi M. , Lafferty N. , Niceno B.
Published: November 2019

Integrity assessment of reactor pressure vessels (RPVs) can be performed either by deterministic fracture mechanics (DFM) or/and by probabilistic fracture mechanics (PFM) analyses. In European countries and Switzerland, only DFM analyses are required. However, in order to establish the probabilistic approach in Switzerland, the advantages and shortcomings of the PFM are investigated in the frame of a national research project. Both, the results from DFM and PFM depend strongly on the previous calculated thermal-hydraulic boundary conditions. Therefore, complete integrity analyses involving several integrated numerical codes and methods were performed for a reference pressurized water reactor (PWR) RPV subjected to pressurized thermal shock (PTS) loads. System analyses were performed with the numerical codes RELAP5 and TRACE, whereas for structural and fracture mechanics calculations, the FAVOR and ABAQUS codes were applied. Additional computational fluid dynamics analyses were carried out with ANSYS/FLUENT, and the plume cooling effect was alternatively considered with GRS-MIX. The results from the different analyses tools are compared, to judge the expected overall uncertainty and reliability of PTS safety assessments. It is shown that the scatter band of the stress intensities for a fixed crack configuration is rather significant, meaning that corresponding safety margins should be foreseen. The conditional probabilities of crack initiation and RPV failure might also differ, depending on the considered random parameters and applied rules.
Technical Basis Document for Alloy 82/182 Weld Inspection Code Case N-770 Through N-770-6
Authors: Donavin Paul , Bamford Warren , Marlette Stephen
Published: November 2019

The Primary Water Stress Corrosion Cracking causes existing ASME BPV Code Section XI inspection and repair methodology to need enhancement. This forms the basis for Code Case N-770 and revisions through 6. The paper includes the bases for examination requirements, examination schedule, and repair criteria.
Sequential Bayesian History Matching for Model Calibration
Authors: Gardner Paul , Lord Charles , Barthorpe Robert J.
Published: November 2019

Computer models, whilst frequently utilised for many complex engineering tasks, suffer from model form errors due to some level of simplification and/or absence of certain physics. These model form errors lead to a mismatch between model outputs and observational data when the ‘true’ parameters are known; a phenomenon known as model discrepancy. Calibration of a computer model without consideration of this type of uncertainty therefore leads to biased estimates of system parameters. Bayesian history matching (BHM) is one such method of calibrating a computer model whilst accounting for uncertainties associated with model discrepancy. The ‘likelihood-free’ technique assesses the system parameter domain using an emulator of the complex computer model in order to discard parameter combinations based on how unlikely they were to have produced a known observation response. BHM can be approached in an iterative manner, allowing sequential-based approaches to be used in selecting new computer model evaluations that will maximise the improvement in emulator performance. This paper develops techniques for sequentially selecting new computer model evaluations, reducing the total number of evaluations and increasing improvements in the emulator. The developed metrics and criteria are outlined with a demonstration on a numerical case study in order to visually demonstrate their applicability and increase in computational efficiency.
Tone mergers in Hong Kong Cantonese: An asymmetry of production and perception
Authors: Fung Roxana S. Y. , Lee Chris K. C.
Published: November 2019

This paper examines the tone-merging phenomenon in Hong Kong Cantonese. Both perception and production tasks were administered to 120 participants with ages ranging from 20 to 58 years. After considering the complicated interplay of perception and production confusion, the paper provides statistical evidence that three tonal contrasts have undergone merging in contemporary Hong Kong Cantonese. They are Full-merger T2 and T5, where contrast is collapsed in both perception and production; Partial-merger T3 and T6, where contrast is collapsed in production only; and Near-merger T4 and T6, where contrast is collapsed in perception but maintained in production.