bluuebunny/crossref_metadata_2025 huggingface dataset:
Analysis of the Coupled Dynamics of an Offshore Floating Multi-Purpose Platform: Part A — Rigid Body Analysis
Authors: Li L. , Collu M. , Ruzzo C. , Failla G. , Abhinav K. A. , Arena F.
Published: November 2019

A multi-purpose platform (MPP) is an offshore system designed to serve the purposes of more than one offshore industry. Indeed, over the past decades, a number of industries have expanded, or are expanding, from onshore to offshore locations (renewables, aquaculture, tourism, mineral extractions, etc.), and the research on these type of platform is increasing. In the present work, a MPP able to accommodate wind turbines, wave energy converters, and aquaculture systems are considered. This work presents the first part (Part A) of the analyses of the dynamics of the floating support structure for this MPP, focusing on the rigid body dynamic response, while its complementary hydroelastic analysis is presented in Part B (OMAE2019-96282).

The aim here is to assess the dynamic response of the platform with respect to the preliminary requirements imposed by the wind turbine, the aquaculture system, and the other ancillary systems. After describing the platform analyzed, and explaining the aero-hydro coupled model of dynamics approach adopted, two independent analyses are conducted, one using the SESAM package by DNV-GL, and another using ANSYS AQWA, in order to verify the results, in absence of experimental data. Considering a severe, but still operational, load case, the preliminary results seem to demonstrate that the chosen platform can satisfy the dynamics constraints imposed by the payload systems.
First in Place Replacement of a TLP Top Tendon Connector Flex Bearing
Authors: Otten Jeffrey D. , Kuriakose Vinu , Amini Shakib
Published: November 2019

Tension Leg Platform (TLP) tendons typically are installed for the life of the platform and incorporate elastomeric flex bearings. The Allegheny TLP, owned and operated by ENI Petroleum, was installed in Gulf of Mexico Green Canyon Block 254A, in 1999. It was designed for a service life of 20 years and currently ENI wants to extend the operating life of the platform. A baseline inspection showed significant degradation of the top tendon connector (TTC) flex bearing and it was concluded that the flex bearings needed to be replaced if the platform was to continue to operate safely.

SBM and BHGE came up with a solution for replacing the TTC including the flex bearing, which was accepted by ENI. This involved ballasting the TLP to reduce the tendon pretensions, installing a temporary buoyancy module, and using a hydraulic tool, first of its kind in the world, to take the load off of the old TTC and gradually release the tendon to free stand. The tool was then retrieved with the old TTC, onboard the installation vessel. A second identical tool with the new TTC was then lowered on to the porch and the tendon stretched to the lock-off position by the tool and locked in position with the new TTC. This was done on all six (6) tendons and the platform was de-ballasted to the original tendon pre-tensions. Development of the tendon de-tensioning tool required new designs, extensive shop testing, and planning.

The final offshore campaign took place during July 2018 and was completed in three (3) weeks. This represented a successful conclusion to a three (3) year effort. This paper highlights lessons learned in completing a complex first time ever project and makes recommendations for the design of future TLP’s.
Aeromechanical Analysis of Wind Turbines Using Non-Linear Harmonic Method
Authors: Win Naung Shine , Rahmati Mohammad , Farokhi Hamed
Published: November 2019

In this paper, aeromechanical analysis of wind turbines is presented. The distinctive feature of this paper is the use of frequency based non-linear harmonic method which is an efficient computational method to study unsteady periodic flow and aeroleasticity of turbomachinery applications, and extensive validation of the non-linear harmonic method against conventional time domain solution methods. This paper is an extension of the authors’ previous work which analysed the aerodynamics of the MEXICO (Model Rotor Experiments In Controlled Conditions) Experiment wind turbine. Aeromechanical analysis of the MEXICO-Experiment wind turbine as well as 1.5 MW wind turbine are conducted in this study. Both conventional time domain solution method and non-linear harmonic method are used, and compared to each other for validation and verification of the non-liner harmonic method. Using the same numerical set-up for each method demonstrates the differences and capabilities of each solution method, and their computational expenses. Finally, this paper concludes with how the aeromechanical analysis of large wind turbines can be performed effectively and efficiently using the non-linear harmonic method.
Advances in Riser Management Technology Enabling Improved Efficiency for Deepwater and Harsh Environment Drilling
Authors: Lang Donogh W. , Bohan Paul , Gomes Victor , Venero Germain , Corrignan Hugues
Published: November 2019

Despite the abrupt fall in crude oil prices since 2014, operators continue to explore for, and develop, oil and gas resources in some of the most challenging offshore environments. Exploration and development drilling is currently ongoing or planned in locations such as West of Shetland, offshore Eastern Canada, along Ireland’s Atlantic margin, in the South Atlantic Ocean and offshore South Africa. All these locations are characterized by the challenges of deepwater, powerful ocean currents and high seas.

With the lower oil price environment, carrying out drilling operations at these locations both safely and economically requires the adoption of new digital technologies and associated processes that maximize efficiency and reduce the cost of well programs. A significant aspect of this relates to planning and execution of operations involving the marine drilling riser, which can be a major contributor to non-productive time in deepwater and harsh environment locations. This paper describes a holistic approach to addressing this challenge, which covers every phase of riser operations for the drilling program, from pre-operations global riser analysis through to post-operations assessment.

The paper focuses on the technology that enables this holistic solution, with emphasis on the state-of-the-art riser management technology that is deployed on the drilling vessel. This uses an advanced finite element model of the riser, BOP stack, wellhead, conductor, casing and soil interaction as well as a detailed model of the riser tensioning system. The same model is used in both the pre-operations global drilling riser analysis phase and the operational drilling phase to ensure consistency.

Incorporation of the model provides the capability to perform forecast analysis on-board the rig, allowing offshore personnel to simulate a range of operations hours and days in advance using forecast metocean conditions, thereby assessing the feasibility of critical well construction operations before they commence. Capabilities for real-time monitoring of ongoing operations, fusing sensor data with the riser model, are also described. These provide calculation of live watch circles and operating envelopes for connected-mode operations, in addition to tracking of riser joint, wellhead, conductor and casing fatigue from both wave and VIV excitation. Additionally, calibration of soil models — often a critical input to wellhead fatigue analyses — can be performed.

Application of the technology is illustrated by means of a case study describing deployment on a record-breaking well in a harsh environment location. This demonstrated significant cost savings while simultaneously increasing safety and improving integrity assurance.
A Method to Calculate the Multi-Axial Fatigue of Subsea Rigid Jumper due to VIV
Authors: Kapoor Kunal , Liu Zhenhui , Ong Muk Chen
Published: November 2019

Prediction of vortex induced vibration (VIV) and estimation of fatigue damage for subsea multi planar structures exposed to significant current condition is an important topic for subsea engineering. Due to the multi-planar characteristics of structure, the VIV induced stress states of subsea jumper are normally with the combination of flexural and bending stresses. Consequently, the associated fatigue is a multi-axial fatigue problem. In this study a novel energy-critical plane method by Farahani [1][2] has been used for fatigue assessment instead of the traditional method with utilizing the stress range and SN curve, for example the 1st principle stress method as recommended by DNVGL-RP-F105 (2017) [3]. By using this method, the phase change of the stress from different modes is considered. A case study based on previous jumper experiments by ExxonMobil is included. Fatigue results have been compared with DNVGL-RP-F105 (2017) [3] approach. Advantages of energy-critical plane approach have been discussed. Phase change between flexural and torsional stresses has been successfully captured and its effect on fatigue damage has been presented. Additionally, some discussions have been performed with respect to the application of DNVGL-RP-F105 (2017) [3] to calculate the VIV fatigue to subsea rigid jumpers.
Analytical Methodology to Evaluate Flexible Risers Fatigue Lives at the Top Region
Authors: de Sousa Fernando Jorge Mendes , Queija de Siqueira Marcos , de Sousa José Renato Mendes , Campello George Carneiro
Published: November 2019

Traditionally, fatigue life calculations are very expensive in terms of time and computer resources. They are usually performed during riser design phases, when several lines with similar characteristics need to be analyzed. While operating, when problems are detected, fatigue analyses are also necessary to help to decide if any action is needed. In both situations, end fittings and bendstiffeners are usually the critical regions. Considering the high number of flexible risers installed in Brazil and the structural complexity of this kind of structure, a robust and fast methodology to evaluate the fatigue life of flexible risers becomes attractive. In this way, this paper proposes a analytical/numerical methodology to evaluate the fatigue life at the top region of flexible pipes. Using the top imposed motions and taking into account the properties of all structures in the riser, it is possible to evaluate tension analytically. Combining tension and the rotations imposed at the top of the riser, curvatures are determined, and stresses can be calculated. Finally, SN curves and the Miner’s rule for damage accumulation allow the estimation of fatigue life. The obtained results indicate that the proposed methodology is conservative when compared to traditional ones. Also, it is very fast, allowing the fatigue life estimation in minutes.
Current Induced Drag Forces on Cultivated Sugar Kelp
Authors: Endresen Per Christian , Norvik Carina , Kristiansen David , Birkevold Jens , Volent Zsolt
Published: November 2019

To obtain more knowledge of current induced drag forces on sugar kelp, towing tests with ropes containing cultivated sugar kelp was conducted. As freshwater may damage the kelp and cause changes in its mechanical response, tests were performed in a test facility containing seawater. A special purpose test rig was constructed for towing of ropes at different constant velocities through the water, thus simulating water current. The ropes were mounted horizontally and perpendicular to the towing direction. Several ropes, all 3 meters long, with either a medium level or high level of growth, were tested individually. The ropes with sugar kelp were collected from a seaweed farm prior to the experiments and tested with the kelp still attached to the ropes on which they were grown. The total drag forces on the ropes were measured along with the towing velocity. Based on the results from the experiments relations between drag forces, measured size, weight of the kelp and current velocity were found. The results also show signs of reconfiguration of the plants, i.e. adaption to the current flow to reduce the experienced loads. As a result, a power function with an exponent smaller than 2 can be used for modelling of the drag forces. The drag force seems to go towards a value proportional to the velocity squared for higher velocities, indicating that the plants might no longer be able to reduce the forces through reconfiguration. Results from this study expand the knowledge of drag forces on ropes with cultivated sugar kelp and may be implemented into a suitable numerical code for estimation of hydrodynamic loads on seaweed farms.
Emerging Technology in Fitness-for-Service Assessment of Crack-Like Flaws
Authors: Anderson Ted L.
Published: November 2019

This paper describes several recent advances in crack assessment technology that have been or will be incorporated into the API 579 fitness-for-service standard. Four technology areas are addressed herein:

• Stress intensity factor solutions. The 2016 edition of API 579 contains an extensive library of stress intensity solutions inferred from 3D finite element analysis.

• A new equation for fitting elastic-plastic J solutions. A parametric equation that captures the elastic, fully-plastic and contained-yielding regimes of deformation provides an alternative definition of reference stress in the failure assessment diagram (FAD) method.

• An enhanced constraint adjustment. A future edition of API 579 will include an improved version of the Wallin methodology for shifting the Master Curve reference temperature to account for constraint effects.

• A procedure to account for non-ideal crack profiles. Most crack assessment methods assume an idealized flaw shape such as semi-elliptical, but many real-world flaws have complex shapes.
Flow Past a Forced Oscillating Cylinder: A Three-Dimensional Numerical Study
Authors: Ping Huan , Bao Yan , Zhou Dai , Han Zhaolong
Published: November 2019

In this paper, we conducted a three-dimensional investigation of flow past a cylinder undergoing forced oscillation. The flow configuration is similar to the work of Blackburn & Henderson (1999) [1], in which Reynolds number equals to 500 and a fixed motion amplitude of A/D = 0.25. The oscillation frequencies are varied in the range near to the natural shedding frequency of a stationary cylinder. The flow dynamics are governed by Navier-Stokes equations and the solutions are obtained by employing high-order spectral/hp element method. It is found that the flow dynamics are significantly distinguished from the study of two-dimensional flow by Blackburn & Henderson (1999) [1]. The values of hydrodynamic forces are smaller compared to that in the two-dimensional study. However, lock-in boundary we identified is broader. In addition, a different type of hysteresis loop of energy transfer coefficient is obtained.
On GIS Based Facility Scale and Selection of Suitable Site of Floating Medical Support System on Big Disaster
Authors: Eto Hiroaki , Togawa Sachio , Yamamoto Morikazu , Miyasawa Shintaro , Yamaguchi Junko , Ikoma Tomoki , Aida Yasuhiro , Masuda Koichi , Shimomoto Sena , Kitabatake Yuichi
Published: November 2019

In 2011, Japan experienced a major catastrophe: The Great East Japan Earthquake and subsequent tsunami. After the tsunami struck, overland transport routes were cut off, and consequently, emergency supplies and people requiring medical attention could not be transported very efficiently. Many hospitals and other emergency facilities were destroyed or were operating with reduced capabilities during this period, meaning victims could not receive treatment within a reasonable timeframe. Therefore, we need to consider emergency facilities, particularly for medical support, which are resilient and versatile for use in such situations. Floating bases for disaster relief and support ships are already available for deployment along coastal regions or on rivers near affected areas. A medical support floating base has also been proposed, which is called the Medi-float hereafter, in preparation for the anticipated Tokyo Inland Earthquake. And it is determined that the primary function of this Medi-float should be as a dialysis treatment center during normal operation and primarily for the treatment of crush syndrome patients during a disaster. But the original proposal was deemed inadequate in terms of facility scale and selection of the suitable site of Medi-float. Therefore, in this research aiming at realization of Medi-float, firstly the number of people who develop crush syndrome in the target area is estimated by GIS based on the damage prediction of the huge earthquake striking Tokyo and the risk of building collapse. Based on the distribution of dialysis treatment facilities and data such as road network data in Tokyo, Voronoi diagrams were created using GIS. And facility scale required for Medi-float and suitable installed site were examined by the distribution of crushed syndrome patients obtained by analysis and Voronoi diagram.
Numerical Simulations of Riser Gas Behavior in Non-Aqueous Muds Using a Modified Drift Flux Model
Authors: Nwaka Nnamdi , Chen Yuanhang
Published: November 2019

Real-time prediction of riser gas behavior is of great importance in well control. Single bubble models have, thus far, been used to describe gas-in-riser events and define riser equilibrium. These models have however not considered the transient nature of desorption of gas influx from non-aqueous fluids (NAFs) during migration or circulation in a riser. This paper uses a modified drift-flux model (DFM) to more properly describe gas-in-riser events by incorporating time-dependent mass transfer processes in NAFs.

In this paper, we modified the DFM to account for the gas-liquid mass transfer due to the time dependent desorption of the gas phase. The advection upstream splitting model (AUSMV) hybrid scheme was used to solve the model. The time dependent mass transfer is calculated using a kinetic model developed based on recent experimental data.

The capability of this model to improve riser gas management is demonstrated using a case study and the simulations are compared to when mass transfer between gas influx and NAF is not considered. Results also show that the severity of unloading and depth of the riser equilibrium can be underestimated if a time dependent desorption is not considered.

The concept of riser equilibrium has been, thus far, developed without due consideration of mass transport of gas phase in the mud. This paper factors in the time-dependent desorption of the gas phase in the mud for a more realistic prediction of riser gas unloading events.
Characteristics of Transforming Waves Breaking Over a Fringing Reef
Authors: Gong Fuxian , Dhanak Manhar R.
Published: November 2019

Direct numerical simulation (DNS), based on solution of the Navier Stokes equations, is used to study the characteristics of the transformation of monochromatic waves over a simplified fringing reef, including wave shoaling, and wave breaking that occurs under certain circumstances. The reef geometry involves a sloped plane beach extended with a simple submerged horizontal reef flat. The characteristics are studied for several case studies involving a selection of submergence depths on the reef flat and for a range of incident wave conditions, corresponding to nonbreaking, a spilling breaker and a plunging breaker, are considered. The results are compared with those of laboratory experiments (Kouvaras and Dhanak, 2018). Consistent with other studies, generation of harmonics of the fundamental wave frequency is found to accompany the wave transformation over the reef and the process of transfer of energy through wave breaking. The energy flux decreases dramatically in the onshore direction when the waves break. The more severe the wave breaking process, the greater the decrease in energy flux, particularly in the wave shoaling process. Most of the wave energy is carried by the first harmonic throughout its passage over the fringing reef. In nonbreaking waves, the energy gradually transfers from the first harmonic to the second harmonic due to bottom effects in terms of flat wave troughs and secondary waves. The further the distance away from the fore edge of the reef, the larger the percentage of the transmission, resulting in a single dominant harmonic frequency at the end of the wave surfing zone. For breaking waves, the energy carried by the first harmonic gradually decreases in the onshore direction. Energy transmission between harmonics is not as efficient as nonbreaking waves, while wave dissipation is significant in the wave breaking process.
Learning From Dynamic Positioning Events
Authors: Kvitrud Arne
Published: November 2019

Sixteen loss of position incidents on fourteen units are reported to us from the petroleum activity on the Norwegian continental shelf, from 2014 to 2018. The incidents had a mixture of severity, with pollution of 360m3 mud, damage to drilling and production equipment, falling objects and three autolifts of bridges as the most severe consequences. The incidents are described briefly and the most common causes of the events are found. The cases are discussed in view of several approaches. The barrier concept, and modifications of previous established barrier functions and barrier elements are discussed. I discuss the man-technology-organisation examinations in the investigations. Further the application of the single failure analysis philosophy is reviewed, and I discuss limitations to the method based on our cases. Our cases are compared with previous learning from incidents on shuttle tankers. A discussion is done on the slow reactions to changes in the weather conditions. In the last section I discuss needs for improvement.
Improvement of the Method for Calculating Downhole Weight on Bit and its Application in Autodriller Systems
Authors: Wu Zebing , Guo Longlong , Zhang Shuai , Wu Yuanping , Lv Lantao , Wang Wenjuan , Pan Yujie , Wang Yongyong , Mokhtari Adnane El
Published: November 2019

The accuracy of downhole weight on bit (DWOB) is one of the most important factors in the improvement of drilling efficiency, especially in horizontal well drilling. This paper introduced an analytical model and developed a corresponding program to calculate DWOB using drilling data on the surface. A well with field data measured was utilized to verify the model. The results indicate that the calculated friction factors are reasonable, and the DWOB calculated using the analytical model is consistent with those measured by the measurement tool. To satisfy the requirement of real-time drilling monitoring, a least square fitting (LSF) model for the relationship between the DWOB and surface weight on bit (SWOB) measured by deadline sensor on the surface was established to improve the calculation speed. Compared to the analytical method, the LSF model features much faster calculation speed, and the DWOB predicted by LSF model shows much better agreement with the measured DWOB. In addition, the influence of friction factors and standpipe pressure on the coefficients of LSF model was analyzed. The method and calculation technique proposed have applications potential, such as integration with present autodriller systems, post-drilling analysis, drilling operation monitoring, drilling optimization and automation.
Numerical Study on Scale Effect of KCS
Authors: Zhou Yujie , Liu Liwei , Cai Xiao , Feng Dakui , Guo Bin
Published: November 2019

The key objective of this paper is to perform a fully nonlinear unsteady RANS simulation to predict the self-propulsion performance of KCS at two different scales. This simulations are performed at design speeds in calm water, using inhouse computational fluid dynamics (CFD) to solve RANS equation coupled with two degrees of freedom (2DOF) solid body motion equations including heave and pitch. The SST k-ω turbulence equation is discretized by finite difference method. The velocity pressure coupling is solved by PISO algorithm. Computations have used structured grid with overset technology. The single-phase level-set method is used to capture the free surface. The simulations of self-propulsion are based on the body-force method. The PID control method is applied to match the speed of KCS by changing the propeller rotation speed automatically. In this paper, the self-propulsion factors of KCS at two scales are predicted and the results from inhouse CFD code are compared with the EFD date, and then the reasons for the scale effect have been discussed.
CFD-Based Numerical Wave Basin for FPSO in Irregular Waves
Authors: Baquet Aldric , Jang Hyunchul , Lim Ho-Joon , Kyoung Johyun , Tcherniguin Nicolas , Lefebvre Timothee , Kim Jang
Published: November 2019

Following the successful application of CFD-based Numerical Wave Basin (NWB) to GBS, TLP and Semisubmersible platforms [1–4], the same methodology has been applied to simulate FPSO hull motion responses to irregular waves. It has been found that the NWB modeling practices developed for the other floater types must be modified for application to an FPSO. This paper describes how the NWB modeling practices have been improved, and then compares results from NWB simulations with those from physical model testing.
OpenModelica Modelling of the Thruster in a Compact Subsea Work-Class Remotely Operated Vehicle
Authors: Xing Yihan , Fotland Kristian , Ong Muk Chen
Published: November 2019

Thrusters are vital for the functionalities of remotely operated vehicles (ROVs). The development of thruster design is a trade-off between cost, thrust force, physical weight and size. A six degree of freedom model is created in OpenModelica to investigate the vibrations and bearing responses in thruster systems. The model consists of a marine propeller, a shaft, and two bearings. The propeller used is based on the Wageningen B-screw propeller series. The hydrodynamic added mass and damping forces are calculated from empirical equations based on open water tests and are functions of the propeller geometry, rotational speed and fluid density. Meanwhile, the mean thrust and torque are obtained from open water test data of the relevant propeller and are used to calculate the dynamic forces and moments from the marine propeller. Displacements in the axial, horizontal, and vertical directions are calculated and used to investigate vibration amplitudes and bearing life.

Initial steady-state simulations show that the bearing life of the bearings in the thruster is found to be highly dependent on the axial load acting on the bearing, i.e., the thrust force. Moreover, if the propeller is not balanced then high centrifugal forces can occur and result in severe forces in the radial direction which can be of concern regarding the bearing life.
Performance of Semi-Metallic Gaskets With Nubbins
Authors: Taylor Robert , Fairbanks David
Published: November 2019

Nubbins are predominately machined into a heat exchanger flange to create a high stress point to produce a tighter seal.

Traditionally the gasket used when a nubbin is present is a Double Metal Jacket (DMJ), which consists of a metal jacket with a soft internal sealing material e.g. Graphite, PTFE. The metal jacket is commonly soft iron, carbon steel or a 300-series austenitic stainless steel.

This paper will compare the performance of a DMJ and Kammprofile gasket, performance being – leakage and temperature cycling and the affect the nubbin has on the gasket after testing.
RPV Irradiation Surveillance Programmes in China
Authors: Zhang Shuo , Zhang Haisheng , Sun Kai
Published: November 2019

Nowadays, nuclear energy is very important to China. Since Qinshan phase I nuclear power plant, by the end of December 2018, 44 nuclear power units are in operation in the mainland of China, with a total power rate of 44645MW, all these units are pressurized water reactors except for two CANDU6 heavy water reactors of Qinshan phase III. The power rate of those units under construction is 16,921MW, and most of them are also pressurized water reactors. Pressurized water reactor is a proven reactor type, but the safety problems should always be paid close attention to, one of the problems is the safety of the reactor pressure vessel (RPV). RPV is the key component in determining the lifetime of pressurized water reactor nuclear power plants, because it is subject to the significant aging phenomenon of irradiation embrittlement and can not be replaced. For materials used for the RPV, sufficient strength and toughness are required to endure the operating conditions and the aging degradation. In order to ensure the safety of RPV, the international experienced practice is to set up the irradiation surveillance programme, including the design of the irradiation surveillance capsule, the irradiation surveillance program, the irradiation surveillance test and evaluation. This paper introduces the RPV irradiation surveillance programmes on pressurized water reactors in China.
Applicability of Seismic Fatigue Evaluation by JSME Code Case, NC-CC-008
Authors: Otani Akihito , Nakamura Izumi , Watakabe Tomoyoshi , Morishita Masaki , Shibutani Tadahiro , Shiratori Masaki
Published: November 2019

A Code Case, JSME S NC1, NC-CC-008, in the framework of JSME Nuclear Codes and Standards has been published. New seismic evaluation methodology for piping by utilizing advanced elastic-plastic response analysis method and strain-based fatigue criteria has been incorporated into the code case. It can achieve more rational seismic design than the current rule.

This paper demonstrates validity and applicability of fatigue evaluation method proposed in the code case. Experimental results of a shaking table test for a piping model is used for comparing the evaluation by the current rule with one by the code case. As a result, it is confirmed that the code case can provide a rational and conservative result in the fatigue evaluation of piping. Moreover, cycle counting in the fatigue evaluation was examined for further progress of the code case.
Effects of Initial Pressure and Length of a Broken Pipe on the Transient Hydraulic Loads Acting on Nuclear Steam Generator Tubes and Supports During Blowdown Following a Sudden Feedwater Pipe Break
Authors: Jo Jong Chull , Jeong Jae-Jun , Yun Byong-Jo
Published: November 2019

This paper investigates the effects of steam generator initial pressure and length of a broken feedwater pipe on the transient hydraulic loads on the pressurized water reactor (PWR) steam generator (SG) tubes and supports during blowdown following a sudden feedwater line break (FWLB). To do this, the transient flow fields inside the SG and the connected broken feedwater pipe are calculated by realistically treating the discharge flow as the sub-cooled water flashing flow. Then, the calculated transient flow field data are used to predict the transient hydraulic loads on the PWR SG tubes and supports for some specified cases where the SG initial pressure or the broken feedwater pipe length are different from each other.
How to Select the Optimized Time Step and Mesh Size for FEM Thermal Transients Simulations of PWR Vessels and Nozzles by Means of Artificial Neural Networks
Authors: Santucho Nicolas , Chimenti Martin , Duo Jose
Published: November 2019

This paper describes the development of a data base and associated interpolation tool used to perform the validation of FEA thermo-mechanical models designed to verify the structural integrity of a self-pressurized modular Reactor Pressure Vessel (RPV) and its nozzles under service transient thermal loads. The main goal is to assess the element’s size and time steps that provide a confidence level on the obtained solutions.

The validation process implies the definition of the geometry under study, its material’s properties, thermal load conditions and type of mesh element. With all this information, the program gives the user a set of curves for maximum time steps vs. temperature change rates for each typical thickness section in the modeled geometry for a chosen element size. Any point located below those curves assures a solution underneath a user specified allowable error (e.g.: 5%).

All calculations are processed using dimensionless variables in order to create a universal data base enabling the analysis of many different situations of geometries, materials and loads. To improve performance, an Artificial Neural Network algorithm was developed. The resulting application significantly reduces the convergence study time and efforts.
New Code Case Development for the Mitigation of PWSCC and CISCC in ASME Section III Components by Advanced Surface Stress Improvement Technology
Authors: Cho Sungwoo , Mohr Nicholas , Pyun Young Sik , Amanov Auezhan , Broussard John
Published: November 2019

A challenge for owners operating nuclear power plants and spent fuel canisters is to provide sound technical basis for the safety and security of long-term operation and storage, respectively. Two code cases N-729-6 and N-770-5 provide performance requirements for mitigation of Primary Water Stress Corrosion Cracking (PWSCC) in ASME Section XI and Code Case N-860 “Examination Requirements and Acceptance Standards for Spent Nuclear Fuel Storage and Transportation Containment Systems” is under development in ASME Section XI. The primary degradation concern being addressed in N-860 is Chloride Induced Stress Corrosion Cracking (CISCC). ASME Section III has formed two Task Groups with the intent to reduce PWSCC and CISCC in operation by mitigating residual stresses during new construction of components.

ASME Section III formed Task Group Weld Residual Stress (TG-WRS) to incorporate lessons learned into the Code from operating plants regarding their experience with stress corrosion cracking. An example of expected guidance from TG-WRS is to consider residual stresses after weld repair of a susceptible material when the repair surface is exposed to the wetted environment. To address this concern, one form of mitigation could be the use of SSI which has been used in operating plants. However, there is a gap because no acceptance or performance criteria exists for mitigation of SCC by surface stress improvement for ASME Section III components.

The executive committee of ASME requested that a new Task Group named “Advanced Surface Stress Improvement Technology” (ASSIT) be formed by the Korean International Working Group (KIWG) and Materials Fabrication and Examination (MF&E) to address this gap by developing a code case for mitigation of PWSCC and CISCC for new ASME Section III components by SSI techniques. This paper will discuss the background and current approach being taken by Task Group ASSIT in developing SSI acceptance or performance criteria for mitigation of SCC. The necessary technical reports supporting this code case are also under development as part of joint projects between Doosan Heavy Industries and Construction (DOOSAN), Electric Power Research Institute (EPRI), and Sun Moon University (SMU). Interim reports summarizing the status of these joint projects will be presented as separate papers in the same session.
Mean Stress Correction for Fatigue Life of Carbon Steel: Proposal of Non-Closure Model
Authors: Kamaya Masayuki
Published: November 2019

Influence of the mean stress on fatigue life was investigated for carbon steel. Uni-axial fatigue tests were conducted by stress and strain-controlled conditions at room temperature. The fatigue life was reduced by applying the mean stress for the same stress amplitude. The fatigue life exhibited better correlation with the strain range rather than the stress amplitude. Increase in strain range caused by applying the mean stress correlated well with the decrease in the fatigue life. It was assumed that the mean stress effect on the fatigue life was brought about by the change in crack growth rate caused by applying the mean stress. The mean stress enhanced crack mouth opening and accelerated the crack growth. The non-closure model, in which the crack mouth is assumed not to be closed even at the minimum peak stress, was proposed.
A Kriging-Based Surrogate Model for Seismic Fragility Analysis of Unanchored Storage Tanks
Authors: Phan Hoang Nam , Paolacci Fabrizio , Corritore Daniele , Tondini Nicola , Bursi Oreste S.
Published: November 2019

The seismic vulnerability of aboveground steel storage tanks has been dramatically proved during the latest seismic events, which demonstrates the need for reliable numerical models for vulnerability and risk assessments of storage facilities. While for anchored aboveground tanks, simplified models are nowadays available and mostly used for the seismic vulnerability assessment, in the case of unanchored tanks, the scientific community is still working on numerical models capable of reliably predicting the nonlinearity due to uplift and sliding mechanisms. In this paper, a surrogate model based on a Kriging approach is proposed for a case study of an unanchored tank, whose calibration is performed on a three-dimensional finite element (3D FE) model using a reliable design of experiments (DOE) method. The verification of the 3D FE model is also done through a shaking table campaign. The outcomes show the effectiveness of the proposed model to build fragility curves at a low computational cost of the critical damage state of the tank, i.e., the plastic rotation of the shell-to-bottom joint.
A Thermal-Mechanical Analysis Model for Composite Overwrapped Pressure Vessel for Hydrogen During Fast Filling
Authors: Jiang Y. , Xu M. , Fan Zhichao , Xuedong Chen , Wu Q. G.
Published: November 2019

Composite overwrapped pressure vessel (COPV) is considered to be the most promising storage tank for hydrogen. Filling the COPV to high pressure within 3–5 minutes generates temperature increment due to negative Joule-Thomson coefficient and compression effect of hydrogen. This temperature increment induces a non-uniform temperature distribution in the COPV. The difference between the physical properties of inner metallic liner and outer composite will produce thermal stress. In this work a computational fluid dynamics (CFD) model is built to simulate the temperature increment during fast filling of the COPV. A three-dimensional thermal-mechanical finite element model for COPV is set up. The temperature distribution of the COPV by the CFD model is input into the thermal-mechanical model to analyze the stress distribution during the fast filling. This thermal-mechanical analysis model will provide technical support for the design of COPV.
Limit Load Solutions of the Orthotropic Thick-Walled Pipe Subjected to Internal Pressure, Bending Moment and Torsion Moment
Authors: Xu Min , Zhao Yujie , Zhou Binbin , He Xiaohua , Zhou Changyu
Published: November 2019

Based on the Hill yield criterion, the analytical solutions of the limit load of orthotropic thick-walled pipes under pure internal pressure, bending moment and torsion are given respectively. The simplified Mises analytical solution and finite element results of limit load for isotropic thick-walled pipe are obtained. The solution verifies the reliability of the analytical solution. The paper discusses the difference of limit load of isotropic and orthotropic pipes under the conditions of pure internal pressure, pure bending moment and pure torsion moment. It is concluded that the influence of material anisotropy on the limit load is significant. The limit load of pipe under pure internal pressure is mainly determined by circumferential yield strength, pure bending is only related to axial yield strength and pure torsion moment is related to the yield strength in the 45° direction and radial yield strength.
Random Excitation PSD Model Acting on Heat Exchanger Tube Bundle Under Two Phase Flow Condition
Authors: Nishida Shingo , Kawakami Ryoichi , Hirota Kazuo , Morita Hideyuki , Azuma Seinosuke , Kondo Yoshiyuki , Komuro Yoshiteru
Published: November 2019

A considerable amount of time and dedication have been devoted into the development of an unified non-dimensional random excitation forces (Power Spectrum Density) PSD model of tube bundles into two phase flow conditions. However, any model cannot be used for wide-range two phase flow conditions as random excitation forces depends strongly on a two phase flow regime. Therefore, we have developed a new scaling method for a two phase random excitation force PSD to be applicable for a wide-range of flow conditions. This method has been developed by focusing on the correlation between a two phase pressure loss and two phase turbulence energy. Comparisons of non-dimensional random excitation force PSDs in various conditions scaled by using the developed method, showed a good concordance between the two.
Finite Element Modeling of Hybrid Friction Diffusion Welding of Tube-Tubesheet Joints
Authors: Al-Badour Fadi
Published: November 2019

Hybrid Friction Diffusion Bonding (HFDB) is a solid-state welding process that proved its capability of producing sound tube-tubesheet joints, but with limitations on tube thickness (up to 1mm) and tube-tubesheet materials. In the petrochemical industry, there is a great demand for the use of carbon steel shell and tube heat exchangers. To investigate the feasibility of HFDB techniques in joining thicker tube (i.e 2.1 mm) on tubesheet joint, a three-dimensional thermo-mechanical finite element model (FEM) was developed and solved using ABAQUS (commercial finite element analysis (FEA) software). The model was used to predict the temperature distribution and developed stresses during and after welding. The model considered temperature dependent material properties while Johnson-cook model was used to govern material plastic flow behavior. In this paper,19 mm (¾ in) ASTM 179 cold-drawn carbon steel tube into an ASTM A516 Grade 70 tubesheet joints was simulated. Results are validated based on temperature measurements, which was found in good agreement with experimental results. The developed model can be used to optimize processing parameters (i.e. tool rotational speed, dwell time “holding time”, and forging force.. etc) and study their effect on material flow and developed stresses.
Evaluation of Creep Properties of Alloy 690 Steam Generator Tubes at High Temperature Using Tube Specimen
Authors: Kim Jongmin , Kim Woogon , Kim Minchul
Published: November 2019

Thermally induced steam generator (SG) tube failures caused by hot gases from a damaged reactor core can result in a containment bypass event and may lead to release of fission products to the environment. A typical severe accident scenario is a station blackout (SBO) with loss of auxiliary feedwater. Alloy 690 which has increased the Cr content has been replaced for the SG tube due to its high corrosion resistance against stress corrosion cracking (SCC). However, there is lack of research on the high temperature creep rupture and life prediction model of Alloy 690. In this study, creep test was performed to estimate the high temperature creep rupture life of Alloy 690. Based on reported creep data and creep test results of Alloy 690 in this study, creep life extrapolation was carried out using Larson-Miller Parameter (LMP), Orr-Sherby-Dorn (OSD), Manson-Haferd Parameter (MHP), and Wilshire’s approach. And a hyperbolic sine (sinh) function to determine master curves in LMP, OSD and MHP methods was used for improving the creep life estimation of Alloy 690 material.
Development of Chinese Standard on Ultrasonic Inspection for Electrofusion Joint of Polyethylene Pipe
Authors: Guo Weican , Tao Yangji , Shi Jianfeng , Miao Cunjian , Zhong Haijian , Zheng Jinyang
Published: November 2019

Polyethylene (PE) pipe has been widely used in the transportation natural gas, and electrofusion (EF) welding is a welding method commonly used in the welding of polyethylene pipes. Defects are likely to occur in electrofusion joints, which lead to significant casualties and economic losses if PE pipes failed during service. However, the assessment of electrofusion joints is made by visual inspection and destructive testing, which can’t detect internal defects directly. This paper introduces two recently developed Chinese standards for nondestructive testing and safety assessment of electrofusion joints. These standards illustrate inspection process, sample block, defect characterization and safety assessment. Some research, applying these standards for inspection and safety assessment of electrofusion joint, is introduced in this paper. Those researches show that ultrasonic detection technology in these standards is suitable for defects inspection, and standards provide standard technical support for the safety of polyethylene pipelines.
Integrity Mitigation Prioritization Using Multi-Criteria Decision-Making
Authors: Mehranfar Mahsa , Mejia Juan , Hassanien Sherif , Martin James
Published: November 2019

In-line Inspection (ILI) tools are regularly used for inspecting transmission pipelines. However, it is challenging to use such technology for a large portion of pipes; e.g. terminals and pumping stations, because of diameter changes, tight turns, or other pipe/inspection characteristics. Non-contact pipeline magnetic testing (NPMT) is a well-suited technique to inspect potentially non-ILI pipes. This paper presents a new framework for selecting and prioritizing digs-based LSM high severity features. A multi-criteria decision-making approach was developed using pair-wise comparisons which stems from the Analytical Hierarchy Process (AHP). AHP is a structured technique for organizing and analyzing complex decisions to help the decision maker set priorities and make the best decision given available information. In addition to the application of AHP, a cost benefit analysis and evaluation of risk have been conducted in order to support a risk-informed decision-making for selecting the top priority digs. Pipe properties, LSM tool reported data and Subject Matter Expert (SME) opinion were utilized in order to efficiently render a decision regarding prioritization of dig sites.

The developed approach can be used as a regular process to prioritize similar dig programs. This method is capable of ranking different dig sites based on SME opinion as well as construction information and LSM reported data.
Assessment of Structural Integrity on Irradiated Steel Structure: Focusing on Long Column Type Reactor Pressure Vessel Supports
Authors: Han Goeun , Guzey Sukru
Published: November 2019

The structural steel in a nuclear facility experiences significant degradation due to the accumulated neutron irradiation. Particularly, the long-column type reactor pressure vessel supports have been focused since they resist considerable loading to maintain the primary coolant system in their position and experience high neutron irradiation in low temperature, which is an unfavorable condition for the fracture toughness. This study implemented the API 579-1/ASME FFS-1, fitness-for-service (FFS) method to consider both irradiated mechanical properties and multiple loading cases. A three-dimensional (3D) finite element model of long column type reactor pressure vessel support was built for the linear analysis. The metallurgical properties of reactor pressure vessel support for assessment were estimated by empirical equations. This study provides the structural margin of long-column type reactor pressure vessel support by levels of the loads and levels of the neutron fluence.