bluuebunny/crossref_metadata_2025_split huggingface dataset:
Strain-Controlled Low Cycle Fatigue of Stainless Steel in PWR Water
Authors: Seppänen Tommi , Alhainen Jouni , Arilahti Esko , Solin Jussi 
Published: November 2019

Abstract
Fatigue is a major degradation mechanism and life-limiting factor for primary circuit piping. High temperature, pressurized reactor coolant aggravates fatigue damage with a suitable combination of loading parameters. Nonstandard test methods, incompatible with design codes and the peculiar material behaviour of austenitic stainless steel have been widely used. This complicates quantification of the effect of water environment, commonly referred to as the Fen factor.
Four test series in simulated PWR coolant were completed over four years with stainless steel alloys 347 and 304L, hypothesizing that Fen=f⁡ε.pl. Linear strain waveforms were used with non-constant strain rate to represent simplified plant transients and non-realistic mirrored strain waveforms for comparison purposes. Applying multiple strain rates allows identifying potentially non-damaging effects of effectively elastic strain near the valley of a strain cycle and on the other hand the damaging effect of effectively plastic strain.
Results generated within this project were used to draft a replacement to the Fen methodology presented in NRC report NUREG/CR-6909. Initially, this model remains based on total strain rate and is presently limited to the narrow parameter window in which valid experiments were performed. It does however reduce the scatter and unnecessarily high conservatism associated with the NUREG Fen by a factor of approximately two. This paper presents new results for 304L and an outline of the draft model proposal for Fen evaluation in PWR water.
Influence of the Pitch-to-Diameter Ratio on Two-Phase Flow-Induced Forces Across a Tube Bundle
Authors: Deri Enrico 
Published: November 2019

Abstract
Flow-induced vibrations of Steam Generator tube bundles are a major concern for the operators and designers of nuclear power plants. In order to predict damages due to such vibrations, predictive calculations are performed, both by designers and by operators, which allow one to evaluate safety margins and thereafter to optimize the SG maintenance policy.
In cases when semi analytical models of fluid-dynamic forces are used, together with corresponding dimensionless fluid force coefficients, closures are assessed by experiment. The database of dimensionless coefficients should then cover relevant tube bundle configurations.
Within this framework, a test rig which was available at EDF was modified in order to arrange different pitch-to-diameter ratio bundles and different tube diameters. This paper discusses the fluid-induced forces measured on a set of flexible tubes placed in a triangular pitch bundle both in the lift and drag directions. Two-phase flow excitation spectra are presented as well.
Simulation of Sloshing Wave Crest Impact Acting on a Fixed Roof Cylindrical Tank Subjected to a Sinusoidal Excitation
Authors: Toyoda Yukihiro , Ohtori Yasuki 
Published: November 2019

Abstract
This paper describes the applicability of an open source code “OpenFOAM” on estimating of sloshing wave crest impact pressure acting on a fixed roof of cylindrical tank. Based on the computed results, slosh-induced pressure loads and distribution on the tank roof is presented. A series of large scale tests, which are conducted on the “E-defence” shaking table, has been analyzed. In the shaking table tests, partially water-filled cylindrical tank (diameter/height:3m, water depth:2.3m/1.9m) with the flat fixed roof was subjected to a sinusoidal excitation at the first sloshing resonant frequency. The computer code well simulated the observed waveform with a sharp pressure peak at the time of liquid impact on the tank roof, including appearance of negative pressures in the post impact period, with sufficient accuracy. As for the liquid impact zone of the tank roof, the numerical results indicated good agreement with the observed ones. Consequently, the computer code was capable of predicting the complex nonlinear sloshing behavior with the collision of the liquid surface against the tank roof with an acceptable level of accuracy.
Piping Vibration of Multi-Treater System in OCU Process Plant
Authors: Park Jae-Yeol , Kim Manjin , Han Minkyu 
Published: November 2019

Abstract
Acoustic-Mechanical coupling effect on piping dynamics is examined on site with measurement and analytical development. In this article, a multi-treater piping system in OCU (Olefin Conversion Unit) plant is subjected to investigation since significant piping vibration prevents the normal operation when some specific combinations of two treaters are operated. There is severe piping and structure vibration problem especially with increased capacity. Measurement in frequency domain shows two peaks so close each other to result in high amplitude in the piping system vibration by beating phenomenon. In search of solution, extra safety valve is manually opened to increase the acoustic volume which changes the acoustic natural frequency in the subjected piping system and decrease the vibration. Analytical study with acoustic analysis software is also conducted and it shows the same results as the actual piping dynamics. Based on the acoustic study, piping modification is designed and applied to the piping system and vibration improvement is achieved as expected.
Study on the Predictive Evaluation Method of Nonlinear Sloshing Wave Crest Impact Load on the Roof of Cylindrical Tanks
Authors: Morita Hideyuki , Takata Tomoshige , Madokoro Hideki , Sago Hiromi , Yokoi Shinobu , Yamamoto Tomohiko 
Published: November 2019

Abstract
When cylindrical tanks installed on the ground, such as oil tanks and liquid storage tanks, receive strong seismic waves, including the long-period component, motion of the free liquid surface inside the tank called sloshing may occur. If high-amplitude sloshing occurs and the waves collide with the tank roof, it may lead to accidents such as damage of the tank roof or outflow of internal liquid of the tank. Therefore, it is important to predict the wave height of sloshing generated by earthquake motion.
Sloshing is a type of vibration of free liquid surface, and if the sloshing wave height is small, it can be approximated with a linear vibration model. In this case, the velocity-response-spectrum method using velocity potential can estimate the sloshing wave height under earthquake motion. However, if the sloshing wave height increases, the sloshing becomes nonlinear, and necessary to evaluate the wave height using other methods such as numerical analysis.
Design earthquake magnitude levels in Japan tend to increase in recent years, long-period components of earthquake wave which act on the sloshing wave height also increase instead of introducing seismic isolation mechanisms. To evaluate sloshing wave crest impact load acting on the roof of a tank, there are few applications which quantitatively evaluated the crest impact load of nonlinear sloshing.
To construct a simple technique to evaluate the sloshing impact load considering the nonlinear sloshing wave height which acts on a flat roof of cylindrical tanks, it is proposed that flow diagram of evaluating the sloshing impact load which newly took into consideration the nonlinearity of sloshing and the dynamic amplification factor. The applicability of the technique was verified with the shaking table tests results for cylindrical tank and flow-analysis results.
Fracture and Deformation Behavior in Slow-Strain-Rate Tensile Testing of Cu–Ni Alloy With Internal Hydrogen
Authors: Wada Kentaro , Yamabe Junichiro , Ogawa Yuhei , Takakuwa Osamu , Iijima Takashi , Matsunaga Hisao 
Published: November 2019

Abstract
The effect of hydrogen on the deformation and fracture behavior in pure Cu, pure Ni and Cu–Ni alloy was studied via tensile tests of H-charged, smooth and circumferentially-notched specimens at room temperature (RT) and 77 K. Hydrogen-diffusion properties were determined by the desorption method. To obtain a uniform hydrogen concentration in the H-charged specimens, specimens were exposed to 100-MPa hydrogen gas at 543 K for 200 h, based on the determined hydrogen diffusivity. In tensile tests of smooth pure Ni and Cu–Ni alloy specimens at RT, common hydrogen effects were detected, namely, an increase in yield and flow stresses — a hardening effect; and a ductility loss that was accompanied by a change in fracture surface from ductile to brittle feature — an embrittling effect. With regard to the embrittling effect, the pure Ni and Cu–Ni alloy showed different fracture-surface morphologies at RT; the pure Ni showed an intergranular (IG) surface and the Cu–Ni alloy surface was flat. However, a number of IG cracks were detected beneath the fracture surfaces on the smooth Cu-Ni alloy. The tensile tests of the H-charged smooth specimens at 77 K yielded an IG surface for the pure Ni and a ductile fracture surface with dimples in the Cu–Ni alloy. In contrast, tensile tests of the H-charged, notched specimens at RT demonstrated clear IG fractures for the pure Ni and Cu–Ni alloy. These facts indicate that IG cracking was the first step in the embrittling process for the pure Ni and Cu–Ni alloy, and IG cracking was accompanied by a large plastic deformation that formed the flat surface (unclear IG surface) for the smooth Cu–Ni alloy. Considering that the HE of both pure Ni and Cu–Ni alloy was related to IG cracking, possible mechanisms were discussed and tensile tests performed at 77 K suggested two possibilities: (I) interaction between hydrogen-moving dislocation is more important in the HE process of the Cu-Ni alloy compared to the pure Ni; (II) hydrogen transportation towards grain boundaries are required to cause the IG fracture in the Cu-Ni alloy.
Limits of Allowable Static and Cyclic Loads on Lens Ring Gaskets
Authors: Maderbacher Hermann 
Published: November 2019

Abstract
Due to their relative simple handling and the high reliability, lens ring gaskets are widely used in high pressure connections. In addition, they are able to withstand large external forces without being damaged but at the same time they do not lose leak tightness even with very small contact forces. This ability to withstand high loads allows a lens ring gasket to be reused several times with minimal polishing after disassembling the flange connection.
However, this reusability has its end when the lens ring gasket is damaged or destroyed by static or cyclic overload. Static overload is mainly caused by too high bolt tightening force and leads to large scale plastic deformation. This damage can be easily avoided by choosing the correct bolt preload and proper flange alignment. A greater difficulty is the damage prediction by cyclic overload. This is caused by pressure fluctuations, excitations in the range of natural frequencies or other external cyclic loads. The effects of these mentioned loads on the service life of the lens ring gasket additionally depend on factors such as the stiffness of the individual components of the flange connection, the initial bolt preload or the materials used.
In the present work a method is presented which is able to predict the load limits of lens ring gaskets under static and cyclic loading. This method allows the consideration of different geometric influences of the individual components, of different materials and bolt preloads. From the static and cyclic forces on the flange connection, local stresses in the lens ring are calculated. This enables making a statement regarding plastic deformation due to bolt load and fatigue failure due to cyclic loads.
A Study on the Reuse of Xylan 1424 Studs
Authors: Ruffin Mark 
Published: November 2019

Abstract
While there are many factors that should be considered when determining if a stud can be reused, one of them is the nut factor. The study described in this paper set out to determine if the nut factor of a Xylan 1424 coated stud is significantly affected by the age of the coating and/or the cycles of tightening. A load cell was used to compare the nut factor: 1) of previously installed (used) studs to new studs, 2) of a new and used stud that were tightened more than once, and 3) associated with the first tightening pass to subsequent passes for a new stud. The results show that the age of the stud and the amount it has been tightened contribute to an increased nut factor for used Xylan 1424 studs.
Overview of Current Practice for Analysis and Design of Independent Spent Fuel Storage Installation Pads
Authors: Kwon Gunup , Ata Khaled 
Published: November 2019

Abstract
Nuclear power plant spent fuels are initially stored in the spent fuel pool. Then, the water cooled fuels are transferred in a concrete or steel cask and transported outside of the Fuel Handling Building (FHB) or the Reactor Building (RB) for long term on site storage. The spent fuel casks are typically stored on a slab-on-grade pad. The slab-on-grade pad is designed according to the U.S. Nuclear Regulatory Commission NUREG-1536 and NUREG-1567. The two Standard Review Plans provide guidance to the regulators for the review of cask storage system license application. The ISFSI pad analysis and design have to consider various loading conditions, such as earthquake and tornado loadings as well as normal operating loading conditions. Seismic analysis of the ISFSI pad requires considering interaction between the pad and the supporting soil. Various cask loading configurations on the pad also have to be considered. Due to the lack of specific guidelines, many ISFSI pad designs show overly conservative reinforcement. This study provides guidelines and procedure for the design of the ISFSI pad that are typically used in the nuclear industry. It is considered that the guidelines and practices described in this study help design engineers understand general guidance provided in the NRC Standard Review Plans.
Auxiliary Beam Stress Improved Laser Welding for Repair of Irradiated Light Water Reactor Components
Authors: Chen Jian , Tatman Jonathan , Feng Zhili , Miller Roger , Tang Wei , Gussev Maxim , Leonard Keith , Sutton Benjamin , Frederick Greg 
Published: November 2019

Abstract
The welding task focuses on development of advanced welding technologies for repair and maintenance of nuclear reactor structural components to safely and cost-effectively extend the service life of nuclear power reactors. This paper presents an integrated research and development effort by the Department of Energy Light Water Reactor Sustainability Program through the Oak Ridge National Laboratory (ORNL) and Electric Power Research Institute (EPRI) to develop a patent-pending technology, Auxiliary Beam Stress Improved Laser Welding Technique, that proactively manages the stresses during laser repair welding of highly irradiated reactor internals without helium induced cracking (HeIC). Finite element numerical simulations and in-situ temperature and strain experimental validation have been utilized to identify candidate welding conditions to achieve significant stress compression near the weld pool during cooling. Preliminary welding experiments were performed on irradiated stainless-steel plates (Type 304L). Post-weld characterization reveals that no macroscopic HeIC was observed.
Numerical Surrogate Model of a Coupled Tank-Piping System for Seismic Fragility Analysis With Synthetic Ground Motions
Authors: di Filippo Rocco , Abbiati Giuseppe , Sayginer Osman , Covi Patrick , Bursi Oreste S. , Paolacci Fabrizio 
Published: November 2019

Abstract
Seismic risk evaluation of coupled systems of industrial plants often needs the implementation of complex finite element models to consider their multicomponent nature. These models typically rely on significant computational resources. Moreover, the relationships between seismic action, system response and relevant damage levels are often characterized by a high level of nonlinearity, thus requiring a solid background of experimental data. Furthermore, fragility analyses depend on the adoption of a significant number of seismic waveforms generally not available when the analysis is site-specific. To propose a methodology able to manage these issues, we present a possible approach for a seismic reliability analysis of a coupled tank-piping system. The novelty of this approach lies in the adoption of artificial accelerograms, FE models and experimental hybrid simulations to evaluate a surrogate meta-model of our system. First, to obtain the necessary input for a stochastic ground motion model able to generate synthetic ground motions, a disaggregation analysis of the seismic hazard is performed. Hereafter, we reduce the space of parameters of the stochastic ground motion model by means of a global sensitivity analysis upon the seismic response of our system. Hence, we generate a large set of synthetic ground motions and select, among them, a few signals for experimental hybrid simulations. In detail, the hybrid simulator is composed by a numerical substructure to predict the sliding response of a steel tank, and a physical substructure made of a realistic piping network. Furthermore, we use these experimental results to calibrate a refined ANSYS FEM. More precisely, we focus on tensile hoop strains in elbow pipes as a leading cause for leakage, monitoring them with strain gauges. Thus, we present the procedure to evaluate a numerical Kriging meta-model of the coupled system based on both experimental and finite element model results. This model will be adopted in a future development to carry out a seismic fragility analysis.
Variables Affecting Nut Factors in Bolted Flange Connections
Authors: Aycock Justin B. , Wilson Jeffery , Bausman Anita 
Published: November 2019

Abstract
Bolted flange connections are heavily used within the chemical production/processing, transportation, marine, and power generation industries to contain processes while minimizing leaks. These leaks could cause unsafe working conditions, environmental hazards, and/or loss of product which, in turn, can cause fines or higher operating cost for plants. A way to deter this from happening is to correctly load the fasteners of the bolted flange connections to ensure the fasteners are properly stretched to apply an adequate contact stress to the gasket. Good understanding of how bolted flanged connections are optimally loaded limits leakage. When applying load via controlled torque to a fastener, the torsional energy applied is translated into a perpendicular force acting on the nut’s face and threads that is mirrored on the other side of the fastener thus inducing the clamping force on the connection. To determine the clamping force generated from the applied torque, a typical torque equation is applied using an empirically derived composite friction term called the nut factor. The nut factor is a dimensionless constant that includes all of the friction effects in the torque-clamping force relationship. The friction occurs between the surfaces of bolt and nut threads and the faces of the nut and flange or washer. The higher the friction, the higher the nut factor resulting in a higher fastener torque to achieve the same clamping force load. This study looked at several variables that can cause changes in assembly nut factor magnitude including bolt grade, bolt load, lubrication, washer presence, and bolt diameter.
Direct-Current Electric Potential (D-C EP) Technique Validation Through an Experimental and Computational Study on Pipe With Surface Crack
Authors: Hioe Y. , Kalyanam S. , Wilkowski G. , Brust F. W. , Punch E. 
Published: November 2019

Abstract
The direct-current electric potential (d-c EP) technique (also known as Electrical Potential Drop, EPD) was developed by researchers in the 1960s and applied to cracked geometries. In this investigation, measurement of the d-c EP signature from a circumferential surface-crack profile in a pipe was attempted to characterize the flaw shape with higher resolution using state-of-the-art digital equipment. A part-circular profile of crack was inserted using an EDM technique in a small diameter (4-inch diameter Schedule 160) TP304 (Type304) stainless steel pipe. Experimentally, different magnitudes of electric-current were applied to obtain the d-c EP across the length of the crack (from the shallowest to the deepest point). Finite Element Analysis (FEA) was performed to calculate the variation of the d-c EP across the length of the crack. A sensitivity study was done for various distances between the d-c EP probe locations near the crack. A comparison of the d-c EP values obtained from the part-circular crack front and a semi elliptical crack FEA (more realistically seen/assumed in service crack cases and used in the ASME Section XI calculations) were made. The study also investigated the variation of the d-c EP for various crack depths through the thickness for the applied constant amplitude direct-current. The sensitivity on d-c EP probe location distance from the surface flaw and d-c EP probe location along the length of the surface flaw (from deepest or center of the surface flaw to the shallowest point or corner of the surface flaw) were investigated. The scatter in the acquired d-c EP data across the two sides of the crack was investigated and accuracy of crack depth characterization was characterized in detail. This was done to investigate the limits of d-c EP calibration curves used for crack growth predictions.
The d-c EP calibration curves are useful in determining the crack growth that occurs without destructively opening the specimen and also measuring the in-situ crack depth measurements real time during a pipe or other surface flawed component/fitting experiments.
Computations of Single and Multiphase Flows Using a Lattice Boltzmann Solver
Authors: Akhtar M. Wasy , Love Holley C. 
Published: November 2019

Abstract
There is considerable interest in high fidelity simulation of both single phase incompressible flows and multiphase flows. Most commonly applied numerical methods include finite difference, finite volume, finite element and spectral methods. All of these methods attempt to capture the flow details by solving the Navier–Stokes equations. Challenges of solving the Navier–Stokes single phase incompressible flows include the non-locality of the pressure gradient, non-linearity of the advection term and handling the pressure-velocity coupling. Multiphase flow computations pose additional challenges, such as property and flow variable discontinuities at the interface, whose location and orientation is not known a priori. Further, capturing/tracking of the multiphase interface requires solution of an additional advection equation. Recently, the lattice Boltzmann method has been applied to compute fluid dynamics simulations both for single and multiphase configurations; it is considered a modern CFD approach with improved accuracy and performance. Specifically, we employ a multiple-relaxation time (MRT) technique for the collision term on a D3Q27 lattice. The multiphase interface is captured using the phase-field approach of Allen-Cahn. Test cases include lid driven cavity, vortex shedding for a double backward facing step, Rayleigh Taylor instability, Enright’s deformation test and rising bubble in an infinite domain. These test cases validate different aspects of the single and multiphase model, so that the results can be interpreted with confidence that the underlying computational framework is sufficiently accurate.