bluuebunny/crossref_metadata_2025 huggingface dataset:
Progress in ITER Project and Its Superconducting Magnet System in Japan
Authors: Okuno Kiyoshi , Nakajima Hideo , Takahashi Yoshikazu , Koizumi Norikiyo
Published: July 2010

The ITER Agreement was signed on 21 November 2006 and the ITER Organization (IO) was officially started. IO undertook a Design Review of ITER and the ITER baseline design was established as a basis for starting construction, together with the reference Integrated Project Schedule. In parallel, Japan Atomic Energy Agency (JAEA) performed extensive development work as procurement preparation including TF conductor, TF coil winding and TF coil structures. Based on the achievements from these developments, JAEA started the actual procurement from March 2008 by placing contracts on the industries in line with the Integrated Project Schedule.
ARCMAC Optical Strain Measurement for Creep Monitoring: Recent Improvements in Accuracy and Resolution
Authors: Morris Andy , Palmer Iain , Maharaj Chris , Puri Amit , Dear John
Published: July 2010

Remaining life of power station high pressure steam pipes is heavily dependant upon material creep rates. However, due to the difficulty in monitoring strain in these pipes as a result of the demanding operational conditions, a rugged optical strain gauge system has been developed. The current E.ON UK ARCMAC gauge system has been validated using the UK National Physical Laboratory standard grade extensometer and provides a strain measurement accuracy of 64 micro-strain with an error of <10%. This system uses precision optics, a CCD camera and a light source system to capture images of uniaxial and biaxial optical strain gauges on steam pipes during periodic maintenance. Further developments of the ARCMAC system have included the design, manufacture and validation of an advanced ARCMAC optical measurement system with improved sensor resolution and improved accuracy. Additionally, the methodology of image processing has been studied in order to reduce errors in both the existing and the new ARCMAC systems. Finally, Digital Image Correlation (DIC) has been used alongside ARCMAC gauges to monitor strain fields around welds and defects in steam pipes. Some of these techniques have also been used in a related study into strain monitoring in wind turbine blades.
High Temperature Pipeline Cracking Cause Analysis of a Synthetic Ammonia Reforming Furnace
Authors: Fan Zhichao , Chen Xuedong , Pan Jianhua , Chen Tao
Published: July 2010

Some cracks were detected in elbow welds of a high-temperature pipeline in a synthesis ammonia reforming furnace which has served for about two years at 650°C. The pipeline material is TP321H stainless steel. The maximum crack with a length larger than 130mm is located in the center of the circumferential weld. In this paper, FEM analysis of this pressure pipeline is carried out by the ABAQUS software, and the results indicate that the design parameters satisfy Chinese standard. By such measures as welding process analysis, chemical analysis, mechanical properties testing, optical microscopy, scanning electron microscopy, X-ray diffraction, the pipeline cracking cause is found to be the relatively poor welding quality, namely welding is fully deviated from the welding process, resulting in severe stress concentration and some welding reheat cracks. Additionally, during the installation and operation periods of the pipeline, abundant σ-phases were precipitated in grain boundaries, inducing a great plasticity and toughness losses of welds. Micro-cracks initiated from inside at some locations with relatively high stress, propagated intermittently towards outside along the grain boundary with rich σ-phases, and finally penetrated the whole pipeline wall. In the end, some suggestions are also presented to ensure the safe operations of this pressure pipeline.
Buckling Analysis of an Orthotropic Elliptical Toroidal Shell
Authors: Redekop D.
Published: July 2010

A theoretical solution is given for the linearized buckling problem of an orthotropic toroidal shell with an elliptical cross-section under external pressure loading. The solution is based on the Sanders-Budiansky shell theory, and makes use of the harmonic differential quadrature method. Theory developed earlier for the buckling of orthotropic shells of revolution, and the vibration of orthotropic elliptical toroidal shells, is incorporated in the present work. Numerical results obtained from the solution are compared with results given in the literature, and good correspondence is generally observed. A parametric study is then conducted, covering a wide range of material and geometric parameters. Regression formulas are derived, indicating the variation of the buckling pressure with the degree of orthotropy of the material. Overall, the study introduces a new tool for the buckling analysis of elliptical toroidal shells, and extends the information available for orthotropic toroidal shells.
CFD Modeling of Flow Induced Vibration on a Mobile Cylinder for a 30 K-60 K Reynolds Number Comparison Between Simulation and Experimental Results
Authors: Peyrard Christophe , Belloli Marco , Bousseau Pierre , Muggiasca Sara , Giappino Stefano , Howard Richard , Rocchi Daniele
Published: July 2010

Fatigue and aging of electrical overhead transmission lines is a major concern nowadays in developed countries with ever increasing difficulties to build new lines and an already quite aged network. An important degradation phenomenon of overhead line cables is fretting fatigue close to the suspension clamps due to vortex induced vibrations (VIV). These VIV are generally observed for wind speeds in the range of 1 to 7 m/s. The existing industrial practice for predicting how prone cables are to VIV fatigue is based on a balance between the power generated by the wind and the power dissipated by the cable system. The power generated by the wind has been evaluated through measurements on real line spans and through wind tunnel experiments on rigid and flexible cylinders as a function of frequency and vibration amplitude. The wind tunnel measurement results are mainly performed for constant flow speed. Corresponding results show a scattering from simple to double. Furthermore, complementary investigations are required to better evaluate the power with wind speed variations across and along the overhead line span. EDF R&D (with Code_Saturne open source software) and Politecnico di Milano have evaluated CFD modeling on a mobile rigid cylinder with comparison to detailed wind tunnel measurement results performed by Politecnico di Milano on a 20 cm diameter rigid cylinder equipped with a pressure scanner. This paper presents the steps, the different questions raised, the difficulties and limitations for the setting and the realization of the CFD modeling approach. The comparison between experimental results and simulation results is presented for the mobile rigid cylinder with k-ω SST turbulence model.
Evaluation of Wall Thinning Rate Due to Flow Accelerated Corrosion With the Coupled Models of Electrochemical Analysis and Double Oxide Layer Analysis
Authors: Naitoh Masanori , Uchida Shunsuke , Uehara Yasushi , Okada Hidetoshi , Koshizuka Seiichi
Published: July 2010

Systematic approaches for evaluating flow accelerated corrosion (FAC) are desired before discussing application of countermeasures for FAC. Future FAC occurrence should be evaluated to identify locations where a higher possibility of FAC occurrence exists, and then, wall thinning rate at the identified FAC occurrence zone should be evaluated to obtain the preparation time for applying countermeasures. Wall thinning rates were calculated with the coupled models of static electrochemical analysis and dynamic double oxide layer analysis. Anodic current density and electrochemical corrosion potential (ECP) were calculated with the electrochemistry model based on an Evans diagram and ferrous ion release rate determined by the anodic current density was applied as input for the double oxide layer model. The thickness of oxide layer was calculated with the double oxide layer model. The dependences of mass transfer coefficients, oxygen concentrations ([O2]), pH and temperature on wall thinning rates were calculated with the coupled model. It was confirmed that the calculated results of the coupled models resulted good agreement with the measured ones. The effects of candidates for countermeasures, e.g., optimization of N2H4 injection point into the feed water system, on FAC mitigation was demonstrated as a result of applying the model.
A Study of Developing Composite Material of Penetrated Diamond Particles Into Metal Plate
Authors: Nishi Keijiro , Tanaka Shigeru , Itoh Shigeru
Published: July 2010

An explosive welding technique which uses underwater shock wave to weld thin aluminum plate has been studied and the technical advantages were reported. In this research, we propose a method to produce a composite material using an underwater shock wave generated by detonation of explosive. In the production process, a metal plate (flyer plate) accelerates to a high speed by the underwater shock wave, and collided with diamond particles and penetrated the metal plate. Diamonds were used as the particles and aluminum plates (A1050) as the flyer plates. Diamond has high hardness and excellent thermal conductivity, therefore diamond should provide improvement in the thermal conductivity of the composite material. From recovered sample, the multilayer joined surface including diamond particles was observed using an optical microscope. The production of the pipe of composite materials was attempted using this technique as the application. Details of the experimental methods and results are reported in this paper.
Simulation of Creep/Relaxation Behavior in Bolted Flange Joints Based on 3-D Viscoelasticity Model of Gasket
Authors: Yamaguchi Atsushi , Tsuji Hirokazu , Honda Takashi
Published: July 2010

It is well known that an axial bolt force which tightens a gasket decreases due to a creep of non-asbestos gaskets. A bolted flange joint contains a combined condition of the creep/relaxation. A reduction behavior of a tightening pressure due to an effect of creep/relaxation is related to lifetime assessment of the non-asbestos gasket, and a leakage prevention of internal fluid. In this research, the creep/relaxation of the bolted flange joint using the non-asbestos gasket is measured. The compressed creep test is carried out using four-inch flanges and non-asbestos compressed fiber sheet gaskets. The test conditions are room temperature and 90 hours. The result of creep/relaxation is evaluated by 3-D viscoelasticity model. The creep/relaxation that was evaluated by 3-D viscoelasticity model and the Young’s modulus of the non-asbestos gaskets that was measured by the nanoindentation testing is applied to the FE analysis. FE model that include viscoelasticity is 1/16 of the test device. The stress state of the non-asbestos gasket was confirmed by the FE analysis. Then, the validity of creep/relaxation of the non-asbestos gaskets that was evaluated by the 3-D viscoelasticity model was shown by comparison with the experimental value and the analysis result.
Shaking Table Tests With Large Test Specimens of Seismically Isolated FBR Plants: Part 1—Response Behavior of Test Specimen Under Design Ground Motions
Authors: Kitamura Seiji , Morishita Masaki , Yabana Shuichi , Hirata Kazuta , Umeki Katsuhiko
Published: July 2010

The seismic isolation technology is planned to introduce to the next generation’s fast breeder reactor (FBR) plants in order to reduce seismic load subjected to components. To grasp the ultimate behavior of a seismically isolated plant under extremely strong earthquake at a level beyond the design ground motions and to establish ultimate strength design methods of seismic isolators, we made a series of shaking table test with large test specimen of seismically isolated FBR plants. The ultimate behavior test was performed using one of the world largest three-dimensional shaking tables “E-Defense” of National Research Institute for Earth Science and Disaster Prevention of Japan to obtain ultimate behavior data of a technologically-feasible large scale model. Test specimen consists of concrete blocks, reinforced concrete walls and isolation layer with six laminated rubber bearing with lead plug (LBR). The gross mass of upper structure of the test specimen is about 600ton. The diameter of the LRB is 505mm that reduced prototype dimensions to about 1/3. In this study, the following three behaviors were assumed as the ultimate behavior of the seismic isolation system; 1) loss of response reduction function of the isolation system by hardening of rubber, 2) non-linear response behavior by the cracking of the concrete wall and 3) braking of the LRB. When the input acceleration level increased, the test specimen was designed to show the ultimate behavior in the above-mentioned order. The ultimate behavior test of the seismic isolation system was carried out on the condition of two input waves by using two test specimen sets of the same dimensions. In this paper, details of the test specimen including the LRB and loading conditions are described. Response behavior of the test specimen under design ground motions is also reported. The restoring force characteristics of the LRBs were stable. The response acceleration of a horizontal direction measured at the upper structure of the specimen was reduced. Prior to the ultimate behavior tests with strong input waves, the response reduction functions of the test specimen under design ground motions were confirmed.
Effect of Uneven Crack Front on Crack Tip Mechanics and the Implication to Stress Corrosion Crack Growth
Authors: Xue He , Lu Zhanpeng , Murakami Hiroyoshi , Shoji Tetsuo
Published: July 2010

Uneven crack fronts have been observed in laboratory stress corrosion cracking tests. For example, cracking fronts of nickel-base alloys tested in simulated boiling water reactor (BWR) and pressurized water reactor (PWR) environments could exhibit uneven crack front. Analyzing the effect of an uneven crack front on further crack growth is important for quantification of crack growth. Finite-Element analysis shows that the local KI distribution can be significantly affected by the shape and size of the uneven crack front. Stress intensity factor at the locally extended crack front can be significantly reduced. Since generally there is a nonlinear CGR versus KI relationship, it is expected that crack growth rate at the locally extended crack front can be significantly different from those in the neighboring areas. There could be several patterns for the growth of an uneven crack front. For example, once initiated, the crack growth rate in areas other than the locally protruded front would become higher and then the whole crack front would tend to become uniform. On the other hand, if the crack growth in other areas is still low, there is a possibility that the crack growth rate at the front tip would slow down.
The Relationship Between Sealing Behavior of Gaskets and the Leak Tightness of Gasketed Bolted Flanged Connections
Authors: Kobayashi Takashi , Masui Kiichi , Soon Wong Teck
Published: July 2010

With the recent increase of a safety and environmental concern, the tightness of gasketed flanged connections becomes an important issue. In estimating the tightness of gasketed flanged connections, the sealing behavior of gaskets must be known. Currently, methods to test the sealing behaviors have been established in the North America, Europe and Japan. However, the relationships between the gasket data and the tightness of gasketed flanged connections have not been examined systematically. This paper consists of two parts: gasket data concerning sealing behavior and tightness of gasketed flanged connections. Firstly, several sheet gaskets were tested based on the test method JIS B 2490 in order to grasp tightness of gaskets. Secondly, tightness tests were carried out using blind flanges with the tested gaskets by JIS B 2490. Both the results were compared and discussed to highlight the relationship between them. It is shown that the tightness of bolted flanged connections is largely affected by the sealing behavior of gaskets. Based on the results, a simplified method to estimate the tightness of flanged connections is proposed.
Deformation Characteristics of Pipe Flanges Due to Bolt Loads and Internal Pressure
Authors: Kobayashi Takashi , Hamano Kota , Kikuchi Tsutomu , Sawa Toshiyuki , Nagata Satoshi
Published: July 2010

Deformation characteristics of pipe flanges are important in the leak rate based design of gasketed flanged connections. Not only the equilibrium of force between bolts and the clamped parts including flanges and a gasket but also the displacement between them should be considered in the design of gasketed flanged connections. Recently, finite element method (FEM) has widely been used in the analysis of flanged connections. However, analyses of pipe flanges based on the analytical method using classical theories such as the strength of materials are still important when parametric calculations of flanges are necessary. In this study, a method to analyze the stress and deformation of welding neck type flanges is demonstrated and the validity of the analysis is checked by experiment. A software using Visual Basic for Applications (VBA) is developed based on the method. The advantages of the software are that stresses and deformation of flanges are easily calculated by selecting a flange size and design conditions from a database. The validity of the results obtained by the software is also confirmed by comparing the calculated results with those obtained by FEA. A series of calculations have been done for Japanese Industrial Standard (JIS) flanges and the deformation characteristics are clarified when a flange is subjected to bolt loads and an internal pressure.
Mechanical Modeling of Multiple Trench Friction Pendulum System With Multi-Intermediate Sliding Plates
Authors: Tsai C. S. , Lin Yung-Chang , Tsai Wei-Chan
Published: July 2010

In order to upgrade the seismic resistibility of structures and enhance the functionality of an isolator, a new sliding type base isolator system called the multiple trench friction pendulum system (MTFPS) with multi-intermediate sliding plates is proposed. The MTFPS isolator is composed of a trench concave surface and numbers of intermediate sliding plates in each of two orthogonal directions. Mathematical formulations have been derived to examine its characteristics of the proposed MTFPS isolator. Based on mathematical formulations, it can be inferred that the natural frequency and damping effect of the MTFPS isolator change continually during earthquakes. Furthermore, results from shaking table tests demonstrate that the proposed isolator provides good protection to structures for preventing damage from strong earthquakes.
Study on Factors Important to Structural Integrity of Reactor Pressure Vessel During PTS With Regard to Fracture Probability
Authors: Onizawa Kunio , Matsuzawa Hiroshi
Published: July 2010

The structural integrity of RPV during PTS is assessed by considering important factors related to fracture mechanics analysis such as fracture toughness, PTS transient, and irradiation embrittlement prediction and so on. The effects of such factors have been evaluated with regard to the fracture probability of RPV using probabilistic fracture mechanics (PFM) analysis code PASCAL2. Results from sensitivity analyses on the variables in PFM analysis showed that the effect of fracture toughness curve is significant when the curve shape is different at high temperature range. Revised embrittlement correlation method gave slightly lower probability of fracture. The heat transfer coefficient for PTS transient and welding residual stress due to overlay cladding showed some effects to increase the probability of fracture. Uncertainties related to the shift of RTNDT with regard to the probabilistic variables such as chemical composition and neutron fluence are compared with the deterministic result with a margin.
Study on Two-Dimensions Base-Isolating Device for Reduction of Displacement by Using Friction Force
Authors: Makino Tomoyuki , Shintani Masanori
Published: July 2010

This paper deals with research of new isolation device with reduction of horizontal relative displacement by using friction force and reduction of vertical response acceleration and relative displacement by using spring and friction force. The isolation device is using a friction surface. The friction surface is subjected to acts on the slope plate. The restoring-force of horizontal direction is given to the isolation device from elastic force of a compression spring attached to the base. The restoring-force always works in the direction of the center. Therefore, the frictional force and the restoring-force are both proportional to the displacement. The restoring-force of the vertical direction is given to the isolation device from compression springs and draft springs. Simulation analysis was performed under various conditions using this analysis model. Condition reducing both response acceleration and displacement effectively is calculated on various conditions using the analysis model. Furthermore, an experiment is conducted using the experimental device. The experiment is conducted by an imagination wave. Analysis is also conducted on the same conditions. The results of the experiment are compared with the results of the analysis. The performance of the isolation device is examined. The validity of an analysis model is examined. As a result of conducting the analysis and an experiment with this model, it was shown that response acceleration and relative displacement can be reduced successfully. The validity of an analysis model is shown. Next, it analyzes by actual seismic waves. The performance of isolation equipment in actual seismic waves is examined and shown.
Role of Oxide Layer on Wall Thinning Caused by Liquid Droplet Impingement
Authors: Satou Manabu , Sato Takashi , Hasegawa Akira
Published: July 2010

Adhesion strength of oxide layer formed on carbon steel in air at elevated temperature was evaluated using a laser shock method to reveal the influence of the oxide layer on the wall-thinning behavior caused by liquid droplet impingement. The strength of the interface between magnetite and the carbon steel was comparative to the yield stress of the steel or less. It was suggested that formation of the oxide layer reduce the critical velocity, which might result in exfoliation and wall-thinning, compared to without oxide layer.
Microstructure and Properties of the Composites: Hydroxyapatite With Addition of Zirconium Phase
Authors: Dudek Agata , Tokarz Adam
Published: July 2010

The group of bioceramics include hydroxyapatites, which, due to their specific properties, are widely used in biotechnology. These compounds exist in skeleton of human and animal body. A range of advantages of implants which contain, among other things, hydroxyapatites, results also from the level of their porosity. Recent trends that focus on improvement in poor strength properties of HAp coatings include introduction of solid solution of Y2O3 in ZrO2 [1–7]. It seems to be essential to determine the resulting structural and strength properties in the aspect of further application of composites based on hydroxyapatite with addition of zirconium phase. The investigations involved ceramic composites based on HAp with different amounts of the phase modified with ZrO2 yttrium dioxide.
A Study of Redistribution of Residual Stress and Hardness Due to Welding and Surface-Machining at Girth Welded Joint
Authors: Mochizuki Masahito , Katsuyama Jinya , Ihara Ryohei , Mori Hiroaki , Mikami Yoshiki , Onizawa Kunio
Published: July 2010

Stress corrosion cracking (SCC) near the welded zone of core internals and recirculation piping of Type 316L stainless steel in BWR nuclear power plants has been observed at the surface where tensile residual stress exists due to welding and/or surface-machining. It is well-known that butt-welding of austenitic piping causes the tensile stress in the inner surface of the pipe and that surface-machining is usually conducted before and after piping butt-welding to match the internal diameter (ID) of pipes and to provide a smooth surface finish but some amount of hardening. The SCCs near the welds of Ni-based alloys have been observed in the environment of primary water coolant, which is so called PWSCC. In this case, both residual stress and hardening are also the most important factors induced by welding as well as surface-machining in the regions of interest. In this work, therefore, Vickers hardness and residual stress distributions at work hardened layer such as inner surface of piping butt-weld by surface-machining before and after welding were experimentally evaluated. A simulation using a local micron-scale finite element method (FEM) model has been performed to support the understanding of experimental data by a model which was proposed in previous paper (PVP2006 and 2008 [1, 2]). Redistribution behavior of residual stress by welding after surface-machining will be discussed based on experimental and analytical results with regard to crack growth behavior.
Gaseous Detonation in Piping Systems Partially Filled With Liquid
Authors: Shepherd Joseph E. , Akbar R. , Rodriguez E. A.
Published: July 2010

In this paper, we report the results of our investigation into the transmission of a detonation from a gas-filled section of pipe into a water-filled portion. Experimental studies were performed using a detonation in a H2-N2O mixture within a 2-inch, Schedule 40 pipe. The detonation wave impinges on a vertical column of water just downstream of a 90-degree bend. A shock wave is transmitted into the water-filled section and propagates slower than the sound speed in the water due to the coupling of flexural waves in the pipe with pressure waves in the liquid. Incident, transmitted, and reflected pressures in the gas are monitored, along with hoop and longitudinal strain throughout the pipe length. Results are presented for a both prompt initiation of an ideal (Chapman-Jouguet) detonation and deflagration-to-detonation transition (DDT) occurring just upstream of the gas-liquid interface. The results of the experiments are analyzed using computational modeling and simulation with an Eulerian hydrodynamic code as well as classical wave interaction methods. For a Chapman-Jouguet (CJ) detonation, the reflected and transmitted pressures agree with the classical one-dimensional theory of wave interaction. The values of the peak reflected pressure are close to those that would be obtained considering the water as a perfectly reflecting boundary. The transmitted wave propagates at a speed consistent with the Korteweg speed of classical water hammer theory and little to no attenuation in amplitude over ∼ 1.5 m of travel. In one DDT event, peak pressures up to 11 times the CJ pressure were observed at the end of the water-filled section.
Fatigue Design for Non-Welded Regions According to New European and American Pressure Vessel Standards
Authors: Rauscher Franz
Published: July 2010

EN 13445-3 [1], which was first published in the year 2002, includes separate fatigue design checks for unwelded and welded regions. Furthermore, the new 2007 ASME Boiler & Pressure Vessel Code Section VIII Division 2 [2] includes separated design checks for welded and unwelded regions. Because of differences in the procedures, the approaches of these standards are not directly comparable. Therefore, comparable design curves for special cases and/or for extreme values of parameters are evaluated. Differences in the procedures are discussed and examples are given for special cases. For the unwelded regions, which are covered by this paper, the following approach was chosen: Design curves from EN 13445-3 are corrected by the extreme values of the necessary correction factors. These corrected EN 13445-3 fatigue design curves are compared to the design curves given in ASME VIII-2. As examples of typical usage, some experimental results are compared to the specific design curves.
Effects of Weld Strength Mismatch on Estimation Procedures for J Fracture Parameter Using Clamped SE(T) Specimens
Authors: Donato Gustavo H. B. , Magnabosco Rodrigo , Ruggieri Claudio
Published: July 2010

This work presents an exploratory development of J estimation procedures for deep and shallow cracked tension SE(T) specimens based upon plastic eta factors which incorporate the effects of weld strength mismatch. The considered technique includes estimation of J from plastic work. The primary objective is to derive estimation procedures which are applicable to determine J fracture parameters for a wide range of a/W-ratios, material flow properties and different levels of weld strength mismatch using clamped SE(T) specimens of varying geometries. Very detailed non-linear finite element analyses for plane-strain models provide the evolution of load with increased load-line displacement and crack mouth opening displacement, which are needed to determine the estimation procedures. Laboratory testing of a welded structural steel using SE(T) specimens provide the data needed to evaluate J evolution for the welded joints based upon the proposed methodology. The crack driving force evolution is compared against the results obtained using plastic eta factors for homogeneous specimens and demonstrates the importance of considering mismatch effects on crack-tip stress fields and fracture parameters. The present analyses, when taken together with previous studies, extend the body of results which serve to determine J integral using tension SE(T) specimens with varying geometries and mismatch levels.
The NPP Leibstadt Program for the Prevention of Piping Degradation Due to Flow-Accelerated Corrosion Phenomena
Authors: Zander Andre´ , Janning Carsten
Published: July 2010

Safety-related aspects and the targeted high availability of the power plant as well as the requirements stipulated by Swiss regulatory authorities prompted the operator of NPP Leibstadt (KKL) to introduce a procedure for the early identification of susceptible piping sections and components due to flow-accelerated material degradation mechanism. Flow-accelerated corrosion (FAC) is a degradation process resulting in wall thinning of piping, vessels, heat exchanger and further equipment made of carbon and low alloy steel. The FAC degradation mechanism occurs only locally under specific condition of flow, water chemistry, temperature and materials applied. In order to deal with the flow-accelerated corrosion issue, the NPP Leibstadt (KKL) adopted the computer code COMSY for the preparation of targeted wall thickness inspection programs. In a first step a systematic screening procedure was applied with the intension to reliably identify system areas which may be subject to a flow-accelerated corrosion attack. For system areas sensitive to degradation a detailed lifetime analysis was performed for individual piping elements. Based on the predicted service life, elements were prioritized for inspection programs. The results of examination were fed back to further optimization of the lifetime predictions. Due to systematic approach applied, a significant gain of knowledge be achieved regarding the impact of FAC on a plant-wide basis. The combination of predictions, the measured data and other inspection results (e.g. visual examinations) are used to prepare a catalog of weak points. The weak-point catalog is thus a tool for as-is information and inspection of piping systems / components. It serves to optimize the condition-oriented planning of future measures and inspections and will be revised and updated on an annual basis.
Numerical Analysis of Fluidelastic Instability in a Normal Triangular Tube Array
Authors: Gillen Stephen , Meskell Craig
Published: July 2010

Investigation of steady flow through a normal triangular tube bundle is carried out numerically using a 2D Reynolds Averaged Navier-Stokes solver. Pitch to diameter ratios of 1.25 and 1.32 are simulated with a single tube displaced and the resulting force coefficients measured. Comparison of pressure coefficient with experimental data indicates simulations provide a reliable indication of Reynolds number dependence. These fluid force coefficients are then used as input into the quasi-unsteady model in order to predict the critical velocity of damping controlled fluidelastic instability for a single degree of freedom tube within an array. The predicted critical velocities are in the range of empirical data from the literature. The predicted critical velocities for the pitch ratio of 1.25 are within 30% of the experimental values previously reported.
Residual Stress and Strain Responses of Welded Piping Joints Under Low-Cycle Fatigue Loading
Authors: Cheng Pei-Yuan , Hassan Tasnim
Published: July 2010

It is well known that residual stress of welded joints influence their fatigue lives. This influence of residual stress is manifested through strain ratcheting response at the weld toe. Among many other reasons, strain ratcheting at the weld toe is anticipated to be a reason of many premature fatigue failure of welded joints. Hence, accurate simulations of weld toe residual stress and strain responses are essential for fatigue life simulation of welded joints. This paper presents results form an ongoing study on fatigue failure of welded piping joints. A modeling scheme for simulating weld toe residual stress and strain response is developed. Uncoupled, thermo-mechanical, finite element analyses are employed for imitating the welding procedure, and thereby simulating the temperature history during welding and initial residual stresses. Simulated residual stresses are validated by comparing against the measured residual stresses. Finite element simulations indicate that both residual stress and resulting strain responses near the weld toe are the key factors in inducing fatigue cracks at the weld toe. Research needs in revealing the fatigue failure mechanisms at the weld toe are discussed.
High Speed Imaging of the Fragmentation of the Jules Verne Automated Transfer Vehicle
Authors: Giannopapa C. G. , Hatton J. , Franken E. , van der Linden B. , Jenniskens P.
Published: July 2010

The Automated Transfer Vehicle (ATV) “Jules Verne” is the first completely automated rendezvous and docking spaceship to service to the International Space Station (ISS). As a cargo ship, it is designed for one-time use. After completing its mission, it is subjected to hypersonic flow during the re-entry into earth’s atmosphere, with high associated heat flux leading to structural heating and fragmentation of the vehicle. During its first voyage on September 29, 2008, the ATV reentry was observed using various instruments including a wide field view camera and high frame rate cameras. Using the wide field view camera the trajectory path can be reconstructed. The high frame rate camera gives information about the sequence of the events of the explosions and fragmentations of various parts of the spacecraft. The aim of this paper is to present the detailed events that occurred during the ATV re-entry.
Evaluation of Improved Methods for Plant Data Validation in Automated Fatigue Monitoring
Authors: Cranford Elwyn Lyles , Gray Mark A. , Shychuck Jamie L. , Haegeli Heinz , Blokker Brigitte
Published: July 2010

This paper presents the results of an engineering review that examined the accuracy and effectiveness of specific enhancements to an automated data validation algorithm used as part of an on-line fatigue monitoring system. One of the major challenges in developing an effective fatigue monitoring system that processes plant computer data is the quality of the original data stream. In these systems, the goal is to minimize, and eventually eliminate, spurious conservative fatigue monitoring results caused by bad input data passed through the plant computer. Reaching this goal frees engineering users from having to correct the faulty data in the original input stream and reprocess it. The WESTEMS™ stress and fatigue monitoring program at the Beznau Nuclear Power Plant Units 1 and 2 was used to develop and test the enhancements to the data validation algorithm designed to reach this goal. The engineering review included both quantitative and qualitative assessments of data-related errors and warnings, as well as a detailed comparison of the automated data validation and correction algorithm against a parallel user-assisted (manual) process. Effectiveness of the method was quantified by comparing the overall fatigue accumulation rates resulting from the manual data checking process with those produced by the fully automated approach. The positive results of the review demonstrate the effectiveness of the enhanced automated approach presented.
Fatigue Analysis Methods: Their Performance Evaluation for a Class of Pressure Vessels With Welded Joints
Authors: Kalnins Arturs
Published: July 2010

This paper provides a basis for evaluating the performance of a fatigue analysis method for a selected class of welded pressure vessels. After the allowable number of cycles that the method permits for a member of the class is calculated, the question is addressed whether that number of cycles can be regarded as conservative or unconservative. To answer that question, a performance evaluation is proposed that requires a mean life estimate of a representative sample of the selected vessel class from tests, and the predicted mean life and the permissible number of cycles from the method. The performance is based on the ratio of two factors: (1) Achieved Factor — test mean life cycles divided by the permissible number of cycles, and (2) Assigned Factor — predicted mean life cycles divided by the permissible number of cycles. The ratio between the former and the latter defines a Performance Index, which indicates whether, and to what extent, the permissible number of cycles can be regarded conservative or unconservative. For an illustration of the performance evaluation, it is applied to three methods for a class of pressure-cycled carbon steel vessels with welded-on flat plates.
Design Review of the VVER-440 NPP Main Components on the Base of ASME BPVC
Authors: Boros Ja´nos , Pa´lfi Tama´s , Pa´lfi Pe´ter , Ra´tkai Sa´ndor
Published: July 2010

Complying to the regulatory body’s need complete design review was made for the Hungarian VVER 440/213 units’ main components. It was necessary, because only the most important components had design calculation for 30 years of operation — in this case the task was to make new calculation including the key-points from the original and justify 50 years operation —, while some of the components had no or poorly documented design calculations. According to these facts documentation needed to be completed for some components, TLAA had to be made for 50 years, and the NPP decided to have ASME code as the basic of the general standard in the future. For these three reasons Paks Nuclear Power Plant decided to make a complete design review for all class1 and class2 components on the base of ASME BPVC code. Article shows the major problems and the possible solutions while moving from PNAE [2] regulation to ASME code.
Assessment and Management of Ageing of Civil Structures of Paks NPP
Authors: Katona Tama´s , Ra´tkai Sa´ndor , Go˝si Pe´ter , Mo´ga Istva´n
Published: July 2010

Ageing management review is an essential element of the licence renewal process. Proper ageing management has to ensure that ageing effects will be discovered and handled before the loss of the intended functions of the structures. This practice, the most important and the most frequent degradation mechanisms and effects with the involved concrete structures and structural elements, are presented and summarised in this paper. Two types of ageing management programmes are applied at Paks NPP. Programmes “A” are related to the different structural elements of the buildings or to typical ageing problems (e.g., settlement) which occur at many buildings. Programmes “B” specify the exact methods and conditions of the application of the necessary “A” programmes for the different buildings. Altogether 31 buildings are involved in the ageing management system of Paks NPP. The majority of the identified degradation problems were comparatively minor and involved mainly concrete cracking, leaching, chemical attack, corrosion of carbon steel liners, degradation of sealing and coating materials, and settlement. The main results of monitoring and theoretical analyses (in the fields of heavy-concrete structures, effect of elevated temperature, forecasting of settlement for the end of the extended lifetime, etc.) are also presented.
Method for Predicting Mixing Tee Thermal Fatigue in Carbon Steel Based on Austenitic Stainless Steel Operating Experience
Authors: McGill Robert O. , Harris David O. , Wolfe Ken
Published: July 2010

Over the past ten years, a significant amount of research has been conducted regarding mixing tee thermal fatigue in pressurized water reactors prompted by the leakage event at Civaux Unit 1 in 1998. The plant experienced a leak in the reactor residual heat removal system piping after a short period of operation during plant start-up. An evaluation as to the cause of the leakage concluded that mixing of hot and cold fluid upstream from the failed austenitic stainless steel elbow resulted in thermal fatigue cracking. Recently, an assessment of susceptibility to this thermal fatigue mechanism in boiling water reactors in the United States was completed. The piping systems in these reactors where the potential for thermal mixing exists are predominantly constructed of carbon steel. Thus, an analytical model was developed for predicting mixing tee thermal fatigue in carbon steel piping based on the austenitic stainless steel piping operating experience at Civaux. This paper describes how the model was developed and presents some general findings.
New PLIM Program for Czech NPPs
Authors: Kadecˇka Petr
Published: July 2010

Nuclear Research Institute (NRI) Rez, Czech Republic have worked together with Czech NPPs (Dukovany and Temelin) on preparation of a new Plant Life Management (PLIM) Program that is currently for these NPPs in implementation phase. This presentation describes the new PLIM program structure and whole implementation process that covers: - preparation of specific guidelines and strategies based on analysis of Czech Regulator’s and IAEA requirements, and different good practices, - ageing management (AM) review carried out for selected structures and components, existing AM programs and other already used practices related to AM, - performance of technical-economical study that adds economical planning to PLIM, - design and usage of supporting database application called INFOZ.
Study of Fluid Effects on Dynamics of Composite Structures
Authors: Kwon Y. W.
Published: July 2010

This study investigates the effect of fluid-structure interaction on dynamic responses of submerged composite structures subjected to a mechanical loading. The research focuses on finding various parameters that affect the transient dynamic responses of these structures. Coupled fluid-structure interaction analyses of composite structures surrounded by a water medium are conducted numerically for various parametric studies, and their results are compared to those of dry structures. Furthermore, modified dry structural models are developed to represent the dynamic responses of the same structures under water with a reasonable accuracy. Those models promise to be beneficial to predict structural behaviors under water without an expensive computational or experimental cost.
Growth Behavior of Two Interacting Surface Cracks of Dissimilar Size
Authors: Kamaya Masayuki , Kikuchi Masanori , Miyokawa Eiichi
Published: July 2010

When multiple cracks approach to each other, the stress intensity factor is likely to change due to the interaction of the stress field. This causes change in the growth rate and the shape of cracks. Because of the orientation with respect to the loading, and existing of KII and KIII which can develop and increase with interaction, the shape of cracks becomes non-planar. In this study, the complex growth of interacting cracks is evaluated by using the S-Version finite element method, in which local detailed finite element mesh (local mesh) is superposed on coarse finite element model (global mesh) representing the global structure. The effect of relative size and spacing of cracks on the growth behavior is investigated. It is shown that the smallest crack stops growing due to the interaction when the difference in size of two cracks is large enough.
Effect of Heat-Up Transient Condition on the Thermal Stratification in Nuclear Power Plant Surgeline
Authors: Kim Young-Jong , Kim Maan-Won , Ko Eunmi , Lee Jae-Gon , Kim Byoung Chul
Published: July 2010

During operating transients of the pressurizer, thermal stratification effect may occur especially in the horizontal parts of surge line. Generally, the fatigue usage factor of surge line is comparative high, due to its operating temperature and pressure transients and its thermal stratification loads. Traditional 2-D finite element model (FEM) for thermal stratification analysis has excessive conservativeness. To reduce such an excessive conservativeness, 3-D numerical analysis model for fluid-structure interaction (FSI) problem in the surgeline and some parametric FSI analyses were performed with different heat-up temperature rate and flow rate in the inlet of surgeline during plant heat-up. Based on these FSI analysis results, an efficient condition to reduce the excessive conservativeness in surgeline stratification analysis could be proposed in terms of heat-up rate and flow rate.
Investigation of Corrosion Properties of Welded and Laser-Surface Melted SUS 304 in Nuclear Power Operating Conditions
Authors: Kim Joung Soo , Chung Chin-Man , Baik Sung-Hoon , Lee Sang-Bae
Published: July 2010

Welded SUS 304 stainless steel surface was melted using an Nd:YAG laser beam in order to increase its corrosion resistance in operating conditions of nuclear power plants. The optimum process conditions for laser-surface melting of welded SUS 304 stainless steel were determined by measuring the depth melted by the laser beam of welded regions through an optical microscope, observing the microstructures of the laser-melted surface, and measuring the double-loop electrochemical potentio-dynamic reactivation (DL-EPR) curves in a 1L aqueous solution of 0.5M H2SO4 and 0.01M KSCN. From the test results, the optimum laser-surface melting process conditions were as follows; a laser power of 170W, a N2 gas flow rate of 20L/min, a beam scan rate of 600mm/min, and laser power density of 20J/mm2. The microstructure of the laser-surface melted (LSM) region was observed to be very fine and homogenous, and of cellular structure. Grain growth in the LSM region from the substrate occurred epitaxially. No Cr depletion along the grain boundary in the LSM region was detected, which would result in increasing the corrosion, specially intergranular corrosion (IGC) including intergranular stress corrosion resistance (IGSCC) of the welded SUS 304.