bluuebunny/crossref_metadata_2025 huggingface dataset:
Impact Simulation of Radioactive Material Package During Forklift Truck Collision
Authors: Wu Tsu-te
Published: August 2008

This paper discusses the evaluation of the structural integrity of the SAFKEG radioactive material package to ensure hazardous material confinement during the postulated accident event of forklift truck collision. When a SAFKEG Package carried by a forklift truck traveling at 7 miles per hour collides with another forklift truck moving at the same speed but in the opposite direction, the structural response of the package components represents a complex problem. Because of its complex geometric configuration and complicated contact conditions between the neighboring component interfaces, the problem can not be solved using the implicit numerical scheme that would involve solving a large number of simultaneous equations through numerical iteration. In addition, material degradation and failure caused by collision can create severe convergence difficulties in the implicit analysis. Consequently, the explicit solution method is used in the present analysis, and thus the problem has to be treated as a dynamic one even though the inertia effect is insignificant due to the low speed of the forklift trucks. Applying the explicit dynamic technique to quasi-static problems involving very large deformation and material degradation require special considerations in overcoming solution convergence and extremely long computing time. The techniques used to overcome these difficulties are discussed in this paper. This paper also discusses the development of the constitutive models of the thermal insulating and shock absorbing materials used in the SAFKEG. The resin-bounded cork material is represented by the “crushable foam” plasticity with volumetric hardening. On the other hand, the material model of the brittle foam is developed by using the combination of the Mohr-Coulomb and Drucker-Prager plasticity theories. The analysis utilizes the finite-element method and the ABAQUS/Explicit Computer Code, version 6.3. A combination of the “General Contact” method and the “Contact Pair” method is employed to simulate the complicated interface variations among the neighboring components of the model.
A Novel Method of Estimating the Aspect Ratio of Pipe Wall Thickness to Diameter Utilizing the Characteristics of a Hollow Cylindrical Guided Wave
Authors: Nishino Hideo , Chubachi Noriyoshi , Cho Hideo , Takemoto Mikio
Published: August 2008

We have developed a method of estimating the aspect ratio of a pipe wall thickness to diameter (t/d) using a hollow cylindrical guided wave (HCGW). The HCGW is an ultrasonic guided wave in a pipe. The method is very useful for onsite and nondestructive estimation of pipe wall thickness. It is based on the change of the dispersion relation of the HCGW as a function of t/d. The group velocity of the primary wave (first arriving wave packet from an impulse source) of the HCGW ranges from the bar velocity to the sheet velocity as a function of t/d. The bar velocity is the velocity of the DC component of the guided wave propagating in a solid cylinder; the sheet velocity is that of the S0 mode Lamb wave. The first part of the paper describes the principle of the method. In the last part, a laser ultrasonic method was employed to verify the method in both time- and time-frequency domains. The experimental results for aluminum pipes with various t/d’s were in good agreement with the theory.
Time Frequency Domain Analysis of the Dispersion of Guided Wave Modes
Authors: Cho Youn-Ho , Kim Yong-Kwon , Park Ik-Keun
Published: August 2008

One of unique characteristics of guided waves is a dispersive behavior that guided wave velocity changes with an excitation frequency and mode. In practical applications of guided wave techniques, it is very important to identify propagating modes in a time-domain waveform for determination of defect location and size. Mode identification can be done by measurement of group velocity in a time-domain waveform. Thus, it is preferred to generate a single or less dispersive mode. But, in many cases, it is difficult to distinguish a mode clearly in a time-domain waveform because of superposition of multi modes and mode conversion phenomena. Time-frequency analysis is used as efficient methods to identify modes by presenting wave energy distribution in a time-frequency. In this study, experimental guided wave mode identification is carried out in a steel plate using time-frequency analysis methods such as wavelet transform. The results are compared with theoretically calculated group velocity dispersion curves. The results are in good agreement with analytical predictions and show the effectiveness of using the wavelet transform method to identify and measure the amplitudes of individual guided wave modes.
Circumferential Guided Wave Inspection for a Defect at Inner Surface of a Pipe
Authors: Hayashi Takahiro , Nagamizo Hisashi , Nakamura Shinya , Murase Morimasa , Kawashima Koichiro
Published: August 2008

Circumferential guided wave, that is ultrasonic wave propagating in the circumferential direction in a pipe, has attracted considerable attention due to its prominent characteristics. However, its complex wave mechanics such as multi-mode generation and mode conversion often prevent us from quantitative evaluation such as defect sizing. In this study, modal analysis and guided wave simulation are done by a semi-analytical finite element technique to clarify that a defect at an inner surface of a pipe cannot be quantitatively measured by the amplitude of guided wave signals. Energy distributions in the thickness direction that shows the sensitivity to the defect depth are calculated for various guided wave modes. These calculation results and experimental group velocity dispersion curves show that the conventional angle beam transducers do not excite the mode with inner concentrated energy and so inner defects cannot be measured well by the amplitude of received signals, which was improved with the special angle beam transducers.
Automated Ultrasonic Inspection of Pressure Vessel Welds
Authors: Moles Michael , Labbe´ Simon
Published: August 2008

ASME Code Case 2235 now permits automated ultrasonic testing (AUT) instead of radiography for vessels 0.5” (12.7 mm) or greater. Ultrasonic testing has significant advantages over radiography: no safety hazard so no disruption of production; inspection as soon as component cools; rapid feedback; defect vertical sizing for Fitness-For-Purpose applications; tailored inspections. ASME CC 2235 permits a variety of inspection techniques based on pulse-echo and Time-Of-Flight Diffraction (TOFD), provided a Performance Demonstration is achieved. This paper describes a number of AUT systems which fulfill the ASME code case. These AUT systems range from a portable phased array system (Omniscan) for low cost and convenience, through conventional systems based on TOFD (μ-Tomoscan), general phased array systems (Tomoscan III) to premium systems with multiple NDE approaches. With such a variety of technologies and costs, AUT systems can be tailored to the client’s needs.
High S/N Ratio Guided Wave Inspection of Pipe Using Chirp Pulse Compression
Authors: Toiyama Kiyokazu , Tsutsumoto Takahiro , Ikeda Takashi , Hayashi Takahiro
Published: August 2008

Guided wave is expected as the most promising technique for rapid long-range inspection of pipes. However, signal to noise ratio is still required to be improved, especially in highly attenuative pipes covered with heat insulator and/or buried in the ground. Recently, pulse compression technique has been developed as an effective means for improving S/N ratio in the field of radar detection. In this paper, chirp pulse compression technique was applied to the long-range inspection of pipe using guided wave. The technical brief explanation about chirp pulse compression was described. Example data signals of burst wave excitation way and chirp pulse excitation way with commonly -used amplifier were reviewed with respect to unwanted side lobe. The cause of a side lobe was investigated, and the amplifier with excellent distortion property was presented to improve S/N ratio of system with quite vanishing of side lobe.
Evaluation of the Rolling Direction Effect in the Acoustoelastic Properties for API 5L X70 Steel Used in Pipelines
Authors: Santos Auteliano A. , Bray Don E. , Caetano Sidney F. , Andrino Marcilio Haddad , Trevisan Roseana E.
Published: August 2008

Ultrasonic evaluation of stresses has experienced great development in the last decade, mostly because of the new electronic instruments and high-speed data acquisition systems now available. Past applications have been applied mostly using shear waves and the birefringence technique. Longitudinal critically refracted (skimming) waves have proved to be more sensitive to stress variation, and have been applied recently to oil steel pipelines. Oil pipe failures have caused a lot of environmental damage in Brazil. The environmental and economical costs are very high. This work describes part of a research effort to further apply longitudinal critically refracted waves to inspect the welded region in pipes in Brazil through a study of the acoustoelastic constants. Twenty-eight samples were cut from a flat plate of the oil industry class steel (API 5L X70) which would be typically formed into pipe. The samples were prepared for tensile testing. Half of those were cut from what would be the longitudinal direction of the pipe, and the other half from the perpendicular direction. The samples are bars of 760×70×10.8-mm3. Some bars were stress relieved before the test. The results show that there are significant differences between the acoustoelastic constants for the rolling direction and the perpendicular direction. It is clearly important to have the correct value for the acoustoelastic coefficient when applying the technique to stress measurement. There is a minor, but important influence of the stress relief process.
Development of a Focused Ultrasonic Transducer for the Testing of the Wheel Seat in the Hollow Axle of Shinkansen Vehicles
Authors: Murata Yorinobu , Toda Hiroki , Ikeda Masataka , Nii Yoshiyuki , Yohso Jiro
Published: August 2008

In order to test the fretting fatigue cracks with high sensitivity, which occurred on the wheel seat of hollow axles of Shinkansen vehicles, the design of a focused ultrasonic transducer was proposed by a new method. The method was achieved by designing a suitable surface shape of the ultrasonic transducer through a reverse analysis of the wave propagation in the axle so that all radiated waves from the transducer were focused into a point region of the wheel seat with a same phase. A composite piezoelectric material was applied to the focused ultrasonic transducers in order to test with a shorter ultrasonic pulse. As the result of evaluating the performance of the developed focused ultrasound transducer, comparing with the previous plate-like ultrasonic transducer made using PZT, a great improvement was demonstrated in respect of sensitivity and directivity. Furthermore, the method inclining the ultrasonic beam slightly to the circumference direction and the method making the frequency characteristic of the transducer high were devised in order to reduce the influence of echoes by press fit. Consequently, it was demonstrated that a focused incline ultrasonic transducer of 10 MHz was possible to evaluate up to an artificial crack of about 0.17 mm depth with the SN ratio of 9 dB.
Non-Contact Tube Inspection Technique Using Laser Generation of Guided Wave and Its Reception by Air-Coupled Transducer
Authors: Jhang Kyung-Young , Kim Hyun-Mook , Kim Hong-Joon , Ha Yob
Published: August 2008

Ultrasonic guided wave has been widely used for the tube inspection. The conventional method is to use piezoelectric transducers that should be contacted to the target surface. In recent years, however, the non-contact method is strongly required in the automation of inspection process for the manufacturers as well as in dangerous environmental in-service inspection. In this paper, we have proposed a non-contact inspection method generating the ultrasonic guided wave by laser and receiving it by an air-coupled transducer. This method can generate and receive the guided wave of a specific mode with selectivity, which makes the interpretation of received signal clearer and resultantly improves the accuracy of inspection. Also the detected signal was analyzed by using the wavelet transform and it was shown that the wavelet analysis is useful for the mode identification. The proposed method was applied to the tube of 1mm thickness and 20mm outer diameter with three different types of artificial notch defects; through-wall, inside and outside of tube. The size of defects were 2∼8mm long in the circumferential direction, with 100μm width. It was proven that all kinds of defects were detectable. Finally we have developed a practical automatic inspection system, in which the inspection result is displayed in a 2-D image.
Determination of Compressive Residual Stresses Using Critically Refracted Longitudinal (Lcr) Waves
Authors: Belahcene Farid , Lu Jian , Thomas Fabien , Zhou Xiaolai
Published: August 2008

Surface treatment methods are widely used in the aerospace industry to increase the metal parts damage tolerance by producing a thin surface layer of compressive residual stresses that prevents crack initiation and retards crack growth during service. Nondestructive evaluation of the prevailing compressive residual stresses in the shallow subsurface layer is realized by the ultrasonic technique. The method is based on the measurement of ultrasonic wave velocity variation versus the stress state variation. The application of the Lcr technique (using longitudinal critically refracted wave) has been performed on the SMAT (surface mechanical attrition treatment) steel sample, for which the residual stresses are determined in different zones and depths. The results show that the ultrasonic technique is rather efficient for the evaluation of residual stresses and control of the state of the material after mechanical treatment. The experimental results are successfully compared with the hole drilling method.
Digital Image Acquisition Method for Film Based Radiographic Testing
Authors: Mori Masako , Taguchi Tetsuo , Takagi Mikio , Aoki Yoshimitsu
Published: August 2008

Radiographic Test (RT) has been widely used in various industries to detect inner defects of weld structures and other significant components. In terms of digitization, although the ASME Boiler and Pressure Vessel Code Section V provides general outlines of digital image acquisition and processing of RT film, it is not widely implemented in industries as medical radiography instruments. One major reason for not being able to drive RT film digitization is that they cannot quantitatively guarantee each RT film and its digital image resolution directly. To solve these bottlenecks, the present paper proposes two things: 1) Line pair type penetrameter corresponding to current image quality indicators (IQIs) for both hole and wire type, which enables us to not only easily guarantee radiographic testing film resolution but also quantify digitalized RT film image resolution [1]; and 2) Line pair type standard film which is used for digitizing “existing RT film” with commonly used imaging scanners. Prototypes of line pair type penetrameters have been developed and prepared for various materials and verified for its applicability to RT digitalization. Also, prototypes of standard film are manufactured and verified that used with scanners, we can get RT film images of which resolution are quantitatively guaranteed. These two new RT film digitizing methodologies enable us to get “resolution guaranteed film images” and “digital inspection.” Furthermore, this will contribute to “remote inspection” where manufacturers, inspectors, customers and government inspectors can share the results of inspection in electronic format and timely confirm them from a remote place.
Image Subtraction Method in Digital Radiography of Welding
Authors: Ikeda Yasushi , Mizuta Yasutoshi
Published: August 2008

In order to improve contrast resolution in X-ray digital radiography, an image subtraction method was developed. Using a conventional image intensifier, welding lines of thick steel parts were tested. First the X-ray image was integrated in the image flame of an image processor used to minimize the random noise from X-ray statistic distribution. Next the image detector was slightly moved and again the X-ray image was taken, where the second image was subtracted from the first integrated image, which gave us significantly spatial noise reduction and extracting the images of only defects of welding. The contrast enhancement was possible to maximum level, so that the detectability of defects was greatly improved, being about 0.1% of detectability was obtained.
Crack Sizing of Deep Cracks in Eddy Current Testing Using 3D Electromagnetic Field Analysis
Authors: Takagi Toshiyuki , Uchimoto Tetsuya , Endo Hisashi
Published: August 2008

A computer-aided approach of the eddy current testing (ECT) is described to detect and to size up deep cracks in thick metal structures. A 3D eddy current field analysis based on the finite elements performs designing ECT probes and evaluating the size of crack depth quantitatively. An exhaustive study on the ECT probe specification gives the optimal design of coil elements and their combination. The experimental verification shows that the developed ECT probe employing double exciting coils is capable of detecting crack depth over 10mm from the inspection surfaces. The depth of cracks is quantitatively evaluated from the measured ECT signals with the help of numerical calculation. The results of evaluation profile the crack shapes with fairly high accuracy, supporting our approach.
Finite Element Simulations of the Remote Field Eddy Current Signal in Steam Generator Tubes of Monju Fast Breeder Reactor
Authors: Mihalache Ovidiu , Imai Yoshiyuki , Ueda Masashi , Yamashita Takuya
Published: August 2008

The present paper describes and clarifies the main difficulties arising in the 3D numerical simulations using finite element method of the remote field eddy current effect in magnetic steam generator tubes. The 2D axisymmetric and full 3D simulations are compared with experimental results from outer discontinuities in Monju fast breeder reactor steam generator tubes. Very good agreements were obtained between measurements and 2D simulations. The influences of several parameters are evaluated by 3D simulations: convergence error of the iterative matrix solutions, pattern of the mesh discretization, the boundary limit and finite element interpolation order. The computational cost of the remote field 3D model in Monju steam generator tubes and the numerical aspects of the 3D simulations are discussed in detail in the paper.
Leak Detection of the Pipeline Using Acoustic Emission Technique
Authors: Lee Min-Rae , Lee Joon-Hyun
Published: August 2008

This paper presents an approach to leak detection of pipeline review in term of theoretical analysis such as acoustics and hydromechanics that should be accompanied by explanation of leakage. The acoustic emission signals during leak from a circular hole of different geometries were studied both analytically and experimentally. The relationships between acoustic parameters and fluid mechanical parameters also were derived analytically. A quadrupole aerodynamic model was applied in the analysis of leak form the circular hole. Computer simulation results demonstrate the effectiveness of the proposed approach. In addition, the leak source location results are also presented by employing the wavelet transform.
Some Consequences of Material Frame Indifference on Engineering Flow Calculations
Authors: Mompean G. , Thais L. , Helin L.
Published: August 2008

The principle of material frame indifference (MFI) is a fundamental and controversial principle of continuum mechanics which has been invoked to derive recent nonlinear algebraic models for stresses of viscoelastic liquids (Mompean, Thompson, and Souza Mendes [2003]) and for Newtonian turbulent fluids (Rumsey, Gatski, and Morrison [2000]). The purpose of the present study is to identify regions of a flow field where MFI should be considered. Such regions are identified by computing the angular velocity of the principal directions of the rate-of-deformation tensor in order to obtain a Euclidean objective vorticity tensor. The method is applied to the planar flow through an abrupt 4:1 contraction. The main results are: (i) MFI should be taken into account in regions characterized by the transition between two different viscometric kinematics and significant velocities (ii) MFI can be safely ignored in regions of pure viscometric behavior as well as in recirculation regions.
A Model to Predict Stratification in Two Phase Flow in Horizontal Pipes
Authors: Calay Rajnish K. , Awad Ahmad
Published: August 2008

Stratified flow is encountered in many situations. The flow of hydrocarbons transported in horizontal pipes often gets stratified. The prediction of pressure drop and liquid hold-up is essential for reservoir and pipe management and optimizing the cost of transportation of constituents. The present paper presents a simple mathematical model to predict the pressure drop, water and oil hold up and stratified layer. A good agreement with the experimental data was found. The model will be further developed and incorporated within a numerical model in order to investigate the flow field characteristics and establish correlations for a wide range of parameters.
Seal Monitoring System for an Explosive Containment Vessel
Authors: Pastrnak John W.
Published: August 2008

Researchers at Lawrence Livermore National Laboratory are developing a high performance filament wound composite firing vessel intended for containment of one time detonation of explosive assemblies that contain toxic metals and gaseous by-products. A 2-meter diameter pressure vessel is being designed for containment of up to 80 lb tnt equivalent explosive without leakage. Due to the complexity of assuring good o-ring sealing ability for explosive generated dynamic pressures in excess of 40,000 psig (280 MPa), multiple seals in-series are used at the vessel openings. To assess and monitor the integrity of these seals during actual detonations within the vessel; miniature pressure and gas sample measurements were made upon the interstitial volume between the o-ring seals. Recent results of this prototype monitoring system indicated that at least two of the seven o-ring seals were required to adequately prevent transient leakage of toxic particulates from test series CVD-2a as evidenced by mass spectrograph quantities of 10% argon vessel pre-charge as a fiducial indicator gas and later confirmed by particulate swipes for metals.
Helium Leak Testing Between E-11 and E-15 CC/S: Theory and Application
Authors: Saski Y. Tito
Published: August 2008

Gas leakage between E-11 and E-15 std cc He/s can be measured by a helium accumulation method. The leak detector uses a quadrupole mass spectrometer with a minimum detectable partial pressure of 5E-15 torr. The mass spectrometer is attached to a small ultrahigh vacuum chamber constructed of stainless steel treated for a low hydrogen outgas rate of 2E-15 torr·liter/cm2·s. The chamber has a nozzle to which a test object can be attached. The chamber is also equipped with a non-evaporable getter (NEG) pump that pumps active gases but not noble gases such as helium. The purpose of the NEG and the ultra-low hydrogen outgas feature of the chamber is to maintain low background pressure and high sensitivity of the quadrupole during helium accumulation. Helium tracer gas coming through a defective seal or material is accumulated in this chamber for a few minutes, and the rate of rise of the helium signal is compared with that of a calibrated reference leak. In this manner, leakage down to 1E-15 std cc He/s can be measured with a good confidence factor.
Numerical Simulation of Bird Strike Damage on Jet Engine Fan Blade
Authors: Shimamura Kazuo , Shibue Tadashi , Grosch Donald J.
Published: August 2008

Aircraft jet engine should be designed to keep the required performance against for the event of foreign object ingestion, such as bird-strike. For the purpose to realize highly efficient and more advanced design of fan blade of jet engine, a numerical simulation technique for bird-strike problem has developed. Good agreement was obtained between simulation results and the soft body impact tests described in this paper. It was also shown that bird-strike problem has to be recognized as a fluid-structure interaction problem, because the impacted bird behaves like fluid and the impact force is highly influenced by the deformation of fan blade.
Study on Simplified Models for Coupled Transmission Tower-Line System to Seismic Excitations
Authors: Li Hong-Nan , Shi Wen-Long , Wang Guo-Xin
Published: August 2008

The simplified computational models of high-voltage transmission tower-line system under out-of-plane and in-plane vibrations are presented due to seismic excitations in this paper. The equations of motion are derived and the computer program is compiled to obtain the earthquake responses of the coupled system. To verify the rationality of the proposed approaches, the shaking-table experiments of the coupled system of transmission lines and their supporting towers are carried out and the results indicate that the errors of theoretical and testing results of systemic seismic responses are within the acceptable arrange in engineering area. Based on these studies, a simplified analysis method is proposed to make the seismic response calculation of coupled tower-conductor system faster and more effective.
Exact Solution of the Base-Isolated Structure With Elastomeric-Type Base Isolator
Authors: Tsai C. S. , Chiang Tsu-Cheng , Chen Bo-Jen
Published: August 2008

Base isolation technologies have been proven to be very efficient in protecting structures from seismic hazards during experimental and theoretical studies. In recent years, there have been more and more engineering applications using base isolators to upgrade the seismic resistibility of structures. Optimum design of the base isolator can lessen the undesirable seismic hazard with the most efficiency. Hence, tracing the nonlinear behavior of the base isolator with good accuracy is important in the engineering profession. In order to predict the nonlinear behavior of base isolated structures precisely, hundreds even thousands of degrees-of-freedom and iterative algorithm are required for nonlinear time history analysis. In view of this, a simple and feasible exact formulation without any iteration has been proposed in this study to calculate the seismic responses of structures with base isolators. Comparison between the experimental results from shaking table tests conducted at National Center for Research on Earthquake Engineering in Taiwan and the analytical results show that the proposed method can accurately simulate the seismic behavior of base isolated structures with elastomeric bearings. Hence, the proposed concept can be used as a reliable tool for engineering professions for preliminary design.
Effects of Coincident Response of Structures Subjected to Horizontal and Vertical Ground Motions on Evaluation of Peak Response
Authors: Taniguchi Tomoyo , Takeshita Mitsuru
Published: August 2008

A response spectrum rule, which considers the coincidence between horizontal and vertical responses, for dynamic analysis of structures subjected to horizontal and vertical ground motions is developed. The ratio of response coincidence, the vertical response to its absolute maximum at the maximum horizontal response, is introduced to express the intensity and direction of the coincident vertical response. It forms a certain normal distribution and is independent of types of earthquake, soil, structure and linearity/non-linearity of structural response. The combination of the maximum expected value of the ratio based on the allowable probability of exceedance and the modal responses gives the maximum expected coincident vertical response at the maximum horizontal response. Comparison of the combined response by the proposed method with the conventional methods highlights the conservativeness of conventional methods in evaluating the vertical response 38% and the combined response 7%.
Accuracy of Shock Response in Time History Analysis
Authors: Chang Shuenn-Yih
Published: August 2008

A very small time step may be needed in the solution of the shock response from an impulse. In fact, this time step might be much smaller than the time step to have accurate representation of the impulse and negligible period distortion. It will be proved that the discontinuity in external force at the end of an impulse is responsible for this difficulty. Furthermore, the technique to assess a relative amplitude error arising from this discontinuity is also proposed. Finally, the rough guidelines to have accurate shock response from an impulse are developed.
Recent Developments in the Seismic Analysis of Multiply Supported Piping Systems
Authors: Gupta Abhinav
Published: August 2008

This paper presents results from some of the recent studies on seismic analysis of multiply supported piping systems. The seismic responses for an actual feedwater piping system as evaluated from the conventional uncoupled analysis are compared with those obtained from an analysis of the coupled building-piping system. A discussion is also presented on the significance of non-classical damping in such analyses. It is illustrated that the composite modal damping is just another form of classical damping. Consideration of composite modal damping in a coupled analysis can give inaccurate piping responses when the modes of uncoupled systems are nearly tuned. In such systems, the effect of nonclassical damping is quite significant. Since the floor spectra are neither generated nor required in a coupled systems analysis, methods like peak broadening or peak shifting cannot be used directly to account for the effect of uncertainties. Formulations are presented to evaluate the design response from a coupled system analysis by considering the effect of uncertainties in modal properties of uncoupled systems.
An Assessment of Simplified vs. Detailed Methodologies for SSI Analyses of Deeply Embedded Structures
Authors: Xu J. , Miller C. , Hofmayer C. , Graves H.
Published: August 2008

Sponsored by the US Nuclear Regulatory Commission (NRC), Brookhaven National Laboratory (BNL) is carrying out a research program to develop a technical basis to support the safety evaluation of deeply embedded and/or buried (DEB) structures as proposed for advanced reactor designs. In this program, the methods and computer programs established for the assessment of soil-structure interaction (SSI) effects for the current generation of light water reactors are evaluated to determine their applicability and adequacy in capturing the seismic behavior of DEB structures. This paper presents an assessment of the simplified vs. detailed methodologies for seismic analyses of DEB structures. In this assessment, a lump-mass beam model is used for the simplified approach and a finite element representation is employed for the detailed method. A typical containment structure embedded in a soil profile representative of a typical nuclear power plant site was utilized, considering various embedment depths from shallow to full burial. BNL used the CARES program for the simplified model and the SASSI2000 program for the detailed analyses. The calculated response spectra at the key locations of the DEB structure are used for the performance assessment of the applied methods for different depths of burial. Included in the paper are: 1) the description of both the simplified and detailed models for the SSI analyses of the DEB structure, 2) the comparison of the analysis results for the different depths of burial between the two methods, and 3) the performance assessment of the analysis methodologies for SSI analyses of DEB structures. The resulting assessment from this study has indicated that simplified methods may be capable of capturing the seismic response for much deeper embedded structures than would be normally allowed by the standard practice.
Dynamic Instability of a Cylindrical Shell Structure Subjected to Horizontal and Vertical Excitations Simultaneously
Authors: Fujita Katsuhisa , Nosaka Taisuke , Ito Tomohiro
Published: August 2008

Many structures such as support columns such as those for elevated expressways and towers tend to become larger and more flexible recently, thus the buckling or collapse of these structures is considered to easily occur than ever due to huge earthquakes. Actually, in the Hyogo-ken Nambu earthquake in Japan, buckling phenomena of tall support columns were observed every-where. Therefore, the evaluation technology on the dynamic stability is very important in order to ensure the seismic design reliability for these structures. The authors have ever studied the effects of the horizontal and vertical simultaneous excitations on the above-mentioned buckling phenomena of support columns experimentally. More-over, they also investigated the fundamental phenomena of the dynamic stability of the support columns subjected to the horizontal and vertical excitations simultaneously by numerical simulations using an analytical model where the support column is treated as a tall elastic cantilever beam. The purpose of this paper is on the dynamic instability, that is dynamic buckling, of a cylindrical shell structures such as those for elevated expressways, towers, containment vessels, LNG tanks and water tanks in various industrial plants so on subjected to horizontal and vertical excitations simultaneously. The coupled motion of equation with horizontal and vertical excitations simultaneously for these cylindrical shell structures is derived in this paper, and this modeling is shown to become a Mathieu type’s parametric excitation. The numerical simulation analysis is carried out for a cylindrical shell model with an attached mass on its tip. Comparing with the classical seismic analysis method, this proposed dynamic instability analysis method shows the larger deformation in horizontal direction due to the parametric excitation of the vertical seismic wave. As the results, the structures are apt to lose the structural stability more due to the coupling effects between the horizontal and vertical seismic simultaneous loadings.
Sloshing Effects on the Seismic Design of Horizontal-Cylindrical and Spherical Vessels
Authors: Karamanos Spyros A.
Published: August 2008

The paper concerns earthquake-induced sloshing analysis in horizontal-cylindrical and spherical industrial vessels. More specifically, the paper focuses on the calculation of the total force in such vessels, due to horizontal seismic excitation. The proposed methodology is based on a “impulsive”–“convective” decomposition of the liquid-vessel total motion, widely used in the design of vertical-cylindrical tanks. This method offers a simple and efficient tool for estimating the total seismic force, considering sloshing effects, and extends the current design practice stated in API 650 and EC8 for vertical cylindrical tanks.
A Dynamic Position Measurement Method for Destructive Process of Structures Using Image Processing
Authors: Nishizawa Hiroshi , Fujita Satoshi , Furuya Osamu
Published: August 2008

In order to clarify the destruction mechanism of large structures in large seismic movements, a non-contacting displacement measurement system with a three-dimensional dynamic position with high precision is required. We have developed a three-dimensional measuring system with image processing using optical motion capture technology. This system consists of light emitting markers installed on the object structure and plural high speed cameras which obtain images of markers’ movement simultaneously, to measure the dynamic position of the three dimensional spatial coordinates of the markers. In order to measure the dynamic position with high precision, we have ever developed sub-pixel processing method which is able to measure very small displacements of the markers by analyzing the luminance distribution. Moreover, we have developed a new marker of spherical surface emission type which formed the luminance profile to improve furthermore the accuracy in rotational movement. Shaking tests were carried out with this measuring system and the results indicated that this system using new markers had sufficient accuracy within errors of a few millimeters in the structure of a 4 meter cube. Consequently, we have acquired the potential to apply to the measurement to the 3-D Full Scale Earthquake Testing Facility (E-Defense).
A Multi-Path Tolerant Displacement Measurement System Using Radio Wave Phase Differences
Authors: Suzuki Nobuhiro , Mikoshiba Tadashi , Mogi Atsushi
Published: August 2008

In quake-proof test facilities, multipoint displacement measurement systems are demanded to analyze quake-destroy mechanisms of structures. As a one of those systems, we have proposed a measurement method using radio wave phase differences. Observing carrier phases of radio waves from transmitters attached on measurement points, the displacement of measurement points can be measured. In this report, we propose an improved measurement method that uses redundant number of sensors to obtain multi-path tolerant capability. We will also report some new experimental results which show the proposed method has sub-centimeter measurement precision.
An Estimation Method for First Excursion Probability of Nonlinear System Using Maximum Response
Authors: Aoki Shigeru
Published: August 2008

The secondary system such as pipings, tanks and other mechanical equipment are installed in the primary system such as building. The important secondary systems should be designed to maintain their function even if they are subjected to destructive earthquake excitations. First excursion failure is one of the most important failure modes. The secondary system has many nonlinear characteristics. In this paper, an estimation methods of the first excursion probability of the secondary system with gap and friction subjected to earthquake excitation is proposed. Restoring force with gap and friction force is equivalently linearized. When the tolerance level is normalized by the maximum response of the secondary system without gap and friction characteristics, variation of the first excursion probability is very small for various values of mass ratio of the secondary system to the primary system, the damping ratio and the natural period.
Unified Procedure for Lifetime Assessment of Components and Piping in WWER NPPs (VERLIFE)
Authors: Brumovsky Milan
Published: August 2008

Main goal of the project within the European Community 5th Framework Program was in a preparation, evaluation and mutual agreement of a “Unified Procedure for Lifetime Assessment of Components and Piping in WWER Type Nuclear Power Plants”. This procedure should be based on former Soviet rules and codes, as WWER components were designed and manufactured in accordance with requirements of these codes and from prescribed materials. Then, critical analysis of possible application of some approaches used in PWR type components was performed and such approaches have been incorporated into the prepared procedure as much as possible with the aim of a harmonization of WWER and PWR Codes and procedures. Preparation of a Unified Procedure for WWERs operating in Finland, Czech Republic, Slovak Republic, Hungary and Bulgaria will increase the level of lifetime/integrity evaluation in these countries and will help to elaborate a unified approach and fully comparable results between individual plants and countries. Then, harmonization with PWR codes allows to obtain results that will be comparable, reliable and more sophisticated as similar approaches will be used in both types of reactors. The paper described main principles, approaches and achievements of the “Unified Procedure...”.
Assessment of Remaining Life for Class 1 Piping Components Experiencing Wall Thinning
Authors: Kumar Rajnish
Published: August 2008

Assessment of remaining life of power plant components is important in light of plant life management and life extension studies. This information helps in planning and minimizing plant outages for repairs and refurbishments. Such studies are specifically important for nuclear power plants. Nuclear Safety Solutions Limited (NSS) is involved in conducting such studies for plant operators and utilities. Thickness measurements of certain piping components carrying fluids at high temperature and high pressure have indicated higher than anticipated wall thinning rates. Flow accelerated corrosion (FAC) has been identified as the primary mechanism for this degradation. The effect of FAC was generally not accounted for in the original design of the plants. Carbon steel piping components such as elbows, tees and reducers are prone to FAC. In such cases, it is important to establish the remaining life of the components and assess their adequacy for continued service. Section XI of the ASME Boiler and Pressure Vessel Code is applicable for evaluation of nuclear power plant components in service. This Section of the Code does not specifically deal with wall thinning of the piping components. Code Case N-597 provides guidelines for evaluation for continued service for Class 2 and Class 3 piping components. For Class 1 piping components, this Code Case suggests that the plant owner should develop the methodology and criteria for evaluation. This paper presents methodology and procedure for establishing the remaining life and assessment of Class 1 piping components experiencing wall thinning effects. In this paper, the rules of NB-3600 and NB-3220 and Code Case N-597 have been utilized for assessment of the components for continued service. Details of various considerations, criteria and methodology for assessment of the remaining life and adequacy for continued service are provided.
Certification Program for Assessing the Mechanical Integrity of Pressure Vessel Systems
Authors: Alexander Chris , Biel Richard
Published: August 2008

Pressure vessels play an integral role in the operation of facilities such as refineries, chemical plants, power plants, both on land and offshore platforms. Consequently, with the increased need for profitable production cycles and pushing pressure systems to their limits, the potential for failures has increased. All of this takes place in an environment where shut-downs and losses of production are expensive. The likelihood for catastrophic failures is also increased, which carries the potential for major costs due to equipment failure, lawsuits, and danger to the public. For these reasons, the Pressure Vessel Certification Program was developed. The cornerstone of this program is technical application of design methods coupled with detailed inspection for assessing the present quality of the vessel. The framework for this effort is built up on careful inspection and readily-accessible documentation that can be used as reference material and integrated within a companies’ risk analysis and safety programs. The long-term element of this program involves regularly-scheduled inspections (e.g. every 3 years) to ensure that the vessel conditions do not change to the point where safe operation is no longer possible. The intent is of the Pressure Vessel Certification Program to ensure that the inspected vessels operate safely for their intended service conditions and intended design lives.
Life Assessment of Components With Underclad Cracks in PWR
Authors: Verdiere Nicolas , Cambefort Pierre , Zamoum Karim , Payraudeau Karl , Royer Se´bastien
Published: August 2008

During the in-service inspection in 1999 in Tricastin 1 Nuclear Plant, underclad cracks had been discovered in the core shell. Following the specific demonstration of the acceptability of these defects, other components also sensitive to this kind of defects have been re-examined. The life assessment includes a review of the mechanism of formation of theses underclad flaws by cold cracking and the selection of the components sensitive to theses cracks. This includes various shells of the reactor pressure vessel, the steam generator and the pressurizer. A second part consists in mechanical analysis of theses selected components, with an underclad flaw of very large size. This is compared with the maximum size of a realistic crack, which depends of the size of the heat affected zone during the cladding process. The third part has to do with the In Service Inspection. This concerns only the reactor pressure nozzles — both inlet and outlet — which are examined during the inspection of the core shell of the reactor vessel.
Equipment Aging Management and Operational Lifetime Extension at the PAKS Nuclear Power Plant
Authors: Katona T. , Bi´ro´ A. Ja´nosine´ , Ra´tkai S. , Pa´lfi T. , To´th A.
Published: August 2008

The design life of the NPP PAKS VVER-440/213 Units is 30 years. The Paks Nuclear Power Plant strategy is to extend the operational lifetime of the plant and renew the operational license for 20 years over the designed and licensed lifetime. The feasibility of plant lifetime extension has been investigated. It has been found that a 20 years extension of operation is feasible from both technical and business point of view. The Licence Renewal regulation based mainly on USNRC approach taking into account the special features of the VVER-440/213 Units and the Periodic Safety Review (PSR) (every 10 years) requirements based on IAEA methods. At Paks NPP the systematic ageing management activities were started ten years ago. Basic results of plant assessment and aging management programs of the main components are discussed in the paper. Summary of the license renewal process and details of the main activities are reported.
French R&D Program for RPV Aging Management
Authors: Churier-Bossennec H. , Moinereau D. , Todeschini P. , Faidy C. , Bezdikian G.
Published: August 2008

Until now French approach for RPV PTS assessment is based on at least 40 years lifetime. This lifetime has been taken into account at each step of the the RPV life: first early in the design, then at each periodic safety demonstration by including the surveillance program, the national and international feedback and R&D results. All of them confirm that all the 3-loop French RPV fulfill the existing criteria for at least 40 years of operation. In order to evaluate their capability to operate for 60 years, an Engineering and Research and Development program has been recently established and engaged by EDF. This large program of activities between all of divisions of EDF is focused on the different fields involved in the risk of fast rupture of the irradiated core vessel. The main purposes of this programme are: • the research of specific data corresponding to a long lifetime of about 60 years; • the studies of new methods to improve the demonstration including several themes such as fluence evaluation, determination of fracture toughness, structural integrity assessment including probabilistic approach, definition of transients; • the evaluation of mitigation methods. This paper contains first a description of what was done at each RPV PTS assessment and an overview of the present program.