bluuebunny/crossref_metadata_2025 huggingface dataset:
Aging Performance of Viton® GLT O-Rings in Radioactive Material Packages (U)
Authors: Skidmore T. E. , Counts K. M. , Fox E. B. , Hoffman E. N. , Dunn K. A.
Published: August 2009

Radioactive material packages used for transportation of plutonium-bearing materials often contain multiple O-ring seals for containment. Packages such as the Model 9975 are also being used for interim storage of Pu-bearing materials at the Savannah River Site (SRS). One of the seal materials used in such packages is Viton® GLT fluoroelastomer. The aging behavior of containment vessel O-rings based on Viton® GLT at long-term containment term storage conditions is being characterized to assess its performance in such applications. This paper summarizes the program and test results to date.
Fatigue Crack Growth Rate Curve for Nickel Based Alloys in PWR Environment
Authors: Nomura Yuichiro , Sakaguchi Katsumi , Kanasaki Hiroshi
Published: August 2009

Japanese reference fatigue crack growth rate (FCGR) curves for ferrite and austenitic stainless steels in light water reactor environments are prescribed in JSME S NA1-2004. However, similar reference FCGR curve for nickel-based alloys for pressurized water reactors (PWR) are not prescribed. In order to propose reference FCGR curve for nickel-based alloys, under high stress ratio and low rising time, the effect of the welding method, the effect of specimen orientation and low stress intensity range fatigue crack propagation tests of nickel-based alloys 600, 132 and 82 weld metals were conducted as part of the Environmental Fatigue Test (EFT) projects of Japan Nuclear Energy Safety Organization (JNES). The results show that the effect of heat, welding methods, specimen orientations and environmental water conditions on the FCGR was not significant for Alloys 600, 132 and 82. The FCGR increased with increase of stress ratio, and cyclic loading frequency. According to the procedure for determining the reference FCGR curve of austenitic stainless steels in PWR environment of nickel-based alloys is proposed based on the reference data and the results of this study. The reference FCGR curve for nickel-based alloys in PWR environment are determined as a function of stress intensity factor range, temperature, load rising time and stress ratio.
Application of Risk-Based Inspection in Ethylene Plant
Authors: Han Jianyu , Gao Jinjin , Chen Guohua
Published: August 2009

Risk-Based Inspection (RBI) began from 1993 and standard was issued in 2000 by API. It is the method of inspection which combines economy with safety [1]. But whether it is suitable for equipments made according to chinese standard needs to be verified. This paper introduces verification of RBI application in Maoming Ethylene Plant.
Utilization of Modern Test Methods and Analyses for Pressure Vessel and Piping Gasket Design
Authors: Daugherty Rita J. , Burkhart Nancy J. , Bolin Lonnie K.
Published: August 2009

Modern, state-of-the-art equipment was recently introduced to the marketplace which allows gasket material manufacturers, fabricators, and end users to test gasket materials and analyze gasket behavior more accurately and precisely than ever before. Previous methods lacked the sophistication of this equipment, or conversely were so complex that the methods were not user friendly. Therefore, this research focuses on providing data from new equipment using newly adopted standards and applying this information to an operational bolted gasketed joint. In addition, the paper describes the test methods, summarizes and analyzes the test results, and discusses incorporating the data into Finite Element Analysis (FEA) modeling of a gasketed joint. The intent of the work is to provide practical information about the behavior of compressed non-asbestos type gaskets under varying conditions, examining this ubiquitous material and how it provides a seal, while elucidating the problems and pitfalls of pressure vessel sealing.
Stress Intensity Factors of Slanted Through-Wall Cracks in Plate and Cylinder
Authors: Huh Nam-Su , Shim Do-Jun , Kim Ji-Ho , Wilkowski Gery M. , Yang Jun-Seok
Published: August 2009

For Leak-Before-Break (LBB) analysis of nuclear piping, a circumferential through-wall crack (TWC) with the crack front parallel to the cylinder radius is typically postulated, i.e., an idealized TWC. Such assumption simplifies the LBB analysis significantly. However, in reality, an internal surface crack grows through the wall thickness and penetrates through the wall thickness at the deepest point. Hence, a TWC with different crack lengths at inner and outer surfaces is formed. Such a TWC is referred to as a “slanted TWC” in the present study. Leak rates as well as SCC and fatigue crack growth rates of slanted TWC are expected to be quite different from those of postulated idealized TWC. In this context, characterization of the actual TWC shape during crack growth due to fatigue or stress corrosion cracking is essential for accurate LBB analysis. Based on detailed 3-dimensional (3-D) elastic finite element (FE) analyses, the present paper provides stress intensity factors (SIFs) for plates and cylinders with slanted TWCs. As for loading conditions, axial tension was considered for the plates, whereas axial tension and global bending were considered for the cylinders. In order to cover the practical range of crack sizes, the geometric variables affecting the SIF were systematically varied. Based on FE analysis results, SIFs along the crack front, including the inner and outer surface points, were provided. The SIFs of slanted TWC can be used to evaluate the fatigue crack growth of a TWC and to perform detailed LBB analysis considering a more realistic crack shape.
Pressure Pulsations by a Centrifugal Compressor at Blade Passing Frequency
Authors: Hayashi Itsuro , Kaneko Shigehiko
Published: August 2009

Pressure pulsations excited by a centrifugal compressor or fan at blade passing frequency may cause severe noise and vibrations in piping systems. Therefore, the practical evaluation method of pressure pulsations is strongly required. In this study, a one-dimensional excitation source model for a compressor was proposed based on the equation of motion. An experiment was performed for the validation of this model. As a result, the relation of the maximum pressure amplitude in piping systems to the location of the excitation source under resonant conditions can be evaluated by introducing the equivalent resistance of the compressor and that of piping systems. The role of the system resistance to the response of pressure pulsations is discussed in detail.
Finite Element Based Plastic Loads for Elbows With Local Wall Thinning
Authors: Kim Jong-Hyun , Oh Chang-Sik , Ahn Joon-Hyuk , Kim Yun-Jae , Park Chi-Yong , Lee Sung-Ho , Kim Tae-Ryong
Published: August 2009

Based on systematic three-dimensional (3-D), large strain FE limit analyses using elastic-perfectly plastic materials, this paper quantifies the effect of local wall thinning on plastic behaviors and TES (twice-elastic-slope) plastic loads for 90° elbows under in-plane bending. The thinning geometry is assumed to be rectangular rather than circular, but the nonlinear geometry effect is fully considered. Results from systematic analyses lead to simple approximations for TES plastic loads, covering a wide range of elbow and thinning geometries.
Influence of Flaw Length on Failure Pressure of Straight Pipe With Wall-Thinning
Authors: Kamaya Masayuki , Meshii Toshiyuki , Suzuki Tomohisa , Yamada Masami
Published: August 2009

Burst tests using straight pipes of carbon steel for high-temperature use with artificial wall-thinning were conducted under internal pressure. Then, three-dimensional elastic-plastic finite element analyses (FEA) was conducted. The validity of the analyses was confirmed by comparing it with the experimental results. Through FEA for various pipe configurations as well as length and depth of the wall-thinning, it was revealed that the influence of the length of the wall-thinning on the failure pressure can be normalized by pipe radius. The failure pressure exhibited dependency on stress-strain relation, and the results obtained from line pipe steel and carbon steel was almost identical, while the stainless steel showed better durability. It was concluded that assessment criteria developed for line pipe steel pipes can be applied for carbon steel and stainless steel pipes conservatively.
Elastic-Plastic J and COD Estimates for Circumferential Through-Wall Cracks Between Elbows and Straight Pipes Under Bending
Authors: Song Tae-Kwang , Kim Yun-Jae
Published: August 2009

A method for elastic-plastic fracture mechanics analyses is presented for the circumferential through-wall crack in weldment joining elbows and attached straight pipes, subject to in-plane bending, based on the reference stress approach. Based on small strain finite element limit analyses using elastic-perfectly plastic materials, closed-form limit loads for circumferential through-wall cracks in between elbows and straight pipes under bending are given. Then applicability of the reference stress based method to approximately estimate J and crack opening displacement (COD) is proposed.
A Management Study of Pressure Relief Valves
Authors: Chien Chi-Hui , Chen Chun-Hung , Lin Yih-Shen
Published: August 2009

As a safety concern, pressure relief valves play important roles in protecting a pressure vessel or pressurized system. The conditions of the pressure relief valves deteriorate day after day which depend on the operating conditions of process train such as variation of pressure and temperature, containment and frequency of relieving during operation. If the deteriorative relief valves failure to operate normally as required, a catastrophic event may occur while no other protective means provided. So, to prepare a plan of inspection and maintenance with suitable intervals based on the knowledge of the relations between the conditions of pressure relief valves and plant operation parameters, is a safety strategy to plant owner. With practical inspection and maintenance works of pressure relief valves performed in a process train, this paper collects the as-received pressure relief valves test results from current inspection intervals and presents the relationships between as-received test data and operation parameters based on analysis of variation (ANOVA) and analysis of correlation. With these analyses, one can get the relationships between the decay conditions of the pressure relieve valves and their operating parameters. A site survey of as-received test results will be used as a case study and the weighting factors corresponding to the operation parameters are also presented.
Finite Element Analysis of a Compressor Housing Used in High Pressure Refrigeration System
Authors: Bosco Raul , Maciel Ricardo Alexandre , Mattar Neto Miguel , Miranda Carlos Alexandre J.
Published: August 2009

In the design of compressors running with high pressure refrigerants, safety aspects must be a mandatory concern. Moreover, when dealing with high pressure levels, compressor components have their original design adapted to withstand such a high pressures, particularly acoustical mufflers, external housing, and compression mechanism. Regarding the external housing, the design approach goes beyond acoustical and aesthetics features as mostly observed in current refrigerating compressors. In order to safety enclose the compression mechanism the application of a proper design methodology is mandatory to safeguard the structural integrity of both the compressor external housing and the whole refrigerating system. Looking for acceptable, cost effective safety factors, a simultaneous design approach including advanced structural mechanics techniques, experimentation, safety Codes revision, and Computer Aided Engineering (CAE) tools application is mandatory. The aim of this work is to present a new development approach, concerning structural design of a compressor housing used in high pressure refrigeration system. Numerical and experimental results will be compared among each other aiming to evaluate some ASME Codes criteria and design procedures.
Helmholtz Absorbers: Experiments in Controlling Resonant Pulsation Without the Use of Orifice Plates
Authors: Broerman Eugene L. , Smolik Mitchel A. , Scrivner Christine M.
Published: August 2009

Pressure drop has been used for more than half a century to control resonant pulsation in reciprocating compressor piping. Although avoiding these resonances is the preferred method, this is not possible in many high-speed/variable-speed installations. In these cases, resonant pulsation is often managed by using orifice plates to dampen the response. Helmholtz absorbers are an old technology, used to improve the acoustics of ancient Greek theaters and modern recording studios alike. Although their application in the field of piping acoustics has been well documented, this paper presents new ways in which they have not yet been applied. In this paper, experimental data is shown for a self-tuning Helmholtz absorber, or Side Branch Absorber (SBA) used to cancel a piping length resonance, and for a Virtual Orifice that is used to reduce cylinder nozzle pulsation. These devices open up new doors for controlling pulsation with reduced horsepower costs in reciprocating compressor installations.
Distortion of Polymer Matrix Composite Panels Under Transverse Thermal Gradients
Authors: Gu Pei , Asaro R. J.
Published: August 2009

This paper discusses the distortion of panels made by fiber reinforced polymer matrix composites under transverse thermal-loading conditions. We formulate thermal distortion from the bending theory of functionally graded materials. General solution for thermal distortion is derived in terms of material variation and temperature profile along the thickness of the panels. Using the general solution, analytical expressions of thermal distortion and associated internal forces for commonly used end supports are obtained. From these solutions, we discuss the failure mechanism induced by thermal distortion and design criteria that can be placed to prevent such failure. The roles of geometry, temperature and temperature gradients, and the competition among them in the process of structural failure are addressed.
Reliability of System With Hysteresis Loop Characteristic Subjected to Earthquake Excitations
Authors: Aoki Shigeru
Published: August 2009

Estimation of reliability of system subjected to earthquake excitations is important problem for aseismic design. Reliability of such system should be evaluated in probabilistic manner. First excursion failure is one of the most important failure modes of structures and one of a factor of reliability. Many structures have nonlinear characteristics. Hysteresis loop characteristic caused by plastic deformation is one of the most common nonlinear characteristics observed in pressure vessels and piping systems. In this paper, an estimation method for the first excursion probability of structure with hysteresis loop characteristic is proposed. The first excursion probability is the function of many parameters. First excursion probability is obtained by using artificial time histories. It is shown that when the tolerance level is normalized by the expected values of the maximum response of the structures, the first excursion probability can be shown independent of many parameters.
Outline of the JSME Rules on Pipe Wall Thinning Management for Thermal Power Generation Facilities
Authors: Nishiguchi Isoharu , Hamada Seiichi
Published: August 2009

In response to the pipe wall thinning damage experienced in power plants in 2004, the Japan Society of Mechanical Engineers (JSME) has started activities to develop technical standards on the pipe wall thinning management. The first edition of the JSME rules on pipe wall thinning management for thermal power generation facilities (JSME S TB1-2006 [1]) was issued in March 2006, and its latest edition will be issued in 2007, which describes the technical requirements to meet the JSME performance-based rules for pipe wall thinning management (JSME S CA-1 2005 [2]). Based on 24,774 inspection data obtained at the thermal power plants in Japan, the latest JSME rules will show the specific attention to the need for inspection of piping systems that are susceptible to the wall thinning damage. The JSME rules describe the selection of thickness measurement locations such as downstream of piping configurations that produce turbulence, downstream of orifices, downstream of control valves, and they describe the periodic inspections including the first inspection to be scheduled taking the wall thinning rate data at the equivalent locations into consideration. The JSME rules stipulate some available inspection methods such as ultrasonic scanning, radiographic profile, eddy current and potential drop technique. This paper presents outline of the JSME rules including basic philosophy, technical requirements on the inspection and testing practices and the relation with the regulations in Japan.
Improved Design for Hypercompressor Packing Cups
Authors: Campo Nicola , Chiesi Francesco
Published: August 2009

Second stage cylinders for polyethylene hyper compressors are among the most stressed pressure vessels in the industry. Due to the high operating pressure and pressure fluctuations between suction and discharge, these cylinders must be designed to withstand high fatigue loads. Packing cups are the most critical cylinder component and, in particular, the lube oil ducts are the bottleneck for reliability. This work deals with a structural optimization of packing cups focused on the most critical packing cup area: the lube oil hole. Various pre-compression techniques (i.e., shrink-fit and autofrettage) are used to improve the fatigue behavior. Longer life and reliability are investigated with advanced design techniques such as finite element modeling and design of experiments. New design cups with a 50% higher fatigue safety factor have been obtained.
Regulatory and Industry Guidance on Use of Risk Technology in Nuclear Power Plant Applications
Authors: Sanwarwalla Mansoor H.
Published: August 2009

Since the United States Nuclear Regulatory Commission (USNRC) published its landmark “Reactor Safety Study — An Assessment of Accident Risks in U. S. Commercial Nuclear Power Plants” in late 1975, commercial nuclear power industry, encouraged by the USNRC, have since then been applying Probabilistic Risk Assessment (PRAs) in their nuclear power units in areas of in-service testing, in-service inspection, quality assurance, technical specifications, maintenance, etc. To guide and regulate the industry in use of PRAs, Regulatory Guides and Standards have been written and are being revised continuously by the USNRC, American Society of Mechanical Engineers (ASME) and American Nuclear Society (ANS). The current use of PRA takes credit for single failure criterion based on applicability of codes and standards. The proposed new USNRC regulation 10 CFR Part 53 applicable for all reactor technologies is silent on the applicability of current standards endorsed by the regulatory body. The impact of the proposed new rule to both new and the current application needs to be studied. This paper will review the application of the various guidance documents for their use in commercial nuclear power plants with emphasis on the new generation nuclear power plants.
Elastic-Plastic Finite Element Simulation and Fatigue Life Prediction for Beam and Elbow Under Cyclic Loading
Authors: Zhu Xian-Kui , Leis Brian N.
Published: August 2009

Work hardening and Bauschinger effects on plastic deformation and fatigue life for a beam and an elbow under cyclic loading are examined using finite element analysis (FEA). Three typical material plastic hardening models, i.e. isotropic, kinematic and combined isotropic/kinematic hardening models are adopted in the FEA calculations. Based on the FEA results of cyclic stress and strain at a critical location and using an energy-based fatigue damage parameter, the fatigue lives are predicted for the beam and elbow. The results show that (1) the three material hardening models determine similar stress at the critical location with small differences during the cyclic loading, (2) the isotropic model underestimates the cyclic plastic strain and overestimates the fatigue life, (3) the kinematic model overestimates the cyclic plastic strain and underestimates the fatigue life, and (4) the combined model predicts the intermediate cyclic plastic strain and reasonable fatigue life.
Gross Plastic Deformation of a Hemispherical Head With Cylindrical Nozzle: A Comparative Study
Authors: Naruse Tomohiro , Mackenzie Donald , Camilleri Duncan
Published: August 2009

The plastic load of a hemispherical head with a cylindrical nozzle subject to an internal pressure and/or moment is established using two new plastic criteria; the plastic work curvature (PWC) criterion and the ratio of plastic to total work curvature (RPWC) criterion. The calculated plastic loads are compared to ASME Design by Analysis stress categorization and limit analysis allowable loads. The stress categorization approach is seen to be dependant on the appropriate choice of stress classification lines and the classification of primary, secondary and peak stresses. The limit load approach is simpler to apply but does not consider material strain hardening and/or large deformation behaviour and may often lead to conservative design loads. In the plastic analyses, strain hardening material models and large deformation analyses are considered. The calculated allowable pressure-moment interaction surfaces are assessed and compared for the different methods.
Experimental Study of Three-Dimensional Identification of Semi-Elliptical Crack on the Back Surface by Means of Direct-Current Electrical Potential Difference Method of Multiple-Point Measurement Type
Authors: Tada Naoya , Uchida Makoto , Funakoshi Akira , Ishikawa Hiroki
Published: August 2009

A method for identification of a semi-elliptical crack existing on the back surface of the material by means of direct-current electrical potential difference method of multiple-point measurement type was proposed. The geometry of the crack was given by the two-dimensional location of the crack center, the surface and inward angles of the crack, and the length and depth of the crack. The identification was carried out based on the distribution of potential difference on the surface. The related experiments were carried out using six metal plates with various semi-elliptical cracks made on the back surface by electric discharge machining. The geometry of the crack was successfully identified by the proposed method and the results were discussed.
Reduction of Seismic Response of Mechanical System by Base Isolation System With Friction Bearing
Authors: Aoki Shigeru , Nakanishi Yuji , Tominaga Kazutoshi , Otaka Takeshi , Nishimura Tadashi , Inagaki Mitsuyoshi , Kanazawa Mitsuo , Kawaguchi Sumio
Published: August 2009

Reduction of seismic response of mechanical system is important problem for aseismic design. Some types of base isolation systems are developed and used in actual base of buildings and floors in buildings for reduction of seismic response of mechanincal system. In this paper, a base isolation system utilizing bearing with friction and restoring force of bearing is proposed. Friction bearing consists of two plates having spherical concaves and oval type metal or spherical metal with rubber. First, effectiveness of the base isolation system is examined experimentally. Using artificial time histories, the isolated table is shaken on the shaking table. The maximum value of response is reduced and sum of squares of response is significantly reduced. Power spectrum is significantly reduced in almost of all frequency regions, except for very low frequency region. Next, in order to examine reduction of seismic response of actual mechanical system, a console rack is set on the isolated plate. Seismic response is also significantly reduced. Finally, obtained results of experiment are examined by simulation method. An analytical model considering friction and restoring force is used. From simulation method, effectiveness of the proposed base isolation system is demonstrated.
Insights Arising From a Comparison of the tanh and Exponential Fitting Methods for Charpy V-Notch Energy Data
Authors: EricksonKirk MarjorieAnn , EricksonKirk Mark T. , Rosinski Stan , Spanner Jack
Published: August 2009

In the 1960s and 1970s when the surveillance programs for currently operating commercial nuclear reactors were established state of knowledge limitations resulted in the use of Charpy-V notch (CVN) specimens rather than fracture toughness specimens. Reasonable success has since been achieved in correlating CVN and fracture toughness parameters. Such correlations provide an important part of the technical basis for both current regulations and ASME codes. These correlations imply that trends manifest in CVN data must also appear in fracture toughness data even though empirical evidence demonstrates that this is not always true. For example, the temperature dependence of CVN energy (CVE) in transition is thought to be a unique feature of each specific sample of ferritic steel that is tested, a view in sharp contrast with the now widely accepted view of a “Master Curve” for transition fracture toughness (KJc). Also, effects of product form on CVE temperature dependence and property correlations are widely reported despite the fact that product form effects are absent from KJc properties. These observations suggest that the mapping of CVE behavior onto fracture toughness implicit to correlation-based regulations and ASME codes may produce erroneous trends in estimated values of fracture toughness. In this paper we investigate the hypothesis that the apparent differences between CVE and fracture toughness arise due to differences in how the temperature dependence of CVE and KJc data have historically been modeled. Our analysis shows that when CVE data are analyzed in a manner consistent with KJc data (i.e., transition and upper shelf data are partitioned from each other and analyzed separately rather than being fit with a continuous tanh function) the apparent differences between CVE and toughness characterizations are minimized significantly, and may disappear entirely. These findings demonstrate the differences between CVE and fracture toughness data to be an artifact of the tanh analysis method rather than an intrinsic property of CVE.
Researching Methods to Study Creep Strain Variations in Power Station Steam Plant
Authors: Morris Andy , Maharaj Chris , Puri Amit , Kourmpetis Miltiadis , Dear John
Published: August 2009

A research programme to investigate different methods of measuring creep strain rate in steam pipes and other power station components is described. One of the studies is to obtain more information of the changing distribution of creep strain around welded joints, changes in cross-section and other features in steam pipes and other power plant components. One method being developed is to use Digital Image Correlation (DIC) together with the E.ON UK ARCMAC gauges. The latter to provide an integrated creep strain rate, with the DIC method revealing the local creep strain rate distribution around the ARCMAC gauges. To validate this approach, laboratory specimens have been prepared that have known faults to ratify the measurement data obtained and its sensitivity to small changes in the studied specimens. Parallel to this laboratory research are investigations as to how best to use the DIC method on working steam pipes and other components of power stations.
Dynamic Crack Propagation and Arrest in PWR Pressure Vessel Steel: Interpretation of Experiment With the X-FEM Method
Authors: Prabel B. , Marie S. , Combescure A.
Published: August 2009

In the frame of analysis of the pressure thermal shock in a PWR RVP and the associated R&D activities, some developments are performed at CEA on the dynamic brittle propagation and crack arrest. This paper presents a PhD work on the modeling of the dynamic brittle crack growth. For the analyses, an important experimental work is performed on different geometries using a French RPV ferritic steel: Compact Tension specimens with different thickness, isothermal rings under compression with different positions of the initial defect to study a mixed mode configuration, and a ring submitted to thermal shock. The first part of this paper details the test conditions and main results. To propose an accurate interpretation of the crack growth, a viscous-elastic-plastic dynamic model is used. The strain rate influence is taken into account based on Cowper-Symond’s law (characterization was made from Split Hopkinson Pressure Bar tests). To model the crack propagation in the Finite Element calculation, eXtended Finite Element Method (X-FEM) is used. The implementation of these specific elements in the CEA F.E. software CAST3M is described in the second part of this paper. This numerical technique avoids re-meshing, because the crack progress is directly incorporated in the degrees of freedom of the elements crossed by the crack. The last part of this paper compares the F.E. predictions to the experimental measurements using different criteria. In particular, we focused on a RKR (Ritchie-Knott-Rice) like criterion using a critical principal stress in the front of the crack tip during the dynamic crack extension. Critical stress is found to depend on crack speed, or equivalently on strain rate. Good results are reported concerning predictive simulations.
Use of a CFD-Tool for Assessment of the Reactor Pressure Vessel Integrity in Pressurised Thermal Shock Conditions: Thermal-Hydraulic Studies of a Safety Injection in a PWR Plant — Methodology and Present Limitation
Authors: Martin A. , Bosse S. , Lestang F.
Published: August 2009

Integrity evaluation methods for nuclear Reactor Pressure Vessels (RPVs) under Pressurised Thermal Shock (PTS) loading are applied by French Utility. They are based on the analysis of the behaviour of cracks under PTS loading conditions due to the emergency cooling during PTS transient like SBLOCA. This paper explains the Research and Development program started at Electricite´ De France about the cooling phenomena of a PWR vessel after a Pressurised Thermal Shock. The numerical results are obtained with the E.D.F ThermalHydraulic code (Code_Saturne) coupled with the thermal-solid code SYRTHES to take into account the conjugate heat transfer on the cooling of the vessel. We first explain the global methodology with a progress report on the state of the art of the tools available to simulate the different scenari displayed within the frame of the plant life project in order to reassess the integrity of the RPV, taking into account the evolution of some input data, such as the new value of end of life (EOL) fluence, the feedback results of surveillance program and the evolution of the functional requirements. The main results are presented and are related to the evaluation of the RPV integrity during a Small Break Loss Of Coolant Accident transient for 900 and 1300 MWe nuclear plant. On the whole, the main purpose of the numerical CFD studies is to accurately estimate the distribution of fluid temperature in the down comer and the heat transfer coefficients on the inner RPV surface for a fracture mechanics computation which will subsequently assess the associated RPV safety margins. In a second time, a new analysis is performed to assess an accurate temperature distribution in the RPV. Indeed, from a physical phenomena point of view, the EDF thermalhydraulic tool Code_Saturne is now qualified in order to assess single phase transient but in the case where the cold legs are partially filled with steam, it becomes a two-phase problem and new important effects occur, such as condensation due to the emergency core cooling injections of sub-cooled water. Thus, an advanced prediction of RPV thermal loading during these transients requires sophisticated two-phase, local scale, 3D codes. In that purpose, a program has been set up to extend the capabilities of the Neptune_CFD two-phase solver which is the tool able to solve two phase flow configuration. In a same time, A simplified approach has showed that for a type of transient weakly uncovered, a free surface calculation was sufficient to respect the necessary criteria of safety. A Qualification study was carried out on the Hybiscus experimental E.D.F facility, representing a cold leg with ECC injection and a third down comer. Temperature profiles have been compared and are presented and analysed here, showing encouraging results.
Effect of Autofrettage in the Thick-Walled Cylinder With a Radial Cross-Bore
Authors: Li Hongjun , Johnston Richard , Mackenzie Donald
Published: August 2009

The effect of autofrettage on the stress level in thick-walled cylinders with a radial cross-bore is investigated by applying inelastic FEA with cyclic pressure loading. A macro is created in ANSYS to calculate the equivalent alternating stress intensity, Seq, based on the ASME Boiler and Pressure Vessel Code. The value of Seq is used to evaluate the fatigue life of the vessel. For a specific cyclic load level, a distinct optimum autofrettage pressure is identified by plotting autofrettage pressure against the number of cycles from design fatigue data. The fatigue life of the autofrettaged vessel with such an optimum pressure is significantly increased compared with the case where no autofrettage is used.
Effect of Impact Limiter Material Degradation on Structural Integrity of 9975 Package Subjected to Two Forklift Truck Impact
Authors: Wu Tsu-Te
Published: August 2009

This paper evaluates the effect of the impact limiter material degradation on the structural integrity of the 9975 package containment vessel during a postulated accident event of forklift truck collision. The analytical results show that the primary and secondary containment vessels remain structurally intact for Celotex material degraded to 20% of the baseline value.
UK Research Programme on Residual Stresses: Progress to Date
Authors: Bate S. K. , Warren A. P. , Watson C. T. , Hurrell P. , Francis J. A.
Published: August 2009

A long-term UK research programme on residual stresses was launched in 2004. It involves Rolls-Royce plc and Serco Assurance, and is supported by UK industry and academia. The programme is aimed at progressing the understanding of weld residual stresses and the implementation of finite element simulation and residual stress measurement for assessing the integrity of engineering structures. Following on from this, the intention is then to develop improved guidance on residual stress modelling techniques. In the first two years finite element activities have addressed heat source representation, simplified modelling (e.g. 2D v 3D, bead lumping), material hardening models, high temperature behaviour and phase transformations. It is recognized that simplifying assumptions have to be made in order to reduce the computational run-time and modelling complexity, especially for multi-pass welds. The effects of these assumptions on the determined stresses have been considered by carrying out finite element analyses of welded mock-ups. The welded mock-ups have been developed to provide measured residual stress data which are necessary to validate the modelling techniques that have been developed. These activities have been used to support the development of guidelines on the use finite element analysis to predict residual stresses in welded components. These guidelines will be incorporated in the next issue of the British Energy R6 defect assessment procedure.
Custom Material Modeling Within FEA for Use in Autofrettage Simulation
Authors: Gibson Michael C. , Hameed Amer , Hetherington John G. , Parker Anthony P.
Published: August 2009

Finite Element Analysis (FEA) has been widely adopted. For autofrettage analysis, in order to represent real conditions and materials, it is necessary to properly model end conditions and material behavior, in particular the loss of compressive strength following prior tensile plastic strain, termed the ‘Bauschinger Effect’. The latter is a strong function of prior plastic strain and therefore of location; this implies the need to model a different material unloading behavior at each location in the tube. Two possible methods of implementing such a behavior within FEA are examined. These are an ‘elastic modulus and Poisson’s ratio adjustment procedure’ (EMPRAP) and a ‘user programmable feature’ (UPF). Finally the results are compared to an independent, non-FEA, EMPRAP numerical solution. Close agreement between all three methods is demonstrated. The UPF approach, validated here, is applicable in more complex loading scenarios.
Thermal Fatigue Testing and Analysis of a Thick Perforated Ring
Authors: Damiani T. M. , Holliday J. E. , Zechmeister M. J. , Reinheimer R. D. , Jones D. P.
Published: August 2009

Thermal fatigue cracking has been observed for thick perforated spacer rings used as part of a thermal fatigue test loop operating at Bechtel Bettis, Inc. The perforated rings are used for instrumentation access to the fluid flow at the test specimen inlet and outlet, and are subject to alternating hot and cold forced flow, low oxygenated water every three minutes so that rapid changes in water temperature impart a thermal shock event to the inner wall of the rings. Thermal and structural three dimensional elastic and elastic-plastic finite element analyses (FEA) were conducted for the ring and the results used to predict fatigue crack initiation using strain-based fatigue-life algorithms. Predicted cycles-to-crack initiation agreed well with the observed cracking when alternating shear strain intensity analogous to the Tresca stress was used. This analysis qualifies the use of FEA for thermal fatigue assessments of complicated three-dimensional components.
Seismic Evaluation of Atypical Special Plate Shear Walls
Authors: Russell M. J. , Spears R. E. , Kobbe R. G.
Published: August 2009

The structure of a building undergoing a seismic reevaluation at the Idaho National Laboratory includes a number of steel plate walls and a roof liner which will act as shear diaphragms during an earthquake. Since the facility was designed and built long before such criteria were formulated, it is not surprising that these walls are not configured to meet all of the recently formulated requirements for such structures. To take advantage of these unusual structural elements, nonlinear analysis was used to ensure accurate modeling of the plate walls in a linear elastic seismic analysis of the full superstructure. The modeling was also used to establish the capacity of the plate.
Accidental Drop of a Carbon Steel/Lead Shipping Cask at Low Temperatures
Authors: Hawkes Brian D. , Durstine Kenneth R.
Published: August 2009

A shielded cask is used to transport radioactive materials between facilities. The cask was fabricated with an outer and inner shell of hot rolled low carbon steel. Lead was poured in the annular space between the shells to provide radiation shielding. Carbon steel is known to be susceptible to low-temperature brittle fracture under impact loading. This paper will present the analysis results representing postulated transportation accidents during on-site transfers of the cask. The accident scenarios were based on a series of cask drops onto a rigid surface from a height of 6 ft assuming brittle failure of the cask shell at subzero temperatures. Finite element models of the cask and its contents were solved and post processed using ABAQUS software. Each model was examined for failure to contain radioactive materials and/or significant loss of radiation shielding. Results of these analyses show that the body of the cask exhibits considerable ruggedness and will remain largely intact after the impact. There will be deformation of the main cask body with localized brittle failure of the cask outer shell and components and but no complete penetration of the cask shielding. The cask payload outer waste can will experience some permanent plastic deformation in each drop, but will not be deformed to the point where it will rupture, thus maintaining confinement of the can contents.
Comparison of Decoupled and Coupled Analyses for Hydrogen Transport in Fracture Specimens
Authors: Kim Y. , Chao Y. J. , Morgan M. J. , Lam P.-S.
Published: August 2009

Hydrogen embrittlement is an important issue in many industries. Fracture resistance of metals is often weakened by the presence of hydrogen. In this paper, two diffusion models are compared for hydrogen transport analysis. One is the coupled model where the concentration of hydrogen in the lattice is integrated with mechanical properties. The other is the decoupled model in which the hydrogen diffusion is independent of the mechanical properties; but depends on the stress state. Finite element analyses are performed for a boundary layer specimen with a blunting crack and a four-point bend specimen with rounded notch. Hydrogen concentration profiles around the blunt crack (or notch) are compared under different boundary conditions and material properties. It is observed that, in spite of the difference in constitutive models, there is a similarity between hydrogen concentration in normal interstitial sites by the two models. In case that large plastic strain is present (such as those in low to moderate strength steels) there is a substantial difference in hydrogen concentration between the two models.
A Tribute to Spencer H. Bush: His Abilities and Accomplishments—A Personal Perspective
Authors: Chockie Larry J.
Published: August 2009

This author had the pleasure of knowing and working with Spencer H. Bush, from the time he began his career at the Hanford Atomic Plant operated by the General Electric Company for the Atomic Energy Commission until his demise. This paper presents some of the unusual attributes he possessed, such as speed reading, his memory retention, and a connoisseur of fine wines. Papers presented following this presentation will emphasize and extol his accomplishments in the technical and engineering areas addressing the nuclear power industry. My remarks are from a perspective of serving with Spence for half a century and to emphasize his remarkable humanistic attributes, for example his ability to read a lengthy novel at the rate of a page every few seconds, and his photographic retention of the subject and details.
Mixed Mode I/III Crack-Tip Fields for Perfectly Plastic Mises Materials
Authors: Pan J.
Published: August 2009

In this paper, governing equations and solutions for asymptotic singular and non-singular crack-tip sectors in perfectly plastic Mises materials are first reviewed under combined in-plane and out-of-plane shear loading conditions. The crack-tip fields under mixed mode I/III loading conditions are then investigated. One assembly of four crack-tip plastic sectors is adopted with stress discontinuities along the border of two constant stress sectors. The solutions of the crack-tip fields under pure mode I and mixed mode I/III loading conditions are presented. The crack-tip fields under pure mode I and mixed mode I/III loading conditions give fully-plastic solutions with various hydrostatic tensile stresses ahead of the crack tip. The characteristics of the mode I limits of fully plastic crack-tip fields with different hydrostatic tensile stresses ahead of the crack tip agree well the past computational results under pure mode I with different constraint conditions.
Characterisation of Ductile Crack Growth Behaviour Through a Novel Normalised P-ΔLL Master Curve
Authors: Mourad Abdel-Hamid I. , Abu-Assi Aladdin
Published: August 2009

This paper presents findings of fracture experiments and analyses obtained as part of research on stable crack growth behaviour in low alloy steel (EN 34NiCrMo6). Results of fracture tests conducted on CT specimens of low constraint (section slenderness ratio, b0/B ∼6), with various a0/W ratios and different loading angles, φ, are presented. Analysis of results revealed that the point at which behaviour departs from linearity (attributed to initiation of stable crack behaviour) is similar relative to maximum-recorded load, Pmax. The load-line displacement, ΔLL at Pmax, ΔPmax, was also found to be similar. An attempt was made thus at representing results of fracture tests, in terms of a normalised P-ΔLL curves. Normalised experimental plots have shown to represent a single “master” curve characterising stable crack growth behaviour. The proposed method was also applied to other experimental data in the literature on other materials and of other specimen configurations and loading modes. Comparisons do show that the experimental results reduce to a single trendline. The proposed normalisation therefore does provide promising results in characterising stable crack growth behaviour and can contribute greatly to the addressing of transferability issue of fracture tests of low constraint specimens.
Investigation of Thermal Fatigue Cycling in Drain Lines
Authors: McGill Robert O. , Deardorff Arthur F. , Peltola David W. , Chu Shannon
Published: August 2009

Several instances of thermal fatigue cracking in small-diameter PWR branch lines off reactor main loop piping led to an industry program to evaluate the loading mechanisms responsible for the cracking. It was found that swirl penetration of hot reactor coolant into the normally stagnant drain lines can result in cyclic thermal stratification in the horizontal run of the drain driving the thermal loading. Models were developed to predict the thermal conditions and cyclic behavior that resulted in the cracking. Thermal transient and stress analysis was conducted to test the model predictions and to assure that cracking could be predicted. Further review was conducted for the related piping events where leakage had occurred. These investigations provided considerable insight into how to evaluate the larger populations of lines in operating plants where there have been no indications of cracking. These investigations have shown that two cases of cracking were due to un-insulated configurations that resulted in high cycling temperature differentials in the region of cracking. In addition, the lines where cracking occurred had rigid vertical supports in the region of stratification, leading to high elbow bending moments as a result of the constraint.
The 2006 Forum on Seismic Design of Piping Systems for the Year 2010
Authors: Slagis Gerry C.
Published: August 2009

A summary of The 2006 Forum on Seismic Design of Piping Systems for the Year 2010 is provided. This forum session is the tenth in a series that was started in 1992. Previously, the title was Appropriate Criteria and Methods for Seismic Design of Nuclear Piping. In this 2006 forum, the main topics of discussion were: “SSE only” design, a comparison of the Level B (OBE) and Level D (SSE) design requirements, and inspection after an earthquake.
Creep Amendments in the European Standard EN 13445
Authors: Baylac Guy , Kiesewetter Norbert , Zeman Josef , Handtschoewercker Alain , McFarlane Rod , Delle Site Corrado , Tonti Andrea , Holdsworth Stuart
Published: August 2009

This paper describes the Creep Amendments which will be implemented in EN 13445, the European Standard for Unfired Pressure Vessels, in 2007. It will address four topics: 1) Specifications for Materials and Weldments. 2) Specifications for Design By Formula and Damage Accumulation rules. 3) Specifications for Design By Analysis — Direct Route (Creep Rupture, Excessive Creep Strain, Creep and cyclic Fatigue Interaction). 4) Specifications for Inspection and Non-Destructive Testing (NDT).