bluuebunny/crossref_metadata_2025 huggingface dataset:
A Practical Criterion on Fatigue Crack Growth Rates at Notches and Its Application to Part-Through-Thickness Fatigue Cracks in Notched Plates Subjected to Cyclic Bending
Authors: Matsuno Hiroshi
Published: July 2008

In the present paper, an equivalent stress ratio concept, which has hitherto been developed by author [1–3], is applied to problems of part-through-thickness fatigue crack growth in notched plates subjected to cyclic bending loads, and a criterion for estimating fatigue crack growth rates is derived on the basis of the concept. In order to take a great variety of practical notches into consideration, a bending stress field of a notched plate containing a part-through-thickness fatigue crack emanating from a notch root is simplified by the elementary beam theory, and the stress field is characterized in accordance with classification of notch morphology: (a) an unnotch type, (b) a transverse type notch such as a groove, a shoulder, a trapezoidal protuberance, etc., which is disposed along a width of a plate, and (c) a through-thickness type notch such as a circular and elliptical hole, a side-groove, etc. Experimental results on part-through-thickness fatigue cracks emanating from artificial flaws at notch roots in plates subjected to cyclic bending loads are analyzed. Growth rates of fatigue cracks in the notches are estimated based on the proposed criterion and the devised convenient method for calculating stress intensity factors, and they are compared with experimental ones.
Influence of Axial Force on the Flexural Deflection of Euler-Bernoulli Beam Structures Solved by DQEM Using EDQ
Authors: Chen Chang-New
Published: July 2008

The influence of axial force on the flexural deflection of Euler-Bernoulli beam structures is analyzed by differential quadrature element method (DQEM) using extended differential quadrature (EDQ). The DQEM uses the differential quadrature to discretize the governing differential equation defined on each element, the transition conditions defined on the inter-element boundary of two adjacent elements and the boundary conditions of the beam. Numerical results solved by the developed numerical algorithm are presented. The convergence of the developed DQEM analysis model is efficient.
Partial Safety Factor (PSF) Approach in Japanese FFS Code, HPIS Z101 Level 2
Authors: Kojima Ikuo , Konosu Shinji
Published: July 2008

One of the features of HPIS Z101 Level2 method, which is to be published as a Japanese Fitness-For-Service (FFS) code for pressure equipment, is to use plural FADs (Fracture Assessment Diagrams) dependent on the materials. Regarding the FFS assessment methods for a crack-like flaw, Partial Safety Factor (PSF) is becoming a major approach in considering the effect of the variance of parameters for the assessment, such as applied load, material properties and detected dimensions of the flaws concerned. To apply this approach to the HPIS code, different PFSs for FADs dependent on materials should be prepared. PSFs with various conditions are calculated for the HPIS code, by the AFOSM (Advanced First-Order Second Moment) method. Comparison with PSFs in other preceding FFS codes, such as API 579-2000 and BS 7910-2005, is being conducted.
Effects of Scatter in Bolt Preload on the Sealing Performance in Bolted Flange Connections With Cover of Pressure Vessel Under Internal Pressure
Authors: Nagata Satoshi , Sawa Toshiyuki , Hamamoto Seiichi
Published: July 2008

It has been well known that the scatter in axial bolt forces of bolted flange connections tightened by torque control methods is substantial. In evaluating the sealing performance of a bolted flange connection with a gasket subjected to internal pressure, it is necessary to know the contact gasket stress distributions due to the scatter of the axial bolt forces in the flange connections tightened by torque control methods. This paper deals with the leakage of a bolted flange connection with a cover of pressure vessel including a spiral wound gasket tightened by a torque wrench. The scatter in the axial bolt forces was measured using strain gauges attached at the shank of bolts. The amount of leakage from the bolted flange connection with cover of pressure vessel was measured by so-called pressure decay method. The gas employed was Helium. From the measured leakage, the actual assembly efficiency is examined. The eight bolts and nuts were tightened according to the ASME PCC-1 method and Japanese method developed by High Pressure Institute (HPI). The difference in the bolt preload was shown between the ASME method and the HPI method. The contact gasket stress distributions at the interface of the flange connection with the gasket were calculated under the measured axial bolt forces by means of finite element analysis. Using the calculated gasket contact stress distribution, the amount of gas leakage was estimated. The estimated gas leakage was compared with the measured results.
A Rational Identification of Creep Design Area Using Negligible Creep Curves
Authors: Sukekawa Masayuki , Isobe Nobuhiro , Shibamoto Hiroshi , Tanaka Yoshihiko , Kasahara Naoto
Published: July 2008

For extension of non-creep design area and simplification of design procedures, a rational identification method of creep design area by negligible creep (NC) curves was studied. NC curves of six kinds of austenite stainless and ferrite steels for fast reactors were determined based on domestic material data. NC curves provide the relation between temperature and time that does not induce damageable creep strain under the constant stress 1.5Sm (Sm: design stress intensity). In existing Japanese design guides, non-creep design area is severely restricted by constant upper temperature limit for austenite stainless steel and ferrite steel. In the case of 316FR steel and SUS410J3, which are candidate materials of Japanese commercialized fast reactors and have excellent material property, this limit can be extended by NC curve concept considering the duration of high temperature operation. NC curves under secondary stress considering stress relaxation were also studied. However, rationalization effect was insufficient whereas evaluation process was too complex. Therefore, at the present stage, NC curves at constant stress level 1.5Sm were adopted to identify creep design area. The concept of NC curve was introduced into the interim structural design guide for commercialized fast reactors in Japan to simplify the creep design of fast reactor systems. Utilizing these curves, non-creep design becomes possible for components operated at comparatively lower temperature in normal condition.
Application of Plastic Region Tightening Bolt to Flange Joint Assembly
Authors: Kaneda Shinobu , Tsuji Hirokazu
Published: July 2008

Elastic region tightening based on torque control method is conventional method of tightening a bolt. Axial force of the bolt is controlled by a torque wrench, however, it is not easy to achieve uniform bolt tightening force. When torque method is applied to flange joint assembly, the scatter of the bolt tightening foeces are large. They might cause the leakage of the internal fluid from a flange joint. Recently, plastic region tightening is remarked for critical applications, which provides good uniformity in bolt preloads and high preloads compared with the elastic region tightening. In this research, the plastic region tightening is applied to flange joint assembly and its superiority in uniformity of the bolt tightening force is demonstrated. For the tightening tests, JPI-4inch flange, spiral wound gaskets and M16 bolts were used. Axial force and elongation of all bolts in the flange were measured. Bolts were tightened by modified HPIS flange tightening procedure which incorporates the angle control method into the clockwise tightening sequence. Experimental results show that variations of the axial force in the plastic region was smaller than those in the clastic region. The influence of the elastic interaction on the axial force in the plastic region is also small. It is concluded that the application of plastic region tightening to flange joint assembly is effective for the leak-free joint and that the nominal diameter of the bolt can be reduced.
Statistical Analysis of Glovebox Glove Failure
Authors: Pines E. , Park Y. H. , Ofouku M. , Cournoyer M. E.
Published: July 2008

The Nuclear Materials Technology (NMT) Division has the largest inventory of glovebox gloves at Los Alamos National Laboratory (LANL). Consequently, the minimization of unplanned breaches of the glove material, typically resulting in glove failures, is a significant safety concern in the daily operations in NMT Division facilities. To investigate processes and procedures that minimize unplanned breaches in the glovebox, information on glovebox glove failures has been compiled from formal records. This research analyzed and interpreted this data by employing statistical methods. Statistical models were also developed to perform reliability analysis for glove failures. In this research, to utilize all available data including incomplete data, data censoring techniques are used in the statistical analysis.
Crack Growth Rates of Nickel Alloy Welds in a PWR Environment
Authors: Alexandreanu Bogdan , Chopra Omesh K. , Shack William J.
Published: July 2008

A program is being conducted at Argonne National Laboratory to evaluate the resistance of Ni alloys and their welds to environmentally assisted cracking in simulated LWR coolant environments. This paper presents crack growth rate (CGR) results for Alloy 182 shielded-metal-arc weld metal in a simulated pressurized water reactor (PWR) environment at 320°C. Crack growth tests were conducted on 1–T compact tension specimens with different weld orientations from both double-J and deep-groove welds. The results indicate little or no environmental enhancement of fatigue CGRs of Alloy 182 weld metal in the PWR environment. The fatigue CGRs of Alloy 182 in the PWR environment are a factor of ≈5 higher than those of Alloy 600 in air under the same loading conditions. The stress corrosion cracking CGRs for Alloy 182 are close to the average growth rates of Alloy 600 in the PWR environment. The results from the present study are compared with the existing CGR data for Ni-alloy welds to determine the relative susceptibility of the specific Ni-alloy weld to environmentally enhanced cracking.
Free Surface Flow Analysis by Smoothed Particle Hydrodynamics
Authors: Imasato Jun , Sakai Yuzuru
Published: July 2008

In this study a new computational algorithm to enforce incompressibility in free surface flow analysis using Smoothed Particle Hydrodynamics (SPH) is presented. The method uses two steps. The first step is a fractional step for solving velocity field forward in time without incompressibility. Then the second step is computed to compensate the pressure Poisson equation using the mass constant equation in a particle field. This method is composed of the above two steps and is similar to SMAC (Simplified Marker and Cell) method commonly used in CFD. However in SPH simulation, the introduction of incompressibility of fluid is easily realized using the particle density concept and the boundary of free surface of fluid is also controlled conveniently by the concept. In this study the algorithm is applied to sloshing problems of vessels with fluid. The numerical results using this algorithm show good results in the behaviors of free surface flow and the pressure evaluations at the wall of the vessels.
Large Deformation Analysis by Smoothed Particle Hydrodynamics
Authors: Kawashima Yoichi , Sakai Yuzuru , Yamagata Nobuki
Published: July 2008

Smoothed particle hydrodynamics (SPH)[1] is extended to the elastic-plastic large deformation analysis of metals and the hyper-elastic analysis of rubbers. The elastic-plastic analysis theory and the large deformation theory used in this study are fundamentally similar to those of FEM however the theories are applied at the particle points within a smoothing radius in SPH models. In this study the volume constant condition is imposed on the plastic deformation process using a pressure equation given by the particle density condition in a unit volume. Test problems show that the large deformation analysis by SPH leads to good stability and accuracy comparing with FEM results.
Elastic-Plastic and Frature Analysis of Mobile Phones Using SPH
Authors: Yamagata Nobuki , Sakai Yuzuru , Marcal Pedro
Published: July 2008

Smoothed Particle Hydrodynamics (SPH) was invented by Lucy[1], Monaghan and Gingold [2] for gas dynamics problems in astrophysics and extended to treat solid continua in this decade[3]]. The SPH technique uses no underlying grid — it is a pure Lagrangian particle method. The absence of a mesh and the calculation of interactions among particles based on their separation alone that large deformations can be computed without difficulty. It is for this reason that SPH has the potential to be a valuable computational tool. In this paper we have been using the SPH algorithm to compute the structural analysis of the mobile phones without mesh data. Using the visualization software MPAVE the particle distributions for the mobile phone could be easily produced in 3 dimensions and the elastic-plastic analysis and the fracture analysis have been performed effectively. The results show the possibility for practical use of a particle method to 3 dimensional structural analysis of the usual industrial products.
MOX Fuel Fabrication Glovebox Window Qualification Criteria
Authors: Brunsdon Bruce E. , O’Sullivan John J. , Shirani Oscar B. , Malagoli Guillaume
Published: July 2008

This paper discusses criteria developed to qualify glovebox windows to maintain confinement under normal, accident, and design basis natural phenomena conditions. Specialized qualification methods include equivalent panel and gasket modeling techniques, membrane stress evaluation methods, panel stress acceptance criteria, ligament efficiency applications at perforations, and gasket strain acceptance criteria.
Particle Swarm Optimization (PSO) Fuzzy Systems and NARMAX Approaches Trade-Off Applied to Thermal-Vacuum Chamber Identification
Authors: Araujo Ernesto , Freitas Ubiratan S. , Macau Elbert A. N. , Coelho Leandro S. , Aguirre Luis A.
Published: July 2008

Two nonlinear identification methods are employed in this paper in an experimental comparative approach to generate dynamical models for a thermal-vacuum system. Used for space environment emulation and satellite qualification, a thermal-vacuum chamber presents highly nonlinear and time-delay characteristics. While, in the first nonlinear identification approach, Particle Swarm Optimization (PSO) derive a Takagi-Sugeno fuzzy model, the second one was based on NARMAX polynomial identification technique. PSO is a stochastic global optimization technique that uses a population of particles, where the position and velocity of each particle represent a solution to the problem. It is employed as an auxiliary mechanism for finding out a T-S fuzzy model. The NARMAX polynomial identification technique uses a criterion called Error Reduction Ratio (ERR) computed by employing an orthogonal least squares method whose terms are selected in a forward-regression manner. Results indicate that both methods are feasible solutions for eliciting models from the available data.
Failure Behaviour of Notched Sheet Specimen Under Plane Strain Deformation
Authors: Duan Xinjian , Spencer Kevin , Jain Mukesh , Wilkinson David S.
Published: July 2008

The failure behaviour of notched AA5754 specimen subject to plane strain deformation is examined by the use of a heterogeneous finite element model. A ductile damage indicator triggered model is applied together with the use of element deletion technique for virtualization of fracture evolution. The predicted characteristics of the failure process under a wide range of triaxiality (0.33 to 2.5) fits well with those experimental observations in the literature.
Comparison of Acceptance Criteria for Ultrasonic Inspection of ASME CC 2235, Dutch Standard TO 98-54 and API RP 579
Authors: Gottselig Ken M.
Published: July 2008

This paper provides a comparison between the acceptance criteria for ultrasonic inspection for new pressure vessels using ASME Code Case 2235-3, Dutch Standard Report TO 98-54 on Time of Flight Diffraction (TOFD) and API RP 579 Fitness-for-Service. Two case studies using all three standards are performed for two recently constructed pressure vessels. The differences for all three standards are discussed and recommendations for standardization are made.
Non-Uniform Pressure Distribution in Draw-Bend Friction Test and a New Methodology to Determine Non-Constant Friction Coefficient From the Test
Authors: Kim Young Suk , Jain Mukesh K. , Metzger Don R.
Published: July 2008

Friction under lubricated conditions is known to depend on pressure, and experimental determination of this dependence has typically quantified pressure as an average value over the contact area. However, non-uniform pressure distributions at the contact interfaces of draw-bend tests have been reported from various experiments and simulations. A previous study by the authors has evaluated the current methodology, which assumes uniform pressure distribution to estimate friction coefficients from draw-bend friction tests, and has concluded that the current methodology is only valid for measuring an average friction coefficient over the pressure range, which exists in the specific draw-bend system. In this paper, a new methodology to extract non-constant friction coefficients from draw-bend friction tests is suggested. In the methodology, contact pressure maps obtained from simulations, instead of the uniform pressure assumption, are included in the analysis of test data to measure the pressure dependency of friction coefficient. The methodology is tested by applying the method to back predict the input friction data from finite element simulation results of draw-bend friction tests, in which non-constant friction models are used as friction input.
Some Comparisons and Potential Structural Integrity Methodology Transfer Between the Petroleum Industry and the Nuclear Power Industry
Authors: Server William , Craig Bruce
Published: July 2008

Many different large component industries develop structural integrity methodologies independently of each other even though the guiding principles of fracture mechanics and flaw tolerance concepts are followed. This paper presents a comparison of some key aspects of flaw tolerance approaches used in the petroleum and nuclear power industries. Differences in the types of components and structures are acknowledged as well as material degradation and failure mechanisms. Potential transfer of structural integrity technology for some aspects of the methodologies will be presented and discussed. The hope is that some cross-fertilization between the industries can be developed and maintained.
Guideline of Weld Overlay Repair Method for Primary Piping of Japanese Boiling Water Reactors
Authors: Fujimori Haruo , Hayashi Eisaku , Motora Yuichi , Ohata Hitoshi , Sakurai Hideo
Published: July 2008

A private guideline of a weld overlay (WOL) repair method for SCC cracked Boiling Water Rector (BWR) primary piping was provided by Thermal and Nuclear Power Engineering Society of Japan. In the WOL method, the overlaid structure of SCC resistant 308L weld metal substitutes for cracked existing piping weldments as pressure boundary. The guideline prescribes the applicability, welding conditions and essential variables, weld overlay structural design, evaluation of welding effects to the piping system, in-process control, post-process examination, and procedures of pre-service and in-service inspection.
A Study of Influence of Locally Reduced Thickness on Stress of Bottom Annular Plate of Oil Storage Tank During Uplifting by Seismic Loading
Authors: Yamaguchi Satoru , Ishida Kazuo , Ibata Takashi , Kawano Kazuma , Sekine Kazuyoshi , Maruyama Hiroaki
Published: July 2008

In 1978, Off-Miyagi Prefecture Earthquake in Japan caused damage to large oil storage tanks. Their annular plates had been greatly reduced in thickness due to local corrosion, and they were broken by uplifting due to the earthquake. In order to examine the stress tendency of annular plates with local metal loss during uplift by earthquakes, nonlinear static uplift analyses by three-dimensional shell FEM were carried out on a 110,000kl oil tank. The sizes of locally reduced parts, such as the circumferential and radial dimensions, were taken as the analytical parameters. Many useful results were obtained regarding the relationship between the range of local metal loss and the stress in annular plate. The “stress increase ratio” is defined in this study as the ratio of radial surface stress in an annular plate with metal loss to that without metal loss. The following results were obtained. As the radial width of metal loss part decreases, the annular plate radial stress increases. The stress increase ratio is 1.47 when the thickness of radial metal loss part of radial width 23mm is reduced to 18.4mm from an original thickness of 21mm. For a circumferential length of metal loss part of less than 2.1m that is calculated by multiplying the radius of tank with the tank central angle of three degrees, the stress increases proportionally to the length of metal loss part. On the other hand, when the length is more than 2.1m, the maximum stress has a tendency to saturate.
Industrial Application of Research Results of Packings on Safety Relevant Valves in Nuclear Power Plants
Authors: Koring Reinhard
Published: July 2008

In a NPP approximately 380 safety relevant valves are installed. The main requirements are the safety and operational availability as well as a adequate leak tightness of the sealings and stem packings. Based upon the research results of the MPA-Stuttgart, Germany on packing features specific procedures for handling, assembly and maintenance of packings and analytical inputs for the design calculation have been developed. Depending on the valve size, especially on the stem diameter, the packing influences the necessary stem force for the closing and opening function due to the amount of friction force. The complying equations of the valve calculation guideline were derived from the research results and rely on covering material characteristics of the approved packing rings such as friction coefficient and the vertical/horizontal force transfer factor of the stressing force. The industrial application often requires a more detailed calculation and handling of the actually installed packing configurations especially if existing valves are considered for redesign measures and recalculation. Therefore additionally mock-up tests of existing packing configurations have been performed in cooperation with the packing manufacturer in order to get very specific material coefficients as input data for the calculations. This paper presents the application of research results to design calculation of safety relevant valves as well as the development of procedures for the packing assembly and maintenance.
Extreme Value Analysis of Heat Exchanger Tube Inspection Data
Authors: Wang W. David
Published: July 2008

This paper presents a statistical extreme value analysis (EVA) method for assessment of the minimum remaining thickness of tubes in industrial heat exchangers, including air-cooled heat exchangers and shell-and-tube heat exchangers. Five test cases are used to evaluate the effectiveness of the EVA method developed in this work. In each case, real inspection data from heat exchangers in petroleum refinery and petrochemical plant are analyzed, and the results discussed. The effectiveness of the EVA method is then evaluated per the Inspection Effectiveness definition used by American Petroleum Institute (API) for Risk-Based Inspection (RBI), so that the EVA method and results can be easily incorporated in API RBI assessment. It is found through these test cases that the most ideal sample size seems to be 20–30 tubes, regardless of the number of tubes in the heat exchanger. At that sample size, A, B, C and D levels of API RBI inspection effectiveness can be achieved by using the lower bound value of the 99%, 95%, 90%, and 80% confidence intervals, respectively.
Helium Leak Test of a General Purpose Fissile Package (GPFP)
Authors: Trapp Donald J.
Published: July 2008

The General Purpose Fissile Package (GPFP) is a new package that is designed to safely ship radioactive contents on public highways. The package consists of a specially designed 35 gallon drum which holds a 6-inch diameter containment vessel, which in turn holds the radioactive material that is being transported. The containment vessel must be helium leak tested at fabrication and once per year to ensure it is “leaktight” per ANSI N14.5. To minimize potential leak points, the containment vessel design does not include a port to add helium during the leak test. SRNL designed a helium charging device that the leak test specialist seals inside the vessel and activates at the appropriate time during the leak test.
A Fast Method for Ratchetting Strain Prediction
Authors: Noban Mohammad , Jahed Hamid
Published: July 2008

A time efficient method for predicting ratchetting strain is proposed. By finding the ratchetting rate, at only a few cycles, the ratchetting strain of any cycle can be determined. It is shown that a trajectory of the origin of stress may be defined in the deviatoric stress space as the ratchetting progresses. The method for obtaining this trajectory from a standard uniaxial asymmetric cyclic loading is presented. At the beginning, this trajectory coincides with the initial stress origin and approaches the mean stress, displaying a power law relationship with the number of loading cycles. This path defines a moving frame of reference for stress tensor calculations. Ratchetting rates for different cyclic loading are calculated with the knowledge of this frame of reference and through utilizing a constitutive cyclic plasticity model which incorporates deviatoric stresses and back stresses that are measured with respect to this moving frame. The proposed model is used to predict ratchetting strain of 1070 steel under single step constant amplitude and multi-step loading. The method is also applied to non-proportional loading. Results obtained agree with the available experimental measurements.
Use of Fuel Assembly/Backfill Gas Effective Thermal Conductivity Models to Predict Basket and Fuel Cladding Temperatures Within a Rail Package During Normal Transport
Authors: Greiner Miles , Gangadharan Kishore Kumar , Gudipati Mithun
Published: July 2008

Two-dimensional finite element thermal simulations of a generic rail package designed to transport twenty-one spent PWR assemblies were performed for normal transport conditions. Effective thermal conductivity models were employed within the fuel assembly/backfill gas region. Those conductivity models were developed by other investigators assuming the basket wall temperature is uniform. They are typically used to predict the maximum fuel cladding temperature near the package center. The cladding temperature must not exceed specified limits during normal transport. This condition limits the number and heat generation rate of fuel assembles that can transported. The current work shows the support basket wall temperatures in the periphery of the package are highly non-uniform. Moreover the thermal resistance of those regions significantly affects the maximum fuel clad temperature near the package center. This brings the validity of the fuel/backfill gas thermal conductivity models into question. The non-uniform basket wall temperature profiles quantified in this work will be used in future numerical and experimental studies to develop new thermal models of the fuel assembly/backfill gas regions. This will be an iterative process, since the assembly/backfill model affects the predicted basket wall temperature profiles.
Developing Solutions to Regional Latin America’s Spent Fuel Needs: Supporting the IAEA Mission
Authors: Feldman Matthew R.
Published: July 2008

Several countries in regional Latin America, including Argentina, Brazil, Chile, Mexico, and Peru, have active nuclear programs. Most of these programs involve small research reactors typically used to create various isotopes for medical and research purposes. Until recently, the highly radioactive spent fuel from these reactors was transported to the United States when it was removed from the various reactor sites. The United States has decided to cease acceptance of these waste materials, thereby requiring these Latin American countries to develop their own methods for dealing with the highly radioactive materials. The International Atomic Energy Agency (IAEA), the arm of the United Nations (UN) that deals with all forms of radioactive materials from weapons inspections to nuclear reactor safety, has undertaken a leadership role in the development of regional Latin America’s spent fuel storage/disposal plan. Acting as an IAEA mission expert, the author of this paper has aided in the development of the teams responsible for the development of both a Type B transportation cask and a long-term storage cask for these materials. This paper will discuss the overall scope and current status of these projects as well as detail the involvement of the author in helping to develop the ability of the design team members to find viable solutions to this problem.
Study on Reliability of Nuclear Power Plant Piping Considering Defect Sizing Accuracy
Authors: Machida Hideo
Published: July 2008

This paper describes effects of a defect sizing accuracy on the reliability of a nuclear power plant (NPP) piping when “Rules on Fitness-for-Service (FSS)” is applied. The effect of defect sizing accuracy on failure probability of PLR piping of boiling water reactor (BWR), in which stress corrosion cracking (SCC) frequently observed, was evaluated in this study. The failure probabilities with parameters of defect sizing accuracy and safety factor considered in the crack stability assessment were evaluated using probabilistic fracture mechanics (PFM) analysis. As the results, the defect sizing accuracy has a much effect on leak probability and this effect cannot be covered by the safety factor taken in FFS. In order to maintain reliability of an NPP when FFS is applied, the defect sizing accuracy in non-destructive examinations have to be grasped beforehand, and it is necessary to take it into consideration in the crack growth and the crack stability assessments.
Overview of the JEA Code of Fracture Toughness Requirements for Nuclear Power Plant Components
Authors: Tomimatsu Minoru , Asada Seiji , Hirano Takashi , Kobayashi Hideo
Published: July 2008

The Japan Electric Association Code, JEAC 4206, “Method of Verification Tests of the Fracture Toughness for Nuclear Power Plant Components” was originally published in 1973 in order to prescribe test methods, fracture toughness requirements and acceptance standards for materials used in nuclear power plant components. The code was recently revised so as to incorporate a new method to evaluate the structural integrity of reactor vessels with upper shelf Charpy impact energy (USE) less than 68J, based on the results of the researches performed as national projects by the Japan Power Engineering and Inspection Corporation and so on. In this paper, some contents of the code, which are applicable for reactor vessels, such as J integral based integrity evaluation method for reactor vessels with low USE including predicting J resistance curves (J-R curves) by using USE and temperature, and methods to evaluate integrity against pressurized thermal shock events and to determine pressure temperature limits, are overviewed.
Fitness-for-Service Assessment for Steam Generator Tube Fretting at Darlington Nuclear Generating Station
Authors: Pagan Sandra , Mills Brian E. , Kozluk Michael J.
Published: July 2008

Ontario Power Generation (OPG) has developed and implemented a systematic managed process for steam generators at all of its facilities. One of the key requirements of this managed process is to have in place long range Steam Generator Life Cycle Management (SG LCM) plans for each of its reactor units. The primary goal of these plans is to maximize the value of the nuclear facility through safe and reliable steam generator operation over the expected life of the units. These SG LCM plans integrate and schedule all steam generator actions such as inspection, operation, maintenance, repairs, modifications, assessments, performance monitoring, research and development, and feedback. This paper provides an overview of how structural and leak-rate testing, being conducted by OPG, is being used to support fitness-for-service assessments for fretting degradation in the U-bend region of the recirculating steam generators at the Darlington Nuclear Generating Station.
Evaluation of Alternate Interpretations Regarding the Conditions for Exclusion of Thermal Bending Stresses in Simplified Elastic-Plastic Stress Analyses
Authors: Keating Robert B. , Vollmer Richard O.
Published: July 2008

The ASME Code permits the range of primary plus secondary stress to exceed the stress limit of 3Sm, provided that several key conditions are satisfied. These conditions are provided in Paragraph NB-3228.5, “Simplified Elastic-Plastic Analysis”. The first condition is that the range of primary plus secondary stress intensity, excluding thermal bending stresses, shall be less than 3Sm. The term “thermal bending” is not clearly defined in the Code and at least two Code Interpretations have been issued with differing viewpoints. The first interpretation is that only those stresses due to the radial through-wall temperature distribution may be excluded; the second is that all thermal bending stresses, including thermal discontinuity stresses, may be excluded. In order to investigate the suitability of these two interpretations, elastic-plastic analyses are conducted of a highly restrained sample geometry. First, the sample problem is evaluated using the ASME Code rules for simplified elastic-plastic analysis for thermal ratcheting and fatigue, as required by NB-3228.5. Subsequently, cyclic elastic-plastic finite element analyses are conducted to determine if the simplified analysis rules provide adequate protection with regard to thermal ratcheting and fatigue. These analyses are performed using both interpretations to determine if adequate designs can be achieved for the sample problem selected.
Applicability of Master Curve Method to Japanese Reactor Pressure Vessel Steels
Authors: Miura Naoki , Soneda Naoki , Arai Taku , Dohi Kenji
Published: July 2008

The Master Curve method has been proposed and recognized worldwide as an alternative approach to evaluate fracture toughness of reactor pressure vessel (RPV) steels in brittle-to-ductile transition temperature range. This method theoretically provides the confidence levels of fracture toughness in consideration of the statistical distribution, which is an inherent property of fracture toughness. In this study, a series of fracture toughness tests was conducted for typical Japanese RPV steels, SFVQ1A and SQV2A, to identify the effects of test temperature, specimen size, and loading rate, and the applicability of the Master Curve method was experimentally validated. The differences in test temperature and specimen size did not affect master curves. In contrast, increasing loading rate significantly shifted master curves to higher temperatures. The lower bound curve based on the master curve could conservatively envelop all of the experimental fracture toughness data. The present rule, in which the lower limit of fracture toughness is indirectly determined by Charpy impact test results, can be too conservative, while the application of the Master Curve method may significantly reduce the conservativity of the allowable level of fracture toughness.
Creep-Fatigue Life Assessment Under Multiaxial Strain State
Authors: Zhang Shengde , Sakane Masao , Itoh Takamoto
Published: July 2008

This paper studies the multiaxial creep-fatigue life for type 304 stainless steel at elevated temperature. Strain controlled biaxial tension-compression creep-fatigue tests were carried out using cruciform specimens under four strain waves at three principal strain ratios. The strain wave and the principal strain ratio had a significant effect on creep-fatigue life of the cruciform specimen. The creep-fatigue life ratio decreased as the principal strain ratio increased which indicates that larger creep damage occurred at larger principal strain ratio. The effects of the strain wave and principal strain ratio were discussed in relation to the observations of surface crack and void area density in the gage part of the specimen. Creep-fatigue lives were discussed in relation to the principal stress amplitude calculated by finite element analysis and creep-fatigue damage was evaluated by linear damage rule.
Residual Stress Assessment in Japanese FFS Code for Pressure Equipment, HPIS Z101
Authors: Takagi Yoshio , Konosu Shinji , Yatomi Masataka
Published: July 2008

The High Pressure Institute of Japan published the first edition of Fitness for Service Assessment Procedure in 2001, HPIS Z101. Z101 is currently being revised and updated including the addition of Level 2 Assessment which involves more detailed evaluation regarding the structural integrity of cracked pressure vessels or piping systems than Level 1 Assessment. One of the notable revisions of Level 1 and the additions in Level 2 are the weld residual stress assessment of welded components. In the Level 1 assessment, the simplified residual stress distribution was defined in the current version. After publishing the current version, the committee has made an additional investigation into the residual stress assessment in existing FFS codes such as R6 and API 579 and has also compared the data in the technical literature on residual stress. The existent FFS code contains a certain degree of safety in residual stress assessment by making conservative structural integrity assessments for cracked pressure vessels and piping to prevent unexpected failure. However, the definition of residual stress profiles on the surface is controversial. In addition, some simplified definitions in the FFS codes do not always evaluate the measured weld residual stress safely. In this paper, the contradictions and controversial issues regarding weld residual stress distributions are discussed. Furthermore, the draft of revised Z101 is explained.
Detailed Simulation of an Overlay Repair on a 14” Dissimilar Material Weld
Authors: Courtin Stephan , Gilles Philippe
Published: July 2008

In nuclear reactors, ferritic low alloy steel heavy section components are connected with austenitic stainless steel piping systems. Despite a special manufacturing procedure to ensure a good resistance of the joint, several experiences from the field confirm sensitivity to fatigue and corrosion in this type of junction. Overlay welding is a process widely used to mitigate dissimilar material weld (DMW) stress corrosion cracking by replacing inside tensile stresses by compressive stresses. Taking into account the costs generated by mock-up manufacturing, predictive Finite Element (FE) residual stress calculations are of great interest to prove the effectiveness of the overlay welding and to adjust the parameters of the process and particularly the overlay thickness. This paper presents residual stress computations performed by Framatome-ANP on a 14” pipe geometry, resembling many mid size DMW in the US. Considering 2D axisymmetric hypotheses, the analysis simulates each elementary step of the mock-up manufacturing procedure. In particular, the pass-by-pass welding simulation reproduces the deposit of each bead by thermo-metallurgical and mechanical calculations. Thanks to residual stress measurements carried out on 2 mock-ups (with/without overlay), the numerical approach has been validated and highlights the beneficial overlay effect. However, some discrepancies raise various problems: the backing ring modelling, the machining heating effect, the experimental scatter and the weld material hardening. The simulation being able to analyze the influence of an overlay layer going up to 1 time the original pipe thickness, further work on the stabilization of the residual stress fields obtained here after the deposit of 4 or 5 layers, may lead to a better adjustment of the overlay thickness and to a cut in the operation costs too.
Status of Repair Welding Guideline on Pressure Equipment in Japan
Authors: Yamamoto Eiichi , Hara Yasuhiro , Tahara Takayasu
Published: July 2008

Responding to the needs in petroleum and chemical industries, the Japan Welding Engineering Society has been working to collect repair welding cases and make technical data bases which will enable to optimum repair welding methods and procedures. The paper describes the purpose of the activity and its present status.
Fatigue of Stabilized SS and 316 NG Alloy in PWR Environment
Authors: Solin Jussi P.
Published: July 2008

Strain controlled constant and variable amplitude fatigue tests for 316NG and Titanium stabilized stainless steels in low oxygen PWR waters were performed. The stabilized steel has been plant aged for 100 000 hours. Constant amplitude test results at 0,01 Hz sinusoidal straining comply with predicted lives according to the Fen approach for both materials. Spectrum straining both in air and in environment caused predicted life reduction factors (about 3) for the stabilized steel, but for the 316NG steel spectrum straining in environment resulted to a larger reduction in life.
Thermo-Mechanical FE-Analysis of Heat Flow and Residual Stresses Distribution in Butt Welding
Authors: Kumaresan D. , Potti R. Krishnan , Muthu L.
Published: July 2008

In most of the Aerospace industries, welding play a vital role in joining process. Many of the structures presently built in space rockets, deep diving submarines and very heavy containment vessels for nuclear reactors could not have been constructed without the proper application of welding technology. It is well known fact that during welding the metal at the welding zone gets melted and then solidifies, which accompanies shrinkage in all directions. Residual strain and stress distributions coming from shrinking are largely influenced by the configuration of the welding process, metallurgical characteristics of weld and the geometrical shape of the welded joint. The material characteristics are mainly depends on the thermal history cycle through which the specimen undergoes. So these thermal history cycles have to be known in order to get a better knowledge of the phenomenon and to minimize the risks of failures. This work describes the detailed finite element simulation procedure for determination of heat flow pattern and residual stress for aluminium alloy during welding. In this Modified Double Ellipsoidal Distribution Pattern was modeled and considered for the weld pool design. Elasto-plastic material properties at various temperatures were also considered for the analysis. Transient thermal histories at various points were determined to obtain the cooling curve and cooling rate and compared with the theoretical values. From which metallurgical characteristic of the material at the weld zone and heat affected zone can be obtained during welding process. The problems of distortion and residual stress are also carried out. The transient stress and distortion plot were obtained from the FEM results. A customized programming was developed for the welding simulation.
A Review of Fatigue and SCC Crack Growth Rate Relationships for Ferritic and Stainless Steels and Ni-Cr-Fe Materials in BWR Environment
Authors: Mehta Hardayal S.
Published: July 2008

When in-service inspection of a nuclear plant component reveals the presence of cracking, an engineering evaluation (typically called a justification for continued operation, or JCO) is required to demonstrate the structural suitability for continued operation. A key element in such a flaw evaluation is the projected crack growth over the period when the cracked component will be reinspected. The crack growth is expected to be a combination of stress corrosion cracking (SCC) and corrosion fatigue. The ASME Section XI Code is in the process of developing a full range of SCC and corrosion fatigue crack growth rate relationships (CGRs) for stainless steel and Ni-Cr-Fe materials. The objective of this paper is to summarize several available SCC and fatigue crack growth rate relationships for these materials exposed to boiling water reactor (BWR) water environments. For completeness, low alloy steel SCC and corrosion fatigue CGRs in BWR water environment are also briefly reviewed. Two example evaluations are provided that used some of these CGRs in developing the JCOs for BWR components. A detailed comparison of these CGRs along with a review of the underlying data will be part of a future effort undertaken by the ASME Section XI Task Group.
The Effect of LWR Coolant Environments on the Fatigue Life of Reactor Materials
Authors: Chopra Omesh K. , Shack William J.
Published: July 2008

The existing fatigue strain–vs.–life (ε–N) data illustrate potentially significant effects of light water reactor (LWR) coolant environments on the fatigue resistance of pressure vessel and piping steels. This paper reviews the existing fatigue ε–N data for carbon and low–alloy steels and austenitic stainless steels in LWR coolant environments. The effects of key material, loading, and environmental parameters, such as steel type, strain amplitude, strain rate, temperature, dissolved oxygen level in water, flow rate, surface finish, and heat-to-heat variation, on the fatigue lives of these steels are summarized. An updated version of the ANL statistical models is presented for estimating the fatigue ε–N curves for these steels as a function of the material, loading, and environmental parameters. The Fen (environmental fatigue correction factor) approach for incorporating the effects of LWR coolant environments into the fatigue evaluations of the American Society of Mechanical Engineers Code is presented.
Bolt Bending Behaviour in a Bolted Flanged Pipe Joint: A Comparative Study
Authors: Abid Muhammad , Nash David H.
Published: July 2008

The joint strength of a bolted flanged pipe joint depends upon its proper assembly using a suitable level pre-loading leading to a static behavioral mode whilst in operation. This is opposed to a dynamic behavioral mode observed in the gasketed joint, where there is relative movement between components, resulting in subsequent joint relaxation, fatigue mechanism and potentially ultimately joint failure. The static behavioral mode present in non-gasketed joints however shows no joint relaxation, and hence effective sealing. This paper presents results of detailed comparative experimental studies of both gasketed and non-gasketed joint behavior during assembly, and highlights bolt bending and relaxation as the main factors effecting joint performance. In addition the importance of proper bolt tightening sequences, bolt tightening methodology and the influence of the number of passes to make a joint is also presented. For the case of the gasketed joint only, the influence of different types of gaskets in the joint and their effect is discussed since such factors can lead to joint relaxation.