bluuebunny/crossref_metadata_2025 huggingface dataset:
Research of Elastomeric Expansion for Tube-to-Tubesheet Joint
Authors: Hao J. W. , Pan H. L. , Tang S. H.
Published: July 2008

Just as hydraulic expansion, elastomeric expansion is an alternative method to produce tube-to-tubesheet joint with low residual stress level. However, the key parameters of the elastomer expansion are different from the hydraulic expansion. For elastomeric expansion, the problems lie in three aspects, (1) the expanding pressure (the radial pressure) applied to the surface of the tube is difficult to be measured directly; (2) the expanding length, which is decided by the final length of elastomer, is less than the original length of elastomer; (3) though grooving on the surface of the tubesheet hole can improve the strength of tube-to-tubesheet joint, the effect is depending on the location and width and number of the grooves. Therefore, in this paper, relationship of the axial pressure and the radial pressure, together with the relationship between the expanding length and original elastomer length and the width of groove, is investigated. It is discovered that the radial pressure is nearly equal to the axial pressure, so the radial pressure can be estimated by the axial pressure. Two equations are derived through this work. One can be used to obtain the suitable original length of elastomer, and the other is for calculating the width of groove.
Proposition of Helical Thread Modeling With Accurate Geometry and Finite Element Analysis
Authors: Fukuoka Toshimichi , Nomura Masataka , Morimoto Yuuya
Published: July 2008

Distinctive mechanical behavior of bolted joints is caused by the helical shape of thread geometry. Recently, a number of papers have been published to elucidate the strength or loosening phenomena of bolted joints using three-dimensional finite element analysis. In most cases, mesh generations of the bolted joints are implemented with the help of sophisticated software. The mesh patterns so obtained are, therefore, not necessarily adequate for analyzing the stress concentration and contact pressure distributions, which are the primary concerns when designing bolted joints. In this paper, an effective mesh generation scheme is proposed, which can provide a helical thread model with accurate geometry in order to analyze such important characteristics as stress concentrations and contact pressure distributions along the thread helix. Using the FE models with accurate thread geometry, it is shown how the thread root stress and contact pressure vary along the helix and nut loaded surface and how the chamfering of the top threads of the nut mitigate the stress concentration concerned.
R&D and Its Application to NPPs on Aging Management and Lifetime Assessment
Authors: Dou Yikang , He Yinbiao , Xu Xuelian , Xie Yongcheng
Published: July 2008

With more and more aged Nuclear Power Plants (NPPs) are still in operation in main nuclear industrial countries, aging and life management for operational NPPs becomes a worldwide concern. Many countries and international organizations, like IAEA, etc., have published a lot of regulatory requirements and guidelines to make the aging be well controlled by implementing effective aging management (AM) system in NPPs based on well understanding on aging mechanisms, assessment methodology and online monitoring technique. As a pioneering R&D institute in NPP design in China, Shanghai Nuclear Engineering research & Design Institute (SNERDI) initiated R&D on aging and life management for main components of NPP in the middle of 1990s, when Chinese first NPP, Qinshan-I (Q1), was very young. At present, China has a very ambitious NPP development plan in the following 15 years. Establishment of regulatory requirements and guidelines on aging management for operational NPPs gradually becomes an actual need, with more and more new NPPs being put into operation in the near future. This paper provides a schematic introduction on SNERDI’s strategic consideration and R&D activities on aging management and lifetime assessment. As an example of application of R&D to operational NPPs, PSR for Qinshan-I (Q1) is briefly introduced. Finally, the paper provides some points of view on establishment of Chinese aging management (AM) regulatory system.
2004 Edition of Japanese Fitness-for-Service Code for Nuclear Power Plants
Authors: Kashima Koichi , Nomura Tomonori , Koyama Koji
Published: July 2008

JSME (Japan Society of Mechanical Engineers) published the first edition of a FFS (Fitness-for-Service) Code for nuclear power plants in May 2000, which provided rules on flaw evaluation for Class 1 pressure vessels and piping, referring to the ASME Code Section XI. The second edition of the FFS Code was published in October 2002, to include rules on in-service inspection. Individual inspection rules were prescribed for specific structures, such as the Core Shroud and Shroud Support for BWR plants, in consideration of aging degradation by Stress Corrosion Cracking (SCC). Furthermore, JSME established the third edition of the FFS Code in December 2004, which was published in April 2005, and it included requirements on repair and replacement methods and extended the scope of specific inspection rules for structures other than the BWR Core Shroud and Shroud Support. Along with the efforts of the JSME on the development of the FFS Code, Nuclear and Industrial Safety Agency, the Japanese regulatory agency approved and endorsed the 2000 and 2002 editions of the FFS Code as the national rule, which has been in effect since October 2003. The endorsement for the 2004 edition of the FFS Code is now in the review process.
The Effect of the Thermal Expansion Coefficient on the Sealing Performance of Pipe Flange Connections With NiTi Shape Memory Alloy Gaskets
Authors: Takagi Yoshio , Tatsuoka Teruhisa , Sawa Toshiyuki
Published: July 2008

Due to the long-term durability and the excellent resistance to aging degradation, metal gaskets are expected to endure a longer life compared to conventional polymer gaskets. However, the nature of high elastic modulus of the metal reduces the sealing performance at interface. The authors have paid attention to the super elasticity of the shape memory alloys like Nickel-Titanium (Ni-Ti) alloy and evaluated its applicability to a gasket. In the process, leakage tests of the flange connections with Ni-Ti alloy gaskets were done and the sealing performance was evaluated with the new gasket constants and the tightness parameter proposed by PVRC (Pressure Vessel Research Council, ASME). The results revealed that Ni-Ti alloy gaskets showed a superior sealing performance to the conventional aluminum gasket. However, the thermal expansion coefficient of Ni-Ti alloy is smaller than that of stainless steel of which the flange is made. The increase in temperature of the flange like 20 °C to 40 °C accordingly induced a slight degradation of the sealing performance. In this paper, the effect of the change in temperature on the sealing performance of the pipe flange connections with Ni-Ti alloy gasket was numerically evaluated with the measured thermal expansion coefficient. Moreover, the effect of the clamped temperature on the sealing performance was evaluated taking into account the temperature dependence of the mechanical properties of Ni-Ti alloy.
Applicability of the Modified Rate Approach Method Under Various Conditions Simulating Actual Plant Conditions
Authors: Sakaguchi Katsumi , Nomura Yuichiro , Suzuki Shigeki , Kanasaki Hiroshi
Published: July 2008

The fatigue life in elevated temperature water is strongly affected by water chemistry, temperature and strain rate. The effects of these parameters on fatigue life reduction have been investigated experimentally. In transient condition in an actual plant, however, such parameters as temperature and strain rate are not constant. In order to evaluate fatigue damage in actual plant on the basis of experimental results under constant temperature and strain rate condition, the modified rate approach method was developed. As a part of the EFT (Environmental Fatigue Tests) project, the study was conducted in order to evaluate the applicability of the modified rate approach to the case where temperature and strain rate varied simultaneously. It was reported in the previous papers (1,2) that the accuracy of modified rate approach is about factor of 2. Various kinds of transient have to be taken into account of in actual plant fatigue evaluation, and stress cycle of several ranges of amplitude has to be considered in assessing damage from fatigue. Generally, cumulative usage factor is applied in this type of evaluation. In this study, in order to confirm applicability of modified rate approach method together with cumulative usage factor, tests were carried out by combining stress cycle blocks of different strain amplitude levels, in which temperature changes in response to strain change in a simulated PWR environment.
Simplified Limit Load Determination Using the Reference Two-Bar Structure
Authors: Seshadri R. , Adibi-Asl R.
Published: July 2008

Limit loads for mechanical components and structures are determined in this paper by invoking the concept of equivalence of “static indeterminacy” that relates a multidimensional pressure component configuration to a “reference two-bar structure.” Simple scaling relationships are developed that enable the rapid determination of limit load multipliers. The reference two-bar structure method is applied to a number of pressure component configurations with or without notches.
Integrity of Roller Expanded Tube-to-Tubesheet Joints With Over-Enlarged Tubesheet Holes
Authors: Shuaib A. N. , Merah N. , Ahmed M. , Al-Nassar Y. N. , Al-Anizi S. S.
Published: July 2008

This paper presents the results of an experimental investigation conducted to evaluate the effect of initial tube-tubesheet diametral clearance on the integrity of roller expanded tube-to-tubesheet joints in over enlarged tubesheet holes. The criteria of evaluating joint integrity include the pull out force and hydraulic tightness of the joints in which tubes were expanded to 5% wall reduction after metal to metal contact of the tube with the tubesheet hole. The levels of clearance investigated were selected to cover a range that exceeded by ten times that prescribed by the Tubular Exchangers Manufacturers Association (TEMA) standards [1]. The pull out test results showed that, within the investigated range of clearance, the joint strength has not declined below the strength of joints with clearance levels within the TEMA range. In fact the pull out force exhibited a slight linear increasing trend with the increase in initial clearance, which is attributed to the effect of tube strain hardening. The hydro test results indicated that all joints within the investigated clearance levels were hydraulically tight when they were tested at 1.5 times the design pressure of the heat exchanger for duration of 30 minutes. A relationship between rolling specific energy and initial joint clearance has been developed.
Enhancement of Surface Properties by Laser Peening Without Coating
Authors: Sano Yuji , Altenberger Igor , Scholtes Berthold , Masaki Kiyotaka , Ochi Yasuo , Akita Koichi
Published: July 2008

Laser peening without coating (LPwC) has been applied to water-immersed materials using a water-penetrable light of a Q-switched and frequency-doubled Nd:YAG laser. Compressive residual stress of several hundred MPa was introduced at the surface of the materials. High-cycle fatigue (HCF) properties were evaluated through rotating-bending or push-pull type testing for an austenitic stainless steel (SUS316L), a titanium alloy (Ti-6Al-4V) and a cast aluminum alloy (AC4CH). LPwC prolonged the fatigue lives significantly, in spite of the increase in surface roughness ascribed to the ablative interaction of laser pulses with the materials.
Fracture Toughness of Stainless Steel Cladding for Evaluation of the Degraded Davis-Besse RPV Head
Authors: Nanstad Randy K. , Sokolov Mikhail A.
Published: July 2008

Boric acid attack in the reactor pressure vessel (RPV) head of the Davis-Besse (D-B) nuclear plant led to wastage through the 150-mm low alloy steel head such that the stainless steel cladding was exposed. The Heavy-Section Steel Technology (HSST) Program at Oak Ridge National Laboratory was commissioned by the Nuclear Regulatory Commission to conduct a program of testing and analysis to enable an evaluation of the structural significance of cladding defects found in the wastage cavity of the D-B head. The overall test program consisted of material characterization at 316°C (600°F) of cladding materials, pressure vessel burst tests of cladding discs with and without flaws, and extensive analytical studies. Three different cladding materials were tested and evaluated, one from an unused commercial RPV that was used for the clad-burst experiments, an archival cladding previously used for various experimental and irradiation experiments, and the cladding from the D-B head. This paper compares and discusses the fracture toughness test results conducted with the three claddings, and the fractographic analyses conducted on the clad-burst discs. Comparison of J-resistance curves for the three clad materials shows significant material variability and disparity in the results from two test specimen types. Fractographic examinations of clad-burst discs showed transition from ductile tearing to shear mode of fracture. The relationship of the cladding test results with the clad-burst results is discussed.
Taking Advantage of Signal Processing Techniques for the Life Management of NPP Components
Authors: Chatellier L. , Dubost S. , Peisey F. , Richard B. , Fournier L. , Goussard Yves , Guichard Raphae¨l
Published: July 2008

The long term management of nuclear power plants raises several major issues among which the aging management of key components ranks high, from both technical and economic points of view. In order to detect and characterize potential defects on cast components, a program of in-service inspections is carried out by non-destructive testing (NDT) methods. In general, defect detection is the first step of an inspection procedure. Should a defect be detected, the plant operator must evaluate whether the component should be replaced or repaired (now or later) and will be required to prove that the component still meets regulatory requirements. That is why the characterization of the defect in terms of locating and sizing is essential, especially when the proof relies on mechanical calculations. In this paper we provide an overview of advanced signal processing techniques based on regularization of inverse problems. Those techniques have a strong potential for improving defect positioning and sizing. This has already been demonstrated in several R&D studies in the field of radiography and ultrasonics, leading in some cases to expertise-oriented applications. After a presentation of the general principles, we detail how regularization can be applied to process eddy current probe signals and provide good estimates of the depth of small surface breaking defects. Encouraging laboratory results have been obtained so far, which may lead to re-consider the scope of the eddy current technique as presently used in the nuclear industry. For example, its eligibility as an alternative NDE method could be explored in cases dealing with this kind of defect, if ultrasonics failed to meet the required characterization performance.
Environmental Fatigue Testing of Type 304L Stainless Steel U-Bends in Simulated PWR Primary Water
Authors: Hickling John , Kilian Renate , Spain Leslie , Carey John
Published: July 2008

Environmental fatigue testing of small-scale austenitic stainless steel components under simulated pressurized water reactor (PWR) operating conditions was sponsored by the EPRI Materials Reliability Program (MRP) Fatigue Issue Task Group and the U.S. Department of Energy to fill in some important gaps in the knowledge base. An analysis and assessment of existing fatigue data for stainless steel exposed to the PWR primary environment identified a lack of data with respect to flow rate effects. The majority of existing data has been gained under static or quasi-static flow conditions, where the tendency to environmental enhancement of cyclic crack growth is generally expected to increase. However plant experience — where high-flow conditions prevail — shows significantly lower susceptibility to corrosion fatigue cracking. The main objective of the present test program was the identification of flow-rate effects on the initiation and growth of low-cycle corrosion fatigue (LCF) cracks in cold-drawn, 304L stainless steel tube U-bend specimens undergoing cyclic loading and simultaneous exposure to simulated PWR primary water on the inside of the tube. Use was made of a pre-existing facility at F-ANP in Germany where the experimental concept had been previously tested on carbon-steel U-bends. The test equipment was set up so as to allow direct comparison of results obtained under quasi-stagnant conditions (∼0.005 m/s flow rate at the internal surface) with relatively high-flow conditions (∼ 2.2 m/s flow rate). In accordance with literature data, PWR primary water was shown to have a significant effect on the high-temperature fatigue behavior of the bends, as demonstrated by the observed change in failure mode and location of cracking between baseline specimens (tested in nitrogen) and those bends exposed to simulated reactor coolant. Metallography and fractography suggest that the environment is acting by affecting both crack initiation and crack growth. In contrast to the situation for carbon steel, no beneficial effect of higher flow rate on the number of cycles to failure (leakage) was observed. The paper discusses further details of the environmental fatigue data obtained, including the effects of strain amplitude, strain rate and surface condition. It also provides a comparison of test results with the current ASME Section III fatigue curves.
Transportable Laser Peening System for Field Applications to Improve Fatigue and SCC Resistance of Offshore Components and Structures
Authors: Hackel Lloyd A. , Dane C. Brent , Harris Fritz , Rankin Jon , Truong Chanh
Published: July 2008

Laser peening technology has matured into a fully qualified production process that is now in routine and reliable use for a range of aerospace alloys. The technology is capable of extending the fatigue life and stress corrosion cracking life of components, and will enable designers to consider higher stress levels in life limited designs. Applications under development for steels include high and medium strength steels used in off shore oil exploration and production, titanium, aluminum and even ceramics and plastics as well as life extension of steel and aluminum welds. Fixed systems to treat components and transportable systems capable of field operations are available with a moveable beam that allows peening directly as needed on large structures.
Mixed Oxide Fuel Fabrication Facility Design/Engineering Glovebox: Fire Protection Safety
Authors: Rosenbloom Lary J. , Berry Richard A.
Published: July 2008

Gloveboxes in a mixed oxide fuel fabrication facility provide primary confinement for the process systems handling nuclear material. The fire protection design must be coordinated with the confinement design while meeting criticality and life safety requirements. The fire protection strategy for the facility starts with specifying fire resistant systems, structures, and components with low fire loadings and design features that minimize ignition sources. The fire hazards, along with other process hazards, are specifically addressed during the design of nuclear process units. The industrial-scale process glove boxes in the MOX facility utilize polycarbonate as their window material, which was evaluated as being the most appropriate material in terms of constructability, operability, and confinement performance under mechanical loadings (e.g. shock, earthquake). The glovebox fire detectors are installed in accordance with the requirements of NFPA 72-1996 requirements and are an integral part of the facility fire detection system. Special design features to prevent a fire from starting, to divert potentially explosive material upon detection of a fire, and to reliably extinguish any incipient fires are incorporated into glovebox and process unit designs.
Fatigue Performance of Laser Peened 7050-T7451 Aluminum Alloy
Authors: DeWald Adrian T. , Luong Harold , VanDalen John E. , Hill Michael R.
Published: July 2008

Laser peening is an emerging technology for the surface treatment of metallic materials that is capable of enhancing resistance to fatigue failure. This paper presents results quantifying the effects of laser peening on residual stress and fatigue performance of samples machined from 7050-T7451 aluminum alloy. Residual stress distributions were measured for treatment with different laser peening parameter sets using the slitting method. For particular laser peening parameter sets, stress versus life data were generated over a range of applied loads and compared with as-machined and shot peened results. Two different sample types were used for fatigue testing: smooth bend bars and notched bend bars. In general, laser peening produced a fatigue life improvement of approximately 3 to 6 relative to as machined samples and 1.5 to 2 relative to shot peened samples over the range of stress levels tested.
Technical Basis for Proposed Revisions to ASME Code Case N-513 and Some Applications to Moderate Energy Piping
Authors: McGill Robert O. , Cofie Nathaniel G. , Cipolla Russell C. , DeBoo Guy
Published: July 2008

Code Case N-513 provides evaluation rules and criteria for temporary acceptance of flaws, including through-wall flaws, in moderate energy piping. The application of the Code Case is restricted to Class 2 and 3 systems, so that safety issues regarding short-term system operation are minimized. The first version of the Code Case was published in 2000. Since then, there have been two revisions to the Code Case (N-513-1 [1] and N-513-2 [2]) that have been published by ASME. There is currently work underway to incorporate additional changes to the Code Case to make it easier to apply to through-wall, nonplanar flaws. The technical basis for the original version of the Code Case and the first revision, N-513-1, has been previously published [3]. This paper provides the technical basis for the changes in the second revision of the Code Case, N-513-2, and the proposed changes to a third revision. These changes specifically address exceptions taken by the NRC in the first version of the Code Case and more importantly provide flaw evaluation rules for through-wall, nonplanar flaws. The flaw evaluation rules for through-wall, nonplanar flaws are based on ASME Code Section III branch reinforcement rules and also a quasi planar flaw approach. These developments are described in the paper. In addition, practical examples involving the application of the Code Case to through-wall, nonplanar flaws are also provided.
Computational Analyses of Instabilities and Transients in Valve and Piping Systems
Authors: Ahuja Vineet , Hosangadi Ashvin
Published: July 2008

Valve and piping systems in rocket propulsion systems and testing facilities are constantly subject to dynamic events resulting from the timing of valve motion leading to unsteady fluctuations in pressure and mass flow. Such events can also be accompanied by cavitation, resonance, system vibration leading to catastrophic failure. High-fidelity dynamic computational simulations of valve operation can yield important information of valve response to varying flow conditions. Prediction of transient behavior related to valve motion can serve as guidelines for valve scheduling, which is of crucial importance in engine operation and testing. Feed components operating in cryogenic regimes can also experience cavitation based instabilities leading to large scale shedding of vapor clouds and pressure oscillations. In this paper, we present simulations of the diverse unsteady phenomena related to valve and feed systems that include valve stall, valve timing studies as well as cavitation instabilities in components utilized in the test loop.
Net Section Plastic Collapse Analysis of Two-Layered Materials and Application to Weld Overlay Design
Authors: Deardorff Arthur F. , Cofie Nathaniel G. , Dijamco David G. , Chintapalli Aparna
Published: July 2008

The net section plastic collapse equations currently used for piping flaw evaluation in ASME Section XI, IWB-3600 are derived based on thin shell theory assuming properties for a single material. Because of the wide use of weld overlays to repair piping flaws in both BWRs and PWRs, there is a need to investigate the effect of multi-layered materials on the net section plastic collapse equations since weld overlays are typically applied with the weld material being different than the underlying base material. In addition, the larger section of the weld overlay provides additional load-carrying capability. A question also arises as to the application of appropriate loads and Z-factors if the underlying material is low-toughness material and the weld overlay has high toughness, not requiring consideration of thermal expansion stresses and Z-factors. The inherent assumptions that are made may lead to over-sizing of the overlay which can increase the welding time during the overlay implementation and subsequently the outage time. In this paper, an approach is developed for inclusion of thermal expansion loads and Z-factors for a weld overlaid circumferentially cracked section. Limit load equations are derived assuming a two layered material, both with and without taking advantage of the greater area and section modulus associated with the weld overlay. The equations for the allowable applied loads include consideration of both limited and complete circumferential flaw extent into the compressive zone of the section. The formulations are then applied to the design of weld overlays which are used to repair flawed piping. The evaluation shows that there can be significant difference in the allowable piping stresses as compared to those based on use of simplified uniform material assumptions.
Reconsideration of the Allowable Local Thickness of Straight Pipes in ASME CC N-597
Authors: Park Jai Hak , Shin Kyu In , Park Chi Yong , Lee Sung Ho , Kim Tae Ryong
Published: July 2008

It becomes a hot issue to assess the structural integrity of thin-walled pipes and pipe items. ASME Section XI Code Case N597-2 [1] provides a criterion for acceptance of the pipes. But the code has several limitations for application and sometimes gives too conservative or non-conservative results. So works are in progress to modify and extend the code. For that purpose it is necessary to understand fully the technical bases of the code. In this paper technical bases were explained and the equations in the code were derived for the allowable local thickness of straight pipes. In N-597 code, the allowable local thickness of a thinned straight pipe is given for three different methods. Because of the different technical base, each method gives different thickness values and sometimes gives contradictory values. So in this paper attempts were made in order to propose a unified rule for the allowable local thickness and in order to remove or relax the restrictions on the application of the code. For this purpose elastic stress analyses were made using the finite element method and the stress results were examined. Based on the obtained bending stress results, a very simple procedure was proposed to obtain the consistent allowable local thickness for the thinned straight pipes.
Evaluation of Sealing Behavior of Gaskets Based on the Test Method HPIS Z104 Proposed in Japan
Authors: Kobayashi Takashi , Sawa Toshiyuki , Tsuji Hirokazu , Shigetome Shoichi
Published: July 2008

This paper discusses the gasket testing procedure HPIS Z104 to obtain fundamental sealing behavior of gasket established in Japan. The testing procedure consists of 11 combinations of gasket stresses and a constant internal pressure. It takes about 3 hours to complete one test, which is acceptable for gasket manufacturers. In order to demonstrate the validity of the testing procedure, measurements of leak rates of compressed fiber sheet gaskets were carried out. It has shown that the fundamental sealing behavior can be well characterized using the proposed testing procedure with reasonable time and cost.
Introduction to the Department of Energy Mixed Oxide Fuel Fabrication Facility Design/Engineering
Authors: Choho Anne-Marie , Shipp James H. , Niemer Keyes , Sanchez Richard
Published: July 2008

This paper/presentation will serve as an overview of the Department of Energy (DOE) Mixed Oxide Fuel Fabrication Facility (MFFF) project including background, purpose and function of the MFFF, and an overview of the MFFF primary plant process systems.
Mechanical Properties of Fine-Grained Structures Using Computational Cell Elements
Authors: Park Y. H. , Arige V. , Tang J.
Published: July 2008

Mechanical properties of fine-grained microstructure are predicted using a phase mixture model. The constitutive model is implemented into commercial finite element analysis code ABAQUS as a UMAT subroutine. A unified constitutive model based on dislocation density evolution describes the matrix phase behavior. The yield criterion of the Gurson-Tvergaard-Needleman material model for porous materials is applied to the boundary phase. The boundary phase is assumed to behave like a quasi-amorphous material. The effect of the grain size on the material property is studied using a numerical example.
Development of a New Simple Protocol and Test Device for the Detection and Measurement of Elastomeric Seal Material By-Pass Leak
Authors: Fribourg D. , Morio Y. , Birembaut Y.
Published: July 2008

When leakage measurement on an elastomeric seal is performed with a tracer gas (helium), the measured global leak is the result of the combination of the two following phenomena: a) a phenomenon of gas permeation related to the solubility and diffusion of gas in and through the material, b) a phenomenon of by-pass or interfacial leakage related to the gas flow around the seal due to geometrical defaults at the interface (capillaries, cuts, seal and groove surface quality, etc).
Calandria Tube to Tubesheet Roller-Expanded Joint Qualification
Authors: Banwatt A. S. , Sauve´ R. G.
Published: July 2008

The complex calandria tube to calandria tubesheet roller-expanded joint in CANDU nuclear reactors is usually qualified by test. In this paper, a state-of-the-art numerical simulation is undertaken in order to improve the understanding of the behaviour of the joint to support design modifications and provide assurance that the test rig envelopes behaviour of the in-situ reactor assembly. Parameters such as hoop stress, and plastic deformation of the assembly are predicted. The analysis results are also compared with the available test data and in-situ experimental data. The analysis results show that the test performed to qualify the joint using a small plate and single joint is representative of the in-situ reactor configuration.
Comparison of Fatigue Damage Estimates Using the ASME Code and Other Methods
Authors: Chattopadhyay Som
Published: July 2008

Fatigue damage calculations have been performed in a specific design application using the method outlined in the ASME Code Section III as well as the local strain approach. For both methods, the finite element stress analysis results for a structural component subject to a specified set of transient loadings have been considered. The local strain approach is based on computing strain ranges from the elastic stresses using the material stress strain curve and Neuber’s rule. The allowable number of cycles is determined from the strain ranges and the continuous cycling fatigue curve for the material. A comparison of the fatigue damages predicted by the two methods demonstrates some of the conservatisms of the ASME Code procedure over the local strain approach. The sources of conservatism lie in the low cycle fatigue strain concentration factors and inherent safety factors in the design fatigue curves of the ASME Code. Some of the non-conservatisms in the ASME Code fatigue evaluation could primarily arise from the low cycle fatigue strain concentration factors for stress ranges in the vicinity of 3Sm for the material, a result based on experimental and finite element studies. We have also included an assessment approach based on a material distance parameter for the same problem.
Fracture Behavior of Finite Length Part Through Wall Flaws in Zirconium-Niobium Pressure Tubes
Authors: Metzger Don R. , Shek Gordon K. , Ho Ed T. C.
Published: July 2008

Flaws encountered in nuclear pressure tubes must be evaluated to ensure that a delayed hydride cracking (DHC) mechanism is not initiated where the stress concentration at a flaw tip causes diffusion of hydrogen and precipitation of zirconium hydride at the flaw tip. A fracture initiation model for DHC involves a process zone description for the interaction of hydride precipitation with the flaw tip stress distribution. Analytical techniques for this model are practical and accurate for two-dimensional geometry, but cannot be easily applied to the three-dimensional features of finite length surface flaws. Recently, a numerical rendition of the model has been incorporated into a finite element program so that arbitrary geometry and material properties can be managed. The three-dimensional finite length model is applied to specific flaw geometries used in an experimental program. Comparison with corresponding two-dimensional tests demonstrates that the finite length flaw has a significantly higher threshold load than that predicted on the basis of a two-dimensional model.
Overview of Computational Methods for Hydrogen Diffusion Coupled With Stress and Temperature Gradients in Zirconium Reactor Components
Authors: Metzger Don R. , Sauve´ Richard G. , Byrne Tom P.
Published: July 2008

In order to better understand and predict hydride blister formation and hydride cracking in zirconium alloy CANDU(1) fuel channels, specialized computational methods are required. Hydride blister formation involves the coupled action of gradients in temperature and hydrogen concentration, while hydride cracking involves coupling of stress and concentration gradients. Hydride accumulation and crack growth in a leaking crack involves a complete coupling of concentration, stress and temperature gradients. In all cases, the action of dissolution or precipitation of hydride adds complexity to the numerical analysis procedure. Dedicated finite difference and finite element programs have been developed and applied to blister formation and uniform temperature cracking problems. On the basis of experience gained in the use of such specialized codes, a fully coupled capability has been integrated into a general-purpose finite element program. This program can more realistically address complex load and temperature histories that may be encountered during fuel channel operation. An overview of important computational features is given along with applications relevant to current experimental research and fuel channel assessments. (1)CANDU is a registered trademark of Atomic Energy of Canada Limited.
Addressing the Monitoring and Transport of Radioactively Contaminated Scrap Metal: An International Approach
Authors: Pope Ronald B. , Kopsick Deborah , Chen Shih-Yew , Turner Ray , Magold Martin
Published: July 2008

The international metal processing industries are very concerned about the importation of scrap metal contaminated by radioactivity. Many of the problems are being identified while these materials, either unprocessed scrap, or processed materials, are being transported in the public domain. Because of this concern, the United Nations Economic Commission for Europe (UNECE), with the support of the United States Environmental Protection Agency (EPA) circulated a survey to various countries and interested groups. Following assessment of the survey, a meeting was convened in April 2004 to discuss and evaluate the issues. Three major issues were identified at the initial meeting. • First, an internationally acceptable scrap metal radiation monitoring and response protocol is needed. • Second, international training programs are needed to address multiple areas, almost all having emphasis on the transport mode; these include addressing such topics as protocol implementation, optimum location of monitors, acceptable detector sensitivities, calibration and maintenance needs, incident reporting, handling radioactive materials after detection. • Third, international information exchange within the scrap metal industry is needed to share data and experiences on contaminated scrap incidents, especially those occurring at international borders during the transport of these materials. The “open border” policy of the European Union makes the collection and dissemination of this information sharing particularly time critical. The paper reviews the results of the initial meeting, and elaborates on the efforts undertaken since that meeting.
Simulation Model for the Rod System Graphs Dynamics
Authors: Kholodov Yaroslav , Evseev Evgeny , Morozov Evgeny V. , Bapayev Azilkhan
Published: July 2008

The engineering structures composed from the rods (frames, trusses, etc.) are widely used in the various industrial applications. There are many publications presenting a theoretical modeling of the rod-based structural systems especially for the designs constructed from the thin-walled components. Usually, the single bar element of such system is taken as the basis for the general model development. The growth of the use of fast computer techniques has resulted in the extensive development of numerical methods where the main role belongs to the finite-element analysis. This paper presents a new approach to the numerical simulation and dynamic analysis of the rod systems based on the use of graphs in the numerical solutions for this class of problems. The main idea is that the solution of the global 3D problem for the whole system can be split into the number of simple one-dimensional problems for the individual elements (bars). Then, at each step of the numerical integration, these one-dimensional problems are linked with the common solution procedure for the original system using additional systems of equations written for the nodes (bar joints). In this way, the global coupling for all the original problem variables is guaranteed. Implementation of this method is illustrated in this paper for the flat two dimensional rod systems and incorporates finite-difference methods. The rod systems under consideration could be composed from an arbitrary number of the rectilinear bars/rods with different geometrical and physical characteristics. Also, the random topology of the bar joints and reactions in the system nodes can be realized. The advantage of the proposed approach is that not only dynamical behavior of the whole system, but also the transition nonstationary processes in the system components could be simulated for various combinations of the load applied and boundary conditions imposed.
Open Inspection Intervals of Boilers and Pressure Vessels for Chemical Plants in Japan
Authors: Ando Kotoji , Kitano Kazuharu
Published: July 2008

The open inspection intervals of boilers & pressure vessels for chemical plants in Japan is decided by the director of a bureau’s notification of Ministry of Public Welfare & Labor of Japan. The intervals are divided into three categories: 1) 12-month, 2) 24-month and 3) 48-month intervals. Basically, all boilers & pressure vessels for chemical plants shall be subjected to open inspection by every 12-month interval. However, specially authorized boilers & pressure vessels for chemical plants can be extended the open inspection interval from 12-month to 24-month or 48-month interval. The unit for authorization is a site of works. The numbers of accepted sites of works, boilers & pressure vessels for 24-month interval and 48-month interval at the time of 25th/Nov/2005 are as follow: *24-month open inspection interval — Sites of works: 177, Boilers: 1331, Pressure vessels: 10536; *48-month open inspection interval — Sites of works: 57, Boilers: 597, Pressure vessels: 4452. In this paper, the authorization system and the conditions are introduced concretely.
Electrochemical Testing of Gas Tungsten Arc Welded and Reduced Pressure Electron Beam Welded Alloy 22
Authors: Day S. Daniel , Wong Frank M. G. , Gordon Steven R. , Wong Lana L. , Rebak Raul B.
Published: July 2008

Alloy 22 (N06022) is the material selected for the fabrication of the outer shell of the nuclear waste containers for the Yucca Mountain high-level nuclear waste repository site. A key technical issue in the waste package program has been the integrity of the container weld joints. The currently selected welding process for fabricating and sealing the containers is the traditional gas tungsten arc welding (GTAW) or TIG method. An appealing faster alternative technique is reduced pressure electron beam (RPEB) welding. It was of interest to compare the corrosion properties of specimens prepared using both types of welding techniques. Standard electrochemical tests were carried on GTAW and RPEB welds as well as on base metal (non-welded) to determine their relative corrosion behavior in simulated concentrated water (SCW) at 90°C (alkaline), 1 M HCl at 60°C (acidic) and 1 M NaCl at 90°C (neutral) solutions. Results show that for all practical purposes, the three tested materials had the same electrochemical behavior in the three tested electrolytes.
Natural Convection/Radiation Heat Transfer Simulations of an Enclosed Array of Vertical Rods
Authors: Chalasani N. R. , Greiner Miles
Published: July 2008

Experiments performed by others measured the temperature of twelve heated vertical rods within a constant temperature, internally finned cylindrical enclosure. Measurements were performed for a range of air and helium pressures and a range of rod heat generation rates. In the current work, three-dimensional computational fluid dynamics simulations of natural convection and radiation heat transfer within this domain were conducted to benchmark the simulation techniques. These calculations accurately reproduced the local and average temperatures when the heat generation rate was sufficiently low that the velocity field is steady. Future simulations will be used to design experiments that model spent nuclear fuel within non-isothermal cells of storage packages.
Fire Durations of Concern for a Modern Legal Weight Truck Cask
Authors: Mallidi Neelima , Greiner Miles , Venigalla Venkata V. R.
Published: July 2008

The response of a truck package designed to transport four pressurized water reactor fuel assemblies to a simplified radiation fire model is simulated for a range of fire durations using three-dimensional finite element analysis. A model is developed to determine the cumulative seal degradation from its temperature versus time history. This model is used to determine the minimum fire duration that causes the seal to lose containment integrity. The fire durations that cause the maximum cladding temperature to reach its long term creep deformation and burst rupture temperatures are determined and found to be longer than the duration that cause the seal to lose containment integrity. These simulations are repeated for package models without the compliant regions of the impact limiters, and for a package with the impact limiter completely removed. These simulations quantify the level of thermal protection the impact limiters provide to the seals and cladding during simulated fires.
Large Deformation Analysis of Structures Enclosing Air Cavities
Authors: Bayoumi Hassan N.
Published: July 2008

In this paper, a method to analyze structures that enclose cavities filled with an ideal gas such as air is presented. The method has been implemented in a commercial nonlinear finite element program. The power of this method is in its simplicity and user friendliness. The change of pressure in the cavity resulting from the large deformation of the structure due to the application of external forces is automatically evaluated according to the ideal gas equations. The volume of the cavity is continuously updated and used to determine the changes in the cavity pressure. The method has been extended to model cavities partially filled with incompressible fluids and air. The method has also been successfully used in coupled thermal-stress problems. Several applications that use this method are presented. The applications range from simple problems used to validate the accuracy of the method against other techniques in the literature to real practical applications. Applications presented include fluid containers, airsprings and rubber seals.
Overview of the Japanese Code of Surveillance Test Program for Reactor Vessels
Authors: Tomimatsu Minoru , Asada Seiji , Ohata Hitoshi , Kobayashi Hideo
Published: July 2008

The Japan Electric Association Code, JEAC 4201, “Method of Surveillance Tests for Structural Materials of Nuclear Reactors” was originally published in 1970 so as to design a surveillance program for monitoring radiation induced changes in mechanical properties of beltline materials in light-water moderated nuclear power reactor vessels and to evaluate the test results. Recently in 2004 the code was revised, and a new method for predicting the decrease in upper shelf Charpy impact energy (USE) of beltline materials was incorporated based on the results of the research performed as a national project by the Japan Power Engineering and Inspection Corporation. Japanese surveillance tests program, including materials selections, type of specimens, number of capsules, withdrawal schedule, and evaluation of the results, is overviewed. Furthermore, methods for predicting the decrease in USE and reference temperature shift for beltline materials are also presented.
Design of Large Size High Pressure Raised Face Flanges to Meet ASME/ANSI B16.5 Standard
Authors: Ezekoye L. I. , Matty T. J.
Published: July 2008

ASME/ANSI B16.5 flange design provides the pressure-temperature ratings, materials, design dimensions, tolerances, and testing of pipe flanges in sizes 1/2 through 24 inches. For the most part, ASME/ANSI B16.5 is sufficient for many engineering applications requiring pipe flanges. However, there are instances where the pipe flange required is not covered by the ASME/ANSI Standard. This is particularly true when the flange rating is high, for example, Class 2500, and the flange size is greater than 12 inches. Developing a flange for these cases requires making some extrapolations of the ASME/ANSI design philosophy. In this paper, the process used to develop a Class 2500 14 inch Raised Face flange will be presented and which can be extended to other sizes and pressure classes.
Ultrasonic Measurement of Mechanical Properties of SA-516-70 Steel in Wet H2S Services
Authors: Wang W. David
Published: July 2008

Hydrogen-induced cracking (HIC) is a common problem occurring on pressure equipment made of SA-517-70 carbon steel in wet H2S services. The damage appears predominantly as blisters and laminar cracks, which may be linked in the through-wall direction to form stepwise cracking. The conventional approach used for crack inspection and fitness-for-assessment decision relies on finding and sizing the biggest through-wall crack. It does not work well for HIC assessment because there are usually too many cracks to be sized individually. Moreover, the through-wall links are often difficult to confirm by regular ultrasonic shear-wave techniques since the sound path may be blocked laminar cracks. This paper presents an alternative method using Crack Indication Density (CID) as the parameter to measure. This is a parameter can be easily extracted from ultrasonic C-scan data. Using empirical relations between CID and mechanical properties, one can then nondestructively determine the mechanical properties of the damaged steel and thus the integrity of the damaged equipment. The formula to calculate CID and examples of measured data are discussed in this paper.