bluuebunny/crossref_metadata_2025 huggingface dataset:
The Influence of Chemistry Concentration Uncertainty on the Probabilistic Fracture Mechanics Analysis
Authors: Chen Bo-Yi , Huang Chin-Cheng , Chou Hsuing-Wei , Liu Ru-Feng , Lin Hsien-Chou
Published: May 2012

The chemistry concentration uncertainty of cooper and nickel significantly affects the shift in reference nil-ductility transition temperature (ΔRTNDT). The uncertainty comes from the methods and equipments applied in measurements, the lack of specimen in surveillance capsule, and the non-homogeneous of material. The variations of ΔRTNDT result in the differences of failure probability of reactor pressure vessel. In this study, the structural integrity of Chinshan boiling water reactor RPV shell welds was evaluated by probabilistic fracture mechanics code-Fracture Analysis of Vessel – Oak Ridge (FAVOR). The influence of chemistry concentration uncertainty on the fracture probability of Chinshan nuclear power plant RPV with 32 and 64 effective full power years (EFPY) operation was discussed. The results of this work can be used to evaluate the structural integrity of the welds located at the RPV beltline region, and provide the aging assessment of reactor pressure vessel.
Research on the Tightness of the Hydraulically Expanded Tube-to-Tubesheet Joint
Authors: Li Xiang , Jia Guodong , Wang Hui , Ma Xin
Published: May 2012

Many investigations and practical experience show that the leakage failure of the tube-to-tubesheet joints is a common failure mechanism for the shell and tube heat exchangers. To systematically research the tightness of the hydraulically expanded tube-to-tubesheet joints, a three-dimensional finite element model was developed to consider the influence of such factors as the hydraulic expansion pressure, operating temperature and multi-tubes expansion. on the residual contact pressure between the tube and tubesheet-hole of the joints. The analytical results show that the hydraulic expansion can improve the tightness of the joints significantly. The leakage pressure of the joint first increases and then decreases with the increase of the expansion pressure, thus, an optimal expansion pressure exists. The leakage pressure improves at the beginning and lowers gradually with an increase in the temperature. The tightness of the joint is reduced very little after the temperature cycle. The optimized expansion pressures are quite different between the single-tube expansion model and multi-tube expansion model. Thus, the influence of expanded tubes on the expanding tube should be taken into consideration in the research of the tightness of the joints.
Comparison of Plastic Loads for Elbows With Experimental Data
Authors: Han Jae-Jun , Lee Kuk-Hee , Kim Yun-Jae , Budden Peter J. , Jin Tae-Eun
Published: May 2012

Finding plastic (limit) loads for elbows under various loading conditions such as in-plane bending and out-of-plane bending is not an easy task due to complexities involved in plastic analyses. Considering complexities involved in plastic limit analysis of elbow, deriving analytical solutions of plastic loads for elbows would be extremely difficult. So, recently the limit analysis using finite element program has been widely adopted. Based on extensive and systematic FE limit analyses using elastic-perfectly plastic materials, closed-form solutions of plastic loads for defect-free elbows under in-plane closing, in-plane opening and out-of-plane bending were presented. This paper summarizes the well-known criteria for finding plastic (limit) loads proposed by ASME BPVC Sec.III [1], Zahoor [4], Chattopadhyay et al. [17] and Kim et al. [19] The purpose of this paper is to integrate and improve the proposed solutions by Kim et al. Also, comparison results with published experimental data are presented. From these results, the pros and cons of each criterion for finding plastic (limit) loads for elbows are discussed.
FEM Calculation and Evaluation of Sealing Performance in Oil Pan Wavy-Shaped Flange Gasketed Connections
Authors: Kurosawa Ryou , Tenma Kentaro , Sawa Toshiyuki
Published: May 2012

The oil pan wavy-shaped flange connection, while is a type of the box-shaped flange connections, has been used for the oil-pan in the vehicles such as cars and motorcycles to seal inner fluid. Though the light weight of these connections is important, the design method has not been established, since no research for evaluating the sealing performance of the wavy-shaped flange connections has been conducted. In this paper, The contact gasket stress distribution in a oil pan wavy-shaped flange connection under the internal pressure is examined taking into account a gasket hysteresis using finite element method (FEM) for estimating a location where a principal leakage occurs and for calculating the amount of leakage. Leakage tests were also conducted to validate the estimated results using an actual connection under internal pressure. The effects of flange shape and difference in types of inner fluid (gas / liquid) are examined on the contact gasket stress distributions and the sealing performance in the connections. It is found that the estimated amount of leakage is in a fairly good agreement with the measured results. Furthermore, discussion on the effect of the bolt spacing and the gasket width on the sealing performance are made.
New Analytical Approach to Predict Creep Void Growth in Heat-Affected Zone of High Cr Steel Weldments
Authors: Murakami Eiji , Iwamoto Takeshi , Sawa Toshiyuki
Published: May 2012

This paper proposes a new analytical approach to predict creep void growth and remaining creep lifetime in a heat-affected zone (HAZ) of high Cr steel weldments. Concept of the new approach is based on a relationship between creep void growth rate and a parameter to represent multi-axial stress state obtained by finite element analysis. In this study, creep tests of ASME grade 91 (9Cr-1Mo-Nb-V) and grade 122 (11Cr-2W-0.4Mo-Cu-Nb-V) tubes with longitudinal weldments subjected to various internal pressures have been conducted to reveal creep void growth behavior in HAZ. Some specimens were intentionally interrupted before leakage at a damage level from 40 to 70% for clarification of void growth behavior at intermediate damage level. In addition, finite element creep analyses of the specimens at different creep strain rates in base metal, weld metal and HAZ have been carried out to investigate distribution of stress and stress triaxiality factor in HAZ. A comparison between stress distributions and void distributions revealed that stress triaxiality factor predominantly affects growth behavior of creep voids. From the result, the relationship between creep void growth rates and the parameter as a function of principal stress and triaxiality factor was established. Based on the relationship, a new prediction method was proposed. To verify proposed approach, the new method was applied to the elbow pipe with longitudinal weldment. As a result, predicted creep void growth in HAZ showed a good agreement with the results from diffusion simulation reported by literature. Therefore, the results demonstrated that the proposed approach is applicable to predict void distribution and remaining creep lifetime in the HAZ of high Cr steel weldments.
Extremely Low Probability of Rupture (xLPR) Version 1.0 Code: Pilot Study Problem Results
Authors: Rudland D. , Harrington C.
Published: May 2012

Nuclear Regulatory Commission (NRC) Standard Review Plan (SRP) 3.6.3 describes Leak-Before-Break (LBB) assessment procedures that can be used to demonstrate compliance with the 10CFR50 Appendix A, GDC-4 requirement that primary system pressure piping exhibit an extremely low probability of rupture. SRP 3.6.3 does not allow for assessment of piping systems with active degradation mechanisms, such as Primary Water Stress Corrosion Cracking (PWSCC) which is currently occurring in systems that have been granted LBB approvals. Along with a series of existing qualitative steps to assure safety in LBB-approved lines experiencing PWSCC, NRC staff, working cooperatively with the nuclear industry through a memorandum of understanding with the Electric Power Research Institute, is developing a new, modular based, comprehensive piping system assessment methodology to directly demonstrate compliance with the regulations. This project, called xLPR (eXtremely Low Probability of Rupture), will model the effects and uncertainties of relevant active degradation mechanisms and the associated mitigation activities. The resulting analytical tool will be comprehensive, vetted with respect to the technical bases of models and inputs, flexible enough to permit analysis of a variety of in-service situations and adaptable such as to accommodate evolving and improving knowledge. A multi-year project has begun that will first focus on the development of a viable method and approach to address the effects of PWSCC as well as define the requirements necessary for a modular-based assessment tool. To meet this goal, the first version of this code has been developed as part of a pilot study, which leverages existing fracture mechanics based models and software coupled to both a commercial and an open source code framework to determine the framework and architecture requirements appropriate for building a modular-based code with this complexity. The pilot study focused on PWSCC in pressurizer surge nozzles, and is meant to demonstrate the feasibility of this code and approach and not to determine the absolute values of the probability of rupture. Later development phases will broaden the scope of xLPR to appropriate primary piping systems in pressurized and boiling water reactors (PWR and BWR), using an incremental approach that incorporates the design requirements and lessons learned from previous iterations. This paper specifically examines the xLPR Version 1.0 model, the methods and approach used to couple the deterministic modules within a probabilistic software framework, and the results from the pilot study. A comparison of the results specific to the surge nozzle sample problem is presented. This paper concludes with lessons learned from the pilot study.
Overview of RPV Sub-Project of Perform 60
Authors: Lidbury David , Keim Elisabeth , Marini Bernard , Malerba Lorenzo , Zeghadi Asmahana , Moinereau Dominique , Al Mazouzi Abderrahim
Published: May 2012

PERFORM 60 (Prediction of the effects of radiation for reactor pressure vessel and in-core materials using multi-scale modelling — 60 years foreseen plant lifetime) is a 48-month project of the 7th Framework of the European Atomic Energy Community (EURATOM) being carried out under the auspices of the Directorate General Research, Technology and Development (DG.RTD) of the European Commission. Launched in March 2009, and building on the achievements of PERFECT, a EURATOM 6th Framework project, PERFORM 60 has as its main objective the development of multi-scale modelling tools integrated onto a common software platform, aimed at predicting for PWRs (i) the effects of irradiation on RPV materials (low alloy bainitic steels), (ii) the combined effects of irradiation and corrosion on internals (austenitic stainless steels). Accordingly, PERFORM 60 is based on two main technical sub-projects: SP1 (RPV) and SP2 (Internals). An integration work package within both SP1 and SP2 serves to facilitate software development. A Users’ Group (SP3) supports the main technical sub-projects and allows representatives of constructors, utilities, regulators and research organizations from Europe and further afield to receive the information and training needed to make their own appraisal as to the validity of the developed tools. A significant effort is also being made to train young researchers in the field of physical modelling of materials degradation due to neutron irradiation. Against this background, the paper provides an overview of SP1, highlighting the various models and methods being developed, building on the achievements of PERFECT, to describe the evolution of flow properties of low-alloy steels with irradiation and address their subsequent effects on cleavage fracture behaviour.
Simulation of Low-Reynolds Number Flow Around an Oscillated Cylinder Using Two Computational Methods
Authors: Baranyi La´szlo´ , Bollo´ Betti , Daro´czy La´szlo´
Published: May 2012

The two-dimensional flow around a circular cylinder oscillated in-line and transverse to the main stream at low Reynolds numbers is investigated numerically using a 2D in-house code (Baranyi, 2008) based on a finite difference solution (FDM). A second CFD approach, the commercial software FLUENT based on the finite volume method (FVM), uses equivalent oscillatory flow to perform computations for the same conditions. Here we investigate the Reynolds numbers of Re=100, 120, 140 and 160 using two computational domains characterized by R2/R1 = 60 and 360. Computations are carried out at two frequency ratios of f/St0 = 0.8 and 0.9 for different oscillation amplitude values in the lock-in domain. Both methods analyze flow properties such as drag, lift and mechanical energy transfer between the fluid and the cylinder for both transverse and in-line cylinder motions. Computational results obtained using the two methods for both type of cylinder motions agree well.
Diagnostics of Thermal Cycle Based on Residuals Between Actual and Expected States
Authors: Pliska Jiri , Londynova Katerina , Machat Zdenek , Sury Petr , Havlat Ladislav , Horky Vladimir
Published: May 2012

The economical operation of any nuclear power plant requires an accurate, consistent and permanent supervision of process states and health of major equipments that means performance monitoring, analysis, diagnostics, and optimization. The performance of nuclear power plant depends on many parameters. Any even the smallest improvement leads to a significant energy saving. The actual world tendency cares for all parameters which can enable economical work of nuclear power plant. There is a wide range of problems connected with measurement inaccuracies caused by stochastic and systematic errors and with calculating expected power and efficiency of nuclear power plant. An actual state can be determined by measurement data reconciliation. Data reconciliation serves for getting consistent set of process variables by eliminating random measurement errors. It enables detection of gross errors and thus an early detection of sensor degradations. An expected state can be predicted by a process simulation model. The simulation model is used for detailed calculation of expected or desirable performance of thermal cycle and its major equipments at varying ambient conditions and different steady-state operation modes. Outputs of data reconciliation and process simulation are then used to determine residuals between actual and expected performance of thermal cycle and its equipments thus providing performance engineers and operators (in near-real time) with information about the condition of thermal cycle and major equipments. Processing of residuals enables an early detection of equipment degradations, incorrect adjustment of the process parameters or sensor drifts or failures. It helps to improve operation and predictive maintenance and so reduce plant operation and maintenance costs. Comparison between actual and expected states is based on assumption that it is possible to have a process measurement which is precise but not accurate. Process optimization is a determination of setpoints for nuclear power plant operation or/and flow-sheet structure changes to obtain the maximum of power output and/or thermal efficiency or the maximum/minimum of the other optimization criterion under defined constraints. Some examples are taken from VVER 440 type of nuclear power plant.
Application of a New Carcass Design for Prevention of Singing Behaviour in Flexible Risers
Authors: Belfroid S. P. C. , Korst H. J. C. , Nielsen K. G. , Bendiksen E.
Published: May 2012

The flow of fluid over the inner surface of rough bore flexible pipes may create vortex induced pulsations. For gas risers these pulsations can in some cases be the source of a high amplitude tonal sound. This phenomenon is in the industry referred to as “singing risers”. Under certain circumstances these pulsations can result in large structural vibrations with potential fatigue failure of the connected topside or subsea pipe systems. The singing behavior is dependent on the operating conditions such as product density and viscosity as well as the piping layout of the topside and subsea piping. However, the most important factor is the geometry of the corrugations. In traditional designs the carcass is made from a folded metallic strip. NKT Flexibles has developed a novel approach to carcass manufacturing originally intended for deep and ultra deepwater applications, wherein the carcass is made of helically wound wires rather than a folded strip. Although the main focus for this development was to devise a carcass of superior collapse strength compared to conventional systems, the new carcass design provides a very smooth inner surface, thus mitigating vortex formation which will reduce or eliminate the formation of flow induced pulsations. The susceptibility to singing of the new carcass design is compared to that of a traditional carcass design. This includes the onset of the singing and the flow pressure drop. Due to the much smaller cavities in the new design, the singing tendency is shown to be significantly reduced. In particular, the expected onset velocity is 5–9 times that of a classic rough bore design with 20%–50% of the amplitude. An additional benefit of the new design is that the pressure drop for the pipe is close to that of a smooth bore pipe. Therefore, it is expected that for many applications, the new design will not lead to the generation of high amplitude tonal noise within the desired operating envelope.
Several Failure Analysis Cases of Pressure Equipment Under the Conditions of Complex Medium Environment
Authors: Chen Xuedong , Ai Zhibin , Yang Tiecheng , Fan Zhichao , Guan Weihe
Published: May 2012

There are several hundred of failure cases of pressure vessels and piping in China every year. The causes for part of accidents have been clearly analyzed, and preventive measures have been taken making the similar accidents substantially reduced, but the causes for quite a few failure accidents are still not found effectively, the similar accidents is still taking place. Through study, the authors find that the major reason for deviation of failure analysis lies in that equipments are mostly operating in complex medium environment, and mutual competition may exist among multiple failure mechanisms. Sometimes changes of some influential factors may cause the dominant failure mechanism change, even leads to totally different analysis conclusions. Combining with the analysis and verification of several failure cases of pressure vessels and piping in petrochemical enterprises, the judgment method for the dominant failure mechanism under multiple failure mechanisms is discussed in this paper, which may be helpful to provide some effective means for failure prevention of pressure equipment under complex environment.
NRC/EPRI Welding Residual Stress Validation Program: Phase III Details and Findings
Authors: Fredette Lee F. , Kerr Matthew , Rathbun Howard J. , Broussard John E.
Published: May 2012

The US Nuclear Regulatory Commission (NRC) and the Electric Power Research Institute (EPRI) are working cooperatively under a memorandum of understanding to validate welding residual stress predictions in pressurized water reactor primary cooling loop components containing dissimilar metal (DM) welds. These stresses are of interest as DM welds in pressurized water reactors are susceptible to primary water stress corrosion cracking (PWSCC) and tensile weld residual stresses are one of the primary drivers of this stress corrosion cracking mechanism. The NRC/EPRI welding residual stress (WRS) program currently consists of four phases, with each phase increasing in complexity from lab size specimens to component mock-ups and ex-plant material. This paper discusses Phase III of the WRS characterization program, comparing measured and predicted weld residual stresses profiles through the dissimilar metal weld region of pressurizer safety and relief nozzles removed from a cancelled plant in the United States. The DM weld had already been completed on all of the plant nozzles before use in the mock-up program. One of the nozzles was completed with the application of the stainless steel safe-end weld to a section of stainless steel pipe. Measurements were taken on the nozzles with and without the welded pipe section. Several independent finite element analysis predictions were made of the stress state in the DM weld. This paper compares the predicted stresses to those found by through-thickness measurement techniques (Deep Hole Drilling and Contour Method). Comparisons of analysis results with experimental data will allow the NRC staff to develop unbiased measures of uncertainties in weld residual stress predictions with the goal of developing assurances that the analysis predictions are defensible through the blind validation provided using well controlled mock-ups and ex-plant material in this program.
SCC Behavior of Alloy 690 HAZ in a PWR Environment
Authors: Alexandreanu Bogdan , Chen Yiren , Natesan Ken , Shack Bill
Published: May 2012

The objective of this work is to determine the cyclic and stress corrosion cracking (SCC) crack growth rates (CGRs) in a simulated PWR water environment for Alloy 690 heat affected zone (HAZ). In order to meet the objective, an Alloy 152 J-weld was produced on a piece of Alloy 690 tubing, and the test specimens were aligned with the HAZ. The environmental enhancement of cyclic CGRs for Alloy 690 HAZ was comparable to that measured for the same alloy in the as-received condition. The two Alloy 690 HAZ samples tested exhibited maximum SCC CGR rates of 10−11 m/s in the simulated PWR environment at 320°C, however, on average, these rates are similar or only slightly higher than those for the as-received alloy.
2010 Edition of B31.3 Process Piping Code: New Allowables for Appendix P—Alternative Stress Range Rules
Authors: Edwards Don R.
Published: May 2012

Appendix P Alternative Rules for Stress Range Evaluation was first introduced into the 2004 edition of ASME B31.3 Process Piping Code [1] as an alternative method that was conceived to be more computer friendly and possibly a more nearly theoretically defensible method of protecting piping systems individually against fatigue failure and dimensional ratchet than the singular stress range requirements of the Code’s base text (“base Code”). This paper describes the progression of events that led up to the inception of the Appendix and the subsequent revisions to same and detailing the reason for the 2010’s newly coined Allowable Operating Stress to protect against dimensional ratchet and Allowable Operating Stress Range to protect against fatigue failure.
Tube Arrays Flow-Induced Vibrations Simulations With ALE Finite Element Method
Authors: E´tienne Ste´phane , Pelletier Dominique
Published: May 2012

Fluidelastic instabilities in tube bundles subject to cross-flow are a major concern for the design of steam generators. We determine the fluidelastic instability boundary in the plane of the pitch reduced velocity and mass-damping parameter through unsteady simulations for low values of the Reynolds number. Simulations are performed with a finite element method.The time integrator is a 3rd order implicit Runge-Kutta scheme for both the flow and structural parts. The numerical method satisfies the Geometric Conservation Law. The variation of the pitch reduced velocity is performed by varying the rigidity of springs that support cylinders. Results show that in-line as well as cross-flow vibrations predominate when the reduced velocity is varied.
An Integrated Approach to Piping System Assessment: Incorporating ASME Code Standards Into NDE Inspection Techniques of Safety Related Piping at Wolf Creek Generating Station
Authors: Houston Eric , Walter Matthew , Rach Ken
Published: May 2012

This paper presents an overview of an integrated approach to piping system assessment. This project specific example directly assesses the condition of a large portion of the above ground Essential Service Water (ESW) at Wolf Creek Generating Station (WCGS). Prior to inspections, it is important to define acceptance criteria. In this example, multiple levels of screening were developed with varying acceptance criteria and required actions for acceptance. Inspections were conducted using multiple state of the art techniques, including Guided Wave Technology (GWT) and linear phased array (LPA). Screening levels were based on the original plant Code of Construction, as well as an NRC accepted ASME Code Case. The screening levels were developed in accordance with the inspection capabilities and limitations of each technology. This paper presents an overview of the process, the analysis that was conducted, the subsequent inspections, and general conclusions about the state of the system under investigation. The advantages and limitations of this integrated approach to piping system assessment are also discussed.
Mechanical Properties of New Hybrid Materials: Metallic Foam Filled With Syntactic Foam
Authors: Madawela Raghvan , Ouyang Zhenyu , Ji Gefu , Li Guoqiang , Ibekwe Samuel
Published: May 2012

Syntactic polymer foam has received intensive attention and extensive application due to its remarkable low cost, lightweight, mechanical properties as well as its thermal, acoustic properties for multifunctional purpose. Electrically conductive polymers have the advantages of light weight, resistance to corrosion, good processability, and tunable conductivity. In a recent separated study, we proposed a novel conductive polymer which was based on the metallic foam filled with syntactic polymer foam. In this study, instead of focusing its unique multi-physical properties, we focus on characterizing the mechanical properties of this new conductive syntactic foam. Before the exploration of this new hybrid foam, an understanding of the mechanical properties is quite necessary. To this end, hybrid foams were prepared by varying the volume fractions of microballoons in the syntactic foam and types of microballoon materials: glass and polymer microballoons. The metallic foam adopted in this work was based on aluminum with an average relative density of 7% (the porosity is about 93%). Both compressive and bending tests were conducted. The current test results may provide the valuable baseline and also facilitate the further understanding of this hybrid foams as a core material in the advanced sandwiched pipe/pressure vessel structures featured by lightweight, impact tolerant, self-monitoring, thermal and acoustic insulation, and electromagnetic shielding.
Influence of Testing Environment and Radius of Die Shoulder on SP Creep Rupture Life
Authors: Kobayashi Ken-ichi , Kaneko Masahiro , Koyama Hideo , Stratford Gavin C. , Tabuchi Masaaki
Published: May 2012

Small Punch, hereinafter designated as SP, creep test has been proposed as a semi destructive testing methodology to examine the residual creep life of high temperature components. Employing low alloy steel, a series of SP creep tests were conducted on disc specimens at 600°C in air and in high vacuum to investigate the influence of oxide scale on the creep rupture life. Thickness of the oxide scale on disc specimens in air increased with the test duration, e.g., about 30μm in thickness after 400 hours. The creep rupture life in air reduced to a half of the life in vacuum due to an increase in the actual stress in the disc thickness. In addition, the magnitude of radius of a lower die shoulder affected the SP creep rupture life. The influence of this radius on the SP creep life was also studied experimentally and numerically. The creep rupture life with the die radius of 0.5mm had twice longer than that with 0.6mm. This fact was also demonstrated by the FE analysis.
Development of S-N Curves for Some Pressure Vessel Steels
Authors: Chattopadhyay Somnath
Published: May 2012

In this paper the stress range versus the number of cycles to failure (S-N) curves has been developed for steels used in the pressure vessel and construction industries. These include SA 533 Grade B and C36 Steel. The method used to obtain the S-N curves involves a material parameter based on fatigue crack threshold stress intensity factor range and the endurance limit. This parameter has been used to study fatigue crack growth of short cracks as a means to study fatigue crack initiation in steels and is based on the concept that initiation occurs only when the material ahead of the crack tip is damaged enough by cyclic straining. A separate model has been explored that incorporates a microstructural variable, namely the grain size. For the two materials studied, the initiation and growth of small cracks have been investigated with consideration for crack closure. Using the material parameters, the number of cycles to initiate a fatigue crack has been determined.
Effects of Post-Tightening on the Residual Bolt Force and the Sealing Performance of Flanged Connections With PTFE Gaskets (Long Term Effects at Room Temperature)
Authors: Hagiri Taiki , Kobayashi Takashi , Nishiura Kengou , Uchiyama Kazuaki
Published: May 2012

It is known that bolt forces reduce significantly after tightening bolted flanged connections in which expanded PTFE gaskets are used. Bolts are often post-tightened in practice after a while to compensate for the reduction of bolt forces. The viscoelastic characteristic of expanded PTFE gaskets is the main cause for the phenomenon. However, the long term effects of the post-tightening on the residual bolt forces and the sealing performance of flanged connections have not been clarified yet. In this study, two sets of flanged connections (2 inch in nominal size), in which PTFE gaskets were used, were prepared and tightened. One of the flanges was post-tightened after a designated time. The reduction of bolt forces and the change in the sealing performance were measured for about two months. The results were compared with those of flanges without post-tightening. Based on the test results, the effectiveness of post-tightening was discussed from the viewpoint of the residual bolt force and the sealing performance. It has been clarified that the effectiveness of post-tightening depends on gasket material and that post-tightening is effective for expanded PTFE gaskets.
Tackling FSI Simulation for FIV Problems in Tube Bundle Systems With POD Approach
Authors: Pomarede Marie , Hamdouni Aziz , Liberge Erwan , Longatte Elisabeth , Sigrist Jean-Franc¸ois
Published: May 2012

Tube bundles in steam boilers of nuclear power plants and nuclear on-board stokehold are known to be exposed to high levels of vibrations under flowing fluid. This coupled fluid-structure problem is still a challenge for engineers, first because of the difficulty to fully understand it, second because of the complexity for setting it up numerically. Although numerical techniques could help the understanding of such a mechanism, a complete simulation of a fluid past a whole elastically mounted tube bundle is currently out of reach for engineering purposes. To get round this problem, the use of a reduced-order model has been proposed with the introduction of the widely used Proper Orthogonal Decomposition (POD) method for a flow past a fixed structure [M. Pomare`de, E. Liberge, A. Hamdouni, E.Longatte, & J.F. Sigrist - Simulation of a fluid flow using a reduced-order modelling by POD approach applied to academic cases; PVP2010, July 18–22, Seattle]. Interesting results have been obtained for the reconstruction of the flow. Here a first step is to propose to consider the case of a flow past a fixed tube bundle configuration in order to check the good reconstruction of the flow. Then, an original approach proposed by Liberge (E. Liberge; POD-Galerking Reduction Models for Fluid-Structure Interaction Problems, PhD Thesis, Universite´ de La Rochelle, 2008) is applied to take into account the fluid-structure interaction characteristic; the so-called “multiphase” approach. This technique allows applying the POD method to a configuration of a flow past an elastically mounted structure. First results on a single circular cylinder and on a tube bundle configuration are encouraging and let us hope that parametric studies or prediction calculations could be set up with such an approach in a future work.
Guideline for Repair Welding of Pressure Equipment in Refineries and Chemical Plants: Part 5—Repair Welding for Specific Materials - Heat Resistance Alloy and Non-Ferrous Metals
Authors: Watanabe Hirohisa , Shiga Keisuke , Ohno Atsushi
Published: May 2012

It has been recognized that repair welding takes an important role in the long term, safe operation of pressure equipment. Responding to the needs in petroleum and chemical industries, the Japan Welding Engineering Society (JWES) published Guideline for repair welding of pressure equipment at 2009. This paper describes the key points of repair welding for heat resistance alloy and non-ferrous metals such as Nickel, Copper, Titanium and their alloys, based on JWES’s guidelines. Before implementing repair welding, it is important to understand the features of damaged materials, because these materials have been used at severe environment in plants.
Important Residual Stress Features in Reactor Nozzle Dissimilar Metal Welds
Authors: Zhang Jinmiao , Song Shaopin , Dong Pingsha
Published: May 2012

This paper is focused on the study of residual stress distribution at a dissimilar metal weld (DMW) of nuclear reactor nozzle. The paper extends some of the recent research on this subject by investigating the effect of weld sequence and nozzle length design on the residual stress distributions. It also investigates the effect of a partial excavation repair and a weld overlay on the residual stress distribution. As a result, some of the important residual stress features at DMW are revealed and these features are discussed and summarized in the paper.
Ratcheting/Shakedown Analysis of Cracked Structures
Authors: Adibi-Asl R. , Reinhardt W.
Published: May 2012

The classical approaches in shakedown analysis are based the assumption that the stresses are eventually within the elastic range of the material everywhere in a component (elastic shakedown). Therefore, these approaches are not very useful to predict the ratcheting limit (ratchet limit) of a cracked component/structure in which the magnitude of stress locally exceeds the elastic range at any load, although in reality the configuration will certainly permit plastic shakedown. In recent years, the “Non-Cyclic Method” (NCM) was proposed by the present authors to predict the entire ratchet boundary (both elastic and plastic) of a component/structure by generalizing the static shakedown theorem (Melan’s theorem). The proposed method is based on decomposing the loading into mean (time invariant) and fully reversed components. The applicability of the NCM has been demonstrated for several uncracked components and structures using both analytical and numerical schemes. The present paper extends the NCM further to analyze plastic shakedown for two simple cracked components.
Development of Tritium Transport Package for ITER Supply
Authors: Lee Sanghoon , Lee Min-Soo , Lee Ju-Chan , Choi Woo-Seok , Seo Ki-Seog
Published: May 2012

For tritium supply to the fusion reactor of ITER (The Way to New Energy) [1], tritium need to be transported from tritium production sites, mainly the CANDU type reactor sites to the tritium plant building of ITER. Korea Atomic Energy Research Institute (KAERI) was commissioned the work of developing the transport package for tritium by ITER Organization and the first stage of the development has been just finished. The developed package was designed to carry 70 g of tritium and classified as a type B(U) package, which should comply with the requirements stipulated in IAEA Safety Standard Series [2]. The package is composed of a storage vessel, a containment vessel, an overpack and an aluminum liner which is a unique feature of the package. The aluminum liner between the storage vessel and the containment vessel is for containment control under the repetitive use of the package. The package has enough pressure resistance for 5 year in-site storage and the structural and thermal integrity under the hypothetical accident conditions has been demonstrated through a series of analyses.
Characterisation of Twin Co-Planar Flaws: Guidance for the Lower Shelf Regime
Authors: Bezensek Bostjan , Sharples John , Wilkes Mark
Published: May 2012

Structural integrity assessments use characterised flaws derived from simplifying the real flaw indications into a simpler flaw for the purpose of analysis. The guidance is historically derived from fatigue data and applied to other failure modes. Under cleavage conditions the guidance may not always be conservative as shown by the authors in earlier publications. This paper follows on to the investigation reported in PVP2010-25134 by examining the guidance for the characterised flaw on the lower shelf. Two options are examined: increasing the characterised flaw size or increasing the stress intensity factor for the original flaw. Both approaches result in a more pessimistic characterised flaw which is required to recover the conservatism of the characterisation procedure on the lower shelf.
Inclusion of Torsion With Bending and Pressure Loads for Pipes With Thin-Wall Regions
Authors: Bezensek Bostjan , Li Yinsheng , Hasegawa Kunio , Hoang Phuong H.
Published: May 2012

Piping installations may experience local wall thinning under predominant pressure and bending loading with a small amount of torsion loading. Assessment of the remaining pipe integrity must account for all loads and can benefit from resolving the multiaxial loads into an equivalent load. This paper presents results of the finite element analyses of straight pipes containing non-planar flaws (i.e. local wall thinning areas) subject to combination of pressure, bending and torsion. The pressure is 8 MPa and the torsion stresses are limited to 20% of the material’s flow stress. Flaws are introduced into a 4 inch OD pipe with an R/t of 6.64 and 9.36. The incipient plastic collapse moment at a given torsion moment is determined and compared with the plastic collapse moment of the pure bending case. The results show that for flaws with a depth less than 60% of the nominal pipe wall thickness the bending and torsion moments can be combined into an equivalent moment by vector summation (the Root of the Sum of Squares approach). For deeper flaws the effect of pipe and flaw geometry is observed.
Manufacturing of Large-Scale Polyurethane-Lined FRP Piping
Authors: Mertiny Pierre , Popella Robert , Juss Kulvinder
Published: May 2012

Fiber-reinforced polymer composite piping is known to provide excellent corrosion resistance and high specific properties such as strength-to-weight ratio. However, the propensity for micro-cracking of the polymer matrix and associated potential for fluid leakage, and/or insufficient capacity to endure damage from abrasive fluids transported in the piping, often requires composite piping to be equipped with internal polymeric liners. It has been shown that polyurethane liners provide good abrasion resistance and reliable fluid containment. A durable bond between polyurethane liner and structural composite pipe can be achieved employing suitable manufacturing protocols. This was demonstrated by earlier research for laboratory-scale pipe structures. In the present work, manufacturing procedures for large-scale piping structures are described along with the involved chemical and mechanical processes.
High Temperature Damage and Failure Assessment of Plant Components
Authors: Dogan Bilal
Published: May 2012

A comprehensive approach for the treatment of components operating at high temperature is of immediate industrial interest. Particularly, the components with weldments in currently aging plants are prone to failure. Although these components are designed for base load operation, they are now forced to cyclic operation. This important issue needs to be addressed by a methodology that will be developed and incorporated into design codes such as ASME, as well as in Fitness-for-Service (FFS) assessment procedures (e.g. API 579/ASME FFS1, R5, RCC-MR A16) for in-service plant components. Assessment of welded components for Fitness-for-Service is addressed in fragments in various procedures. The present paper gives an overview of the high temperature assessment procedures including recent developments in the FFS procedures. Experimental and analytical test results from ferritic steel P22, which is used in power generation and chemical processing industrial applications are presented.
A Simplified Stress Intensity Factor Relation for Assessment of External Axial Flawed Safety-Related Nuclear Power Plant HDPE Piping
Authors: Kalyanam S. , Krishnaswamy P. , Uddin M. , Shim D.-J.
Published: May 2012

PE piping has been used successfully for over 50 years in the natural gas distribution, water systems, petrochemical industry piping, and specialty applications for corrosive fluids. The application of PE pipes to safety-related service-water nuclear power plant (NPP) piping, demands superior material and fracture toughness performance at elevated stresses and thermal loads/gradients. The ASME Boiler and Pressure Vessel Code Case N-755 was developed to identify requirements that PE piping must meet and material qualification based on allowable stress levels in the presence of cracks/flaws and material resistance to crack growth. The PE and NPP industry intend to use PE pipes in safety-related, service-water applications and have conducted material evaluation tests that are similar in nature to those used earlier for qualifying PE materials for other applications listed above. Coupon and PENT tests that include controlled notches that simulate the stress-intensity factor (KI) of a typical axial flaw in PE pipe form the basis of current assessment procedures for PE material resistance to slow-crack growth (SCG). The applicability of these assessment methods, and experience from other applications, to specifying allowable flaw depths is of interest to the industry and is the subject of much discussion. In this study, a detailed investigation was conducted to assess KI for PE pipes with various outside diameters (OD) and a range of OD axial surface crack/flaw depths, different SCG test specimens with prescribed initial notch, notched-pipe tests (NPT) prescribed by international standards. A simplified equation to represent the SIF variation with crack/flaw depths for a large group of PE pipes (with same DR value) and same axial semi-elliptical surface flaws was developed.
Determination of Flow Structure in a Tube Array by Particle Image Velocimetry
Authors: Mureithi Njuki , Masabarakiza Claude
Published: May 2012

Particle Image Velocimetry (PIV) presents a possible approach to measuring two-phase flow parameters over a large area, leading to a snap shot of flow behavior in complex geometries such as tube bundles. Tests have been conducted in a 2m long wavy wall channel simulating the open lane within a rotated triangular array. The results show that liquid phase PIV measurements must be limited to very low void fractions. On the other hand, much information can be gained from the gas phase data. The details of the flow structure within the array are revealed. Current measurements, performed in the bubbly flow regime, show that even in this regime, the flow structure is significantly non-uniform and complex. Bubble diameters have been found to be strongly dependent on flow velocity; the effect of turbulence shear at high flow rates breaking up the bubbles to smaller sizes. The PIV measurements yield the complete averaged velocity vector field in the measurement region. The velocity profiles across the measurement section are also obtained. The non-uniform profiles show the challenges associated with attempts to estimate average void fractions and slip ratios in the array.
Seismic Capacity Tests of Motor Operated Fans in Ventilation Systems
Authors: Hirose Jiro , Suzuki Kenichi , Yoshika Naoki
Published: May 2012

Motor operated fans (M/O fans) of safety related ventilation systems in nuclear power plant facilities are required to maintain operability following earthquakes. M/O fans are designed to qualify the validated response capacity ranged from 2.3×9.8m/s2 to 2.6×9.8m/s2 at the bearing bracket depending on the type of fan in accordance with “JEAC4601-2008” [1] in Japan. Since the Regulatory Guide for Reviewing Seismic Design of Nuclear Power Reactor Facilities (Seismic Guide) revised in September 2006 [2] prescribes that the facilities in class S shall maintain their safety functions under seismic forces caused by a Design Basis Earthquake Ground Motion (DBEGM) Ss, a reevaluation is required for the seismic capacity of M/O fans to ensure operability. Japan Nuclear Energy Safety Organization (JNES) performed a series of seismic capacity tests for specimens of actual M/O fans, including a centrifugal fan with coupling and an axial fan without coupling. A program for a vibration test was developed to ensure its safety-related function to operate following earthquakes and to maintain the design flow rate and the design pressure. The tests were carried out by a shake table up to the response acceleration 7.5×9.8m/s2 at the bearing bracket in horizontal directions, and 3.0×9.8m/s2 in the vertical direction individually. As a result of the tests, the operability was qualified for each type of fan up to the above target acceleration values excluding a few exceptions. As a failure mode of the M/O centrifugal fan with coupling, the labyrinth seal was identified to be vulnerable to wear. The obtained data of seismic capacity are expected to be applied for the seismic reevaluation of M/O fans.
Development of Engineering Formulae for Stress Concentration Factors of Local Wall Thinning in CANDU Feeder Pipe Under Pressure
Authors: Kim Jong Sung , Seo Jae Seok
Published: May 2012

Feeder pipes that connect the inlet and outlet headers with the in-reactor fuel channels in CANDU nuclear power plants are considered as safety Class 1 piping items. Therefore, fatigue of the feeder pipes should be assessed at design stage in order to verify structural integrity during design lifetime. In accordance with the fatigue assessment result, cumulative usage factors of some feeder pipes have significant values. An active degradation mechanism for the outlet feeder piping made of SA-106 Grade B carbon steel is local wall thinning due to flow-accelerated corrosion. This local wall thinning can cause increase of peak stress due to stress concentration by notch effect. The increase of peak stress results in increase of the cumulative usage factor. However, present fatigue assessment doesn’t consider the stress concentration due to the local wall thinning. Therefore, it is necessary to assess the effect of local wall thinning on the stress concentration. This study developed the engineering formulae for stress concentration factors of the local wall thinning in the CANDU feeder pipe under internal pressure by using the engineering procedure of Kinectrics Co.. Finally, the developed formulae were applied to the elbow feeder pipes and compared with the finite element analysis results. As a result of comparison, it is identified that the engineering formulae is valid.