bluuebunny/crossref_metadata_2025_split huggingface dataset:
Integrity Evaluation of Korean Nuclear Reactor Pressure Vessel Under Pressurized Thermal Shock Conditions According to JEAC
Authors: Kim Se-Chang , Choi Jae-Boong , Cho Doo-Ho , Lee Sang-Min , Kim Yong-Beum , Chung Hae-Dong 
Published: January 2014

In nuclear power plant, reactor pressure vessel (RPV) is the primary equipment that contains reactor cores and coolant. The RPV integrity should be evaluated in consideration with transient operation conditions and material deterioration. Especially, the pressurized thermal shock (PTS) has been considered as one of the most important issues regarding the RPV integrity since Rancho Seco nuclear power plant accident in1978.
In this paper, integrity evaluation of Korean RPV was performed by using finite element analysis. PTS conditions like small break loss of coolant accident (SBLOCA) and Turkey Point steam line break (TP-SLB) were applied as loading conditions. Neutron fluence data of actual RPV operated over 30 years was used to determine fracture toughness of RPV material.
The 3-dimensional finite element model including circumferential surface crack was generated for fracture mechanics analysis. The RPV integrity was evaluated according to Japan Electric Association Code (JEAC).
Calculation Approach of Optimum Cutting Surfaces of Extra Length of Pipe Spools
Authors: Kitahara Takashi , Yamamoto Yuichi , Tagawa Yasutaka 
Published: January 2014

To connect a pipe spool between existing pipes with high accuracy for power plant constructions, a calculation approach which figures out appropriate cutting positions and angles of extra length areas of the spool has been developed. In this approach, center positions and axes of end surfaces are modeled numerically based on three-dimensional measurement of each pipe, and the appropriate cutting surfaces are calculated by geometric analysis of the models with considering for ease of cutting work at the construction site.
This paper described a modeling method of pipes, a calculation algorithm of the proper cutting surfaces of the spool, and a verification result of the calculation.
Consideration of Creep in Design Rules of AFCEN RCC-MRx 2012 Code
Authors: Lebarbé T. , Petesch C. , Lejeail Y. , Lamagnère P. , Dubiez-Le Goff S. 
Published: January 2014

The 2012 edition of the RCC-MRx Code has been issued in French and English versions by AFCEN (Association Française pour les règles de Conception et de Construction des Matériels des Chaudières Electro-nucléaires). This Code is the result of the merger of the RCC-MX 2008 developed in the context of the research reactor Jules Horowitz Reactor project, in the RCC-MR 2007 which set up rules applicable to the design of components operating at high temperature and to the Vacuum Vessel of ITER.
This new edition is the opportunity to publish also the background of the rules. This paper is one illustration of what may be such a document, on a dedicated example, the creep rules. It contains an overview of the design rules associated to the creep damage and explains the purpose and the origins of these rules. This type of exercise is going to be generalized to all the parts of the code in AFCEN technical publications, the criteria.
User’s Design Specification Preparation for 2¼Cr-1Mo-¼V Reactors in Accordance With ASME Section VIII, Division 2 Code and Code Case 2605
Authors: Stefanovic Radoslav , Avery Alicia , Bardia Kanhaiya , Kabganian Reza , Oprea Vasile , Seipp Trevor 
Published: January 2014

Today’s hydroprocessing reactor manufacturers use 2¼Cr–1Mo–¼V steel to build lighter reactors than conventional Cr-Mo reactors. Manufacturing even lighter hydroprocessing reactors has been enabled with the introduction of the new ASME Section VIII Division 2 Code, initially released in 2007. The higher allowable stresses in the new Division 2 for these Vanadium-modified steels permits even lighter reactors to be built while maintaining suitable design margins. The new Division 2 Code requires additional engineering to ensure safe design. One of the challenges the engineer is faced with, is preparation of the User’s Design Specification (UDS) including new and more stringent requirements for fatigue evaluation. As the operating temperature of the rector is higher than 371°C, engineers have to evaluate the fatigue life of the reactor in accordance with Code Case 2605 (CC2605). CC2605 requires inelastic analysis and evaluation effects of creep. Vanadium-modified reactors require additional care during fabrication to prevent higher hardness around weld areas, reheat cracking, and reduced toughness at lower temperatures in the “as welded” condition.
This paper provide guidance for the preparation of an ASME Section VIII Division 2 User’s Design Specification including process descriptions of all the cycles expected for the life of the rector and analysis requested by CC2605. An example of such an analysis, including finite element analysis results, is provided in this paper. Requirements to provide the material specification is also discussed with an emphasis on prevention of reheat cracking, hardenability, and temper and hydrogen embitterment.
Numerical Analysis of Hydrogen Distribution in Welds of Stainless Clad Steels for Hydrogen Storage Pressure Vessels
Authors: Mori Hiroaki , Kayano Rinzo , Ogiwara Hiroyuki , Saida Kazuyoshi , Nishimoto Kazutoshi 
Published: January 2014

Numerical analysis of hydrogen distributions in the welds of stainless clad steels, which are the structural material of hydrogen storage pressure vessels, was conducted to predict the hydrogen embrittlement in the pressure vessels. The theoretical model for the calculation was based on the activity of hydrogen considering residual stresses induced by welding and hydrogen accumulating sites such as precipitates and dislocations.
From the calculations, hydrogen concentrates at the center of weld metals in both of longitudinal and circumferential directions in welded joints of stainless clad steels. However, the hydrogen contents were much lower than those in the carbide layers, in which are observed in steels with weld overlay of stainless steels, as the calculation of hydrogen distribution in the materials using the higher evaluated diffusion coefficient of hydrogen with considering margin of safety.
Therefore, it seemed that the risk of cold cracking due to hydrogen embrittlement was sufficiently lower in the welds of stainless clad steels during many cycles of shutdown and restart of the pressure vessels in long-term operation.
Cemented Carbide Plungers for LDPE Hyper Compressors: Properties, Defects and Reconditioning
Authors: van Loon Luc 
Published: January 2014

Cemented carbide plungers are used in hyper compressors to compress ethylene gas to the reactor pressure between 160 and 350 MPa. Since cemented carbide is a brittle material, the failure load is determined by the nature and distribution of defects. This makes the plunger one of the most critical components in the LDPE production plant. Plunger failure can lead to very high costs because of damage on the compressor and production loss and in the worst case it can cause very high gas leakages that can lead to an explosion and fire.
Typical defects on plungers have been analyzed and related to their origin. Corrosion and thermo-mechanical fatigue cracks are discussed in detail because they are most frequently found. Causes of these defects can be process or component related, but also the influence of reconditioning techniques has been analyzed. Since most of plunger fractures are directly initiated by fatigue cracks, external factors that can lead to these cracks are analyzed.
Simplified Prediction of Creep Void Density in Heat-Affected Zone of Grade 122 Steel Considering Multiaxial Stress State
Authors: Murakami Eiji , Hashimoto Masamitsu , Kikuhara Seiji 
Published: January 2014

This paper deals with a simplified method for approximately predicting creep void growth in heat-affected zone (HAZ) of ASME grade 122 (11Cr-2W-0.4Mo-Cu-Nb-V) steel weldments. Authors have proposed a simplified prediction method based on the relationship between creep void density increasing rate and multiaxial stress state. This method has been applied to prediction of creep void growth behavior for grade 91 (9Cr-1Mo-Nb-V) tubular specimens with longitudinal weldments. In this study, the method has been also applied to grade 122 steel to clarify the applicability of the method.
Internal pressure creep tests of grade 122 tubular specimens with longitudinal weldments subjected to several internal pressures have been conducted to reveal creep void growth behavior in HAZ. In addition, finite element creep analyses for the specimens at different creep strain rates in base metal, weld metal and HAZ have been carried out to investigate distribution of stresses and stress triaxiality factor in HAZ. A comparison between stress distributions and creep void distributions revealed that stress triaxiality factor affects growth behavior of creep voids. From the result, the relationship between creep void density increasing rate and the parameter as a function of principal stress and triaxiality factor was established. It was found that the slope of this relationship for 122 steel has a tendency to be slightly small compared with grade 91 steel.
To demonstrate the applicability of the proposed simplified prediction method, the method was applied to the internal pressure creep test specimens at different experimental conditions. As a result, the predicted void distribution and void density increasing rates for grade 122 steel were in good agreement with the experimental results.
Development of Plastic Collapse Assessment Procedure for Cylindrical Vessels With a Local Thin Area Near a Nozzle Under Internal Pressure
Authors: Oyamada Kenji , Konosu Shinji , Horibe Tadashi , Ogasawara Kenta , Miyashita Tetsuji , Ohno Takashi 
Published: January 2014

There are numerous cases where a local thin area has found near a nozzle attachment in cylindrical pressure vessels. Since the stress concentration due to a nozzle hole under internal pressure significantly affect to the stress state of the vessel near the nozzle, it must be taken into account in its plastic collapse assessment. In this paper, a new plastic collapse assessment procedure for cylindrical vessels with a local thin area near a nozzle attachment under internal pressure was proposed. This proposal utilizes the existing reference stresses to estimate the plastic collapse load under three-axial condition derived in accordance with the Tresca theory. The distribution of stress concentrations in vessel wall due to a nozzle attachment depends on its reinforcement condition for the nozzle hole, so the stress state should be computed by linear FEA in advance. The stress concentration factors are provided with normalizing of generated stresses in vessels near a nozzle attachment for the similar type of dimensions, orientations and projections of the nozzle attachment by the computed stresses with already-proposed equations for no reinforcement conditions.
The plastic collapse loads predicted by the proposed reference stress are ascertained with the results of experiments and non-linear FEA.
Advanced Assessment of the Ductile Fracture Mechanism in A508 Class 3 Reactor Pressure Vessel Steel Using Laboratory X-Ray Tomography
Authors: Daly Michael , Leonard Fabien , Sharples John K. , Sherry Andrew H. 
Published: January 2014

Ductile damage is characterised by the nucleation, growth and coalescence of voids at initiating particles within the volume of high triaxial stresses and plastic strain ahead of a crack-tip or stress concentrator. To establish a more detailed understanding of the mechanism of ductile fracture in the A508 Class 3 ferritic RPV steels and to improve fracture models, the ductile damage was quantified below the fracture surface of tested compact test specimens using laboratory X-ray tomography imaging with sufficient resolution to image voids of approximately 10μm in diameter. The average distribution of void volume fraction as a function of distance below the fracture surface was quantified, and the initiating and coalescence mechanisms were characterised. The highest void volume fraction was observed at the fracture surface and this tends to decrease as a function of distance below the fracture surface. This decrease is periodically perturbed by large voids associated with inclusions which are distributed throughout the microstructure and act as further nucleating sites at low strains.
This distribution of voids was correlated with the local variations in stress triaxiality and plastic strain derived from finite element analyses to provide a relationship between experimental observations and the Rice and Tracey model. These correlations aim to provide new data and understanding with which to calibrate mechanistically based models such as the Gurson-Tvergaard-Needleman (GTN) model.
The Role of Computational Weld Mechanics in the Weld Repair of Canada’s NRU Nuclear Reactor
Authors: Goldak John A. , Yetisir Metin , Pistor Rob 
Published: January 2014

The NRU reactor at Chalk River Laboratories is one of the largest and oldest research reactors in the world. It has been the world’s largest producer of medical isotopes, which are used in cancer treatments, nuclear medicine and other diagnostic procedures. The NRU reactor was shut down in May 2009 when a heavy water leak was detected in the reactor building. Subsequent inspections indicated that the reactors aluminum vessel corroded at various locations resulting in heavy water seeping through the reactor vessel.
The extent of the damage required a complex pattern of internally applied weld overlays in numerous areas. Weld repair was further complicated by concerns over the effect of radiation hardening of the aluminum and compositional changes (irradiation induced transmutation of aluminum to silicon). Considering the deformation and stress associated with welding aluminum plate (Figure 1) and the aggressive return to service schedule, Atomic Energy of Canada (AECL) commissioned an extensive Computational Weld Mechanics (CWM) campaign to guide the repair design and optimize structural integrity. This paper describes the technical issues encountered in the design of the weld repair processes and how CWM was used in selecting welding strategies. Traditionally, welding pattern, progression and sequence are determined through a combination of trial and error on mock ups along with welders experience and analyzed by computer after the fact. To the authors knowledge, this is the first weld repair that used CWM to assess proposed designs of welds.
Hourglass Control Convergence Studies for Hexahedral Elements Developed by the ASME Special Working Group on Computational Modeling
Authors: Molitoris David P. , Bjorkman Gordon S. , Tso Chi-Fung , Yaksh Michael 
Published: January 2014

The ASME Special Working Group on Computational Modeling for Explicit Dynamics was founded in August 2008 for the purpose of creating a quantitative guidance document for the development of finite element models used to analyze energy-limited events using explicit dynamics software. This document will be referenced in the ASME Code Section III, Division 3 and the next revision of NRC Regulatory Guide 7.6 as a means by which the quality of a finite element model may be judged. One portion of the document will be devoted to a series of convergence studies that demonstrates the effect of hourglass control settings on solution convergence for reduced integration elements. These convergence studies will demonstrate the importance of selecting an appropriate hourglass control setting to achieve accurate results for large deformation simulations using reduced integration elements.
In this paper, the authors present the results of a convergence study for an impulsively loaded propped cantilever beam constructed of LS-DYNA reduced integration hexahedral elements using different hourglass control settings. A large load is applied to produce large deformations and large plastic strains in the beam.
Brittle Fracture Assessments on Offshore Piping Systems
Authors: Subramanian Kannan , Penso Jorge , McVinnie Graham , Garic Greg 
Published: January 2014

Offshore piping systems may be subject to low temperatures due to operation related scenarios and are cause for brittle fracture concern. The analyses included in this work consider probable events leading to low temperature conditions such as auto-refrigeration. In such circumstances, brittle fracture assessments of piping are typically carried out using API 579-1/ASME FFS-1, latest referred as API 579, procedures. The assessment of piping systems are in many cases very involved, requiring extended piping system information followed by stress analysis and MAT calculations depending on the material type, thickness of the piping analyzed, and stress levels. In addition, the component-by-component assessment approach recommended in API 579 leads to tedious calculations.
In this paper, approaches used for static and dynamic low temperature scenarios are presented. Static cases involve constant pressures and temperatures. Dynamic cases involve varying pressures and temperatures as the low temperature events unfold (e.g., blowdown of a valve or a vessel). Dynamic cases warrant the requirement of a safe operating envelope or MAT curve similar to those developed for pressure vessels. Case studies involving the influence of the extent of the system analyzed and the restraint conditions on the results are also presented. In addition, the importance of separately assessing the rated components such as flanges and valves away from the stress analysis is discussed. Based on the assessments carried out, a discussion on the toughness rules defined in ASME Section VIII Divisions 1, 2, and the original piping code of construction is provided.
Determination of J-R Curves for Dissimilar Metal Welds Using Normalization Method and Compact Tension Specimens
Authors: Zhu Xian-Kui , Shim Do-Jun , Scott Paul , Rudland David 
Published: January 2014

Normalization method is adopted in this paper to determine fracture resistance curves, i.e. J-R curves for dissimilar metal (DM) welds involved in nuclear reactor pressure vessels. Due to the restriction of material availability, three compact tension (CT) specimens containing a DM weld with a crack were utilized and tested under the guideline of ASTM fracture toughness test standard E1820 [1]. The test data of load versus load-line displacement were recorded during the tests, and directly applied to estimate crack extension using the normalization procedures. The J-R curves are then developed without the need of online crack extension measurement.
Three J-R curves of DM welds were obtained using the standard 1T CT specimens and the normalization method. These resistance curves were evaluated through comparison with those obtained from small sized ½T CT specimens via ASTM E1820 standard procedures and those obtained from the electrical potential drop method. The results showed that the normalization method, ASTM E1820 standard procedures, and the electrical potential drop method can determine similar fracture resistance curves for DM welds in a good agreement. Among the three methods, the normalization method is of most attractive because it is the only one that does not need crack extension measurements, and thus test costs are saved.
Weld Residual Stress Analysis and Axial PWSCC Predictions in a Double Vee Groove Large Diameter Nozzle
Authors: Brust Frederick W. , Punch E. , Shim D. J. , Rudland David , Rathbun Howard 
Published: January 2014

Flaw indications have been found in some dissimilar metal (DM) nozzle to stainless steel piping welds and reactor pressure vessel heads (RPVH) in pressurized water reactors (PWR) throughout the world. The nozzle welds usually involve welding ferritic (often A508) nozzles to 304/316 stainless steel pipe) using Alloy 182/82 weld metal. The welds may become susceptible to a form of corrosion cracking referred to as primary water stress corrosion cracking (PWSCC). It can occur if the temperature is high enough (usually greater than 300°C) and the water chemistry in the PWR is typical of operating plants. The weld residual stresses (WRS) induced by the welds are a main driver of PWSCC.
The purpose of this paper is to determine the weld residual stresses in a double-vee groove welded nozzle and then to model the natural crack growth in the weld. The double vee groove geometry has not been modeled much to date especially in such a large nozzle. This leads to a rather unique weld residual stress pattern which changes as the throat of the double vee is approached. Axial crack growth is modeled using a natural crack growth procedure. This was challenging since the crack shape necked down in the region where the tips of the vee grooves meet making the mesh development during this process challenging. This analysis provides information regarding crack growth evolution versus time. In addition, some comments regarding idealized growth are presented.
A Unified Approach for Comparison of Multiaxial Fatigue Models
Authors: Noban M. , Adibi-Asl R. 
Published: January 2014

There are several methods of estimating fatigue crack initiation life under multiaxial loading including strain and energy based methods.
This paper investigates a unified approach that enables comparison of these different models. The various fatigue models are mapped into a specific domain, i.e., stress, strain or energy domain. Three sets of experimental results available from literature are used for this comparison.
Under simultaneous axial and torsional loadings, the fatigue life predictions of investigated fatigue models are in a better agreement when the axial load is more dominant than torsional loading. The differences in the predictions increase when torsional loading increases. This is mostly due to the fact that fatigue parameters are generally determined and calibrated under uniaxial cyclic loading.
Preliminary Evaluation of the Flooding Effects on an Existing PWR
Authors: Baudanza Vincenzo , Lo Frano Rosa , Forasassi Giuseppe 
Published: January 2014

The aim of the study is the evaluation of the structural effects induced by a severe flooding or tsunami (which is one of the external events to be considered for the safety margin reassessment purpose according to the International requirements, after the Fukushima accident) in an outer containment walls of a typical PWR.
The hydrodynamic forces exerted by the breaking waves, characterizing the inundation phase of tsunami/flooding phenomenon, are calculated in agreement with ASME rules.
Therefore to evaluate the consequences and damages, if any, induced by the breaking water waves which have arisen on an existing PWR containment building, non linear analyses (by using an adequate FEM code) were performed simulating the impact forces of the water waves in terms of pressure. Moreover a FSI analysis was carried out in order to verify the adequacy (and consistency) of the methodology adopted in the evaluation of the pressure forces mentioned above.
To analyze the performances of the containment building suitable reinforced concrete material properties and damage phenomena features were considered.
The results obtained highlighted that the tsunami effects are strongly dependent on the wave height, flow velocity, hydrodynamic phenomena and on the geometry and material behaviour of the analyzed structures.
Finally they showed that the containment building considered seemed capable to withstand the flooding/tsunami effects without loss of the integrity of PWR containment structure.