bluuebunny/crossref_metadata_2025 huggingface dataset:
Scheduling Strategy of Multiple Semi-Active Controllers With Information on the Disturbance and the Structural Response
Authors: Hiramoto Kazuhiko , Matsuoka Taichi , Sunakoda Katsuaki
Published: December 2016

A scheduling strategy of multiple semi-active control laws for various earthquake disturbances is proposed to maximize the control performance. Generally, the semi-active controller for a given structural system is designed as a single control law and the single control law is used for all the forthcoming earthquake disturbances. It means that the general semi-active control should be designed to achieve a certain degree of the control performance for all the assumed disturbances with various time and/or frequency characteristics. Such requirement on the performance robustness becomes a constraint to obtain the optimal control performance. We propose a scheduling strategy of multiple semi-active control laws. Each semi-active control law is designed to achieve the optimal performance for a single earthquake disturbance. Such optimal control laws are scheduled with the available data in the control system. As the scheduling mechanism of the multiple control laws, a command signal generator (CSG) is defined in the control system. An artificial neural network (ANN) is adopted as the CSG. The ANN-based CSG works as an interpolator of the multiple control laws. Design parameters in the CSG are optimized with the genetic algorithm (GA). Simulation study shows the effectiveness of the approach.
Dynamic Effects on Fracture Toughness for Ferritic Steel in the Ductile-to-Brittle Transition
Authors: Jacquemoud C. , Delvallée-Nunio I. , Balestreri F.
Published: December 2016

Dynamic loading effects on fracture toughness of ferritic steel have been evaluated in the ductile-to-brittle transition, considering loading rates representative of object drops. To verify that the design fracture toughness curve, initially defined from static tests, remains conservative for the integrity assessment of object submitted at low temperature to a dynamic impact due to a drop, experiments on 16MND5 ferritic steel have been performed.

A three-point bending set-up and a thermal chamber have been designed in order to perform dynamic fracture tests on large Single Edge-notched Bending SE(B) specimens, at very low temperature. Considering that the reference temperature of the material is −122°C (defined from quasi-static tests), dynamic drop tests have been performed at −120°C, −80°C and 0°C in order to cover the ductile-to-brittle transition of the material. A shift of +80°C of the reference temperature has been observed with the increase in the stress intensity rate, from less than 1 MPa.m0.5/s in quasi-static tests to values up to 105 MPa.m0.5/s for the dynamic SE(B) tests.

Numerical simulations of the tests, compared to classical static analysis, have confirmed that the effects of inertia and viscosity on fracture toughness are negligible at these temperatures (<0°C). Equivalent static analysis appears sufficient to study such dynamic tests.
Nonlinear Finite Element Analysis of a Full-Scale Test of a Cracked Dissimilar Weld for Ageing Nuclear Power Piping and Failure Assessment
Authors: Zeng Lingfu , Luo Chouping , Jansson Lennart G.
Published: December 2016

In this paper, non-linear finite element analysis of a full-scale laboratory test, a Benchmark four-point bending test of a straight pipe with an obliquely inserted crack in a dissimilar metal weld of ferritic steel (A508), austenitic steel (316L), weld material (308L) and buttering material (309L/308L), is conducted. The behavior of the crack front at the load level, at which the crack initiation is observed in the test, are computed, summarized and examined. A comparison to the results from the test and from linear finite element analysis is made. Computed results confirm our recent observations through linear fracture mechanics assessment: (i) The fracture initiation predicted by using J-integral based mixed mode cracking criteria may approximately be achieved by an “effective stress intensity factor” based approach; (ii) it is not conservative to use a purely mode-I based criterion for the fracture assessment for typical problems of mixed mode driven cracking. This paper is an extension of our recent work reported in the 2015 PVP conference, which addresses the fracture assessment using linear finite element analyses.
Environmental Fatigue Evaluation Considering Transient Stress History for Piping
Authors: Kim Youn-Jung , Kang Sun-Yeh , Park Byung-Jong , Kim Gee-Seok , Kim Hyun-Min
Published: December 2016

The environmental fatigue evaluation for piping is performed based on conservative formulas and environmental correction factors (Fen) calculation because of the difficulty of finding transient strain history and to reduce the cost of the analysis. Therefore, more sophisticated analyses using a finite element model of piping would be required to meet Code requirement (cumulative fatigue usage factor including the environmental effects, CUFen < 1).

The environmental fatigue evaluation was performed considering the transient stress history for pressurizer surge and spray piping. The stress histories due to the thermal moment and thermal gradient through the wall thickness were evaluated using a three-dimensional piping system model. The strain rate for Fen calculation was calculated in accordance with draft Code Case 10-293 and 14-1177.

For the purpose of comparison, environmental fatigue usage factors and Fen are calculated based on the ASME Code NB-3600 rules. The differences of Fen, CUF, and CUFen are reviewed between the methods using NB-3200 rule and NB-3600 rule.

Finally, this paper shows that environmental fatigue evaluation considering transient history is an effective method in lowering the environmental CUF value of the piping.
Nuclear In-Service Inspection Codes ASME Section XI and RSE-M Codes Comparisons
Authors: Faidy Claude
Published: December 2016

This paper will compare two major In-Service Inspection Nuclear Codes: the Boiler and Pressure Vessel Code Section XI developed by ASME on the one hand and French RSE-M developed by AFCEN on the other hand. These two Codes cover totally or partially:

- General Introduction

- In-service and pre-service inspection program

- In-service inspection techniques and qualifications

- Surveillance in Operation

- Flaw evaluation

- Repair-Replacement

- Quality Assurance and Documentation

- Appendices and Code Cases

A general presentation of the two Codes will be developed and followed by a general comparison.

To conclude, the paper will consider two particular examples for detailed comparison:

- K stress intensity factor handbooks comparison for circumferential flaws in cylinder: ASME Code Appendix A3000 and RSE-M Code Appendix 5-4, last published editions

- analysis of longitudinal crack in steam generator tubes
Short-Term Burst Pressure of Large Diameter and High Pressure Reinforced Thermoplastic Pipe
Authors: Nie Xinyu , Shi Jianfeng , Zheng Jinyang
Published: December 2016

Reinforced thermoplastic pipe (RTP), which basically consists of thermoplastic matrix and reinforced layers, has many advantages such as good flexibility, corrosion resistance and long service life. It has been used in oil and gas transportation pipeline industry for several decades, but generally has either low working pressure or small piping size which limits its application range. Recently, a new type of RTP with high design pressure of 6.9 MPa and large outside diameter of 490 mm was manufactured to substitute traditional metallic piping for long distance oil and gas transportation. In this paper, mechanical properties of such RTP, which is composed of four layers’ cross helically wound steel wires in the middle and two layers’ high density polyethylene (HDPE) inside and outside, are studied. Firstly, a multi-layer model was proposed to analyze the stress-strain relationship for the complex reinforcement structure considering the elasticity of both steel wires and HDPE. Further, an analytical procedure was developed to predict the short-term burst pressure (STBP) of high pressure RTP by taking the nonuniformity of reinforced steel wires into consideration. The practical position and nonuniformity of reinforced steel wires were measured by ultrasonic phased array technique. Then, short-term burst tests were conducted to validate the proposed model. Hoop strains at different internal pressures were measured and a good agreement with theoretical results was obtained, which verifies the effectiveness of the presented model. Finally, some differences of analytical and experimental techniques for STBP between normal RTP and RTP with large diameter and high design pressure were further discussed.
Interaction of Residual Stresses With Applied Stresses in a Dissimilar Metal Electron Beam Welded Specimen
Authors: Abburi Venkata K. , Truman C. E. , Khayatzadeh S. , Coules H. E.
Published: December 2016

Dissimilar metal welds are often used in nuclear reactors to connect the ferritic components to the austenitic stainless steel pipes. One of the pressing concerns of such design is the presence of cracks at the interface. The situation is further complicated by the differences in the yield strength at the interface compared to the base materials, the existence of residual stresses in high magnitude and the loading conditions of the crack in service. Residual stresses when combined with the service loads may affect the susceptibility to failure. Therefore studying the interaction between the applied and residual stresses in a component is crucial to understand the fracture behaviour and the accurate failure assessment of cracks. The objective of the following research is to assess the fracture behaviour of the crack located at the interface of a dissimilar metal weld between the ferritic P91 steel to an austenitic AISI 316LN steel made from electron beam (EB) welding, using a 3D elastic-plastic finite element analysis under the presence of residual stresses. A numerical model was developed to simulate the fracture behaviour of cracked body under applied load in the presence of residual stresses from the welding process and predict the J-integral around the crack tip. The numerical model was developed in stages to simulate the welding process, extraction of C(T) blank specimen and finally the behaviour of the cracked body under residual stresses and service loads. The model was validated at various stages using neutron diffraction measurements on the welded plate, after the C(T) specimen extraction but prior to the introduction of the crack and the residual stresses around the crack tip after the introduction of crack.
Experimental Investigation on Buckling of Steel Nuclear Containment With Elliptical Head
Authors: Li Keming , Zheng Jinyang , Zhang Zekun
Published: December 2016

Thanks to relative ease of fabrication and erection, steel containments with a torispherical or elliptical head are common in large nuclear power plants with relatively high internal pressure. Buckling failure mode is critical in the design of a steel containment with elliptical head under internal pressure. An experiment on buckling of elliptical head under internal pressure is presented in this paper. A test vessel was designed to provide a substantial margin of safety which permitted testing the head to rupture. The head has a diameter of 4797 mm, radius-to-height ratio of 1.728 and nominal thickness of 5.5 mm. Initial shape and shell displacement measurements of the head were carried out by using 3D laser scanners. The details of the buckling behavior are given. Initial buckling pressure was predicted by nonlinear finite element method considering the measured initial shape of the head. The agreement between the initial experimental buckling pressure and that predicted by the nonlinear finite element method is good. It is very useful in the buckling evaluation and the development of design rules for steel nuclear containment with elliptical head.
Visualization of Shock Wave Propagation Behavior of the General-Purpose Batch Processing for Pressure Vessel by Numerical Simulation
Authors: Shimojima Ken , Higa Yoshikazu , Higa Osamu , Takemoto Ayumi , Itoh Shigeru , Yasuda Atsushi , Iyama Hirofumi , Watanabe Toshiaki
Published: December 2016

Recently, National Institute of Technology, Okinawa College (ONCT) has been developing a new food processing method using underwater shock wave. The continuous-operation device was manufactured for the production of rice flour, the amount of milling flour per hour and the quality of the rice powder were evaluated. In the case of Yuzu (Citrus junos), an improved fragrance was obtained using this methods compared with other general processing method. The authors have also developed a batch-type crushing device (pressure vessel) for various food processing. However, the mechanism by which is processed using shock waves has not been clarified. Therefore, in this study, the propagation characteristics of a shock wave in the developed pressure vessel were evaluated by numerical simulation. The characteristics of processing is evaluated using shock wave and, the pressure resistance of the vessel was analyzed. In addition, food processing experiments using the developed device were performed. In which, in which “Yuzu” were crushed. Yuzu before-and-after crushing were compared, and the effect of shock wave were clarified.
A Probabilistic Approach to Predicting Pipework Failures in High Temperature Environments
Authors: Cannell Benjamin , Lloyd David , ElAgha Feras , Knowles David
Published: December 2016

Structural integrity assessments are traditionally undertaken using lower bound deterministic approaches whereby the worst combination of loads, operating conditions and material properties are assumed. This can lead to excessively conservative predictions which give pessimistic outlooks for plant life. A more representative approach which allows for consideration of acceptable levels of reliability of a component / system can be achieved through use of probabilistic assessment methods. A probabilistic approach aims to capture the uncertainties in the plant conditions, system loads and material properties (including degradation in-service).

This paper outlines a focused approach to undertaking a ‘Monte-Carlo’ probabilistic assessment of thin stainless steel pipework in high temperature environments considering failure due to creep rupture and plastic collapse whereby known or estimated statistical distributions of the assessment inputs are randomly sampled. The method is undertaken in Excel using VBA and it is developed to provide a transparent, quick and easy approach for a probabilistic assessment.
Tensile Testing and Analysis of Notched Low Alloy Steel Specimens
Authors: Wormsen Anders , Kirkemo Finn , Hagner Torulf
Published: December 2016

Notched axisymmetric specimens of two high strength low alloy steels used frequently in the subsea industry have been tensile tested to failure in air and in a 3.5% NaCl artificial seawater solution with cathodic protection (CP). The aim of the testing was to provide input to an initial assessment of elastic-plastic static load-capacity analysis of low alloy steels with material and quality control requirements according to ISO 13628-7 (ISO-7). The tensile testing in seawater with CP was performed in order to investigate whether hydrogen as formed by the CP system may have an effect on the ductility and strength that needs to be taken into account in the static load-capacity analysis and hence in design.

Local and global static load-capacity criteria from ASME VIII Div. 3 (Div.3), ISO-7, NORSOK U-001 (U-001) and API 6X (6X) have been considered for the notched specimens. Recommendations regarding elastic-plastic static load-capacity analysis of subsea equipment are given. The specimens tested in seawater with CP were found to have a reduced ductility and strength compared to the corresponding specimens tested in air. Further testing in seawater with CP is recommended before it can be concluded whether the environmental effect of the hydrogen needs to be included in the static load-capacity analysis of high strength low alloy steels.
Some Practical Aspects of Class 1E Actuator Qualification on Comparing Test Levels and Design Basis Event Loading
Authors: Farrell Ronald S.
Published: December 2016

All power operated valve actuators that perform a critical safety function in nuclear power plants must be backed by testing to demonstrate they are capable of reliably performing their safety related function. Such actuators are denoted Class 1E and must be qualified according to IEEE-382 “Standard for Qualification of Actuators for Power-Operated Valve Assemblies with Safety-Related Functions for Nuclear Power Plants” which states that a Class 1E Actuator is essential to emergency reactor shutdown, containment isolation, reactor core cooling, and containment and reactor heat removal, or otherwise essential in preventing significant release of radioactive material to the environment. Qualification of these actuators involves type testing where one or several test specimens that adequately represent and span the entire represented fleet undergo rigorous testing commensurate with expected service. Then, for each application, an evaluation is performed to show how specific loading is enveloped with margin by the testing. IEEE-382 is a specific application of the more general IEEE-323 “Standard for Qualifying Class 1E Equipment for Nuclear Power Generation Stations” containing general requirements applicable to all Class 1E equipment; then, the rules of IEEE-323 add useful clarification to those of IEEE-382.

This paper describes actual type testing of a gas-hydraulic actuator where planned levels were not reached at all times for every test due to test apparatus limitations and shows that the resulting intermittently off target test levels need not envelope loading for all times compared to specific applications. IEEE-382 requires an evaluation showing that test conditions meet specific service conditions plus acceptable margin; however, demonstrating that margin also exists in the range of achieved test levels demonstrates that specified service conditions are adequately included even though specified levels are not enveloped at every time or frequency due to the test apparatus limit anomalies. One practical example is given that logically compares the achieved seismic test levels with a sample required load case for a line mounted valve assembly. Another example compares results from a simulated design basis environmental accident event involving high temperature steam with a sample expected event curve. Rather than compare test and application level by level and curve by curve, the physical effect of the loading, such as stress level, is compared between the test specimen and the application. It is concluded that test levels need not envelope requirements at every point if it can be shown and documented that important physical aspects including stress level, deflection magnitude, absorbed vibration cycles, and energy involvement are enveloped with the required margin.
The Mechanical Characteristics and Sealing Performance Evaluation of Bolted Pipe Flange Connections With Metallic Flat Gaskets Subjected to Internal Pressure
Authors: Kondo Koji , Sato Koji , Takahashi Satomi , Sawa Toshiyuki
Published: December 2016

Bolted pipe flange connections with metallic gaskets have been used under higher pressure as well as higher temperature. However, a few researches on the mechanical characteristics in connections with metallic gaskets have been carried out. It is necessary to examine the mechanical characteristics such as the contact gasket stress distributions which govern the sealing performance, the deformation of the metallic gaskets, changes in axial bolt forces and the hub stress under higher pressure and temperature. In the present paper, the objectives are to examine the changes in axial bolt forces, the hub stress and the contact gasket stress distributions and the sealing performance of the pipe flange connections with metallic flat gaskets. Firstly, the mechanical characteristics of the connections under higher pressure are analyzed using FEA. Then, experiments were carried out to measure the load factor, the hub stress and the leak rate (the sealing performance). The relationship between the average contact gasket stress and the leak rate was measured using platen device at room temperature. The FEA results are fairly coincided with the experimental results. It is shown that the leak rate decreases as the contact gasket stress increases and when the plastic deformation of gaskets occurs, the sealing performance increases. The leak rate was measured in the range of 10−4∼10−7 [Pa·m3/s]. It is found that the sealing performance increases as the gasket width increase in the elastic deformation range while it is independent of the gasket width when the plastic deformation occurs. The effect of temperature on the mechanical characteristics of the connection is also examined. The FEA results are in a fairly good agreement with the experimental results. It is found that the sealing performance increases as the temperature increases. In addition, a method how to determine the bolt preload for increasing the sealing performance is proposed.
Computational Simulation for Evaluation of Food Softening Treatment Vessel Using Underwater Shockwave
Authors: Higa Yoshikazu , Shimojima Ken , Iyama Hirofumi , Higa Osamu , Takemoto Ayumi , Itoh Shigeru , Yasuda Atsushi
Published: December 2016

To clarify the characteristics of the shock wave propagation in food and treatment food vessel, the finite element models of the food, surrounding water, source of high-pressure and its vessel were developed using commercial finite element software HyperWorks (Altair®) RADIOSS®.

By conducting a series of numerical simulations, the pressure distribution in the foods has been observed. From a comparison between computational results and experimental ones corresponding to food hardness using creep meter, it is also revealed that the food softening treatment is highly dependent on the incident shockwave and the reflected one.
A Lagrange-Projection-Like Numerical Scheme for Mixed Acoustic-Convective Two-Phase Flows
Authors: ten Eikelder Marco F. P. , Daude Frédéric , Koren Barry
Published: December 2016

The computation of compressible two-phase flows with the Kapila five-equation model is studied. In the model (fast) acoustic waves and (slow) transport waves occur. In this paper a splitting-based Lagrange-projection-like numerical scheme for the Kapila five-equation model is introduced to decouple these physical phenomena. This approach is based on a Lagrange-projection method for the gas dynamics equations. The decoupling leads to two submodels which are alternately solved to approximate the solution of the full model. The acoustic submodel is cast into an almost conservative form and is solved using an HLLC-type Riemann solver. A classical upwind scheme is used for the transport part. The method allows for a general equation of state. Numerical computations are performed for two-phase shock tube problems, including a mixture problem. The results are in good agreement with reference results.
On Piping Vibration and Practical Measures for Preventing Vibration-Related Damage
Authors: Jansson Lennart G. , Zeng Lingfu , Börjesson Alexander
Published: December 2016

This paper continues our recent discussion on piping vibration and vibration-related damage. Two key issues are addressed in both analytical and experimental aspects: (1) vibration properties and their identification; (2) damage mechanisms caused by vibration and their prevention. Practical approaches for identifying vibration properties and practical measures for preventing vibration damages are overviewed. An empirical approach, which estimates a “vibration susceptibility” parameter prior to installation of a piping system, and for planning post-installation vibration recording activities, is described and studied numerically and experimentally. This approach is based on “theoretic predictions” of “critical” sections of a piping system, namely the sections most sensitive to vibration. It utilizes thereafter an option in a commercial piping program, which serves as a screening tool for determining “potentially-large” alternating stresses. Combined with knowledge of typical vibration sources, this is a cost effective way for preventing vibration damages and for forming a base for controlling actual vibrations in operation of plant, especially for closed premises. Examples are given to exemplify vibration risk.
Overview of Aging Management Program for CANDU Feeders: Canadian Regulatory Perspectives
Authors: Eom Seyun , Liu Sue , Jin John
Published: December 2016

Fitness for Service of CANDU feeder piping has been maintained through the feeder specific Aging Management (AM) Plan, which is called feeder Life Cycle Management Plan (LCMP), implemented by Canadian CANDU licensees. The CNSC REGDOC-2.6.3 describes aspects to be addressed to meet the nine attributes of an effective Aging Management Program (AMP). The LCMP was developed, along with Feeder Fitness for Service Guidelines (FFSG), through a comprehensive industry wide feeder integrity project, called Feeder Integrity Joint Project (FIJP), which had been carried out from 2003 to 2012. The LCMP, FFSG and Periodic Inspection Program (PIP) form the main elements of the AMP to maintain the Fitness for Service of feeder pipes which experience pipe wall thinning due to flow accelerated corrosion (FAC) and the other types of degradations. The effectiveness of the AMPs is continuously monitored through periodic in-service inspections. This paper describes the feeder AMP, from a regulatory perspective, against the nine attributes required in REGDOC-2.6.3.
Reduction of Fugitive Emissions From Bolted Flanged Connections by Using PTFE Blended Gasket
Authors: Kobayashi Takashi , Sato Koji , Muramatsu Akira , Sawa Toshiyuki
Published: December 2016

Gasket is the key element which determines the tightness of bolted flanged connection. PTFE blended gaskets which have recently been developed and come onto the market have a superior sealing performance as well as the chemical and temperature resistances and can contribute to reduce fugitive emissions. This paper deals with the sealing behaviors of the PTFE blended gasket and the tightness of a bolted flanged connection in which the gasket is used. The gasket is mainly composed of PTFE and graphite and has a high tightness and heat resistance up to 300 degree C. The creep characteristic is improved by the graphite filler.

In this paper, the estimation method of the tightness of bolted flanged connections based on the sealing behavior of gasket is demonstrated. The estimated results are validated by experiments using a flange connection.

It is shown that the leak rate below the tightness class 4 defined in the Room Temperature Tightness Test (ROTT, Pressure Vessel Research Council) can be obtained using the PTFE blended gasket.
Damage Characterization of Heat Resistant Steels After Long Service in Reforming Plants
Authors: Alvino Antonello , Antonini Alessandra , Lega Daniela , Mennuti Canio , Tonti Andrea
Published: December 2016

ASTM A 297 grade HP steels are widely employed for radiant tubes in reforming furnaces: this class of heat resistant alloys shows high creep and corrosion resistance, ensuring good performances in extreme pressure and temperature conditions. The typical microstructure of such materials is an austenitic matrix surrounded by a network of interdendritic carbides, which contain chromium and other carbide forming elements, namely Nb, Ti, W, Zr and Y.

During long service life, these high strength materials may suffer aging or even severe damage, especially when process conditions allow coke deposition, or maintenance procedures are not carried properly.

Service aging can be summarized, for HP steels, in terms of microstructure degradation: coalescence and coarsening of interdendritic precipitates, precipitation of secondary carbides in the austenite matrix and transformation of niobium-rich carbides in the G-phase silicide are the typical phenomena occurring on the microstructure of these alloys during service. Carburization can also occur in radiant tubes, since their inner wall side is exposed to hydrocarbon-rich process fluids: carbon diffuses into the metal matrix, causing massive precipitation of chromium-rich carbides. The alloy corrosion resistance is then reduced, resulting in surface attack, cracks development and a general wastage of the material. Furthermore, the high temperatures, which tubes are exposed to, can also induce creep, especially if a local tube overheating occurs: cavities and microcracks, mainly localized at precipitates, are the typical evidences of creep damage on HP steels.

The present work is aimed on the damage characterization of several radiant tubes in HP alloys, after long term service aging in reforming plants. We employed optical and electron microscopy, EDX elements mapping and mechanical tests, in order to characterize and evaluate the various damages affecting the alloys.

Microstructure evolution has been detected in all the analyzed tubes, but we found that such a phenomenon was strictly influenced by the chemical composition of each alloy, so that in presence of small amounts of titanium and tungsten, the chemical evolution of the secondary phases was appreciably contained. Creep also was observed in all the investigated tubes and its extent was found to be related to both alloy composition and process conditions. These latter have assumed to be the main driving factor for carburization, since we observed that slight differences in temperature, pressure, chemical composition of the process fluid and tube maintenance dramatically conditioned the performances of each tube. Massive precipitation and material degradation, in fact, were found in some cases, but, on the other side, no appreciable evidence of carburization damage was observed on other cases.
PWR Effect on Crack Initiation Under Equi-Biaxial Loading Development of the Experiment
Authors: Perez G. , Gourdin C. , Courtin S. , Le Roux J. C.
Published: December 2016

Fatigue lifetime assessment is essential in the design of structures. Under-estimated lifetime predictions may generate overly conservative usage factor values and hence result in unnecessary in-service inspections.

In the framework of upgrading the fatigue design rules (RCC-M, RCC-MRx), the uniaxial reference fatigue curve was altered by taking into account effects like: Multiaxiality, Mean stress or strain, Surface roughness (polished or ground), Scale effect, Loading History...

In addition to this effect, Environmentally Assisted Fatigue is also receiving nowadays an increased level of attention.

To formally integrate these effects, some international codes have already proposed and suggested a modification of the austenitic stainless steels fatigue curve combined with a calculation of an environmental penalty factor, namely Fen, which has to be multiplied by the usual fatigue usage factor.

The aim of this paper is to present a new device “FABIME2E” developed in the LISN in collaboration with EDF and AREVA. These new tests allow quantifying accurately the effect of PWR environment on semi-structure specimen. This new device combines the structural effect like equibiaxiality and mean strain and the environmental penalty effect with the use of PWR environment during the fatigue tests.
Hydraulic and Pneumatic Pressure Cycle Life Test Results on Composite Reinforced Tanks for Hydrogen Storage
Authors: de Miguel Nerea , Mair Georg , Acosta Beatriz , Szczepaniak Mariusz , Moretto Pietro
Published: December 2016

Current standards governing the design, qualification and in-service inspection of carbon fibre composite cylinders do not facilitate to optimise cylinder design. The requirements have been adapted from standards for metallic cylinders and cannot easily quantify the degradation processes in composite materials. In this article, the results of hydraulic and hydrogen pressure cycle life tests performed on composite reinforced tanks with a metal liner (type 3) and with a high density polymer liner (type 4) are shown. Moreover, the degradation measured by means of residual strength of the tanks after the cycling tests have been compared. It has been found that the most critical aging for metal based composite cylinder is the gaseous cycling while type 4 designs seem to be more sensitive to hydraulic cycling at high temperature.
Production of Rice Powder Milling Flour Device and Characterization by Numerical Simulation
Authors: Higa Osamu , Shimojima Ken , Higa Yoshikazu , Takemoto Ayumi , Itoh Shigeru , Yasuda Atsushi , Iyama Hirofumi , Watanabe Toshiaki
Published: December 2016

Rice powder is of interest in Japan, because it can be processed into various foods. However, conventional methods of manufacturing rice-powder generate heat when crushing the rice. National Institute of Technology, Okinawa College (ONCT) has been developing a pressure vessel for producing rice powder using underwater shock waves. The merits of this process are the dry condition and the lack of heating, and a decrease in the manufacturing cost can be expected, using this method. A power supply for generating the shock waves, a pressure vessel for crushing and, a device for the transportation of the rice were developed. The amount of flour that could be milled by the first prototype device was approximately 450g per hour. Then, the pressure vessel was improved to increase the rate of milling. Toward achieving this target, the characteristics of rice processing using shock waves were evaluated. First, a shock wave crushed the rice, which was trapped in transparent acrylic blocks. At the same time, the transmitted shock wave was observed using a high speed camera. From the result of the observation, the speeds of the wave passing through the acrylic blocks and rice was calculated. A linear relationship between the shock wave velocity (Us) and particle velocity (Up) in a material has been empirically found. The propagation of a shock wave in the pressure vessel was calculated by computer simulation. Moreover, a cylindrical pressure vessel with an internal diameter of 150mm was developed. Silicone hoses are installed in the pressure vessel, and the rice passes through in the hoses. The shock wave is generated by the electrical collapse induced by supplying a high voltage to the gap between electrodes in the center of the vessel. The rice is milled into flour by these phenomena, and rice is continuously supplied to the pressure vessel by a classification device and the transport device. The amount of flour milled per hour was verified experimentally.
Numerical Simulation of Cavitating Flow in a Globe Valve: Comparison of OpenFoam and CFX
Authors: Rodriguez Calvete Daniel , Gosset Anne , Pierrat Daniel , Couzinet Anthony
Published: December 2016

The efficiency of control valves operating with liquids is highly conditioned by the occurrence of cavitation when they undergo large pressure drops. For severe service control valves, the subsequent modification of their performance can be crucial for the safety of an installation. In this work, two CFD codes, OpenFoam [1] and Ansys-CFX, are used to characterize the flow in a globe valve, with the objective to compare their capabilities in solving cavitating flows in complex 3D geometries. In both codes, an Homogeneous Equilibrium approach is adopted, and phase change is modeled with a similar cavitation model. It is found that both solvers predict correctly the location of vapor cavities, but tend to underestimate their extension. The flow rate is correctly calculated, but in strong cavitating regimes, it is affected by the underprediction of vapor cavities. The force acting on the stem is found to be more sensitive to the computation parameters.
Integrated Structural Analysis of Composite Pressure Vessels: A Design Tool
Authors: Multhoff Jörg B.
Published: December 2016

The growing interest in gas storage for mobile applications leads to a rising demand for light-weight composite pressure vessels. These are comprised of multiple interacting parts: composite overwrap, liner and boss. The composite overwrap is a multi-layered structure with anisotropic properties that exhibits complex deformation and failure characteristics. The behavior of this structure is unintuitive and can only be understood using thorough analysis. A variety of analysis techniques, ranging from simple netting analysis to detailed finite element analysis, are available. Finite element analysis is applied less often than may be expected due to the high effort for modeling, data preparation and result interpretation. Frequently, manufacturers rely on trial and error approaches to solve the design challenge. Analysis is only used as required to verify the final design. This may result in suboptimal designs. Based on ten years of experience in design and analysis of composite pressure vessels, a tool chain is presented that integrates filament winding simulation and finite element analysis in an automated and efficient manner. This facilitates the understanding of the complex behavior of composite pressure vessels and drives an iterative design-by-analysis process.
A Study of Stresses in Cylindrical Shells Having Tapped Holes Parallel to the Axis of the Cylinder
Authors: Chandiramani Dipak K. , Gopalakrishnan Shyam , Mathkar Ameya
Published: December 2016

Clause UG-27 of ASME Section VIII Division 1 [1] provides rules for calculating the thickness of shells under internal pressure. Mandatory Appendix-2 of Code [1] provides rules for design of bolted flanged connections.

In certain high pressure and high thickness pressure vessels having a cylindrical shell with bolted cover flange, Manufacturers avoid a separate end flange welded to the shell, as the construction becomes bulky. Instead of the same, Manufacturers provide tapped holes in shell wall parallel to axis of the cylindrical shell. The cover is directly bolted to these tapped holes provided in the shell.

This type of construction may be economical as compared to welding a conventional flange to the end of the shell. However this type of construction is not covered in the Code [1].

When such tapped holes are provided in the cylindrical shell, generally the total metal thickness provided at the tapped hole location meets UG-27 requirement of the Code [1]. However due to the tapped holes, the thickness from inside surface of vessel to inside surface of tapped hole is less than the required thickness of UG-27.

It is therefore required to analyze the stresses due to these tapped holes in the shell thickness to ensure that Code [1] allowable stresses are not exceeded.

The work reported in this paper was undertaken to determine the effect of internal pressure on the stresses in a cylindrical shell having tapped holes parallel to axis of the cylindrical shell.
Issue of Application for the Pre-Cracked Charpy Specimens to Estimate WWER-1000 RPV Metal Embrittlement
Authors: Revka Volodymyr M. , Chyrko Liudmyla I.
Published: December 2016

In this study the analysis of fracture toughness test data has been performed in terms of estimation of the proper T0 value for several WWER-1000 RPV materials in unirradiated condition. The surveillance test data for the standard and reconstituted specimens were included in the analysis. It was found that a reference temperature T0 for reconstituted specimens is 31°C higher on average in comparison to the standard specimens. The possible reason is a high level of the stress intensity factor Kmax during the cycle at the stage of completion of crack tip sharpening for standard specimens.

Furthermore, the Charpy impact and fracture toughness test data for standard and reconstituted specimens have been compared considering the known relationship between the reference temperature T0 and the transition temperature T28J which corresponds to the Charpy energy level of 28 J.

Another objective of this study was to compare the RPV metal embrittlement rate for the two reactor pressure vessels using surveillance test data from standard and reconstituted fracture toughness specimens. The analysis has shown that test data for the reconstituted specimens is consistent with the test data for the standard specimens with regard to the embrittlement rate.
Comparison of Seismic Design Provisions Using ASCE 43 With Conventional Design Based on ASCE 7 Seismic Loads
Authors: Houston Thomas W. , Mertz Greg E. , Maham Andrew
Published: December 2016

One graded approach for the design of nuclear facilities would design high hazard facilities to meet the provisions of ASCE 43 while low hazard facilities would be designed as conventional structures based on the seismic loading and design criteria in ASCE 7. In structures with an intermediate hazard it is not immediately obvious which standard provides a more conservative design. This paper presents a case study that compares the performance of an intermediate hazard structure with ASCE 7 seismic loading and criteria to the target performance goals described in ASCE 43 and DOE-STD-1020.

The purposes of seismic design associated with ASCE 7 are; 1) to provide minimum design criteria for structures appropriate to their primary function and use considering the need to protect the health, safety, and welfare of the general public by minimizing the earthquake-related risk to life, and 2) to improve the capability of essential facilities and structures containing substantial quantities of hazardous materials to function during and after design earthquakes.

Designs developed using the provisions of ASCE 7 are targeted to a collapse prevention limit state probability of 1% in 50 years. The goal of the earthquake provisions in ASCE 43 is to ensure that high hazard nuclear facilities can withstand the effects of earthquakes with desired performance, expressed as probabilistic Target Performance Goals and various limit, or damage, states. These Target Performance Goals range from 1×10−4 to 1×10−5 with limit states ranging from essentially linear response to short of collapse.

There are requirements invoked by ASCE 7 that are different than the requirements of ASCE 43 which prevents a direct computation of performance based on comparing the seismic demand levels required by each standard. These differences include the use of building R values in ASCE 7 compared to component specific Fu values in ASCE 43, the use of different analyses methods, ASCE 7 upper bound limits on seismic forces for some components, the limitations on framing system types, among others. The effect of these differences on the performance achieved between the two standards is evaluated for the design of a reinforced concrete shear wall structure that is representative of the types of structures used in nuclear facilities.
Evaluation of Ultrasonic Phased-Array for Detection of Planar Flaws in High-Density Polyethylene (HDPE) Butt-Fusion Joints
Authors: Prowant Matthew S. , Denslow Kayte M. , Moran Traci L. , Jacob Richard E. , Hartman Trenton S. , Crawford Susan L. , Mathews Royce , Neill Kevin J. , Cinson Anthony D.
Published: December 2016

The desire to use high-density polyethylene (HDPE) piping in buried Class 3 service and cooling water systems in nuclear power plants is primarily motivated by the material’s high resistance to corrosion relative to that of steel alloys. The rules for construction of Class 3 HDPE pressure piping systems were originally published as an alternative to the American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME BPVC) in ASME Code Case N-755 and were recently incorporated into the ASME BPVC Section III as Mandatory Appendix XXVI (2015 Edition). The requirements for HDPE examination are guided by criteria developed for metal pipe and are based on industry-led HDPE research and conservative calculations.

Before HDPE piping will be generically approved for use in U.S. nuclear power plants, the U.S. Nuclear Regulatory Commission (NRC) must have independent verification of industry-led research used to develop ASME BPVC rules for HDPE piping. With regard to examination, the reliability of volumetric inspection techniques in detecting fusion joint fabrication flaws against Code requirements needs to be confirmed. As such, confirmatory research was performed at the Pacific Northwest National Laboratory (PNNL) from 2012 to 2015 to assess the ability of phased-array ultrasonic testing (PAUT) as a nondestructive evaluation (NDE) technique to detect planar flaws, represented by implanted stainless steel discs, within HDPE thermal butt-fusion joints. All HDPE material used in this study was commercially dedicated, 305 mm (12.0 in.) nominal diameter, dimension ratio (DR) 11, PE4710 pipe manufactured with Code-conforming resins, and fused by a qualified and experienced operator. Thermal butt-fusion joints were fabricated in accordance with or intentionally outside the standard fusing procedure specified in ASME BPVC. The implanted disc diameters ranged from 0.8–2.2 mm (0.03–0.09 in.) and the post-fabrication positions of the discs within the fusion joints were verified using normal- and angled-incidence X-ray radiography. Ultrasonic volumetric examinations were performed with the weld beads intact and the PA-UT probes operating in the standard transmit-receive longitudinal (TRL) configuration. The effects of probe aperture on the ability to detect the discs were evaluated using 128-, 64-, and 32-element PA-UT probe configurations. Results of the examinations for each of the three apertures used in this study will be discussed and compared based on disc detection using standard amplitude-based signal analysis that would typically be used with the ultrasonic volumetric examination methods found in ASME BPVC.
Characteristics of Commercially Available Integrally Reinforced Weld-On Fittings
Authors: Becht Charles , Paulin Anthony , Stonehouse Mark , Edwards Donald , Cates John
Published: December 2016

Integrally Reinforced Weld-On Fittings (IRWO Fittings) are used often as branch connections in piping systems. Original taper-bore designs are from Bonney Forge, and original straight-bore designs are from WFI. Numerous other manufacturers now fabricate these fittings under various names, but all Markl-type Code testing of these fittings was performed on either the Bonney Forge or WFI geometries. The original IRWO fittings were not intended to be used in large size-on-size configurations and were designed with various area replacement strategies (50% or 100% reinforcement in the fitting) and were based on an extensive series of burst tests. Stress Intensification Factors (SIFs) were developed by extending existing ASME Section III [3] Equations for fabricated tees after several series of tests were conducted, (See WRC 329 [2]). Taper-bore designs were developed to facilitate handling during fabrication, but inadvertently also produced larger footprints which reduced stress intensification factors but introduced installation issues that were all but eliminated with the straight thru bore design, (i.e. with the taper bore design, should the hole in the run pipe fit the taper ID or the branch ID?) IRWO tests on partially welded-out geometries and on alternate geometry designs are presented along with finite element (FEA) results that indicate where additional testing is needed and where the pipe designer should exercise additional caution.