bluuebunny/crossref_metadata_2025 huggingface dataset:
Overview of PSA for the UK ABWR Generic Design Assessment
Authors: Hirokawa Naoki , Ishiwatari Yuki , Taniguchi Daisuke , Hisamochi Kohei
Published: October 2018

A Probabilistic Safety Assessment (PSA) was provided as an integral part of the safety case for the United Kingdom Advanced Boiling Water Reactor (UK ABWR) Generic Design Assessment (GDA). The main objectives of PSA for GDA is to provide a demonstration of the compliance, for a single unit UK ABWR, with numerical risk targets defined in the UK Safety Assessment Principles (SAP) and to support the “As Low As Reasonably Practicable” (ALARP) assessment. This content of this paper includes:

• An overview of the UK ABWR PSA

• Identification of the PSA scope

• PSA model development to compare with numerical risk targets and inform design and operational features

• Illustration of PSA results, e.g., Core Damage Frequency (CDF), Large Release Frequency (LRF) and Large Early Release Frequency (LERF)

• Peer reviews

• Use of PSA in ALARP assessment
Numerical Study on Effect of Pressure on Behavior of Bubble Coalescence by Using CMFD Simulation
Authors: Ono Ayako , Suzuki Takayuki , Yoshida Hiroyuki
Published: October 2018

The mechanism of critical heat flux (CHF) for higher system pressure remains to be clarified, even though it is important to evaluate the CHF for the light water reactor (LWR) which is operated under the high pressure condition. In this study, the process of bubble coalescence was simulated by using a computational multi-fluid dynamics (CMFD) simulation code TPFIT under various system pressure in order to investigate the behavior of bubbles as a basic study. The growth of bubbles was simulated by blowing of vapor from a tiny orifice simulating bubble bottom. One or four orifices were located on the bottom surface in this simulation study. The numerical simulations were conducted by varying the pressure and temperature.
Evaluation Method of Response Reliability During an Accident and its Applicability to Fast Reactor Plants
Authors: Suzuki Masaaki , Demachi Kazuyuki , Takaya Shigeru , Chikazawa Yoshitaka
Published: October 2018

In this study, we develop new indices that evaluate the response capability — response margin and response reliability — of a nuclear power plant in case of occurrence of a severe accident by considering the ability of the nuclear power plant to recover system safety functions, which may have been affected by the accident, to the minimum safety values. Further, we demonstrate a specific evaluation procedure for our proposed indices. While performing the evaluation, we consider margins with respect to a minimum safety function level and a time constraint along with their temporal changes. Additionally, for a simplified fast reactor (FR) plant model, we conduct a trial assessment of the recovery capacity of the system to ensure system safety based on the concept of new indices. Further, the applicability of the response reliability evaluation method to FR plants is discussed based on the viewpoints of reflecting the characteristics of each reactor type.
Simulation of JAERI Downcomer Effective Water Head Experiments With WCOBRA/TRAC-TF2
Authors: Kobelak Jeffrey R. , Liao Jun , Ohkawa Katsuhiro
Published: October 2018

During the reflood phase of a postulated large break loss-of-coolant accident (LBLOCA), the liquid head in the reactor vessel downcomer provides the driving force to reflood the core. Since the reflood rate is a function of the downcomer inventory, the calculation of the downcomer liquid inventory is critical in simulating the reflood phase of a postulated LBLOCA accident in a pressurized water reactor.

Since the reactor coolant system pressure decreases rapidly after the onset of a LBLOCA transient, the walls surrounding the downcomer become superheated for the duration of the transient. The Japan Atomic Energy Research Institute (JAERI) downcomer effective water head test facility was designed to study boiling and steam-water interaction in the reactor vessel downcomer under prototypical reflood conditions. A number of tests were conducted at this facility with varying degrees of wall superheating (among other things) that cover the expected degree of superheating in a pressurized water reactor. The wall superheating achieved at the JAERI facility is greater than that of other large-scale facilities that are typically simulated to validate thermal-hydraulic system codes.

WCOBRA/TRAC-TF2 is the thermal-hydraulic system code utilized in the FULL SPECTRUM™ LOCA (FSLOCA™) evaluation model (EM). The ability of the WCOBRA/TRAC-TF2 code to predict phenomena occurring in the reactor vessel downcomer during the reflood phase of a postulated LBLOCA has been previously validated. However, only limited wall superheating was present in the existing validation basis. As such, two experiments conducted at the JAERI downcomer effective water head test facility are simulated to provide additional information on the capability of WCOBRA/TRAC-TF2 to predict the liquid inventory in the reactor vessel downcomer during the reflood phase of a postulated LBLOCA. The code captured all the trends observed in the experimental data for both Run 115 and Run 121. The various collapsed liquid levels tended to be well-predicted or under-predicted by the code after the initial simulated accumulator injection period.
Two Stage Data Driven V&V for an Agile Thermohydraulic Analysis Method
Authors: Bennett Christopher , Adams Scott , Alexander Nick
Published: October 2018

Rolls-Royce has embarked on a Small Modular Reactor (SMR) design programme, which is developing a safe, deployable and affordable Nuclear Power Plant. An element of the work undertaken is the determination of the performance of nuclear reactor plants through the application of thermal hydraulic analysis methods. These methods are used throughout the product lifecycle; beginning with exploring the performance potential of design options and ultimately providing analysis to support the safety justification.

To provide performance analysis at the earliest stages of design it is imperative to have a flexible analysis method that evolves alongside the design process while being able to inform the system architects at each phase. To achieve this goal an analysis method has been developed that allows for varying plant configurations with adjustable plant component geometries. The process of updating each of the plant component subsystem models has been automated and linked with an overarching database that allows system designers to directly update geometrical parameters.

This approach to early concept design has led to the practice of two-stage verification and validation. The first stage is the traditional understanding of V&V, the verification of the models and supporting scripts through the use of a predefined rigorous test suite which encompasses unit tests through to full system integration tests.

The second stage is data verification and validation, as the method has the ability to constantly update based on data input the verification of this input data is paramount. The design data is hierarchical, which in addition to a mean and an uncertainty distribution, requires knowledge of a transfer function.

Each item of data is owned by the department that is the expert in that field, for example the steam generator dimensions are owned by the components team. It is the responsibility of each of the data owners to verify their data and ensure that any transfer functions are implemented correctly.

As data is used in a cross discipline setting it requires a central storage location, this is the Master Parameter List (MPL). This repository defines the data, its format, its owner, and the last time it was updated among other things. This repository is the single point of truth for every data item used in analysis.

The aim of this paper is to demonstrate the way in which a flexible analysis method is created along with the framework that provides confidence in the analysis results through a two phase data driven V&V approach.
Application of Miniaturized Experiments for Constitutive Modeling of Creep Relaxation of a Novel Textured Gasket Product
Authors: Gordon Ali P. , Albury John , Lopez Matthew , Tasci Evren , Poust Zachary , Pitolaj Steve , Drago Jim , Nichols Paul
Published: October 2018

The material attributes that are fundamental for developing a candidate textured, ceramic-filled PTFE gasket, such as texture style/dimensions, filler material, thickness and so on, create a set of potential combinations that are not practical to experimentally characterize at the component-level one-by-one. Optimizing gasket performance, however, is essential to the operation of bolted connections associated with pressurized vessels that transfer media from one location to another. Gaskets are essential for these systems since they confer high levels of leak mitigation across a range of operating environments. A balance of both compressibility and sealability must be displayed in an optimal candidate gasket to be subjected to aggressive operating conditions. A novel textured PTFE material (termed textured) characterized using a miniaturized test platform. This new-to-market viscoelastic material features a dual-face, raised honeycomb pattern. Experiments on both flat (termed Flat) and textured are used to identify viscoelastic constitutive model constants associated with Burger theories. Considering that the test platform contains an elastic bolt that is tightened to a prescribe torque level, the gasket is subjected to creep relaxation. Test results on the small samples contribute to constitutive modeling. The influence of parameters such as filler material selection, torque level, dwell period, etc. are presented.
Effect of Crack Orientation on Fracture Behaviour of Wire + Arc Additively Manufactured (WAAM) Nickel-Base Superalloy
Authors: Seow Cui Er , Coules Harry , Khan Raja
Published: October 2018

In this study, the effect of crack orientation on the fracture behaviour of two compact tension C(T) specimens extracted from a Wire + Arc Additively Manufactured (WAAM) wall made from Inconel (IN) 625 nickel-base superalloy was investigated. Both specimens had different levels of ductile tearing but their load vs. crack mouth opening displacement (CMOD) behaviour was relatively similar. The total-and-elastic strain distribution around a crack tip was measured in both specimens using Digital Image Correlation (DIC) and neutron diffraction respectively. The results show that the strain distribution and deformation around the crack tip are different in the two directions. In the specimen with crack orientation parallel to the build direction, banding was observed in both the total strain maps and the deformation pattern. Neutron diffraction measurements on this specimen also showed non-monotonic elastic strain evolution, suggesting the occurrence of intergranular load shedding mechanisms. These were not observed in the specimen with crack orientation perpendicular to the build direction. Electron Backscatter Diffraction (EBSD) maps show that the WAAM IN625 material is strongly textured with coarse columnar grains elongated in the build direction. The effect of microstructure has been correlated with the differences in strain distribution in the two specimens.
A Basis for Applying Elastic Perfectly-Plastic Design Methods to Cyclic Softening Materials
Authors: Messner M. C. , Wang Yanli , Jetter R. I. , Sham T.-L.
Published: October 2018

Design approaches using elastic perfectly-plastic (EPP) analysis have recently been approved as Code Cases for the Section III, Division 5 design of high-temperature nuclear reactor components made from austenitic stainless steel. These methods bound the ratcheting strain and creep-fatigue damage accumulated over the life of a component with a simplified, elastic-perfectly plastic analysis using a special pseudo-yield stress — often not equal to the true material yield stress. The austenitic materials specified in the existing Code cases are cyclic-hardening for all allowable operating temperatures. However, other Section III, Division 5 materials, such as Grade 91 steel, are cyclic softening at expected advanced reactor operating temperatures. This work describes the extension of EPP methods to cyclic softening materials through the use of a postulated saturated material state and softening factors to be applied to the pseudo yield stress. We demonstrate the conservatism of the modified EPP method against a series of inelastic simulations of two bar tests, using a constitutive model that captures work and cyclic softening.
Creep Properties Assessment of Materials by a Small Cantilever Beam Specimen
Authors: Zhuang Fakun , Tu Shantung , Xie Guoshan , Shao Shanshan , Cao Luowei
Published: October 2018

Small specimen creep test techniques have been widely applied in the creep properties assessment of materials for the equipment in-service. In order to acquire the creep data accurately and conveniently, the creep test method with small cantilever beam specimens is proposed. On the basis of Norton-Bailey creep law, analytical creep model for the cantilever beam specimen is derived. With this model, the load can be converted to equivalent uniaxial stress and the displacement rate can be converted to equivalent uniaxial strain rate. The creep properties of Cr-Mo steel are assessed by the cantilever beam specimens creep tests. And the creep parameters are evaluated, which are compared to the uniaxial creep parameters. The results show that parameters obtained from the cantilever beam tests correspond reasonably well with those from uniaxial tests. It proves that the primary and secondary creep properties can be assessed by the cantilever beam specimen tests.
Oxygen Impurity Effects on Hydrogen Assisted Fatigue and Fracture of X100 Pipeline Steel
Authors: Ronevich Joseph , San Marchi Chris , Kolasinski Robert , Thurmer Konrad , Bartelt Norm , El Gabaly Farid , Somerday Brian
Published: October 2018

Hydrogen gas accelerates fatigue crack growth and reduces fracture toughness in ferritic structural materials such as pipelines and pressure vessels. The extent to which the crack growth rates are accelerated depends upon environment, mechanical loading conditions, and material. In this work, the effects of loading conditions and environment, specifically oxygen impurities, are examined on an X100 pipeline steel in high pressure hydrogen gas. Fatigue crack growth rates were measured in a gas mixture consisting of nominally 100 ppm O2 in a balance of H2 gas to evaluate the effects of pressure and load ratio (R-ratio) on the manifestation of hydrogen-accelerated fatigue crack growth (HA-FCG). Tests were performed at 21 MPa, 2.1 MPa, and 1.4 MPa and at load ratios of 0.5 and 0.1. The onset of HA-FCG was observed to be dependent on both absolute pressure and load ratio and it will be shown that a critical combination can result in complete mitigation of HA-FCG over the stress intensity factor range (ΔK) examined. Tests were predominantly performed at 10 Hz; however, a single test was performed at 1 Hz which exhibited negligible HA-FCG compared to a test at 10 Hz which did exhibit HA-FCG. Rising load fracture toughness tests were conducted via constant displacement rates to generate J-R curves in both pure H2 and 100 ppm O2 mixed gas. At similar absolute pressures, fracture toughness was measured to be greater in the 100 ppm O2 mixed gas compared to the pure H2. Hydrogen-assisted fracture was completely alleviated at pressures below 2.1 MPa in the 100 ppm O2 mixed gas, in which fracture toughness values were consistent with tests in air.
The Effect of a Low Constraint Geometry on Measured T0 Values for a Nuclear Reactor Pressure Vessel Ferritic Steel
Authors: Rait Geena K. , Davies Catrin M. , Garwood Stephen J.
Published: October 2018

Current requirements for assessing the fracture toughness of reactor pressure vessel (RPV) ferritic steels are potentially overly conservative due to the employment of high constraint geometries such as compact tension (C(T)) or single edge notch bend, SEN(B), specimens for material testing. These high constraint conditions are not representative of the actual conditions experienced by the RPV in service. If this conservatism could be reduced, more appropriate predictions for RPV lifetime extension could become a possibility. In this study, a known low constraint geometry, single edge notch tension, SEN(T), has been tested alongside the higher constraint SEN(B) specimen in order to compare measured T0 and fracture toughness values for both cases. Finite element analyses have also been conducted for both geometries in order to measure T-stress and calculate Q values thereby allowing quantification of the level of constraint for both geometries. Eight SEN(B) and eight SEN(T) specimens were tested with dimensions 24 × 254 × 96 mm and 20 × 20 × 200 mm, respectively.

Testing was conducted at sub-zero temperatures, as close to the T0 as possible, in accordance with the guidelines presented in ASTM E1921-17a. Contrary to expected behaviour the SEN(T) specimen indicated a higher (less negative) T0 then the SEN(B) specimen. The reason for these results are explored in this paper.
A Quantitative Assessment of Microstructural Evolution for Grade 91
Authors: Che Chang , Qian Gong , Yang Xisheng
Published: October 2018

China has the most supercritical boilers in the world. Grade 91 steels are widely used for high temperature components of supercritical boiler. During high temperature service, microstructural evolution of Grade 91 steel may affect the mechanical properties, including creep strength. However, there are very few studies on quantitative assessment of microstructural evolution for Grade 91 steel, especially on precipitates content.

In this article, microstructural evolution of Grade 91 was studied. A quantitative assessment of microstructure evolution was given during long-term creep, focusing on the precipitated phase content in Grade 91 steel. The results show, the precipitates content of Grade 91 steel has a corresponding relationship with creep damage.
Factors Affecting the Oxidation and Carburisation Behaviour of an Austenitic Stainless Steel Used in the UK Advanced Gas-Cooled Reactors
Authors: Palkó S. , Scenini F. , Ainsworth R. A.
Published: October 2018

A significant number of stainless steel components within the boilers of the UK advanced gas-cooled reactor (AGR) plants are subjected to oxidation, carburisation and other changes in the underlying microstructure of the material during operation. This results from exposure to the pressurised CO2-based primary circuit coolant at temperatures from about 500 to 650°C. It is believed that there is a synergistic relationship between the pressurised CO2 coolant environment and creep-fatigue initiation and cracking. Devising and implementing an evaluation methodology to account for oxidation and carburisation to enable conservative lifetime assessments is essential to current and future plant safety. Therefore, the development of a new and fundamental understanding of environmentally assisted degradation and failure mechanisms is required. It has been postulated that the mechanism underlying the initiation of cracks is carburisation associated with the presence of a duplex oxide layer. In this study, the material-environment interaction for Type 316H stainless steel under simulated AGR conditions has been investigated to increase the understanding of the combined effects of stress, strain and surface preparation, for example, on oxidation and cracking behavior. Experimental data are presented which show that surface deformation promotes the formation of a thin, protective oxide scale, which does not protrude along the grain boundaries, whereas a deformation-free surface leads to the formation of thick duplex oxide layers as well as intergranular oxide penetration. Furthermore, an increased surface hardness due to carburisation has been observed for the undeformed surface only, suggesting that carburisation occurs at an early stage on a chemically treated surface. It is found that when the substrate is plastically deformed and under the effect of active stress, the thin oxide on the mechanically deformed surface can be disrupted, resulting in similar behaviour to a chemically treated surface with no deformation.
Advanced NDE Techniques for Reliable Crack Inspection and Fitness-for-Service Assessments
Authors: Krynicki Joseph W. , Peng Lujian
Published: October 2018

Reliable and accurate NDE (Non-Destructive Evaluation) techniques are required to conduct FFS (Fitness-For-Service) assessments for crack type flaws in equipment. FFS assessments rely on certain flaw detection and flaw sizing assumptions which can only be provided through NDE. The detection and sizing provided by the NDE work is highly dependent on both inspection methodology (e.g., operator, equipment, and procedure) as well as the specific component and application (e.g., part thickness and geometry, flaw type, damage mechanism, etc.). Therefore, the accurate determination of these detection and sizing assumptions requires thorough consideration, modeling, assessments, and determination by NDE specialists. This paper will describe factors that affect flaw detection and sizing results by NDE, the use of synthetic flaws to assess and improve NDE performance, the verified performance of advanced NDE techniques on natural flaws, and the integration of NDE performance results with FFS assessments.
Environmental Assisted Fatigue and EDF 900 MWe PWRs Fleet: Towards an Exemption of Environmental Effects Consideration for Secondary Circuit Components
Authors: Cuvilliez Sam , Léopold Gaëlle , Métais Thomas
Published: October 2018

Environmentally Assisted Fatigue (EAF) is receiving nowadays an increased level of attention for existing Nuclear Power Plants (NPPs) as utilities are now working to extend their life. In the wake of numerous experimental fatigue tests carried out in air and also in a PWR environment, the French RCC-M code [1] has recently been amended (in its 2016 edition) with two Rules in Probatory Phase (RPP), equivalent to ASME code-cases, “RPP-2” and “RPP-3” [2] [3]. RPP-2 consists of an update of the design fatigue curve in air for stainless steels (SSs) and nickel-based alloys, and is also associated with RPP-3 which provides guidelines for incorporating the environmental penalty “Fen” factor in fatigue usage factor calculations.

Alongside this codification effort, an EAF screening has recently been carried out within EDF DT [4] on various areas of the primary circuit of the 900 MWe plants of the EDF fleet. This screening led to the identification of a list of 35 “sentinel locations” which are defined as areas most prone to EAF degradation process. These locations will be subjected to detailed EAF analysis in the stress report calculations (according to the above-mentioned RCC-M code cases) for the fourth decennial inspection of the 900 MWe (VD4 900 MWe) power plants.

The potential impact of EAF on the secondary circuit components is another question to address in anticipation of the VD4 900 MWe, as they may be considered as class 1 or class 2 equipment for RCC-M application according to the equipment specification. This paper presents the approach proposed by EDF towards an exemption of environmental effects consideration for secondary circuit components. The argument is first based on a review of experimental campaigns led in Japan and France (respectively on fatigue test specimens and at the component scale) which indicate a Dissolved Oxygen (DO) content threshold below which environmental effects are almost inexistent. The (conservative) value of 40 ppb has been selected consistently with NUREG/CR-6909 revision 0 [5]. The second part of the argument is built, on the one hand, on the analysis of the EDF Technical Specifications for Operation (STE) which narrows the scope of the study only to unit outages, and, on the other hand, on the analysis of 5 years of operations of all 900 MWe plants of the EDF fleet (equivalent to 170 reactor-years). It has been shown that the DO content rarely exceeded the 40 ppb threshold in the secondary coolant, and that in this case, the considered locations were not submitted to any fatigue loading.
Evaluation of the Compatibility of High-Strength Aluminum Alloy 7075-T6 to High-Pressure Gaseous Hydrogen Environments
Authors: Ogawa Yuhei , Kim Dain , Matsunaga Hisao , Matsuoka Saburo
Published: October 2018

To develop safer and more cost-effective high-pressure hydrogen tanks used in fuel cell vehicles (FCVs), the metallic materials with the following three key properties, i.e. lightweight, high strength and excellent resistance to hydrogen embrittlement should be explored. In this study, the compatibility of high-strength, precipitation-hardened aluminum alloy 7075-T6 was evaluated according to the four types of mechanical testing including slow-strain rate tensile (SSRT), fatigue life, fatigue crack growth (FCG) and fracture toughness tests in high-pressure gaseous hydrogen environments (95 ∼ 115 MPa) at room temperature. Even though numerous publications have previously reported significant degradation of the mechanical properties of 7075-T6 in some hydrogenating environments, such as moist atmosphere, the understanding with regards to the performance of this alloy in high-pressure gaseous hydrogen environments is still lacking.

In SSRT tests, the alloy showed no degradation of tensile strength and ductility. Furthermore, fatigue life, fatigue crack growth and fracture toughness properties were also not degraded in hydrogen gas. Namely, it was first demonstrated that the material has big potential to be used for hydrogen storage tanks for FCVs, according to its excellent resistance to high-pressure gaseous hydrogen.
Investigation of the Performance of Different Face Milling Inserts to Improve Rough Milling of SA508 Grade 3 Forgings
Authors: Gurdal Ozan , Wright Andrew , Carpenter Charles , Blackmore Michael
Published: October 2018

The selection of cutting tool geometry and cutting conditions plays a major part in the planning of machining operations affecting the productivity. Although there are several classifications used by tool manufacturers, carbide inserts for face milling can be categorised according to their cutting edge angle. In this study, the material removal performance of square, round and high-feed inserts, which all have different cutting edge angles, was investigated through cutting trials conducted without coolant on forged SA508 Gr.3 Cl.2. Predictive tool life models for round and high-feed inserts were developed by means of the response surface methodology and their adequacy was checked through the analysis of variance. Cutting speed versus feed per tooth contour plots are presented against predicted tool life values which facilitate the selection of cutting conditions ensuring desired tool life. The experimental data has demonstrated that using inserts with lower cutting edge angle would significantly improve cycle times especially in the rough milling stage where the surface integrity is not of primary interest. However, it should be taken into account that limitations exist mainly due to the process stability and capabilities of machine tools.
ASME Section XI Appendix L Flaw Tolerance Evaluation of Pressurized Water Reactor Piping Systems to Support Second License Renewal (80-Years Operation)
Authors: Udyawar Anees , Tomes Charles , Carolan Alexandria , Marlette Steve , Meikle Thomas , Bamford Warren
Published: October 2018

One of the goals of ASME Section XI is to ensure that systems and components remain in safe operation throughout the service life, which can include plant license extensions and renewals. This goal is maintained through requirements on periodic inspections and operating plant criteria as contained in Section XI IWB-2500 and IWB-3700, respectively. Operating plant fatigue concerns can be caused from operating conditions or specific transients not considered in the original design transients. ASME Section XI IWB-3740, Operating Plant Fatigue Assessments, provides guidance on analytical evaluation procedures that can be used when the calculated fatigue usage exceeds the fatigue usage limit defined in the original Construction Code. One of the options provided in Section XI Appendix L is through the use of a flaw tolerance analysis.

The flaw tolerance evaluation involves postulation of a flaw and predicting its future growth, and thereby establishing the period of service for which it would remain acceptable to the structural integrity requirements of Section XI. The flaw tolerance approach has the advantage of not requiring knowledge of the cyclic service history, tracking future cycles, or installing systems to monitor transients and cycles. Furthermore, the flaw tolerance can also justify an inservice inspection period of 10 years, which would match a plant’s typical Section XI in-service inspection interval. The goal of this paper is to demonstrate a flaw tolerance evaluation based on ASME Section XI Appendix L for several auxiliary piping systems for a typical PWR (Pressurized Water Reactor) nuclear power plant. The flaw tolerance evaluation considers the applicable piping geometry, materials, loadings, crack growth mechanism, such as fatigue crack growth, and the inspection detection capabilities. The purpose of the Section XI Appendix L evaluation is to demonstrate that a reactor coolant piping system continues to maintain its structural integrity and ensures safe operation of the plant.
Influence of Pressure Vessel Shape on Explosive Forming
Authors: Iyama Hirofumi , Nishi Masatoshi , Higa Yoshikazu
Published: October 2018

The explosive forming is a characteristic forming method. This technique is a metal forming using an underwater shock wave. The underwater shock wave is generated by underwater explosion of the explosive. The metal plate is formed with involving the high strain rate on this technique. In generally, the pressure vessel is used in this method due to the effective utilization of the explosion energy. The underwater shock wave is propagated in water and reflected on inside wall of the pressure vessel. This reflected shock wave is affected on the deformation shape of a metal plate. Therefore, the inside shape of pressure vessel is often changed. In other words, the shape of pressure vessel is changed, the shock pressure distribution on the metal plate and it is possible that final deformation shape of the metal plate is changed. Some numerical simulations and experiments have been carried out to clear the influence of the inside shape of pressure vessel in the explosive forming. This paper is included the results and discussions on the numerical simulation and experiment used those conditions.
The Influence of Material, Hardness, Roughness and Surface Treatment on the Frictional Characteristics of the Underhead Contact in Socket-Head Screws
Authors: Croccolo Dario , De Agostinis Massimiliano , Fini Stefano , Olmi Giorgio , Robusto Francesco , Cavalli Omar , Vincenzi Nicolò
Published: October 2018

The present paper aims at determining the effect of several design and manufacturing parameters on the frictional response of the underhead contact in a bolted joint comprising a socket-head M6 class 12.9 screw. The rationale of the research moves from the need to understand the frictional behavior of screw joints used in machine tools as a means to join roller monoguides with the moving carriages of three-axis tooling units. The experimentation takes into account different underhead materials (Steel, Cast Iron, Aluminum), different roughness levels (Ra = 0.8, 1.6, 3.2), different surface treatments (No treatment, oxidised, DLC), as well as repeated tightening operations. The experimentation has been run by a specifically developed specimen, consisting of two parts: an instrumented sleeve, equipped with a double array of strain gauges capable of sampling both the axial preload and the underhead torque, and interchangeable underhead washers, with an anti-rotation device, whose material and surface treatment are suitably changed among the different sets. The tightening torque is recorded by a digital torque wrench. The collected data are processed by ANoVa tools, to investigate the significance of each factor, as well as related interactions. The friction coefficients associated with the different operating parameters are a useful tool to support the design task of bolted joints.
Evaluation of Deformation and Fracture Behaviors of Nuclear Components Using a Simulated Specimen Under Excessive Seismic Loads
Authors: Kim Jin Weon , Song Ik Hyun , Kweon Hyeong Do , Kim Jong Sung , Kim Yun Jae
Published: October 2018

This study designed a specimen that can simulate deformation and crack initiation in system, structure, and components (SSCs) of nuclear power plants (NPPs) under excessive seismic loads, and conducted ultimate strength tests using this specimen at room temperature (RT) and 316°C. The specimen designed was a compact tension (CT) type with a round notch, and both SA312 TP316 stainless steel (SS) and SA508 Gr.3 Cl.1 low-alloy steel (LAS) were used in the experiment. Displacement-controlled cyclic loads with constant and random amplitudes were applied as input loads for the test. One set of input loads consisted of 20 cycles, and the input amplitudes of load-line displacement (LLD) were determined to induce the maximum elastic stress of 6∼ 42Sm on the specimen, where Sm is allowable design stress intensity. The input LLD had a triangular waveform and was fully reversed for both types of amplitude. During the test, multiple sets of input cyclic loads, with increasing amplitude of input LLD, were applied to the specimen until a crack was initiated. The results demonstrated that the specimen used in this study adequately simulates the deformation and failure behaviors of SSCs under excessive seismic loads. In addition, the samples in both materials failed under cyclic load levels that were several times higher than those of design basis earthquake (DBE). The SA316 TP316 SS specimen had a greater safety margin under excessive seismic loading conditions than SA508 Gr.3 Cl.1 LAS specimen, regardless of test temperature.
Investigations of Very High Cycle Fatigue Behavior of Metastable Austenitic Steels Using Servohydraulic and Ultrasonic Testing Systems
Authors: Daniel Tobias , Boemke Annika , Smaga Marek , Beck Tilmann
Published: October 2018

To investigate the fatigue behavior of metastable austenite steels in the VHCF-regime, high loading frequencies are essential to realize acceptable testing times. Hence, two high-frequency testing systems were used at the authors’ institute: an ultrasonic testing system with a test frequency of 20 000 Hz and also, a servohydraulic system with a test frequency of 980 Hz. In the present study, two different batches of the metastable austenitic stainless steel AISI 347 were investigated.

Fatigue tests on metastable austenitic steel AISI 347 batch A were carried out at an ultrasonic test system at a test frequency of 20 000 Hz, at ambient temperature. Because the test rig acts as a mechanical resonant circuit excited by a piezoelectric transducer the specimen must be designed for oscillation in its vibration Eigenmode at the test frequency to assure maximum displacement at the end and maximum stress in the gauge length center, respectively. For analyzing the deformation behavior during the tests, the change in temperature was measured. Additionally, Feritscope™ measurements at the specimen surface were performed ex-situ after defined load cycles. First results showed a pronounced development of phase transformation from paramagnetic face-centered cubic γ-austenite to ferromagnetic body-centered cubic α‘-martensite. Because formation of α‘-martensite influences the transient behavior and high frequency loadings leads to pronounced self-heating of the material, ultrasonic fatigue tests on metastable austenites represent a challenge in controlling of displacement amplitude and limiting the specimen temperature.

First investigations on metastable austenitc steel AISI 347 batch B using a servohydraulic test system at a frequency of 980 Hz and a temperature of T = 300 °C resulted in no fatigue failure beyond N = 107 cycles in the VHCF-regime. However, only specimens with a low content of cyclic deformation-induced α‘-martensite achieved the ultimate number of cycles (Nu = 5·108).
Investigation on Standards on Hydrogen Cycle of Composite Tanks for Storage of High Pressure Hydrogen
Authors: Du Yan-Nan , Wang Zhen-Bang , Tang Xiao-Ying , Yuan Yi-Wen , Xue Xiao-Long , Jiang Cheng-Jun
Published: October 2018

High pressure hydrogen storage tank is a key component in hydrogen supply systems of the fuel cell vehicles. Composite hydrogen storage tanks own some advantages such as high stiffness, density and strength, and the composite tanks for storage of 70 MPa hydrogen is the hotspot of research. However, composite hydrogen storage tanks have the potential leakage and explosion hazards in the process of using due to the flammable and explosive storage medium. hydrogen cycle test is an important means to detect the macroscopic strength, safety margin, structure design rationality and reliability of composite hydrogen storage tanks. The relevant standard of 70MPa composite hydrogen storage tanks is not yet introduced in China. At present, the european union, Japan and the international standardization organization have formulated the composite hydrogen storage tanks standard or code, which have an important reference for the formulation of the relevant standards in china. In this study, foreign standards related hydrogen cycling test content such as (EU) 406-2010, ANSI HGV 2-2014, ISO CD 19881-2015, SAE J2579-2013 and ECE/TRANS/180-2013 are systematically studied, which could be helpful for the establishment of relevant standards in China and the development of hydrogen cycle test equipment.
Experimental and Numerical Analysis of a Pristine and a Nano-Modified Thermoplastic Adhesive
Authors: Niutta Carlo Boursier , Ciardiello Raffaele , Belingardi Giovanni , Scattina Alessandro
Published: October 2018

In this work, the mechanical properties of two different adhesives compositions have been investigated both experimentally and numerically. The studied thermoplastic adhesives are Hot-Melt Adhesive (HMA). In particular, a pristine and a nanomodified adhesive with 10% in weight of iron oxide have been considered. The adhesives have been subjected to a series of single lap joint (SLJ) tests using adherends made of polypropylene copolymer. As it is well-known, the structural-mechanical behavior of adhesive joints is mostly influenced by the bonding process: thickness of adhesive as well as its application procedures and the surface preparation of adherends are among the most influencing factors. In addition, the mechanical behavior of SLJ test is particularly influenced by the correct alignment of adherends and applied load. These aspects have been investigated, analyzing the experimental results. Moreover, the experimental results have been used to develop a numerical model of the two adhesives. The numerical analysis has been carried out using the commercial software LS-DYNA. Transient nonlinear finite element analysis has been performed to simulate the mechanical behavior of the thermoplastic adhesives. In particular, the cohesive formulations of the elements have been taken into consideration after a careful literature review. In order to set-up and to validate the mechanical properties of the adhesives, the experimental SLJ tests have been simulated. The developed finite element models enable to investigate more complex joint structures where these types of adhesives are used, such as plastic piping systems and automotive applications. Further, the numerical models allow to investigate with higher accuracy and lower time different aspects such as manufacturing and non-linear effects.
CFD Prediction of Safety Valve Disc Forces Under Two Phase Flow Conditions
Authors: Dempster William , Alshaikh Moftah
Published: October 2018

At present there are very few published works on prediction based methods to establish the forces that act on safety valves during two-phase operation. This means that the valve dynamics and resulting opening and closure are uncertain for a wide range of complex flow applications. This paper describes a study whereby a safety valve, primarily developed for the industrial refrigeration sector is investigated for a range of steady state high gas mass fraction inlet conditions, (gas mass quality 1-0.2) and the disc force characteristics measured for valve choked conditions. The highly compressible two phase flow processes are modelled using an Euler–Euler two fluid CFD approach and the results compared with the experiments. Results indicate that CFD approaches can reasonably capture the key processes but deficiencies exist due to the prediction of two phase built up backpressure in the valve. The methods and data trends are discussed to show the effectiveness of current modelling approaches.
Crack Growth Rate Testing of Bolt-Load Compact Tension Specimens Under Chloride-Induced Stress Corrosion Cracking Conditions in Spent Nuclear Fuel Canisters
Authors: Duncan Andrew J. , Lam Poh-Sang , Sindelar Robert L. , Metzger Kathryn E.
Published: October 2018

Stress corrosion cracking (SCC) may occur when chloride-bearing salts and/or dust deliquesce on the external surface of the spent nuclear fuel (SNF) canister at weld residual stress regions. An SCC growth rate test is developed using instrumented bolt-load compact tension specimens (ASTM E1681) with experimental apparatus that allows an initially dried salt to deliquesce and infuse naturally to the crack front under temperature and humidity parameters relevant to the canister storage environmental conditions. Characterization of initial shakedown tests was performed to determine a more extensive matrix of testing to provide bounding conditions in which cracking will occur. The test specimen and apparatus designs were modified to enhance the interaction between the deliquescing salt and the crack front for more accurate crack growth rate measurement as a function of stress intensity factor, temperature and relative humidity which is an essential input to the determination of in service inspection frequency of SNF canisters. Testing was conducted over a range of relative humidity controlled by the guidance in ASTM E104 from ambient temperature to 50 °C with salt assemblages of ASTM simulated sea salt. After three months exposure in prototypic dried sea salt, the specimens will be examined for evidence of chloride-induced stress corrosion cracking (CISCC) and observations are reported for a range of relative humidity and temperature conditions. The above testing attempts to provide a technical basis for the boiler pressure vessel (BPV) Section XI code case N-860.
Three Approaches to Quantification of NDE Uncertainty and a Detailed Exposition of the Expert Panel Approach Using the Sheffield Elicitation Framework
Authors: Fong Jeffrey T. , Heckert N. Alan , Filliben James J. , Doctor Steven R.
Published: October 2018

The ASME Boiler & Pressure Vessel Code Section XI Committee is currently developing a new Division 2 nuclear code entitled the “Reliability and Integrity Management (RIM) program,” with which one is able to arrive at a risk-informed, NDE-based engineering maintenance decision by estimating and managing all uncertainties for the entire life cycle including design, material selection, degradation processes, operation and non-destructive examination (NDE). This paper focuses on the uncertainty of the NDE methods employed for preservice and inservice inspections due to a large number of factors such as the NDE equipment type and age, the operator’s level and years of experience, the angle of probe, the flaw type, etc. In this paper, we describe three approaches with which uncertainty in NDE-risk-informed decision making can be quantified: (1) A regression model approach in analyzing round-robin experimental data such as the 1981–82 Piping Inspection Round Robin (PIRR), the 1986 Mini-Round Robin (MRR) on intergranular stress corrosion cracking (IGSCC) detection and sizing, and the 1989–90 international Programme for the Inspection of Steel Components III-Austenitic Steel Testing (PISC-AST). (2) A statistical design of experiments approach. (3) An expert knowledge elicitation approach. Based on a 2003 Pacific Northwest National Laboratory (PNNL) report by Heasler and Doctor (NUREG/CR-6795), we observe that the first approach utilized round robin studies that gave NDE uncertainty information on the state of the art of the NDE technology employed from the early 1980s to the early 1990s. This approach is very time-consuming and expensive to implement. The second approach is based on a design-of-experiments (DEX) of eight field inspection exercises for finding the length of a subsurface crack in a pressure vessel head using ultrasonic testing (UT), where five factors (operator’s service experience, UT machine age, cable length, probe angle, and plastic shim thickness), were chosen to quantify the sizing uncertainty of the UT method. The DEX approach is also time-consuming and costly, but has the advantage that it can be tailored to a specific defect-detection and defect-sizing problem. The third approach using an expert panel is the most efficient and least costly approach. Using the crack length results of the second approach, we introduce in this paper how the expert panel approach can be implemented with the application of a software package named the Sheffield Elicitation Framework (SHELF). The crack length estimation with uncertainty results of the three approaches are compared and discussed. Significance and limitations of the three uncertainty quantification approaches to risk assessment of NDE-based engineering decisions are presented and discussed.
Global Harmonization of Fatigue Life Testing in Gaseous Hydrogen
Authors: San Marchi Chris , Yamabe Junichiro , Schwarz Martina , Matsunaga Hisao , Zickler Stefan , Matsuoka Saburo , Kobayashi Hideo
Published: October 2018

Methods to qualify materials for hydrogen service are needed in the global marketplace to enable sustainable, low-carbon energy technologies, such as hydrogen fuel cell electric vehicles. Existing requirements for qualifying materials are not adequate to support growth of hydrogen technology as well as being inconsistent with the growing literature on the effects of hydrogen on fracture and fatigue. This report documents an internationally coordinated effort to develop a test method for qualifying materials for high-pressure hydrogen fuel system onboard fuel cell electric vehicles. In particular, consistency of fatigue life testing strategies is discussed. Fatigue life tests were conducted at three different institutes in high-pressure gaseous hydrogen (90 MPa) at low temperature (233K) to confirm consistency across distinct testing platforms. The testing campaign includes testing of both smooth and notched axial fatigue specimens at various combinations of pressure and temperature. Collectively these testing results provide insight to the sensitivity of fatigue life testing to important testing parameters such as pressure, temperature and the presence of stress concentrations.