bluuebunny/crossref_metadata_2025 huggingface dataset:
Structure Integrity Evaluation of Supercritical Water Cooled Pressure Tube Subjected to Accident Conditions
Authors: Luo Jiacheng , Yu Li , Li Pengzhou , Sun Lei
Published: October 2018

The coolant inside the supercritical water cooled pressure tube operates beyond the critical thermodynamics point of water, and the structure integrity of the pressure tube is of great important to the safety of reactor. Under the accident load, the difference in temperature along the pressure tube wall will cause relatively large thermal stress. Due to the generated high tensile stress, coupled with the internal high pressure load, the defects in the inner surface of the pressure tube may propagate rapidly and even through the wall thickness. This paper investigates the structure integrity of the supercritical water cooled pressure tube based on the deterministic and the probabilistic method of fracture mechanics, and obtains the stress intensity factor and the probabilistic function. It is found that the integrity of the supercritical pressure tube can be maintained from the fracture mechanics analysis under the accident load.
Crack Growth Prediction for Cracked Dissimilar Metal Weld Joint in Pipe Under Large Seismic Cyclic Loading
Authors: Yamaguchi Yoshihito , Katsuyama Jinya , Li Yinsheng
Published: October 2018

Seismic risk assessment of nuclear power plants (NPPs) based on seismic hazard and fragility analyses of structures/components has become important since Japanese NPPs have experienced several large earthquakes beyond the design basis ground motion. In addition, cracks resulting from the long-term operation of NPPs have been detected in piping system of NPPs. For example, in the pressurized water reactor environment, crack initiation and propagation due to primary water stress corrosion cracking (PWSCC) have been observed in dissimilar metal welds made of nickel-based alloy. Therefore, fragility analyses related to seismic probabilistic risk assessment considering such PWSCC and seismic loading are important for more realistic seismic risk assessment. In our previous study, a fragility analysis method for cracked pipes that is applicable for the carbon and stainless steel pipes has been developed. The developed method consists of two functions for evaluating the crack growth due to seismic loading as well as the age-related degradation. Since the crack growth evaluation method is available for only carbon steel and stainless steel pipes, it is important to enhance the applicability of the method to dissimilar metal welds of pipes where the cracks due to PWSCC were observed.

In this study, an extensive study for crack growth evaluation method is performed for the dissimilar metal welds. Here, applicability of the previously developed method to a nickel-based alloy weld is investigated. We performed crack growth tests using the center cracked plate specimens and welded pipe specimens with circumferential through-wall crack machined from dissimilar metal weld joint of pipes. It is found that the amount of crack growth predicted by our crack growth evaluation method are in good agreement with the experimental results. Therefore, we conclude that the previously developed method can be widely used for evaluating the crack growth behavior under seismic loading conditions in the nuclear piping including dissimilar metal welds of pipes.
Monitoring of CMC-Jacketed Pipes for High-Temperature Applications
Authors: Juengert Anne , Friedrich Maximilian , Huang Min , Klenk Andreas , Weihe Stefan
Published: October 2018

The lifetime of pressurized parts under temperature load is limited due to degradation mechanisms such as creep, fatigue and corrosion. The increase of boiler outlet temperatures in conventionally fired power plants and increasing process temperatures in other industries requires the use of creep-resistant steels. Suitable materials are expensive and difficult to manufacture. An alternative approach to increase the lifetime of pressurized components under temperature load is the use of composite pipes. A highly creep resistant jacket made of fiber reinforced ceramic matrix composite (CMC) is applied to new or existing pipes. In laboratory tests the CMC jackets increased the lifetime of hollow cylinder specimens by a factor of about six.

In an already scheduled on-site test a CMC jacketed pipe bend will be installed in the Large Scale Power Plant (GKM) in Mannheim, Germany. To monitor the condition of the steel pipe and the CMC jacket, different techniques are applied. The creep strain is measured at different positions of the steel pipe with high temperature resistant strain gauges. The strain of the compound of pipe and jacket is monitored using resistance wires. Additionally, a monitoring of acoustic emissions (AE) in the CMC jacket will be installed. Failure processes like matrix cracking or fiber breakage excite acoustic signals that can be recorded by high temperature resistant acoustic emission sensors applied to the surface of the CMC. An increase in acoustic activity and intensity is an indicator for ongoing damage processes. Under certain conditions even a localization of the acoustic sources is possible. This paper shows results from a previous project and the preliminary investigations for the scheduled on-site test.
Efficient Solution for Cylindrical Shell Based on Short and Long (Enhanced Vlasov’s) Solutions on Example of Concentrated Radial Force
Authors: Orynyak Igor , Oryniak Andrii
Published: October 2018

There is the general feeling among the scientists that everything what could be performed by theoretical analysis for cylindrical shell was already done in last century, or at least, would require so tremendous efforts, that it will have a little practical significance in our era of domination of powerful and simple to use commercial software. Present authors partly support this point of view.

Nevertheless there is one significant mission of theory which is not exhausted yet, but conversely is increasingly required for engineering community. We mean the educational one, which would provide by rather simple means the general understanding of the patterns of deformational behavior, the load transmission mechanisms, and the dimensionless combinations of physical and geometrical parameters which governs these patterns. From practical consideration it is important for avoiding of unnecessary duplicate calculations, for reasonable restriction of the geometrical computer model for long structures, for choosing the correct boundary conditions, for quick evaluation of the correctness of results obtained.

The main idea of work is expansion of solution in Fourier series in circumferential direction and subsequent consideration of two simplified differential equations of 4th order (biquadratic ones) instead of one equation of 8th order. The first equation is derived in assumption that all variables change more quickly in axial direction than in circumferential one (short solution), and the second solution is based on the opposite assumption (long solution).

One of the most novelties of the work consists in modification of long solution which in fact is well known Vlasov’s semi-membrane theory. Two principal distinctions are suggested: a) hypothesis of inextensibility in circumferential direction is applied only after the elimination of axial force; b) instead of hypothesis zero shear deformation the differential dependence between circumferential displacement and axial one is obtained from equilibrium equation of circumferential forces by neglecting the forth order derivative.

The axial force is transmitted to shell by means of short solution which gives rise (as main variables in it) to a radial displacement, its angle of rotation, bending radial moment and radial force. The shear force is also generated by it. The latter one is equilibrated by long solution, which operates by circumferential displacement, axial one, axial force and shear force.

The comparison of simplified approach consisted from short solution and enhanced Vlasov’s (long) solution with FEA results for a variety of radius to wall thickness ratio from big values and up to 20 shows a good accuracy of this approach.

So, this rather simple approach can be used for solution of different problems for cylindrical shells.
Beyond Shakedown-Ratcheting Boundary
Authors: Adibi-Asl R. , Reinhardt W.
Published: October 2018

The ASME Boiler and Pressure Vessel Code (Section III and Section VIII) provides requirements to avoid a ratcheting (accumulating permanent strain) condition under cyclic thermal load application. The ratchet check in this code is based on the solutions presented by Miller in 1959. One important focus in Miller’s work was to estimate the accumulated plastic strain under cyclic loading. The existing pressure vessels and piping codes have been adopting Miller’s ratchet boundary solution where there is no cyclic plastic accumulation of strain. However, some of these codes also provide limit on accumulated plastic strain under ratcheting conditions. Since the cyclic loading also causes fatigue damage in thee component, the question how to account for the interaction of ratchet deformation, which may contribute to damage in the material, and fatigue damage arises, since the fatigue curves are obtained from tests in the absence of ratcheting. This paper investigates the solutions to calculate growth strain (incremental plastic strain) and their application in design including taking into account the interaction with fatigue. Finite element analysis is presented to validate the analytical solutions.
Fracture Toughness Predictive Models Within the SOTERIA EU Project
Authors: James P. M. , Berveiller M.
Published: October 2018

SOTERIA is focused on the ‘safe long term operation of light water reactors’. This will be achieved through an improved understanding of radiation effects in nuclear structural materials. This project has received funding from the European Union’s Horizon 2020 research and innovation programme under agreement No 661913.

The overall aim of the SOTERIA project is to improve the understanding of the ageing phenomena occurring in ferritic reactor pressure vessel steels and in the austenitic internals in order to provide crucial information to regulators and operators to ensure safe long-term operation (LTO) of existing European nuclear power plants (NPPs). SOTERIA has set up a collaborative research consortium which gathers the main European research centers and industrial partners who will combine advanced modelling tools with the exploitation of experimental data to focus on two major objectives: i) to identify ageing mechanisms when materials face environmental degradation (such as e.g. irradiation and corrosion) and ii) to provide a single platform containing data and tools for reassessment of structural components during NPPs lifetime.

This paper provides an overview of the ongoing activities within the SOTERIA Project that are contained within the analytical work-package (WP5.3). These fracture aspects are focused on the estimates of fracture in both ferritic steels and irradiation assisted stress corrosion cracking (IASCC) in austenitic stainless steels, under irradiated conditions. This analytical development is supported by analytical estimates of irradiation damage and the resulting changes in tensile behaviour of the steels elsewhere in SOTERIA, as well as a wider number of experimental programmes.

Cleavage fracture estimates are being considered by a range of modelling estimates including the Beremin, Microstructurally Informed Brittle Fracture Model (MIBF), JFJ and Bordet Models with efforts being made to understand the influence of heterogeneity on the predicted toughness’s. Efforts are also being considered to better understand ductile void evolution and the effect of plasticity on the cleavage fracture predictions. IASCC is being modelled through the INITEAC code previously developed within the predecessor project Perform 60 which is being updated to incorporate recent developments from within SOTERIA and elsewhere.
UK Programme on Codes, Standard and Procedure Needs for SMR and Gen IV Reactors
Authors: James P. M. , Sharples J. K. , Underwood N.
Published: October 2018

This paper provides an overview of the ongoing activities in the UK to understand the possible needs and development opportunities for design codes, standards and assessment procedures when looking at Small Modular Reactors (SMRs) and Generation (Gen) IV reactors. The project (at the time of the conference) is progressing towards the completion of the initial gaps analysis phase of the work. This project is also part of a wider programme of work being supported by the Innovate UK to consider other pertinent aspects such as materials, automated manufacturing, large-scale manufacture and assembly and modularised build. This paper summarises these activities and the findings to-date.
Engineering J Estimation Equations for Spent Fuel Canisters Under Combined Mechanical and Welding Residual Stresses
Authors: Lee Hyun-Jae , Jeong Jae-Yoon , Kim Yun-Jae , Lam Poh-Sang
Published: October 2018

This paper provides engineering J estimation equations for Spent Fuel Canisters (SFCs) under combined mechanical and welding residual stress (WRS) fields. The basic form of estimation equations is reference stress-based ones as in R6. Interaction between mechanical (primary) and residual (secondary) stresses is treated using the V-factor. Based on systematic finite element (FE) analysis and J results, the V-factors for the combined mechanical and welding residual stresses are reported.
Study on Fatigue Characteristics of CFRP
Authors: Takehana Tatsumi , Yamada Toshihiro , Sano Takeru , Kimura Katsuyuki , Miyashita Tetsuji , Shiga Yuta , Yoshikawa Nobuhiro , Kobayashi Hiroshi
Published: October 2018

With the widespread use of fuel cell vehicles in recent years, the development of hydrogen containers for vehicles and accumulators for hydrogen refueling stations has been actively carried out. For these containers and accumulators, in addition to being lightweight and combination of materials that don’t deteriorate with high-pressure hydrogen gas, composite containers using carbon fiber reinforced plastic (CFRP) have attracted attention.
Study on Stress Rupture Characteristics of CFRP
Authors: Sano Takeru , Yamada Toshihiro , Takehana Tatsumi , Miyashita Tetsuji , Shiga Yuta , Yoshikawa Nobuhiro , Kobayashi Hiroshi
Published: October 2018

With the widespread use of fuel cell vehicles in recent years, the development of hydrogen containers for vehicles and accumulators for hydrogen refueling stations has been actively carried out. For these containers and accumulators, composite containers using carbon fiber reinforced plastic (CFRP) have become a focus.
Acceptance Criteria for Probabilistic Fracture Protection Evaluations of CANDU Zr-Nb Pressure Tubes
Authors: Scarth Douglas , Gutkin Leonid
Published: October 2018

Requirements for pressure-temperature limits to protect against rupture of CANDU nuclear reactor Zr-Nb pressure tubes are provided in the Canadian Standards Association (CSA) Standard N285.8. The requirements are based on a stability evaluation of a postulated axial through-wall flaw for all ASME Service Level A, B, C and D loadings. The flaw stability evaluation is strongly dependent on the fracture toughness of the Zr-Nb pressure tube material. The fracture toughness of Zr-Nb pressure tubes is decreasing with operating hours. The decrease in fracture toughness as well as compounding conservatisms based on using bounding values make deterministic evaluations more challenging. The CSA Standard N285.8 permits probabilistic evaluations of fracture protection, but does not provide acceptance criteria. Proposed acceptance criteria that meet the intent of the design basis for Zr-Nb pressure tubes have been developed. The proposed acceptance criteria consist of a proposed maximum allowable conditional probability of pressure tube rupture for the entire reactor core, as well as a proposed maximum allowable conditional probability of rupture of a single pressure tube. The paper provides a description of the technical basis for the proposed acceptance criteria for probabilistic evaluations of fracture protection.
Effect of Simulated Heat Affected Zone Thermal Cycle on the Creep Deformation and Damage Response of Grade 91 Steel Including Heat-to-Heat Variation
Authors: Takahashi Yukio , Shigeyama Haruhisa , Siefert John , Parker Jonathan
Published: October 2018

Grade 91 and other creep strength enhanced ferritic steels are widely used in fossil power plants as the structural materials of high temperature piping and components. As the operating temperature of these plants is as high as 600°C, creep deformation and accompanying damage cannot be neglected in evaluating their integrity. In particular, creep damage tends to concentrate in the softened heat-affected zone in welded joints and often caused so-called type-IV cracking, in advance of failure in base metal or weld metal. In evaluating the likelihood of such a failure, it is important to understand the mechanical property of such region in comparison with base metal and weld metal. Previous studies have shown that considerable degradation of creep strength brought by thermal cycles simulating the temperature history experienced by such a zone. In order to strengthen the understanding, thermal cycle was given to six Grade 91 heats encompassing a wide range of creep properties and their creep behavior was evaluated in this study. As a result, it was found that resistance for creep deformation and rupture life of six heats showed different trend than what was observed in the original metal but the heat-dependency of the ductility seems to be inherited.
Proposed Review Framework for Design of Pressure Retaining Systems and Components (PRSC) in Small Modular Reactor (SMR)
Authors: Eom Seyun , Sadek Nabel , Chaudhry Khalid , Cole Chris , Awad Raoul , Duan Xinjian
Published: October 2018

A recent surge of nuclear industry interest in the development of smaller, modular/factory-built nuclear reactors has been underway for the last few years. Recently, the Canadian Nuclear Safety Commission (CNSC), which is the Canadian nuclear regulatory authority, has been reviewing a number of proposed Small Modular Reactor (SMR) designs through the pre-licensing Vendor Design Review (VDR) process. Some of these SMR designs propose to operate under relatively high neutron fluxes and at elevated temperatures to achieve high thermal efficiency compared to current operating power reactors. Other designs employ a highly corrosive coolant medium. Such operating conditions could accelerate or present unforeseen degradation mechanisms that could adversely affect the integrity and service life of the pressure boundary. It is therefore crucial to understand the material behavior under these conditions to devise appropriate design rules for metallic and non-metallic components. Thus, a systematic approach and a well-designed research and development program to address any knowledge gaps in material behavior at the early design stage for a SMR is crucial, so that potential/plausible degradation mechanisms are accounted for and the structural integrity of Pressure Retaining Systems and Components (PRSC) is maintained over the design life. This paper discusses a proposed framework based on key review findings from the pre-licensing VDR of several SMR designs in Canada.
Cycle-Wise Process-Zone Model for Prediction of Delayed Hydride Cracking Initiation Under Flaw-Tip Hydride Ratcheting Conditions
Authors: Xu Steven X. , Cui Jun , Scarth Douglas A. , Cho David
Published: October 2018

Flaws found during in-service inspection of Zr-2.5Nb pressure tubes in CANDU(1) reactors include fuel bundle scratches, debris fretting flaws, fuel bundle bearing pad fretting flaws and crevice corrosion flaws. These flaws are volumetric and blunt in nature. A key structural integrity concern with in-service blunt flaws is their susceptibility to delayed hydride cracking (DHC) initiation, particularly for debris fretting flaws under flaw-tip hydride ratcheting conditions. Hydride ratcheting conditions refer to situations when flaw-tip hydrides do not completely dissolve at normal operating temperature, and accumulation of flaw-tip hydrides occurs with each reactor heat-up/cool-down cycle. A significant number of in-service flaws are expected to be under hydride ratcheting conditions at late life of pressure tubes.

DHC initiation evaluation procedures based on process-zone methodology for flaws under hydride ratcheting conditions are provided in CSA (Canadian Standards Association) N285.8-15. The process-zone model in CSA N285.8-15 predicts whether DHC initiation occurs or not for given flaw geometry and operating conditions, regardless of the number of reactor heat-up and cool-down cycles. There has been recent new development. Specifically, a cycle-wise process-zone model has been developed as an extension to the process-zone model in CSA N285.8-15. The cycle-wise process-zone model is able to predict whether DHC initiation occurs or not during a specific reactor heat-up and cool-down cycle under applied load. The development of the cycle-wise process-zone model was driven by the need to include flaw-tip stress relaxation due to creep in evaluation of DHC initiation. The technical basis for the development of the cycle-wise process-zone model for prediction of DHC initiation under flaw-tip hydride ratcheting conditions is described in this paper.
Comparison of Predicted Cyclic Creep Damage From a Multi-Material Weldment FEA Model and the Traditional R5 Volume 2/3 Weldment Approach
Authors: ElAgha Feras , Tanner David , Knowles David
Published: October 2018

The R5 assessment procedure for Integrity of High Temperature Structures employs a Weld Strain Enhancement Factor (WSEF) (dependent only upon classified weld type) for predicting creep-fatigue crack initiation at weldments (V2/3 Appendix 4). This serves to amplify the calculated total strain at the weld toe for full penetration welds to account for geometric concentration and material mismatch between weldment zones. The value of WSEF recommended for fillet welds was derived from a review of a limited number of tests on thin welds which were not wholly representative of a typical fillet weld.

The objective of this paper is to present a comparison of the predicted cyclic creep defect initiation damage at a fillet weld toe using a multi-material finite element (FE) model of the weldment, against the damage predicted using the traditional R5 V2/3 approach, which uses only the parent material properties to derive the weld toe strain range in combination with the WSEF. In this example, the fillet weld joins a high temperature tube to an anti-vibration strap. There is pressure loading in the tube and displacement loading due to thermal expansion.

The FE model incorporates material properties associated with both the parent and the weld metal, including elastic modulus, plastic yield properties, creep deformation, and creep ductility (to determine damage via ductility exhaustion). The finite element analysis is run for 30 cycles (pressure and thermal cycling) with an average dwell period of 736 hours, with predicted damages for 100 cycles estimated using extrapolation. Sensitivities considering the stress-strain properties of the weld are included.

The cycle to cycle evolution of damage after 100 cycles including the weld-parent interaction in the FE modelled weldment is shown to be significantly lower than that predicted by the traditional R5 V2/3 route.
Reactor Vessel Nozzle Inner Radius Fracture Analyses Using Elastic-Plastic Fracture Mechanics
Authors: Marlette S. E.
Published: October 2018

The American Society of Mechanical Engineers (ASME) published Section XI Code Case N-648-1 [1] in order to provide alternative examinations of reactor vessel nozzle inner radii. The Code Case was created because ultrasonic examination of the inner radius regions of reactor vessels nozzles is not practical within the operating fleet and the likelihood of flaws developing within these locations is extremely low. Justification for using alternative visual examinations was provided in a paper published at the 2001 Pressure Vessel and Piping (PVP) Technology Conference [2]. This 2001 PVP paper used linear elastic fracture mechanics (LEFM) to demonstrate tolerance for flaws significantly larger than would be detected using nondestructive examination techniques.

However, the Code Case [1] and PVP paper [2] were only applicable to operating plants in the United States. Thus, there was a need to provide a similar fracture analysis considering the AP1000® design to support elimination of volumetric examinations of the nozzle inner radius regions. It was also important to consider improvements in facture mechanics techniques that have been recently published in the ASME Code. The ductile behavior of the material at operating temperatures allow for the use of elastic plastic fracture mechanics (EPFM) methods which provides significantly improved flaw tolerance results. This paper compares results from analyses using LEFM and the EPFM methods for the AP1000 reactor vessel nozzle inner radii region and demonstrates tolerance for large flaws within these regions in order to support a basis for elimination of volumetric inspection during in-service and pre-service examination for the AP1000 design.
Discussion of the Background of the Design Margins in API 17TR8 HPHT Design Referencing ASME VIII Division 3
Authors: Peters Daniel T. , Pham Man
Published: October 2018

There has been a significant amount of discussion of the appropriateness of the design margins from ASME Boiler and Pressure Vessel Code Section VIII Division 3 being applied to the design of HPHT equipment. A technical report has been issued with a first revision which references the use of ASME Section VIII Division 2 and Section VIII Division 3 for design of HPHT equipment above 15 ksi. Additionally, there has been recent pressure testing which attempted to validate the margins used in ASME Section VIII Division 3 and API 17TR8. There has also been a significant amount of discussion that the equipment in HPHT service may be very different from the pressure equipment which utilizes ASME Section VIII Division 3 and the design methods discussed in the standards. This paper will discuss the background of ASME Section VIII Division 3, including an overview of how the standard began, and the types of equipment which were being considered when the document was first drafted. It will also discuss the background of the design margin used in ASME Section VIII Division 3 over the years and how the current margin came into play. It will also discuss the margins used in addition to the margins on the structural capacity of a piece of equipment and how the margins interrelate within the Code. This paper will demonstrate the robust nature of ASME Section VIII Division 3, and its applicability to the design of HPHT equipment.
A Quasi-Steady In-Plane Fluidelastic Instability Analysis of a Rotated Triangular Tube Array in Two-Phase Cross Flow
Authors: Olala Stephen , Mureithi Njuki
Published: October 2018

In-plane fluidelastic instability is a dynamic phenomenon requiring fluid coupling of at least two degrees-of-freedom, in this case, at least two flexible tubes. Due to the nature of the mechanism causing streamwise fluidelastic instability, a purely experimental or an unsteady determination would require intensive experimental effort. As a compromise between experimental effort and prediction accuracy, the quasi-steady model is used in the current study. In the present work, previously measured quasi-steady and unsteady forces are used to estimate the time delay first between the displacement of an oscillating tube and the forces generated on itself then the time delay between the displacement of a central oscillating tube and the forces induced on the adjacent tubes. The estimated time delays are then used together with drag coefficients and derivatives to predict the in-plane fluidelastic instability in a rotated triangular tube array of P/D = 1.5 subjected to two-phase flow. The results closely replicate dynamic test results and confirm the predominance of the stiffness controlled mechanism and the potential of the quasi-steady model in accurately predicting streamwise fluidelastic instability in arrays subjected to two-phase flows.
Analytical Determination of Stress Indices and Stress Intensification Factor for an Extruded Nozzle of Super Pipe
Authors: Feng Lv , Gengyu Zhou , Haiyang Qian
Published: October 2018

The super pipe nozzles in nuclear power plants are usually designed to be in compliance with the requirements of Class 2 piping of Section III of the ASME Boiler and Pressure Vessel Code. The stress indices B2 and stress intensification factor i are required for the stress evaluation. In the past two decades, the hot extrusion forming technology has been widely used to manufacture those nozzles, instead of traditional insert weldolets. However, previous extruded nozzle stress analyses have shown B2 that the calculated stresses may exceed the limits in some working conditions. The objective of present study is to determine the stress indices and stress intensification factor for an extruded nozzle of the supper pipe by the finite element method and to evaluate the conservatism of those factors from the ASME Code formulae. In this paper, a three-dimensional finite element model of an extruded nozzle is developed. Four load cases are considered, which are corresponding to an in-plane bending moment and an out-plane bending moment applied at the run pipe side and at the branch pipe side, respectively. The magnitude of bending moment is assumed to be 1000Nm. The stress indices B2r, B2b, C2r, C2b, K2r and K2b, where the subscript r and b refer to the run pipe and B2r the branch pipe, are calculated based on the finite element analysis results. The stress intensification factor ir and ib are determined by the empirical formula: ir = C2r*K2r/2 and ib = C2b*K2b/2. Further, the developed factors are compared with those calculated from the ASME code formulae. It is found that the stress indices B2r and B2b obtained from the linear elastic finite element analysis are conservative. Currently, the values of B2r and B2b gained from the ASME code formulae are more appropriate for the stress evolution. The stress intensification factors ir and ib obtained from the analytical determination are lower than those calculated from the ASME code formula. For the extrude nozzle studied, the factor ir decreases 30% and the factor ib decreases about 3.3%.
Margins Assessment of Pressure-Temperature Limit Curves for a RPV
Authors: Feng Lv , Gengyu Zhou , Haiyang Qian
Published: October 2018

In order to prevent brittle fracture, the pressure and temperature in a reactor pressure vessel (RPV) is controlled by pressure-temperature (P-T) limit curves during the heat-up and cool-down processes. Nuclear power plants should update the P-T limit curves periodically, because of RPV material irradiation embrittlement. Too restricted P-T limit curves may cause difficulty of operating a reactor. The 2007 edition of the RCCM code Annex ZG provides a new method for defining the P-T limit curves. In this paper, two types of the P-T limit curves for a French type RPV are established by different methods, which are the current operation limits based on the 1993 edition of the RCCM code and the new proposed limits according to the 2007 edition of the code. The margins of the current P-T limit curves are evaluated by comparing with the new proposed limit curves. Furthermore, the reasonability of improvements of the new P-T limit curve method is discussed, and their individual effects are investigated, including the conventional defect size, the required material toughness and the stress intensity factor plastic correction. The present results indicate that the current P-T limit curves for the RPV studied are conservative and have about 25∼70 °C margin in the transition temperature range and about 10∼12MPa in the upper shell temperature range, depending on different conditions. The new P-T limit curve method, which not only removes some conservative assumptions in the previous method but also restricts some requirements, is more reasonable and can provide a relaxed operation window. Present results can be a reference for the nuclear power plant owner to release the operation limits and is helpful in enhancing our understanding of the P-T limit curve.
Comparison of New Proposal for Simplified Elastic-Plastic Analysis and Code Case N-779
Authors: Reinhardt Wolf , Ranganath Sampath
Published: October 2018

In the fatigue analysis in Section III design by analysis, the evaluation is performed in terms of alternating stress, but the evaluation curves are alternating strain – life curves that were converted to alternating pseudo-stress by formally multiplying elastic-plastic (total) strains by a modulus of elasticity that is representative of the elastic regime. The corresponding evaluation method would be an elastic-plastic analysis where the calculated strain amplitude is multiplied by the modulus of elasticity that is provided with the Code fatigue curve to obtain the alternating pseudo-stress. When the alternating stress is calculated by elastic analysis but is found to be in excess of the elastic regime, corrections need to be applied that account for the difference between stress from an elastic analysis and the pseudo-stress that would be obtained from an elastic-plastic analysis.

Performing such a correction is the objective of simplified elastic-plastic fatigue analysis. An alternative to the simplified elastic-plastic fatigue analysis in Appendix XIII, XIII-3450, is given by Code Case N-779. A new proposal has been developed recently, with the objective to be less conservative in most cases than the very conservative method in Appendix XIII, XIII-3450, and more straightforward to apply than Code Case N-779. The new proposal has been validated with elastic-plastic analysis results. The present paper details a comparison to Code Case N-779 over a large range of parameters. The causes for discrepancies and implications are discussed in detail.
Inter-Laboratory Proficiency Testing of NDT Labs According to ISO 17043 As a Tool for Continuous Improvement Principle According to ISO 9001
Authors: Zavadil Tomáš
Published: October 2018

Inter-laboratory proficiency testing of NDT laboratories acc. to ISO 17043 is an effective tool to select laboratories competent to perform the NDT tasks according to the customer requirements in desired quality especially. The goal of this article is to show that inter-laboratory proficiency testing is also a relevant tool for assessing the continuous improvement principle acc. to ISO 9001. It is demonstrated how proficiency testing may help the NDT labs to fully understand the NDT process, get feedback and self-reflection on performing NDT tasks, monitor the internal efficiency and improve the laboratory through a continuous evolution of NDT process.
Effect of Helix Angle on the Bending Capacity of a 5 Inch API-Style Threaded Flange
Authors: Han Young-Hoon , Shirley Blake , Pivowar Jason
Published: October 2018

This paper investigates the effect of helix angle on the structural bending capacity of an API 5-1/8 inch 15,000 psi rated threaded flange under internal pressure and external tension and bending. The three-dimensional finite element flange connection is analyzed with and without the helix angle, and API 17TR8 criteria is selected as a standard to calculate capacity. It was found that the helix angle model predicts a more conservative bending capacity with low internal pressure when compared to the model without a helix angle. At higher bore pressures, the roles reverse and the bending capacity predicted by the helix angle model is less conservative than the non-helix angle model. This disparity is diminished as external tension is increased.
Room temperature long-range coherent exciton polariton condensate flow in lead halide perovskites
Authors: Su Rui , Wang Jun , Zhao Jiaxin , Xing Jun , Zhao Weijie , Diederichs Carole , Liew Timothy C. H. , Xiong Qihua
Published: October 2018

Long-range coherent polariton condensate flow is observed in all-inorganic perovskite microcavities.
Efficacy of Azithromycin and Miltefosine in Experimental Systemic Pythiosis in Immunosuppressed Mice
Authors: Loreto Erico S. , Tondolo Juliana S. M. , de Jesus Francielli P. K. , Verdi Camila M. , Weiblen Carla , de Azevedo Maria I. , Kommers Glaucia D. , Santurio Janio M. , Zanette Régis A. , Alves Sydney H.
Published: October 2018

We evaluated the efficacy of azithromycin (50 mg/kg, every 12 h [q12h] orally) and miltefosine (25 mg/kg, q24h orally) treatments in an experimental model of vascular/disseminated pythiosis in immunosuppressed mice. Azithromycin was the only treatment able to reduce mortality.
Phosphodiesterase Genes Regulate Amylovoran Production, Biofilm Formation, and Virulence in Erwinia amylovora
Authors: Kharadi Roshni R. , Castiblanco Luisa F. , Waters Christopher M. , Sundin George W.
Published: October 2018

Precise control of the expression of virulence genes is essential for successful infection of apple hosts by the fire blight pathogen,
Erwinia amylovora
. The presence and buildup of a signaling molecule called cyclic di-GMP enables the expression and function of some virulence determinants in
E. amylovora
, such as amylovoran production and biofilm formation. However, other determinants, such as those for motility and the type III secretion system, are expressed and functional when cyclic di-GMP is absent. Here, we report studies of enzymes called phosphodiesterases, which function in the degradation of cyclic di-GMP. We show the importance of these enzymes in virulence gene regulation and the ability of
E. amylovora
to cause plant disease.
Proximal humerus deformity, in a four-limb amputee following meningococcal septicaemia
Authors: Ikram Adeel , Singhania Kriti , Tafazal Suhayl , Tambe Amol
Published: October 2018

We present a challenging case of proximal humerus varus deformity in a four-limb amputee, caused by growth arrest from meningococcal septicaemia. The deformity resulted in a loss of function for our patient with inhibition of activities of daily living, requiring corrective osteotomy to help improve the range of motion of the shoulder. We describe in detail the management of our patient, highlight the importance of the orthopaedic manifestations of meningococcal septicaemia, and demonstrate the importance of monitoring potential deformities from growth arrest in these patients.
Umbilical cord anomalies: antenatal ultrasound findings and postnatal correlation
Authors: Kong Catrin Kar Yee , Zi Xean Khoo , Li Fay Xiangzhen , Chandran Suresh
Published: October 2018

Umbilical cord anomalies are rare. The differential diagnosis for a cystic structure around the umbilical cord and its insertion include pseudocyst, omphalomesenteric duct cyst, haemangioma, omphalocele or anterior abdominal wall defects. Although cord anomalies can be detected through antenatal ultrasound scans (US), very often a definitive diagnosis cannot be made. This may affect the management of the infant at birth. In cases where antenatal US was not diagnostic, current evidence supports the use of MRI to help in making an accurate diagnosis. We report two cases of umbilical cord anomalies. The first case was diagnosed in antenatal US as an omphalocele, but was found to be an allantoic cyst with hamartoma on postnatal diagnosis. The second case was not detected on antenatal US, and was diagnosed postnatally as a small omphalocele with vitellointestinal duct remnants.
Acceptability and feasibility of dual HIV and syphilis point-of-care testing for early detection of infection among pregnant women in China: a prospective study
Authors: Wang Qian , Chan Po-Lin , Newman Lori M , Dou Li-Xia , Wang Xiao-Yan , Qiao Ya-Ping , Su Min , Chen Xiang-Sheng , Jin Xi , Wang Ai-Ling
Published: October 2018

Objective

To assess the feasibility and acceptability of using WHO prequalified combined dual HIV/syphilis rapid diagnostic tests (RDT) for same-day results in antenatal care (ANC) clinics.

Methods

This is a pragmatic implementation study using quantitative approach to evaluate outcomes. Antenatal clinic attendees from 21 rural and urban township hospitals in two provinces of China were offered with free dual RDTs testing that included HIV and syphilis, in addition to the routine blood tests. Study outcomes included testing uptake before and during dual RDT use, test feasibility and acceptability among pregnant women. Regression model was used to assess acceptance of RDT testing.

Results

In total, 1787 out of 1828 pregnant women attending ANC received the RDT testing. Testing uptake among pregnant women in their first and second trimester increased from 76.0% (2438/3269) using standard blood testing to 90.1% (1626/1787) with concurrent RDT use (χ2=197.1, p<0.001). Among 1787 pregnant women who received RDT tests, 98.3% (1757/1787) participants were given test result the same day. Positive proportions of HIV and syphilis screened with RDT were 0.06% (1/1787) and 1.0% (18/1787), respectively. Regression analysis indicated that women who did not receive syphilis or HIV testing before were less likely to accept dual RDT (OR 0.28, 95% CI 0.10 to 0.75). Acceptance for dual RDT testing at second or third antenatal visit was lower compared with the first visit (OR 0.37, 95% CI 0.15 to 0.94).

Conclusion

Combined dual HIV/syphilis RDT with same-day results increased uptake of HIV and syphilis testing among pregnant women at primary healthcare facilities. Given the diversity of testing capacities among health services especially in rural areas in China, the dual RDT kit is feasible tool to improve testing uptake among pregnant women.
Comparison of branded rugby headguards on their effectiveness in reducing impact on the head
Authors: Frizzell Erin R A , Arnold Graham P , Wang Weijie , Abboud Rami J , Drew Tim S
Published: October 2018

Aim

To compare the available brands of rugby headguards and evaluate their impact attenuation properties at various locations on the cranium, with regard to concussion prevention.

Methods

Seven different branded headguards were fitted onto a rigid headform and drop-tested in three different positions. An accelerometer measured the linear acceleration the headform experienced on impact with the ground. Each test involved dropping the headform from a height that generated 103.8 g on average when bare, which is the closest acceleration to the upper limit of the concussion threshold of 100 g. A mean peak acceleration for each drop position was calculated and compared with the bare baseline measurement.

Results

Each headguard demonstrated a significant decrease in the mean peak acceleration from the baseline value (all p≤0.01). Overall the Canterbury Ventilator was the most effective headguard, decreasing the impact force on average by 47%. The least effective was the XBlades Elite headguard, averaging a force reduction of 27%. In five of the seven headguards, the right side of the headwear was the most effective at reducing impact force.

Conclusion

Overall, the results indicate that it would be beneficial to wear a headguard during rugby in order to reduce the impact forces involved in head collisions. There was also a clear difference in performance between the tested brands, establishing the Canterbury headguard as the most effective. However, only one model of headguard from each brand was tested, so further research evaluating all other models should be considered.
Effectiveness of the 2014 European Society of Cardiology guideline on sudden cardiac death in hypertrophic cardiomyopathy: a systematic review and meta-analysis
Authors: O’Mahony Constantinos , Akhtar Mohammed Majid , Anastasiou Zacharias , Guttmann Oliver P , Vriesendorp Pieter A , Michels Michelle , Magrì Damiano , Autore Camillo , Fernández Adrián , Ochoa Juan Pablo , Leong Kevin M W , Varnava Amanda M , Monserrat Lorenzo , Anastasakis Aristides , Garcia-Pavia Pablo , Rapezzi Claudio , Biagini Elena , Gimeno Juan Ramon , Limongelli Giuseppe , Omar Rumana Z , Elliott Perry M
Published: October 2018

Objective

In 2014, the European Society of Cardiology (ESC) recommended the use of a novel risk prediction model (HCM Risk-SCD) to guide use of implantable cardioverter defibrillators (ICD) for the primary prevention of sudden cardiac death (SCD) in patients with hypertrophic cardiomyopathy (HCM). We sought to determine the performance of HCM Risk-SCD by conducting a systematic review and meta-analysis of articles reporting on the prevalence of SCD within 5 years of evaluation in low, intermediate and high-risk patients as defined by the 2014 guidelines (predicted risk <4%, 4%–<6% and ≥6%, respectively).

Methods

The protocol was registered with PROSPERO (registration number: CRD42017064203). MEDLINE and manual searches for papers published from October 2014 to December 2017 were performed. Longitudinal, observational cohorts of unselected adult patients, without history of cardiac arrest were considered. The original HCM Risk-SCD development study was included a priori. Data were pooled using a random effects model.

Results

Six (0.9%) out of 653 independent publications identified by the initial search were included. The calculated 5-year risk of SCD was reported in 7291 individuals (70% low, 15% intermediate; 15% high risk) with 184 (2.5%) SCD endpoints within 5 years of baseline evaluation. Most SCD endpoints (68%) occurred in patients with an estimated 5-year risk of ≥4% who formed 30% of the total study cohort. Using the random effects method, the pooled prevalence of SCD endpoints was 1.01% (95% CI 0.52 to 1.61) in low-risk patients, 2.43% (95% CI 1.23 to 3.92) in intermediate and 8.4% (95% CI 6.68 to 10.25) in high-risk patients.

Conclusions

This meta-analysis demonstrates that HCM Risk-SCD provides accurate risk estimations that can be used to guide ICD therapy in accordance with the 2014 ESC guidelines.

Registration number

PROSPERO CRD42017064203;Pre-results.
Low-density lipoprotein level on admission is not associated with postintravenous thrombolysis intracranial hemorrhage in patients with acute ischemic stroke
Authors: Hong Chien Tai , Chiu Wei Ting , Chi Nai Fang , Lai Le Yan , Hu Chaur Jong , Hu Han Hwa , Chan Lung
Published: October 2018

Intravenous thrombolysis with the tissue plasminogen activator (tPA) is the gold standard for acute ischemic stroke. However, its application is limited because of the concern of the post-tPA intracranial hemorrhage (ICH). Low low-density lipoprotein (LDL) has been speculated to increase the risk of hemorrhagic transformation after ischemic stroke. However, whether LDL is associated with post-tPA ICH remains controversial. The present study obtained the medical records from Shuang Ho Hospital and retrospectively reviewed for the period between August 2009 and December 2016 to investigate the association between LDL and the risk of post-tPA ICH. The differences were analyzed using the Student's t-test, Fisher's exact test, the univariate and stepwise multiple regression model, and p<0.05 was considered statistically significant. Among 218 patients, post-tPA ICH was noted in 23 (10.5%) patients. Patients with post-tPA ICH tended to have a lower LDL level (ICH group: 102.00±24.56, non-ICH group: 117.02±37.60 mg/dL, p=0.063). However, after adjustment for the factors might affect the risk of post-tPA ICH, such as stroke severity, onset-to-treatment time interval, and atrial fibrillation (AF), LDL level was not associated with post-tPA ICH whereas AF was the only significant factor increased the risk of post-tPA ICH (adjusted OR: 1.177, 95% CI 1.080 to 1.283). In addition, patients with AF had significant lower LDL level and for patients without AF, LDL was not associated with the post-tPA ICH. In conclusion, LDL level is not associated with the risk of post-tPA ICH in Taiwanese patients with stroke.