bluuebunny/crossref_metadata_2025_split huggingface dataset:
Evaluation of Bending Limit of 9Cr-1Mo-V Steel by Master Curve and Failure Assessment Diagram Method: Evaluation of Base Metal
Authors: Oda Kazuo , Nakatani Mitsuyoshi , Tanaka Tomohiro , Abe Masamitsu , Takashima Yasuhito , Minami Fumiyoshi 
Published: October 2018

We investigated the bending and rolling limit of 9Cr-1Mo-V steel plate used in pressure vessels for the purpose of improving its manufacturing efficiency. Hereafter in this report, the bending limit refers to bending by press or by roller. It includes acceptable crack size, temperature, introduced plastic strain and other factors.
When fracture toughness tests of 9Cr-1Mo-V steel plate were performed at bending temperature in production, unstable fracture rarely occurred. Since fracture probability during the bending process seems to be low, it was not possible to evaluate aspects of the degree of safety factor for brittle fracture. To estimate the bending limit at high temperature where unstable fracture rarely occurs, a method was proposed for estimating fracture probability using master curve and failure assessment diagram (FAD).
In order to verify the proposed method, loading tests simulating the bending process were performed. The bending limits obtained from the loading tests were in good agreement with the values predicted by the proposed method.
In this study, guidelines such as required toughness value and bending temperature for preventing brittle fracture during the bending process of 9Cr-1Mo-V steel plate were investigated.
Pilot Study for Uncertainty Analysis in Probabilistic Fitness-for-Service Evaluations of Zr-2.5Nb Pressure Tubes: Identification of Influential Variables
Authors: Manu Christopher , Datla Suresh , Gutkin Leonid 
Published: October 2018

Canadian Nuclear Standard CSA N285.8, “Technical requirements for in-service evaluation of zirconium alloy pressure tubes in CANDU® reactors”(1), permits the use of probabilistic methods when performing assessments of the reactor core. A non-mandatory annex has been proposed for inclusion in the CSA Standard N285.8, to provide guidelines for performing uncertainty analysis in probabilistic fitness-for-service evaluations within the scope of this Standard, such as the probabilistic evaluation of leak-before-break. The proposed annex outlines the general approach to uncertainty analysis as being comprised of the following major activities: identification of influential variables, characterization of uncertainties in influential variables, and subsequent propagation of these uncertainties through the evaluation framework or code.
The application of the proposed guidelines for uncertainty analysis was exercised by performing a pilot study for one of the evaluations within the scope of the CSA Standard N285.8, the probabilistic evaluation of leak-before-break based on a postulated through-wall crack. The pilot study was performed for a representative CANDU reactor unit using the recently developed computer code P-LBB that complies with requirements of Canadian Nuclear Standard N286.7 for quality assurance of analytical, scientific, and design computer programs for nuclear power plants. This paper discusses the approach used and the results obtained in the first stage of this pilot study, the identification of influential variables.
The proposed annex considers three approaches for identifying influential variables, which may be used separately or in combination: analysis of probabilistic evaluation outputs, sensitivity analysis and expert judgment. In this pilot study, local sensitivity analysis was used to identify and rank the influential variables. For each input variable in the probabilistic evaluation of leak-before-break, the local sensitivity coefficient was determined as the relative change in the output variable associated with a relative change of a small magnitude in the input variable. Each input variable was also varied across a large range to assess the linearity of the relationship between the input variable and the output variable. All relevant input variables were ranked according to the absolute value of their sensitivity coefficients to identify the influential variables. On the basis of the results obtained, the pressure tube wall thickness was found to be the most influential variable in the probabilistic evaluation of leak-before-break based on a postulated through-wall crack, followed by the fracture toughness of Zr-2.5Nb pressure tube material and the pressure tube inner diameter. The results obtained at this stage were then used at the second stage of this pilot study, the uncertainty characterization of influential variables, as discussed in the companion paper PVP2018-85011.
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.
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.
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.
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.
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

ObjectiveTo 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.MethodsThis 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.ResultsIn 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).ConclusionCombined 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.