bluuebunny/crossref_metadata_2025_split huggingface dataset:
Study on PSA Application in VVER NPP Design Extension Condition Identification
Authors: Ma Chao , Ma Yuan , Du Jinyan 
Published: October 2021

Abstract
After the Fukushima accident, the safety requirements of nuclear power plants have been further improved. As an important design requirement, the design extension conditions need to be fully considered in the design of advanced nuclear power plants. Design extension condition list is an important aspect. The VVER nuclear power plant has also made many design improvements on the basis of practice. According to the requirements of design extension condition analysis, combining the design characteristics of VVER nuclear power plants, through carrying out PSA analysis of VVER nuclear power plants, PSA insights are used to systematically analyze the design extension conditions without significant fuel degradation (DEC-A). Such as SBO, ATWS, total loss of feedwater, total loss of heat sink, etc, have been analyzed and quantified to support design extension condition determination. Due to the need to identify important event sequences, the selection of the probability screening value of DEC-A is discussed and suggestions are given. In the probability screening value determination, the safety goal of nuclear power plant is considered, and also the accident sequences in PSA. In addition, the containment bypass event sequence has always been an important radioactive release scenario, which has a greater impact on safety, and is also discussed in the DEC-A analysis.
Validation of Computational Fluid Dynamics Models for Industrial Applications
Authors: Dzodzo Milorad B. 
Published: October 2021

Abstract
Validation of Computational Fluid Dynamics (CFD) models for industrial applications is more challenging due to the complex geometry and long duration and complexity of various postulated accident scenarios, resulting in different and wide ranges of length and time scales. Thus, CFD models for industrial applications are restricted to the smaller subdomains and short periods of postulated accident scenarios.
Validation is most often based on the comparisons with experimental results obtained with the scaled down test facilities. Thus, the effect of scaling needs to be considered and incorporated in the validation process.
During validation, valuable experience is gained related to geometry simplifications, needed mesh size, turbulence and heat transfer modeling, effects of initial and boundary conditions, different fluid thermophysical properties and interaction with other phenomena and processes. Based on the gained experience the validated CFD models are adjusted and used to simulate prototypical domains and conditions.
Several examples of validations of CFD models for industrial applications are presented.
Dedicated CT Tests and Numerical Simulations to Assess Crack Arrest by Quasi-Laminar Flaws
Authors: Dulieu Pierre , Lacroix Valéry , Gérard Robert , Brynk Tomasz , Uytdenhouwen Inge , Chaouadi Rachid 
Published: October 2021

Abstract
Following the detection of a large number of quasi-laminar flaw indications in the core shells of two Belgian Reactor Pressure Vessels (RPV), an extensive Safety Case demonstrating the Fitness-for-Service for continued operation of both reactors was elaborated. These indications were attributed to hydrogen flaking induced during the component manufacturing process. The conservative Flaw Acceptability Assessment demonstrated that the identified indications do not jeopardize the integrity of the reactor vessel in all operating modes, transients and accident conditions. However, beyond this specific case, the need to better understand the behavior of quasi-laminar flaws has been brought to light.
In that framework and as a defense-in-depth investigation, the question of quasi-laminar flaws subsequent behavior in case of fracture initiation is raised. In the hypothetical case of brittle failure initiation, it is expected that the presence of quasi-laminar flaws in the propagation path can stop the flaw propagation. To illustrate this statement, exploratory compact tension (CT) tests are designed such as a mode I pre-crack, from which initiation occurs, subsequently interacts with quasi-laminar flaws in the propagation path. In each of the CT tests, the measured load-displacement curve shows evidence of crack arrest. Besides these experimental results, 3D extended finite element analyses (XFEM) are conducted to confirm and provide additional insights about this phenomenon, in particular the link with the mixed-mode fracture toughness. Moreover, the simulations allow defining an additional test matrix aiming at evaluating the relation between the mixed-mode fracture toughness and the ratio between mode II and mode I stress intensity factors.
The present paper presents the experimental results and describes the numerical simulations that are performed to illustrate the capacity of quasi-laminar flaws to induce a crack arrest phenomenon.
Development of New Design Fatigue Curves in Japan – Treatment of Variable Loading Amplitude Effect
Authors: Asada Seiji , Nomura Yuichiro 
Published: October 2021

Abstract
Design fatigue curves of new concept were developed in the Subcommittee on Design Fatigue Curve in the Atomic Energy Research Committee in the Japan Welding Engineering Society (JWES). Also, Working Group on Design Fatigue Curves (WG DFC) in the JSME is studying the validity and the applicability of the design fatigue curves developed in the JWES to incorporate into the JSME Environmental Fatigue Evaluation Method.
The developed design fatigue curve consists of the best-fit curves using tensile strength as a parameter, correction of mean stress effect employed the Smith-Watson-Topper approach, surface finish effect and variable loading amplitude effect. This paper discusses the treatment of variable loading amplitude effect in the improved design fatigue curves.
The developed design fatigue curves have employed the method of variable loading amplitude effect in EN 13445. This method uses a fatigue life exponent of −0.1 from N = 2 × 106. Research Group on Fatigue Strength in the JSME performed a series of fatigue tests for variable loading amplitude and the test data showed the fatigue life exponent was −0.07. This outcome of the JSME Research Group can support the fatigue life exponent of −0.1 in EN 13445.
A survey of the procedure of variable loading effect has been performed on a thermal fluctuation transient at mixed zone of T-junction piping of nuclear power plants for which UF is significantly affected by variable loading effect. Based on this study, the design fatigue curve for variable loading effect that starts from 2 × 106 with the slope of 1/10, which comes from EN 13445-3, can be considered to be applicable to the developed design fatigue curves. Also, the difference of UF between up to 1 × 108 and extension with no limit is relatively small, and the maximum number of cycles of 1 × 108 can be employed for the engineering fatigue analysis.
Investigation of the Internal Impact During a 9 M Drop Test of an Accident-Safe Waste Package
Authors: Nehrig Marko , Scheidemann Robert , Wille Frank , Ballheimer Viktor 
Published: October 2021

Abstract
The safety assessment of packages for the transport of radioactive material follows the IAEA regulations and guidance. The specified regulatory tests cover severe accidents and demonstrate the package containment system integrity. Special attention must be drawn to the behaviour of the content which could move inside the package due to unpreventable gaps caused by the loading procedure and the structure of the content. A possible internal impact of the content which occurs during the drop tests onto the lid system is investigated. The IAEA regulations SSR-6 and the Guidance SSG-26, revised recently, consider input from Germany and France related to the significance of internal gaps.
In the context of a waste package design assessment, a model was equipped with a representative content to conduct a drop test with an internal impact. The weight and kinetic impact of this content covered all possible real contents. The objective of the test was to maximize the load onto the lid system and to prove the mechanical integrity by complying with the required leak tightness. The test was conducted conservatively at a package temperature lower than −40 °C at the BAM Test Site Technical Safety.
This paper gives an overview of efforts to address internal gaps and their consequences, and the BAM efforts with the implementation of this topic into IAEA regulations and guidance material. The paper then focuses on the conduction of a drop test and investigation of internal component impact.
Numerical Study on the Strain Capacity of Girth-Weld Pipes With Unequal Wall Thickness Transition Joints
Authors: Wang Xu , Shuai Jian , Zhang Shengzhu 
Published: October 2021

Abstract
Girth-weld pipes with unequal wall thickness transition joints result in the misalignment of geometry, and the mismatched welding and heat-affected zone (HAZ) softening prompt inhomogeneity of material in the local area of girth weld. The misalignment of geometry and inhomogeneity of material are the main causes of local strain concentration in the girth weld, which greatly increases the possibility of crack initiation and propagation. In this paper, the numerical models of girth-welded pipe with cracks on the fusion line have been accurately constructed, referring to the crack size and location of the actual accident pipe. The influences such as the ratio of unequal wall thicknesses, the mis-matched coefficients and load conditions on the crack driving force curves have been investigated. The critical apparent fracture toughness has been selected as a failure criterion of girth welded pipe. Results show that an increase in the thickness ratio and a decrease in the weld strength will reduce the strain capacity of girth welded pipes, and the increase in internal pressure will weaken the strain capacity of girth welded pipes. The application of unequal wall thicknesses and low matching welding in the girth-weld pipes in engineering should be avoided or reduced.
Quantitative Risk Assessment of Densely Populated High Consequence Area of Gas Transmission Pipeline
Authors: Zhou Li-Guo , Wang Xiao-Lin , Li Ming , Shi Lei , Wang Yong , Yang Jing 
Published: October 2021

Abstract
In view of the importance of densely populated high consequence area in the management of buried gas pipelines, a special quantitative risk assessment method was proposed in order to clarify the key points of control, optimize resource allocation and refine emergency plans. Firstly, the general failure probability was determined under different pipe diameters based on the pipeline failure statistics. According to the uncertainty of pipeline management and pipeline damage, the calculation models of management correction factor and damage correction factor were constructed. And the pipeline failure probability was obtained by correcting the general failure probability. Then, combining with the theories of explosion shock intensity and fire heat radiation intensity, the probability variable of personnel death was calculated by taking personnel death as the main failure consequence of densely populated high consequence area. Finally, the individual risk and social risk of the gas pipeline accident were analyzed to determine the risk acceptability of the densely populated high consequence area. Method was applicated by taking a buried gas pipeline as an example, the case analysis shows that the risk acceptability can be effectively evaluated through the special quantitative risk assessment, which provides the basis for the formulation of risk control measures, and measures to shorten the response time can reduce the risk level of the pipeline.
Thermodynamic Characteristics of Gas Cylinder During the Process of Hydrogen Filling and Discharging of High Pressure Cycle
Authors: Guo Xiaolu , Fan Zhichao , Liu Xiaoliang , Xu Shuangqing 
Published: October 2021

Abstract
Hydrogen fuel cell vehicle has become the main direction of hydrogen energy utilization because of its advantages of zero emission, short hydrogenation time, long driving range and high efficiency. High pressure hydrogen storage cylinder is one of the key components of hydrogen fuel cell system. Because the temperature of the gas cylinder increases sharply during the rapid hydrogen filling process, and the temperature drops sharply during the hydrogen release process, the drastic temperature change will reduce the fatigue life of the cylinder, which has an important impact on the safety and stability of the whole system. At present, it is necessary to further study the thermodynamic characteristics of gas cylinders in the process of hydrogen filling and discharging. According to the filling and discharging process of high pressure hydrogen cycle, the change and distribution of pressure and temperature and the streamline change in the high pressure cylinder during the process of hydrogen filling and discharging are studied. The pressure and temperature control strategy of high-pressure tank, precooler, test cylinder and low-pressure tank in the process of hydrogen filling and discharging were discussed, and a more safe and effective hydrogen filling and discharging optimization control measure was put forward. This study is of great significance for the stability and safe operation of high pressure hydrogen storage system in the field of hydrogen energy.
Numerical Study on the Re-Rounding Process of Dented Pipelines
Authors: Zhao Pengcheng , Shuai Jian 
Published: October 2021

Abstract
A dent is a common type of pipeline defect that causes a local stress and strain concentrations, which can threaten the safety and integrity of the pipeline. In actual engineering, unconstrained dents tend to re-round as the internal pressure of the pipeline increases. In this paper, the process of re-rounding of a dented pipeline was investigated by numerical study. A 3D numerical model was established. The strain variation of the re-rounding process was analyzed in detail. The effect of various factors (loading depth, indenter diameter, pipe diameter-thickness ratio, initial internal pressure and material) on the re-rounding coefficient were analyzed. The results show that the elastic recovery occurs in the re-rounding process. And no secondary plastic damage occurred in the dented pipeline. The coefficient of re-rounding increases with the increase of the dent depth and initial internal pressure; while the diameter-thickness ratio and indenter diameter display a negative effect. Based on the finite element results, an engineering calculation equation of the re-rounding coefficient was fitted by the nonlinear regression method.
Analytical Limit Load Formula and Procedure for Strength Calculation of Axial Complex Shaped Defect in Pipe
Authors: Orynyak Igor , Bai Julia , Mazuryk Roman 
Published: October 2021

Abstract
This paper describes the analytical model for complex shaped axial defects. The model is based on classical lower bound limit load theorem of theory of plasticity, and consists in construction of statically admissible solution (distribution of stress which satisfies to equilibrium equations). Its main advantage is the possibility to explicitly take into account a lot of geometrical (complex shape) and physical parameters (additional axial loading, variance of material properties along the axis), — while still retaining its relatively simple application and appearance. So, contrary to other approaches, the formula for rectangular defect here is only a particular case of application of the general procedure. The main focus of the paper is description and justification of numeric algorithm of this general procedure (named here as O-procedure) for axial complex defect in pipe under internal pressure, which in fact is an optimization process to get the most favorable stress distribution.
Four different approaches for complex shaped defect are compared. First, ASME (named here as A-) rectangular defect formula combined with RSTRENG (named here as R) procedure, i.e., A-R approach. Second, PCORRC (P-) formula with R-procedure, P-R approach. Third, Orynyak (O-) rectangular formula with R-procedure, O-R approach. Fourth, our universal procedure (as goal of the paper), O-procedure. The comparison is performed as for some artificial complex defects, for example, two interacting rectangular defects, as well as for known full scale test performed in Waterloo University. Further considerations as to enhancing of the theory and its experimental verification are made.
CFD Simulation of Cavitation Erosion Behavior in an Impeller of Industrial Lean Amine Liquid Pump
Authors: Liu Juanbo , Lin Haitao , Duan Linlin , Sun Li , He Meng , Chen Sheng 
Published: October 2021

Abstract
Multistage pump of lean amine liquid is crucial rotating equipment in an industrial refining catalytic reforming unit. Cavitation often causes the damage of impeller in the pump to affect the long-term safe operation of unit. The formation of cavitation on impeller is 3D simulated by using Zwart-Gerber-Belamri model in accord with the actual position under the industrial operating condition. The discrepancies of cavitation range between different volume flux (400 to 800 m3/s. operating pressure (0.4 to 2.0 MPa) and vapor pressure of lean amine liquid (0.05 to 0.5 MPa) in terms of the industrial running conditions every stage impeller are investigated to guide design and safety operation of pump. The simulation results indicate that the impeller cavitation often starts from the forward-curved groove of the blade. and then gradually expands along the flow path of the blade and the two side walls of the forward bend. When the volume flux exceeds critical value of cavitation. the impellers appear cavitation and those ranges enlarge and expend along the flow direction of the blade with the increase of volume flux. With the cavitation pressure increasing. the cavitation ranges of impeller lesson even to disappear. especially at 2.0 MPa. Bigger vapor pressure of lean amine liquid leads easily to erosion.
Numerical Study of Detection of Crack on Corroded Rough Surface Using EMAT-Generated Surface Wave
Authors: Wang Zhe , Chen Xuedong , Fan Zhichao , Chen Wei , Cheng Jingwei , Su Yuanlian 
Published: October 2021

Abstract
Electromagnetic acoustic transducer (EMAT) gradually becomes the main excitation method for surface wave, which is suitably used in periodic inspection or long-term monitoring of pressure equipment. However, the corroded surfaces appearing on the pressure pipes and vessels can cause an increase of background noise and remarkable attenuation of the echo wave, which restrict the improvement of detection accuracy of surface crack. In this paper, a finite element model of EMAT-Generated surface wave inspection for steel plate with rough surface is established based on the constitutive equation of ferromagnetic materials. Considering the Lorentz force and magnetostrictive effect, the influences of rough surface on energy conversion of multiple fields in the excitation and propagation process of electromagnetic acoustic surface wave are separately investigated. The surface wave responses of cracks characterized by rectangular groove on corroded rough surface have been analyzed further. The numerical results indicate that the rough surface of the excitation region below the transducer with a center frequency of 330 kHz has a slight effect on the surface wave energy, while the surface roughness of the propagation region attenuates echo signal of crack significantly. The reflection coefficients of echo signals can be utilized to quantitatively characterize the depth of crack on the corroded surface with roughness less than λ/15 (λ is wavelength of surface wave).
Modeling and Sensitivity Analysis of the TN-32 UNF Cask: Comparison With the HBU Project Data
Authors: Higley Megan , Hadj-Nacer Mustafa , Greiner Miles 
Published: October 2021

Abstract
In this work, a 3D, one-eighth homogenous fuel CFD model of the TN-32 UNF cask is constructed, and simulations are performed as part of the Extended Storage Collaboration Program (ESCP). The simulations are carried out using ANSYS/FLUENT1 package with geometry and boundary conditions recommended by ESCP. Simulation results, including external and internal cask temperatures, are compared with experimental data from the High-Burnup (HBU) project. A preliminary sensitivity analysis is conducted to determine the effect the different assumptions/simplification proposed by ESCP on the cask temperatures. This sensitivity analysis indicates that the cask internal natural convection has a significant effect on the prediction of internal temperatures when the drain holes at the base of the basket are modeled. Additionally, the results indicate that a small variation in the thickness of the peripheral basket-rail gap has a significant effect on the internal temperatures. The best simulation model is shown to include modeling of the drain holes, natural convection, a peripheral basket-rail gap of 4.78 mm (0.188 inch), and omission of the base inner liner-gamma shield gap.
Effect of Shape Modeling on FEM Analysis Results of Equal Tee Pipe
Authors: Nakamura Izumi , Shibutani Tadahiro 
Published: October 2021

Abstract
To understand the properties of the shape of the actual tee pipe and the effect of shape modeling on finite element method (FEM) analysis results, the authors measured the 3D shape of a 150A equal tee pipe and conducted inelastic static and modal analysis on a specimen including the equal tee pipe. The tee pipe joint used in this investigation was a “steel butt-welding type” carbon steel. In the inelastic analysis, the material property was modeled using bi-linear kinematic hardening. The data for two kinds of shapes were prepared for the FEM analysis: based on the measured configuration; based on the nominal dimension.
The 3D shape measurement showed that the actual wall thickness of the tee pipe joint was greater than the nominal value, and it was unevenly distributed in the pipe. The maximum measured wall thickness of the pipe was up to 47% thicker than the nominal value. The analysis showed that the model based on the nominal dimension reduces the collapse load by 25%–30% compared to that based on the actual shape. The distribution of cumulative equivalent plastic strain was also affected by the shape modeling; the model based on the nominal dimension predicts the point of strain concentration to be closer to the center of the tee. Though the natural frequencies of these models were different, which is attributed to the difference of elastic stiffness of each model, the mode shapes were similar.