bluuebunny/crossref_metadata_2025 huggingface dataset:
Investigation of Acoustic Resonance Phenomenon in a Large-Scale Heat Exchanger
Authors: Huang Guofeng , Wang Heng , Tan Wei
Published: November 2023

In gas-gas heat exchangers, pure tone noise can be generated by gas flow pass tube arrays when the frequency of vortex shedding is close to that of acoustic modes, which is called acoustic resonance. Such resonance phenomenon usually occurred while serving because it is difficult to predict in the design stage. The loud noise is harmful to operational staff and may cause structural damage. The paper reports a case of acoustic resonance in a large-scale heat exchanger containing more than 15,000 staggered tubes with a pitch ratio of 1.33. Unexpected acoustic resonance occurs during service although two longitudinal baffles have been installed aiming to eliminate it. The noise of high-pressure levels appears in the heat exchanger operation process. Acceleration signals are obtained at different positions of the outer wall. Results show that acceleration fluctuations are dominated by narrow band peaks from 100 to 145Hz. By numerically investigating the characteristics of the flow field, vortex shedding frequency is found to be similar to this range, indicating a close relationship between vortex shedding and acoustic resonance. The acoustic modes of the shell side are also calculated by using the effective speed of sound. The results show that the modes excited are more likely to be a combination of longitudinal and transverse modes, rather than a transverse mode which is more commonly encountered. Longitudinal modes used to be ignored and staggered tube bundles are considered not prone to suffer acoustic resonance, which may increase the risk in the design stage. From the case discussed in this paper, it is probably necessary to take both longitudinal and transverse coupled modes into consideration.
Prediction of Depth Defects During Pipeline Magnetic Flux Leakage Detection Based on the AVOA-BPNN
Authors: Xu Lushuai , Dong Shaohua , Peng Donghua , Wei Haotian , Ma Yundong
Published: November 2023

The complex operational conditions of in-service pipelines and the extended service time make them susceptible to metal loss, which can lead to pipeline failure. However, quantifying the defect depth presents a challenge to current research. The depth quantification accuracy of pipeline defects can be improved, and the defect state of long-distance pipelines can be accurately controlled by building a model based on the internal magnetic flux signal. This study performed a pulling experiment for internal magnetic flux leakage detection in pipelines and extracted the triaxial leakage signals of 60 internal and external pipeline defects. Firstly, Pearson correlation coefficient is used to extract the seven main influencing factors affecting the depth of pipeline leakage defects, namely axial signal peak-valley value, axial signal waveform area, axial signal waveform energy, circumferential signal peak-valley value, radial signal peak-valley value, axial integral signal peak-valley value, and radial integral signal peak-valley value. Secondly, the initial weights and thresholds of the backpropagation neural network (BPNN) were optimized using the African Vulture Optimization Algorithm (AVOA). Furthermore, an AVOA-BPNN-based defect depth prediction model for pipe leakage detection was established to address the problem challenge of the BPNN algorithm easily falling into the local optimum. The magnetic triaxial leakage signals of the internal and external pipeline defects collected via 60 sets of drafting experiments were used as examples, while a particle swarm optimized BPNN (PSO-BPNN), genetic algorithm optimized BPNN (GA-BPNN), and an unoptimized BPNN were used as models for comparative analysis. The results showed that optimizing the BPNN using AVOA substantially improved the prediction accuracy of the BPNN model. The AVOA-BPNN model predicted 12 sets of pipe defect depths with an average relative error (MRE) of only 2.67% and a determination coefficient (R2) of 0.99800, which exceeded the values of the BPNN, PSO-BPNN, and GA-BPNN models. The AVOA-BPNN uses the internal leakage detection signal to predict the depth of pipe defects, supporting effective decision-making regarding pipe inspection and maintenance.
Development of a New EPRI Elastic-Plastic Fracture Mechanics Handbook
Authors: Anderson Ted L. , Dodds Robert H. , Thorwald Greg V. , Dessein Thomas , Shim Do Jun
Published: November 2023

Research funded by the Electric Power Research Institute (EPRI) in the 1980s produced a series of Ductile Fracture Handbooks including J-integral solutions for structural components with cracks. The EPRI Handbook series was to serve as an elastic-plastic equivalent to stress-intensity factor handbooks that various authors published in the 1970s. The original EPRI research in this area significantly advanced the field of elastic-plastic fracture mechanics (EPFM), particularly for ductile instability analysis of structures. However, the initial EPRI Handbooks were restricted to simple two-dimensional configurations, so were of limited practical value. Subsequent EPRI Handbooks published in the late 1980s contained numerous errors, and the technical basis of some solutions was not documented.

Advances in computing technology in the past four decades have now made EPRI’s original vision practical. A project is currently underway to produce a new EPRI EPFM Handbook. This project entails over 23,500 3D elastic-plastic finite element analyses of cracked configurations. The process of generating the meshes, editing the input files, running the FEA solver, postprocessing the results files, and fitting results to parametric equations is highly automated. Most computations are performed on an EPRI (Linux) cluster with 36, high-end nodes. New parametric equations for the J-integral, crack opening area (through-wall cracks), crack mouth opening displacement, and load-line displacement (laboratory specimen configurations) are developed in this study.
Damage Modeling in Metal Additive Manufacturing Process Simulations
Authors: Fietek C. , Sakai J. , Love A. , Park Y. H.
Published: November 2023

Additive manufacturing (AM) is a process of making three-dimensional parts from a digital file layer by layer. One of the most popular methods of additive manufacturing is selective laser melting (SLM), which uses a high-power laser to melt and fuse metallic powder particles together. Thermo-mechanical simulations are important for the successful design and implementation of AM processes, as they can predict potential process-induced distortions and residual stresses to the final parts. We find that SLM can lead to the formation of voids, porosity, and other defects in the final part, which can degrade the mechanical properties. One macro-scale approach to modeling these defects is by using a ductile damage criterion like that developed by Johnson and Cook. To predict this damage in Abaqus Standard, a UMAT subroutine was developed implementing the Johnson-Cook plasticity and damage models. To validate this user-subroutine, mechanical examples of increasing complexity were used. In this work, we couple thermo-mechanical finite element simulations with the Johnson-Cook damage model to study the effects of SLM on the propagation of process-induced damage within a part made of Inconel 718. Overall, the process-induced damage could be significant to failure predictions of a deployed part and is an efficient way of predicting material degradation from manufacture.
Flow-Visualization of a Prototypical Helical Coil Test Bundle Undergoing Vibrations
Authors: Sutton Noah , Maher Blake , Vaghetto Rodolfo , Hassan Yassin
Published: November 2023

Flow-Induced Vibrations (FIVs) have been of the upmost interest in the engineering community due to their large role in safety and reliability design in heat exchangers. This has especially been true in the nuclear sector as focuses have shifted to Small Modular Reactors (SMRs). These reactors aim to decrease the volumetric footprint of reactors, while maintaining a reasonable power output. To achieve this more compact heat exchangers and faster flow rates are implemented. These changes lead to larger vibrational amplitudes in the system and must be accounted for. This study utilizes Particle Image Velocimetry (PIV) to provide flow visualization of a prototypical section of a Helical Coil Steam Generator (HCSG) with a clockwise, counterclockwise tube rotation undergoing vibrations. The bundle of interest utilizes a canti-levered attachment approach in order to lower the natural frequency of the system. The flow field statistics are studied intensively in order to gain greater understanding of the FIV phenomenon. Several advanced analysis techniques are utilized in this pursuit such as: Proper Orthogonal Decomposition (POD), Wavelet, and spectral analysis.
A Component-Based Hybrid Reduced Basis Method for Creep Analysis of Complex Structures According to the Omega Model (API 579-1/ASME FFS-1)
Authors: Nguyen Thanh Loi , Chau Nguyen Kha , Cao Nhan Tien , Huynh Di Bao Phuong , Knezevic David J. , Jung Gonghyun
Published: November 2023

Finite element analysis (FEA) for creep life assessment of large-scale structures is challenging due to the highly nonlinear (iterative) nature of creep analysis, the long timescales involved, and the substantial number of FEA degrees of freedom to consider strong interaction between components in full scale system. One of the methods explored to overcome the challenges was the linear-nonlinear hybrid formulation which significantly reduces analysis time with reasonably acceptable accuracy.

The approach used in the analysis takes advantage of the fact that, in practice, we are usually interested in a specific region of a system where creep develops faster than the other regions, and thus we can treat that local region as a locally nonlinear problem that will be analyzed using nonlinear finite element analysis (FEA) while the other regions will be analyzed using Reduced Basis Finite Element Analysis (RB-FEA). The FEA and RB-FEA regions are fully coupled via the Hybrid Solver approach, yielding an accurate solution for the overall nonlinear system. The accuracy of the solution over the entire model is maintained by employing appropriate component training processes to infer the behavior of the field over the entire model, including the linear-nonlinear interface.

The paper presents the creep analysis results for simple Tee joint, multiple Tee joints in a piping, and more complicated piping system consisting of main header, sub-header, and smallbore piping, and demonstrates validity and effectiveness of the proposed method by comparing stress relaxation, cumulative creep strain, solving time and memory consumption to standard FEA.
Generation of a Fatigue Design Curve Suitable for Use on Additive Manufacture Nuclear Plant Components Produced From 316LN Stainless Steel Using Laser Powder Bed Fusion
Authors: Press William , Ferriday Jay , Jones Thomas , Dear Matthew , Poole David
Published: November 2023

The Additive Manufacture (AM) of nuclear plant components using Laser Powder Bed Fusion (LPBF) technology, offers opportunities to reduce costs and improve production lead-times. Cost reductions can be achieved by reducing the amount of raw material required, reducing the amount of machining conducted, and eliminating the welding together of sub-assemblies.

However, AM is a relatively new manufacturing technology, and although now seeing greater usage in industry generally, there are still very few examples of where the technology has been applied to components used in safety critical applications. Furthermore, it is not currently covered by the American Society of Mechanical Engineers (ASME), Section III, nuclear design code. For nuclear plant applications, it is imperative that accurate and robust material property data is established to input into design assessment and analysis.

This paper presents Rolls-Royce’s approach to the derivation of a fatigue design curve specific to AM LPBF 316LN stainless steel with Hot Isostatic Press (HIP) process step, for use in ASME III, Subsection NB-3200 or NB-3600 fatigue crack initiation assessments on nuclear plant applications within its portfolio, including small bore globe valves and pipework tees and reducers.

As part of a safety justification strategy for the implementation of AM LPBF small bore globe valves for nuclear plant Rolls-Royce carried out an initial suite of materials testing, including in-air uni-axial fatigue endurance tests on AM LPBF 316LN stainless steel samples. The limited data generated was seen to fall within the expected scatter when compared to the data upon which the NUREG/CR-6909 air best-fit curve is based. However, on completion of further testing in various test orientations on multiple powder batches and builds a more complex fatigue behaviour was observed.

This paper provides an overview of the investigation into the orientation effects on the material fatigue behaviour, especially at high strain amplitudes, and how a combined best fit curve has been constructed for this material using either a fit to the limiting orientation data or the NUREG/CR-6909 mean curve at each point across the S-N curve, whichever is lower. A fatigue design curve is then produced from the best fit curve by first applying a mean stress correction and then applying transference factors on stress and on cycles to account for material variability, component size and surface finish, and load history.

The fatigue design curve generated specific to AM LPBF 316LN stainless steel is judged to be suitably conservative for the design assessment and analysis of the material on nuclear plant applications, including the AM small bore globe valves which have also undergone supporting ASME, Section III, Appendix II, thermal cyclic testing.
Low-Cycle Fatigue Evaluation of Coke Drum Base Materials and Welded Joints - A Summary of OSU Research Project and Future Work
Authors: Zhang Shutong , Romo Sebastian , Giorjao Rafael A. , Berkson Jacque , Penso Jorge , Guo Haixia , Ramirez Antonio J.
Published: November 2023

Coke drums are critical units in the delayed coking process to produce lightweight oil products from heavy residual oil. The fulfillment of the designed coke drum lifetime is often obstructed by low-cycle fatigue damage over cyclic thermal and mechanical loading. Considering the tremendous cost of drum replacement and production loss due to shutdown, the coke drum lifetime extension is of great economic significance in the oil and gas industry. A research project regarding coke drum fabrication and repair was initiated in the Manufacturing & Materials Joining Innovation Center (MA2JIC) at the Ohio State University in 2016. The project includes two phases of work. The first phase of the study (2016∼2019) focused on the external weld repair of coke drum materials, while the ongoing second phase of the study (2019∼2023) addressed coke drum fabrication and repair. A novel low-cycle fatigue testing approach was developed using Gleeble thermo-mechanical simulator and was applied to evaluating the performance of coke drum base materials and welded joints under cyclic deformation. The project goal is to improve the fundamental understanding of materials and joint performance that allows the optimization of coke drum design, fabrication, and repair. In this technical paper, the key methodologies and achievements of the project will be introduced, and some future work will be proposed for the next step.
High Temperature Hydrogen Attack – A Case History
Authors: Dalal Mitul , Penso Jorge , Hau Jorge
Published: November 2023

High Temperature Hydrogen Attack (HTHA) is defined as an irreversible degradation of the mechanical properties of steel. HTHA can detrimentally affect the service life of carbon steel and low chrome pressure equipment and piping components in the petroleum refining and related industries. HTHA involves high temperature reaction of absorbed hydrogen with carbon in the steel to produce methane. The hydrogen/carbon reaction can cause surface decarburization of the steel. Molecules of Methane are too large to diffuse through the steel and the reaction to methane occurs at grain boundaries and at inclusions or other microstructural imperfection in the steel. As a result, internal methane pressure builds up, initially forming bubbles or cavities, then micro-fissures, and finally fissures that may combine to form cracks. Long-term exposure to high temperature hydrogen environment can lead to volumetric damage which can deteriorate mechanical strength of pressure equipment and piping components and accelerate crack-like flaws. There have been multiple industry failures reported due to HTHA.

This paper summarizes a case history of a HTHA damage in a post weld heat treated (PWHT) carbon steel heat exchanger channel, a reactor effluent exchanger in hydrocracker unit. Summary includes detail data processing of the operating conditions, online monitoring experience and comparison to offline inspection. Thorough metallurgical analysis was performed, and operational data were utilized for predictive model comparison. Failure samples were utilized for an ongoing, multi-year Joint Industry Project (JIP) for fingerprinting.
On the Effect of Rising Liquid on Coke Drum Skirt Fatigue Life
Authors: Fernando John , Kwok Henry , Chan Luke , Iverson Millar , Ju Feng , Yuen Simon
Published: November 2023

Due to the severe thermal gradients that develop on coke drums as they are filled with hot oil during coking and water during quenching, accurate modeling of the heat transfer from the fluid to the vessel is critical in the analysis of coke drums. To this end, transient thermo-mechanical simulations typically utilize point measurements of thermal profiles extracted from coke drums in operation, but oftentimes use these point measurements as uniform thermal inputs across the entire inner surface of the drum. In reality, non-uniform thermal fields develop along the height of the vessel depending on the fluid fill rates, the effects of which have also been considered in a number of studies to date. The current study focuses on comparing these two temperature methodologies by estimating fatigue life at the skirt-to-vessel attachment weld (a prevalent location of fatigue damage) for two common skirt designs, to assess the feasibility of the former, simpler approach. Although the results indicate similarities in the overall trends, differences in fatigue-life estimates of up to 20% are calculated between the two approaches. Given these differences, the methodology presented in this study should be considered when a higher level of accuracy is required in estimating fatigue life. However, the alternative, simpler methodology provides conservative estimates of the fatigue life when directional insight or expediency is paramount.
Ethylene Oxide Reactor Engineered Weld Repair Case History
Authors: Dalal Mitul , Penso Jorge , Hau Jorge , O’Brien Steven , London Tyler , Seow Cui Er , Carollo Vallerio , Chukkan Jazeel , Janin Yin Jin , Rothwell John , Howse David , Consonni Marcello
Published: November 2023

A pair of ethylene oxide reactors have been in service for approximately twenty years. The shell material of construction is SA-543, Grade B, CL.1 They were designed according to ASME Section VIII Div.2. A temporal repair work was engineered to remove cracks and reweld. One-side welding approach was qualified per ASME Section IX. It is widely accepted that tensile residual stresses can be detrimental to the integrity of welded components. A combination of weld residual stress simulation and measurement was performed to predict and characterize the weld residual stresses. Generation and analysis of the models followed established best practice for computational welding mechanics. The weld residual stress profiles were optimized after several interactions and mockup coupons were prepared. The approach included the generation a representative computational welding mechanics model; calibration the free parameters in the model against test data; and then validation of the predictions of residual stresses against various experimental residual stress measurements. The residual stress states in both the original weld mock-up and the as-repaired weld were determined using two different experimental techniques: Air-abrasive Centre Hole Drilling (ACHD) for surface residual stresses and incremental Deep Hole Drilling (iDHD) for through-thickness residual stresses. Mechanical testing included tensile and impact testing along with hardness profiles. Controlled deposition approach was implemented to lower hardness. Extensive temporary repairs were successfully executed. New reactors with lower strength steel and post weld heat treatment are being fabricated for permanent replacement.
Relationship Between Natural Period and Strength of Actual Piping Systems Subjected to Seismic Motion
Authors: Tamura Ichiro , Ishii Yuya , Kamatani Keita , Tamura Shinji
Published: November 2023

The responses of single-degree-of-freedom systems subjected to seismic motion are obtained through the well-known inelastic response spectra or constant-ductility response spectra using the natural periods and yield accelerations. Similarly, the modal responses of multi-degree-of-freedom systems subjected to seismic motion are obtained through the spectra using the natural periods and modal yield accelerations, i.e., the modal yield strengths normalized by the modal masses. The relationship between the natural period and modal yield acceleration of each mode of piping systems was investigated for straight and Z-piping systems in a previous study, and was represented by the proposed piping yield diagrams. In this study, their relationship was investigated for actual piping systems in a nuclear power plant, and was represented by the diagrams. Based on these diagrams, the lower limit line of piping yield diagrams was proposed. Using the lower limit line and inelastic response spectra, the maximum responses of piping systems to various seismic motions can be estimated without performing individual dynamic analyses.
Study on Sealing Reliability of High-Pressure Flange for Bolt Axial Stress Measurement Based on Magnetic Memory Testing
Authors: Wang Yanran , Fan Jianchun
Published: November 2023

The high-pressure flange in the wellhead device frequently uses the octagonal gasket sealing method, which provides the optimal sealing effect by ensuring adequate bolt preload. Thus, the change in bolt preload is the primary factor affecting sealing performance. In order to quantitatively evaluate the reliability of high-pressure flange sealing, the bolt preload measuring experiment based on the metal magnetic memory effect was carried out in this research. The experimental findings demonstrate a linear link between the characteristic parameters of the magnetic signal and the bolt preload. The 6BX-type high-pressure flange model for a wellhead device was employed in order to study the effect of varied bolt loosening and load fluctuation circumstances on sealing performance. In addition, the simulation results demonstrate that the bolt pre-tightening force of the flange and the contact stress on the gasket sealing surface increase logarithmically under internal pressure. Lastly, the leakage rate model for the sealing surface is presented based on the simulation results of the seal clearance height of the rough surface. This research provides a new method for assessing the sealing reliability of high-pressure flanges of type 6BX used in wellhead equipment.
Research on China’s LNG Terminal Standard System and Intelligent Management Mode
Authors: Hu Hangjian , He Yongli , Liu Xin , Duan Zhixiang
Published: November 2023

China’s LNG industry started late, and there are insufficient experience and imperfect systems in the construction, operation, production, and management of LNG receiving stations. Moreover, the construction and application of LNG receiving station standard system lags, and it cannot be effectively improved in view of the changes in China’s national conditions and international energy situation. It is difficult to form an efficient standard system and management system unique to LNG receiving stations; The entire LNG terminal cannot effectively form an effective, scientific, and organic unity.

In view of the above problems, this paper puts forward the requirements for intelligent management of the standard system of LNG receiving stations and the relevant measures and suggestions for intelligent management. Based on many research and collection of relevant industrial standards of LNG receiving stations, combined with the relevant requirements of China’s enterprise standard system construction, the corresponding standard system tables for the design, construction, operation, management, maintenance, and safety of LNG receiving stations are established. Relying on computer and big data technology, combined with intelligent management and other functional requirements, relevant standard system management software and database have been established. The system well realizes the management, update, and review of the standard system, and establishes the PDCA cycle with the quality management system and environmental management system, takes the standardized related activities and resources as a process, manages the whole process of LNG receiving station operation and production, and complements and supports different systems, providing important technical support for the sustainable development of LNG receiving station.
INCEFA-SCALE Project – Data Mining and Lessons Learning
Authors: Cicero Roman , McLennan Alec , Mann Jonathan , Beswick Jack , Doremus Luc , Cuvilliez Sam
Published: November 2023

INCEFA-SCALE is a five-year project supported by the European Commission HORIZON2020 program. It is the successor to the INCEFA-PLUS project that ran from 2015 to 2020. Both projects try to address existing gaps between the fatigue behavior of stainless steels in the laboratory, real fatigue behavior observed in nuclear components during operating service, and provide guidance on how to account for the studied behavior in fatigue assessments.

These programmes are contributing to a database with a large number of parameters (strain amplitude, strain rate, temperature, surface roughness, hold time periods, chemistry, etc.). Once the International Fatigue Database Agreement is signed, this database will be augmented with fatigue data shared by international organisations from the US, Korea, Japan and Europe. This will enable INCEFA-SCALE to investigate one of the largest fatigue databases in the world. However, a database compiled from a range of sources with differing objectives creates an issue for analyists as the data will not necessarily be balanced. The impact that this issue may have on an analysis can be mititgated through good data screening and selection practice that must be informed by data visualization. One of the objectives of the INCEFA-SCALE data mining workpackage is to develop and provide a set of tools to aid in this mitigation as well as enabling the statistical analysis of the broader dataset.

During the INCEFA-SCALE project, a data mining tool was developed to statistically analyze all data available to date. In this paper, these tools are presented and, as a proof of concept, used to analyse the available using similar concepts to that of INCEFA-PLUS. To aid in the evaluation of the database and tools expressions for predicting fatigue life of stainless steel specimens in air and ligh water reactor primary coolant conditions are provided. A key requirement of these data exploration and analysis tools is that they are generally accessible and available to the INCEFA-SCALE community to support collaborative data analysis. The conclusions and findings extracted from this data mining analysis are shown and compared with the current procedures most used in environmental fatigue analyses of nuclear components and systems.
Study on the Calculation Method of Fluid Distributor of Corner-Corner Type in Heat Exchangers
Authors: Zhu Guodong , Song Libin , Zhang Yanfeng , Xie Tian
Published: November 2023

The fluid distributors of corner-corner type (named in ASME, FDCC in abbreviation in this paper) are more and more frequently adopted in large high effective condenser or large efficient heat exchanger because of its advantages of space saving, easy to manufacture and high steam flux. But, high local stresses due to discontinuity at its right angle connection would lead to fracture failure or uneconomical design with current empirical rough design method. Meanwhile, the fluid distributor as the pressure element in shell side of heat exchanger, its axial stiffness would affect the tubesheets, shell and tube bundle of the fixed-tubesheet heat exchanger based on the mechanical model and theory in ASME code. Unfortunately, there is no accurate, scientific solution so far because of its complex structure.

In this paper, the structure character and loads of the fluid distributor were introduced and its risk in design was analyzed. An accurate analytical solution based on elastic shell and plate theory was put forward for the fluid distributor under inner pressure and/or axial forces. The detailed calculation method with linear equation matrix was presented to solve the overall strength, local stresses, and stress trend curves for each component and its overall axial stiffness for the fluid distributor. Finally, the method was verified by numerical simulation. The results indicate that the method developed in this paper is valid and accurate to resolve the current design problems. Meanwhile, it is shown by an example that the method can be programed for effective design for fixed tubesheet heat exchangers.
Results of the Explosive Destruction System P3 Vessel Qualification
Authors: Tribble Megan , Stofleth Jerome , Crocker Robert , Ludwigsen John
Published: November 2023

The V31 containment vessel was procured by the US Army Recovered Chemical Material Directorate (RCMD) as a third-generation EDS containment vessel. It is the fifth EDS vessel to be fabricated under Code Case 2564 of the 2019 ASME Boiler and Pressure Vessel Code, which provides rules for the design of impulsively loaded vessels. The explosive rating for the vessel, based on the code case, is 24 lb (11 kg) TNT-equivalent for up to 1092 detonations. This report documents the results of explosive tests that were performed on the vessel at Sandia National Laboratories in Albuquerque, New Mexico to qualify the vessel for field operations use. There were three design basis configurations for qualification testing. Qualification test (1) consisted of a simulated M55 rocket motor and warhead assembly of 24 lb (11 kg) of Composition C-4 (30 lb [14 kg] TNT equivalent). This test was considered the maximum load case, based on modeling and simulation methods performed by Sandia prior to the vessel design phase. Qualification test (2) consisted of a regular, right circular cylinder, unitary charge, located central to the vessel interior of 19.2 lb (8.72 kg) of Composition C-4 (24 lb [11 kg] TNT equivalent). Qualification test (3) consisted of a 12-pack of regular, right circular cylinders of 2 lb (908 g) each, distributed evenly inside the vessel (totaling 19.2 lb [8.72 kg] of C-4, or 24 lb [11 kg] TNT equivalent). All vessel acceptance criteria were met.
Crack Size Measurements on Fracture Surface Images Using Deep Neural Networks for Semantic Segmentation
Authors: Rosenberger Johannes , Tlatlik Johannes , Münstermann Sebastian
Published: November 2023

For the safe evaluation of nuclear-relevant safety components, a precise and reliable analysis of the fracture surfaces after the test procedure is required. Within the scope of the studies a framework for automated crack size measurements based on image segmentation has been developed, capable of accelerating the standardized but tedious measurement procedure. Different known image segmentation architectures have been trained and assessed based on a specially created fracture surface image dataset. The fracture surfaces originate from SE(B) specimens made of the German reactor pressure vessel steel 22NiMoCr3-7 and its weld material. The evaluation of the model performances via the mIoU metric show that the investigated architectures are very well suited for the pixel-fine classification of fracture mechanisms. Based on the obtained prediction masks, the initial crack size a0 could be measured using the so-called area average (AA) method. The results have been compared to manual 5-point average (5PA) measurements. The automated crack length measurements show statistically verifiable very high precision, comparability, and economic efficiency.
CMOD Compliance Solution Determined by Stress Intensity Factor for Single Edge Notched Tension Specimens in End-Clamped Conditions
Authors: Zhu Xian-Kui
Published: November 2023

The oil and gas industry favors to use single edge notched tension (SENT) specimens in the end-clamped conditions to measure less conservative fracture toughness or resistance curves in low constraint conditions. Usually, single specimen test approach is adopted to measure J-integral or crack tip opening displacement (CTOD) based-resistance curves (simply J-R curves or CTOD-R curves), where the elastic unloading compliance technique is often utilized to monitor crack growth in the quasi-static conditions, and instantaneous crack length is inferred from crack mouth opening displacement (CMOD) compliance measured at each loading step during a single specimen test. Several numerical solutions of CMOD compliance were obtained by finite element analysis for end-clamped SENT specimens. However, these CMOD compliance solutions have varied accuracies and different applicable ranges of crack length ratio a/W. Some of them may be inconsistent with existing solutions of stress intensity factor K for the same clamped SENT specimen because the K factor and the CMOD compliance were determined separately by FEA calculations. Due to this reason, the present paper obtains a more accurate analytical solution of CMOD compliance equation from an accurate full-range K solution for the end-clamped SENT specimens, and thus the proposed analytical solution of CMOD compliance is consistent with the stress intensity factor. Comparisons with different FEA results confirm a higher accuracy of the proposed CMOD compliance solution. Finally, an improved SENT test method is discussed for determining JR and CTOD-R curves.
Material Deterioration and Residual Life Evaluation of High Temperature Steam Pipeline
Authors: Li Zhifeng , Song Libin , Chen Gang
Published: November 2023

Cracks were found in high temperature steam pipes which had been used for 100 000 hours. The mechanical properties of pipe material were tested, and the causes of cracks were analyzed by metallographic and scanning electron microscopy. The fracture parts of the tensile specimens were all in the weld fusion line. The metallographic photos of the weld section showed that there were a large number of precipitates on the fusion line. The energy spectrum analysis showed that the main alloying elements of the precipitates were chromium and molybdenum. The location of a large number of precipitates was consistent with the location of surface cracks. Combined with the working parameters of the pipeline, it was judged that the crack was a creep crack. The existence of precipitates led to micro-local stress concentration and provided conditions for the initiation of cracks, resulting in the weld fusion line becoming the primary part of the creep crack. The stress rupture test showed that the fracture time of the weld sample was shorter under larger load. The residual life of the pipeline was analyzed by using the mechanical properties obtained from the test. The conservative calculation results showed that the residual life of some stress concentration parts was 139.68 hours.
A Phase Field Approach to Fracture Mechanics Problems
Authors: P. C. Sidharth , Rao B. N.
Published: November 2023

Phase field modeling of fracture is a widely used numerical method for predicting fracture-related phenomena in solids. The phase field method is a continuous or diffused approach to fracture that approximates the original crack into a diffused zone of fracture. The diffused region is represented by an auxiliary variable called the phase field, which takes values between one and zero for broken and unbroken phases, respectively. The method is becoming increasingly popular since it conveniently solves the difficulty of explicitly tracing the cracks as displacement jumps and incorporating the same in the finite element mesh. The method gives accurate results for finite element meshes that are sufficiently refined. Exponential finite element shape functions offer a way of enhancing the computational efficiency of simulations. These special shape functions, due to their exponential nature, can capture sharp changes in solution variables with a lesser number of elements employed along the crack propagation path. However, exponential finite element shape functions need to be oriented with respect to the crack propagation path in order to provide a good approximation. This study presents an efficient implementation. An efficient implementation of the phase field fracture model is presented by employing automatically oriented exponential finite element shape functions. The orientation of these shape functions is informed by an approximate analysis using bilinear shape functions. The implementation is validated with previous simulations available in the literature. Computational costs and the accuracy of solutions are investigated for a few common fracture problems.
Technical Basis for Revision to Code Case N-702
Authors: Walter Matthew , Wong Kevin , Cofie Nathaniel G. , Uddin Mo , Dominguez Gary
Published: November 2023

Boiling water reactor (BWR) reactor pressure vessel nozzle-to-shell welds and nozzle blend radii are inspected in accordance with ASME Code, Section XI, which requires 100% inspection during each 10-year in-service inspection interval. ASME Code Case N-702-1 provides inspection relief to 25% of the nozzle population every 10 years. The NRC placed limitations on N-702-1 which excluded feedwater nozzles and control rod drive return nozzles and only allowed implementation for up to 40 years of plant operation. N-702-1 has been used by many utilities for inspection relief, resulting in substantial time, dose and cost savings related to inspections. N-702 was incorporated into ASME Code, Section XI, IWB-2500, Item f in 2018.

Since many plants are operating beyond 40 years, and some plants intend to operate as long as 80 years, there is a need to extend the applicability for up to 80 years of operation. Furthermore, it is desirable to include feedwater nozzles in the technical basis. This paper provides the technical basis to update Code Case N-702 to be applicable for up to 80 years and includes feedwater nozzles. Other updates are also made to the evaluations to bring the analysis in-line with current industry standards.

A summary of the probabilistic fracture mechanics inputs and results are provided in this paper, which demonstrates the probability of failure is within NRC-approved acceptance criteria for each case analyzed. Several sensitivity studies were also performed in order to evaluate the impact of different inputs. Screening criteria is provided for each RPV nozzle including relevant operating parameters. This paper is intended to provide the technical basis for a revision to Code Case N-702-1.
Analysis of Spiral Wound Gasket Behavior Against Tightening With Face Rotation
Authors: Kataoka Shunji , Sato Suguru , Takahashi Kyohei
Published: November 2023

In recent years, leakage reduction and assessment have become necessary from an environmental protection perspective. It is important to properly calculate the gasket contact pressure to estimate and reduce leakage in the design stage.

ASME PCC-1 and API 660 demand higher gasket stress to prevent leakage in service. Increasing the bolt tightening load is expected to improve the gasket sealing performance while flange face rotation increase. Flange face rotation causes the unbalance in gasket contact pressure distribution: while the maximum contact pressure increases, the area of high contact pressure decreases. It is difficult to evaluate the unbalance in gasket contact pressure distribution experimentally. Therefore, a detailed analysis is essential to assess how this affects the sealing performance. SWG is widely used in oil and gas industry. However, the detailed analysis has been difficult due to the spiral structure and the composite property of constituent materials.

In this paper, firstly, the method for detailed analysis of SWG was proposed. The analysis model was developed by combining a hyper-foam material model of CEG filler with a detailed SWG geometry model. Secondly, the analysis model was validated by uniform compression test by parallel plate. The gasket stress curve simulated by the developed model was well matched in the result of uniform compression test. Finally, the effect of flange face rotation to the compression behavior was studied by the developed model. Based on the contact pressure distribution and the filler compression distribution, the relationship between the overall compression behavior and the interaction of constituent materials was discussed.
Study on Regular Inspection Standard of Large Volume Carbon Fiber Fully Wound Cylinder Bundles
Authors: Fang Zhou , Liu Qia , Wang Zhe
Published: November 2023

The large-capacity storage cylinder set in long tube trailers is a key element for transporting high-pressure gas, and its safety in use is of concern. Among them, carbon fiber wound plastic liner is a new generation of gas cylinders with the advantages of lightweight and corrosion prevention. At present, the United States, the United Kingdom and the International Organization for Standardization have established standards on the periodic inspection of carbon fiber fully wound gas cylinders. This paper introduces the scope of application, the content of periodic inspection, and evaluation of the results of these standards based on the comparative study of Chinese TSG 23 Technical Regulations for Gas Cylinder Safety. The group standard T/GDASE 0017-2020 “Periodic Inspection and Evaluation of Carbon Fiber Fully Wound Gas Cylinders with Aluminum Lining for Automotive Compressed Hydrogen Gas” issued by Guangdong Special Equipment Industry Association and the International Organization for Standardization IS011623. And an assessment of the results of these standards and other aspects of the different requirements. On this basis, this paper points out the shortcomings of the testing methods used in the periodic inspection of large volume carbon fiber wound gas cylinders with long tube trailers in China, taking into account the demand for hydrogen storage and transportation in China and the current situation of cylinder production technology in enterprises. Finally, this paper provides some suggestions for the development of a new generation of cylinder periodic inspection and assessment standards and points out several issues that need to be studied in focus for future standard development and implementation for reference.
Study on Analysis Procedure Using Integrated Three-Dimensional FE Model for Reactor Coolant System by Applying to Shaking Table Tests for Scaled Mock-Ups
Authors: Kawashima Takehiro , Kumagai Yasutaka , Asao Yuki , Shimazu Shota , Nishimura Takuya
Published: November 2023

Generally, seismic stress evaluation for a Class 1 component of a nuclear power plant is performed using Finite Element stress analysis with seismic loads that are obtained another calculation. In Japan, a multimass beam model is usually employed to calculate seismic loads for components in a reactor coolant system (RCS) of PWR plant. The components are modeled into simple elements such as mass points and beams in the multimass beam model. So far, three-dimensional FE analysis (3D-FEA) has been applied to stress analysis for each portion in a component. Recent advances in computer performance, however, have made large-scale analysis possible, and 3D-FEA for not only whole of a component but also the integrated all components in a RCS is not difficult at the present time. If the integrated whole 3D-FE model of RCS is employed, stress due to seismic can be directly calculated by applying seismic waves to the 3D-FE model, and the multimass beam model is not necessary. So, we are developing a stress evaluation method that uses an integrated 3D-FE model consisted of all components in RCS, which is called “Seamless Structural Analysis Process”. As a validation for this method, this method has been applied to the shaking table tests for scaled mock-ups previously conducted by the Japanese national projects and the results are discussed in this paper. Three scaled mock-ups, which were modeled for reactor coolant system (RCS), reactor vessel (RV) and reactor vessel internals/control rod drive mechanism (RVI/CRDM), were prepared for these projects. In our study, 3D-FE models have been developed for the RCS, RV and RVI/CRDM mock-ups, and time history response analyses have been performed for those 3D-FE models. The results are discussed in this paper.
Prediction of Dormancy Time of Cryo-Compressed Hydrogen Tank by Considering Dynamic Thermal Boundary
Authors: Yuan Yutong , Ge Zhoutian , Shi Jianfeng
Published: November 2023

Hydrogen has advantages of high efficiency and cleanliness, which has become main target of energy strategy development in many countries. Hydrogen storage is an integral part of the efficient utilization of hydrogen energy, and high pressure and low temperature can effectively improve the storing energy density. This paper studied the hydrogen storage behavior of cryo-compressed hydrogen (CcH2) in an insulated pressure tank. Since the temperature of CcH2 can change from 40.15 K to 233.15 K, it is crucial to consider the temperature change when predicting the dormancy time of CcH2 tank. This paper proposed a theoretical method for predicting the storage behavior of cryo-compressed hydrogen storage tank. The heat influx of radiation, conduction and convention through the thermal boundary of CcH2 tank was calculated based on realtime temperature difference between liner and outer vessel. The theoretical method was verified by experimental results from existing reports, and the predicting results showed good consistency. Furthermore, based on the dynamic heat influx, the influence of filling rate, initial pressure and initial temperature on dormancy time was discussed in detail. Finally, a prediction model was proposed for estimating the dormancy time for cryo-compressed hydrogen.
Numerical Analysis of Gas Explosion Characteristics of Gas Compartment of Utility Tunnel Based on FLACS
Authors: Ma Honglian , Huang Hui , Zhang Guiyuan , Chen Zhiwei , Ji Fang
Published: November 2023

With the rapid development of urbanization and the comprehensive demand for the utilization of urban underground space resources, Utility tunnel, as an emerging infrastructure of the advanced laying method of municipal public pipelines, it’s safe operation is related to the safe operation and functional guarantee of the city, and it is a major “lifeline” project of the city. As one of the most dangerous sources, gas pipeline is prone to secondary and derivative disasters in case of leakage, explosion and other disastrous accidents, which brings great challenges to the safety of urban underground utility tunnel. Based on FLACS simulation, this paper studies the gas explosion characteristics of the gas compartment of utility tunnel. The results show that the explosion overpressure reaches the peak when the methane volume fraction is 9.41%; Compared with the closed pipe gallery model, the preset vent of the comprehensive pipe gallery has a strong pressure relief effect. This research can not only provide basic data for the dynamic response of the explosion impact load to the pipe gallery structure, but also provide theoretical and technical support for improving the disaster prevention and mitigation capability of the gas compartment of utility tunnel, which is of great significance for improving the sustainable and safe development of the city.