As a critical component of nuclear and thermal energy conversion systems, the long-term safe operation of a steam generator depends on the structural integrity of its tube bundles. Foreign objects introduced into the secondary side can induce flow-induced vibrations and wear, potentially causing tube wall damage and unplanned outages, thereby affecting overall system reliability. This study systematically investigates the flow-induced vibration behavior of foreign objects within steam generator tube bundles and explores the influence of object geometry through three-dimensional fluid–structure interaction (FSI) simulations. The foreign objects are modeled as single-degree-of-freedom rigid bodies, and their dynamic responses are captured using a coupled flow–motion framework. Results reveal that object geometry significantly influences flow separation, variations in lift and drag forces, and displacement characteristics. Cylindrical and irregular objects exhibit stable, low-amplitude vibrations; plate-shaped objects experience restricted motion due to large drag areas and symmetric contact constraints; whereas helical objects show the largest displacements arising from coupled axial–radial vibrations and complex vortical structures. These findings demonstrate that the interplay between aerodynamic forces and geometric complexity strongly governs the flow-induced vibration of foreign objects, offering insights into their motion behavior and potential impact on steam generator tube bundle integrity.
GUO Yiwen, LI Liangxing, XIANG Zutao, GUI Jiabin, SHI Shang, LEI Zhenxin, XU Xiangyang
The main coolant pump (MCP) of lead-cooled fast reactor (LFR) faces significant corrosion challenges due to the high-temperature, high-density coolant flow and heat transfer within complex geometric domains. Consequently, detailed attention to the internal flow field of the pump is crucial during the design process. Currently, the design of MCP for LFR heavily relies on extensive numerical simulations, requiring the generation of high-quality meshes and the discretization of governing equations for computation. This approach results in high computational costs and prolonged design cycles. To address the issues, a physics-informed neural network (PINN) surrogate model with a multi-input structure was developed and applied it for rapid prediction of the flow field of the MPC in LFR under different operating conditions, to be used in the state tracking module of a digital twin system. The surrogate model was proposed for overcoming the limitations of traditional numerical simulations, such as high computational complexity and large data demands, while enhancing model response speed and reducing storage requirements. First, the flow field within an axial lead-bismuth eutectic (LBE) pump was modeled and the loss function for training the multi-input PINN surrogate model based on the governing equations of the pump was derived. Subsequently, the accuracy of the surrogate model was validated by comparing its reconstruction of the flow field under several specific operating conditions with the results obtained from traditional computational fluid dynamics (CFD) simulations. Additionally, the computational time of both approaches was compared. The results show that the model demonstrates good ability in identifying flow field details near the rotating blades which suffer from the most corrosive environment in the whole pump, with a relative error to CFD calculation results of generally less than 20%, a prediction time of approximately 0.273 seconds per operating condition, and a prediction speed improvement of 15 000 times. The training time is equivalent to that of 2 to 3 CFD simulations for different operating conditions. Furthermore, the model parameters for predicting the flow field across the entire flow passage of the MCP under arbitrary operating conditions require only 286 kB, whereas the flow field data generated by CFD for a single operating condition amount to 413 MB. The conclusion indicates that the surrogate model can effectively fit nonlinear training data, with high prediction accuracy and generalization capability, providing a rapid and efficient flow field prediction tool for the design of the MCP of LFRs, which can be used as the state tracking module in the corresponding digital twin software.
Coherent scattering is the theoretical basis of X-ray diffraction, which is widely used in the field of materials. A functional module to calculate the nondestructive testing of photon-atomic and photon-molecular coherent scattering cross sections is developed in the nuclear data processing code NECP-Atlas. The photon-atomic coherent scattering cross section is processed in NECP-Atlas with the same method as that of NJOY2016. In practice, photon interacts with materials which usually consist of numerous polyatomic molecules. Therefore, the photon-molecular coherent scattering cross sections should be calculated instead of photon-atomic coherent scattering cross sections to acquire more accurate simulated results. First, the independent atom model (IAM) was implemented to calculate the photon-molecular coherent scattering cross sections with the assumption that the atom was isolated. This approximation works well when the momentum transfer of incident photons is large. At small momentum transfer, the interference effects of various atoms cannot be ignored. Then, the molecular interference model was introduced to consider the influence on angular distribution of secondary photons due to the interference effects. The molecular interference functions of water and ethanol were simulated using molecular dynamics simulation, and then applied in the ACE library. The atomic form factors of the atoms in water and ethanol molecules were modified by the molecular interference function. To quantify the influence of molecular interference effects on angular distribution of secondary photons, an imaging system was simulated. Numerical results show that the molecular interference effects have a significantly influence on the angular distribution of photons at small momentum transfer, while at large momentum transfer, the molecular interference effects can be ignored.
Risk management strives to reach the standards of theoretical systematicity and empirical precision achieved in natural science models. To this end, a set of risk-informed and performance-based standards was developed in the form of statistically validated measures. The set enables the systematic extraction by deterministic and probabilistic analysis of potentially objective risk assessments and well-defined decisions. However, much of the data and models are subjectively influenced by the uncertainty of the context in which they are related and derived. Current risk analysis contains a large amount of risk-related information, but without the context of the models, its results lack sufficient predictive and explanatory power to be a solid basis for decisions. Therefore, to model the entire site of a multi-unit nuclear power plant as an integrated system connecting facility and activity, it is necessary to consider not only the technological conditions, but also the entire site context, including human, organizational, and environmental factors. An interface tool for dynamic deterministic-probabilistic safety analysis should be used to contextualize and complement existing risk indicators, but not to replace them. This article presents the possibilities of risk contextualization for nuclear systems through the symptom-based context quantification procedure of the Performance Evaluation Teamwork method.
In Experimental Advanced Superconducting Tokamak (EAST) experiments, to achieve long pulse and high-power ICRH system operation, a new kind of ICRH antenna has been designed. One of the most critical factors in limiting the operation of long pulse and high power is the intense heat load in the front face of the ICRH antenna, especially the Faraday Screen (FS). Therefore, the cooling channels of FS need to be designed. According to thermal-hydraulic analysis, the FS tubes are divided into several groups to achieve more excellent water cooling capability. The number of series and parallel tubes in one group is chosen as six. This antenna went into service in the spring of 2021, and it is delightful that the temperature distribution of the FS tube is below 400 °C in 14.5 s and 1.8 MW ICRH system operation. However, the active water-cooling design was not carried out on the upper and lower plates of FS, which led to severe ablations on that region under long pulse and high power operation, and the temperature is up to 800. Therefore, the upper and lower side plates of the FS were designed with water cooling based on thermal-hydraulic analysis. During the 2022 winter experiments, the temperature of ICRH antenna FS was lower than 400 in the pulse of 200s and the power of 1 MW operation.
The temperature distribution of the reactor pool under natural circulation induced by the RVACS operation was experimentally studied. According to the Bo’ based similarity law, which could reproduce the temperature distribution of the working fluid under natural circulation, SINCRO-2D facility was designed based on the PGSFR. It was reduced to 1 : 25 in length scale, having water as a simulant of the sodium, which is the original working fluid. In general, temperature was stratified, however, effect of the natural circulation flow could be observed by the entrainment of the stratified temperature. Relative cooling contribution of the upper plenum (narrow gap) and lower plenum was approximately 0.2 and 0.8, respectively. In the range of decay heat from 0.2% to 1.0%, only the magnitude of the temperature was changed, while the normalized temperature maintained. Boundary temperature distribution change made a global temperature offset of the pool, without a significant local change. Therefore, the decay heat and cooling boundary condition had no significant effect on temperature distribution characteristics of the pool within the given range of the decay heat and boundary temperature distribution.
AbstractAfter decades of mostly rhetoric on climate change, robust and urgent actions must be taken to avoid its worst effects. However, the energy transition discourse reflects an anti-humanitarian philosophy that will undermine any serious efforts of achieving decarbonisation, as well as merely entrenching already-existing global inequalities. The potential of nuclear power for radically reducing greenhouse gas emissions has been well-explored. However, to date, few attempts have been made to fully discern the broader positive impacts nuclear technology can have on achieving sustainable and equitable development. Nuclear science and technology have broad applications and should be placed at the centre of policies aimed at combatting energy poverty, reducing air pollution, providing clean water, addressing food insecurity, or fulfilling any other of the United Nations’ 17 SDGs. This chapter explores the centrality of energy in ensuring sustainable development, a just energy transition, and the importance of nuclear energy, which goes far beyond simply delivering low-carbon electricity.
A piping system stress analysis need to be re-performed for structural integrity assessment after reinforcement of a pipe with significant wall thinning. For efficient stress analysis, a one-dimensional beam element for the wall-thinned pipe with reinforcement needs to be developed. To develop the beam element, this work presents analytical equations for elastic stiffness of the wall-thinned pipe with reinforcement are analytically derived for axial tension, bending and torsion. Comparison with finite element (FE) analysis results using detailed three-dimensional solid models for wall-thinned pipe with reinforcement shows good agreement. Implementation of the proposed solutions into commercial FE programs is explained.
Hanan Al-Ghamdi, Khaled Farah, Aljawharah Almuqrin
et al.
A reliable and well-characterized dosimetry system which is traceable to the international measurement system, is the key element to quality assurance in radiation processing with cobalt-60 gamma rays, X-rays, and electron beam. This is specifically the case for health-regulated processes, such as the radiation sterilization of single use medical devices and food irradiation for preservation and disinfestation. Polyethylene is considered to possess a lot of interesting dosimetric characteristics. In this work, a detailed study has been performed to determine the dosimetric characteristics of a commercialized high-density polyethylene (HDPE) film using Fourier transformed infrared spectrometry (FTIR). Correlations have been established between the absorbed dose and radiation induced infrared absorption in polyethylene having a maximum at 965 cm−1 (transvinylene band) and 1716 cm −1 (ketone-carbonyl band). We have found that polyethylene dose-response is linear with dose for both bands up to1000 kGy. For transvinylene band, the dose-response is more sensitive if irradiations are made in helium. While, for ketone-carbonyl band, the dose-response is more sensitive when irradiations are carried out in air. The dose-rate effect has been found to be negligible when polyethylene samples are irradiated with electron beam high dose rates. The irradiated polyethylene is relatively stable for several weeks after irradiation.
This study was conducted to discuss the role of urban governments in the future, including intercity network construction, by reviewing cases of responding to COVID-19 in Seoul amid changes in the international situation caused by COVID-19. This paper is organized into four sections. First, this paper described the outbreak of COVID-19 in Seoul from January to August 2020 and the responses of the Seoul Metropolitan Government over time. over time. Second, the background of Alliance for Multilateralism and inter-city cooperation in accordance with the changes in the international situation due to COVID-19 was explained. Third, the response of the Seoul Metropolitan Government to the pandemic was reviewed based on the following four characteristics: (i) Social distancing; (ii) Enhanced contact tracing; (iii) Widespread testing; and, (iv) Early preparation. Finally, this paper reviewed how Seoul city cooperated with overseas cities in order to overcome the pandemic crisis, as well as the cases in which 25 autonomous districts of Seoul shared their policies using the Healthy Cities Network.
Nuclear engineering. Atomic power, International relations
This paper presents experimental and numerical analysis results regarding the effects of an incomplete penetration defect on the fatigue lives of socket welded pipes. For the experiment, four-point bending fatigue tests with various defect geometries (defect depth and circumferential length) were performed, and test results are presented in terms of stress-life data. The results showed that for circumferentially short defects, the fatigue life tends to increase with increasing crack depth, but for longer defects, the trend becomes the opposite. Finite element analysis showed that for short defects, the maximum principal stress decreases with increases in crack depth. For a longer defect, the opposite trend was found. Furthermore, the maximum principal stress tends to increase with an increase in defect length regardless of the defect depth.
A spectroscopic system with multiple viewing chords was developed for QUEST (Q-shu University Experiment with Steady-State Spherical Tokamak) to measure the spatial distribution of ion toroidal velocities in discharges sustained by electron cyclotron resonance heating (ECH). Twenty-four viewing chords were aligned in the midplane and C III emission line spectra were measured for three types of ECH discharge under different magnetic field configurations. By applying an inversion method to the measured spectra, we evaluated the radial distributions of C2+ ion emissivity, temperature, and toroidal velocity. The error in the evaluated velocity was estimated to be less than 5 km/s. It was found that the velocity depends on the magnetic field configuration.
At present, most of the widely used system codes for nuclear safety analysis are one-dimensional, which cannot effectively simulate the flow field of the reactor core or other structures. This is true even for the system codes containing three-dimensional modules with limited three-dimensional simulation function such as RELAP-3D. In contrast, the computational fluid dynamics (CFD) codes excel at providing a detailed three-dimensional flow field of the reactor core or other components; however, the computational domain is relatively small and results in the very high computing resource consuming. Therefore, the development of coupling codes, which can make comprehensive use of the advantages of system and CFD codes, has become a research focus.In this paper, a review focus on the researches of coupled CFD and thermal-hydraulic system codes was carried out, which summarized the method of coupling, the data transfer processing between CFD and system codes, and the verification and validation (V&V) of coupled codes. Furthermore, a series of problems associated with the coupling procedure have been identified, which provide the general direction for the development and V&V efforts of coupled codes.
In this study, the neutronic calculation to obtain tritium breeding ratio (TBR) in a deuterium-tritium (D-T) fusion power reactor using Monte Carlo MCNPX is done. In addition, by using COMSOL software, an efficient cooling system is designed. In the proposed design, it is adequate to enrich up to 40% 6Li. Total tritium breeding ratio of 1.12 is achieved. The temperature of helium as coolant gas never exceed 687°C. As regards the tolerable temperature of beryllium (650°C), the design of blanket module is done in the way that beryllium temperature never exceed 600°C. The main feature of this design indicates the temperature of helium coolant is higher than other proposed models for blanket module, therefore power of electricity generation will increase. Keywords: Fusion, Breeding blanket, Tritium, Tokamak, Helium-cooled pebble bed (HCPB)
Yeon Soo Kim, Joongoo Jeon, Chang Hyun Song
et al.
During severe nuclear power plant (NPP) accidents, a H2/CO mixture can be generated in the reactor pressure vessel by core degradation and in the containment as well by molten corium-concrete interaction. In spite of its importance, a state-of-the-art methodology predicting H2/CO combustion risk relies predominantly on empirical correlations. It is therefore necessary to develop a proper methodology for flammability evaluation of H2/CO mixtures at ex-vessel phases characterized by three factors: CO concentration, high temperature, and diluents. The developed methodology adopted Le Chatelier’s law and a calculated non-adiabatic flame temperature model. The methodology allows the consideration of the individual effect of the heat transfer characteristics of hydrogen and carbon monoxide on low flammability limit prediction. The accuracy of the developed model was verified using experimental data relevant to ex-vessel phase conditions. With the developed model, the prediction accuracy was improved substantially such that the maximum relative prediction error was approximately 25% while the existing methodology showed a 76% error. The developed methodology is expected to be applicable for flammability evaluation in chemical as well as NPP industries.
In order to simulate hydrogen charging and discharging cycles of mechanically loaded structures full 3D Macroscopic Rate Equation (MRE) modelling is proposed based on a finite element method (FEM). The model, implemented in the 3DS Abaqus software, uses a generalized transport equation, which accounts for mechanical fields, hydrogen transport and trapping, and their evolution with time. The influence of a-priori known thermal field has also been included. To ensure the solution convergence and the numerical stability, the trapping kinetic is introduced by using an approximation of the analytical solution the McNabb and Foster equation. Comparisons with a relevant 1D MRE code and with thermal programmed desorption (TPD) experimental results are performed on a 1D configuration to validate the model. Next, the model is used to simulate the tritium diffusion and trapping in a 2D geometry of interest in the upper plug of ITER tokamak, and results of tritium inventory are compared with an equivalent 1D calculation. Keywords: Hydrogen, Kinetic trapping, Modelling, Finite elements, Abaqus, User subroutine, Macroscopic Rate Equations
Aslina Br. Ginting, Supardjo Supardjo, Yanlinastuti Yanlinastuti
et al.
Meningkatnya densitas uranium dari 2,96 gU/cm3 menjadi 5,2 gU/cm3 bahan bakar U3Si2/Al harus diikuti dengan penggunaan kelongsong yang kompatibel. Bahan bakar berdensitas tinggi mempunyai kekerasan yang tinggi, sehingga bila menggunakan paduan AlMg2 sebagai kelongsong dapat menyebabkan terjadi dogbone pada saat perolan. Selain fenomena dogbone, pada saat bahan bakar tersebut digunakan di reaktor dapat terjadi swelling karena meningkatnya hasil fisi maupun burn up. Oleh karena itu, perlu dicari pengganti bahan kelongsong untuk bahan bakar U3Si2/Al densitas tinggi. Pada penelitian ini telah dilakukan karakterisasi paduan AlMgSi sebagai kandidat pengganti kelongsong AlMg2. Karakterisasi yang dilakukan meliputi analisis termal, kekerasan, mikrostruktur dan laju korosi. Analisis termal dilakukan menggunakan DTA (Differential Thermal Analysis) dan DSC (Differential Scanning Calorimetry). Analisis kekerasan menggunakan alat uji kekerasan mikro, mikrostruktur menggunakan SEM (Scanning Electron Microscope) dan analisis laju korosi dilakukan dengan pemanasan pada temperatur 150 oC selama 77 jam di dalam autoclave. Hasil analisis menunjukkan bahwa kelongsong AlMgSi maupun AlMg2 mempunyai kompatibilitas panas dengan bahan bakar U3Si2/Al cukup stabil hingga temperatur 650 oC. Kelongsong AlMgSi mempunyai kekerasan sebesar 115 HVN dan kelongsong AlMg2 sebesar 70,1 HVN. Sementara itu, analisis mikrostruktur menunjukkan bahwa morfologi ikatan antarmuka (interface bonding) kelongsong AlMgSi lebih baik dari kelongsong AlMg2, demikian halnya dengan laju korosi bahwa kelongsong AlMgSi mempunyai laju korosi lebih kecil dibanding kelongsong AlMg2. Hasil karakterisasi termal, kekerasan, mikrostruktur dan laju korosi menunjukkan bahwa PEB U3Si2/Al densitas 5,2 gU/cm3 menggunakan kelongsong AlMgSi lebih baik dibanding PEB U3Si2/Al densitas 5,2 gU/cm3 menggunakan kelongsong AlMg2.
Kata kunci: U3Si2/Al, densitas 5,2 gU/cm3, kelongsong AlMgSi dan AlMg2.
Basma Foad, Salwa H. Abdel-Latif, Toshikazu Takeda
In this work, the reactor kinetics capability is used to compute the design safety parameters in a PWR due to complete loss of coolant flow during protected and unprotected accidents. A thermal-hydraulic code coupled with a point reactor kinetic model are used for these calculations; where kinetics parameters have been developed from the neutronic SRAC code to provide inputs to RELAP5-3D code to calculate parameters related to safety and guarantee that they meet the regulatory requirements. In RELAP5-3D the reactivity feedback is computed by both separable and tabular models. The results show the importance of the reactivity feedback on calculating the power which is the key parameter that controls the clad and fuel temperatures to maintain them below their melting point and therefore prevent core melt. In addition, extending modeling capability from separable to tabular model has nonremarkable influence on calculated safety parameters. Keywords: CLOFA, RELAP5-3D code, Reactor kinetics, PWR
In the present paper, firstly, we review our previous works on uncertainty quantification (UQ) of reactor physics parameters. This consists of (1) development of numerical tools based on the depletion perturbation theory (DPT), (2) linearity of reactor physics parameters to nuclear data, (3) UQ of decay heat and its reduction, and (4) correlation between decay heat and β-delayed neutrons emission. Secondly, we show results of extensive calculations about UQ on decay heat with several different numerical conditions by the DPT-based capability of a reactor physics code system CBZ.
Myagmarjav Odsuren, Kiyoshi Katō, Gonchigdorj Khuukhenkhuu
et al.
We discuss the problems of scattering in this framework, and show that the applied method is very useful in the investigation of the effect of the resonance in the observed scattering cross sections. In this study, not only the scattering cross sections but also the decomposition of the scattering cross sections was computed for the α–α system. To obtain the decomposition of scattering cross sections into resonance and residual continuum terms, the complex scaled orthogonality condition model and the extended completeness relation are used. Applying the present method to the α–α and α–n systems, we obtained good reproduction of the observed phase shifts and cross sections. The decomposition into resonance and continuum terms makes clear that resonance contributions are dominant but continuum terms and their interference are not negligible. To understand the behavior of observed phase shifts and the shape of the cross sections, both resonance and continuum terms are calculated.