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Analysis of Transient Characteristics of Droplets in the Dffb Regime During Single-Rod Channel Reflood Experiment

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SSRN 2023年

作者： Chen, Deqi Chen, Mingjing Liu, Hanzhou Liu, Haidong Zhong, Lei Deng, Jian Key Laboratory of Low-grade Energy Utilization Technologies and Systems Chongqing University Ministry of Education Chongqing400044 China Science and Technology on Reactor System Design Technology Laboratory Nuclear Power Institute of China Chengdu610041 China

This study aims to explore the dynamic distribution and hydrodynamic characteristics of droplets in the process of strong transient reflood. However, the quasi-steady state analysis is generally adopted in the current study, ignoring the dependence of droplet formation and breaking mechanism in the Dispersed flow film boiling (DFFB) mechanism on the time-related historical behaviors such as the advance of the quench front. A series of reflood cooling visualization experiments of zirconium alloy high-temperature rod-shaped heating surface were carried out to achieve this research goal. The wall surface and fluid temperature history curves were recorded, and the parameters, such as the size and velocity of DFFB regime droplets, were quantitatively extracted by visual image processing technology. Based on the formation and breakup mechanism of droplets in the dispersed flow, the reasons for droplet size distribution and velocity change with input heat flux, initial wall temperature, inlet subcooling, and inlet flow rate are well analyzed and explained. At the same time, the experimental results also show a strong correlation between droplet behavior and the reflood process in time. This study can provide more detailed physical support for the subsequent development of droplet behavior models more suitable for the strong transient reflood process and the evaluation of existing models. © 2023, The Authors. All rights reserved.

关键词： Heat flux

Analysis of Transient Characteristics of Droplets in the Dffb Regime During Single-Rod Channel Reflood Experiment

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SSRN 2023年

作者： Chen, Mingjing Chen, Deqi Liu, Haiong Liu, Hanzhou Zhong, Lei Deng, Jian Key Laboratory of Low-grade Energy Utilization Technologies and Systems Chongqing University Ministry of Education Chongqing400044 China Science and Technology on Reactor System Design Technology Laboratory Nuclear Power Institute of China Chengdu610041 China

This study aims to explore the dynamic distribution and hydrodynamic characteristics of droplets during the highly transient process of reflood. However, the quasi-steady state analysis is generally adopted in the current study, ignoring the dependence of droplet formation and breaking mechanism in the Dispersed flow film boiling (DFFB) mechanism on the time-related historical behaviors such as the advance of the quench front. A series of reflood cooling visualization experiments of zirconium alloy high-temperature rod-shaped heating surface were carried out to achieve this research goal. The wall surface and fluid temperature history curves were recorded, and the parameters, such as the size and velocity of DFFB regime droplets, were quantitatively extracted by visual image processing technology. Based on the formation and breakup mechanism of droplets in the dispersed flow, the reasons for droplet size distribution and velocity change with input heat flux, initial wall temperature, inlet subcooling, and inlet flow rate are well analyzed and explained. At the same time, the experimental results also show a strong correlation between droplet behavior and the reflood process in time. This study can provide more detailed physical support for the subsequent development of droplet behavior models more suitable for the strong transient reflood process and the evaluation of existing models. © 2023, The Authors. All rights reserved.

关键词： Heat flux

Insights into Dissolved Oxygen Dependent Crack Initiation Mechanism of 316ln Stainless Steel Fatigue Tested in High-Temperature Pressurized Water

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SSRN 2024年

作者： Qiao, Yufei Li, Hui Tan, Jibo Liu, Daoping Zhang, Ziyu Wu, Xinqiang Ke, Wei CAS Key Laboratory of Nuclear Materials and Safety Assessment Liaoning Key Laboratory for Safety and Assessment Technique of Nuclear Materials Institute of Metal Research Chinese Academy of Sciences Shenyang110016 China School of Materials Science and Engineering University of Science and Technology of China Hefei230026 China Science and Technology on Reactor System Design Technology Laboratory Nuclear Power Institute of China China

The corrosion fatigue behavior of 316LN SS hollow specimen was investigated in high-temperature pressurized water at different dissolved oxygen (DO) concentrations ( © 2024, The Authors. All rights reserved.

关键词： Corrosion fatigue

Representation Learning based and Interpretable reactor system Diagnosis Using Denoising Padded Autoencoder

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arXiv

arXiv 2022年

作者： Li, Chengyuan Qiu, Zhifang Yan, Zhangrui Li, Meifu Science and Technology on Reactor System Design Technology Laboratory Nuclear Power Institute of China Chengdu610213 China CNNC Key Laboratory on Nuclear Reactor Thermal Hydraulics Technology Nuclear Power Institute of China Chengdu610213 China

With the mass construction of Gen III nuclear reactors, it is a popular trend to use deep learning (DL) techniques for fast and effective diagnosis of possible anomalies to ensure the safety of reactor systems under accidents. To improve the robustness of diagnostic model to crippled and noisy monitoring data, and to enhance the interpretability of the diagnostic outputs, this paper focuses on three aspects. First, a novel Denoising Padded Autoencoder (DPAE) model is proposed for representation extraction of monitoring data, and such representation extractor is effective on disturbed data with signal-to-noise ratios up to 25.0 and monitoring data missing up to 40.0%. Secondly, a diagnostic paradigm using DPAE encoder followed by shallow statistical learning algorithms is proposed, and such stepwise diagnostic approach is tested on disturbed datasets with 41.8% and 80.8% higher classification and regression task evaluation metrics, in comparison with the end-to-end diagnostic approaches. Finally, a hierarchical interpretation algorithm using SHAP and feature ablation is presented to analyze the importance of the input monitoring parameters and validate the effectiveness of the high importance parameters. The results of this study inform the development of robust, interpretable, intelligent reactor anomaly diagnosis systems in situations with high safety requirements. Copyright © 2022, The Authors. All rights reserved.

关键词： Monitoring

Enhancing Mechanical Properties and Microstructure Evolution of Hybrid Az61-5sic-0.5cnts Composite During Equal Channel Angular Pressing

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SSRN 2024年

作者： Zhou, Mingyang Zhao, Yanli Sun, Dan Long, Ziyao Gen, Laiyao Fan, Lingling Gao, Shixin Xin, Yong Quan, Gaofeng Gupta, Manoj Science and Technology on Reactor System Design Technology Laboratory Nuclear Power Institute of China Chengdu610213 China School of Mechanical Engineering Chengdu University Chengdu Sichuan610106 China School of Materials Science and Engineering Southwest Jiaotong University Chengdu610031 China 9 Engineering Drive 1 Singapore117576 Singapore

Equal channel angular pressing (ECAP) is one of widely used severe plastic deformation methods for improving performance of metallic materials. In this work, the effects of the ECAP on the microstructural evolution and mechanical properties of the AZ61-5SiC-0.5CNTs composite were studied systematically. The results revealed that ECAP can effectively reduce the porosity of the AZ61-5SiC-0.5CNTs composite, refine grains, weaken basal texture, and promote the further dispersion of CNTs, which can optimize the microstructure of the composite. However, the large shear effect of ECAP also leads to the destruction of the structural integrity of the CNTs and thus reduces the strengthening effect. Due to the combined effects of grain refinement, porosity changes, texture evolution, and structural damage of CNTs, the composites reached the highest strength after 2 ECAP passes at 250 °C. The yield and tensile strengths were increased to 383 MPa (+11.0%) and 445 MPa (+8.0%), respectively, while the elongation was marginally reduced, but remained around 6%. © 2024, The Authors. All rights reserved.

关键词： Equal channel angular pressing

MOLECULAR DYNAMICS STUDY on THERMAL CONDUCTIVITY of UNIRRADIATED and IRRADIATED SYMMETRICAL TILT GRAIN BOUNDARY 3C-SIC 29

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MOLECULAR DYNAMICS STUDY on THERMAL CONDUCTIVITY of UNIRRADI...

2022 29th International Conference on Nuclear Engineering, ICONE 2022

作者： Cai, Ziqi Shao, Zhuang Li, Yuanming Zhang, Qingmin Department of Nuclear Science and Technology School of Energy and Power Engineering Xi'an Jiaotong University Xi'an710049 China Science and Technology on Reactor System Design Technology Laboratory Nuclear Power Institute of China Chengdu610200 China Shaanxi Key Laboratory of Advanced Nuclear Energy and Technology Xi'an Jiaotong University Xi'an710049 China Shaanxi Engineering Research Center of Advanced Nuclear Energy Xi'an Jiaotong University Xi'an710049 China

ISBN: (纸本)9780791886366

The cubic silicon carbide (3C-SiC) has been considered as a candidate structural material for several types of advanced nuclear reactors. The effects of cascade collision on thermal conductivity in symmetrical tilt grain boundary (GB) were studied by Molecular dynamics (MD) simulations. The thermal conductivity of 3C-SiC at 5(210)[001] GB was calculated using non-equilibrium molecular dynamics (NEMD) methods. A relatively small simulation unit was used to analyze the effect of different energies of incident PKA (primary knock-on atoms) on the thermal conductivity of 3C-SiC and to compare the results with perfect structure GB system. Finally, the vibrational density of states (VDOS) of atoms in the GB region was calculated to analyze the phonon mismatch at the interface. Calculations show that cascade collisions generated by energetic atoms will result in a decrease in thermal conductivity of the 5(210) GB system, but the effect varies in different regions, with a sharp decrease in thermal conductivity and an increase in thermal resistance for the intracrystalline region, while the magnitude of change in either thermal resistance or thermal conductivity is not significant in the GB region. Irradiated model shows a higher GB energy compared to the unirradiated model. For all irradiated models, lattice defects have a significant effect on the thermal conductivity of the GB system, depending on the spatial structure of the *** results of the VDOS analysis suggest that an increase in the degree of atomic lattice mismatch near the interface is responsible for a further increase in the thermal resistance of the irradiated GB system. © 2022 American Society of Mechanical Engineers (ASME). All rights reserved.

关键词： Grain boundaries

STUDY ON AUTOMATIC DEPRESSURIZATON system OF SMR

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STUDY ON AUTOMATIC DEPRESSURIZATON SYSTEM OF SMR

2020 International Topical Meeting on Advances in Thermal Hydraulics, ATH 2020

作者： Yin, Shasha Sun, Yan Li, Yi Yang, Hongfa Science and Technology on Reactor System Design Technology Laboratory Nuclear Power Institute of China Sichuan Chengdu China

ISBN: (纸本)9780894487774

Small modular reactor (SMR) is highly cared and researched by people all over the world. There are many differences during reactor operating between the small modular reactor and the traditional large-scale pressurized water reactor, because of the differences in structure and design issues for both reactors. This means that more and better research especially on SMR will be needed. The continued improvements in designing conception of SMR, the research of SMR get to be more in depth and detail. Passive safety system is commonly accepted in the present study, and developed into an indispensable system for the advance nuclear reactor. However, automatic depressurization system (ADS) as an important part of a passive safety system also is a unique system compared with conventional PWR. So ADS system is worthy of comprehensive and in-depth study. In this paper, the severe accident analysis model was established based on the design characteristics of the small modular nuclear. Then, the severe accident process, the thermalhydraulic phenomena and the system safety were researched. Then, based on the results of the severe accident process for SMR, analyze the depressurization capability of ADS system during a station blackout initiated severe accident in SMR, and analysis the effect on accident process. Finally, this paper proposed the optimization and improvement of the automatic depressurization system (ADS). The results of this study are the necessary foundations for the development of small modular reactor severe accident prevention and mitigation measures. © ATH 2020 - International Topical Meeting on Advances in Thermal *** rights reserved.

关键词： Pressurized water reactors

Structure topology optimization design and shock resistance study on nuclear power safety DCS cast aluminum cabinet

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Structure topology optimization design and shock resistance ...

2020 International Conference on Nuclear Engineering, ICONE 2020, collocated with the ASME 2020 Power Conference

作者： Dongwei, Wang Mingxing, Liu Xiao, Wu Hao, Yan Zhiqiang, Wu Science and Technology on Reactor System Design Technology Laboratory Nuclear Power Institute of China Chengdu610213 China

ISBN: (纸本)9780791883761

Offshore floating nuclear power plant (FNPP) is characterized by its small and mobility, which is not only able to provide safe and efficient electric energy to remote islands, but to the oil and gas platforms. The safety digital control system (DCS) cabinet, as a carrier for the electronic devices, plays a significant role in ensuring the normal operation of the nuclear power plant. To satisfy the requirements of cabinet used in the sea environment, such as well rigidity, shock load resistance, good seal and corrosion resistance, etc, more and more attention is focused on the cast aluminum cabinet. However, the cast aluminum structure may cause larger weight of cabinet, which inevitability affects the mobility of cabinet, and increases the carried load of ship as well. Therefore, seeking for an effective approach to design a light weight cast aluminum cabinet for the offshore FNPP is definitely necessary. In this work, a frame of cast aluminum cabinet with lightweight is obtained successfully via structure topology optimization design, it is found that the weight of the frame can be reduced to 50% after optimization iterations. Subsequently, the natural frequency of the optimized cast aluminum cabinet is calculated by using ABAQUS, it is seen that the first mode frequency of the frame is beyond 30 Hz, which can meet the basic stiffness requirement. Accordingly, dynamic design analysis method (DDAM) is performed to verify the ability of the optimized cast aluminum cabinet in resisting sudden shock load, and the shock response characteristics of the cabinet are determined. Numerical results support that the optimized frame of cabinet possesses good resistance to high level shock. However, for the assembled cast aluminum cabinet, the vertical shock circumstance turns out to be the most critical condition, high stress and deformation regions occurs at the bracket and column. Reinforcements are proposed to make the bracket stiffer in this shock loading condition. Copyri

关键词： Finite element method

Study on Uniaxial Tension and Cyclic Deformation Behavior of TA16 at Room Temperature and High Temperature

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Study on Uniaxial Tension and Cyclic Deformation Behavior of...

作者： Shao, Xuejiao Juan, Du kuang, Linyuan Lu, Yuechuan Lu, Jiang Yu, Mingda Science and Technology on Reactor System Design Technology Laboratory Nuclear Power Institute of China Chengdu610213 China

TA16 is a new type of titanium alloy material, which is widely used in pipeline systems of aerospace, ship and nuclear reactor with high temperature and high pressure. In this paper, the basic mechanical properties and cyclic deformation characteristics of TA16 were obtained by uniaxial tensile test and cyclic loading test at room temperature and high temperature. The Chaboche constitutive model can reasonably describe the cyclic plastic cumulative effect of materials and is provided in ANSYS which is a commercial finite element analysis software. The constitutive model of Chaboche presents a very important evolution criterion of follow-up hardening for ratchet simulation. Based on steady cyclic stress-strain curves which is got by strain control at different temperatures, the material parameters of Chaboche model are obtained by least multiplication fitting for TA16 at room and high temperatures. The constitutive model can used in elastic and elastic finite element analysis of TA16 materials. The experiment results show that TA16 exhibits slight cyclic softening under symmetrical strain cycles, and obvious ratcheting behavior under asymmetric stress cycles. When ratcheting strain of the structure reaches a certain saturation state, plastic accumulation will lead to accidental damage of the structure and lead to serious consequences. The stable cyclic stress-strain curves of TA16 at room temperature and high temperature are simulated by Chaboche model. The simulation results are in good agreement with the experimental results, which provides the basic data for the finite element simulation of cyclic deformation behavior of TA16 titanium alloy structure. © Springer Nature Switzerland AG 2020.

关键词： Constitutive models