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SSRN 2023年

作者： Sun, Qishi Han, Ruiyu Guo, Kailun Wang, Chenglong Zhang, Jing He, Xiaoqiang Qiu, Suizheng Su, Guanghui Tian, Wenxi Department of Nuclear Science and Technology State Key Lab. of Multiphase Flow in Power Engineering Shaanxi Key Lab. of Advanced Nuclear Energy and Technology Xi’an Jiaotong University Xi’an710049 China Key Lab. of Nuclear Reactor System Design Technology China Nuclear Power Research and Design Institute Chengdu610213 China

To investigate the best performance wick forms to support the design and fabrication of high-performance heat pipes, in this paper, two kinds of nanostructured wick were prepared by the oxidation-reduction method. The effect of surface nanostructure on the wick performance was investigated by comparing the surface characteristics, capillary properties, permeability, and evaporation properties. The result shows that the nanostructured wick presented excellent super hydrophilic properties. A liquid-lift visualization experimental method for measuring the capillary performance factor M was proposed, and it was verified to be correct by the separation effect of the capillary pumping experiment under a vacuum environment. With the increasing oxidized degree, the densification of nanoparticles on the wick surface increased the capillary performance factor M from 8.68 μm to 13.81 μm, with a maximum enhancement of 59.1%. The effective capillary radius decreased from 4.70×10-5 m to 4.01×10-5 m, with a maximum reduction of 14.9%. The permeability increased from 4.33×10-10 m2 to 5.83×10-10 m2, with a maximum enhancement of 34.7%. The increase in porosity made the effective capillary radius dominate the competition for permeability, and the capillary performance factor decreased by 17.1%. The thermal resistance of the wick decreased with the enhancement of the capillary performance factor, which fell from 2.03×10-3 m2·K/W to 1.26×10-3 m2·K/W. The current study provides a reference for the future design and preparation of high-performance heat pipe wicks. © 2023, The Authors. All rights reserved.

关键词： Heat resistance

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Thermally-Induced Fracture in the Oxide Scale of T91 Ferritic/Martensitic Steel after Exposure to Oxygen-Saturated Liquid Lead-Bismuth Eutectic

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SSRN 2024年

作者： Liu, Yunpeng Du, Juan Zhou, Zhikun Tian, Chenwen Liu, Zhenyu Zhang, Ying Shi, Kaikai Chen, Ziguang Department of Engineering Mechanics School of Aerospace Engineering Huazhong University of Science and Technology Wuhan430074 China Science and Technology on Reactor System Design Technology Laboratory Nuclear Power Institute of China Chengdu610213 China Hubei Key Laboratory of Engineering Structural Analysis and Safety Assessment 1037 Luoyu Road Wuhan430074 China

Ensuring the continuity and stability of the oxide scale to separate T91 steel from lead-bismuth eutectic (LBE) is an effective method for limiting corrosion in the lead-based fast reactor system. In this study, we specifically investigate the impact of cooling thermal stress on the stability and damage of the oxide scales of T91 steel when exposed to oxygen-saturated liquid lead-bismuth eutectic at high temperatures. We revisit a corrosion test conducted on T91 steels exposed to stagnant oxygen-saturated LBE at 500 °C. Experimental results indicate that oxide damage exists without any external force, including interface cracks and through-scale cracks perpendicular to the interface. We develope a three-layer peridynamic model of T91-(Fe,Cr)3O4-Fe3O4 to simulate the deformation and failure of oxides under a cooling process from high temperature to room temperature. The simulation results show that a temperature drop of about 200 °C from 500 °C can cause through-oxide cracks in the oxide scale, and subsequent cooling can lead to the propagation of interfacial cracks. Additional modifications are introduced in the model to account for the porosity of the oxide scale. Parametric investigations illustrate the effects of oxide scale thickness and porosity on the resulting crack patterns. © 2024, The Authors. All rights reserved.

关键词： Oxygen

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Capillary Limit of a Sodium Screen-Wick Heat Pipe

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SSRN 2022年

作者： Ma, Yugao Wang, Xueqing Yu, Hongxing Huang, Shanfang Zhang, Yingnan Huang, Jian Su, Guanghui Deng, Jian Chai, Xiaoming Hu, Wenzhen School of Nuclear Science and Technology Xi’an Jiaotong University Shanxi Xi’an710049 China Science and Technology on Reactor System Design Technology Laboratory Nuclear Power Institute of China Chengdu610213 China Department of Engineering Physics Tsinghua University Beijing100084 China State Key Laboratory of Multiphase Flow in Power Engineering China

High-temperature alkali-metal heat pipes are passive heat transfer devices, where the capillary pressure created by the menisci in the wick pumps the condensed fluid back to the evaporator. Thus, the heat pipe heat transfer capacity is limited by the maximum capillary pressure at high heat fluxes. This work presents a two-dimensional heat and mass transfer model that includes the capillary and gravitational forces that are used to predict the capillary limit which is then validated by experimental data. The predicted critical heat flux temperature has an error of less than 20℃ and a relative error of 6%. The predicted transient sequences are consistent with the measurements. The model shows that capillary limit is affected by inclination angle, heat flux, and wick structure. For inclinations, the critical heat flux at the capillary limit is linearly related to the inclination angle with the predicted temperature rising 2 ~10℃/s during the early stage of the capillary limit critical heat flux condition. The evaporator temperature oscillates before the capillary limit with positive inclinations. For heat fluxes, increasing the heat flux by 17% increases the temperature increase rate 10 fold with a longer dryout length. The evaporator exhibits hysteresis after the capillary limit due to partial dryout of evaporator. For wick structures, reducing the mesh screen pitch from 80 μm to 15 μm reduces the critical heat flux to 10% of the CHF at 80 μm. This model can accurately predict the heat pipe temperature variations at the capillary limit and can explain the physical mechanisms for the dryout oscillations and recovery hysteresis at the capillary limit. Thus, the measurements and model provide analytical guidelines for designing heat pipe cooling systems. © 2022, The Authors. All rights reserved.

关键词： Heat flux

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Numerical Study on the Impact Characteristics of a Single Molten Lead Bismuth Droplet on Water

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SSRN 2024年

作者： Lin, Yue Zhang, Dalin Chen, Yutong Zhang, Xisi Deng, Jian Du, Peng Tian, Wenxi Qiu, Suizheng Su, Guanghui Department of Nuclear Science and Technology State Key Lab. of Multiphase Flow in Power Engineering Shaanxi Key Lab. of Advanced Nuclear Energy and Technology Xi’an Jiaotong University No.28 Xianningxilu Beilinqu Shaanxi Xi’an710049 China Institute of Reactor Engineering Technology China Institute of Atomic Energy Beijing102413 China Science and Technology on Reactor System Design Technology Laboratory Nuclear Power Institute of China Sichuan Chengdu610213 China

As an important link in the possible occurrence of steam explosions, the interaction between molten materials and coolant is of great significance for safety analysis in severe accidents of nuclear reactors. This study is based on the two-dimensional multiphase and multi-component fluid dynamics code ACENA to model the process of single molten lead bismuth droplet impacting a water tank and obtain the velocity changes of the molten droplet as it moves through the water tank. Furthermore, a sensitivity analysis of relevant factors such as the heat transfer area fraction and drag coefficient of the droplet is carried out. To verify models in ACENA, the computation results are compared to experimental data. It is demonstrated that the overall trend of the velocity curve acquired by the ACENA code during the interaction between a molten lead bismuth droplet and water is consistent with the experimental results. The droplet falling velocity increases with the increase in droplet temperature when the temperature of water is the same, and the droplet falling velocity increases with the increase of water temperature at the same droplet temperature. The simulation results by ACENA code for MFCI are in good agreement with experiments which verifies the accuracy of relevant models in ACENA. It can provide an effective means for safety analysis of nuclear reactors in China. © 2024, The Authors. All rights reserved.

关键词： Drops

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Addition of Niobium in Fe-13cr-4.5al-2mo Alloy Used as Atf Cladding: Effect on High Temperature Water Corrosion and In-Situ Electrochemistry

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SSRN 2022年

作者： Liao, Jingjing Wang, Hui Wu, Jun Zhang, Wei Xu, Fei Sun, Hongying An, Xuguang Qiu, Shaoyu Chengdu University China Science and Technology on Reactor Fuel and Materials Laboratory Nuclear Power Institute of China Sichuan Chengdu610213 China Science and Technology on Reactor System Design Technology Laboratory Nuclear Power Institute of China Sichuan Chengdu610213 China School of Mechanical Engineering Anyang Institute of Technology Henan Anyang455002 China Interdisciplinary Materials Research Center Institute for Advanced Study Chengdu University Sichuan Chengdu610106 China

Niobium addition in candidate accident tolerant fuel (ATF) cladding FeCrAl alloy has received much attention, but its effect on high temperature water corrosion behavior has not been revealed. Four alloys with different Nb content (0wt%, 0.5wt%, 1.0wt% and 1.5wt%) based on Fe-13Cr-4.5Al-2Mo model alloy were designed, and the corrosion behavior was investigated by in-situ electrochemistry and microscopy. The in-situ electrochemistry analyses were carried out in 360 。C/19.0MPa lithiated and borated water connected with a loop system to monitor the water chemistry. Detailed studies on the oxide film formed after exposure for 85 days were conducted by focused ion bombarding and transmission electron microscopy. FeCrAl alloys have satisfactory corrosion resistance because of small corrosion currents and thin oxide films. Only monolayer multicrystal spinel oxide forms on alloy surface. Slight Nb addition (0.5% and 1.0wt%) benefits the corrosion resistance due to relatively large impedance of oxide and delayed oxidation of Fe2 Nb particles. Porosities with Fe depletion are spotted in oxide and especially severe in 1.5wt%-Nb alloy. Cathodic Tafel kinetics and corrosion mechanisms of FeCrAl are further discussed. © 2022, The Authors. All rights reserved.

关键词： Oxide films

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Text digital watermarking technology based on graph theory

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Jisuanji Yanjiu yu Fazhan/Computer Research and Development 2007年第10期44卷 1757-1764页

作者： Liu, Dong Sun, Ming Zhou, Mingtian School of Computer Science and Engineering University of Electronic Science and Technology of China Chengdu 610051 China National Key Laboratory of Reactor System Design Technology Chengdu 610041 China

Because of text's properties, it's so difficult to find perfect algorithms of embedding watermark into text documents, when compared with other media. Nowadays, text watermarking technologies is far behind other multimedia watermarking technologies such as images, audios, etc. A novel text digital watermarking technology based on graph theory is presented in this paper. Through changing its topology structures of a character or string, different figures are schemed out, which represent the same semanteme. Then those figures are mapped on graphs of graph theory, and the graphs or their properties should be correctly encoded in order to denote different watermarking information. The mathematic models of embedding and detecting watermarking are also described, and the experimental methods of robustness and visual influence, as well as the relative results are given. Finally, general rules of removing attack on text watermarking system is proposed, and the attack-resisting capability and methods of this text digital watermarking is analyzed in detail. According to the experimentation and analysis, the text watermarking technology has the following advantages: great capacity of watermarking, strong robustness, little visual influence and quite good attack-resisting capability. With this technology, it is more convenient to embed watermark into characters for ideograph languages such as Chinese and Korean, while it is suitable for embedding watermark into strings for alphabetic languages such as English and French.

关键词： Digital watermarking

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An Adaptive Peridynamics with Correspondence Material Model for Coupled Creep-Plastic Fracture Problems

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SSRN 2024年

作者： Zhang, Hanbo Li, Chengxuan Liu, Zhenhai Ye, Hongfei Li, Hui Zheng, Yonggang State Key Laboratory of Structural Analysis Optimization and CAE Software for Industrial Equipment Department of Engineering Mechanics School of Mechanics and Aerospace Engineering Dalian University of Technology Dalian116024 China Science and Technology on Reactor System Design Technology Laboratory Nuclear Power Institute of China Chengdu610200 China

This paper introduces an adaptive peridynamics with a correspondence material model (A-PD-CMM) to effectively simulate the coupled creep-plastic behavior and the creep crack propagation in metal materials. In this method, to describe the coupled creep-plastic deformation with considering the creep damage, the multiaxial coupled constitutive model that integrates the Wen-Tu creep damage model and the J2 plastic model is developed. Moreover, a damage associate criterion is incorporated into the peridynamics framework to effectively capture the influence of damage on the force state. To detail the rapid damage evolution during the tertiary creep stage, a time-adaptive solving strategy is proposed. Additionally, the constitutive integration algorithm of the multiaxial coupled model is efficiently realized by decoupling it into two parts, that is, an implicit computation of creep-plasticity and an explicit evolution of creep damage. The efficacy and engineering applicability of the proposed A-PD-CMM are validated through several representative numerical examples, showcasing its potential in addressing complex material behavior. © 2024, The Authors. All rights reserved.

关键词： Crack propagation

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Investigations of Sodium Droplet Spreading and Evaporation on Surfaces with Different Wettability Based on Lattice Boltzmann Simulations

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SSRN 2024年

作者： Tang, Songsheng Guo, Kailun Tian, Zhixing Wang, Mingjun Wang, Chenglong He, Xiaoqiang Su, Guanghui Qiu, Suizheng Tian, Wenxi School of Nuclear Science and Technology State Key Lab. of Multiphase Flow in Power Engineering Shaanxi Key Lab. of Advanced Nuclear Energy and Technology Xi’an Jiaotong University Shaanxi Xi’an710049 China Key Lab. of Nuclear Reactor System Design Technology China Nuclear Power Research and Design Institute Chengdu610213 China

The spreading and evaporation of sodium droplets is one of the fundamental phenomena in high-temperature heat pipes. The LBM sodium two-phase flow and phase transition model, which can simulate a huge liquid-vapor density ratio, is first established and validated. Then, the spreading and evaporation processes of sodium droplets on solid walls with different wettability are numerically simulated and analyzed. The main conclusions obtained are as follows: (1) The dimensionless spreading diameter and time of the droplet spreading process conforms to Tanner's power law, and the power exponent has exponential relationship with the equilibrium wetting angle;(2) The maximum dimensionless spreading diameter is negatively and linearly correlated with the equilibrium wetting angle;(3) Evaporation of sodium droplets under constant heat flow conditions shows a mixed pattern. The droplets will be detached from the droplet wall at the late stage of evaporation, and the larger the equilibrium wetting angle the sooner the droplets detach. © 2024, The Authors. All rights reserved.

关键词： Evaporation

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Coupled Axisymmetric Peridynamics with Stabilized Correspondence Material Model for Ablation and Fracture Problems

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SSRN 2024年

作者： Zhang, Hanbo Liu, Zhenhai Li, Chengxuan Ye, Hongfei Zhang, Hongwu Li, Hui Zheng, Yonggang State Key Laboratory of Structural Analysis Optimization and CAE Software for Industrial Equipment Department of Engineering Mechanics School of Mechanics and Aerospace Engineering Dalian University of Technology Dalian116024 China Science and Technology on Reactor System Design Technology Laboratory Nuclear Power Institute of China Chengdu610200 China

A coupled axisymmetric peridynamics with a stabilized correspondence material model (CA-PD-SCMM) is proposed in this work to effectively simulate the ablation and ductile fracture behaviors of metals under high temperatures. To quantify the damage resulting from compression and shearing deformations, a strain energy density decomposition method is incorporated into the ductile damage model. Furthermore, a novel axisymmetric stabilization method based on peridynamics linearization theory is introduced to mitigate numerical oscillations arising from zero-energy modes in both thermal and mechanical scenarios. To capture the varying geometries and update the boundary conditions during ablation, a moving boundary model is developed based on temperature-associated criteria. To validate the capacity of the proposed CA-PD-SCMM, several representative numerical experiments are conducted. These examples not only affirm its ability to stabilize numerical oscillations in coupled axisymmetric thermoplastic problems but also demonstrate its capability for accurately simulating ablation and predicting crack propagation. © 2024, The Authors. All rights reserved.

关键词： Ductile fracture

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Evaluation of a Numerical Model for Predicting Flow and Heat Transfer in a Hexagonal Helical Cruciform Seven-Rods Bundle and Analysis of Rod Bundle Size Independence

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SSRN 2024年

作者： Jiang, Dianqiang Deng, Jian Zhang, Dalin Zhou, Xingguang Xiao, Changzhi Tian, Wenxi Qiu, Suizheng Su, Guanghui H. State Key Laboratory of Multiphase Flow in Power Engineering Shaanxi Key Laboratory of Advanced Nuclear Energy and Technology School of Nuclear Science and Technology Xi’an Jiaotong University Xi’an710049 China Nuclear Power Institute of China Science and Technology on Reactor System Design Technology Laboratory Chengdu610213 China China Institute of Atomic Energy Beijing611731 China

In this study, the accuracy and applicability of the numerical model are comprehensively evaluated based on the experimental data of a hexagonal helical cruciform (HC) seven-rods bundle. The STAR CCM+ is utilized as a tool to obtain predicted results of flow and heat transfer in different flow regions. The numerical results indicate that it is an improved method to set a negative heat flux on the hexagonal wall in the laminar flow region. The Reynolds stress transport model can accurately predict the experimental results of heat transfer in the transitional flow region, with an average wall temperature deviation of 2.8℃. The SST k-ω model with cubic constitutive option can accurately predict the experimental results of the flow resistance, and a relative error of f is 1.8%. In the turbulent flow region, the SST k-ω model with cubic constitutive option provides an accurate prediction, with an average wall temperature deviation of 3.7℃. The realizable k-Ε two-layer model can accurately predict the flow resistance, and the relative error of f is 0.1%. The preferred numerical model is used to analyze the size independence of the HC rod bundle. This work provides certain guidelines for the accurate simulation in the HC seven-rods bundle. © 2024, The Authors. All rights reserved.

关键词： Computational fluid dynamics

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