bluuebunny/crossref_metadata_2025_split huggingface dataset:
New Turbulent Prandtl Number Model for Liquid Metal Based on DNS Results
Authors: Fu Hao , Zhao Houjian , Li Xiaowei , Wu Xinxin , Lyu Xuefeng , Liu Fang , Yu Yu , Xu Wei 
Published: November 2024

Abstract
Liquid metal is widely used as the primary coolant in many advanced nuclear energy systems. Prandtl number of liquid metal is much lower than the conventional coolant of water. Due to the high molecular thermal diffusion coefficients of liquid metal, the thermal conduction dominated region of liquid metal is much thicker than that of water. Logarithmic region for dimensionless temperature in the cross section is diminished due to the low Prandtl number effects. Conventional Nusselt number correlations derived from the logarithmic temperature distribution can not be used for liquid metal. For conventional coolant of water or air, the turbulent momentum field is similar with turbulent scalar field. Based on Reynolds analogy, the turbulent Prandtl number is assumed as one for the Reynolds Averaged Navier Stokes method. For turbulent convection of liquid metal, dissipations of turbulent scalar energies are larger than that of turbulent kinetic energies. Dissimilarity between the thermal and momentum field increases with the decreasing of Prandtl number. For turbulent convection of liquid metal, the turbulent Prandtl number is larger than one.
In the current investigation, turbulent convection of liquid metal in channel is directly simulated with OpenFOAM. Turbulent statistics of the momentum and the thermal field are compared with the existed database to validate the numerical model. Power law for dimensionless temperature distribution with different Prandtl number is obtained by regression analysis of DNS results. New Nusselt number correlation is derived based on the power law of temperature distribution. The new Nusselt number correlation agrees well with the DNS results in the literature. Using the method of order magnitude analysis, relationships between the turbulent heat flux and turbulent scalar energy is analysed. Turbulent scalar energy is used to calculate the turbulent thermal diffusion coefficients. New correlation is proposed to consider Prandtl number effects on dissimilarity between the turbulent kinetic energy and the turbulent scalar energy. Then, new turbulent Prandtl number model for liquid metal is obtained. Combined with SST turbulence model, numerical results with the new turbulent Prandtl number model agree well with DNS results. The new Prandtl number model can be used for turbulent convection with different Prandtl number and with different Reynolds number.
Experimental Study of the Effect of Pulsatile Flow on Corner Vortices at the Sudden Contraction Before the Inlet of Two Parallel Narrow Rectangular Channels
Authors: Ala Ayodeji , Ye Bin 
Published: November 2024

Abstract
Corner vortices can be found in regions where there is considerable flow expansion or contraction. Experimental measurement was used to investigate the changing vortices at the contraction region before a dual parallel channel arrangement. The flow in the loop was pulsatile with a flow period of 5 s, amplitude between 0.2 and 0.4, and flow rate in the range of 0.4 m3/h to 0.9 m3/h. The mean transient flow rate in the loop was within ± 6% of the ideal sinusoidal fluctuation at lower amplitude. The corner vortices were analyzed by their change in size during pulsation and the turbulence structure in the contraction area. The corner vortexes are quasi-symmetrical at the channel corners below the contraction plane. The corner vortices were larger when the flow velocity was off-peak. Regions of slower flow increased during the deceleration half-cycle of the pulsatile flow. The results provide more explanation of flow behavior at channel corners and contraction planes.
Exploration of Ultra-High Performance Concrete (UHPC) Application in Nuclear Power Plant Structures
Authors: Peiyao Zhang , Mengyan Song , Di Jiang , Jingwei Gao 
Published: November 2024

Abstract
Ultra-High Performance Concrete (UHPC), as a rapidly developing high-performance cement-based material in recent years, has three major characteristics: high strength, high ductility, and high durability. Based on these characteristics, UHPC offers the potential for conducting “ultra-long life” highways or bridges. Therefore it was initially applied in bridge structures. Due to the safety requirements of nuclear power plants and the fact that most nuclear power plants are distributed along the coast, the material properties of UHPC are very suitable for the structures of nuclear power plants. Currently, UHPC has been preliminarily applied in Nuclear Power Plants. In this paper, a new type of containment structure called UHPC containment is proposed and studied. The finite element analysis is carried out on the UHPC containment by varying the different tensile strength and reinforcement ratios. The results obtained from finite analysis are compared with those from the current pre-stressed concrete containment structures to discuss the feasibility of applying UHPC in such structures. The findings suggest that reasonable use of UHPC can contribute to the enhanced safety of containment structures. Finally, this study proposed required material characteristics and design methods for this new type of UHPC containment structure.
CFD-DEM Simulation on Gas-Solid Separation and Sphere Packing Behaviors in a Storage Bin of the Small Absorber Sphere System
Authors: Li Tianjin , Hu Haitao , Yan He , Diao Xingzhong 
Published: November 2024

Abstract
The small absorber spheres system is one kind of shutdown system in the pebble-bed High Temperature Gas-cooled Reactor (HTGR or HTR). Vertical pneumatic conveying of small absorber spheres in pebble-bed HTGR is a special application of pneumatic conveying technique. The whole process consists of several sub-processes, e.g., the granular discharge from the sphere storage bin into the boring, granular discharge from the side reflector boring into the feeder, particle entrainment in the feeder, sphere conveying in the transport pipeline, and gas-solid separation in the storage bin. The Computational Fluid Dynamics and Discrete Element Method (CFD-DEM) coupling simulation has recently been extended and used to investigate particle vertical conveying in the small absorber sphere system in our previous work. In this study, we further investigate the gas-sphere separation and sphere packing behaviors in a storage bin of the small absorber sphere system by CFD-DEM coupling simulation, to make a better understanding of the gas-solid flow and particle flow behaviors in the small absorber spheres system. The influence of operation parameters is considered, including gas velocity, particle velocity and solid flow rate. The effect of gas and solid properties are also considered, including media type (high pressure Helium and ambient air) and friction coefficient of the sphere and wall. Attention is paid to the sphere motion behaviors and heap up characteristics of the spheres in the storage bin, to gain more knowledge of the evolution of heap up surface for the design of sphere level indicator.
Application of Plasma Arc Cutting Technology in Dismantling of Large Metal Components in Containment Building
Authors: Zhang Naizhe , Wang Weishuai , Gao Zhen , Liu Hai , Liu Xuegang 
Published: November 2024

Abstract
The decommissioning of nuclear reactor is a challenge to the sustainable development of nuclear energy. One of the most challenging tasks in reactor decommissioning is the dismantling and segmentation of radioactive large metal components in the containment building. A variety of cutting technologies have been developed for the special purpose. This paper is focused on the underwater plasma arc cutting technology and its potential applications.
The characteristics of large metal components in nuclear containment building were summarized. The matters needing attention in the process of dismantling and segmentation were analyzed as well. The technical principle of plasma arc cutting was briefly introduced, and the selection of the key operational parameters are discussed, such as the types of gas and electrode materials.
Cutting noise, arc light, and smoke will be efficiently reduced by underwater cutting. More importantly, underwater cutting can reduce the radiation dose to the occupational staff and optimize the radioactive waste management. A comparative evaluation was conducted among underwater plasma arc, arc saw and wire saw cutting. In the last part, a hypothetical scenario taking a steam generator as an example for dismantling is proposed and analyzed. The differences between the plasma arc cutting and the arc saw cutting were compared in terms of cutting time and the amount of secondary waste generation.
In this paper, the underwater plasma arc cutting was comprehensively analyzed and discussed to validate the technology in the decommissioning of large metal components in the containment building. Some concerns for industrial application were revealed.
Thermohydraulic Simulation of Energy Well Micro Modular Reactor Using System Codes
Authors: Mazzini Guido , Benčík Marek , Reungoat Mathieu 
Published: November 2024

Abstract
Due to the actual energy need worldwide, which should be carbon oxide emission free, several initiatives to prepare advanced Small Modular Reactor (SMR) and Micro Modular Reactors (MMR) are ongoing in order to offer new energy solutions (not only for electrical production) with high standard in safety. The goal of these technologies is to obtain clean energy with low carbon emission, which will be located nearby industries or cities. In particular, several countries such as United States of America, Great Britain and Canada plan to build a fleet of SMRs in order to find a compromise between, the actual energy needs, the construction period and investment cost. Particular attention is given to the Gen. IV reactors, which are bringing new solutions and aspects in the nuclear panorama. One of the goals is the practically elimination of severe accident addressed by approaches and phenomena, which are considered during the design of SMRs and MMRs. For this reason, the SMRs development is conditioned by a portfolio of technological solutions, which are currently in preparation, and by the readiness of the supervisory authority to legislatively regulate the construction, operation and supervision.
One of these concepts is Energy Well (EW), an MMR developed in Centrum Výzkumu Rez (CVR) located in the Czech Republic with support of a national consortium, which includes universities and other Czech companies. Especially, CVR uses its experience of more than 60 years in running research reactors, which has several similarities with MMRs, to design EW and to build several facilities useful to assess the molten salt technology. Several activities are ongoing in a framework of a project financed by the Technologická agentura České republiky (TAČR).
Part of these activities focuses on thermohydraulic assessment and safety analyses, which are performed by CVR and Nuclear Research Institute (UJV) in a parallel benchmark activity. The codes used in these activities are TRACE 5 patch 7 developed by Nuclear Regulatory Commission (US NRC) and RELAP5-3D developed at Idaho National Laboratory, which offer several working fluids represented in different equation of states. The aim of the analyses is to provide the results of a benchmark, particularly, assessing the capability of TRACE and RELAP to analyze molten salt technology. Additionally, the EW thermohydraulic will be investigated starting from the steady state and reaching a transient analysis. Particular attention will be given to the point kinetic module, which is introduced and implemented into the models to study the core behavior under extreme accident conditions.
Understanding the Flow Anisotropic Turbulent Flow in the Subchannel of Fuel Assembly Under Effect of the Bare Rod and Mixing Vane Grid by LES
Authors: Qi Siwei , Han Bin , Xing Tianyang , Zhu Xiaoliang , Yang Bao-Wen , Yin Yuanyuan , Liu Aiguo , Liu Shenghui 
Published: November 2024

Abstract
The grid has the functions of supporting fuel rod bundles and mixing the coolant. The flow of the coolant through the mixing vanes increases its perturbation, which directly affects the Critical Heat Flux Density (CHF) of the reactor core, enhances the wall heat transfer performance, and improves the safety and economy of the reactor. The geometric asymmetry of the sub-channels in the Pressurized Water Reactor (PWR) fuel assemblies leads to anisotropy in the flow, and accurate prediction of the flow mixing characteristics in the rod bundle channels plays a significant role in the prediction of the onset of nucleate boiling and CHF. Traditional RANS turbulence models struggle to accurately predict the anisotropic turbulent flow in rod bundle channels. This paper, based on LES simulation calculations, investigates the anisotropic flow characteristics in 2 × 1 and 3 × 3 bare rod channels, comparing the effects of different sizes of rod bundle geometries on flow anisotropy. On this basis, the study examines the anisotropic turbulent flow in rod bundle channels under the influence of a 3 × 3 grid. By conducting Large Eddy Simulations (LES) on the flow field of a simple 3 × 3 rod bundle sub-channel, this paper analyzes the impact of grid mixing vane angle variations on the flow anisotropy between nuclear fuel rods. The results show that changes in the grid mixing vane angles can produce varying degrees of flow field perturbations. The study of the evolution of turbulent anisotropy between rods under the coupled effect of rod bundle channels and grids, and flow field characteristics, lays the foundation for the construction of URANS models that can accurately reflect anisotropic effects, and also establishes a basis for the design of high-performance fuel assembly grids.
Impact of Tube Fouling on Steam Generator Performance Using a Thermal-Hydraulic Code
Authors: Jing Liu , Zhen Li , Zhenqin Xiong , Yuan Gao , Yuchen Lin , Linpeng Shi 
Published: November 2024

Abstract
In order to study the deposition and distribution of Fe3O4 fouling and its impact on the thermal performance of steam generator (SG), numerical simulation model of SG has been developed based on porous medium model. The impact of Fe concentration of feed water on the fouling deposition characteristics and the thermal performance of steam generator has been quantitatively analyzed. The fouling deposition mass after ten-year operation is 65.0 and 166.5 kg for Fe impurity concentration in the SG feedwater 1ug/kg and 3ug/kg, respectively. The thermal power is decreased by 1.2% and 3.1% compared to the situation without fouling accumulation, respectively. The heat flux degradation and the thermal resistance due to fouling of tubes in different locations of SG are compared. The mean heat flux of the shortest tube in the central region is most serious affected by fouling deposition. The fouling thermal resistance contributes to 12%∼25% of the thermal resistance along the bend for Fe concentration 2ug/kg and ten-year operation, while it is in the range of 3–21% and 0–6% for the straight pipe section on the hot side and on the cold side, respectively.
Optimization Design Study of a Radiant Heat Exchanger for a Small-Scale Underwater Nuclear Power Plant’s Residual Heat Removal System
Authors: Guo Yinan , Li Lei , Wen Yongsheng 
Published: November 2024

Abstract
With the continuous development of small-scale underwater nuclear power plants, the need to develop residual heat removal systems for underwater nuclear power plants has become urgent. The efficient and lightweight residual heat removal system is one of the key research directions that need to be developed. The mass and volume of the heat exchanger of a small-scale underwater nuclear power plant account for a large proportion of the residual heat removal system. The heat exchanger in the residual heat removal system in the liquid metal-cooled nuclear reactor of a small-scale underwater nuclear power plant adopts radiant heat exchange, and the fins of the radiant heat exchanger are made of graphite carbon fiber composite material with a rectangular structure. The heat exchanger and heat trap are filled with nitrogen gas. This paper proposes to replace the rectangular cross-section structure of the radiant fins with the triangular structure of the heat exchanger fins. The heat transfer performance of the optimized structure of the radiant heat exchanger is investigated using Fluent. The results show that the optimized triangular fin structure of the radiant heat exchanger makes the residual heat removal system have a better performance of the radiant heat exchanger. The weight of the optimized system is reduced by 16.53%.
Calculation of Noble Gas Ion Mobility Based on SRK EOS Under High-Pressure
Authors: Chang Jiahao , Fu Jintao , Tang Peng , Liu Haoyu , Wang Zhentao , Wu Zhifang 
Published: November 2024

Abstract
The time response characteristic of detectors in radiation imaging systems holds significant importance, and the response time of the detector will influence the image quality of the imaging system. However, the extended response time of parallel plate ionization chamber detectors currently in use contributes to image blurring. Enhancing the imaging quality necessitates a reduction in detector response time. There are many ways to reduce the response time of ionization chamber detectors. Modifying the working gas within the detector and opting for a working gas component with high ion mobility, while keeping the detector structure unchanged, has proven effective. Typically, gas detectors in radiation imaging systems contain noble gases at high pressure. To select the appropriate working gas components, we need to measure the mobility of ions of different gas components at high atmospheric pressure. Measuring the mobility of ions at high atmospheric pressure requires an accurate calculation of the molecular number density, and it is vital to choose an appropriate equation of state (EOS) for the gas. Hence, this paper suggests a method for calculating molecular number density grounded in the Soave-Redlich-Kwong (SRK) gas equation of state. It involves deriving the explicit form of the SRK equation and integrating an iterative approach to compute molecular number density in high-pressure gases. In order to compare the calculated results of different gas equations, various gas equations of state such as the Van Der Waals (VDW), Peng Robinson (PR) equation, ideal gas equation of state, etc. are utilized in this paper. The calculated results of the above equations are compared with the National Institute of Standards and Technology (NIST) data. The calculated results show that the SRK EOS is closer to the real value. The calculated results of the ideal gas equation of state deviate the most from the actual value. For some gases (e.g., krypton), the van der Waals equation has no real-number solution when the gas pressure is more than 2900KPa. Thus, in the subsequent measurements of the ion mobility of noble gases under high-pressure conditions, the ion mobility can be calculated with the assistance of the SRK equation and more accurate data can be obtained.
Investigation of Reverse Flow in the Passive Residual Heat Removal System of NHR-200II
Authors: Geng Yiwa , Li Ziyi , Liu Xiongbin , Huang Shuliang , Qin Haiqi 
Published: November 2024

Abstract
The NHR-200II is a multi-purpose small integrated pressurized water reactor (PWR). Its passive residual heat removal system (PRHRS) to remove core decay heat. During a series of PRHRS experiments conducted in a scaled integral test facility for the NHR-200II, a reverse flow phenomenon was observed. To study this phenomenon, a system model using the RELAP5 code was developed for the integral test facility, and the reverse flow phenomenon was numerically simulated. The system code was used to calculate the flow rate and heat transfer power of each RHE and PHE branch under the test conditions. The calculated flow rates in the PHE branches showed good agreement with the observed reverse flow phenomenon in the test facility. Similarly, the flow rate and heat transfer power of the RHE branch matched well with the experimental data. The cause of the reverse flow phenomenon is attributed to the asymmetric location of the RHE branch on the hot and cold headers relative to the PHE branches. The non-uniformity flow rates in the PHE branches are caused by the different distances between the RHE and each PHE branch. Although small initially, this non-uniformity is amplified by the positive feedback effect of pressure drop and flow rate between the PHE branches, eventually resulting in reverse flow. To address the reverse flow phenomenon in the PRHRS, two methods are proposed. The first method involves reducing the length of the ring header, while the second method focuses on increasing the buoyancy force of the natural circulation system. The effectiveness of these methods is calculated and discussed. This paper highlights the NHR-200II reactor PRHR system, discusses the observation of reverse flow in experiments, describes the numerical simulation using a system model, and proposes two potential methods to mitigate the reverse flow.
Intelligent Fault Diagnosis of Rotating Machinery Based on Deep Neural Network
Authors: Zhang Xiuchun , Xia Hong , Liu Yongkang , Zhu Shaomin , Jiang Yingying , Zhang Jiyu , Liu Jie , Yin Wenzhe 
Published: November 2024

Abstract
In order to improve the fault diagnosis for rotating machinery in nuclear power plants, this paper proposes a fault diagnosis model based on short-time Fourier transform (STFT) and Residual Network (ResNet), using information from multiple sensors. Firstly, acceleration sensors are installed on the different positions of the motor to measure vibration signals, and the normal condition and eight typical faults of the motor are simulated by the mechanical fault simulation test platform. Then, sensor signals from different positions of the motor are obtained as inputs to the fault diagnosis model to reduce the impact of the fault feature attenuation during mechanical propagation. In data preprocessing, STFT is used to convert the multi-source signals from time domain to time-frequency domain to extract the fault features of the signals. Finally, ResNet is used to further extract advanced features from time-frequency feature signals and identify fault patterns. Results obtained show that the proposed model based on STFT, ResNet and multi-sensor information strategy can accurately classify the fault modes, and comparisons with the traditional convolutional network model and single sensor strategy model highlight the advantages of the proposed method in rate of convergence, accuracy and noise robustness.