bluuebunny/crossref_metadata_2025_split huggingface dataset:
Power Performance and Response Analysis of a Semi-Submersible Wind Turbine Combined With Flap-Type and Torus Wave Energy Converters
Authors: Lee Chern Fong , Tryfonidis Christodoulos , Ong Muk Chen 
Published: December 2022

Abstract
An integrated offshore wind and wave energy system is an attractive concept in areas with abundant wind and wave energy resources. The sharing of supporting platform and facilities, e.g., mooring systems, offers significant cost savings. This will effectively lower the levelized cost of energy (LCOE). In the present study, a conceptual design consisting of a braceless semi-submersible floating horizontal axis wind turbine (FHAWT), three flap-type wave energy converters (WECs), as well as a torus (donut-shaped) point absorber-type WEC is proposed. The flap-type WECs harvest wave energy through the flap motion caused by oscillating wave surge, while the torus WEC absorbs wave energy generated from its heaving motion. The absorbed mechanical power of the power take-off (PTO) systems is calculated based on linear damping forces and the motions of the WECs relative to the supporting platform. Hydrodynamic interaction between the WECs and the supporting platform is considered by including the coupling terms in the added mass and potential damping coefficient matrices. A fully coupled aero-servo-hydro-elastic numerical model of the concept is constructed. The feasibility study of the concept is carried out using time-domain simulations. Only operational environmental conditions are simulated based on simultaneous wind and wave hindcast data of a selected offshore site. The effects of the WECs on the wind turbine, platform motions, and WEC power take-off are examined. Based on the power performance of WECs, recommendations are also provided for optimum power absorption.
A Finite Element Approach to Solve Incompressible Navier-Stokes Equations and Its Convergence Rate Analysis
Authors: Lu Qiyue , Bao Shiyi 
Published: December 2022

Abstract
Finite element methods for fluid flow problems are gaining more interests in nuclear engineering fields in recent years. Based on linear triangle elements, this work implements the algebraic subgrid scale (ASGS) stabilized finite element model for solving advection dominated incompressible fluid flows. The non-linearity is handled by the fixed point iteration. Verification is carried out using the method of manufactured solutions (MMS) for convergence rate analysis and the unit square lid-driven cavity benchmark problem.
Development of a Numerical Simulation Method for Air Cooling of Fuel Debris by JUPITER
Authors: Yamashita Susumu , Uesawa Shinichiro , Yoshida Hiroyuki 
Published: December 2022

Abstract
It is known that fuel debris is widely spread inside the primary containment vessel (PCV) at the Fukushima Daiichi Nuclear Power Plant (1F) by on-site observations. To retrieve fuel debris reliably and safely, it will be required that an accurate understanding of where and how much fuel debris locates in the PCV and how high the temperature of fuel debris rises. However, the details of the circumstances are not yet fully understood, and due to the high radiation dose, on-site investigation of it still has a lot of difficulties. Instead of on-site investigations, numerical simulations may provide essential information for the accurate understanding of thermal behaviors, including melt relocation behaviors, effects of unsteady natural convection around fuel debris, and the detailed temperature distribution inside fuel debris.
We focus on the development of a detailed numerical simulation method for unsteady natural convection around fuel debris. JAEA has developed the detailed three-dimensional thermal-hydraulics code, JUPITER, which was originally developed for the melt relocation behavior of core internals in severe accidents. JUPITER has governing equations for incompressible fluids, i.e., equations of the Navier-Stokes, heat conduction, the advection of free interfaces, and solute transport. Because fuel debris may exist as a porous medium, in this study, we newly implemented the equation of porous medium model in JUPITER to calculate natural convection induced by a decay heat of fuel debris. We confirmed that JUPITER gives a reasonable result for the temperature of fuel debris as a porous medium.
Study on Evaluation Method of Radial Power Reference Distribution of PWR
Authors: Wei Ting , Huang Yu , Yue Zhidong , Zhang Ying 
Published: December 2022

Abstract
The selection of radial power reference distribution is an important prerequisite and basic component of reactor safety analysis. In this paper, the reference radial power of a large PWR is calculated and evaluated in detail from 1/4 core and 1/4 hot assembly based on large data, and the following conclusions are drawn: (1) Based on the batch programming calculation of simple random reconfiguration, the influence of 1/4 core power distribution on the minimum DNBR value is negligible. (2) Based on the power capability analysis bank and the three-dimensional core physical accidents banks of rod drop, uncontrolled RCCA withdrawal at subcritical condition, uncontrolled single control rod withdrawal, RCCA ejection, steam line break, the power distributions of 1/4 hot assembly reconstructed by extracting the rod power distributions are evaluated, and it is concluded that the reference radial power distribution has enveloping property. Based on a large amount of data, the reference distribution is studied and evaluated, and it is verified that it can envelop possible distributions to meet the needs of core safety evaluation. Through the above evaluation research, a method to determine the radial power reference distribution of PWR is obtained, which can be used by engineers when designing the reference radial power distribution.
A CFD Method for Thermal-Hydraulic Calculation of Pebble Bed HTGRs
Authors: Zhu Junbing , Chen Fubing 
Published: December 2022

Abstract
The high temperature gas-cooled reactor (HTGR) is an advanced reactor type with safety characteristics of Generation IV nuclear energy systems. In the design process of an HTGR, thermal-hydraulic analysis is of great significance. This paper reviews existing methods for thermal-hydraulic calculation of pebble bed HTGRs and proposes a method for the two-dimensional (2-D) simulation using the commercial computational fluid dynamics (CFD) software ANSYS FLUENT. The pebble bed reactor core, fluid flow zones and control rod channels in the reflector are modeled with a porous media approach, while user-defined scalar (UDS) is employed for solving the governing equations of solid temperature in these regions. To incorporate radiation heat transfer among outer surfaces of the porous media region as well as their viewable walls into the calculation, some heat sources in thin layers adjacent to the walls are innovatively added. The method is applied to the steady-state simulation of the 10 MW high temperature gas-cooled reactor-test module (HTR-10). The fuel temperature is far below the safety limit, and the temperature values of the reactor internals agree well with the experimental results, showing that the CFD method adopted in this study predicts the temperature distribution well. Since the effect of radiation heat transfer on the temperature distribution is fully considered, the method can be directly applied to the simulations and studies of some accident conditions.
Numerical Simulation of Annular Dispersed Flow in Simplified Subchannel of Light Water Cooled Fast Reactor RBWR
Authors: Yoshida Hiroyuki , Naoki Horiguchi , Ono Ayako , Furuichi Hajime , Katono Kenichi 
Published: December 2022

Abstract
About the boiling transition (BT) that determines the maximum thermal output of the BWR, it is considered that the spacers have significant effects on the occurrence of BT. In the light water cooled fast reactor: RBWR, thermal-hydraulics conditions are more severe than the current BWR. Then, the effect of the spacer on BT should be sufficiently utilized in the RBWR. The RBWR is still in the design stage, therefore is not reasonable to determine the shape of the spacer by evaluation only for large-scale tests. In the occurrence of BT, it is considered that the two-phase flow pattern is the annular dispersed flow, and we want to evaluate the effects of spacer shape on annular dispersed flow in RBWR subchannels. This research uses the detailed two-phase flow simulation code TPFIT to simulate annular dispersed flow in RBWR subchannels.
As the first step of this research, we performed numerical simulations of annular dispersed flow in the simplified subchannel of RBWR. We used a circular tube with the same hydraulic diameter as the RBWR subchannel to consider the basic effects of spacer on the annular dispersed flow. In this paper, we describe the result of numerical simulation. In addition, we evaluated droplets’ size and velocity based on simulation results for the spacer’s existence and non-existence cases.
Assessment of Multiphase CFD Method for PWR Fuel Rod Bundle
Authors: Ren Bing , Gan Fujun , Yang Ping , Zhang Jie 
Published: December 2022

Abstract
This paper presents the assessment of the computational fluid dynamics (CFD) methodology for simulating the boiling flow in the Pressurized Water Reactor (PWR) rod bundle. The method includes the Eulerian-Eulerian two-fluid model coupled with the improved wall heat partitioning model. The effects of key phenomenological models are investigated based on the experimental data of vertical pipes. Then the integral validation of the method is carried out based on the NUPEC PWR Subchannel and Bundle Test (PSBT) International Benchmark, including the single sub-channel experimental data, and the full length of a PWR fuel assembly with multiple 5 × 5 spacers grid experimental data. The results agree well with the experimental results, which indicate the promising application of the present method for modeling the boiling flow under high pressure. Based on the validated method, the three-dimensional boiling flow in the fuel rod bundle is investigated, including the rod surface temperature, the bulk fluid temperature and the void fraction.
CFD Analysis on the Small Module Reactor (ACP100) PRS Return Line Thermal Stratification Phenomenon
Authors: Peiying Li , Cai Zhiyun , Zhang Yulong , Liu Hang , Liu Minghao , Ye Zhu , Tao Shuchang , Liu Xianghong 
Published: December 2022

Abstract
The return line of the passive residual system (PRS) of ACP100 is connected to the direct injection nozzle of the pressure vessel. It is a non-isolated dead pipe containing coolant, and there is no insulation layer. The temperature difference between the two sides of the pipe is large, which is prone to thermal stratification. This paper uses FloEFD software to carry out CFD simulation analysis and research on the thermal stratification phenomenon of the pipeline in normal operation and accident conditions. The scope of the return line analysis in this paper begins with the isolation valve at the outlet and ends with the direct injection nozzle on the pressure vessel. The finite volume method is used to solve the model, and the standard k-ε two-equation model is used for turbulence simulation. The pipeline system adopts a mesh refinement strategy according to the flow channel and wall thickness in the pipeline to obtain a reasonable mesh distribution. The results show that during normal operation, there is obvious thermal stratification at the exit of the PRS isolation valves, and there is a certain vortex in the tube, which can promote the heat exchange between the reactor pressure vessel and the PRS return pipeline; When PRS put into operation, a large temperature gradient is generated at the interface of the annular cavity of the pressure vessel, and the influence of thermal stress and cyclic thermal shock needs to be considered, and an obvious vortex will be formed nearby to promote the rapid heat exchange of cold and hot water in the nearby area. The result of this paper can provide input for PRS return line thermal stress and thermal cycling impact analysis.
Study on the Applicability of a Machine-Learning Framework to Improve Modeling for the Stratification Phenomenon
Authors: Oda Takuo , Okayasu Shimpei , Hara Nobuhide , Tanimoto Koichi , Haghiri Ali , Xu Xiaowei , Sandberg Richard 
Published: December 2022

Abstract
In chemical plants, heat storage systems, nuclear power plants, etc., when hot water is injected into a tank containing cold water, mixing of hot and cold fluid is suppressed by buoyancy effects and thermal stratification can occur. This leads to the deterioration of heat storage capability and the effect of thermal stratification can adversely affect the structure. Therefore, a measure for eliminating thermal stratification was constructed and its effectiveness was examined by CFD analysis. Since the fluctuations in the gravity direction are suppressed by buoyancy in the thermal stratification field, the prediction accuracy becomes low when RANS based on the isotropic eddy viscosity hypothesis like the conventional k-ε model is used. Although the above phenomena can be predicted by performing a high-precision analysis such as LES analysis, the analysis cost becomes enormous and it is unsuitable for design evaluation. In this study, turbulent heat flux and anisotropic Reynolds stress were modeled using a Gene Expression Programming (GEP) framework. In the GEP framework of this study, a non-linear Reynolds stress relationship is constructed by adding non-linear terms to the linear Boussinesq approximation and the turbulent Prandtl number is expressed as a function of velocity and temperature gradients. This modeling is based on an LES dataset. RANS analysis was carried out using these two models on a test case different from the training case, and calculation results are compared with experimental test results. As a result, the decay of the thermal stratification phenomenon was reproduced with high accuracy. This paper introduces this new turbulence modeling process.
Virtual Design of Integrated Bottom Head Quenching Scheme
Authors: Wang Jing , Wang Xiaofang , Gu Jianfeng 
Published: December 2022

Abstract
CAP1000 reactor pressure vessel integrated bottom head was the integrated stamping molding of transition section and spherical bottom head forgings. The integrated bottom head forging was too deep, so it was difficult to control the quenching uniformity of head forgings opening and dome. In addition, the wall thickness of the integrated bottom head forgings was almost to 300mm. In order to make the forgings qualified performance, the overall quenching cooling effect of the forgings was need to be improved. In this paper, computational fluid dynamics (CFD) method was used to carry out the numerical simulation of mixing flow field of the integration bottom head in a quenching tank with screw. In order to improve the uniformity and speed of the flow in the vicinity of the head, different quenching schemes of the integrated bottom head were designed virtually and simulated. The placement of the head, the diversion device and the pumping device are all design factors. Eventually, the quenching scheme with bottom three-stage diversion and internal pumping with extended tapered guide was adopted for the deep and thick integration bottom head. The integrated bottom head with this quenching scheme was successfully trial-produced. And the tensile properties, impact properties and drop hammer results of each sampling position meet the product performance requirements with more margin.
A Numerical Investigation of the Mixing in the VCT During the Dilution Process
Authors: Zhang Shengshuai , Wang Naihua , Chi Xiangyu 
Published: December 2022

Abstract
The Volume Control Tank (VCT) is an indispensable device ofChemical and Volume Control System in the primary loop. The incoming water cannot be quickly mixed with the original boric acid solution in the VCT during the dilution process. The poor mixing would delay the reactive control of the core, which increases the time consumption of nuclear power plant operations and brings adverse impacts on core stability. A numerical investigation of the mixing in the VCT during the dilution process is carried out. The numerical methods were validated by experimental data. It is found that there are two different mixing modes in the tank, and the mixing and flow characteristics under different mixing modes are analyzed. It is found that the concentration stratification increases the flow resistance, which has a negative impact on the mixing. Increasing the inlet velocity can effectively avoid stratification and improve mixing efficiency. Increasing the jet density difference will aggravate the stratification in the tank, and even cause the phenomenon of double stratification. The work in this paper has certain guidance for understanding the internal fields in the VCT during the dilution process and improving the mixing efficiency in the VCT.
A Sensitivity Analysis of Condensation Phenomena for a Passive Containment Cooling System by Using Code_Saturne Coupled With OpenTURNS
Authors: Chen Ru , Liang Ronghao , Zhou Lu , Min Jiesheng 
Published: December 2022

Abstract
Computation-expensive problems have become more common in nuclear industry, originating from expensive analysis with the aim of reaching high accuracy. To overcome this challenge, surrogate modelling techniques are often proposed.
Passive containment cooling system (PCCS) is an essential pattern to ensure the containment integrity in the case of accidental conditions for AP600 reactor, so determination of the most influential parameter as regards the heat transfer rate is of great significance to the optimization design and security analysis of nuclear power plants.
This paper contributes to uncertainty quantification in condensation phenomena for PCCS. The purpose is to create a surrogate model instead of a deterministic model for sensitivity analysis on the account of saving computational time. The case used is an experiment carried out in 1998 for which the data is publicly available and was selected here as a showcase of the meta-model construction. In this paper, the database conducted by Anderson in 1998 is used to validate the computational fluid dynamics (CFD) model. By coupling Open-source CFD code code_saturne and uncertainty analysis code OpenTURNS from the SALOME Platform, a representative sample of input and output parameters is obtained using the design of experiments (DoE) technique. Thus, a surrogate model, including kriging and polynomial chaos metamodel, is constructed. In this way, sensitivity analysis of condensing efficiency is performed, which demonstrates the propagation of modeling uncertainty of condensation phenomena.
Numerical Model Development for the Transient Heat and Mass Transfer Performance of a Water-Copper Wicked Heat Pipe
Authors: Liu Jian , Jiang Xingchi , Shah Syed Waqar Ali , Li Yuanjie , Hu Chongju , Yu Dali , Li Taosheng , Pan Chin 
Published: December 2022

Abstract
The application of heat pipes in space nuclear reactors, radiators, and thermal management has gained an enormous amount of attention nowadays. A 3D transient model is needed to study the flow and heat transfer characteristics when considering the complex processes and conditions such as the start-up process, power variation process, non-uniform heating condition, microgravity condition, and so on. In this study, a 3D CFD model for water-copper wicked heat pipe was developed to predict the transient characteristic of heat pipes. A novel source terms method was used through user-defined functions (UDFs) to calculate the evaporation and condensation rates on the water-vapor interface. The laminar flow hypothesis was applied to the flow region. The compressibility of liquid and vapor was considered and the ideal gas equation was adopted for the vapor flow. The Darcy flow characteristic of liquid wick flow was considered in the porous wick region. The simulated outer wall temperature, velocity, pressure, and temperature variation of the wick and vapor during the startup process were obtained and compared with the experimental data. Good prediction results were obtained under the same conditions. The heat flux on the condenser wall will increase quickly due to the quick response-ability of heat pipes. The max vapor velocity shows a minor decrease trend due to the vapor pressure recovery. The distribution of vapor temperature has a significant non-uniformity due to the compression work at the initial time. The beginning of the condensation point will migrate to the condenser section in the start-up process. This study can provide both knowledge and tool for the design of space thermal radiators.
Study on the Radiation Heat Transfer Effect of the Covered Gas Space of the Pool Reactor
Authors: Luo Xinyue , Lu Daogang , Feng Jiaqi , Zhang Yuhao 
Published: December 2022

Abstract
The construction of fast reactor main vessel’s roof slab consists of large argon cavity, plug cock, part of biological shielding column, main pump and heat-exchangers as well as a large number of small-size air gap between plug cock and argon cavity. Therefore, it has an important significant to carry out a thermal hydraulic behavior research on blanket gas top of the main vessel for getting detailed temperature distribution. The temperature field in the headspace of the main vessel of the sodium-cooled fast reactor is of great significance to the analysis of the structural integrity of the reactor. The construction of fast reactor main vessel’s roof consists of large argon cavity, plug cock, Because of the enormous structure of argon cavity. Due to the large space structure of argon gas at the top of the main container, large space and micro-slit space exist at the same time, two orders of magnitude different, which brings difficulties to the theoretical analysis of temperature field. In order to study the distribution of temperature field in the top space of the main vessel, ANSYS series of computational fluid dynamics (CFD) software used to model and simulate the top space of the main vessel of the sodium cold fast reactor. Therefore, based on the existing data, this paper conducts a more detailed simulation study on the thermo-hydraulic behavior of the covering gas in the complex space on the top of the main container of fast reactor. The calculation shows that the symmetry of calculation is good and the flow process is in line with the natural circulation caused by temperature difference. The simulation results are good and can used as the basis and reference for further analysis, which is of positive significance to reactor operation safety.