bluuebunny/crossref_metadata_2025_split huggingface dataset:
Design and Operational Challenges of Switching Working Fluid for a Gen IV Nuclear Powered Closed-Cycle Gas Turbine: Case Studies of Nitrogen and Air, Helium and Argon
Authors: Osigwe Emmanuel O. , Gad-Briggs Arnold , Tukur Nasiru , Pilidis Pericles 
Published: October 2020

Abstract
A unique benefit of using the closed-cycle gas turbine and gas turbomachines employed in the Gen-IV nuclear power plant is the flexibility it offers in terms of working fluid usage. This is so because of the self-containing nature of the closed-cycle gas turbine. To this end, the selection of the working fluid for the cycle operation is driven by several factors such as the cycle performance, system design, and component material compatibility with fluid properties, availability, and many more. This paper provides an understanding of the design and operational challenges of switching working fluids for a nuclear powered closed-cycle gas turbine. Using the plant output power of a simple closed-cycle configuration as a baseline condition, two case studies have been presented in this paper to explore the design and operational challenges of switching working fluids. In the first case study, the fluid was switched from nitrogen to air and in the second case study, helium and argon were utilised. In both cases, using thermodynamic flow relationship, the closed-cycle gas turbine turbomachinery components maps were analysed to understand the operational requirements for switching the working fluids. The paper also provided an insight into the turbomachinery component design considerations for this to be achieved. The overarching results from a thermodynamic perspective showed fluids with similar thermodynamic behaviour could be switched during idle synchronous speed.
Experimental Study on the Thermal Properties and Stability of Hybrid Nanofluids and Evaluation of its Heat Exchange Efficiency
Authors: Xiao Yubai , Zhang Hu , Wu Junmei 
Published: October 2020

Abstract
In recent years, hybrid nanofluids, as a new kind of working fluid, have been widely studied because they possessing better heat transfer performance than single component nanofluids when prepared with proper constituents and proportions. The application of hybrid nanofluids in nuclear power system as a working fluid is an effective way of improving the capability of In-Vessel Retention (IVR) when the reactor is in a severe accident. In order to obtain hybrid nanofluids with excellent heat transfer performance, three kinds of hybrid nanofluids with high thermal conductivity are measured by transient plane source method, and their viscosity and stability are also investigated experimentally. These experimental results are used to evaluate the heat transfer efficiency of hybrid nanofluids. The results show that: (1) The thermal conductivity of hybrid nanofluids increases with increasing temperature and volume concentration. When compared to the base fluid, the thermal conductivity of Al2O3-CuO/H2O, Al2O3-C/H2O and AlN-TiO2/H2O nanofluids at 0.25% volume concentration increased by 36%, 24%, and 22%, respectively. (2) Surfactants can improve the stability of hybrid nanofluids. The Zeta potential value is related to the thermal conductivity of the hybrid nanofluids, and it could be used to explain the relationship between the thermal conductivity of the hybrid nanofluids and the dispersion. It also could provide a reference for subsequent screening of high thermal conductivity nanofluids. (3) The addition of C/H2O can effectively reduce the dynamic viscosity coefficient of hybrid nanofluids. (4) The analysis of heat transfer efficiency of the hybrid nanofluids found that both Al2O3-CuO/H2O and Al2O3-C/H2O have better heat transfer ability than water under certain mixing conditions. This study is conducive to further optimizing hybrid nanofluids and its application to the In-Vessel Retention in severe reactor accidents.
Study on Preparation Process and Properties of High Hydrogen Content Concrete for Neutron Shielding
Authors: Yuanyuan Li , Xiaoqiang Pan , Xiulin Huang , Ying Wu , Jing Yang 
Published: October 2020

Abstract
A series of concrete samples with high hydrogen content were prepared by pressing process with aluminum hydroxide, boron carbide and aluminate cement as raw materials. the mechanical performance of the shielding material was examined by flexural strength tester and compression strength tester. Thermogravimetric analyzer was used to test the weight loss performance of the shielding material, hydrated cement and Al(OH)3. The thermal stability of the concrete at working temperature were investigated by bake the samples at 210°C for 90 hours and at 300°C for 5 hours. The shielding performance against neutron from 241Am-Be source were examined by neutron penetration tests. The test results show that the mechanical properties of the shielding material decrease with the increase of the content of aluminum hydroxide, the compression strength of the shielding material reached above 10MPa. The decomposition temperature of conc is 220°C, the weight loss curve tends to be plateau after baking at 210°C for 20 hours. Most of the crystal water lost after holding at 300°C for 5 hours, but the dimensions of the samples show no obvious change. The shielding performance of the material against neutron from 241Am-Be source is comparable to that of lead-boron polyethylene.
Artificial Neural Network Model for Diagnosing the Performance and the Conditions of Air-Operated Valves
Authors: Kim Taeyun , Chai Jangbom , Lim Chanwoo , Han Ilyoung 
Published: October 2020

Abstract
Air-operated valves (AOVs) are used to control or shut off the flow in the nuclear power plants. In particular, the failure of safety-related AOV could have significant impacts on the safety of the nuclear power plants and therefore, their performances have been tested and evaluated periodically. However, the current method to evaluate the performance needs to be revised to enhance the accuracy and to identify defects of AOV independently of personal skills. This paper introduce the ANN (Artificial Neural Network) model to diagnose the performance and the condition altogether.
Test facilities were designed and configured to measure the signals such as supply pressure, control pressure, actuator pressure, stem displacement and stem thrust. Tests were carried out in various conditions which simulate defects with leak/clogged pipes, the bent stem and so on. First, the physical models of an AOV are developed to describe its behavior and to parameterize the characteristics of each component for evaluating the performance. Secondly, CNN (Convolutional Neural Network) architectures are designed considering the developed physical models to make a lead to the optimal performance of ANN. To train the ANN effectively, the measured signals were divided into several regions, from each of which the features are extracted and the extracted features are combined for classifying the defects. In addition, the model can provide the parameters of maximum available thrust, which is the key factor in periodic verification of AOV with the required accuracy and classify more than 10 different kinds of defects with high accuracy.
Experimental Study of Boiling Characteristics of Seawater After an Accidental Shutdown of the Pump
Authors: Li Yuanjie , Ren Shuai , Pan Chin 
Published: October 2020

Abstract
Water is the most common working fluid using as the coolant for most of nuclear power plants due to its low cost, wide availability, and high heat capacity. In the Fukushima Daiichi accident caused by the tsunami following a powerful earthquake on 11th March 2011, the loss of heat sink occurred. Seawater, which had been considered as an alternative coolant before, was eventually injected into the nuclear reactor for more than one week as an emergency measure. The studies about the characteristics of heat transfer with the seawater as the working fluid have received much more attentions after the Fukushima Daiichi accident. The differences of thermophysical properties such as density, dynamic viscosity, and surface tension, between deionized water and seawater play an important role in the heat transfer. In addition, different boiling behaviors exhibit in the boiling process for two types of working fluid. Compared to pure water, the diameter of bubbles in seawater during pool boiling could be smaller than in water. To improve the safety of a nuclear reactor power plant, mechanisms of the heat transfer using seawater as an alternative emergency coolant should be studied thoroughly. In the present research, experiments of pool boiling in an annulus gap with a riser section after the sudden shutdown of the pump are investigated. Heat transfer characteristic of the heated surface using DI water and 3.5 wt% artificial seawater are described. Boiling behaviors at each fluid are compared and studied.
Research on Cooling Water Source Safety Measures in Water Intake Engineering of Coastal NPP
Authors: Ben-jing Tang , Shu-qiang Hou , Yan-long Wang , Jing Li 
Published: October 2020

Abstract
In view of the situation that large amounts of marine sewage and organisms enter into the cooling water intake system of a coastal NPP at BeiBu-bay, China, which affects the safe and stable operation of NPP, the optimization research on blockage prevention in the water intake engineering is carried out. Based on the statistical analysis of a large number of NPPs’ cooling water source safety incidents globally, the hydraulic characteristics of shell debris in water-intake open channel are studied first, and the source of shell debris in the drum filter at the water intake pump room is analyzed. Secondly, the water intake layout project scheme is optimized through the wave model test, which can effectively improve the wave cover in the water intake channel. At last, through the wave physical model test, the overall force of the network is studied under the combined action of wind, wave, flow and sewage, and the anchoring foundation which can guarantee the stable operation of the trash-intercepting network is optimized. By carrying out the optimization design of water intake engineering, reducing the waves in channel, reducing the possibility of marine sewage and organisms entering the channel, adding the trash-intercepting network facilities and forming effective cover. It can not only effectively avoid or reduce the impact of marine sewage and organisms on the cooling water source safety of NPPs, but also minimize the loss of marine organisms during the operation of NPPs.
Experimental Investigation of the Transient Pool Boiling Heat Transfer on the Quenching of Vertical Rodlet in Water
Authors: Wang Zefeng , Deng Jian , Qian Libo , Cai Rong , Xiong Jinbiao , Zhong Lei , Ma Yugao 
Published: October 2020

Abstract
Quenching is an important phenomenon in the evaluation of an emergency core cooling system following a hypothetical loss of coolant accident (LOCA) in a nuclear reactor. In the present study, an experimental apparatus is designed and constructed with the purpose of conducting high-temperature transient pool boiling quenching experiments for zirconium (Zr-4) cylindrical test samples. Three thermocouples are inserted in the test sample to investigate the effect of axial distance on the minimum film boiling temperature. The Zr-4 rodlet is heated up to a temperature well above the minimum film boiling temperature (up to 600°C), and then plunged vertically in a quiescent pool of subcooled water. A data acquisition system is used to record the temperature of the embedded thermocouples with time. Data reduction is performed by an inverse heat conduction code to calculate the surface temperature and corresponding surface heat flux. A visualization study with a high-speed camera is conducted to record the quenching behavior on the test sample. It is found that the minimum film boiling temperature decreases with the axial distance, while the CHF temperature is relatively insensitive to the axial distance. The film boiling heat transfer coefficient decreases with surface temperature, and seems to be independent of axial distance. The quench front is observed to originate from the bottom and move upwards. It is found that the quench front velocity remains nearly constant in the lower region of the test sample, and significantly increases in the upper region.
Feasibility Study of a New Fabrication Method for the Li4SiO4 Pebbles
Authors: Lo Frano R. , Puccini M. , Stefanelli E. 
Published: October 2020

Abstract
The production of reliable, stable, and durable breeder blanket material is one of the most important open challenge of fusion reactor technology.
A new low temperature fabrication method for producing lithium orthosilicate (Li4SiO4) pebbles based on the drip casting was developed at DICI - University of Pisa.
The pebbles were produced starting from a suspension of Li4SiO4 precursors prepared by sol-gel method, which was dripped through the experimental device and coagulated into solid spheres in a saline solution. Li4SiO4 pebbles were finally obtained after sintering at high temperature.
The pebbles produced are stable and well-sized (about 1.5 mm diameter). Pebbles have been analyzed in order to determine their physical and mechanical characterization. To the aim, SEM and X-ray diffractometer analyses were performed as well as compression tests by Instron machine. The pebbles obtained from the drip casting have a mechanical strength (about 11 N) comparable with that of the others solid breeder in pebbles form. In addition, if compared to these latter they have same roundness and sphericity.
Results confirmed the feasibility of drip casting forming technique, and provided further useful information for the optimization of the proposed new fabrication process.
Investigation of Turbulent Prt Model and the Segmentation Rule for LBE Turbulent Heat Transfer
Authors: Peiying Li , Jian Deng , Lei Zhong , Libo Qian , Rong Cai , Yugao Ma , Hongxing Yu 
Published: October 2020

Abstract
With liquid metal like lead-bismuth alloy (LBE) acting as a coolant for nuclear reactors, it is necessary to use a more accurate heat transfer relationship and a more reliable Prt model for the low Pr fluid. Because of the low Pr of liquid metal, the thermal conductivity is more dominant than the momentum transfer, which is quite different from ordinary fluids. In this case, the turbulent Prt can better reflect the heat transfer process. In this study, the Prt = A1+A2/Pr form is selected, and the corresponding coefficients are obtained by the renormalization group analysis method, then corrected by Pr. Furthermore, the applicable range and segmentation rule of the turbulent Prt model are discussed, and the obtained Prt segmentation theoretical model is written into CFD. The result shows that, compared with the previously unmodified model, the radial temperature distribution and Nusselt number (Nu) of the annular and bundle channel obtained by RANS method with the improved Prt model is in good agreement with experimental results, and the deviations are within 5%. It is proved that the turbulent Prt segmentation theoretical model proposed in this study is effective and can represent the heat transfer characteristics of liquid metal from the mechanism.
Development of a Multiphase Particle Method for Melt-Jet Breakup Behavior of Molten Core in Severe Accident
Authors: Wang Zidi , Iwasawa Yuzuru , Sugiyama Tomoyuki 
Published: October 2020

Abstract
In a hypothetical severe accident in a light water reactor (LWR) nuclear power plant, there is a possibility that molten core released from the reactor vessel gets in contact with water in the containment vessel. In this so-called fuel-coolant interactions (FCIs) process, the melt jet will breakup into fragments, which is one of the important factors for a steam explosion, as a potential threat to the integrity of the containment vessel. The particle method could directly and easily capture the large deformed interfaces by particle motions, benefiting from its Lagrangian description and meshless framework. In order to investigate the melt-jet breakup with solidification processes, a multiphase particle method with arbitrary high order scheme is presented in this study. In addition, an interfacial particle shifting scheme is developed to suppress the unnatural particle penetration between different phases. The convergence rate with different order is firstly confirmed by a verification test in terms of both explicit and implicit calculations. Then, a transient heat conduction between two materials is carried out and quite good results are obtained. After that, a rising bubble benchmark is performed to show the feasibility of modelling for deformation and collapse. Improvements of clear interface are indicated compared with previous reported results. Two important multiphase instabilities, namely the Rayleigh-Taylor instability and the Kelvin-Helmholtz instability, are studied since they play important roles during the melt-jet breakup. The results achieved so far indicate that the developed particle method is capable to analyze the melt-jet breakup with heat transfer.
Effects of Pre-Crack Depth and Hydrogen Absorption on the Failure Strain of Zircaloy-4 Cladding Tubes Under Biaxial Strain Conditions
Authors: Li Feng , Mihara Takeshi , Udagawa Yutaka , Amaya Masaki 
Published: October 2020

Abstract
Fuel cladding may be subjected to biaxial tensile stress in axial and hoop directions during pellet-cladding mechanical interaction (PCMI) of a reactivity-initiated accident (RIA). Incipient crack in the hydride rim assisted by the scattered hydrides in the metal phase may lead to failure of the cladding at small hoop strain level during PCMI. To get insight of such phenomenon, biaxial-EDC tests under axial to hoop strain ratios ranging from 0 to 1 were performed with pre-cracked (outer surface) and uniformly hydrided Zircaloy-4 cladding tube samples with final heat-treatment status of cold worked (CW), stress relieved (SR) and Recrystallized (RX). Results showed dependencies of failure hoop strain on pre-crack depth, strain ratio, hydrogen content and final heat-treatment status on fabrication, but no apparent dependencies were observed on the distribution pattern of hydrides (with similar hydrogen contents and hydrides predominantly precipitated in hoop direction) and the heat-treatment process for hydrogen charging. J integral at failure seems to be available to unify the effect of pre-crack depth.
Investigation of Hardening Law on Welding Residual Stress Analysis for Nickel Based Alloy 82 Weld Metal
Authors: Ejiri Mitsuru , Kubota Teppei , Soga Yukihiro , Nishihara Nozomi , Yanagida Nobuyoshi , Katou Hiroomi , Arashiba Tomoyuki , Taniura Wataru 
Published: October 2020

Abstract
There are three types of hardening laws for evaluating welding residual stress with the finite element method (FEM): kinematic hardening law, isotropic hardening law, and combined hardening law that combine these.
The purpose of this paper is to investigate which hardening law is more appropriate for the evaluation of welding residual stress of alloy 82. We first performed two types of welding tests: welding both ends of a plate, and welding the periphery of a disc. We then compared the results of mock-up welding tests with the analysis results of welding residual stress with the kinematic hardening law and combined hardening law.
Both the kinematic hardening law and the combined hardening law showed a welding residual stress distribution close to the results of the mock-up welding tests, but the combined hardening law tended to be closer to the mock-up results. Therefore when it is necessary to confirm the welding residual stress of alloy 82, it is considered appropriate to apply the combined hardening law.
Study on Cooling Process in a Reactor Vessel of Sodium-Cooled Fast Reactor Under Severe Accident: Velocity Measurement Experiments Simulating Operation of Decay Heat Removal Systems
Authors: Tsuji Mitsuyo , Aizawa Kosuke , Kobayashi Jun , Kurihara Akikazu , Miyake Yasuhiro 
Published: October 2020

Abstract
In Sodium-cooled Fast Reactors (SFRs), it is important to optimize the design and operate decay heat removal systems for safety enhancement against severe accidents which could lead to core melting. It is necessary to remove the decay heat from the molten fuel which relocated in the reactor vessel after the severe accident. Thus, the water experiments using a 1/10 scale experimental apparatus (PHEASANT) simulating the reactor vessel of SFR were conducted to investigate the natural circulation phenomena in a reactor vessel. In this paper, the natural circulation flow field in the reactor vessel was measured by the Particle Image Velocimetry (PIV) method. The PIV measurement was carried out under the operation of the dipped-type direct heat exchanger (DHX) installed in the upper plenum when 20% of the core fuel fell to the lower plenum and accumulated on the core catcher. From the results of PIV measurement, it was quantitatively confirmed that the upward flow occurred at the center region of the lower and the upper plenums. In addition, the downward flows were confirmed near the reactor vessel wall in the upper plenum and through outermost layer of the simulated core in the lower plenum. Moreover, the relationship between the temperature field and the velocity field was investigated in order to understand the natural circulation phenomenon in the reactor vessel. From the above results, it was confirmed that the natural circulation cooling path was established under the dipped-type DHX operation.
Numerical Simulation of Multi-Physics Processes in Nuclear System Based on Galerkin Finite Element Method
Authors: Yuan Baoxin , Yang Wankui , Zhang Songbao , Zhong Bin , Wei Junxia , Ying Yangjun 
Published: October 2020

Abstract
It is of practical significance to analyze the multi-physics process of nuclear system, which includes neutronics, heat transfer and thermoelasticity. Fission reaction is the heat source in system, the heat source will affect the distribution of temperature field, which will lead to the change of strain. Strain in turn will affect the distribution of neutron field. Therefore, it is necessary to analyze the distribution of neutron flux, temperature and strain in system. Three aspects of work have been carried out: 1) Based on Galerkin finite element theory, the governing equations of neutronics, heat transfer and thermoelasticity are established; 2) The multi-physics analysis code is developed; 3) The calculation results are analyzed and discussed.
Numerical Study of Fuel Melting and Molten Migration Based on the MPS Method
Authors: Lei Zhong , Deng Jian , Li Wei , Wu Xiaoli , Deng Chunrui 
Published: October 2020

Abstract
Core melting and molten migration behavior are hot and difficult issues in the field of nuclear reactor severe accident research. The Moving Particle Semi-implicit (MPS) meshless method has potential to simulate free-surface and multiphase flows. In this study, the MPS method was utilized to simulate the melting process of UO2-Zr rod-type fuel elements. The models of heat conduction with phase change, simplified UO2-Zr eutectic reaction, viscous flow and surface tension were implemented with the framework of standard MPS method. Then, the improved MPS code was used to simulate and analyze the process of high-temperature melting and characteristics of molten migration and solidification in the coolant channel, aiming at revealing the severe accidents for light water reactors (LWR), particularly the early core damage. The results showed that compared with the case of higher initial temperature, when the initial temperature of molten UO2 is lower, more molten UO2 will solidify on the surface of rod cluster, and the blockage of upper flow channel caused by molten UO2 is more serious. In addition, this study also demonstrated the potential of the MPS method for the study of complicated severe accident phenomena in not only traditional LWR but also advanced nuclear reactors in the future.