bluuebunny/crossref_metadata_2025_split huggingface dataset:
Validation of RELAP5/MOD3.4 for Flashing-Induced Instabilities in a Natural Circulation Loop
Authors: Xu Yifan , Peng Minjun , Xia Genglei , Zhao Yanan 
Published: October 2020

Abstract
This paper aims to validate the effectiveness of the widely used Relap5 code in simulating two-phase natural circulation, and its capability to predict flashing-induced instabilities. The RELAP5 code is validated against experimental data from the NMR test facility, which was designed to investigate the flow instability for a BWR-type novel modular reactor (NMR). The simulations by RELAP5/MOD3.4 code had been performed under various conditions by changing system pressure, core inlet subcooling, core inlet flow resistance, and core heat power etc. The flow stability for a certain operating condition could be determined from the time trace profile of the loop natural circulation flow rate. The results showed that the simulated mass flow rate increased with increasing core inlet temperature, reproducing the experimental trend. And the maximum error between the experimental data and the calculated results is within 10%. The predicted natural circulation dimensionless numbers, the phase change number and inlet subcooling number, also had a good agreement with the experimental data. In general, the RELAP5 code is able to simulate flashing-induced instability and density wave oscillations, which occurred in the natural circulation test facility at low pressures. However, flashing tends to be suppressed at a higher pressure (400kPa). And the enlargement of core inlet resistance coefficient can also have a positive impact on natural circulation system stability.
Experimental Study on the Sub-Channel Void Fraction Characteristics of Bubbly Flow in Rod Bundles
Authors: Ren Quan-yao , Pu Zeng-ping , Zheng Mei-yin , Su Min , Chen Ping , Pan Liang-ming , He Hui , He Qing-che 
Published: October 2020

Abstract
The gas-liquid two-phase flow behaviors are always associated with its dynamic void fraction, such as flow resistance, heat transfer coefficient, phase distribution, critical heat flux etc. As regard to the commercial PWR and BWR, rod bundles are the typical geometry, which contains many sub-channels for coolant flowing. In present study, the sub-channel void fraction was measured in 5 × 5 rod bundles with the sub-channel impedance void meter consisting of 12 strip electrodes. Based on the measured void fraction in different sub-channels, the void fraction dynamics, PDF (probability distribution function) and CDF (cumulative distribution function) curves were analyzed to make clear the effect of superficial gas and liquid velocity, flow development and casing tube. The empirical correlation for PDF of dynamic sub-channel void fraction has been developed, which showed good fitness with PDF and CDF curves and satisfying accuracy of averaged void fraction.
Artificial Neural Networks in Condition Monitoring and Fault Diagnosis of Nuclear Power Plants: A Concise Review
Authors: Jiang B. T. , Zhou J. , Huang X. B. 
Published: October 2020

Abstract
Artificial neural networks (ANNs) are recognized for their good properties in solving the non-linear classification problem. Especially, ANNs and their latest advancements in deep learning (DL) are blooming in artificial intelligence (AI) fields in the past few years. They have recently proven their abilities to handle some complex fault diagnosis problems. In the context of these backgrounds, this paper provides a concise review on the applications of ANNs to condition monitoring and fault diagnosis (CMFD) of nuclear power plants (NPPs). Firstly, a brief description of basic principle of ANNs are given. Then, a number of studies reported in both the journals and conferences are reviewed. These studies are divided into two categories according the application types of ANNs: shallow ANNs and deep ANNs. Finally, the conclusions and trends developed in the future are summarized.
Optimal Design for Helium Cooled Solid Breeder Blanket of CFETR
Authors: Nogueron Jose A. , Baorui Zhang , Zhiwei Zhou 
Published: October 2020

Abstract
On the road to achieving fusion energy production at a commercial level, China has proposed the design of a nuclear fusion reactor based on the tokamak configuration. Aimed to produce self-sustained burning plasma and a closed tritium breeding cycle, this device is expected to provide a bridge between ITER and DEMO designs.
The Breeding Blanket (BB) is one of the key technological challenges to be designed in order to guarantee sufficient tritium production, heat removal capabilities and radiation shielding protection. Two preliminary designs of the Helium-Cooled Solid Breeder (HCSB) blanket have been suggested to be subjected to further investigation. Despite the fact that both designs use the same materials, they present completely different geometrical arrangements. In the present analysis, these two concepts of the HCSB are examined, addressing the critical design issues that affect the performance of the system. A neutronic analysis is performed to calculate the Tritium Breeding Ratio (TBR), which is a crucial parameter to meet tritium production requirements. Based on this investigation, the cooling capacity of the reactor is analyzed with the help of a Computational Fluid Dynamic (CFD) software through a dynamic evaluation. Valuable conclusions can be extracted from the results of this work, which can be referenced for investigations regarding further studies of HCSB blankets.
Study on Rotor’s Vibration Characteristics of Helium Circulator of HTR
Authors: Li Jiahao 
Published: October 2020

Abstract
The helium circulator is used in the 10MW High Temperature Gas-cooled Reactor (HTR-10). The circulator operates at helium condition in order to transport the core heat to the steam generator. Rotor is a key component of the helium circulator. The rotor vibrates during the operation of the helium circulator. The study of the vibration characteristics of the rotor can provide important design parameters for the helium circulator. The effect of the shell on the rotor in the helium circulator is ignored in the usual research and analysis. In this paper, the working process of the rotor considering the shell effect was studied by theoretical analysis, and the vibration characteristics of the rotor considering the shell effect with various types and parameters was studied by finite element method (FEM). More accurate ranges of the rotor parameters which ensure the helium circulator to operate normally were determined. The shell increases the degree of freedom (DOF) of the rotor, which makes the analysis of the motion process of the rotor more complicated.
The results show that the different parameters of the shell on the rotor play an important role in the analysis results of the vibration characteristics. The analysis results considering the shell effect of the rotor are more accurate than the usual analysis results.
Neutronic Study on Conceptual Lithium Fluoride Salt Cooled Fusion Driven System for Actinide Transmutation
Authors: Putra Feryantama 
Published: October 2020

Abstract
The subcritical fission system could be used to transmute actinide elements from spent fuel into thermal power. Since the subcritical system needs an external neutron source, the D-T Fusion reactor was introduced as a fast neutron source to drive the chain reaction. Fusion driven system based on Spherical tokamak with a 1.7 m major radius has been designed. The breeding blanket has been modified to accommodate space for a 4.8 m length oxide fuel rod. Oxide fuel rods were immersed inside the lithium fluoride salt blanket, which acts as a coolant and liquid tritium breeder. The fully liquid blanket design was taken to reduce structure complexity and maximize tritium breeding volume. The neutronic study has been performed to calculate the neutron multiplication factor, actinide burnup in 400 days cycle and theoretical Tritium Breeding Ratio using MCNPX code. The design goal of fusion driven system with a fully liquid blanket is to reach keff value from 0.8 to 0.9 by burning sufficient actinide while breeding Tritium in Fluoride salt coolant. Various lithium fluoride coolant and reflector options have been simulated with the designed geometry. FLiNaBe salt liquid blanket was used as a reference since it could reach a keff value of 0.942 and able to transmute the actinide element in oxide fuel.
Experimental Study of Bubble Behaviour in a Flowing Liquid Layer
Authors: Zhang Zhengzheng , Li Liangxing , Zhang Shuanglei , Saleem Afnan 
Published: October 2020

Abstract
A visualized experimental system is designed and constructed to investigate the bubble dynamic in a flowing liquid layer. Motivated by reducing uncertainties and digging a deep understand on the formation mechanism of boiling bubbles, the bubbles are formed by injecting air through a submerged orifice in our present work, where the influence of thermal physics, nucleation site density and dry spot are stripped. The water flow rate and the air flow rate are in the range of 72–324 ml/min and 0.8–2.0 ml/min, respectively. The bubble formation process in the smooth channel and the rib channel are investigated. The results state that increasing the liquid flow rates lead to the increasing bubble detachment frequency and the decreasing bubble detachment volume. Besides, the larger the liquid flow rate is, the closer the bubble center of mass is to the wall. The rib has a significant influence on the bubble formation process. In the rib channel, it is more difficult for bubbles to detach from the orifice compared that in a smooth channel. Besides, the bubble detachment volume in a rib channel is larger than it in a smooth channel.
Evaluations of TiO2 Deposition on Structure Surfaces and Water Radiolysis for the Corrosive Environment in a Reactor Pressure Vessel
Authors: Mawatari Takashi , Yamamoto Yasushi , Shibasaki Osamu , Hara Takahiro , Horayama Yusuke , Takagi Junichi 
Published: October 2020

Abstract
It is important to avoid a risk of stress corrosion cracking (SCC) of structure materials in nuclear power plants. One of the methods for preventing SCC is titanium-dioxide (TiO2) injection. TiO2 is a photo-catalyst, and injected TiO2 deposits on the surfaces of structure materials, and the deposited TiO2 can decrease the electrochemical corrosion potential (ECP) by irradiation of Cherenkov-light in the reactor. Generally, the ECP is an important indicator about susceptibility to SCC, and ECP-lowering makes a risk of SCC lower. Therefore, initiation and propagation of SCC will be mitigated by the TiO2 injection.
The evaluation model for corrosive environment had been already developed. That “conventional” model was consisted of some analysis such as water radiolysis, ECP and others. However, the model did not consider an effect of TiO2 deposition and was one-dimensional simple model. Therefore, to evaluate ECP distribution in a reactor after TiO2 injection, the “newly developed” model was build: analyses integration, high-resolution and three-dimensional model.
In this paper, the TiO2 deposition and water radiolysis analyses integrated into flow analysis were contained. Both the deposition and the radiolysis depend on flow in the RPV, so that these analyses were built into the computational fluid dynamics (CFD) analysis model for CFD code. The target plant type for the model was 1100 MWe-class BWR-5.
The flow analysis was carried out at steady-state, assuming the TiO2 injection during the rated operation of the plant. Then the TiO2 deposition and the radiolysis analyses were conducted by transient calculations using the result of flow, and the three-dimensional and high resolution results were obtained.
Control Rod Blades Size Reduction Using Underwater Plasma Cutting and its Effects on Boron Carbide Powder Scattering
Authors: Serbouti Yassine , Kurihara Keisuke , Kometani Yutaka , Itagaki Masatoshi , Tatemura Makoto 
Published: October 2020

Abstract
Control rod blades are comprised of a stainless steel sheath, which contains neutron absorber tubes (filled with boron carbide powder). During decommissioning, the first stage of size reduction consists of cutting the connector (bottom portion) of the control rod, while the second stage consists of separating the blades of the control rod by cutting through the tie rod. The last stage consists of segmenting the control rod blades by cutting through absorber tubes.
In this study, the control rod blades segmentation (last stage of size reduction) is investigated using an actual control rod (unused). During the experiments, we used a forming press on the cut locations followed by a plasma arc cutting underwater. The purpose of this cutting technique is to minimize the scattering of boron carbides into water by using the stainless sheath melt to seal the absorber tubes.
After the segmentation, we confirmed the sealing of the absorber tubes by visually examining the cut cross-sections. The water analysis showed that the boron carbide scattering was relatively low (only 0.07% of the total boron carbides was scattered). Finally, we confirmed that the off-gas emission is considerably reduced by using Argon plasma instead of Argon-Hydrogen plasma.
Measurement of Thermal Decomposition Temperature and Rate of Sodium Hydride
Authors: Kawaguchi Munemichi 
Published: October 2020

Abstract
In decommissioning sodium-cooled fast reactors, the operators can be exposed to radiation during dismantling of cold trap equipment (C/T). The C/T is higher dose equipment because the C/T trapped tritium of fission products during the operation to purify the sodium coolant. In this study, thermal decomposition temperature and rate of sodium hydride (NaH) were measured as a fundamental research for development of “thermolysis” process prior to the dismantling.
We measured the thermal decomposition temperature and rate using NaH powder (95.3%, Sigma-Aldrich) in alumina pan with ThermoGravimetry-Differential Thermal Analysis (TG-DTA) instrument (STA2500 Regulus, NETZSCH Japan). The heating rates of TG-DTA were set to β = 2.0, 5.0, 10.0 and 20.0 K/min. The DTA showed endothermic reaction and the TG showed two-steps mass-loss over 580K. This first-step mass-loss was consistent with change of chemical composition of the NaH with heating (NaH → Na+1/2H2). The thermal decomposition temperature and rate were obtained from the onset temperature of the mass-loss and the simplified Kissinger plots, respectively. Furthermore, we set to the thermal decomposition temperature of around 590K, and the mass-loss rates were measured. As a result, over 590K, the thermal decomposition occurred actively, and showed good agreement with the estimation curves obtained by the simplified Kissinger plots. The thermal decomposition rate strongly depended on the heating temperature.
High Resolution 3D Simulation of Melt Jet Breakup Phenomenon Using Multi-GPU-Based Smoothed Particle Hydrodynamics Code and Comparison With Experimental Result
Authors: Park So-Hyun , Jo Young Beom , Kim Eung Soo 
Published: October 2020

Abstract
Fuel Coolant Interaction (FCI), one of the critical phenomena in severe accident, involves a variety of physical phenomena including the interaction between coolant and fuel of high temperature. Especially, the jet break-up of a pre-mixing phase that the bulk of molten fuel breaks into the droplet is important for the accident progression. Understanding the intricate physics of jet break-up is essential to reduce the uncertainties of FCI and to mitigate severe accident. In this study, we have developed Lagrangian-based CFD code (named as SOPHIA) using Smoothed Particle Hydrodynamics (SPH) method, which has an advantage on handling the complicated interfacial behaviors, large deformation and multiphase flow. Furthermore, the SOPHIA code is parallelized on the multi-GPUs to achieve high-resolution and large-scale simulation that enhance the accuracy and practical applicability. Using the multi-GPU based SOPHIA code, this study simulates the benchmark jet breakup experiments in high resolution and three dimensions. The simulation results are compared with the experimental data both qualitatively and quantitatively. As a results, they shows a good agreement, and furthermore, three dimensional high resolution simulation is confirmed to resolve the physical features of jet breakup accurately by taking account into the multi-fluids interactions between jet-pool-air.
Influence of Gas Properties on Gas-Liquid Two-Phase Flow
Authors: Saito Miki , Kanai Taizo , Nishimura Satoshi , Nishi Yoshihisa 
Published: October 2020

Abstract
Understanding the mechanism of fission product (FP) removal by pool scrubbing is essential for improving the prediction accuracy of FP emissions concerning severe accident (SA) in a nuclear power plant. Since FP migrates from a gas-phase to a liquid-phase via a gas-liquid interface, the FP removal efficiency by pool scrubbing is largely affected by the flow regime of gas-liquid two-phase flow. In order to gain a deeper understanding of the influence of gas properties on flow regimes, experiments were performed by injecting helium (He) and nitrogen (N2) gas mixtures of several volumetric ratios through a pool of stagnant water. The result suggests clear effects of gas compositions on gas-liquid two-phase flow, where both void and holdup fractions were found to increase with N2 fraction in the supplied gas. The results were compared with previous studies, and a detailed analysis of bubble characteristics for different compositions of gases was performed using a wire-mesh sensor (WMS). This paper also illustrates further research aspects needed to discuss the effect of its results on FP removal efficiency in a SA, and to acquire comprehensive physics behind such gas property influences on two-phase flow.
Localization of Radiation Sources Using Randomly Distributed Detectors
Authors: Li Ke , Liang Manchun , Yang Jie , Yang Dandan , Shen Hongmin , He Shuijun , Liu Fang 
Published: October 2020

Abstract
With the radiation sources widely used in the field of industry, agriculture, medicine, and resources all over the world, the occurrences of the lost and theft incidents are not unusual. There will be great threats to human health and environment for uncontrolled sources. It can be even worse when they are used by terrorists as weapons in the city, such as RDD, which would disperse the radioactive substances into the environment and have a long-term negative impact on human society. Besides the security control and surveillance of radiation sources, the source-searching method using radiation detectors is also needed to find the lost or stolen sources. In the case of radiation monitoring in a city, a mass of people with detectors are needed to cover the large area, while radiation dosimeters are appropriate for its portability and economy.
In this paper, a simple approach to finding and locating unknown radiation sources, which might be in static or mobile condition, using distributed mobile radiation dosimeters is put forward. This approach is able to estimate the time-dependent sources location and the intensity with the dose rate measurements over time periods.
Random data is introduced to verify the approach. Virtual radiation sources and detectors with random movement are created in the cases and the dose rate measurements are computed accordingly, with which sources location and intensity are estimated, where natural background radiation and the statistical fluctuation of measurements are taken into account. The results of the estimated sources show a good consistency with the assumptions.
Analysis of Transient Corium Pool Structure in the Lower Plenum of Reactor Vessel
Authors: Chen Liang , Pang Hua , Xie Ximing , Zhong Lei , Cai Rong 
Published: October 2020

Abstract
The transient stratification of the corium in the lower plenum and its impact on the heat flux distribution on the outside of reactor vessel is analyzed in this work. A method for predicting the kinetic corium pool structure is proposed, which takes into account both thermo-chemical equilibrium and density evaluation of the corium. The transient stratification of the corium pool formed after a large loss of coolant accident (LLOCA) and a station blackout (SBO) accident of ACP1000 nuclear power plant in China was analyzed by this method. The transient structure of the corium pool was calculated at the moment when the amount of molten materials in the corium pool increased obviously. The results shown that the formation of a three-layer pool is highly possible when a two-layer pool is formed in the previous moment with a heavy metal layer on the bottom and the density of the heavy metal layer at the bottom is greater than the density of the newly added molten material at the next moment. The heat flux on the outside of the vessel wall faced the thin top metal layer and the vessel failure probability of the vessel here are high if a three-layer pool occurred.
Reliability Assessment of NPP System for Risk Management Based on an Information Reasoning Methodology
Authors: Zhu Guixia , Zhou Tianmi , Qian Yugang , Liu Chongchong , Lu Hongxing 
Published: October 2020

Abstract
Risk management (RM) is an effective means of safety assessment and reliability management of nuclear power plant (NPP). During the operation of NPP, the main contents of RM work are as follows:
1. Real-time reliability assessment of NPP system, and evaluate NPP risk, so as to ensure that the NPP system can complete the specified functions to deal with the consequences of system failure.
2. Complete the diagnosis and mitigation of abnormal faults, so as to ensure that the NPP system can return to a safe state as soon as possible in the case of abnormal operation of NPP.
With the continuous improvement of the requirements of online RM, LPSA (Living PSA) technology, as an effective tool of RM, has been developed and provides more powerful support for the safe operation of NPP. In order to evaluate the reliability of NPP system in real time, LPSA model needs to be updated to match the state of the system. Most of the existing LPSA model updating techniques are based on the premise that the system information is completely knowable and the information is accurate. However, in the process of NPP operation, the accessibility of system information and the accuracy of information are difficult to meet the requirements of updating the existing LPSA model.
How to update the LPSA model in the case of incomplete and inaccurate information is one of the difficulties in the application of online LPSA technology. Especially when the NPP is in abnormal conditions, it is more urgent for operators to obtain correct system information in real time to recognize the available state of the plant system.
In fact, the required system information needs to be obtained by the operator through his or her cognitive behavior process, such as the fault diagnosis process. At the same time, this information can be used to help operators complete the diagnosis of system status and the evaluation of system reliability.
In this study, an information reasoning method is proposed to evaluate the probability of various failure modes under the information known to the operator through the modeling and analysis of the cognitive behavior process of the operator. The method can assist the operator to make the correct fault judgment to complete the fault diagnosis and fault mitigation. In addition, the information obtained by the operator in the process of cognitive behavior, and the results of information reasoning can be used to update the LPSA model in real time, so as to obtain the real-time reliability evaluation results of the NPP system.