bluuebunny/crossref_metadata_2025 huggingface dataset:
Neutronics comparative analysis of fuel assemblies using CSG and DAGMC methods
Authors: Sun NingYan , Liu ShiChang
Published: November 2022

The traditional Monte Carlo method uses the Constructed Solid Geometry (CSG) method to build up the geometry by creating surfaces and using Boolean operators. This method has obvious deficiencies for new type reactors with complex geometry and large size. This method has the problem of geometric overlap. Direct Acceleration Geometry Monte Carlo (DAGMC) method based on CAD geometry modeling can accurately describe higher-order surfaces, which can effectively overcomes the shortcomings of CSG modeling method and effectively build up the model. Additionally, CAD geometry has good visual effect. On the one hand, it is conducive to the verification of the correctness of the model. On the other hand, it is beneficial to the analysis of the calculation results DAG-RMC function based on Reactor Monte Carlo code RMC can directly use CAD model to carry out particle transport calculation. Based on CSG and DAGMC, this paper constructed three dimensional rod repeat structure fuel and plate type repeat structure fuel assemblies respectively and calculated keff as well as power distributions in order to verify the correctness of DAGMC in particle transport and critical calculation for complex geometry. Through comparisons, the keff and power distributions calculated by the two methods are in good agreement, verifying the correctness of DAG-RMC function.
The BDB-NS Hydrodynamic Model for Porous Spent Fuel Storage Racks Solved by Fourier Spectral Method
Authors: Liu Yu , Zhu Yuxuan , Zhao Fei , Liu Dong , Lu Daogang
Published: November 2022

Spent fuel storage racks (rack) are used to store highly radioactive spent fuel. Its seismic design is of great significance for radioactive containment. To reduce the transmission of seismic load, the fuel storage racks (racks) are in a free-standing design, whose bottoms are not fixed with the ground of the spent fuel pool wall. In an earthquake, the rack should not deform significantly to avoid the criticality of the fuel assembly during storage, and the water effect shall be considered. The porous rack design is widely used in the third generation PWR. Under seismic conditions, there is fluid penetration in the porous rack and flow around the outside. If the traditional fluid-structure coupling model of the closed structure is adopted, the analysis is too conservative, and the calculation method of transient CFD fluid-structure interaction parameters based on fine modeling is too time-consuming. To improve the calculation efficiency of fluid-structure interaction parameters of porous racks, a BDB-NS coupling model is established for the fluid immersed porous square cylinders. Combined with the Fourier Spectral Method and solved by MATLAB, the fluid force of the porous racks are obtained, and the parameters such as added mass and added damping are obtained. The algorithm is validated by a solid square cylinder in an infinite water zone the CFD results. This paper can provide a basis for the selection of fluid-structure interaction parameters of spent fuel storage racks for CAP1400 and HPR1000.
The Development and Application of Real-Time Risk Monitor System Based on Level 2 PSA for NPP
Authors: Li Wenjing , Liu Yu , Wei Wei , Yu Xinli
Published: November 2022

The method of real-time risk monitor system (RM) development based on Level 2 probability safety analysis (PSA) is established and a real-time risk model for a nuclear power plant (NPP) in China is developed in this paper. The risk monitor system can calculate not only the core damage frequency (CDF) but also the large early release frequency (LERF) with different plant configurations. In this paper, the application of risk monitor system will be discussed in two aspects: Configuration risk management and risk-informed technical specification (TS) optimization. Configuration risk management method based on risk monitor system is studied and case analysis is carried out for the NPP, which will improve the plant risk management ability and safety. Risk-informed technical specification optimization approach based on RM is studied and case analysis is performed for the TS, which can prolong the completion time for a single equipment/system failure in TS to improve the operation economy of NPP. In addition, the evaluation of completion time for multiple equipment failures is the supplement to the traditional TS. The Level 2 PSA risk monitor system development is a good engineering practice of Level 2 PSA in NPP, and is of great significance for improving both the safety and economy of the plant.
Numerical Simulation Analysis of Silicon Carbide Whiskers Doped Uranium Dioxide Composite Fuel for High Thermal Conductivity
Authors: Lu Linyuan , Guo LiHua , Zhong Yajuan , Zhang Feng , Lin Jun
Published: November 2022

SiCw is expected to be candidate material for Accident Tolerant Fuel (ATF). Nevertheless, the distribution, morphology and size of SiCw have impacts on the thermal conductivity of composite fuels. An analysis model for UO2-SiCw was established using finite element method (FEM), and the effects of whisker orientation, size, volume fraction and aspect ratio on thermal conductivity were analyzed. The generation algorithm of SiCw was improved, and the results of thermal conductivity calculations showed that the improved model is closer to the experimental value. The effect of whisker orientation on thermal conductivity can be calculated by the cosine law of zenith angle and azimuth angle, and deriving a model for calculating thermal conductivity with specific whisker orientation. With the decrease of whisker size, the influence of Kapitza thermal resistance is significant. The formula used to calculate the whisker threshold diameter was deduced, and the results are in good agreement with the FEM results. With the increase of volume fraction of whiskers, the thermal conductivity increases linearly. For morphology, whiskers with high aspect ratio can achieve higher thermal conductivity. There is a value for the ratio of whisker length to matrix size, above which increasing whisker length will slow the increase in thermal conductivity (0.3 for whiskers along the direction of thermal conduction). The thermal conductivity of UO2-SiCw was optimized using the above conclusions, and the radial temperature distribution of pellet was analyzed. The results show that taking full advantage of the anisotropy of whisker heat transfer can significantly improve the thermal conductivity of composites and improve the operation condition of the pellet. The results can provide a good theoretical basis for designing whisker-doped composites with high thermal conductivity.
Hydrogen Release Reaction From Sodium Hydride With Different Sample Quantities
Authors: Doi Daisuke
Published: November 2022

In sodium-cooled fast reactors (SFRs), hydrogen is a major nonmetallic impurity in the coolant during normal operation. A higher hydrogen concentration than the gas-liquid equilibrium had been transiently detected in the gas space of the actual SFR plant. However, the chemical reactions that caused hydrogen generation, which involve several sodium compounds, have not been identified. Furthermore, the thermal behavior of these hydrogen release reactions has not been thoroughly investigated. In this study, the hydrogen release behavior of sodium hydride, which could be involved in all of these reactions, was clarified by two experimental methods dealing with different sample quantities. In the thermal analysis with a semi-micro sample of about 1mmol, the hydrogen generation was demonstrated by mass spectrometry as the sample mass decreased, suggesting thermal decomposition. A monomodal hydrogen release curve similar to the thermal analysis result was obtained in the heating experiment with a macro amount sample of about 1mol. These experimental results showed consistent activation energies within the standard error. Therefore, it was elucidated that the ideal reaction behavior obtained by thermal analysis could be sufficiently extrapolated to the reaction behavior occurring in a larger amount of sample. These findings provide fundamental insights into the thermal decomposition of sodium hydride and are indispensable for analyzing hydrogen release behavior in other hydrogen release reactions involving sodium hydride.
Determination of Radiation Shielding Properties of Low-Density Polyethylene Reinforced With Bismuth Against Gamma-Rays
Authors: Abd Rahman Nur Shafriena Farhana , Sazali Muhammad Arif , Ripin Azuhar , Mohd Ali Nur Syazwani , Sarkawi Muhammad Syahir , Jamaluddin Khairulnadzmi
Published: November 2022

Radiation hazard has inevitably become a global threat due to the widespread use of radiation technology in industrial manufacturing and medicine. As in medicine, the workers are in danger of being exposed to high-penetrating gamma-rays during the treatment of cancerous tumours. Hence, developing such an excellent shielding material from the polymer is vital since it can be used broadly, is low cost, and is non-poisonous to nature. This study aimed to observe the effect of additive content such as bismuth on shielding performance. To test the hypothesis that high-density material leads to higher radiation shielding performance, fabricated bismuth-low-density polyethylene (LDPE) composites that have been processed via internal melt-mixing and compression-moulding processes were labelled with LDPE-100, Bi-5, and Bi-10 containing 0, 5, and 10 wt.% of bismuth content with a thickness of 0.1, 0.2, 0.3, and 0.4 cm respectively. Throughout the experiment, a photon from a gamma source of 241Am and 133Ba with an energy range of 59 keV and 356 keV were captured by a solid-state detector to calculate the count rate in count per second (cps). The fundamental shielding parameter such as mass attenuation coefficient, half-value thickness, tenth-value thickness, and mean free path was also computed using Phy-X software to evaluate the radiation shielding effectiveness. The results showed that Bi-10 polymer composites with 10% wt. of bismuth filler had MAC, HVL, TVL, and MFP values of 1.159 cm2/g, 0.554 cm, 1.838 cm, and 0.798 cm, respectively, and may be used as an effective shielding material for gamma radiation with an energy of 59 keV compared to 356 keV.
Research on Operation Life Extension Time Limited Aging Analysis Key Method for Electrical Penetration Assembly of Nuclear Power Plants
Authors: Wang Binfeng , Chen Zhilin , Huang Ping , Shi Zhenhao , Zhang Yanwei , Liu Tao
Published: November 2022

Environmental qualification (EQ) is a process to ensure that equipment will be capable of withstanding the ambient conditions and executing specific function that the equipment is actually called upon to be performed under accident conditions. The main purpose of EQ is to provide reasonable evidence to ensure that common cause failures will not occur. Electric penetration assemblies (EPAs) belong to EQ components and perform safety-related functions. The time limited aging analysis (TLAA) of EQ components includes all long-lived, passive and active electrical components and commodities located in a harsh environment that are important to safety. This paper takes the electric penetration assembly (EPA) of a early domestic M310 NPP as the research object, based on the components, materials, environment, aging mechanisms and effects of EPA, combined with domestic and foreign standards, specifications and latest research results of equipment qualification and operation license extension, the time limited aging analysis key method of EPA of a early domestic M310 NPP is studied, the test scheme is designed, the test sample is selected, the key parameters are determined, the supplementary environmental qualification of EPA of a early domestic M310 NPP is finished. At the same time, combined with the current management status of EQ equipment at home and abroad, some management suggestions are proposed to maintain the validity of the qualification status during the period of operation license extension.
Mechanical Vapor Re-Compression Evaporation Treatment of Radioactive Waste Water
Authors: Qiaofen Liu , Ming Huo , Fei Gao , Linjun Yang , Yong Liu
Published: November 2022

Evaporation method has been widely used in radioactivity wastewater treatment of nuclear power plants because of its high decontamination factor (DF) and wide application range of water quality. However, the traditional evaporation system has high energy consumption. Aiming at the recovery of latent heat of secondary steam during stable evaporation of wastewater in radioactivity, a new evaporation system & mechanical vapor recompression (MVR) was proposed and studied. Firstly, a mathematical model is established according to the conservation equations of mass and energy. The factors affecting energy consumption, decontamination factors, and secondary waste that needing attention due to radioactivity are discussed. According to the improved scheme, a prototype was built and the wastewater treatment experiment in simulated radioactive water was carried out. The actual energy saving rate and decontamination factor are calculated and analyzed. The results show that, at the conditions of evaporation rate of 600kg/h and evaporation temperature of 100°C, compared with traditional evaporation, MVR can save 84.8%energy, and the decontamination factor (DF) reaches 105 in simulated waste liquid treatment experiment. MVR shows that this method has obvious advantages in economic and environmental benefits.
A Detailed Model to Predict Mechanical Characteristics of Fuel Assembly
Authors: Zhao Jingjing , Xu Shiyin , Pan Wenan , Sun Jingya , Du Yuxi
Published: November 2022

As the core component and the first safety barrier of a nuclear power plant, the structural integrity of fuel assemblies (FAs) is an important factor in ensuring the safety of nuclear power. Safety analysis and evaluation of fuel assemblies under seismic conditions is a requirement of nuclear power plant design codes and safety reviews. The mechanical properties of a single FA determine the operational and seismic performance of the core fuel assembly. Due to the complexity of the FAs in terms of structure and boundary conditions, test is the most common method to obtain the mechanical properties. In order to predict the mechanical properties of the fuel assembly, a nonlinear finite element detailed model was developed. The contact and frictional behavior between the fuel rod cladding and the spring/dimple convexity were considered in the modeling to simulate the nonlinear behavior of the fuel rod better. To verify the validity of the model, virtual tests of lateral stiffness test, forced vibration test and impact test were conducted on the model. The comparison with the experimental results shows that the model can reflect the mechanical properties of the fuel assembly well. The modeling method and calculation conclusions in this paper are of guidance for fuel assembly design.
Access Time and Safety Benefit Analysis of Additional Temporary Water Injection Measures on Primary After the Fukushima
Authors: Liu Weidong , Wang Zhao , Liu LeiLei , Zhang Kuan
Published: November 2022

After the Fukushima nuclear accident, National Nuclear Safety Administration carried out plant inspection nuclear safety on the nuclear plant in operation and under construction, and put forward improvement requirements for each nuclear power plant according to the inspection results. One of the improvement actions was to add temporary water injection measures on the primary side. At present, all power plants have plant requested to add mobile pumps and related water supply pipelines and operating procedures. By summarizing the calculation cases of plant, which selected representative accident sequences for deterministic analysis in the past, this paper determines the effect of implementing temporary water injection measures in primary circuit on accident mitigation at different times, and the results can provide time suggestions for the preparation of mobile equipment in plant. At the same time, the safety benefits after implementing temporary water injection measures in primary circuit in plant are analyzed by using probability analysis method. Based on the analysis of deterministic and probability theory, and considering the preparation time of accessing mobile equipments, it is considered that 4 hours is a reasonable access time for mobile equipments under SBO accident conditions. In the actual access process, this time can ensure that operators have a more suitable time to complete the preparation work of mobile equipments in operation, and at the same time contribute to the reduction of large release frequency. At the same time, it should be noted that at present, the contribution of implementing temporary water injection measures on the primary side under SBO accident is mainly analyzed. In fact, some accident situations with slow development except SBO accident also have great access possibility, so the actual safety benefits of temporary water injection measures on the primary circuit may be more.
Design and Optimization of a PGNAA System Based on D-D Neutron Generator for Cement Composition Analysis
Authors: Chen Si-Yuan , Li Guang-Hao , Jia Shao-Lei , Lu Zhao-Hu , He De-Dong , Ke Gong , Shi Guang-Yu , Jing Shi-Wei
Published: November 2022

Online composition analysis is a crucial method for energy-saving and environment-friendly cement industry. A prompt gamma neutron activation analysis (PGNAA) system, which is aimed to determine the elemental concentrations of cement sample, has been designed and optimized by the Monte Carlo approach. This system consists of a 2 × 2” Bismuth Germanate (BGO) scintillation detector, a portable D-D neutron generator, a multi-channel analyzer, the reflector, the moderator and the shield. Out of consideration for minimization of costs and maximization of the thermal neutron flux at the output surface, different models of reflectors and moderators were tested in the MCNP code. Meanwhile, lead shield was also designed to reduce gamma-ray background produced by the nature and the system itself. In addition, simulated spectra of a standard cement sample were obtained to test the performance of this system. For ensuring the safety of the system operators, the dose rate distribution around the system were evaluated. The results demonstrated the feasibility of adopting this optimized design for chemical composition analysis of cement sample, and provided data reference for similar research. Eventually, an in-situ system has been established for further study.
Multiphysics Analysis of Fuel Performance and Tritium Migration in FeCrAl and Cr-Coated Zircalloy Cladding Under PWR Normal Operating and Transient Conditions
Authors: Liu Rong , Yang Liwen , Liu Shengyu
Published: November 2022

Due to the fact that the Cr-coated Zircalloy and the FeCrAl alloy have excellent high-temperature oxidation resistance, corrosion resistance, they are considered to be potential replacement materials for PWR cladding. However, it is also reported that the poor tritium resistance of FeCrAl alloy will accelerate the penetration of tritium throughout the cladding and increase the treatment cost. In this work, the physical models and tritium migration models of Cr-coated Zircalloy cladding and FeCrAl claddingare reviewed firstly. Then, based on the developed fuel performance analysis code CAMPUS, the fuel performance models of Cr-coated Zircalloy cladding and FeCrAl cladding are implemented, and a new model of the tritium migration in different claddings is implemented too. Finally, the performances of three fuel cladding combinations (UO2 pellets and Zircalloy cladding, Cr-coated Zircalloy cladding and FeCrAl cladding) under normal and LOCA conditions are simulated and discussed. And the tritium resistance performance of different fuel cladding combinations is further calculated and analyzed with the new tritium migration model. The calculation results show that under normal and LOCA conditions, compared with Zircalloy cladding, the application of FeCrAl cladding can reduce the overall temperature of fuel and improve fuel safety margin. And the application of Cr-coated Zircalloy cladding and FeCrAl cladding can effectively delay the failure time of cladding under LOCA condition; In terms of tritium penetration, the Cr-coated Zircalloy is found to have better tritium resistance effect than FeCrAl alloy, which greatly reduces the pollution treatment cost of reactor operation.
Quantitative Probabilistic Safety Analysis of Locking Mechanism of Nuclear Power Control System Products
Authors: Jiang Zhirui
Published: November 2022

Nuclear power control system products must be firmly fixed in the cabinet to ensure that the control system can work normally under earthquake and other working conditions. The locking mechanism of a nuclear power control products were analyzed by FTA, and the quantitative probabilistic safety analysis of the key failure mode locking mechanism loosening event was carried out. Firstly, the Finite element model of locking mechanism was established by using ANSYS, conduct a deterministic simulation analysis under seismic conditions. Then, based on the reliability theory, the failure mode interference equation was established according to the deformation of the locking hook of the locking mechanism, Monte Carlo reliability algorithm program and ANSYS joint simulation interface program were developed, for the failure of locking mechanism loosening, Monte Carlo sampling statistical joint simulation calculation was carried out by using the ANSYS joint simulation interface program, the probability of loosening failure event of locking mechanism under different confidence was calculated. This paper explores a new method for quantitative probabilistic safety analysis of locking mechanism, which has reference value for quantitative probabilistic safety analysis of similar mechanisms. The locking mechanism loosening event probability in the fault tree of probabilistic safety analysis was accurately calculated by using this method, through the introduction of reliability algorithm, it focuses on the evaluation core processing of uncertainty, which is an improvement of probabilistic safety analysis method.
Flow-Solid Coupling Analysis of Pressure Vessels on Floating Nuclear Power Plants
Authors: Wang Yuchao , Lu Daogang , Zhao Fei , Liu Yu
Published: November 2022

Lead-cooled fast reactors are an important choice for small-scaled reactor in floating nuclear power plants. Compared with land-based nuclear power plants, floating nuclear power plants have advantages in stability, which eliminate the impact from earthquake. One aspect remains to be solved is that the lead-cooled fast reactors contains a large volume of liquid that may slosh under the marine environment. The sloshing of liquid may cause external pressure on the nuclear reactor vessel and internal components., which has a great impact on the safety of the reactor. To study the fluid structure interaction between liquid and reactor vessel, this paper establishes an numerical model for the mechanical analysis of the main vessel of a floating nuclear power plant under loads of the marine environment. The mechanical response of the main vessel of a floating nuclear power plant in the marine environment is analyzed by applying the dynamic mesh method and VOF model. The motion of marine environmental loads are applied by the remote displacement method. We study several typical loadings in operation conditions. The study shows that the stress on reactor vessel caused by fluid sloshing is relatively small when long-period loading is applied; and the effect of swaying is larger than the rolling.
The Study of Coupled Fuel Performance Analysis and Neutronics With COMSOL and RMC
Authors: Liu Zhenhai , Qi Feipeng , Zhou Yi , Li Quan , Chen Ping , Chen Hao , Ma Chao , Zhao Bo , Li Chenxi
Published: November 2022

Predicting fuel behavior in the reactor is a typical multi-physics coupling problem. The traditional fuel performance analysis adopts a decoupling way. To provide a higher fidelity tool for fuel performance simulation, the multi-physics coupling software COMSOL and 3D Monte Carlo neutron transport code RMC are coupled. The fuel rod thermo-mechanical coupling analysis module is constructed in COMSOL. RMC is innovatively wrapped as a component of COMSOL to communicate with the fuel performance module. Grid mapping algorithm is set up using COMSOL’s functionality. A carefully designed segregation solver sequence is used to control the coupling process. The fine power distribution calculated by RMC is transferred to COMSOL fuel thermal calculation, and the fuel temperature and the coolant temperature and density calculated by COMSOL are transferred to RMC. In a Picard iterative way, the fuel rod lattice level neutron thermomechanical tight coupling is realized. The coupling is demonstrated in a fuel rod BOL steady state case. The fuel performance analysis is enhanced by the higher fidelity neutron flux solution.
Study on Steady Operational Characteristics of Floating Nuclear Reactor Under Ocean Condition
Authors: Cheng Kun , Chu Xiao , Qiu Zhifang , Xian Lin , Deng Jian
Published: November 2022

Different from land-based reactors, floating reactors are affected by the ocean condition. Numerical simulation is conducted to study the effects of heaving and rolling motion on typical floating nuclear reactor (FNR) under rated power operation by ARSAC code with ocean condition calculation module. The calculation results have shown that heaving motion can cause the periodic fluctuations in the flow rate of both the primary and secondary loops in FNR. The amplitude of heaving motion is the main influence factor on the flow rate fluctuation of the primary loop while the effect of heaving motion period is limited. Rolling motion can cause the out-phase flow fluctuation in the two symmetric loops of the primary system. However, the rolling motion has limited impact on the core flow rate and cannot cause dramatic changes of system parameters at the core. Within the range of motion parameters used in this paper, heaving and rolling motion cannot have a substantial impact on the safe operation of FNR under rated power operation.
Effects of Aggregation on Gravity Settlement of Submicron Aerosols Under High Temperature and High Humidity Conditions
Authors: Chen Jun Yan , Gao Pu Zhen , Gu Hai Feng , Yu Hui Yu
Published: November 2022

Coupling aerosol gravity sedimentation mechanism and aggregation effect, considering the correction of submicron particle free path and gas dynamic viscosity in thermal environment, a gravitational sedimentation model suitable for submicron aerosol accompanied by coalescence effect under high temperature and high humidity conditions is established, and the established model is verified by the results of thermal experiments. The aerosol aggregation model is established using the discretization method. By controlling whether the aggregation mechanism occurs in the established model, the influence of aggregation on gravitational settling when steam fraction and ambient pressure are changed is studied. In the study, it was found that the aggregation effect has a nearly 1-fold acceleration effect on the decay constant of the number concentration of submicron aerosols during gravitational sedimentation, and the acceleration effect on the decay constant of the mass concentration can be ignored, but there is an acceleration trend. When submicron aerosols settle under high temperature and high humidity conditions, the number median particle size tends to increase, that is, the increase of the number median particle size by the aggregation effect is greater than the decrease of the number median particle size by gravity sedimentation. After considering the aggregation effect, the number concentration decay constant and the mass concentration decay constant when the submicron aerosol undergoes gravitational sedimentation will decrease with the increase of the ambient pressure, and increase with the increase of the steam fraction. However, the number concentration decay constant changes larger, the mass concentration decay constant has a trend of change, and the change range is relatively weak. In addition, in the sensitivity analysis of the aerosol coalescence and gravitational sedimentation models, it is found that the molecular free path has a greater impact on the calculation results of aerosol coalescence and deposition in a thermal environment than the dynamic viscosity. Moreover, the influence of Brownian coalescence on the aerosol particle size spectrum is much greater than that caused by gravitational coalescence.
Development and Application of Modular Information Management System for Nuclear Power Engineering
Authors: Gong Xiaocheng , Xu Xinwei , Zhou Wei
Published: November 2022

Modular construction technology is one of the effective ways to shorten the construction period and reduce the cost of nuclear power plants. It is one of the important features of the development of nuclear power engineering construction technology. The application of the module in China has a history of more than 20 years, and it was first used in the construction technology of nuclear island workshop dome steel lining. As modularization is the technology of integrated design,procurement and construction,and is based on the three-dimensional design platform, the close cooperation among design, procurement and construction also needs the support of the corresponding information platform. It is more urgent and necessary for the unified, shared and rapid interface response processing of upstream, downstream and management information. Based on the actual needs of nuclear power project construction and relying on the modular three-dimensional model, this paper develops and constructs a three-dimensional visual modular comprehensive information management system integrating the business data of design, procurement, construction, commissioning and management, realizes the efficient coordination and fine management of modular advanced construction technology of nuclear power project, and provides an information management platform for modular construction of nuclear power project.
Study on the Added Mass of the Double-Fixed Constrained Flexible Coaxial Cylindrical Shells With Liquid in the Narrow Gap
Authors: Li Donghao , Lu Daogang , Zhu Yuxuan , Liu Yu
Published: November 2022

There are many coaxial cylindrical thin-wall structures with a narrow fluid gap in the reactor block of the pool type sodium cold fast reactor (such as primary pump support and its thermal shield). The fluid-structure interaction (usually represented by added mass) of shells and the fluid gap changes the structure’s dynamic characteristics under seismic conditions. Therefore, it is significant to calculate the added mass of the coaxial cylindrical shells. At present, there are few studies on the vibration modes and added mass of flexible shells with double-fixed constrain. For the flexible coaxial cylindrical shells model, due to the coupling of the inner and outer shell, the vibration modes of the inner and outer shell in the same and opposite directions are generated. In this paper, the added mass of two vibration modes in the same direction and in the opposite direction are investigated. The finite element models (with water and without water) of the coaxial cylindrical shells were established using ANSYS software, and the vibration modes and added mass were calculated by FEM. Further, the effect of different outer shell rigidity on the added mass of coaxial cylindrical shells was studied by changing the material parameters of the outer shell.
Fault Diagnosis Based on KPCA and RUSboost for Nuclear Power Plants
Authors: Wang Yiqing , Sun Peiwei
Published: November 2022

Nonlinear relationships among different process variables are very common in nuclear reactors. When constructing a nonlinear model to for process monitoring, linear-based monitoring technique has been proved inefficient and problematic. Kernel principle component analysis (KPCA) combines the principle component analysis and kernel method to cope with fault diagnose in nonlinear system. Experiments are conducted using data samples from Generic Pressurized Water Reactor Simulator(GPWR) to simulate sensor fault and three types system faults. The nonlinear relationship among monitoring variables is analyzed. KPCA is used to capture the nonlinear relationships to distinguish the sensor fault and system fault, which shows the superiority of KPCA to detect a univariate fault. Subsequently, system faults are further analyzed as a classification problem.

Samples imbalance is another common problem existing in diagnose domains. When training samples of one class outnumber than other class, traditional classification algorithm performance may deteriorate. Random under-sampling boosting (RUSboost), a hybrid sampling and boosting algorithm is used to alleviate the imbalance problem. The performances of classifiers by four metrics is evaluated. When compared to Adaboost (contains only boosting), tree variants (base model and ensemble bagged trees) and Gaussian SVM, RUS boosting shows significantly high accuracy and robust performance in dealing with different ratio of training samples, which shows that RUSboost is an excellent technique to cope with imbalanced data in fault diagnose for nuclear power plants.
Investigation on Irradiation Resistance of Anti-Galling Lubricant for High Temperature Fasteners of Nuclear Power Plant
Authors: Liu Xiao Qiang , Jiao Ming , Shi Xiu Qiang , Bao Yichen
Published: November 2022

Lubricant grease is a special material commonly used in the field of nuclear power plant. It is widely used in the sliding fit and press fit parts of bolts, studs and valves to prevent thread wear, seizing as well as stress corrosion cracking of fasteners during assembly, service and disassembly. In this paper, the performance of lubricant materials such as wear resistance and high temperature oxidation resistance under irradiation environment were studied. The results show that the lubricant grease does not change significantly and there is no grease stratification after irradiation with 0.1MGy integrated irradiation dose. However, after irradiation with 10MGy integrated irradiation dose, the irradiation has an obvious destructive effect on the oxidation resistance performance of the grease, and the grease appears obvious stratification. With the increase of irradiation dose, the thermal decomposition temperature first decreases and then increases. Under 0.1MGy irradiation dose, the thermal decomposition loss of the sample changes little, but at 10MGy irradiation dose, a large amount of mass loss occurred, up to more than 80%. The four-ball friction experiment shows that its extreme pressure resistance improves with the increase of irradiation dose, and the sintering load increases. These data provide technical guidance for the long-term reliability of nuclear power fastener materials in service.
Effect of Hydration Time on the Hydro-Mechanical Behavior of Compacted GMZ Bentonite With an Artificial Annular Gap
Authors: Luo Hewen , Ye Weimin , Wang Qiong , Xu Libo
Published: November 2022

According to the conceptual design of high-level radioactive waste (HLW) disposal repositories, the buffer barrier will be constructed by compacted bentonite blocks, which will inevitably produce technological gaps (voids) in the repository. During the consequent long-term operation of the repository, the technological gaps will be gradually filled up on hydration of the bentonite blocks with infiltration of underground water from the host rock. This hydration process will be accompanied by variations of the hydro-mechanical behavior of the buffer system. Therefore, it is necessary to study the changing process of the hydro-mechanical behavior of bentonite blocks with consideration of influences of the technological gaps. In the present work, a series of hydration tests were carried out on compacted GMZ bentonite specimens with initial annular gaps. During the hydration, variations of swelling pressure and hydraulic conductivity were measured. After each test, distributions of dry density and water content in the specimen were determined and the microstructure at different positions was investigated. Results show that, the swelling pressure of the specimen increased rapidly first and then decreased slightly during the hydration process, while the hydraulic conductivity kept decreasing with time. Moreover, closure of the technological gaps induced heterogeneity of the bentonite blocks, which was characterized by the decrease of dry density and the increase of water content with increasing distance to the center of the specimen. With the hydration time elapsed, the bentonite blocks could be divided into compression zone and swelling zone along the radius. In the compression zone, the dry density of the specimen gradually increased, with a decrease in the total pore void ratio and the macro-pores void ratio. In the swelling zone, the dry density decreased with an increase of the total pore void ratio and the undetectable pore void ratio.
A Transient Model of Sodium Heat Pipe With Phase Change Temperature Difference
Authors: Zhong Ruicheng , Ma Yugao , Zhao Qingzhu , Deng Jian , Liu Yu , Ding Shuhua
Published: November 2022

The heat pipe is the essential component in the heat pipe cooled reactor, it conducts heat through the phase change of the working medium and the circulating flow of gas and liquid. One end of the heat pipe is inserted into the reactor as the evaporation section, while the other end serves as the condensation section connecting to the thermoelectric conversion system. Its heat transfer capacity and temperature distribution under a steady state affect the safety, core temperature and energy conversion efficiency of the heat pipe cooled reactor system. Predicting the heat transfer process and steady-state temperature distribution of the heat pipe is helpful to learn about the heat transfer mechanism inside the heat pipe and key factors affecting its performance. It is also helpful to predict the operating characteristics of the heat pipe cooled reactor system and improve the performance of the heat pipe. The heat pipe is generally considered to be a heat transfer element with good isothermal properties. Past studies, however, proved the significant quantity of its phase-change thermal resistance, resulting in a temperature difference at the gas-liquid interface of the heat pipe that affects the evaporation and condensation. Studies on the relationship between the temperature difference, the working temperature, and heat transfer power of the heat pipe are conductive to building a heat pipe model, to predict the temperature distribution of the heat pipe in a steady state in a much more accurate manner. This paper offered a heat pipe model that applies the temperature difference of the phase change interface to calculate the evaporation and condensation. Meanwhile, a 1-meter-long sodium heat pipe was adopted to carry out steady-state heat transfer experiments. Measured and computed the temperature difference of the phase change interface of the heat pipe under varying power and temperature and conducted the relational equation as the input of the heat pipe model. The model predicted the steady-state temperature distribution of the sodium heat pipe and the transient when the power changes after the steam reach the continuous flow stage and compared the calculated outcomes with the experimental values. The transient error was less than 20K, and the steady-state error was less than 12K. The results show that the temperature difference at the phase change interface has a great influence on the steady-state temperature distribution of the heat pipe, which changes with the operating temperature. However, the physical and geometric factors affecting the temperature difference need to be further studied, to reduce the temperature difference as much as possible and improve the energy conversion efficiency of the heat pipe reactor system in the future.
Effect of Oxidizing All-Volatile Treatment on Alumina-Forming Austenitic Oxidation Behavior in Supercritical Water
Authors: Yang Gao , Sun Dayun , Cong Shuo , Zhang Lefu , Guo Xianglong
Published: November 2022

The corrosion behavior of a novel alumina-forming austenitic stainless (14Cr-24Ni-2.5Al) after 1000 hours of exposure to supercritical water (SCW) with deaerated and AVT(O) water chemistry.

X-ray diffraction, scanning electron microscopy, and energy dispersive spectroscopy was used to investigate the microstructure evolution of oxide layers and to explain the likely mechanism.

Although the corrosion weight gain in deaerated supercritical water was lower than in AVT(O), the weight gain curves of AFAs in deaerated SCW followed near-linear rate equations, whereas the kinetic weight gain curves in AVT(O) followed the near-parabolic rate equations.

The oxide film of AFAs could be separated into two distinct layers in both water chemistry environments, an exterior Fe-rich later and an inner Cr-Al internal oxidation layer, and neither formed a visible continuous alumina film, which was attributed to the lower Cr concentration.

The development of amorphous Fe2O3 oxide filling the magnetite spinel interstices may explain the reduced porosity of the outer iron oxide in the AVT(O) environment compared to the deaerated environment.

The reasons for the differences in corrosion behavior between the two chemical feedwater conditions were discussed and explained.

These findings revealed that while AVT(O) was not effective in short corrosion resistance, it can help with long-term corrosion resistance.
Research Progress of Neutron Shielding Materials
Authors: Chang Bing , Li Saisai , Li Minghui , Chen Ruoyu
Published: November 2022

Neutron shielding materials are widely used in aviation, medical treatment, nuclear reactor and other fields. Neutrons is difficult to shield because of their high energy. With the development of neutron shielding materials, different kinds of shielding materials have been developed. Compared with other kinds of materials, composite material is an ideal candidate for neutron shielding material because of their outstanding physical and chemical properties. Therefore, a lot of researchers continue exploring and preparing novel composite neutron shielding materials to meet the complex working conditions. This paper summarized the research status of different neutron shielding materials in recent years, mainly including inorganic non-metallic based neutron shielding materials, polymer based neutron shielding materials, metal based neutron shielding materials, beside for composite shielding materials. Moreover, the existing problems in the research of shielding materials and the possible future development direction are put forward.
Phase-Field Fracture Simulation of Dual-Cooled Annular Fuel Pellet
Authors: Li Wei
Published: November 2022

The dual-cooled annular nuclear fuel is an advanced design that is expected to greatly lower fuel temperature even under high linear power density, as compared to traditional cylindrical fuel pin. Although fuel temperature can be much lower, the annular pellet also receives much higher neutron fluence, which may induce severe cracking during normal operation. This work deals with quasi-static cracking of dual-cooled annular UO2 pellet under neutron radiation. The analysis is based on the phase-field fracture model coupled with an oxygen diffusion model, heat conduction model and mechanical equilibrium model. The considered thermo-mechanical properties and irradiation behaviors of the nuclear fuel are both temperature and irradiation dependent. Especially, the acceleration of fuel creep due to oxygen redistribution is included. The fracture is represented by a scalar phase-field variable governed by a cohesive phase-field fracture method. These models are numerically implemented in the multi-physics coupling simulation framework MOOSE. For the first time, the diffusion-thermo-mechanical coupled fracture model is applied to the dual-cooled annular UO2 fuel pellet cracking during reactor startup, power ramp and reactor shutdown. Preliminarily, UO2 irradiation creep is found to play an important role on the fuel pellet fragmentation. The developed capability supports interpretation of experimental data and can guide material design of advanced ceramic nuclear fuel.
Numerical Analysis of Simple Heat Equation to Predict the Opening Time of the Freeze Plug in Molten Salt Reactors
Authors: Ilham Muhammad , Okawa Tomio
Published: November 2022

Freeze plug is an important safety system that can be used in Molten Salt Reactors (MSRs). Capable of removing the decay heat of the fuel in the core by draining the liquid fuel in the core to the safety tank located underneath the core by gravity, with no use of a mechanical valve or operator and electrical supply. The better understanding of designing the freeze plug system, the more efficient the MSRs safety system will be. The opening time of the freeze plug is one of the major importance in ensuring the passive safety of the MSRs. In this study, systematic numerical simulations are carried out to understand the solidification and melting processes of salt in MSRs freeze plugs. The simulation results from a previous study showed that the steady-state form of the frozen salt in the solidification process has a big impact on the opening time of the plug in the melting process. Based on these results, a simple method to estimate the opening time using the thermal conduction theory was developed. It was found that the opening time of the simulation results has a good agreement with the opening time from the analytical equation. Thus, it was demonstrated that this method is useful to estimate the performance of well-designed freeze plugs.
Solution of Unsteady Flow Equations for Nanoscale Heat and Mass Transfer, Advanced Fluidics, Bioengineering, and High Energy Blast Wave Propagations
Authors: Sinha Ramlala P.
Published: November 2022

A new innovative stable time-dependent compressible flow solution over the order of nanoseconds is provided here for wide-ranging critically important challenging applications. Specifically, a solution of the highly complex unsteady high speed oscillating compressible flow field inside a cylindrical tube, closed at one end with a piston oscillating at very high resonant frequency at the other end, has been obtained numerically, assuming one dimensional, viscous, and heat conducting flow, by solving the appropriate fluid dynamic and energy equations. An iterative implicit finite difference scheme is employed to obtain the solution. The scheme permits arbitrary boundary conditions at the piston and the end wall and allows assumptions for tansport properties. In successfully predicting the time dependent results/data, an innovative simple but stable solution of unsteady fluid dynamic and energy equations is provided here for wide ranging research, design, development, analysis, and industrial applications in solving a variety of complex fluid flow heat transfer problems. The method is directly applicable to pulsed or pulsating flow and wave motion thermal energy transport, fluid-structure interaction heat transfer enhancement, nanoscale heat and mass transfer, diverse range of advanced fluidics, biofluidics / bioengineering, and fluidic pyrotechnic initiation devices. It can further be easily extended to cover muzzle blasts and high energy nuclear explosion blast wave propagations in one dimensional and/or radial spherical coordinates with or without including energy generation / addition terms.