bluuebunny/crossref_metadata_2025_split huggingface dataset:
From Three‐ to Six‐Membered Heterocycles Bearing a Quaternary Stereocenter: an Asymmetric Organocatalytic Approach
Authors: Lattanzi Alessandra 
Published: April 2023

AbstractThe development of procedures useful to form quaternary stereocenters stands out as a highly challenging task in asymmetric synthesis. With the arrival of organocatalysis, different activation strategies became available to pursue this intriguing target, thus leading to notable advancements of the area. In this account, our achievements, spanning over a decade, on asymmetric methodologies to access novel three‐, five‐, six‐membered heterocycles, including spiro compounds bearing quaternary stereocenters, will be highlighted. The Michael addition reaction has been often exploited to trigger cascade reactions, using organocatalysts mostly derived from Cinchona alkaloids, and operating under non‐covalent activation of the reagents. Further manipulations of the enantioenriched heterocycles, attested them as useful compounds to prepare functionalized building blocks.
Study on Resuspension Models Based on Force Balance
Authors: He Liwen , Tong Lili , Cao Xuewu 
Published: April 2023

AbstractDuring the severe accident of the nuclear power plant, the resuspension of the aerosol particles deposited in the containment would occur, due to some disturbance, resulting in the increase of radioactive aerosols released into the environment. Therefore, aerosol resuspension should be considered for the radiological consequence assessment. Accurate aerosol resuspension prediction model is very important.In this paper, three typical aerosol resuspension models considering force balance, named Wichner model, Michael model and ECART model, are investigated. These models follow the principle that resuspension occurs when the aerodynamic disturbing force is greater than the hindering force and differ in the consideration of the forces acting on particles. Wichner model proposes the aerodynamic disturbing force includes lift force, while Michael model considers it composed of lift and drag force, hindering effect of adhesive force is considered in the two models. ECART model considers the hindering force includes gravity, cohesive and adhesive force, the aerodynamic disturbing force is composed of drag, and burst force. Considering the aerosol characteristics and thermal hydraulic conditions during nuclear reactor severe accidents, the simulation for STORM and ART experiments with the three models is carried out. Finally, via comparing and analyzing the prediction results and experimental results, the applicability of these models is evaluated. Wichner model could reflect the rapid change of resuspension with the disturbing gas velocity and is in agreement with the experimental results for different particle sizes under different disturbing gas velocities, which is recommended for predicting aerosol resuspension behavior during nuclear reactor severe accidents.
The Main Reason of SG Thermal Power Imbalance Between Each Loop in CPR1000 Nuclear Power Plants
Authors: Shang Chao-hao , Hu You-sen , Guo Yuan-xiong , Li Chang-ying , Chen Jun 
Published: April 2023

AbstractThe SG thermal power imbalance between each loop exists in some CPR1000 nuclear power plants. In this paper, the authors trying to figure out the chief reasons of SG power imbalance between each loop by analyzing the measurement data from the Nuclear Power Plants. The main thermal parameters from the nuclear power plants are analyzed. By analyzing factors affecting the SG thermal power, the main factors affecting the SG thermal power are loop flowrate and hot leg temperature. The loop flowrate depends on the pump characteristic curve and the loop resistance coefficient. The hot leg temperature depends on RPV structure and core power distribution. A CPR1000 SG model was established and the sensitivity analysis of the coefficients which affect SG heat transfer is performed. The analysis results show that the deviation of the hot leg temperature between loops has the most significant effect on the SG thermal power imbalance. Hence, the SG thermal power imbalance between each loop mainly due to the RPV structure, the core power distribution and the flowrate deviation.
Hysteresis Behaviors of a Bump-Type Foil Bearing Structure with Amended LuGre Friction Model
Authors: Zhou Runeng , Gu Yongpeng , Ren Gexue , Yu Suyuan 
Published: April 2023

AbstractThe gas foil bearing (GFB) has the prospect of application in the nuclear field because of its oil-free lubrication and high-speed as well as high-temperature performance. In this paper, the hysteresis behaviors of the bump foil structure of bump-type gas foil bearings are investigated. The bump foil is modeled by beam elements and reduced by Guyan reduction method. The amended LuGre friction model is adopted and all the state variables are solved simultaneously in the fully coupled scheme. It is found that, along with the decrease of the friction stiffness per normal force, the presliding behavior is enhanced and it is more and more difficult to distinguish the stick and slip states, which results a decrease of the energy dissipation of hysteresis curves. Besides, the differences of high-slope and low-slope hysteresis curves are caused by the changes of stick and slip states of partial contact nodes close to the free end of the bump foil. Finally, the simulation results considering the Stribeck effect indicate that the high-slope and low-slope parts of hysteresis curves are dominated by maximum static friction coefficient and kinetic friction coefficient, respectively. Moreover, the comparisons of simulation and experimental hysteresis curves prove that the presliding behavior and Stribeck effect are prevalent phenomena in bump foil structure and should be taken into account in the modeling of the GFB system.
Discussion on Common Bolt Scuffing Factors and Control Measures in the Installation and Maintenance Stage of Nuclear Power Plant
Authors: Gong Xuefeng , Feng Xiaohan , Liu Xue , Mu Lianjun , Lu Jianxiang 
Published: April 2023

AbstractBecause of its high control precision, high efficiency, easy operation and safe to threads, bolt tensioning is widely used in many mainstream reactor types of nuclear power plants at home and abroad, such as M310, EPR, VVER, AP/CAP and HPR 1000. It plays an indispensable role in the installation and removal of foundation fixing bolts and flange connecting bolts of dynamic and static mechanical equipment in the construction and maintenance stage of domestic nuclear power plants. With the development and upgrading of bolt tensioner, the technology of bolt tensioning has become more and more mature. At present, it has become an irreplaceable means of bolt pre tightening.However, in the installation and maintenance stage of nuclear power plant, the fixing bolts and flange connecting bolts of mechanical equipment will still be jammed, damaged or even be scuffed. This situation may cause damage to bolts and bolt holes, which requires additional repair and rework costs and the construction period would delayed, or it may cause scrapping of bolts and bolt holes, and even affect the main functions of equipment and flanges, cause more serious economic losses and even nuclear safety accidents.This paper analyzes the common bolt scuffing factors in the installation and maintenance stage of nuclear power plant through the experience of actual disposal means on site of bolt tensioning and scuffing, and defines the corresponding control means pertinently, so as to reduce the bolt scuffing probability, and then reduce the additional cost in the installation and maintenance stage and even the probability of nuclear safety accident.Mainly analyze from the aspects of thread material, working environment, manufacturing tolerance, thread cleaning, bolt assembly, bolt tensioning and bolt fastening, and formulate standard and effective work plans for thread material inspection, working environment isolation, manufacturing tolerance inspection, thread cleaning, bolt assembly, bolt tensioning and bolt fastening in combination with the actual situation of the construction site, so as to ensure the reduction or even elimination of nuclear power plant installation The probability of bolt scuffing in the maintenance stage can enhance the quality of nuclear power installation and maintenance at the construction site of the nuclear power plant and improve the operation safety probability of the nuclear power plant.
Study on Unstructured-Mesh-Based Importance Sampling Method of Monte Carlo Simulation
Authors: Shu Hanlin , Cao Liangzhi , He Qingming , Dai Tao , Huang Zhangpeng , Wu Hongchun 
Published: April 2023

AbstractMonte Carlo (MC) method is widely adopted in radiation transport calculation due to its high accuracy, but suffers from high variance in deep-penetration problems. To obtain reasonable results, variance reduction techniques are necessary and thus be widely studied worldwide. The Consistent Adjoint Driven Importance Sampling (CADIS) method is proved to be an effective variance reduction technique, which generally employs finite-difference discrete ordinate (SN) code to obtain the adjoint flux, and generates parameters of source biasing and weight window for MC code. However, the finite-difference method, which models through structural meshes, will introduce considerable geometric approximations in complex geometry. The finite element method (FEM) performs calculations with lower truncation error and can employ unstructured meshes, which are capable of modeling complex geometry with relatively lower geometric approximations. Therefore, the adjoint flux calculated by unstructured-mesh FEM is able to generate more appropriate parameters of source biasing and weight window which will further reduce the variance of forward MC calculation. A fully automatic unstructured-mesh CADIS method is studied and implemented in this paper, parallel three-dimensional unstructured-mesh neutron-photon coupled transport calculation code NECP-SUN based on the SN method and discontinuous FEM is developed and embedded into the MC code NECP-MCX to calculate the adjoint flux with unstructured meshes. The updated code is applied to the HBR-2 benchmark, the numerical results show that the relative statistic error is reduced by up to 22% compared to the traditional CADIS method while the calculation results are closer to the measurements and the figure of merit (FOM) is increased by 3–4 orders comparing to direct MC simulation.
Research on Parameter Sensitivity for Deeply Embedment SSI Analysis Based on Sub-structuring Method
Authors: Liu Ziqiao , Wang Dongyang , Sun Xiaoying , Gan Yingying 
Published: April 2023

AbstractThis paper carried out a seismic analysis of a nuclear island structure under the site of a soft soil foundation, based on the spatial sub-structuring analysis method. In order to fully consider the influence of embedment effect in the analysis, the embedded part is modeled independently in the model. Then, the sensitivity effects from the number of interaction nodes and the radius of the cylindrical central area on the calculation time and results is studied. The research show that: (1) Selecting the nodes only at the boundary of the embedded part as the interaction points can significantly reduce the calculation time on the premise of ensuring the accuracy of the results. (2) The value of cylindrical radius in finite element model does not affect the calculation time and accuracy significantly, but has a certain effect on the spectrum value. It is suggested to determine the radius using the average value of the elements which are a large proportion in the model for an non-uniform mesh. In this paper, the suggested values for two parameters are provided based on the sensitivity analysis. The conclusions provide technical reference for the seismic analysis of the deeply embedded nuclear buildings.
Study on the Cause and Solution of Quadrant Power Tilt Rate Alarm in a PWR Plant
Authors: Jin Desheng , Li Qiubai , Mao Yulong , Zhang Wei , Hu Yousen 
Published: April 2023

AbstractDuring the normal operation of a pressurized water reactor plant, RPN430KA (quadrant power tilt rate over 3%) alarms were issued several times, and the alarm frequency increased with the increase of burnup, which affected the normal operation of the unit. The original signal of this alarm is from four power range channels (RPN). After the process of signal filtering, if the difference between the maximum and minimum nuclear power is still greater than 3%, the alarm will be triggered. In this paper, the root cause of the quadrant power tilt rate alarm phenomenon is studied, and targeted solutions are given. The research shows that the main factor affecting the alarm is the inconsistency between the filtering sampling time during the discretization process and the physical sampling time of the alarm signal, and the induced reason is that the fluctuation of nuclear power gradually increases with the deepening of burnup. The nuclear power fluctuation is a noise signal with too many complex factors but existed objectively. Therefore, in the case of large fluctuation of nuclear power, if the actual filtering effect is not achieved, it is easy to appear alarm phenomenon, which can be solved by modifying the sampling time of signal processing. The results of this paper can be used as reference for plant operation.
Solid-Liquid Equilibria of Ternary Systems UO2(NO3)2 + HNO3 + H2O and UF4 + HF + H2O at 298 K
Authors: Lin Wang , Dan Xu , Jianxin Feng , Hanlong Cui , Wenhui Wang , Yingxi Zhu 
Published: April 2023

AbstractUO2(NO3)2 and UF4 are significant intermediates that connect different chemical unit operations (such as dissolution, evaporation, concentration, extraction and etc.) in uranium chemical industry. Commonly, there is a basic physicochemical question about phase equilibrium of ternary systems UO2(NO3)2 + HNO3 + H2O and UF4 + HF + H2O, it is crucial to understand the phase behavior and thermodynamic properties of them with the continuous development of uranium chemical industry. In this study, solid-liquid phase equilibria of ternary systems UO2(NO3)2 + HNO3 + H2O and UF4 + HF + H2O at 298 K were studied by means of isothermal dissolution method, the solubilities and densities of equilibria liquid phase were investigated experimentally for two systems, the composition of equilibria solid phase of system UO2(NO3)2 + HNO3 + H2O at 298 K were determined by Scherinemakers’ wet residue method, and the method of X-ray diffraction was used to determine the composition of equilibria solid phase for system UF4 + HF + H2O at 298 K. Phase diagrams and diagrams of density-composition were constructed for systems UO2(NO3)2 + HNO3 + H2O and UF4 + HF + H2O at 298 K. Results show that there are unique isothermal dissolution curve for two ternary systems, and corresponding crystallization zone are UO2(NO3)2·6H2O and UF4·2.5H2O, respectively.
Thermo-Physical Property Database of Fusion Materials and Thermo-Hydraulic Database of Breeder Blankets for CFETR
Authors: Ding Wen , Zhang Kui , Chen Ronghua , Tian Wenxi , Zhang Jing , Qiu Suizheng , Su G. H. 
Published: April 2023

AbstractThe Chinese Fusion Engineering Test Reactor (CFETR) is a fusion engineering reactor independently designed and developed by China, and the design of the blanket is one of the key points during the design of CFETR. The configurations of CFETR, the detailed designs of the three types of blankets and typical blanket module, and the coolant flowing schemes in blanket module are introduced in paper. Besides, the work about Thermo-physical Property Database of Fusion Material and Thermo-hydraulic Database of Models established for the three types of blankets is presented. The fusion material involves Plasma Facing Materials (PFM), structural materials, coolant and breeding materials, and the peak temperature and the peak pressure in both steady-state and transient conditions are covered for property of materials. The thermo-hydraulic database includes the heat transfer models, the pressure drop models, and some special models for the fluid flow in blanket. In addition, the tests and verification for the database are performed, and the shortages and deficiencies of current database are analyzed.
Derivation of Activity Concentration Upper Limits for Low Level Solid Radioactive Waste
Authors: Liu Jianqin , Gao Chao , Zhang Li , Qin Xiang 
Published: April 2023

AbstractThe derivation method of activity concentration upper limits for low level radioactive waste is put forward. The activity concentration upper limits for low level solid radioactive waste will be ascertained, on the basis of safety assessment of near surface disposal. On the premise of basic safety requirements about radioactive waste near surface disposal, taking Yaotian disposal site and Feifengshan disposal site as the reference sites, the drilling water scenario, drilling scenario, post-drilling scenario, and housing scenario after the institutional control period when the disposal sites have been closed are considered. The radionuclide transfer process and exposure pathway of various scenarios are analyzed, the conceptual model and mathematical model of radionuclide transfer are established, and the effective dose to human from various scenarios is calculated. Assuming a linear relationship between the activity concentration and the dose, the activity concentration upper limits of various scenarios are then derived for each radionuclide that meet the appropriate dose criteria. The smallest upper limit is chosen, by the approximate integer principle, the magnitude of upper limit of each radionuclide for low level solid waste is then ascertained.
Research on Thermal-Hydraulic Model and Characteristics of Lead Cooled Traveling Wave Reactor
Authors: Zhang Yaoxiang , Zhang Xue , Yu Hongxing , Du Sijia 
Published: April 2023

AbstractTraveling wave reactor (TWR) is an advanced nuclear power system, which can keep the total amount of fissionable nuclides constant during its lifetime through the transformation of fissionable nuclides in the reactor, so as to maintain the stability of the effective proliferation factor of the reactor core. As a coolant, lead has low neutron moderation ability and capture cross section. At the same time, it also has excellent thermal characteristics. Lead cooled traveling wave reactor is a reactor with high inherent safety and good application prospects. The research on reactor core mainly focuses on the physical calculation of the reactor, and the analysis of its thermal hydraulic model and characteristics is relatively scarce, which limits the design and safety analysis of the advanced reactor. Therefore, it is necessary to investigate the thermal hydraulic model of lead cooled traveling wave reactor. In this paper, a thermal hydraulic model suitable for the core of lead cooled traveling wave reactor is proposed. Considering the axial particularity of heat release from the core of traveling wave reactor, the model considers the axial thermal conductivity of fuel rods ignored by other thermal hydraulic models. Due to the strong thermal conductivity of core coolant, the thermal model also considers the heat transfer of fuel assemblies and the flow distribution of core flow. The research shows that the thermal hydraulic model is suitable for the analysis of thermal hydraulic characteristics of lead cooled traveling wave reactor, the thermal hydraulic characteristics are studied by using the thermal hydraulic model.
Design and Application of γ-Ray Energy Spectrum Survey System Based on UAV
Authors: Li Jiangkun , Zhang Wei , Wu Xuliang , Wu Xue , Wei Bin , Wu Leichao , Li Yizhou , Wang Peijian 
Published: April 2023

AbstractAirborne γ-ray energy spectrum measurement is an effective method for radioactive mineral investigation and radiation environment monitoring. In recent years, with the gradual maturity of Unmanaged air vehicle (hereinafter referred to as UAV) technology, UAV airborne geophysical survey technology is becoming a hot research field. But the UAV has less load and space and is difficult to carry traditional aeronautical geophysical equipment. The miniaturization, intelligentization and automation of airborne geophysical survey instruments are the key technologies of airborne geophysical survey for UAVs. The γ-ray energy spectrum measurement system is designed suitable for UAV platform with load in the range of 30–180 kg, at the same time, the data acquisition control and remote monitoring software is developed. The calibration of the system is completed on the Shijiazhuang airborne standard model and Huangbizhuang dynamic belt, and the calibration parameters are obtained, the resolution of the crystal is better than 8.5%, and the peak drift is better than ±1, the sampling frequency of energy spectrum data is 1 Hz. Based on SY-120H and CH-3 UAV platforms, test flights were carried out in Karamay, Xinjiang and Erlianhot, Inner Mongolia, respectively, to find out the distribution of radioactive field in the test area and quickly delineate the specific location and range of the radioactive anomaly. The test results show that: UAV aviation γ The results of K, U and Th content measured by energy spectrum are basically consistent with those measured on the ground, which can provide a fast and efficient exploration technology and equipment for radioactive mineral investigation and radiation environment monitoring.
Minor Actinides Transmutation in Thermal, Epithermal and Fast Molten Salt Reactors with Very Deep Burnup
Authors: Zou Chunyan , Yu Chenggang , Zhou Jun , Chen Shuning , Wu Jianhui , Zou Yang , Cai Xiangzhou , Chen Jingen 
Published: April 2023

AbstractDeep burnup and high minor actinides (MA) loading are two alluring features for molten salt reactors (MSR) to incinerate the nuclear wastes. The transmutation capability of minor actinides in MSR is tightly related with the neutron spectrum, the loading of MA and the carrier salt compositions. In this work, three MSR core designs (thermal, epithermal and fast) and two types of salt compositions (Flibe and Flinak) with different solubility limits of transuranic elements are chosen for analyzing the transmutation capability of MA. With a significant mole fraction of MA loading (4% in the Flibe salt and 10% in the Flinak salt) and the continuous MA refueling, MSR acquires an excellent transmutation rate. The specific incineration rates of MA in the thermal, epithermal and fast MSR cores with the Flibe salt are about 167, 185 and 206 kg/GWth/y, respectively. With a larger loading of MA in the Flinak salt, a higher annual incineration rate of MA can be obtained, which are about 170, 206 and 247 kg/GWth/y in thermal, epithermal and fast MSRs, respectively. On the other hand, since there is a preferred neutron economy for the Flibe salt, a higher MA incineration ratio is achieved than that for the Flinak salt. When the neutron spectrum varies from the thermal to fast region, the MA incineration ratio ranges from 0.79 to 0.82 for the Flibe salt and it ranges from 0.75 to 0.81 for the Flinak salt. The transmutation capability of MA in MSR is much higher than that in solid-fueled reactors (~20 kg/GW.y in a PWR), which can provide a feasible way for reducing the current nuclear wastes.