bluuebunny/crossref_metadata_2025 huggingface dataset:
Physics design of new lower tungsten divertor for long-pulse high-power operations in EAST
Authors: Xu G.S. , Wang L. , Yao D.M. , Jia G.Z. , Sang C.F. , Liu X.J. , Chen Y.P. , Si H. , Yang Z.S. , Guo H.Y. , Du H.L. , Luo Z.P. , Li H. , Zhou Z.B. , Cao L. , Xu H.C. , Xu T.J. , Wang Z.L. , Zi P.F. , Li L. , Han L. , Xu J.C. , Liu J.B. , Li K.D. , Cao B. , Yu Y.W. , Ding F. , Ding R. , Yan N. , Meng L.Y. , Tao Y.Q. , Wang H.Q. , Zhang Y. , Shao L.M. , Zhang X.D. , Zhu S.Z. , Wan B.N. , EAST Team the
Published: October 2021

A new lower tungsten divertor has been developed and installed in the EAST superconducting tokamak to replace the previous graphite divertor with power handling capability increasing from <2 MW m−2 to ∼10 MW m−2, aiming at achieving long-pulse H-mode operations in a full metal wall environment with the steady-state divertor heat flux of ∼10 MW m−2. A new divertor concept, ‘corner slot’ (CS) divertor, has been employed. By using the ‘corner effect’, a strongly dissipative divertor with the local buildup of high neutral pressure near the corner can be achieved, so that stable detachment can be maintained across the entire outer target plate with a relatively lower impurity seeding rate, at a separatrix density compatible with advanced steady-state core scenarios. These are essential for achieving efficient current drive with low-hybrid waves, a low core impurity concentration and thus a low loop voltage for fully non-inductive long-pulse operations. Compared with the highly closed small-angle-slot divertor in DIII-D, the new divertor in EAST exhibits the following merits: (1) a much simpler geometry with integral cassette body structure, combining vertical and horizontal target plates, which are more suitable for actively water-cooled W/Cu plasma facing components, facilitating installation precision control for minimizing surface misalignment, achieving high engineering reliability and lowering the capital cost as well; (2) it has much greater flexibility in magnetic configurations, allowing for the position of the outer strike point on either vertical or horizontal target plates to accommodate a relatively wide triangularity range, δ
l = 0.4–0.6, thus enabling to explore various advanced scenarios. A water-cooled copper in-vessel coil has been installed under the dome. Five supersonic molecular beam injection systems have been mounted in the divertor to achieve faster and more precise feedback control of the gas injection rate. Furthermore, this new divertor allows for double null divertor operation and slowly sweeping the outer strike point across the horizontal and vertical target plates to spread the heat flux for long-pulse operations. Preliminary experimental results demonstrate the ‘corner effect’ and are in good agreement with simulations using SOLPS-ITER code including drifts. The EAST new divertor provides a test-bed for the closed divertor concept to achieve steady-state detachment operation at high power. Next step, a more closed divertor, ‘sharp-cornered slot’ divertor, building upon the current CS divertor concept, has been proposed as a candidate for the EAST upper divertor upgrade.
Study on the influence of geometric imperfections and welding deformation on the global stability of orthogonal mixed with oblique single-layer reticulated shell
Authors: Wang Y M , Zheng F H , Wang J , Ju J S , Sang X X
Published: October 2021

Using finite element method to study the influence of geometric imperfections and welding deformation on the global stability of orthogonal mixed with oblique single-layer reticulated shells. The initial imperfection values of different geometries and the effects of welding residual deformation on the global stability of the ultimate bearing capacity of the structure are compared, and the difference between the instability modes of the two kinds of reticulated shells in the structure is analysed. It is shown that the residual welding deformation almost has no impact on the ultimate bearing capacity of the structure, and the initial geometric imperfections with the first buckling mode have a more obvious effect on the stability of the shell. The rigidity of the orthogonal single-layer reticulated shell is greater than that of the oblique. The deformation of the oblique single-layer reticulated shell is always greater than that of the orthogonal shell in the middle of the shell span or the position of the support.
Research on suppressing brittle fracture and implementing ductile mode cutting for improving surface quality at silicon wafers manufacturing
Authors: Kovalchenko A M , Pashchenko E O , Savchenko D O
Published: October 2021

Single crystal silicon is an important basic material used to manufacture electronic and photovoltaic devices. Ductile mode of diamond wire sawing is a promising method for silicon wafering in order to produce wafers with minimal surface damage. To achieve ductile mode, the correct applying of cutting parameters and careful wire design is necessary. This study investigates the scratching of monocrystalline silicon by the abrasive particles of different geometry, which simulates the material removal process in diamond wire sawing. Diamonds, crushed and spherical tungsten carbide (WC) particles served as abrasives. Experiments show that spherical abrasives enhance ductile mode cutting significantly decreasing brittle damage when compared to irregular shape particles. Spherical WC particles permit to increase the critical load and critical cut depth of ductile-to-brittle transition from 5 to 10 times. The depth of the damaged subsurface layer decreased from 5 µm to 0.2 µm due to the absence of brittle cracks. A uniform regular distribution and appropriate suitable density of abrasive particles is obligatory for cracking reduction. For that, the method of diamond particles uniform deposition with the controlled density by a polymer binder combining high modulus and adhesive capacity with good flexibility was elaborated. The method includes preliminary diamond particles fixation on a thin resin layer providing high uniformity and subsequent strong fixation by a thicker resin layer. The research on ovalization of diamond particles was performed for smoothening cutting edges. The method is based on the activation of the graphitization process at sharp edges of particles under the action of metal salts at increased temperatures.
Research and application of supramolecular gel plugging agent in abnormal pressure reservoir
Authors: Baletabieke B , Gu Y X , Zhou T , Duan D X , Liu J T , Kong X J , Qian F , Li W J , Zhong Z , Xiang Y , Jing N , Li J Y
Published: October 2021

The Aktobe project is the largest oil and gas producing area of PetroChina in Central Asia. However, after years of exploitation, the pressure of the reservoir has dropped, making it difficult to increase the production of a single well. Both the Kenkyak block and North Troyes block of the project have induced fractured leakage, and frequent leakage affects safe and efficient drilling and completion operations and production. Therefore, the research on leakage prevention and control technology is very necessary. This article focuses on the characteristics of the cracks in the high-pressure area of the Kenkyak block and the cracks in the low-pressure area of the North Troyes block. Aiming at the fracture characteristics of the high-pressure zone in the Kenkyak block and the low-pressure zone in North Troyes block, and taking advantage of the synergistic effect of supramolecules, a supramolecular plugging-while-drilling agent was developed based on the deformable fiber composite gel. It forms a strong adhesion plugging layer on the inner wall of the leakage channel through the strong adhesion force, and it achieves a good plugging effect. The 300-500mD sand disc bearing pressure could reach 700psi when adding 3% agent, and the bearing pressure of 3-5D permeability sand disc could reach above 450psi. A supramolecular static plugging agent was also developed based on the dilatant gel. It is rich in strong shear reversible gel with supramolecular structure, which guarantees its pumpability and plugging performance. The effective rate of one-time plugging is over 80%, and the viscosity is greatly reduced after the gel is broken for 72hr, which benefits the reservoir protection.
Electrical conductivity of polymer/carbon nanofillers composites
Authors: Kostromin S , Bronnikov S
Published: October 2021

Using a broadband dielectric spectrometry we studied the effect of carbon nanofillers (CN) with various aspect ratio (fullerene C60, multi-walled carbon nanotubes (MWCNT), reduced graphene oxide (rGO) and hybrid rGO:MWCNT nanofillers) on the electrical conductivity of the polyazomethine-based nanocomposites. One-dimensional MWCNTs with high aspect ratio were shown to be the most effective CN for fabrication of polymer-based nanocomposites with enhanced electrical conductivity.
Fatigue detection and analysis of drilling tools based on metal magnetic memory method
Authors: Zhang J W , Fan J C
Published: October 2021

With the vigorous development of offshore oil and gas resources in the world, underwater extended reach horizontal wells have been widely used. However, due to the complicated stress and serious corrosion of drill pipes in horizontal wells, drill pipes are vulnerable to damage. After a period of service at sea, some drill tools will be placed in coastal areas for a long time. The cumulative fatigue of drilling tools is not easy to master. In the past year or two, drilling tool failure has become more and more frequent. In order to evaluate the fatigue of drilling tools in different periods and master the quantitative fatigue of drilling tools, the metal magnetic memory method has its unique advantages in detecting the stress concentration and early damage of ferromagnetic materials. The self-developed metal magnetic memory detection device is used to detect the drilling tools in the drilling tool base. The results show that the gradient peak value and ladder are used to detect the drilling tools in the drilling tool base. The average degree can be used to classify the fatigue of drilling tools, and the metal magnetic memory method is more than sensitive to various defects of drilling tools, such as penetration, internal corrosion, external corrosion, wall thickness thinning, etc.
Three- dimensional numerical simulation analysis of the influence of structural parameters on the performance of air ejector
Authors: Han L F , Liu T J , Li L , Liu D Q
Published: October 2021

Nowadays, CFD technology has become the third tool to study hydrodynamics problems after theoretical analysis and experimental research, especially in dealing with and solving complex engineering problems such as supersonic. In this paper, using the method of control variables, the system studied a type air ejector structure parameters within a certain range changes affect the performance of the work by means of FLUENT, at the same time, the optimal combination of the structural parameters are given, then three dimensional numerical simulation of the optimal combination model, and the simulation value and experiment value has carried on the contrast and analysis, Compared with the two-dimensional and axisymmetric model, Three-dimensional calculation model is more reliable and reasonable.
Experimental research on shear performance of single bolt joints of bamboo curtain plywood
Authors: Tang G , Wu X N , Sun P , Yang C T
Published: October 2021

This paper focuses on the shear resistance of the bolted connection between steel plate and bamboo curtain plywood. From the fifteen groups of specimens, the performance grade, bolt diameter and end distance of bolts have an influence on the ultimate bearing capacity of joints and the yield load of joints and the yield load is 65%∼75% of the ultimate load. The initial stiffness of the node increases with the bolt diameter increasing. Provide certain materials and theoretical references for bamboo in the future design and research.
Analysis of aging status of silicone rubber insulation material and research progress of its repair countermeasures
Authors: Li B , Huang H , Fan L , Pan G X , Tan Z , Li F , Xie X W , Zhang Z J
Published: October 2021

Due to its good hydrophobicity and hydrophobicity migration, silicone rubber can be used as umbrella sheath of insulators. With the continuous deterioration of environmental conditions, silicone rubber insulators in the process of power grid operation are vulnerable to a variety of environmental factors, such as humidity, partial discharge, ultraviolet radiation, icing and so on, which lead to a significant decline in hydrophobicity, mechanical properties and electrical properties, and bring serious threats to the safe operation of power grid. At present, the anti-pollution flashover mode of power grid power transmission and transformation equipment, which takes cleaning as the main method, can-not adapt to the current power grid operation environment and the impact of harsh environment, resulting in frequent power grid safety accidents. This paper summarizes the influencing factors, aging mechanism and evaluation methods of aging degree of silicone rubber insulators at present, and how to repair aging insulators and improve their anti-pollution flashover performance. Finally, the effective repair of aging silicone rubber insulator is summarized and prospected, the aging factors of insulator in specific environment are analysed, and corresponding countermeasures are taken to repair, which lays a good theoretical foundation for the future research of silicone rubber insulation materials.
Development of ideal processing parameters for powder bed fusion system processing of AlSi10Mg using design of experiments
Authors: Mathe N R
Published: October 2021

The additive manufacturing of aluminium alloys has gained great interest in the transport industry in the past 10 years. This is mainly due to the lightweight and good strength that these alloys offer especially for applications in aerospace and other related industries. However, there is a drawback in using these alloys especially the parts produced by additive manufacturing as they have to be heat treated before application to relieve residual stresses caused by the fast heating and cooling experienced during powder bed fusion (PBF) fabrication. Most of the current PBF metal system offer a variety of processing parameters for part building, however AM uptake and industrial implementation is still slow due to restrictions of the laser power and laser interaction time that are slow and thus the parts take long to produce. Seeing this lag in the market, the CSIR has produced a high speed and high power PBF machine with a build platform larger than the currently available commercial systems. This system allows for the faster production of parts due to its higher consolidation rate and it has already been validated for aluminium alloys, specifically AlSi10Mg. The properties evaluated were microstructure and hardness, which found to be comparable to commercial PBF machines. The samples were analysed for microstructure, mechanical properties using tensile testing procedure. In order to determine that ideal processing window, the response surface methods was used on the Stat-Ease Design Expert software using ultimate tensile strength, elongation and hardness as outputs. Based on the data analysed, the processing window was narrowed to 1400 W laser power and 1.63 – 1.95 s interaction time.
Effect of powder particle size on performances of SiC ceramic balls
Authors: Shi X M , Wang Q , Cheng Y Y , Zhang L , Zheng Y S , Zhang L J , Ren L H , Shi G P
Published: October 2021

The silicon carbide ceramic balls were prepared with different mean particle sizes of 0.5μm and 1.0μm. The powder particle size’s impacts on sintering density, crushing load ratio, hardness, fracture toughness, surface quality and microstructure of ceramic balls were investigated. The results show that the hardness and sintering density with different powder particle sizes were similar. Ceramic balls prepared with finer powder whose mean particle sizes 0.5μm are observed with better mechanical properties and structural homogeneity. The sintering density of ceramic balls with mean particle sizes 0.5μm is 3.118g/cm3, the average of Vickers hardness, average crushing load ratio and fracture toughness is HV2125, 60.6% and 3.22MPa/m1/2.
Corrosion and mechanical behavior of 17G1S-U pipeline steel and its weld joint of in the terms simulating operational conditions
Authors: Nyrkova L I , Prokopchuk S M , Goncharenko L V , Osadchuk S O
Published: October 2021

Corrosion and mechanical behavior of weld joint samples of the straight-weld pipe of 17G1S-U pipeline steel in the conditions simulating the operating conditions of internal and external corrosion has been studied. It is shown that the initiation of local corrosion of welded joints from the inner surface of the pipeline is due to thin-film corrosion in a two-phase medium (hydrocarbon-water) under deformation conditions. The depth of local damages of the base metal and weld metal can reach 0.337 mm and 0.381 mm. Stress corrosion cracking is a danger for the outer surface which is under cathodic protection. Maintaining the potential at the level of the maximum protective potential -1050 mV increases the stress corrosion cracking inclination of pipeline 17G1S-U steel and its weld joint, due to deterioration of the plastic properties of the metal during longtime exposure at cathodic polarization: decreasing in the relative elongation of the base metal is equal near 11 %, weld joint – by 20%. The KS susceptibility, estimated by the KS coefficient, under these conditions is equal to 1.8 for 17G1S-U steel, 1.5 for weld joint.
Influence of welding sequence on the mechanical properties of a latticed shell formed by orthogonal and oblique members
Authors: Wang Y M , Sang X X , Ju J S , Zhang H D , Fu Y Q
Published: October 2021

With the development of economy and the improvement of people’s aesthetic level, large-span latticed shells are increasingly used. Such structures are commonly large in volume and huge in welding. In order to select an optimum welding sequence and avoid correcting complex welding deformation, a latticed shell formed by orthogonal and oblique members was taken as the research object in this paper. The finite element models of single and whole latticed shells were established respectively, and according to the equal deformation principle, the influence of different welding sequence on the deformation and internal force of the structure in each construction stage was quantitatively analyzed. The results show that in the welding and assembling stage of small assembling units in the single latticed shell, welding sequence has the greatest impact on the longitudinal deformation, and the change rate of the longitudinal deformation is up to 83.63%; whereas in the tension, sliding and closure stages of each piece of the latticed shell, the transverse deformation is most affected by welding sequence, and the change rate is 33.05%; in different construction stages, the axial stress of the latticed shell is less vulnerable to welding sequence. Furthermore, it is feasible to control the welding shrinkage deformation by selecting a reasonable welding sequence, and the symmetrical welding sequence from both ends to the middle should be adopted during construction.
Effect of carbon source type on phosphorus removal efficiency of MBBR and characteristics of fluorescent substances in water
Authors: Sun J X , Wang M , Zhang X , Zhang Y T , Huang C , Wan L
Published: October 2021

In this paper, Moving Bed Bioreactor (MBBR) reactor was used as the research object to explore the effects of carbon source type on phosphorus removal performance of MBBR system and the changes of microbial metabolic characteristics in typical cycles. The results showed that the absorption and release of phosphorus by sodium propionate and starch were obvious. The accumulation and degradation of PHA and glycogen were observed in the three reactors, and PHA was prior to glycogen decomposition. When sodium acetate was used as carbon source, glycogen decreased during the stationary phase, and the other two did not change significantly. The intensity of fluorescent substances varies greatly with the type of carbon source. The fluorescent substances in the effluent are mainly tyrosine-like and protein-like substances, fulvic acid-like substances and humic acid-like substances. Therefore, the suitable carbon source type should be selected according to the microbial characteristics in the water treatment process to improve the treatment efficiency.
Evaluation of thermal control performance of phase change materials for thermal shock protection of electronics
Authors: Yang X H , Huang C H , Ke H B , Chen L , Song P
Published: October 2021

Phase change materials have important application value in the fields of heat storage, cold storage, and thermal shock protection of electronic chips. In particular, in the field of chip thermal shock protection, phase change materials can use the solid-liquid phase change process to absorb a large amount of latent heat, thereby suppressing the temperature rise of the chip and preventing it from overheating. At present, there are mainly three types of common phase change materials: organic, inorganic and metallic phase change materials. There exists significant difference in the thermophysical properties of the three types of materials, and their thermal control performance also have their own characteristics. This paper sorts out the main thermophysical data of the three types of phase change materials. Through theoretical modeling and analysis, the thermal control performance of these materials is quantitatively evaluated and compared. For typical chip thermal shock conditions, the three types of phase change materials are compared, and their typical characteristics are intuitively displayed. The research results can serve as value reference for the development of phase change thermal control technology for chips.
Experimental research on thermoelectric application characteristics of thermobattery
Authors: Xiao L X , He Y T , Li L
Published: October 2021

In this work, experimental research was carried out to investigate the conversion output characteristics of thermobattery. The results showed that under the same temperature difference, the open-circuit voltage of the thermobattery showed a tendency of first increasing and then decreasing with the increase of hot end temperature. Under hot-end temperature of 95°C, the output open-circuit voltage reached the maximum. In addition, there was a maximum output point for the thermobattery. Regarding the thermobattery (TGM-287-1.4-1.5), its output power reached the maximum when the load resistance was 9Ω. This research provides a theoretical and experimental basis for the optimal design of thermoelectric power generation system.
A balancing control method by considering lithium batteries state of charge
Authors: Li P P , Jia Y F , Yang Z X , Song Z Z , Xiong Y X , Cheng M M
Published: October 2021

In order to quickly and accurately reduce the inconsistency of charge between lithium battery and prolong the service life of lithium battery, a balancing control method for lithium batteries state of charge (SOC) is proposed in this paper. The difference of each adjacent battery pack in the series lithium batteries and the difference of each adjacent battery pack in each monomer lithium battery are used as the equalization criteria, a bi-directional energy flow topology circuit is constructed using inductor as energy storage element. The magnitude and direction of the equalization current are controlled, and the balancing control of the whole lithium batteries is finally realized by controlling the on-off time of the Mosfet tube. Compared with the traditional extreme difference control method, the simulation results show that the two-level layered balancing control method proposed in this paper increases the rapidity of static and random currents by 23% and 17.1% respectively, and the accuracy increases by 13.3%. The proposed control approach can be provided with equalization efficiency highly, and give some advice for servicing lithium battery application.
The Challenges of Implementing the Indonesian Experimental Power Reactor (RDE) Program
Authors: Wisnubroto D S , Sunaryo G R , Susilo Y S B , Bahri S , Setiadipura T
Published: October 2021

This paper shows the effort to implement the RDE and its challenges from 2013 to 2018. RDE was a program to introduce nuclear power plants by building non-commercial power reactors. The RDE program was also used to prove that Indonesian engineers can design a reactor that will later supply electricity and steam for industry. The technology used is a high-temperature gas-cooled reactor. This RDE program is a very strategic intermediate target for energy security and national sovereignty. The development of RDE-based nuclear power plants, in the long run, is expected to have implications for reducing reliance on fossil fuels, more self-sufficiency in energy supply increases national industrial capacity and competitiveness in the global economic order, as well as enhance energy and political diplomacy. Also, RDE can be a reference installation for PeLUIt (Power and Steam Generators for Industry) power plants for small and medium enterprises to meet the demand for electricity and industrial heat in an area’s needs. However, many challenges occurred to implement this program; among them were cost estimation and cost-benefit analysis. Although the program has not been realized, mainly for financial reasons, many positive things have been obtained from these activities.
Uranium Exploration, Deposit and Resources: The Key of Nuclear Power Plant Development Program in Indonesia
Authors: Syaeful H , Sukadana I G , Susilo Y S B , Indrastomo F D , Muhammad A G , Ngadenin
Published: October 2021

Uranium deposit in Indonesia was found in almost all Indonesian Archipelago, mainly in Kalimantan, Sulawesi, Sumatera, Papua, Bangka Belitung and Riau islands. Uranium exploration activities started in the 1960s to recent, conducted in many exploration stages. The exploration in prospects area are completed with drilling activities to delineate the mineralization zone and continued to resources estimation. In Kalan Area, the research had been completed with underground/tunneling mining. The uranium resources are classified into discovered or undiscovered based on exploration stages, and conventional or unconventional based on sources of primary/secondary/by-product mineral production. The resources are calculated from Kalan Area and its surroundings (Kalimantan) with addition of Mamuju Area (West Sulawesi) and Sibolga Area (North Sumatera). Uranium identified resource in Indonesia is 13,503 tU while the undiscovered is 62,330 tU. Meanwhile, categorized by uranium source, the conventional and unconventional resources are 48,388 tU and 27,445 tU respectively. The uranium resources categories should be increased and completed with feasibility study to increase the resources to reserve classification. The exploration, deposit, and resources are the key to ensure the readiness of developing nuclear power plants in Indonesia, where one of them is Experimental Power Reactor (EPR) or Reaktor Daya Eksperimental (RDE) with domestic uranium fuel.
Cost Analysis of Nuclear Hydrogen Production Using IAEA-HEEP 4 Software
Authors: Dewita E , Prassanti R , Widana K S , Susilo Y S B
Published: October 2021

Hydrogen is a commercially important element. Basically, there are several methods of hydrogen production that have been commercially used, such as Steam Methane Reforming (SMR), High Temperature Steam Electrolysis (HTSE), and thermochemical cycles, like Sulphur-Iodine (SI). Among these methods, SMR is the most widely used for large-scale hydrogen production, with conversion efficiency between 74–85% and it has commercially used in some fertilizer industries in Indonesia. Steam reforming is a method to convert alkane (natural gas) compounds to hydrogen and carbon dioxide (synthetic gas) by adding moisture at high pressure and temperature (35-40 bar; 800-900°C). These hydrogen production technologies can be coupled with different nuclear reactors based on the heat required in the process. The High Temperature Gas-cooled Reactor (HTGR) using helium as a coolant, has a high outlet temperature (900°C), so it can potentially be used to supply for process heat for hydrogen production, coal liquefaction/gasification or for other industrial processes requiring high temperature heat. Hydrogen production cost from SMR method is influenced by a range of technical and economic factors. The fuel component of natural gas needed in the SMR method can be replaced by nuclear heat from a nuclear power plant (NPP) operating in cogeneration mode (i.e. simultaneous producing electric power and heat), hence contributing to the reduction of carbon dioxide in the process.

In the SMR method, fuel costs are the largest cost component, accounting for between 45% and 75% of production costs. Therefore, there is opportune to assess the economics of hydrogen production by using nuclear heat. The economic evaluation is done by using IAEA HEEP-4 Software.

The results comprise cost break up for 2 cases, coupling SMR process for hydrogen production with: (1) 2 HTGRs of 170 MWth/unit; and (2) 1 HTGR of 600 MWth/unit. The cost of hydrogen production is highly depend on the scale of the NPP as energy source and results indicated that hydrogen production cost of the 1 HTGR Unit600 MWth (Case 2) has a lower value (1.72 US$/kgH2), than the cost obtained when 2 HTGR units of 170 MWth each (case 1) are considered (2.72 US$/kgH2). For comparison, the hydrogen production cost by using SMR with carbon capture and storage (CCS) with natural gas as fuel is 2.27 US$/kgH2.
Consecutive Heat Treatment of Pre-lathed Pebble Fuel Elements for HTGR
Authors: Zhou X , Wang L , Kang Y , Zhang S , Li J , Shi X , Liu B , Zhang J , Tang Y
Published: October 2021

In current manufacture process of pebble fuel elements for HTGR, the green pebbles were first carbonized, then lathed and purified at high temperature. The whole heat treatment process included two cycles of heating and cooling and corresponding two loading and unloading processes, which took approximately 90 hours in total. In order to reduce the time and energy consumed and improve the efficiency during the heat treatment process, a consecutive heat treatment process of pebble fuel elements for HTGR was established. In the newly established consecutive heat treatment process, the pebble fuel elements were carbonized and high temperature purified continuously in a specific furnace. The consecutive heat treatment process took less than 60 hours, which included only one cycle of heating and cooling and corresponding one loading and unloading process. Moreover, in order to recycle the matrix graphite powder after lathing, the green pebbles were machined to a certain size before suffering the heat treatment. However, in order to make the size of pebble fuel elements after the consecutive heat treatment meet the technical requirements, it is necessary to figure out their dimension changes during the heat treatment. As the pebbles were prepared by cold quasi-isostatic molding method, their dimension changes parallel and perpendicular to the molding direction were different. In order to better control the dimension changes of pebbles in the heat treatment process, the effects of physical properties such as apparent density, and particle size distribution of matrix graphite powder on the prepared pebbles were comparatively studied. Finally, the consecutive heat treatment of pre-lathed pebble fuel elements for HTGR was established. The comprehensive properties of pebbles prepared with the newly established consecutive heat treatment process satisfied all the technical requirements.
Hyphenated SEM-Raman Characterization for Matrix Graphite of HTGR Spherical Fuels
Authors: Jiao Z , Chen X , Zhang C , Xu G , Liu B , Yin Z
Published: October 2021

Matrix graphite (MG) is an important material for the spherical fuel elements of high temperature gas-cooled reactors (HTGR). After carbonization, the matrix material is composed of three isomers of natural graphite, artificial graphite, and carbon derived from phenolic resin (resin carbon) with the same element but different structure. According to previous study, the three components have different effect on the fission products diffusion and adhesion in the irradiated fuel. However, the characterizing methods to discriminate natural graphite, artificial graphite and resin carbon are rare. In this study, Raman Imaging and Scanning Electron (RISE) microscopy was used to study the structure and distribution of natural graphite, artificial graphite, resin carbon and graphite oxides produced from electrochemical deconsolidation of MG in post-irradiation examination (PIE). Natural graphite and artificial graphite have only a couple of Raman-active bands visible in the spectra between 1100-2400 cm-1, including the strong G band at ~1580 cm-1 and the weak D band at ~1350 cm-1. The D band is activated once the defects are introduced into sp2 hybridized carbon networks, and the intensity of D band is proportional to the defect concentration. Resin carbon has a strong D band, which can be easily distinguished from natural graphite and artificial graphite. The results show that the resin carbon is evenly coated on the surface of the natural and artificial graphite particles, and the network frame is formed during the pressing process to fix the graphite particles. This work also revealed that the changes of surface morphologies of MG after electrochemical deconsolidation by In-situ SEM analysis, of which a lot of cracks and holes on the surface of MG. Meanwhile, Raman spectra suggest that crystalline graphite and resin carbon have different oxidation behaviors. This work will provide a new method for MG components discriminating.
Ti3SiC2-TiC-Si Antioxidant Coating Prepared on SiC coated MG Spheres of HTR Fuel Element by Molten Salt Technique
Authors: Yang H , Zhao H , Liu X , Zhang K , Wang T , Li Z , Gao Y , Liu Bing
Published: October 2021

A Ti3SiC2-TiC-Si composite coating was prepared by molten salt technique on the surface of SiC coated matrix graphite (MG) spheres of HTR fuel element with different Ti content. The coating is composed of a transition layer, a SiC layer and an outer Ti- rich layer. When the content of Ti is 0.6g, the coating consists of Ti3SiC2, SiC, and TiC; when Ti content are 1.2g and 2.4g, the coating is composed of Ti3SiC2, SiC, TiC, and Si. Oxidation tests show that the kinetics of oxidation is parabolic at the beginning of oxidation; then it becomes linear after oxidation for 5h. The coating prepared with 0.6g Ti shows the best oxidation resistance, and the weight reduction of the coated MG spheres is only 0.33% after oxidation in static air at 1773K for 50h. These results show that Ti-based composites coating a kind of anti-oxidation coating system worth studying.
Drop analysis of Active Magnetic Bearing with rolling-sliding integrated auxiliary bearing
Authors: Wang Mingqi , Liu Xingnan , Zhao Yulan , Yang Guojun , Chen Jianqiang , Shi Zhengang
Published: October 2021

The Active Magnetic Bearing (AMB) technology is introduced in the High Temperature Reactor-Pebble-bed Modules (HTR-PM) demonstration nuclear power plant, which is being constructed in Shandong province, China. The auxiliary bearing is one of the most important components guaranteeing the reliability of the AMB. It also has an important impact on the reliability of the whole reactor system. Compared with the traditional auxiliary bearing, a novel one proposed by the authors has a smaller impact force and the rotor center orbit is much more concentrated during the rotor drop. This paper establishes an analytical model of drop of rolling-sliding integrated auxiliary bearing to analyze the above phenomena. Based on the Hertz contact theory, the complex structure inside the rolling bearing is simplified through a spring damping model. The overall impact model of the rolling-sliding integrated auxiliary bearing is established. Then, according to the structural characteristics of the rolling-sliding integrated auxiliary bearing, the tangential force inside the rolling- sliding integrated auxiliary bearing can be obtained by applying the angular momentum theorem. Finally, a four-degree-of-freedom horizontal rotor drop model is established to analyze and calculate the center orbit and motion state of the rotor. The analytical model is helpful in the selection and design of auxiliary bearing for AMB. In further research this contact model can be used to calculate the center orbit and contact forces in the application of the rolling-sliding integrated auxiliary bearing.
HTR-10 OTTO Cycle Depletion Simulation Using Discrete Element Method Coupled Monte Carlo
Authors: Putra F
Published: October 2021

Pebble bed reactor core contains 27,000 pebbles placed in a random position. Since the pebble insertion relies on gravity, the pebble placement pattern is irregular. Discrete Element Method used to simulate the pebble interaction and pebble movement during HTR-10 operation. Even though pebbles distributed randomly, the random generation of pebble positions used in most research does not mimic the actual pebble position and pebble surface contact. The Discrete Element Method provides a realistic interpretation of the pebble position by considering the pebble surface contact and gravity force. Each pebble coordinates from the Discrete Element Method obtained to construct Monte Carlo geometry of the HTR-10 core realistically. By coupling the DEM simulation with Monte Carlo simulation, it is possible to calculate the depletion while considering the core dynamic characteristic. The OTTO recirculation depletion calculation scheme with steady 10MW power for 368 days was constructed and demonstrated in this work. The DEM coupled Monte Carlo method allow one to track and predict each depleted fuel composition. Although the flux distribution change is slight in every timestep, the relation between flux and depleted U235 and Xe135 composition deserves to be taken into account. The calculation model in this work is comparable with the other calculation, but the timestep adjustment is needed to provide more accurate and representative results. Flux calculation and depletion simulation performed using the OpenMC program with ENDF/B-VIII.0 cross-section data. Please refer to digital version to view graph.
Preliminary Study on HTR-10 Operating in Higher Outlet Temperature
Authors: Zheng Yanhua , Xia Bing , Chen Zhipeng , Zhang Han , Sun Jun
Published: October 2021

High Temperature Gas-cooled Reactor (HTGR), which has well-known safety features and high temperature heat supply capability, is expected to be widely used for heat supply and technology heat utilization including the hydrogen production, and so contributing to the reduction of carbon dioxide emissions in various sectors. The 10 MW High Temperature gas-cooled test Reactor (HTR-10) had been constructed and operated in China as a pilot plant to demonstrate the inherent safety features of the modular HTGR. The first criticality of HTR-10 at air condition was realized on December 1, 2000, and the full power operation for 72 h on January 29, 2003. Supported by Chinese National S&T Major Project, HTGR for hydrogen production are now being studied. The physical and thermal hydraulic design to raise the outlet helium temperature of the HTR-10 reactor core from 700 °C to 850~1000 °C is carried out. In this paper, the preliminary thermal hydraulic design of the HTR- 10 with the outlet helium temperature of 950 °C (HTR-10H) is introduced. The power density distribution, the fuel temperature distribution and the reactor pressure vessel (RPV) temperature are studied to identify what need to be focused on next. Besides, the typical DLOFC accident has been studied to evaluate the safety feature of the HTR-10 operating under higher core temperature and outlet temperature. The preliminary results show that, operated at the higher outlet helium temperature, the original acceptance criteria for HTR-10 will be challenged. In the future, the design optimization, as well as the possible modification of these acceptance criteria, which were set more than two decades ago, should be studied based on the current knowledge of the fuel element properties and structure material properties.
Experimental Study on the Residual Heat Removal System in HTR-10
Authors: Li Jing , Wei Liqiang , Zheng Yanhua , Ma Tao , Chen Xiaoming , Xie Feng , Wang Haitao
Published: October 2021

The 10MW high temperature gas-cooled reactor (HTR-10) is a modular pebble-bed type reactor, of which the inlet and outlet helium temperature are 250 and 700 °C, respectively. It reached to its first criticality in December, 2000, and operated for nearly twenty years successfully. Currently, HTR-10 is the only pebble-bed type high temperature gas-cooled reactor that can operate in the world. To verify the natural circulation operating characteristics and safety features of the passive residual heat removal system, a series of experimental studies have been performed under different operation conditions of HTR-10, which include the performance tests of the passive residual heat removal system under various reactor operating power, different ambient temperature and single loop run mode. According to the data collation and result analysis, it shows that the performance of the residual heat removal system in HTR-10 meets the design and safety requirements.
MUF Calculation of Indonesian 10-MWt RDE Experimental HTGR Using Combined Uncertainty Approach
Authors: Adhi Arief S. , Husein Mohamad S.F. , Winastri Pertiwi D.
Published: October 2021

A safeguards assessment for the 10-MWt RDE Experimental HTGR needs to be established in order to fulfill the requirements needed to construct it. Methods and instruments used for the RDE’s nuclear material accounting and safeguards system are reviewed in this paper. Material unaccounted for (MUF) is calculated using the uncertainty of each method and instrument. The effectiveness of the safeguards system is examined by comparing the resulting MUF with the number of SQ ( = significant quantity, i.e. the approximate amount of nuclear material for which the possibility of manufacturing of a nuclear explosive device cannot be excluded). The total uncertainty from each KMP showed a number less than 10%. The number of MUF in each KMP according to total uncertainty showed a number below 1 kg of U-235 in one inventory period (~12 months). According to the number of MUF counted, it is impossible to reach 1 SQ if the diversion done is only by taking the advantage of MUF in the measurement. The result of total uncertainty and MUF calculation showed that the safeguards system and the material measurement designed for RDE is amendable. The sets of instruments and measurements designed will give a comprehensive data of each nuclear material in the RDE. The low number of MUF in comparison with the SQ showed that the RDE has a high proliferation resistance.
Chinese Math Word Problems Generation Network
Authors: Huang Junjian , Xu Ming , Zheng Hengyi , Shang Qian
Published: October 2021

Aiming at the feature vector bottleneck problem and the high time cost of the training process in the automatic generation of Chinese math word problems under the end-to-end architecture, we proposed an automatic generation method of Chinese math word problems based on the pre-training model combined with the integration of encoder and decoder. We used a deep neural network to model the mathematical equation sequence and Chinese keyword information, and used the stepped attention matrix to generate word problems. For training and testing on the Ape210K data set, compared with the end-to-end method, the Rouge-1 and Rouge-L evaluation indicators in our method was increased by 14.1% and 12.5%, as well as the training time cost was reduced by nearly 50%.
Intelligent Question Answering System Based on Machine Reading Comprehension
Authors: Shang Qian , Xu Ming , Qin Bin , Lei Pengbin , Huang Junjian
Published: October 2021

Question answering(Q&A) system is important for accelerating the landing of artificial intelligence. This paper makes an improvement on the Q&A system which uses the method of retrieval-machine reading comprehension (MRC). In the retrieval phase, we use BM25 to recall some documents and split these documents into paragraphs, then we reorder the paragraphs according to the correlation with the question, so as to reduce the number of recalled paragraphs and improve the speed of MRC. In the MRC stage, we design a multi-task MRC structure, which can judge whether the paragraph contains answer and locate answer accurately. Besides, we modify the loss function to fit the sparse labels during the training. The experiments are carried out on multiple data sets to verify the effectiveness of the improved system.
Self-Amplificated Network: Learning fine-grained learner with few samples
Authors: Dai Xili , Ma Chunmei , Sun Jingwei , Zhang Tao , Gong Haigang , Liu Ming
Published: October 2021

Training deep neural networks from only a few examples has been an interesting topic that motivated few shot learning. In this paper, we study the fine-grained image classification problem in a challenging few-shot learning setting, and propose the Self-Amplificated Network (SAN), a method based on meta-learning to tackle this problem. The SAN model consists of three parts, which are the Encoder, Amplification and Similarity Modules. The Encoder Module encodes a fine-grained image input into a feature vector. The Amplification Module is used to amplify subtle differences between fine-grained images based on the self attention mechanism which is composed of multi-head attention. The Similarity Module measures how similar the query image and the support set are in order to determine the classification result. In-depth experiments on three benchmark datasets have showcased that our network achieves superior performance over the competing baselines.
Deep Reinforcement Learning for Stock Recommendation
Authors: Shen Yifei , Liu Tian , Liu Wenke , Xu Ruiqing , Li Zhuo , Wang Jia
Published: October 2021

Recommending stocks is very important for investment companies and investors. However, without enough analysts, no stock selection strategy can capture the dynamics of all S&P 500 stocks. Nevertheless, most existing recommending strategies are based on predictive models to buy and hold stocks with high return potential. But these strategies fail to recommend stocks from different industrial sectors to reduce risks. In this article, we propose a novel solution that recommends a stock portfolio with reinforcement learning from the S&P 500 index. Our basic idea is to construct a stock relation graph (RG) which provide rich relations among stocks and industrial sectors, to generate diversified recommendation result. To this end, we design a new method to explore high-quality stocks from the constructed relation graph with reinforcement learning. Specifically, the reinforcement learning agent jumps from each industrial sector to select stock based on the feedback signals from the market. Finally, we apply portfolio allocation methods (i.e., mean-variance and minimum-variance) to test the validity of the recommendation. The empirical results show that the performance of portfolio allocation based on the selected stocks is better than the long-term strategy on the S&P 500 Index in terms of cumulative returns.