The electrochemical oxidation of biomass-derived platform molecule 5-hydroxymethylfurfural(HMF)represents a crucial pathway for green transformation into high-value chemicals,yet its reaction pathway selectivity,effic...The electrochemical oxidation of biomass-derived platform molecule 5-hydroxymethylfurfural(HMF)represents a crucial pathway for green transformation into high-value chemicals,yet its reaction pathway selectivity,efficiency,and catalyst stability are strongly dependent on the electrolyte pH environment.Under alkaline conditions,high OH−concentration facilitates preferential aldehyde group oxidation and efficient deprotonation,enabling highly efficient synthesis of 2,5-furandicarboxylic acid,but simultaneously induces HMF self-degradation and complicates product separation.As pH decreases,the reaction mechanism shifts toward enhanced hydroxymethyl oxidation,leading to intermediate accumulation(such as 5-hydroxymethyl-2-furancarboxylic acid,2,5-diformylfuran,and 5-formyl-2-furancarboxylic acid)with challenging selectivity control and significantly slowed reaction kinetics.This review comprehensively examines the systematic differences in HMF oxidation pathways and surface catalytic mechanisms across the full pH range from alkaline to acidic conditions.Addressing the distinct reaction characteristics and core challenges in alkaline,near-neutral,and acidic media,we systematically evaluate design strategies for high-efficiency electrocatalysts and explore reactor design aspects.Future research should focus on process integration(with tailored reactor design)for energy consumption reduction in alkaline systems,targeted synthesis of diverse oxidation products in near-neutral systems,and innovative catalyst development for acidic systems,thereby advancing the efficiency,selectivity,and practical application of HMF electrooxidation technologies across the entire pH spectrum through synergistic optimization of catalyst,reactor,and process.展开更多
Nuclear reactor coolant pumps require frequent maintenance to ensure operational safety.One critical aspect of this maintenance is verifying the integrity of the mechanical sealing system.Due to the lack of an evaluat...Nuclear reactor coolant pumps require frequent maintenance to ensure operational safety.One critical aspect of this maintenance is verifying the integrity of the mechanical sealing system.Due to the lack of an evaluation criteria and an incomplete understanding of how end-face defects lead to failure,defective mechanical seals are often replaced empirically,which not only contributes to economic losses but also poses risks to reactor safety.To reveal the mechanism by which surface defects affect sealing performance,this study proposes a classification method for end-face defects based on the analysis of approximately one hundred used mechanical seals.A defect characterization model was established by extracting key features of the observed defects.The influence of these defects on sealing performance was analyzed using a liquid-thermal-solid coupling model.Changes in sealing gap,leakage rates,and film stiffness with respect to defect size,location,and other characteristics are discussed.This work contributes to a deeper understanding of defect failure mechanisms.These results can serve as a reference for evaluating defective seals.展开更多
The synthesis of propylene carbonate(PC)from CO_(2) and propylene oxide(PO)is a typical gas-liquid biphasic system,where gas-liquid mass transfer efficiency significantly influences CO_(2) cycloaddition reactions.Here...The synthesis of propylene carbonate(PC)from CO_(2) and propylene oxide(PO)is a typical gas-liquid biphasic system,where gas-liquid mass transfer efficiency significantly influences CO_(2) cycloaddition reactions.Here,we proposed a microchannel reaction system for the CO_(2) cycloaddition reaction catalyzed by ionic liquid within an aqueous environment.The effect of liquid flow rate,temperature and residence time on gas-liquid flow pattern,catalytic performance and mass transfer were systematically investigated.The results revealed that the PC generation rate reached 560.11 mmol·ml^(−1)·h^(−1)at a 50 cm of flow distance under reaction conditions of 105℃,2.5 MPa,QG=176 ml·min^(−1) and QL=0.3 ml·min^(−1).Variations in mass transfer rate and reaction rate at different flow distances were experimentally studied.The reaction efficiency gradually decreased with increasing flow distance,which were attributed to the reduction of mass transfer caused by decreasing bubble velocity.Optimizing bubble velocity at an appropriate position enhanced reaction efficiency by improving mass transfer,achieving a 97.7%PC yield within 2.85 min.Furthermore,a kinetic model coupling intrinsic kinetics with gas-liquid mass transfer was developed for CO_(2) cycloaddition reaction.The kinetic model was applied to predict PC reaction rates in microchannel reactors at various temperatures and liquid flow rates,achieving an average relative error of 9.6%.展开更多
Laser-induced aerosols,predominantly submicron in size,pose significant environmental and health risks during the decommissioning of nuclear reactors.This study experimentally investigated the removal of laser-generat...Laser-induced aerosols,predominantly submicron in size,pose significant environmental and health risks during the decommissioning of nuclear reactors.This study experimentally investigated the removal of laser-generated aerosol particles using a water spray system integrated with an innovative system for pre-injecting electrically charged mist in our facility.To simulate aerosol generation in reactor decommissioning,a high-power laser was used to irradiate various materials(including stainless steel,carbon steel,and concrete),generating aerosol particles that were agglomerated with injected water mist and subsequently scavenged by water spray.Experimental results demonstrate enhanced aerosol removal via aerosol-mist agglomeration,with charged mist significantly improving particle capture by increasing wettability and size.The average improvements for the stainless steel,carbon steel,and concrete were 40%,44%,and 21%,respectively.The results of experiments using charged mist with different polarities(both positive and negative)and different surface coatings reveal that the dominant polarity of aerosols varies with the irradiated materials,influenced by their crystal structure and electron emission properties.Notably,surface coatings such as ZrO_(2)and CeO_(2)were found to possibly alter aerosol charging characteristics,thereby affecting aerosol removal efficiency with charged mist configurations.The innovative aerosol-mist agglomeration approach shows promise in mitigating radiation exposure,ensuring environmental safety,and reducing contaminated water during reactor dismantling.This study contributes critical knowledge for the development of advanced aerosol management strategies for nuclear reactor decommissioning.The understanding obtained in this work is also expected to be useful for various environmental and chemical engineering applications such as gas decontamination,air purification,and pollution control.展开更多
One of the main issues in designing optimum tapered cascades for uranium enrichment for annual fuel production in a power reactor is whether to employ large(fat)or small(thin)cascades.What will be the permissible and ...One of the main issues in designing optimum tapered cascades for uranium enrichment for annual fuel production in a power reactor is whether to employ large(fat)or small(thin)cascades.What will be the permissible and optimal ranges of the number of machines that can be used in a cascade?For the first time,the permissible and optimal ranges of the number of gas centrifuges that can be utilized in a cascade were investigated using two types of centrifuges,and the performance of small and large tapered cascades was discussed.The particle swarm optimization algorithm(PSO)has been used to optimize tapered cascades.The results show:(1)For the first centrifuge,41 cascades(91≤n≤4897)and for the second centrifuge,49 cascades(18≤n≤3839)with small and large sizes can be used in enrichment facilities,and the best cascade for them has 530(with 23 stages)and 39(with 7 stages)centrifuges,respectively.(2)For both centrifuges,when 600≤n(number of centrifuges=n),the large cascade performance changes are relatively insignificant.(3)For both types of gas centrifuges,the annual los s of separation power in enrichment facilities is approximately 1.25%-4.82%of the total separation work required.展开更多
Medical isotopes are the foundation material for nuclear medicine and are primarily produced through in-reactor irradia-tion.Neutron spectrum regulation is the main technical approach for enhancing the production of m...Medical isotopes are the foundation material for nuclear medicine and are primarily produced through in-reactor irradia-tion.Neutron spectrum regulation is the main technical approach for enhancing the production of medical isotopes,and it requires determining the optimal neutron spectrum and quantifying the values of neutrons in different energy regions.We calculated the neutron energy region values for 20 medical isotopes(^(14)C,^(32)P,^(47)Sc,^(60)Co,^(64)Cu,^(67)Cu,^(89)Sr,^(90)Y,^(99)Mo,^(125)I,^(131)I,^(153)Sm,^(161)Tb,^(166)Ho,^(177)Lu,^(186)Re,^(188)Re,^(92)Ir,^(225)Ac,and ^(252)Cf).The entire energy range was divided into 238 energy regions to improve the energy spectrum resolution,and both fast and thermal reactors were simulated to enhance universal applicability.A dataset of neutron energy region values across the entire energy range was built,which identifies the positive and negative-energy regions and guides the neutron spectrum regulation process during in-reactor medical isotope produc-tion.We conducted neutron spectrum regulation based on this dataset,which effectively improved the production efficiency of medical isotopes and demonstrated the correctness and feasibility of the dataset.展开更多
Core power is a key parameter of nuclear reactor.Traditionally,the proportional-integralderivative(PID)controllers are used to control the core power.Fractional-order PID(FOPID)controller represents the cutting edge i...Core power is a key parameter of nuclear reactor.Traditionally,the proportional-integralderivative(PID)controllers are used to control the core power.Fractional-order PID(FOPID)controller represents the cutting edge in core power control research.In comparing with the integer-order models,fractional-order models describe the variation of core power more accurately,thus provide a comprehensive and realistic depiction for the power and state changes of reactor core.However,current fractional-order controllers cannot adjust their parameters dynamically to response the environmental changes or demands.In this paper,we aim at the stable control and dynamic responsiveness of core power.Based on the strong selflearning ability of artificial neural network(ANN),we propose a composite controller combining the ANN and FOPID controller.The FOPID controller is firstly designed and a back propagation neural network(BPNN)is then utilized to optimize the parameters of FOPID.It is shown by simulation that the composite controller enables the real-time parameter tuning via ANN and retains the advantage of FOPID controller.展开更多
A radical C−C-coupling reaction of acetonitrile into succinonitrile over hydrophobic TiO_(2) photocatalyst with enhanced catalytic activity was developed.In addition,the usage of a flow reactor further improved the ph...A radical C−C-coupling reaction of acetonitrile into succinonitrile over hydrophobic TiO_(2) photocatalyst with enhanced catalytic activity was developed.In addition,the usage of a flow reactor further improved the photon utilization efficiency for succinonitrile synthesis at room temperature.The space time yield of succinonitrile reached 55.59μmol/(g·h)over hydrophobic TiO_(2) catalyst,which was much higher than that of pristine TiO_(2)(4.23μmol/(g·h)).Mechanistic studies revealed that the hydrophobic modification of TiO_(2) promoted the separation and transfer of photogenerated carriers,as well as suppressed their recombination.Hydrophobic TiO_(2) also enhanced the adsorption of−CH3 of acetonitrile,thus facilitating the activation of C−H bond and the utilization efficiency of photocarriers.展开更多
Based on the service characteristics of fuel elements for molten salt reactors,they need to have a high power density,resistance to coolant infiltration,and excellent thermodynamic properties.To solve the problem of t...Based on the service characteristics of fuel elements for molten salt reactors,they need to have a high power density,resistance to coolant infiltration,and excellent thermodynamic properties.To solve the problem of the graphite used in the fuel element for these reactors being susceptible to molten salt infiltration,carbon black(CB)was added to increase the density of the graphite,and a fuel element(TRISO(tri-structural isotropic)fuel particles were randomly distributed in the modified graphite matrix)was prepared by cold isostatic pressing process.An out-of-pile performance study shows that the densification and pore structure of the modified graphite matrix were improved,as was the resistance to molten salt infiltration.The median pore size of the modified graphite was reduced from 673 to 433 nm and the threshold pressure for molten salt(FLiBe,66%(molar fraction)LiF and 34%BeF_(2))infiltration was increased from 0.88 to 1.37 MPa.The isotropic CB made the graphite matrix less anisotropic,while its thermal conductivity and compressive strength were reduced due to the difficult graphitization of CB.Fuel elements containing 20%(volume fraction)TRISO particles were prepared.Numerical simulations show that the power and temperature distribution of the fuel were in line with the design requirements.The modified graphite matrix had a higher density,smaller pores,a lower anisotropy and a greater resistance to FLiBe infiltration.展开更多
Liquid-fueled molten-salt reactors have dynamic features that distinguish them from solid-fueled reactors,such that conventional system-analysis codes are not directly applicable.In this study,a coupled dynamic model ...Liquid-fueled molten-salt reactors have dynamic features that distinguish them from solid-fueled reactors,such that conventional system-analysis codes are not directly applicable.In this study,a coupled dynamic model of the Molten-Salt Reactor Experiment(MSRE)is developed.The coupled model includes the neutronics and single-phase thermal-hydraulics modeling of the reactor and validated xenon-transport modeling from previous studies.The coupled dynamic model is validated against the frequency-response and transient-response data from the MSRE.The validated model is then applied to study the effects of xenon and void transport on the dynamic behaviors of the reactor.Plant responses during the unique initiating events such as off-gas system blockages and loss of circulating voids are investigated.展开更多
Paired electrosynthesis has received considerable attention as a consequence of simultaneously synthesizing target products at both cathode and anode,whereas the related synthetic efficiency in batch reactors is still...Paired electrosynthesis has received considerable attention as a consequence of simultaneously synthesizing target products at both cathode and anode,whereas the related synthetic efficiency in batch reactors is still undesirable under certain circumstances.Encouragingly,laminar microfluidic reactor offers prospective options that possess controllable flow characteristics such as enhanced mass transport,precise laminar flow control and the ability to expand production scale progressively.In this comprehensive review,the underlying fundamentals of the paired electrosynthesis are initially summarized,followed by categorizing the paired electrosynthesis including parallel paired electrosynthesis,divergent paired electrosynthesis,convergent paired electrosynthesis,sequential paired electrosynthesis and linear paired electrosynthesis.Thereafter,a holistic overview of microfluidic reactor equipment,integral fundamentals and research methodology as well as channel extension and scale-up strategies is proposed.The established fundamentals and evaluated metrics further inspired the applications of microfluidic reactors in paired electrosynthesis.This work stimulated the overwhelming investigation of mechanism discovery,material screening strategies,and device assemblies.展开更多
This study discusses the scope of application of the Doppler backscattering(DBS)diagnostic for the tokamak with reactor technologies(TRT)project.This involved numerical modeling of the three-dimensional(3D)beam trajec...This study discusses the scope of application of the Doppler backscattering(DBS)diagnostic for the tokamak with reactor technologies(TRT)project.This involved numerical modeling of the three-dimensional(3D)beam trajectories.Calculations were performed to investigate the propagation of microwaves in the V(40–75 GHz)and W(75–110 GHz)frequency ranges with O-mode polarization for the density profile of the base TRT scenario.Our analysis showed that the DBS system antenna on the TRT would need to be tilted in both the poloidal and toroidal directions in order to meet the condition Kperp/Kpar<10%..For the DBS system located in the equatorial plane it was shown that a wide range of poloidal and toroidal angles is available for the successful implementation of the diagnostic to study the core,pedestal and scrape-off layer(SOL)regions.The DBS system located at 35 cm above the equatorial plane would be more limited in measurements only covering the SOL and pedestal regions.A shift of the cut-offs in the toroidal direction highlighted the need for 3D analysis of the DBS data.展开更多
Owing to high thermal stability and large reaction enthalpy,Mg H_(2) has high reaction temperatures and sluggish reaction kinetics in the dehydrogenation process,which consumes lots of energy.To achieve hydrogen relea...Owing to high thermal stability and large reaction enthalpy,Mg H_(2) has high reaction temperatures and sluggish reaction kinetics in the dehydrogenation process,which consumes lots of energy.To achieve hydrogen release with low energy consumption,accelerated reaction rate,and high heating uniformity,this paper proposes a novel method of graphite responsive microwave-assisted thermal management with NaTiO_(x)H catalyst.A multi-physics model of the 5 wt%NaTiO_(x)H catalyzed Mg H_(2) reactor integrated with a microwave generator is developed to investigate the reaction,heat and mass transfer process of hydrogen release.It is found that the graphite responsive microwave heating method could improve the temperature uniformity of reaction bed,reduce the energy consumption by at least 10.71%and save the hydrogen release time by 53.49% compared with the traditional electric heating method.Moreover,the hydrogen desorption thermodynamics could be improved with the increase of microwave power.The hydrogen release time is shortened by 19.55%with the increase of 20 W microwave power.Meanwhile,it is also concluded that the microwave excitation frequency of 2.1 GHz and the graphite content of 2 wt%have better heating performance.Therefore,it can be verified that the graphite responsive microwave heating helps to low-energy and accelerated hydrogen release from MgH_(2) hydrogen storage reactor.展开更多
High flux reactors(HFRs)are a special type of research reactor aimed at providing a high neutron flux.Compared with power reactors and other research reactors,HFRs have unique technical features in terms of reactor co...High flux reactors(HFRs)are a special type of research reactor aimed at providing a high neutron flux.Compared with power reactors and other research reactors,HFRs have unique technical features in terms of reactor core design,irradiation capability,and operating characteristics.They can be applied to the irradiation tests of nuclear fuels and materials,radioisotope production,neutron science,and experiments.This paper reviews HFRs,including their development history,technical features,and application areas,as well as trends in the development of new and advanced HFRs.展开更多
Hydrogenation reactions,vital in chemical engineering,are hampered by limitations including catalyst recovery,mass transfer issues,and scalability.Catalytic membrane reactors offer a promising alternative by integrati...Hydrogenation reactions,vital in chemical engineering,are hampered by limitations including catalyst recovery,mass transfer issues,and scalability.Catalytic membrane reactors offer a promising alternative by integrating reaction and separation,boosting efficiency and simplifying catalyst handling.However,scaling these membranes to industrial levels while ensuring long-term stability and high efficiency remains a significant challenge.This study tackles this by developing and demonstrating a pilot-scale multi-channel ceramic catalytic membrane reactor system.This system,featuring three 19-channel ceramic catalytic membranes,achieved nearly 100%p-nitrophenol hydrogenation conversion consistently over 600 h of continuous liquid-phase operation.This underscores the superior catalytic efficiency,remarkable long-term stability,and strong scalability of multi-channel ceramic catalytic membrane.This work establishes a robust platform for continuous-flow hydrogenation,providing a solid foundation for practical catalytic membrane reactor technology application in the chemical industry.展开更多
It has been widely recognized that the mixing process has significant impacts on the performance of low-density polyethylene(LDPE)reactors due to the rapid radical polymerization occurred in the reactors,but how the m...It has been widely recognized that the mixing process has significant impacts on the performance of low-density polyethylene(LDPE)reactors due to the rapid radical polymerization occurred in the reactors,but how the macro-and micro-mixing affect the reactor performance was still controversial in publications.In this work,a cold-flow LDPE autoclave with multi-feedings was scaled down(1/2)from an industrial reactor and built to systematically investigate the macro-and micro-mixing characteristics of fluid by experiments.Furthermore,the effects of macro-and micro-mixing on the polymerization were comprehensively analyzed.The results showed that according to the delay time t_(d) and macro-mixing times tM calculated from residence time distribution(RTD)curves,the macro-mixing states are significantly different at various axial positions(h/H),especially at lower agitation Reynolds number Re.But with the increase of Re,since the circulation flow in the reactor is strengthened,the t_(d) for each feed gradually decreases to 0,and the t_(M) at different axial positions tend to be identical.For micro-mixing,the qualities of micro-mixing at different axial positions are similar,and the average micro-mixing time t_(m) in the reactor decreases exponentially with the increase of Re.Moreover,a fitting model was established.Through the comparison of the characteristic times of macro-mixing(t_(d),t_(M)),micro-mixing(t_(m))and elementary reactions within the industrial range of Re,it can be concluded that the properties of LDPE products are dominated by the macro-mixing behavior,and the consumption of initiators is affected by both the macro-and micro-mixing behaviors.This conclusion is of great significance for the design,optimization and operation of LDPE reactors.展开更多
Under the dual-carbon background,the technological updating of traditional high-energy-consuming equipment should not be delayed,and the problem of reactor energy consumption should not be ignored.Therefore,this study...Under the dual-carbon background,the technological updating of traditional high-energy-consuming equipment should not be delayed,and the problem of reactor energy consumption should not be ignored.Therefore,this study is based on computational fluid dynamics(CFD)theory to simulate the spiral stirred reactor with different design parameters(distance of paddle from bottom surface to reactor height ratio h1/H,diameter of stirring paddle to reactor diameter ratio Ds/D,length of blade section to reactor height ratio Ls/H).It was found that the reactor designed with lower Ls/H values and higher h1/H,Ds/D values would have smaller power number(Np)values and smaller flow field average velocity.In addition,this study also fitted the correlation equation of Np concerning Reynolds number and h1/H,Ds/D,and Ls/H,and the conclusions of the study can be used as a reference for the design of industrial equipment.展开更多
基金supported by the National Key R&D Program of China(2023YFA1507400)the National Natural Science Foundation of China(Grant No.22325805,22441010,22408203)+2 种基金Beijing Natural Science Foundation(Grant No.JQ22003)the Haihe Laboratory of Sustainable Chemical Transformations(24HHWCSS00007)Tsinghua University Dushi Program,and Sinopec Group(PR20232572).
文摘The electrochemical oxidation of biomass-derived platform molecule 5-hydroxymethylfurfural(HMF)represents a crucial pathway for green transformation into high-value chemicals,yet its reaction pathway selectivity,efficiency,and catalyst stability are strongly dependent on the electrolyte pH environment.Under alkaline conditions,high OH−concentration facilitates preferential aldehyde group oxidation and efficient deprotonation,enabling highly efficient synthesis of 2,5-furandicarboxylic acid,but simultaneously induces HMF self-degradation and complicates product separation.As pH decreases,the reaction mechanism shifts toward enhanced hydroxymethyl oxidation,leading to intermediate accumulation(such as 5-hydroxymethyl-2-furancarboxylic acid,2,5-diformylfuran,and 5-formyl-2-furancarboxylic acid)with challenging selectivity control and significantly slowed reaction kinetics.This review comprehensively examines the systematic differences in HMF oxidation pathways and surface catalytic mechanisms across the full pH range from alkaline to acidic conditions.Addressing the distinct reaction characteristics and core challenges in alkaline,near-neutral,and acidic media,we systematically evaluate design strategies for high-efficiency electrocatalysts and explore reactor design aspects.Future research should focus on process integration(with tailored reactor design)for energy consumption reduction in alkaline systems,targeted synthesis of diverse oxidation products in near-neutral systems,and innovative catalyst development for acidic systems,thereby advancing the efficiency,selectivity,and practical application of HMF electrooxidation technologies across the entire pH spectrum through synergistic optimization of catalyst,reactor,and process.
基金Supported by National Natural Science Foundation of China(Grant No.51975315)National Science and Technology Major Project of China(Grant No.2019-IV-0020-0088).
文摘Nuclear reactor coolant pumps require frequent maintenance to ensure operational safety.One critical aspect of this maintenance is verifying the integrity of the mechanical sealing system.Due to the lack of an evaluation criteria and an incomplete understanding of how end-face defects lead to failure,defective mechanical seals are often replaced empirically,which not only contributes to economic losses but also poses risks to reactor safety.To reveal the mechanism by which surface defects affect sealing performance,this study proposes a classification method for end-face defects based on the analysis of approximately one hundred used mechanical seals.A defect characterization model was established by extracting key features of the observed defects.The influence of these defects on sealing performance was analyzed using a liquid-thermal-solid coupling model.Changes in sealing gap,leakage rates,and film stiffness with respect to defect size,location,and other characteristics are discussed.This work contributes to a deeper understanding of defect failure mechanisms.These results can serve as a reference for evaluating defective seals.
基金supported by the National Key Projects for Fundamental Research and development of China(2020YFA0710202)the China Postdoctoral Science Foundation(2024M761567)Shandong Postdoctoral Science Foundation(SDCX-ZG-202400271).
文摘The synthesis of propylene carbonate(PC)from CO_(2) and propylene oxide(PO)is a typical gas-liquid biphasic system,where gas-liquid mass transfer efficiency significantly influences CO_(2) cycloaddition reactions.Here,we proposed a microchannel reaction system for the CO_(2) cycloaddition reaction catalyzed by ionic liquid within an aqueous environment.The effect of liquid flow rate,temperature and residence time on gas-liquid flow pattern,catalytic performance and mass transfer were systematically investigated.The results revealed that the PC generation rate reached 560.11 mmol·ml^(−1)·h^(−1)at a 50 cm of flow distance under reaction conditions of 105℃,2.5 MPa,QG=176 ml·min^(−1) and QL=0.3 ml·min^(−1).Variations in mass transfer rate and reaction rate at different flow distances were experimentally studied.The reaction efficiency gradually decreased with increasing flow distance,which were attributed to the reduction of mass transfer caused by decreasing bubble velocity.Optimizing bubble velocity at an appropriate position enhanced reaction efficiency by improving mass transfer,achieving a 97.7%PC yield within 2.85 min.Furthermore,a kinetic model coupling intrinsic kinetics with gas-liquid mass transfer was developed for CO_(2) cycloaddition reaction.The kinetic model was applied to predict PC reaction rates in microchannel reactors at various temperatures and liquid flow rates,achieving an average relative error of 9.6%.
基金financial support from the Nuclear Energy Science&Technology and Human Resource Development Project of the Japan Atomic Energy Agency/Collaborative Laboratories for Advanced Decommissioning Science(No.R04I034)The author Ruicong Xu appreciates the scholarship(financial support)from the China Scholarship Council(CSC,No.202106380073).
文摘Laser-induced aerosols,predominantly submicron in size,pose significant environmental and health risks during the decommissioning of nuclear reactors.This study experimentally investigated the removal of laser-generated aerosol particles using a water spray system integrated with an innovative system for pre-injecting electrically charged mist in our facility.To simulate aerosol generation in reactor decommissioning,a high-power laser was used to irradiate various materials(including stainless steel,carbon steel,and concrete),generating aerosol particles that were agglomerated with injected water mist and subsequently scavenged by water spray.Experimental results demonstrate enhanced aerosol removal via aerosol-mist agglomeration,with charged mist significantly improving particle capture by increasing wettability and size.The average improvements for the stainless steel,carbon steel,and concrete were 40%,44%,and 21%,respectively.The results of experiments using charged mist with different polarities(both positive and negative)and different surface coatings reveal that the dominant polarity of aerosols varies with the irradiated materials,influenced by their crystal structure and electron emission properties.Notably,surface coatings such as ZrO_(2)and CeO_(2)were found to possibly alter aerosol charging characteristics,thereby affecting aerosol removal efficiency with charged mist configurations.The innovative aerosol-mist agglomeration approach shows promise in mitigating radiation exposure,ensuring environmental safety,and reducing contaminated water during reactor dismantling.This study contributes critical knowledge for the development of advanced aerosol management strategies for nuclear reactor decommissioning.The understanding obtained in this work is also expected to be useful for various environmental and chemical engineering applications such as gas decontamination,air purification,and pollution control.
文摘One of the main issues in designing optimum tapered cascades for uranium enrichment for annual fuel production in a power reactor is whether to employ large(fat)or small(thin)cascades.What will be the permissible and optimal ranges of the number of machines that can be used in a cascade?For the first time,the permissible and optimal ranges of the number of gas centrifuges that can be utilized in a cascade were investigated using two types of centrifuges,and the performance of small and large tapered cascades was discussed.The particle swarm optimization algorithm(PSO)has been used to optimize tapered cascades.The results show:(1)For the first centrifuge,41 cascades(91≤n≤4897)and for the second centrifuge,49 cascades(18≤n≤3839)with small and large sizes can be used in enrichment facilities,and the best cascade for them has 530(with 23 stages)and 39(with 7 stages)centrifuges,respectively.(2)For both centrifuges,when 600≤n(number of centrifuges=n),the large cascade performance changes are relatively insignificant.(3)For both types of gas centrifuges,the annual los s of separation power in enrichment facilities is approximately 1.25%-4.82%of the total separation work required.
基金sponsored by the National Natural Science Foundation of China(No.12305190)Lingchuang Research Project of China National Nuclear Corporation(CNNC).
文摘Medical isotopes are the foundation material for nuclear medicine and are primarily produced through in-reactor irradia-tion.Neutron spectrum regulation is the main technical approach for enhancing the production of medical isotopes,and it requires determining the optimal neutron spectrum and quantifying the values of neutrons in different energy regions.We calculated the neutron energy region values for 20 medical isotopes(^(14)C,^(32)P,^(47)Sc,^(60)Co,^(64)Cu,^(67)Cu,^(89)Sr,^(90)Y,^(99)Mo,^(125)I,^(131)I,^(153)Sm,^(161)Tb,^(166)Ho,^(177)Lu,^(186)Re,^(188)Re,^(92)Ir,^(225)Ac,and ^(252)Cf).The entire energy range was divided into 238 energy regions to improve the energy spectrum resolution,and both fast and thermal reactors were simulated to enhance universal applicability.A dataset of neutron energy region values across the entire energy range was built,which identifies the positive and negative-energy regions and guides the neutron spectrum regulation process during in-reactor medical isotope produc-tion.We conducted neutron spectrum regulation based on this dataset,which effectively improved the production efficiency of medical isotopes and demonstrated the correctness and feasibility of the dataset.
文摘Core power is a key parameter of nuclear reactor.Traditionally,the proportional-integralderivative(PID)controllers are used to control the core power.Fractional-order PID(FOPID)controller represents the cutting edge in core power control research.In comparing with the integer-order models,fractional-order models describe the variation of core power more accurately,thus provide a comprehensive and realistic depiction for the power and state changes of reactor core.However,current fractional-order controllers cannot adjust their parameters dynamically to response the environmental changes or demands.In this paper,we aim at the stable control and dynamic responsiveness of core power.Based on the strong selflearning ability of artificial neural network(ANN),we propose a composite controller combining the ANN and FOPID controller.The FOPID controller is firstly designed and a back propagation neural network(BPNN)is then utilized to optimize the parameters of FOPID.It is shown by simulation that the composite controller enables the real-time parameter tuning via ANN and retains the advantage of FOPID controller.
基金supported by the National Key R&D Program of China(2021YFF0500703)Natural Science Foundation of Shanghai(22JC1404200)+3 种基金Program of Shanghai Academic/Technology Research Leader(20XD1404000)Natural Science Foundation of China(U22B20136,22293023)Science and Technology Major Project of Inner Mongolia(2021ZD0042)the Youth Innovation Promotion Association of CAS。
文摘A radical C−C-coupling reaction of acetonitrile into succinonitrile over hydrophobic TiO_(2) photocatalyst with enhanced catalytic activity was developed.In addition,the usage of a flow reactor further improved the photon utilization efficiency for succinonitrile synthesis at room temperature.The space time yield of succinonitrile reached 55.59μmol/(g·h)over hydrophobic TiO_(2) catalyst,which was much higher than that of pristine TiO_(2)(4.23μmol/(g·h)).Mechanistic studies revealed that the hydrophobic modification of TiO_(2) promoted the separation and transfer of photogenerated carriers,as well as suppressed their recombination.Hydrophobic TiO_(2) also enhanced the adsorption of−CH3 of acetonitrile,thus facilitating the activation of C−H bond and the utilization efficiency of photocarriers.
文摘Based on the service characteristics of fuel elements for molten salt reactors,they need to have a high power density,resistance to coolant infiltration,and excellent thermodynamic properties.To solve the problem of the graphite used in the fuel element for these reactors being susceptible to molten salt infiltration,carbon black(CB)was added to increase the density of the graphite,and a fuel element(TRISO(tri-structural isotropic)fuel particles were randomly distributed in the modified graphite matrix)was prepared by cold isostatic pressing process.An out-of-pile performance study shows that the densification and pore structure of the modified graphite matrix were improved,as was the resistance to molten salt infiltration.The median pore size of the modified graphite was reduced from 673 to 433 nm and the threshold pressure for molten salt(FLiBe,66%(molar fraction)LiF and 34%BeF_(2))infiltration was increased from 0.88 to 1.37 MPa.The isotropic CB made the graphite matrix less anisotropic,while its thermal conductivity and compressive strength were reduced due to the difficult graphitization of CB.Fuel elements containing 20%(volume fraction)TRISO particles were prepared.Numerical simulations show that the power and temperature distribution of the fuel were in line with the design requirements.The modified graphite matrix had a higher density,smaller pores,a lower anisotropy and a greater resistance to FLiBe infiltration.
基金partly supported by the University of Shanghai for Science and Technology(No.10-24-301-101)。
文摘Liquid-fueled molten-salt reactors have dynamic features that distinguish them from solid-fueled reactors,such that conventional system-analysis codes are not directly applicable.In this study,a coupled dynamic model of the Molten-Salt Reactor Experiment(MSRE)is developed.The coupled model includes the neutronics and single-phase thermal-hydraulics modeling of the reactor and validated xenon-transport modeling from previous studies.The coupled dynamic model is validated against the frequency-response and transient-response data from the MSRE.The validated model is then applied to study the effects of xenon and void transport on the dynamic behaviors of the reactor.Plant responses during the unique initiating events such as off-gas system blockages and loss of circulating voids are investigated.
基金supported by the National Natural Science Foundation of China(22178361,22378402,52302310)the International Partnership Project of CAS(039GJHZ2022029GC)+5 种基金the National Key R&D Program of China(2020YFA0710200)the foundation of the Innovation Academy for Green Manufacture Institute,Chinese Academy of Sciences(IAGM2022D07)the China Postdoctoral Science Foundation(2022M722597)QinChuangYuan Cites High-level Innovation and Entrepreneurship Talent Programs(QCYRCXM-2022-335)the Fundamental Research Funds for the Central Universities(G2022KY05111)the Open Project Program of Anhui Province International Research Center on Advanced Building Materials(JZCL2303KF)。
文摘Paired electrosynthesis has received considerable attention as a consequence of simultaneously synthesizing target products at both cathode and anode,whereas the related synthetic efficiency in batch reactors is still undesirable under certain circumstances.Encouragingly,laminar microfluidic reactor offers prospective options that possess controllable flow characteristics such as enhanced mass transport,precise laminar flow control and the ability to expand production scale progressively.In this comprehensive review,the underlying fundamentals of the paired electrosynthesis are initially summarized,followed by categorizing the paired electrosynthesis including parallel paired electrosynthesis,divergent paired electrosynthesis,convergent paired electrosynthesis,sequential paired electrosynthesis and linear paired electrosynthesis.Thereafter,a holistic overview of microfluidic reactor equipment,integral fundamentals and research methodology as well as channel extension and scale-up strategies is proposed.The established fundamentals and evaluated metrics further inspired the applications of microfluidic reactors in paired electrosynthesis.This work stimulated the overwhelming investigation of mechanism discovery,material screening strategies,and device assemblies.
基金financial support of the Ministry of Science and Higher Education of the Russian Federation in the framework of the state contract in the field of science(No.FSEG-2024-0005)。
文摘This study discusses the scope of application of the Doppler backscattering(DBS)diagnostic for the tokamak with reactor technologies(TRT)project.This involved numerical modeling of the three-dimensional(3D)beam trajectories.Calculations were performed to investigate the propagation of microwaves in the V(40–75 GHz)and W(75–110 GHz)frequency ranges with O-mode polarization for the density profile of the base TRT scenario.Our analysis showed that the DBS system antenna on the TRT would need to be tilted in both the poloidal and toroidal directions in order to meet the condition Kperp/Kpar<10%..For the DBS system located in the equatorial plane it was shown that a wide range of poloidal and toroidal angles is available for the successful implementation of the diagnostic to study the core,pedestal and scrape-off layer(SOL)regions.The DBS system located at 35 cm above the equatorial plane would be more limited in measurements only covering the SOL and pedestal regions.A shift of the cut-offs in the toroidal direction highlighted the need for 3D analysis of the DBS data.
基金supported by the National Key R&D Program of China(2023YFB3809103)the National Natural Science Foundation of China(No.52176203)+2 种基金the Key R&D Project of Shaanxi Province,China(No.2023KXJ-283)the Key R&D Project of Shaanxi Province,China(No.2024CY2-GJHX-19)the“Young Talent Support Plan”of Xi’an Jiaotong University(No.QB-A-JZB2015004)。
文摘Owing to high thermal stability and large reaction enthalpy,Mg H_(2) has high reaction temperatures and sluggish reaction kinetics in the dehydrogenation process,which consumes lots of energy.To achieve hydrogen release with low energy consumption,accelerated reaction rate,and high heating uniformity,this paper proposes a novel method of graphite responsive microwave-assisted thermal management with NaTiO_(x)H catalyst.A multi-physics model of the 5 wt%NaTiO_(x)H catalyzed Mg H_(2) reactor integrated with a microwave generator is developed to investigate the reaction,heat and mass transfer process of hydrogen release.It is found that the graphite responsive microwave heating method could improve the temperature uniformity of reaction bed,reduce the energy consumption by at least 10.71%and save the hydrogen release time by 53.49% compared with the traditional electric heating method.Moreover,the hydrogen desorption thermodynamics could be improved with the increase of microwave power.The hydrogen release time is shortened by 19.55%with the increase of 20 W microwave power.Meanwhile,it is also concluded that the microwave excitation frequency of 2.1 GHz and the graphite content of 2 wt%have better heating performance.Therefore,it can be verified that the graphite responsive microwave heating helps to low-energy and accelerated hydrogen release from MgH_(2) hydrogen storage reactor.
文摘High flux reactors(HFRs)are a special type of research reactor aimed at providing a high neutron flux.Compared with power reactors and other research reactors,HFRs have unique technical features in terms of reactor core design,irradiation capability,and operating characteristics.They can be applied to the irradiation tests of nuclear fuels and materials,radioisotope production,neutron science,and experiments.This paper reviews HFRs,including their development history,technical features,and application areas,as well as trends in the development of new and advanced HFRs.
基金financial support from the National Key R&D Program(2022YFB3805504)the National Natural Science Foundation(U24A20536,U23A20117,22208149,22278209,22178165,21921006)the Natural Science Foundation of Jiangsu Province(BK20220354,BK20211262)of China.
文摘Hydrogenation reactions,vital in chemical engineering,are hampered by limitations including catalyst recovery,mass transfer issues,and scalability.Catalytic membrane reactors offer a promising alternative by integrating reaction and separation,boosting efficiency and simplifying catalyst handling.However,scaling these membranes to industrial levels while ensuring long-term stability and high efficiency remains a significant challenge.This study tackles this by developing and demonstrating a pilot-scale multi-channel ceramic catalytic membrane reactor system.This system,featuring three 19-channel ceramic catalytic membranes,achieved nearly 100%p-nitrophenol hydrogenation conversion consistently over 600 h of continuous liquid-phase operation.This underscores the superior catalytic efficiency,remarkable long-term stability,and strong scalability of multi-channel ceramic catalytic membrane.This work establishes a robust platform for continuous-flow hydrogenation,providing a solid foundation for practical catalytic membrane reactor technology application in the chemical industry.
基金the support and encouragement of the Key Projects of the Ministry of Industry and Information Technology of China(TC220A04W-3,188)。
文摘It has been widely recognized that the mixing process has significant impacts on the performance of low-density polyethylene(LDPE)reactors due to the rapid radical polymerization occurred in the reactors,but how the macro-and micro-mixing affect the reactor performance was still controversial in publications.In this work,a cold-flow LDPE autoclave with multi-feedings was scaled down(1/2)from an industrial reactor and built to systematically investigate the macro-and micro-mixing characteristics of fluid by experiments.Furthermore,the effects of macro-and micro-mixing on the polymerization were comprehensively analyzed.The results showed that according to the delay time t_(d) and macro-mixing times tM calculated from residence time distribution(RTD)curves,the macro-mixing states are significantly different at various axial positions(h/H),especially at lower agitation Reynolds number Re.But with the increase of Re,since the circulation flow in the reactor is strengthened,the t_(d) for each feed gradually decreases to 0,and the t_(M) at different axial positions tend to be identical.For micro-mixing,the qualities of micro-mixing at different axial positions are similar,and the average micro-mixing time t_(m) in the reactor decreases exponentially with the increase of Re.Moreover,a fitting model was established.Through the comparison of the characteristic times of macro-mixing(t_(d),t_(M)),micro-mixing(t_(m))and elementary reactions within the industrial range of Re,it can be concluded that the properties of LDPE products are dominated by the macro-mixing behavior,and the consumption of initiators is affected by both the macro-and micro-mixing behaviors.This conclusion is of great significance for the design,optimization and operation of LDPE reactors.
基金supported by the Natural Science Foundation of Shandong Province(ZR2023ZD22)the Major Research and Development Program of Shandong Province(2023CXGC010601).
文摘Under the dual-carbon background,the technological updating of traditional high-energy-consuming equipment should not be delayed,and the problem of reactor energy consumption should not be ignored.Therefore,this study is based on computational fluid dynamics(CFD)theory to simulate the spiral stirred reactor with different design parameters(distance of paddle from bottom surface to reactor height ratio h1/H,diameter of stirring paddle to reactor diameter ratio Ds/D,length of blade section to reactor height ratio Ls/H).It was found that the reactor designed with lower Ls/H values and higher h1/H,Ds/D values would have smaller power number(Np)values and smaller flow field average velocity.In addition,this study also fitted the correlation equation of Np concerning Reynolds number and h1/H,Ds/D,and Ls/H,and the conclusions of the study can be used as a reference for the design of industrial equipment.
