Reactor Structure Research Articles

A New Structure of a Gap-Reactor to Reduce Electromagnetic Vibrations

Magnetostriction is an inherent property of an electrical steel sheet (ESS). Experimental measurements have revealed that the magnetostrictions of Grain-oriented and Non-oriented ESSs are mostly opposite in their directions. Based on this, a novel structure of gap reactor is suggested to reduce the mechanical vibration of the reactor. The new structure follows the conventional manufacturing process, and is built by stacking Grain-oriented and Non-oriented cores alternately while a conventional one is by only Grain-oriented or Non-oriented core. In order to verify the effectiveness of the proposed structure, the electromagnetic vibration, stress and displacement of the reactor are analyzed based on the magneto-elastic coupled analysis. The measured magnetization and magnetostriction data of the ESSs are adopted during the numerical calculation. Prototypes of new and traditional structures with the same design parameters were also built and electromagnetic-induced vibration were measured and analyzed. Both the computational and experimental results showed that the proposed structure made much less electromagnetic vibration than the conventional one. Moreover, the noise level around the reactors were measured and the average noise level around the improved prototype was reduced by 16.7%.

Advances in efficient desalination technology of capacitive deionization for water recycling

Abstract Available freshwater resources are becoming harder to obtain due to climate change, population growth, industrial development, and water pollution. The main technologies in the field of wastewater desalination include reverse osmosis, electrodialysis, thermal distillation, and adsorption etc. Capacitive deionization technology (CDI) belongs to a novel electrochemical desalination technology with low energy consumption and low environmental impact, simple equipment structure and convenient operation. With the importance of wastewater desalination highlighted, some great technological progress of CDI has been made in electrode materials, reactor structure and the hybrid process. In this paper, the development of CDI technology was expounded from three aspects to achieve the goal of strong adaptability, low cost and strong adsorption capacity by analysis of the latest research papers. Corresponding improved methods of CDI are summarized to solve the main technology bottlenecks such as the inefficient and vulnerable electrode materials, low selectivity and unreasonable unit structure, and limitations of single CDI unit for promoting the continuous development of CDI technology.

Fatigue Reliability Analysis Method of Reactor Structure Considering Cumulative Effect of Irradiation

The influence of irradiation should be considered in fatigue reliability analyses of reactor structures under irradiation conditions. In this study, the effects of irradiation hardening and irradiation embrittlement on fatigue performance parameters were quantified and a fatigue life prediction model was developed. Based on this model, which takes into account the cumulative effect of a neutron dose, the total fatigue damage was calculated according to Miner’s linear cumulative damage law, and the reliability analysis was carried out using the Monte Carlo simulation method. The case results show that the fatigue life acquired by taking into account the cumulative effect of irradiation was reduced by 24.3% compared with that acquired without considering the irradiation effect. Irradiation led to the increase of the fatigue life at low strains and its decrease at high strains, which is in accordance with the findings of an irradiation fatigue test. The rate of increase in the fatigue life decreased gradually with the increase of the neutron dose. The irradiation performance parameters had a small influence on fatigue reliability, while the fatigue strength coefficient and the elastic modulus had a great influence on the fatigue reliability. Compared with the current method, which uses a high safety factor to determine design parameters, a fatigue reliability analysis method taking into account the cumulative effect of irradiation could be more accurate in the reliability analysis and life prediction of reactor structures.

Severe accident studies on the efficiency of mitigation devices in a SFR core with SIMMER code

Sodium-cooled Fast Reactors (SFR) are investigated as future Generation IV reactor concepts. In SFR, the core configuration is not the most reactive during the nominal reactor operation, its geometry change or coolant voiding can induce a reactivity insertion. Within these considerations, mitigation devices should be implemented into the core in order to limit the thermal energy released into the fuel during a severe accident and thereby the possibility to induce mechanical loadings of the reactor structure when vaporized materials expand. Complementary safety devices called Transfer Tubes (TT) are studied in a French concept as an effective mitigation measure of severe accidents to reach a final reactor safe state, even in case of a failure of all shutdown systems including the passive shutdown safety rods. More precisely the TT, with their upper part located in and above the core, cross the core support structure and are linked to the core catcher zone situated in the main vessel bottom. Their purpose is to extract fissile materials from the core zone and secondly to favor the transfer of the molten fuel from the core region to the core catcher in case of severe core damage. The fuel discharge out of the core zone is necessary in order to lower the core reactivity, the relocation into the core catcher is necessary to enable the stabilization, the sub-criticality and the fuel cooling. An extensive work on severe accident calculations and phenomena identification related to fuel discharge through TT was performed. These studies represent the outcome of the work performed in 2014–2019, performed with collaboration of Japanese JAEA and MFBR and Framatome in the framework of the SFR project carried out by CEA. Calculations of fuel discharge were carried out with the mechanistic calculation code SIMMER and the main results are presented in this paper. Firstly, the whole unprotected loss of flow (ULOF) accident sequence was calculated with the SIMMER code. From these calculations, the power and flow evolution were set as boundary conditions for a more detailed model with six fuel assemblies around TT. This model was used to focus on key phenomena and to check impact of design parameter as local bottom restriction inside TT on fuel discharge way.

Possibility of a Sonofusion Reactor – Nuclear Fusion induced by Cherenkov Radiation from the ZPF field in a Collapsing Water Bubble

Sonofusion, also known as bubble fusion, is the name for a nuclear fusion reaction hypothesized to occur during a high-pressure version of sonoluminescence. By applying this phenomenon, the researchers caused bubbles in the deuterated acetone liquid with oscillating sound waves to expand and then violently collapse for producing a flash and enormous heat that has the potential to fuse nuclei together. In this paper, the authors present the theoretical explanation of sonoluminescence, which accounts for the sonofusion induced by Cherenkov radiation which is generated from tachyon pairs created from ZPF field in a collapsing water bubble, and the possible structure of a sonofusion reactor.

WASTE CLASSIFICATION ASSESSMENT OF NUCLEAR STEELS FOR FUSION POWER APPLICATIONS

Fusion power is an attractive option for the world’s future energy needs. An important goal for fusion is to avoid the severe radioactive waste issues associated with nuclear fission. However, the neutrons produced in the fusion plasma reaction impinge on the surrounding reactor structure causing nuclear activation. It is hoped that activated material from fusion facilities can be disposed of as low level waste 50-100 years after operation ceases, but recent work suggests this may be difficult to achieve. This work presents inventory simulations for a number of potential fusion steels, for two neutron irradiation conditions typical of the DEMO reactor concept. The results are used to determine if the steels meet low level waste regulations, for a number of different international waste management systems. These results show that steels do not appear able to consistently meet low level waste requirements when exposed to near-plasma neutron fluxes. They have more success when exposed to lower fluxes, but traditional steels will still struggle to meet low level waste requirements in a fusion environment.

Numerical Simulation on Asymmetrical Three-Dimensional Thermal and Hydraulic Characteristics of the Primary Sodium Pool Under the Pump Stuck Accident in CEFR

The complex structure of a pool-type sodium-cooled fast reactor may lead to uncertainty and asymmetry of flow and temperature field distributions under a pump stuck accident. This phenomenon has obvious three-dimensional (3-D) thermal-hydraulic characteristics and cannot be analyzed by one-dimensional or two-dimensional models. Previous research has been limited and lacking of 3-D numerical data. Therefore, the commercial computational fluid dynamics software FLUENT is used to simulate a full-scale 3-D integrated model of the China Experimental Fast Reactor (CEFR) in order to obtain 3-D thermal-hydraulic characteristics of key structures and components in the pool-type sodium-cooled fast reactor under a pump stuck accident in the primary loop. The results show that a special asymmetrical backflow phenomenon may occur in the pressure tube and the intermediate heat exchangers (IHXs) of the failure loop under the accident, further leading to complicated flow and thermal characteristics in both the hot and the cold pools. There is obvious thermal stratification and asymmetric temperature distribution, within a temperature difference of more than 90°C between the different loops’ IHX outlet. The temperature difference between the upper and lower areas of the baffles is 20°C to 105°C. This research provides a detailed reference for engineering design and operation.

Extraction of tungsten from scheelite using hydrodynamic and acoustic cavitation

The primary purpose of this study is to investigate the effects of hydrodynamic and acoustic cavitation (HAC) on the leaching efficiency of tungsten. The aim is to reduce energy use and to improve the recovery rate. The goal is also to carry out a leaching process at a much lower temperature than in an autoclave process that is currently used in the industry. Energy-efficient initiation and collapse of cavitation bubbles require optimization of (i) vibro-acoustic response of the reactor structure, (ii) multiple excitation frequencies adapted to the optimized reactor geometry, and (iii) hydrodynamic cavitation with respect to orifice geometry and flow conditions. The objective is to modify and apply a previously in house developed high power cavitation reactor in order to recover tungsten by leaching of the dissolution of scheelite in sodium hydroxide. In this process, various experimental conditions like dual-frequency excitation, different orifice geometry have been investigated. The numerically optimized reactor concept was excited by two frequencies 23 kHz and 39–43 kHz in various flow conditions. The effects of leaching time, leaching temperature, ultrasonic power and geometry of orifice plates have been studied.The leaching temperature was varied from 40 °C to 80 °C. The concentration of leaching reagent sodium hydroxide (NaOH) was 10 mol/L.The results were compared to conventional chemical leaching. Energy supplement with acoustic cavitation of 130 kWh/kg concentrate resulted in a leaching recovery of tungsten (WO3) of 71.5%, compared to 36.7% obtained in absence of ultrasound. The results confirm that the method developed is energy efficient and gives a recovery rate potentially better than current autoclave technology.

Zn2+‐Doped PVA Composite Electrospun Nanofiber for Upgrading of Enzymatic Properties of Acetylcholinesterase**

AbstractEnzyme immobilization provides improve mechanical characteristic of enzymes and stability to environmental alters. It also helps to enzymes maintain their activities for a long time and offers the possibility to use them again. With these unique features, they can reduce production costs in industrial applications. In this study, acetylcholinesterase (AChE) immobilized on Zn2+‐doped PVA nanofibers via adsorption and cross‐linking methods. Morphological structures of Zn2+‐doped PVA nanofibers were characterized by Scanning Electron Microscopy (SEM) before and after immobilization. It was observed that the enzyme gained resistance against temperature and pH changes occurring in the reaction medium after immobilization process. In addition, immobilized Zn2+‐doped PVA nanofibers retained of its activity approximately 75 % after 8 reuse and its activity decreased below 50 % after 12 reuse. As a result, AChE immobilized Zn2+‐doped PVA nanofibers offers numerous advantages for various biotechnological applications, such as hydrolysis and determination of pesticides, use in the structure of reactors and electrodes, thanks to the unique stability and reusability features that AChE gains after immobilization.

Influence of inlet structures of planetary reactor on gas reaction path in AlN-MOVPE process

Numerical study on the influence of inlet structure of planetary reactor on gas reaction path and growth rate in AlN-MOVPE was investigated. It was found that, for the conventional two-inlet reactor (base reactor), the reaction is dominated by the adduct reaction path, and the growth rate is low but evenly distributed; for the inverted inlet reactor, i.e., group-III in lower inlet and group-V in upper inlet, the reaction is dominated by the pyrolysis path, and the growth rate is higher than the base reactor but the growth uniformity is decreased. By moving the position of the inlet separator closer to the ceiling for the inverted inlet, the growth uniformity is improved. When the number of reactor inlets increases from two inlets (base reactor) to three and five inlets, the growth rate increases, the growth uniformity improves, and the reaction changes from the adduct-dominated path to the pyrolysis and adduct coexisted path. Besides varying the inlet geometry, we also found that decreasing the NH3 flow rate will enhance the pyrolysis path and the growth rate for the above reactors.

Multi-objective topology optimization for the solar thermal decomposition of methane reactor enhancement

A multi-objective topology optimization method is proposed to generate local solid structure that can enhance the solar thermal decomposition of the methane (TDM) reactor. Two dominant factors can govern the performance of solar reactor, with heat transfer entropy generation and viscous dissipation representing heat exchange capability and flow resistance, respectively. Therefore, local solid structure and flow pattern can be generated under the compromise between the extreme value of the two factors. This multi-objective topology optimization problem is solved by the calculus of variations method and globally convergent version of the method of moving asymptotes (GCMMA) with the governing equations of the solar TDM reactor as constraints. A novel local structure of the solar TDM reactor is generated, which can improve the heat exchange effect and the conversion rate of the reaction.

Characteristic of methanol steam reforming in fan-shaped channel reactor for efficient hydrogen production

ABSTRACT On-board methanol steam reforming fan-shaped channel micro-reactor heated by engine exhaust (simulated by hot wind) for hydrogen production was designed and analyzed in this study. Effects of the reactor material and structural parameters were investigated. The optimal size of reactor structure, using the stainless steel as the reactor material, are predicted to be 26 mm and 35 mm for the hot wind side radius and total radius, respectively. Additionally, the optimal angle of the fan shaped reactor unit is 10°, while the thickness of the intermediate between the hot wind and reaction sides as well as side and top walls are 1 mm. Under these structure parameters, the methanol conversion rate is 73.48%, the engine exhaust heat efficiency is 36.50%, and the hydrogen production rate of the whole reactor is 78439.30 mm3/s. These results can be utilized as reference for the comprehensive utilization of engine exhaust heat and engine hydrogen-mixed combustion.

Study on the Effect of Structure Parameters on NO Oxidation in DBD Reactor under Oxygen-Enriched Condition

To improve NO oxidation and energy efficiency, the effect of dielectric barrier discharge reactor structure on NO oxidation was studied experimentally in simulated diesel exhaust at atmospheric pressure. The mixture of 15% O2/N2 (balance)/860 ppm NOX (92% NO + 8% NO2) was used as simulated diesel exhaust. The results show that DBD reactor with 100-mm electrode length has the highest oxidation degree of NOX and energy efficiency. NO oxidation efficiency is promoted and the generation of NO is inhibited significantly by increasing the inner electrode diameter. Increasing the inner electrode diameter not only improve the E/N, but also makes the distribution of E/N more concentrated in the gas gap. The secondary electron emission coefficient (γ) of electrode material is closely related to electron energy and cannot be considered as a constant, which causes the different performance of electrode material for NO oxidation under different gas gap conditions. Compared with the rod electrode, the screw electrode has a higher electric field strength near the top of the screw, which promotes the generation of N radicals and inhibits the generation of O radicals. Rod electrode has a higher NO oxidation and energy efficiency than screw electrode under oxygen-enriched condition.

Monolithically Integrated Diffused Silicon Two-Zone Heaters for Silicon-Pyrex Glass Microreactors for Production of Nanoparticles: Heat Exchange Aspects.

We present the design, simulation, fabrication and characterization of monolithically integrated high resistivity p-type boron-diffused silicon two-zone heaters in a model high temperature microreactor intended for nanoparticle fabrication. We used a finite element method for simulations of the heaters’ operation and performance. Our experimental model reactor structure consisted of a silicon wafer anodically bonded to a Pyrex glass wafer with an isotropically etched serpentine microchannels network. We fabricated two separate spiral heaters with different temperatures, mutually thermally isolated by barrier apertures etched throughout the silicon wafer. The heaters were characterized by electric measurements and by infrared thermal vision. The obtained results show that our proposed procedure for the heater fabrication is robust, stable and controllable, with a decreased sensitivity to random variations of fabrication process parameters. Compared to metallic or polysilicon heaters typically integrated into microreactors, our approach offers improved control over heater characteristics through adjustment of the Boron doping level and profile. Our microreactor is intended to produce titanium dioxide nanoparticles, but it could be also used to fabricate nanoparticles in different materials as well, with various parameters and geometries. Our method can be generally applied to other high-temperature microsystems.

Advance in Improving the Electrical Performance of Microbial Fuel Cell

As a bioelectrochemical hybrid system, microbial fuel cell converts chemical energy into electrical energy through microbial metabolism, which has great advantages of energy conservation and environmental protection, high energy conversion efficiency, and reduced sludge volume. Therefore, how to improve the power generation performance and output power of MFC has been a hot topic in recent years. Based on this, on the basis of reviewing many literatures, this review analyzes the main factors influencing the electrical performance of MFC by combining the principle of MFC and its electronic transfer mechanism, including battery reactor structure, exchange membrane, anode microorganisms, electrode materials and parameters, etc. At the same time, the application prospect of MFC is discussed, including CW-MFC coupling technology, biosensor and sewage treatment technology. Finally, the present challenges of MFC are put forward, and a better application research direction is proposed for the future of MFC.

Numerical-experimental evaluation of FRESNEL lens heating dynamics

Fresnel lenses allow the concentration of sunlight that can be employed in different thermal unitary operations or endothermic chemical transformations. A system with Fresnel lenses should also take into account vessel or reactor surface thermal losses (reflection, convection and emission), as well as the thermal energy required to keep the vessel or reactor structure warm. In this paper, a numerical and experimental analysis indicated that the solar radiation incident on the lens, the Fresnel lens area and the specimen mass can be represented by a grouping called Heating Factor (31 ≤ Ψ (W/kg) ≤ 3347). The Heating Factor (Ψ) was strongly correlated with the maximum temperature conductive specimens could reach when inserted at the focal point of a Fresnel Lens. Equilibrium Temperatures were predicted by a physical-mathematical model and validated by experimental tests. The Fresnel lens system has been shown to be able of providing Equilibrium Temperatures from 345 to 1600 K for specimens with Heating Times between 3 and 85 min and Initial Thermal Rates from 1.16 to 312.00 K/min. Numerical-experimental analyses also showed that the heating dynamic was strongly influenced by the nature of the materials that constituted the specimens (specific mass and the specific heat).

Continuous Generation of HgCl2 by DBD Nonthermal Plasma. Part I: Influences of the DBD Reactor Structure and Operational Parameters

Abstract-1 Accurate on-line measurement of mercury speciation is vital in the mercury emission control. Calibrator is an important part in the instrumentation system, which is responsible for the a...

Experimental studies on metallic fuel relocation in a pin bundle core structure of a sodium-cooled fast reactor

Understanding the relocation behavior of metallic fuel in severe accident scenarios is one of the most important factors in the safety assessment of sodium-cooled fast reactors (SFRs). In the present study, the relocation behavior of uranium metallic fuel was investigated by conducting metallic fuel relocation experiments using 19-pin bundle test sections in the Argonne’s Metallic Uranium Safety Experiment (MUSE) facility. Post-test radiographic images were taken to characterize the uranium fuel relocation within the pin bundle test section. In addition, the pressure drop in the test sections was measured after the relocation experiments to evaluate the blockage of the sodium coolant channel. The pressure drop in the pin bundle test sections was also analytically calculated by varying the porosity and the pore size of the relocated fuel. The porosity and pore size of the relocated fuel in the pin bundle test sections were estimated by comparing those calculated pressure drop values with the measured pressure drop values from the pressure drop tests. The experimental results showed that the more formation of the eutectics could lead to more fuel dispersion and less blockage due to the lower freezing point of the eutectics.

Effects of hydraulic retention time on the process performance and microbial community structure of an anaerobic single-stage semi-pilot scale reactor for the treatment of food waste

The performance of a single-stage semi-pilot scale reactor in anaerobically digesting food waste was examined and its microbial community composition investigated using high-throughput 16S rRNA gene sequencing. Highest biogas yield (1.01 L/g VSadded), highest removal efficiency for chemical oxygen demand (COD) (95.84%) and volatile solid (VS) (92.7%) were achieved during 124-day HRT. When the hydraulic retention time (HRT) reduced from 124 days to 62 days, ammonia and volatile fatty acids (VFA) concentration in the reactor gradually increased while pH, biogas yield, removal efficiency for VS and COD decreased gradually. This was likely due to the accumulation of volatile fatty acid (VFA), which resulted in scum accumulating in the reactor. The abundance of acid-producing bacteria resulted in the accumulation of VFA in the reactor, which is a critical factor that could explain process failure. Hydrogenotrophic methanogenesis was the main pathway for producing methane from hydrogen and carbon dioxide during the 124-day HRT. The decline in hydrogenotrophic methanogens at 62-day HRT inhibited the decomposition of VFA and accelerated the transfer of the amino acid degradation pathway, which further enhanced VFA accumulation. However, the dominant methanogens failed to degrade the excessive acetate at 41-day HRT. This metabolic discrepancy ultimately led to process deterioration.

Research on Improved Simplified SCWR Assembly and Core Design

Abstract A new type of simplified assembly without “water rod” or solid moderator is identified to simplify China Supercritical Water-cooled Reactor with the rated electric power of 1000 MWel (CSR1000) core structure. A study on the properties of this new assembly has been carried out. Under the condition of heat full power, maximum cladding surface temperature (MCST) is 658 °C, very close to safety criterion 650 °C, and maximum linear heat generation rate (MLHGR) is 40.0 kW/m, slightly higher than safety criterion 39 kW/m. Considering rod stuck criterion, the maximum keff is 0.9833, lower than safety criterion 0.99. The discharge burn-up reduced to 21368 MWd/t, a sharp decreasing of 31.1%. This simplified assembly provides a new idea for solving the problem of complex structure of supercritical water-cooled reactor (SCWR).