Large Size Reactor Research Articles

A Review on the Future of SMR Reactors in Nuclear Energy

The development of small modular reactors (SMRs) has emerged as a promising solution to provide clean, affordable, and reliable energy as global energy demand continues to rise. With a focus on different reactor types, their designs, and implementation strategies, this study offers a thorough overview of the state of SMR technology. This article evaluates the potential and challenges of small modular reactors concerning nuclear energy. It also thoroughly reviews the advantages and disadvantages of SMR technology, identifies regulatory barriers, public opinion, and infrastructure deficiencies, and investigates how SMRs might work with renewable energy sources to reduce greenhouse gas emissions. The SMR industry also emphasizes the significance of ongoing research and development. Adopting SMR reactors can be made easier with the support of advancements in design, technology, and regulatory frameworks. The integration of SMRs with renewable energy sources has the potential to provide a dependable, low-carbon, and sustainable energy solution. Advances in design, technology, and regulatory frameworks can facilitate the adoption of SMR. Annual operating and maintenance cost estimates can be affected by a wide range of additional factors, including the location of a plant, its capacity factor, regulatory considerations, plant obsolescence, and the number of reactors on the site. The difference in average cost ($/KWh) between SMR and Large-size reactors is about 20

Development of pressure-temperature limit curves considering unified constraint for reactor pressure vessel

In this work, the pressure-temperature (P-T) limit curves considering unified constraint for a typical large-sized reactor pressure vessel (RPV) with axial surface cracks have been investigated and developed based on the KJ-Ad* two-parameter and the Master Curve (MC) method. The ASME fracture toughness KIc curve and the MC with and without considering unified constraint for irradiated RPV steel were used in the constructions of the P-T limit curves. The effects of crack sizes (constraint levels) and fracture toughness curves on the P-T limit curves have been analyzed for the RPV under heatup and cooldown conditions. The results further show that the P-T limit curves based on traditional ASME KIc curve has the highest degree of conservatism and the use of the MC method can significantly increase the safety margin of P-T limit curves. With increasing crack sizes (increasing constraint levels), the safety region in P-T limit curves reduces, which may lead to the decrease of operating flexibility for nuclear power plants. The accuracy of the P-T limit curves can be improved by considering unified constraint. For smaller size cracks with lower constraint in the RPV, the consideration of constraint can reduce conservatism of the P-T limit curves, and for larger size cracks with higher constraint, it can avoid the non-conservatism. It is recommended to obtain more accurate P-T limit curves based on the MC with considering unified constraint and finite element analysis for RPVs under various operating conditions.

RF and microwave diagnostics for compact plasma traps and possible perspectives for fusion devices

Plasma diagnostics is a topic having a great impact on R&D in compact ion sources as well as in large fusion reactors. Towards this aim, non-invasive microwave diagnostics approaches, such as interferometric, polarimetric and microwave imaging profilometric techniques can allow obtaining volumetric, line-integrated or even space-resolved information about plasma electron density. Special probes can be also designed and implemented in order to characterize external and/or self-generated radio-waves in the plasmas. In particular, the design, construction and operation of a K-band microwave interferometry/polarimetry setup based on the Frequency-Modulated Continuous-Wave (FMCW) method at INFN-LNS will be described: this tool provides reliable measurements of the plasma density even in the extreme unfavorable wavelength-to-plasma scale ratio in plasma-based ion sources. A “frequency sweep” and a post-processing filtering method (for interferometry and polarimetry, respectively) were used to filter out the multipath contributions or cavity induced depolarizations in the detected signals. Besides this, the use of the aforementioned RF plasma-immersed probes will also be discussed, which allow measuring local E-fields and fast temporal response in order to characterize turbulent (through kinetic instabilities, cyclotron maser emission, etc.) vs. stable plasma regimes. An analysis based on wavelet transform applied to measurements of plasma radio self-emission in B-minimum and simple mirror traps will be presented. These tools and methods have the potential to be applied to plasma machines both in compact traps and large-size reactors with a proper scaling.

Modeling and comparative analysis of changeover of homogeneous and heterogeneous core of BN-1200 reactor to equilibrium mode

Equilibrium reactor core operating in closed fuel cycle with breeding ratio close to 1 is one of the key features of reactor designs developed within the framework of «Proryv» project direction (PD). Equilibrium reactor core is characterized by the stable reactivity and power density pattern, as well as isotopic composition of recycled plutonium. When putting into operation fast reactor using plutonium extracted from thermal reactor spent fuel in bicomponent nuclear power, the reactor core would operate rather long (more than 10 years) in transient mode, which requires special studies and special measures for controlling reactivity coast down during reactor run.Virtual-digital modeling of fast reactor (FR) fuel cycle closure is an efficient tool in such study. In this paper, RTM-2 code package option is outlined and used. This option includes updated fuel cycle model allowing to simulate heterogeneous core layout, as well as to use radial and axial blankets.Analytical studies have been made on sodium cooled large size reactor (1200 MW). Reactivity stabilization in such reactor is slightly more difficult as compared to lead cooled reactors, and excess reactivity exceeds βeff value attributed to BREST type reactors. Owing to heterogeneity of the core, the required excess reactivity can be decreased in transient mode down to βeff level. In equilibrium mode of such core, its breeding ratio (BR) is overrated, and this would even cause reactivity increase (although relatively small). Fuel breeding can be used for assurance of equilibrium mode with high fuel burnup.Basically, there is no need to use blankets in the core designs under consideration. However, one should not discount the demand for fuel breeding, which is also one of the potential advantages of fast reactors. Modeling has shown the possibility of adaptable variation of BR of BN-1200 M reactor within the range of values from 1.05 to about 1.4 with the use of additional blankets (axial and radial) and enriched N15.

Simulation of Methoxy methyl heptane (MMH) production using unisim design R460.1

Various fuel additives are employed till now like ethanol, ethyl tertiary butyl ether (ETBE), MTBE, Di Isopropyl alcohol (DIPA) etc. after the phase-out of lead-based compounds to enhance the octane number of fuel. MMH is suggested as an alternative to methyl tertiary butyl ether (MTBE) and similar ethers since they causes groundwater contamination. The liquid phase reversible reaction of methanol (MHOH) with 2-methyl1-heptene (MH) produces MMH. But there is an undesirable reaction also to form Dimethyl ether (DME) and 2-methyl-2-heptanol (MHOH). The process of MMH production is simulated using Unisim Design software R460.1. Conventionally, MMH is produced through a reactor and three distillation column sequences for yielding high purity MMH. This reactor-column sequence requires either high MH recycle or large-sized reactor to have the desired yield. Both results in large capital and operating costs. A reactive distillation concept can tackle these constraints with reactor and distillation in a single column known as reactive distillation column (RDC).The feasibility of RDC and analysis of the process can be observed using Unisim Design software since pilot plants are costly for this type of RD process. The simulation of the process using different test bed Unisim R460.1 is not explored yet.

Comparative analysis of the investment attractiveness of nuclear power plant concepts based on small and medium sized reactor modules and a large nuclear reactor

It seems to be of current interest to consider and analyse possible electrical and non-electrical applications of small and medium sized reactors for both the nearest and more distant future. The paper presents the results of a comparative analysis of the economic attractiveness of nuclear power plant (NPP) designs based on small and medium-sized reactor modules and a large-sized reactor in order to identify conditions for increasing the investment attractiveness of NPP modular design concept. The analysis is based on the evaluation of such economic performance metrics as net present value, present value, internal rate of return, discounted payback period, and levelized cost. It was shown that, in terms of the present value and levelized costs, the NPP modular design concept is less economically attractive in comparison with the NPP design based on a large-sized reactor. In terms of the net present value, internal rate of return and payback period, the NPP modular design concept can be considered economically attractive if only the predicted learning effect is observed when the modules are constructed and the scale factor is not less than 0.5. In this case, it will be economically feasible to construct an NPP based on a small number of medium sized reactor modules. If the scale factor is not less than 0.6, one may talk about the economic attractiveness of NPP designs based on reactor modules of lower power. The impact of various debt financing schemes was analysed and it was demonstrated that, in relative terms, changes in the economic performance indicators are comparable in the implementation of the NPP modular design and a large sized reactor.

High purity hydrogen production with a 10kWth RESC prototype system

The Reformer Steam Iron Cycle (RESC) is suitable to attain high-purity pressurized hydrogen from a broad range of renewables and residues in decentralized on-site applications. This paper introduces a 10 kWth lab prototype system for high purity hydrogen production exceeding 99.999%. The significantly enlarged reactor system comprises of a combined steam reformer and fixed bed chemical looping system within a single unit. A series of experiments was conducted to demonstrate the system applicability for decentralized hydrogen production with an improved process layout. A previously undiscovered hydrogen purity was realized from a fixed-bed chemical looping prototype system. Supplementary, the applied oxygen carrier material was characterized to reveal occurring degradation effects in large-size reactors as a significantly increased thermal stress. A characterization by SEM, EDX, light microscopy and BET methods was performed to exhibit the effects on the pelletised material.

Design of an Intensified Reactive Distillation Configuration for 2-Methoxy-2-methylheptane

The design of an intensified reactive distillation (RD) configuration for the production of 2-methoxy-2-methylheptane (MMH) was proposed. Conventionally, a high yield of MMH can be achieved by a large-sized reactor or by recycling 2-methyl-1-heptene (MH). Both strategies are associated with high capital and operating costs. This study proposed an innovative RD configuration that allows the production of MMH with significantly lower energy costs and total annual costs (TACs). The results demonstrate that the proposed RD configuration can reduce energy demands and total annual costs by up to 18.2, and 10.8%, respectively, compared to those for a conventional reactor column sequence for the desired MMH yield. In addition, different heat integration sequences were investigated to utilize the sensible heat to save energy and the subsequent TAC. One heat integration sequence for the proposed configuration further realized savings in energy and TAC by up to 36.7 and 21.8%, respectively.

Mass Synthesis in Polyol of Tailored Zinc Oxide Nanoparticles for Photovoltaic Applications

Zinc oxide nanoparticles with different sizes and shapes have been synthesized in polyol using a bottom-up approach. We have studied the scale-up of the process to massively produce high quality nanoparticles of controlled size and shape. The scale-up strategy required the effective mixing of reagents using either axial or radial mixing configurations and was experimentally validated by comparing structural properties of particles obtained in a small and a large size reactor. In addition, the flow patterns in these reactors have been calculated using three-dimensional turbulent computational fluid dynamics (CFD) simulations. Our results indicate a strong connection between the flow patterns, as obtained by CFD simulations, and the size and shape of the particles. Actually, our pilot scale reactor allowed producing sample aliquots of ~50 grams with nanoparticle sizes ranging from 8 nm to 600 nm and aspect ratio varying from 1 (nanospheres) to 20 (nanorods). After their synthesis, these two nanoparticle classes have been tested as building blocks in D149-dye-sensitized solar cell (DSSC). The measured power conversion efficiency (PCE) was 4.66% for nanorods shaped particles and 4.21% for nanospheres. These values were significantly higher than the 3.90% PCE obtained with commercial Degussa VP20 ZnO nanoparticles.

Numerical Analysis for the Growth of Epitaxy Layer in a Large-Size MOCVD Reactor

A modified large-size MOCVD reactor is developed to produce uniform and large-volume epitaxy thin film layer of gallium nitride (GaN). The full governing equations for continuity, momentum, energy and chemical species are solved numerically. It is investigated how thermal flow field, and the operating parameters affect molar concentration of each reactant, and the thin film uniformity. These parameters are involved such as the chamber pressure (100-700 torr), susceptor rotation rate (100-800). In this paper, the simulation results from these listed parameters shows that an optimum epitaxy layer can be achieved in the large-size reactor.

Economic features of integral, modular, small-to-medium size reactors

The renewed interest towards nuclear energy is largely based on the escalation of fossil fuels prices and the global warming concerns. The nuclear option has to face not only the public opinion sensibility, mainly related to plant safety and waste disposal issues, but also the economic evaluation from investors and utilities, particularly careful on that energy source and in deregulated markets. Smaller size nuclear reactors (IAEA defines as “small” those reactors with power<300 MWe and “medium” with power<700 MWe) can represent a viable solution for both the stakeholders, especially for developing countries, or countries with not-highly-infrastructured and interconnected grids, or even for developed countries when limitation on capital at risk applies. A description of Small-Medium size Reactor (SMR) economic features is presented, in a comparison with the state-of-the-art Large size Reactors. A preliminary evaluation of the capital and O&M costs shows that the negative effects of the economies of scale can be balanced by the integral and modular design strategy of SMRs.

Role of passive systems in advanced reactors

In this paper, the role of passive systems in advanced reactor designs has been discussed. With large scale deployment of nuclear power reactors in future, the safety requirements in terms of risk for these future reactors would be different and more stringent than the existing reactors. In fact, some of these reactors are proposed to be built inside a population zone without having an exclusion zone. To achieve the higher safety standards in terms of reduction of risk, passive systems could play an important role by eliminating the requirements of operators or external inputs for their operation. However, it may be difficult or impossible to incorporate passive systems extensively in large size reactors, but could be well fit into small and medium sized reactors. Passive systems have several issues including their reliability, which must be resolved before incorporation of them into advanced designs. These are discussed in this paper.

Anaerobic biogasification of undiluted dairy manure in leaching bed reactors

Dry anaerobic digestion of high solids animal manure is of increasing importance since conventional slurry digestion is not an effective system for these manures. The investment costs for large-size reactors, costs for heating these reactors, handling, dewatering, and the disposal of the digested residue decrease the benefits of conventional slurry anaerobic digestion for high solids animal manure. Even though leaching bed reactors (LBR) constitute a promising option for dry anaerobic biogasification of animal manure, no study is cited in the literature for animal manure, excluding a single study on cattle waste which utilized a similar concept in a different experimental set-up, namely a packed bed digester. Therefore, this work was undertaken to investigate the anaerobic biogasification of undiluted dairy manure in LBRs. To this purpose anaerobic leaching bed reactors (ALBR) packed with a mixture of dairy manure, anaerobic seed and wood powder/chips were operated. The ALBRs were fed with water, and the leachate that was collected from their effluents was subjected to biochemical methane potential (BMP) experiments to determine the biogas production. The results revealed that LBRs can successfully be applied to anaerobic digestion of undiluted dairy manure with around 25% improvement in biogas production relative to conventional (slurry) anaerobic digesters.

Prospects of nuclear desalination in Morocco

In the last few years, Morocco has faced a continuous series of dry seasons, which has put a great stress on its limited water resources. Hence, for some time now Morocco has been considering desalinating seawater to supply fresh water to some areas. In the early 1980's, due to limited energy resources, Morocco was obliged to consider other alternatives to meet its energy demands. A feasibility study for the introduction of a nuclear power plant into the national electrical grid was launched. Even though the study showed that the commercially proven, large size reactors could not be integrated into the grid due to their limited capacity, the national electrical utility continues to pursue its efforts to introduce nuclear energy into the country. Presently, the feasibility study is being updated and a bid invitation specification is being prepared with the help of the IAEA experts. In response to the increasing need for energy and water, Morocco and some North African countries participated in the IAEA regional project on the feasibility study on using nuclear energy for seawater desalination. Subsequently, Morocco carried out a feasibility study for the construction of a demonstration plant for seawater desalination using a 10 MW Nuclear Heating Reactor with China and IAEA. As part of its interest in nuclear energy, Morocco is setting up the nuclear infrastructure that could help in the implementation of the nuclear power programme. The construction of a nuclear research centre which is to be commissioned in a couple of years, and the establishment of the nuclear safety authority and the radiation protection authority are part of the programme.

生ごみの高温メタン発酵における負荷とアンモニア阻害の影響

Although the methane fermentation process requires less energy and the collected gas may be used as a fuel, the reaction speed is slow. It leads to the large size reactor and high cost. Therefore, to investigate the practicability and efficiency of the Methane Fermentation as the waste disposal system from the perspective of energy production, advancement of load and reduction of discharge, the thermophilic methane fermentation tests were carried out at the temperature of 55°C changing the loading rate from 2.28 kg-VS/m3/d to 9.90 kg-VS/m3/d continuously. The fermentation could be stable under the following condition, HRT: over 10 days, loading rate: under 9.29 kg-VS/m3/d, moisture percentage: over 90%, Nitrogen content: under 0.0020 kg-N/kg. In case of that the nitrogen concentration in the treated waste is higher, the dilution water is necessary to control the concentration of nitrogen. In the thermophilic methane fermentation, two times more additional water is necessary compared with the mesophilic methane fermentation. The obtained net energy was two times greater by the thermophilic methane fermentation than by the mesophilic methane fermentation in the condition that the additional water for the waste was unnecessary. On the other side, there was no great difference between thermophilic and mesophilic methane fermentation in the condition that the additional water was necessary.

VUV Characteristics of BaAl12O19:Mn2+ Phosphor Particles Prepared from Aluminum Polycation Solutions by Spray Pyrolysis.

AbstractFor Abstract see ChemInform Abstract in Full Text.

VUV characteristics of BaAl 12O 19:Mn 2+ phosphor particles prepared from aluminum polycation solutions by spray pyrolysis

High efficiency BaAl 12O 19:Mn 2+ phosphor particles with spherical shape and non-aggregation characteristics were prepared by large-scale spray pyrolysis from aluminum polycation precursor solutions. The phosphor particles prepared from nitrate precursors had a hollow and irregular structure under the preparation conditions of high concentration solution, high flow rate of carrier gas, and large size reactor. However, the BaAl 12O 19:Mn phosphor particles prepared from aluminum polycation precursor solution had completely spherical shape and filled morphology after post-treatment at 1400 °C. The as-prepared particles obtained from aluminum polycation precursor solution had spherical shape and dense structure under the severe preparation conditions by forming viscous gel precursors at the drying stage of the droplets. The mean size of the BaAl 12O 19:Mn phosphor particles increased from 1.2 to 2.7 μm when the concentration of the solution changed from 0.8 to 2 M. The prepared BaAl 12O 19:Mn phosphor particles had high luminescence intensities irrespective of the type of precursor solutions under vacuum ultraviolet. The maximum peaks of the prepared BaAl 12O 19:Mn and the commercial Zn 2SiO 4:Mn phosphor particles are located at 516 nm and 527 nm, respectively.

Gd2 O 3 : Eu Phosphor Particles Prepared from the Polymeric Precursors in Spray Pyrolysis

The phosphor particles with high brightness and spherical shape were prepared by spray pyrolysis from the polymeric precursor solutions. The particles prepared from the nitrate precursors had a hollow and irregular structure in the preparation conditions of high concentration, high flow rate of carrier gas, and large size reactor. However, the particles prepared from the polymeric precursor solutions obtained from citric acid and ethylene glycol had a spherical and filled morphology. The phosphor particles prepared from the polymeric precursors had the higher intensities than that of the particles prepared from the nitrate precursors. The maximum photoluminescent intensity of the particles prepared from the polymeric precursor solution was 146% of that of the particles prepared from the nitrate precursors. The photoluminescent intensity of the particles prepared from the polymeric precursor solutions was 120% of that of the commercial phosphor particles. © 2001 The Electrochemical Society. All rights reserved.

Theoretical Reactor Design from the Simple Tubular Reactor Analysis for Wsix CVD Process

ABSTRACTWe propose a methodology for systematic reactor design and optimization of operating conditions. The reactor can be designed systematically through the following steps: extraction of the chemistry from small-scale experiments, simulations for the virtual large-sized reactor configurations using the chemistry obtained from small-scale experiments, and final optimization by actual experiments on the real reactor manufactured according to the results of the simulation experiments. We call this technique ECONOMIX (Experiment, COmputer, kNOwledge MIXed CVD Process Design). The validity of this theoretical approach was confirmed for the WSix CVD process. The chemistry of the WSix CVD process was obtained from the tubular hot wall reactor. The rate constants of consecutive reaction were re-determined using two-dimensional simulation with consideration of temperature distribution. The growth rate and composition ratio were simulated for the cold wall reactor using reaction kinetics obtained by tubular hot wall reactor analysis. The predicted growth rates and composition ratios of Si/W showed good agreement with the experimental data. Therefore, the theoretical approach, ECONOMIX, is valid for the design of CVD reactor. We can design reactors and optimize operating conditions efficiently by this theoretical approach using computer simulation coupled with small-scale experiments.

Influence of the reactor design in the case of silicon nitride PECVD

Based on a chemical mechanism whose reliability has already been established in a previous paper, two-dimensional models for some normally employed reactors, namely, longitudinal flow, radial flow and showerhead reactors were developed in the case of silicon nitride plasma enhanced chemical vapor deposition (PECVD) from silane and ammonia mixtures. The aim of this study was to gain a new and global insight into the understanding of the overall behavior of PECVD reactors which can be useful for reactor developers and users. In this work, the reactor design and the flow distribution were shown to be determining parameters. Apart from some second-order differences, some general tendencies were brought to the fore and two groups of reactors were distinguished: the ‘localized injection reactors’ and the ‘distributed injection reactors’. In the case of the first type, the deposition rate and film composition undergo variations which can be strong, whereas in the other, the thickness uniformity and the composition uniformity of the layer are very satisfactory, even for large-size reactors. This last type of reactors was found to be all the more interesting as the film composition could be set by choosing appropriate operating conditions.