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Inverted fuel geometry implementation for a fast reactor: Potential improvements in neutronic and thermalhydraulic performance
No full textThis paper presents a detailed procedure for implementing the inverted fuel geometry to a fast reactor to improve its safety system and economy. The study is starting from the fuel unit cell, fuel assembly, reactor core, and burnup analysis. A proposed multivariable graph (v, Delta P, T-F(max)-D-co, V-F) introduced at the fuel unit cell level provides comprehensive thermalhydraulic and neutronic parameters in a single graph, allowing for an efficient optimization process. The fuel unit cell study reveals that the inverted fuel design has a higher fuel volume fraction and lower core pressure drop than conventional pin-typed fuel. This is beneficial for the reactor economy and enhances the reliability of the safety system. With the inverted fuel design, the primary loop can save pumping power by up to 40 % and provides an excess driving force for natural circulation. The male-female axial grid structure separating the fuel assembly potentially eliminates coolant flow path restriction and fretting issues. The core is named the Inverted Core Fast Reactor (IC-FR), an LBE-cooled fast SMR designed to generate 60 MWth for at least 40 years of full-power operation without refueling and fuel shuffling. IC-FR is a transportable reactor and has load following capability that can be deployed for many applications, including marine and land-based applications, and stand alone or mixing power grid. The burnup study of IC-FR reveals that the balance of neutron leakage and fissile inventory yields a small reactivity swing (<1$) for 40 years. This study extensively utilizes Monte Carlo (MC) code MCS for neutronic calculation. Owing to the high computational expense of MC code, the approaches to optimize the MC usage are also presented
The production scheduling problem employing non-identical parallel machines with due dates considering carbon emissions and multiple types of energy sources
No full textThis paper addresses the production scheduling problem with non-identical parallel machines in a high-mix, low-volume production environment with due dates, considering carbon emissions savings and diverse types of energy sources for machine operation. To this end, we present a bi-objective mixed-integer programming model that minimizes both the total production-related cost and the total carbon emissions in the production process to determine the optimal production strategy. For each machine, we consider various types of energy sources with different electricity generation costs and different amounts of carbon emissions. The proposed model is validated with an application to a manufacturer in Ulsan, the industrial capital of the Republic of Korea. Our results showcase the potential use of non-identical parallel machines to minimize the total cost and carbon emissions in green manufacturing. Furthermore, the results identify the trade-off between different energy sources and the total cost under different carbon emissions limits. Generally, as the carbon emissions limit increases, our proposed model tends to replace natural gas with coal to minimize the total cost. Also, we perform sensitivity analyses with respect to the energy price of different types of energy sources combined with nuclear and renewable energy sources. We find that coal provides more stability than natural gas in terms of the total cost, particularly when there are fluctuations in the price for coal and natural gas. Additionally, we determine the optimal combination of energy sources for various carbon emissions limits, aiming to minimize the total cost while simultaneously satisfying all production-related and environmental constraints
User Preferences of Privacy-Enhancing Attributes of a Smart Speaker
No full textSmart speakers become a versatile and convenient device to provide digital contents in our daily life. However, given the challenges of privacy management in smart speakers, it is required to examine how users cope with privacy threats of the devices. In this study, we examine how the privacy-enhancing attributes of smart speakers influence users' preferences when choosing devices. The preference structure was generated from a conjoint approach, dealing with four privacy-enhancing features (parasite function, data storage method, security notice, and speaker recognition function) and two typical factors affecting consumer decision making (brand and price). Data collected from a survey of 516 consumers identified that, aside from the attribute of price, parasite function was ranked as the most preferred attribute. We also compared the findings across three user clusters. By examining concrete and explicit attributes regarding privacy-enhancing features, the present study provides novel insights into users' understanding of privacy
Bacterial remediation of pesticide polluted soils: Exploring the feasibility of site restoration
No full textFor decades, reclamation of pesticide contaminated sites has been a challenging avenue. Due to increasing agricultural demand, the application of synthetic pesticides could not be controlled in its usage, and it has now adversely impacted the soil, water, and associated ecosystems posing adverse effects on human health. Agri-cultural soil and pesticide manufacturing sites, in particular, are one of the most contaminated due to direct exposure. Among various strategies for soil reclamation, ecofriendly microbial bioremediation suffers inherent challenges for large scale field application as interaction of microbes with the polluted soil varies greatly under climatic conditions. Methodically, starting from functional or genomic screening, enrichment isolation; func-tional pathway mapping, production of tensioactive metabolites for increasing the bioavailability and bio-accessibility, employing genetic engineering strategies for modifications in existing catabolic genes to enhance the degradation activity; each step-in degradation study has challenges and prospects which can be addressed for successful application. The present review critically examines the methodical challenges addressing the feasi-bility for restoring and reclaiming pesticide contaminated sites along with the ecotoxicological risk assessments. Overall, it highlights the need to fine-tune the available processes and employ interdisciplinary approaches to make microbe assisted bioremediation as the method of choice for reclamation of pesticide contaminated sites
Numerical simulation of ball milling reactor for novel ammonia synthesis under ambient conditions
No full textThe investigation models an alternative ammonia production method compared to the Haber-Bosch method. The operating parameters of proposed process, which successfully synthesized ammonia with competitive yield, were 45 degrees C and 1 bar, which is significantly lower than the Haber-Bosch process. A study was made on the impact and contact behavior of the planetary ball mill to understand the movement of steel balls and iron particles inside the reactor vessel to improve the synthesis process. The EDEM software, based on discrete element method (DEM), was used to understand the internal behavior of a planetary mill. Balls and particles were loaded at a ratio of 1:20, i.e., 500 g of steel ball diameter is 25 mm, and 24 g of iron particles diameter is 0.25 mm in reactor. Contact and energy released by balls and particles as a function of mill speed were compared with the experimental correlation of adsorbed nitrogen. The correlation with the experimental data showed satisfactory agreement with present numerical simulation. This work is the first step towards realistic scaling of the system and vertical mill is not a common practice on an industrial scale, this work will use experimental data to create and validate a vertical ball mill model
Direct conversion of furfural to 1,5-pentanediol over a nickel-cobalt oxide-alumina trimetallic catalyst
No full textThe use of a Ni-CoOx-Al2O3 mixed metal-metal oxide catalyst was proposed for the one-pot direct conversion of furfural (FFA) to 1,5-pentanediol (1,5-PDO), which afforded a high yield (47.5%) at 160 degrees C and at an initial H-2 pressure of 3 MPa for 6 h in ethanol. Proximity between the Ni-0 and oxygen-vacant CoOx (O-v-CoOx) sites favored the dissociative adsorption of H-2 molecules on Ni-0 and subsequent hydrogen spillover to O-v-CoOx. The hydrogenation of the CO group of FFA produced furfuryl alcohol, which was then adsorbed on the Co delta+ center of the O-v-CoOx site in a eta(1)-(O)-alcoholic configuration, where subsequent C-O bond cleavage produced 1,5-PDO. Catalytic activity loss through the oxidation of the Ni-0 and O-v sites could be mitigated by reactivation under H-2. Thus, the developed Ni-CoOx-Al2O3 catalyst has potential for efficient, low-cost, and environmentally friendly 1,5-PDO production from FFA
Radiological safety analysis of a newly designed spent resin mixture treatment facility during normal and abnormal operational scenarios for the safety of radiation workers
No full textThe radiological safety of workers in a newly developed microwave-based spent resin treatment facility was assessed based on work location and operational scenarios. The results show that the remote-operation room worker was exposed to maximum annual dose of 3.19E+00 mSv, which is 15.9% of the dose limit, thereby confirming radiological safety. Inside the pathway, annual doses in the range of 7.87E-02???2.07E-01 mSv were measured initially at the mock-up tank and later at the point between the spent resin separation and treatment parts. The dose of emergency maintenance workers was below the dose limit (4.08E-03???4.99E+00 mSv); however, before treatment (separation and microwave), the dose of maintenance and repair workers exceeded the dose limit. The doses of the effluent removal workers at the zeolite and activated carbon storage tank and spent resin storage tank were the lowest at 2.79E-01???2.87E-01 mSv and 9.27E-01 mSv in ???1 h??? and ???4???5 h of operation???, respectively. The immediately lower and upper layers of the facility room exhibited the highest annual doses of 1.84E+00 and 3.22E+00 mSv, respectively. Through this study, a scenario that can minimize the dose considering the movement of spent resin through the facility can be developed
New Ion Substitution Method to Enhance Electrochemical Reversibility of Co-Rich Layered Materials for Li-Ion Batteries
No full textThe recent development of high-energy LiCoO2 (LCO) and progress in the material recycling technology have brought Co-based materials under the limelight, although their capacity still suffers from structural instability at highly delithiated states. Thus, in this study, a secondary doping ion substitution method is proposed to improve the electrochemical reversibility of LCO materials for Li-ion batteries. To overcome the instability of LCO at highly delithiated states, Na ions are utilized as functional dopants to exert the pillar effect at the Li sites. In addition, Fe-ion substitution (secondary dopant) is performed to provide thermodynamically stable surroundings for the Na-ion doping. Density functional theory calculations reveal that the formation energy for the Na-doped LCO is significantly reduced in the presence of Fe ions. Na and Fe doping improve the capacity retention as well as the average voltage decay at a cutoff voltage of 4.5 V. Furthermore, structural analysis indicates that the improved cycling stability results from the suppressed irreversible phase transition in the Na- and Fe-doped LCO. This paper highlights the fabrication of high-energy Co-rich materials for high voltage operations, via a novel ion substitution method, indicating a new avenue for the manufacturing of layered cathode materials with a long cycle life
Synthesis of a halogenated low bandgap polymeric donor for semi-transparent and near-infrared organic solar cells
No full textSemi-transparent organic solar cells (ST-OSCs) have garnered significant interest because of their potential in aesthetic and space-saving solar energy systems such as multi-colored semitransparent building???integrated photovoltaic or grow light transparent agrivoltaic systems. As visibly semitransparent photoactive materials, the low bandgap (LBG) donor polymer and acceptor present new opportunities for the realization of ST-OSCs because they can facilitate photovoltaic generation of electricity from near-infrared (NIR) light without significant absorption of visible light. However, while various LBG non-fullerene acceptors have been recently developed to realize highly efficient ST-OSCs, there are only a few reports on LBG donor polymers that achieve efficient photo-induced charge generation from NIR light as well as allow the propagation of visible light. In this study, LBG donor polymers consisting of BD-F and BD-Cl as the halogenated derivatives of poly{2,6???-4,8-di(5-ethylhexylthienyl)benzo[1,2-b; 3,4-b]dithiophene-alt-5-dibutyloctyl-3,6-bis(5-bromothiophen-2-yl)pyrrolo[3,4-c]pyrrole-1,4-dione} (BD-H) were synthesized. The BD-F:Y6 and BD-Cl:Y6 OSCs showed higher open-circuit voltages and fill factors than BD-H:Y6 due to their downshifted energy level and efficient charge extraction characteristics. Consequently, the BD-Cl:Y6 OSCs achieved a power conversion efficiency (PCE) of 5.62%. Furthermore, with the introduction of a metal oxide/metal/metal oxide transparent electrode, the BD-Cl:Y6 ST-OSC demonstrated a high average visible transmittance of 35.1% and PCE of 3.69%. This approach contributes to enhancing the potential of ST-OSCs
A comparative study on binary polymer blends comprising rigid planar low-bandgap semiconductor and flexible coil-type insulator
No full textA polymer blend is an essential member of a class of materials analogous to metal alloys, in which two polymers are blended together to create a noble material with different physical properties. Not only the physicochemical properties of each polymer but also their relative interaction and miscibility are a key to eliciting novel materials properties. Here, we investigated the effects of blending a flexible coil-type insulating polymer on the charge transport characteristics of rigid planar semiconducting polymers. To this end, we systematically controlled the blending ratio of the commercial insulating polymer, polystyrene, and one of two different diketopyrrolopyrrole-based donor-acceptor alternating copolymers, and characterized the electrical, microstructural, and morpho-logical properties of the semiconductor-insulator polymer blend films. We found that the electrical properties of the films are strongly correlated with the polymer blend ratio and the resulting films' vertical segregation and crystalline structures and that hole transport and electron transport alter differently with the polymer backbone structure and blend ratio. These results are expected to be greatly helpful in optimizing the semi-conductor-insulator polymer ink formulations for potential use in printed electronics