•The ATF concept Cr-coated-Zr was assessed with a BWR MELCOR plant model.•The Cr-coated-Zr was applied to both cladding and canister.•The effect of Cr-Zr eutectic reaction was considered.•The use of ...Cr-coated-Zircaloy mitigates the core degradation process.•The gross in-vessel hydrogen generation decreased by almost a factor of three.
The deposition of protective coatings on nuclear fuel cladding has been considered as a near-term Accident Tolerant Fuel (ATF) concept that will reduce the high-temperature oxidation rate and enhance accident tolerance of the cladding while providing additional benefits during normal and transient. In this study, the performance of the proposed ATF concept of Cr-coated-Zircaloy is assessed using a generic Boiling Water Reactor MELCOR plant model considering a Short-term Station Blackout (STSBO) scenario. Simulation results indicate that the use of Cr-coated-Zircaloy as cladding and canister material mitigates the core degradation process as compared to the traditional Zircaloy cladding and canister design. The onset of fuel degradation and collapse is delayed by over thirty minutes, and the extent of fuel degradation is reduced. Specifically, the gross in-vessel hydrogen generation decreased by almost a factor of three. Although the eutectic reaction between Cr-coating and Zircaloy could cause an early failure of the coating, the improvement in the delay of fuel degradation is still notable. Additionally, a thicker coating is found helpful to obtain additional coping time and to decrease hydrogen generation. In addition to the eutectic formation that may compromise Cr-coated Zr, a different failure mode is identified for the Cr-coated-Zr when compared to Zircaloy; i.e., a complete melt of base material leads to component collapse before the coating is oxidized and consumed. These findings can help the industry focus on productive areas of research and development for accident-tolerant fuel concepts and enhancement of core safety margins.
•The Cl- ions in the solution promote the passive dissolution reaction process.•The dissolved surface in the chloride-containing solution is significantly flatter.•The transpassive dissolution rate ...and current efficiency are enhanced by Cl- ions.
The electrolyte solution significantly affects electrochemical machining. This study investigates the electrochemical dissolution behavior of a laser solid formed Hastelloy X nickel-based superalloy in 15 wt% NaNO3, 7.5 wt% NaNO3 + 7.5 wt% NaCl, and 15 wt% NaCl solutions. The Cl- ions in the electrolyte solution accelerates the passive dissolution rate because the electrochemical reactions at the metal/film and film/solution interfaces are promoted. During the transpassive dissolution process, the Cl- ions in the electrolyte solution weaken the hindering effect of the transpassive film on the dissolution process, resulting in a faster transpassive dissolution rate and a higher current efficiency. Furthermore, the flatness of the dissolved surface in the chloride-containing solution is significantly higher than that in the chloride-free solution. Two models are proposed to illustrate the passive and transpassive dissolution behaviors. This study provides theoretical guidance for the selection of electrolyte solutions for the electrochemical machining of laser solid formed nickel-based superalloys.
•This paper shows a broad comparison of flexible IDE RH sensors.•Three different electrode materials are studied: AgNPs ink, laser-induced graphene and laser-reduced graphene oxide.•The comparison is ...made in terms of sensitivity to humidity changes, linearity, thermal drift, losses and frequency response.•Feasibility of large-scale and cost-effective manufacturing.
This work presents a case-based comparison between two emerging fabrication techniques for the development of conductive patterns for flexible electronics: inkjet-printing and nanographene production by laser-scribing. In particular, these two methods are used to fabricate planar interdigitated electrode (IDE) capacitors with Kapton® HN polyimide as supporting flexible substrate. Silver-based electrodes are manufactured by inkjet-printing, while a laser-scribing technique is used to obtain laser-reduced graphene oxide (laser-rGO) patterns from deposited graphene oxide (GO) and laser-induced graphene (LIG) layouts from the bare polyimide substrate. The comparison is focused on the application of these IDE capacitors as relative humidity (RH) sensors. The different sensors are benchmarked in terms of sensitivities to RH as well as thermal drift and linearity considering frequency dependencies. The results show that the manufactured capacitors exhibit a very competitive performance as capacitive structures when compared with other similar capacitive sensors from the literature. Furthermore, inkjet-printed and LIG-based capacitors stand out for its thermal stability and linearity.
•The HNGD model was found to be unable to predict the hydride rim thickness under temperature gradient.•Two hypotheses, targeting the supersolubility and solubility, were proposed to address this ...issue.•The modified HNGD model accurately predicts the thickness of the hydride rim in a sample submitted to a temperature gradient.•The modified HNGD model predicts the hydride distribution in the case of a Zircaloy cladding with an inner Zr liner.•The modified HNGD model has been implemented and verified and is now available for general use in Bison.
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During operation of a light water reactor, waterside corrosion of the Zircaloy nuclear fuel cladding causes hydrogen pickup. The absorbed hydrogen can redistribute in the cladding driven by existing concentration, stress, and temperature gradients. When the concentration reaches the solubility limit, hydrides precipitate. These hydrides can be more brittle than the Zircaloy matrix, so they can endanger the cladding integrity during a transient if their concentration is too high. In recent years, extensive efforts have been made to understand hydrogen behavior and to develop simulation tools able to predict hydrogen diffusion and hydride precipitation and dissolution. These efforts led to the development of the Hydride Nucleation-Growth-Dissolution (HNGD) model and its implementation into the nuclear fuel performance code Bison. While it offers a significant improvement and accurately predicts the amount of precipitates, this model fails to predict the thickness of the hydride rim under a temperature gradient. The current work presents the limitation of the HNGD model and proposes two hypotheses to improve the model’s accuracy. The first hypothesis introduces a time dependency to the supersolubility to reduce the nucleation barrier as hydrogen atoms find more favorable nucleation sites. The second one introduces a hydride content dependency to the solubility. These hypotheses were validated and implemented into Bison and are now available to the user community. The modified HNGD model accurately predicts the hydride rim thickness, and it was demonstrated that this updated model can be used in Bison to model Zircaloy cladding with a zirconium inner liner. Finally, potential experimental and numerical methods are discussed to further validate these hypotheses.
Aerogels have recently received extensive attention owing to their excellent thermal insulation performance. Thus, they are widely used for thermal management in buildings, aerospace, pipelines, and ...transportation for energy saving and emission reduction. However, silica aerogels have been confirmed to possess passive radiative cooling (PRC) capacities, which may seriously retard their thermal insulation performance. Therefore, whether PRC behavior is a universal property of aerogels is an urgent problem that can determine the eventual thermal management property of aerogels. Thus, in this study, six types of aerogels with different chemical components and microstructures, including silica aerogel, boron nitride aerogel, reduced-graphene oxide aerogel, Kevlar aerogel, poly(
p
-phenylene-2,6-benzobisoxazole) aerogel, and polyimide aerogels, are synthesized, and their PRC and thermal management behaviors are investigated. Impressively, all the above-mentioned aerogels showed extensive PRC performance, with a sub-ambient cooling ranging from 6.6 to 11.1 °C at night, regardless of their chemical component or color, confirming the universal PRC behavior of various aerogels. The PRC also significantly affects the thermal insulation properties of the aerogels. The reasons for the PRC of aerogels have been discussed. The findings of this study can help to a comprehensive understanding of the thermal management behavior of aerogels and guide to a better way to use aerogels in the actual environment by considering their PRC.
The universal passive radiative cooling behavior of aerogels is revealed and their impact on thermal conductivity-related thermal insulation performance is investigated.
Since ancient times humans observed animal and plants features and tried to adapt them according to their own needs. Biomimetics represents the foundation of many inventions from various fields: From ...transportation devices (helicopter, airplane, submarine) and flying techniques, to sports' wear industry (swimming suits, scuba diving gear, Velcro closure system), bullet proof vests made from Kevlar etc. It is true that nature provides numerous noteworthy models (shark skin, spider web, lotus leaves), referring both to the plant and animal kingdom. This review paper summarizes a few of "nature's interventions" in human evolution, regarding understanding of surface wettability and development of innovative special surfaces. Empirical models are described in order to reveal the science behind special wettable surfaces (superhydrophobic /superhydrophilic). Materials and methods used in order to artificially obtain special wettable surfaces are described in correlation with plants' and animals' unique features. Emphasis is placed on joining superhydrophobic and superhydrophilic surfaces, with important applications in cell culturing, microorganism isolation/separation and molecule screening techniques. Bio-inspired wettability is presented as a constitutive part of traditional devices/systems, intended to improve their characteristics and extend performances.
Abstract
It has been suggested that Cr-coated zircaloy is an excellent material for accident-tolerant fuel (ATF) cladding. It is found that Cr coating shows multi-cracking behavior under external ...load due to its embrittlement. Different fabrication parameters will lead to different crack resistances of the coatings, but the brittle cracking characteristic is common. The estimation of the strength and structural integrity of the fuel cladding depend on the cracking characteristic of the coating. The Cr coating’s tensile characteristic for ATF cladding was examined utilizing the in-situ mechanical testing method. The surface crack initiation, propagation, and fracture process were captured in real time, and the crack density evolution of two different process parameters was compared. The results demonstrate that the first long channel crack occurs at a small strain, then the crack density increases rapidly and gradually reaches saturation with increasing stress. Different fabrication parameters will change the cracking resistance. Compared with the previous sample, the new sample started to crack at a larger strain, the crack density reached saturation faster with a larger saturated crack density, and the crack resistance is inferior. Many small cracks in different directions were observed near the fracture surface. Moreover, there was no interfacial spallation under stress, demonstrating the Cr coating’s excellent interfacial adhesive property.
This study investigates the relationship between Economic Policy Uncertainty (EPU) and innovation activities within the context of the BRICS countries (Brazil, Russia, India, China, and South Africa) ...over the period from 2000 to 2019. Focusing on the interplay between economic policy uncertainty and innovation, this research aims to provide empirical evidence regarding the potential impact of EPU on innovation efforts within these emerging economies. By employing FMOLS (fully modified ordinary least square) and controlling for other relevant factors, the study seeks to isolate the specific influence of economic policy uncertainty on innovation outcomes across the BRICS countries. The findings of the study reveal a significant and negative relationship between EPU and innovation activities. The empirical evidence suggests that heightened levels of economic policy uncertainty tend to stifle innovation efforts across these economies. This negative effect underscores the potential hindrance that uncertain economic environments can impose on research, development, and the implementation of new ideas and technologies. The implications of these findings are important for policymakers, businesses, and researchers. Policymakers can use this evidence to recognize the importance of providing stable and predictable economic policy frameworks to foster innovation. In conclusion, this study contributes to the existing literature by shedding light on the intricate relationship between EPU and innovation activities. The empirical evidence presented herein underscores the need for policy measures that promote stability and predictability in economic environments to facilitate sustained innovation and economic growth.
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Two grades of commercial AFFINISOL™ HPMC HME were used as polymer binders to explore the influence of polymer viscosity and concentration on a novel heat assisted dry granulation ...process with a twin screw extruder. Contributions of other non-binder ingredients in the formulations were also studied for lactose, microcrystalline cellulose and an active pharmaceutical ingredient of caffeine. As sensitive indicators of processing conditions that expose the drug to high internally generated heat, dehydration of α-lactose monohydrate and polymorphic transformation of caffeine were monitored by differential scanning calorimetry (DSC) and powder X-ray diffraction (XRD). Additionally, any decomposition of caffeine was determined by high-performance liquid chromatography (HPLC). Granular samples were characterized by particle size, circularity, fracture strength and their temperature on the exit of extruder. Higher screw speed and lower feed rate were found to help particles agglomerate by allowing feed particles a greater opportunity to increase in temperature. Lower binder molecular weight and higher binder concentration enable granules to build stronger strength and thereby lead to higher particle size. This new twin screw dry granulation was demonstrated as offering advantages over conventional hot melt granulation by minimizing thermal degradation of the tested ingredients.
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