• Proceedings of the Materials Research Society of Korea Conference
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• 2012.05a
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• pp.51-51
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• 2012

There is a growing interest in innovative chemical synthesis in microreactors owing to high efficiency, selectivity, and yield. In microfluidic systems, the low-volume spatial and temporal control of reactants and products offers a novel method for chemical manipulation and product generation. Glass, silicon, poly(dimethylsiloxane) (PDMS), and plastics have been used for the fabrication of miniaturized devices. However, these materials are not the best due to either of low chemical durability or expensive fabrication costs. In our group, we have recently addressed the demand for economical resistant materials that can be used for easy fabrication of microfluidic systems with reliable durability. We have suggested the use of various specialty polymers such as silicon-based inorganic polymers and fluoropolymer, flexible polyimide (PI) films that have not been used for microfluidic devices, although they have been used for other areas. And inexpensive lithography techniques were used to fabricate Lab-on-a-Chip type of microreactors with differently devised microchannel design. These microreactors were demonstrated for various synthetic reactions: liquid, liquid-gas organic chemical reactions in heterogeneous catalytic processes, syntheses of polymer and non-trivial inorganic materials. The microreactors were inert, and withstand even harsh conditions, including hydrothermal reaction. In addition, various built-in microstructures inside the microchannels, for example Pd decorated peptide nanowires, definitely enhance the uniqueness and performance of microreactors. These user-friendly Lab-on-a-Chip devices are useful alternatives for chemist and chemical engineer to conventional chemical tools such as glass.

• Nuclear Engineering and Technology
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• v.56 no.3
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• pp.855-865
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• 2024

Commercial deployment of nuclear microreactors presents an opportunity for the industry to rethink its approach to manufacturing, siting, operation and maintenance, and fuel cycle management as certain principles used in grid-scale nuclear projects are not applicable to a decentralized microreactor economy. The success of this nascent industry is dependent on its ability to reduce infrastructure, logistical, regulatory and lifecycle costs. A utility-like 'Central Facility' that consolidates the services required and responsibilities borne by vendors into one or a few centralized locations will be necessary to support the deployment of a fleet of microreactors. This paper discusses the requirements for a Central Facility, its implications on the cost structures of owners and suppliers of microreactors, and the impact of the facility for the broader microreactor industry. In addition, this paper discusses the pre-requisites for eligibility as well as the opportunities for a Central Facility host site. While there are many suitable locations for such a capability across the U.S., this paper considers a facility co-located with the Vogtle Nuclear Power Plant and Savannah River Sites to illustrate how a Central Facility can leverage the existing infrastructure and stimulate a local ecosystem.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.2896-2900
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• 2007

A numerical analysis was carried out to investigate the degradation of Volatile Organic Compounds (VOC) in photocatalytic microreactors with different inner geometries. Two different cases of microreactor were considered, namely, one microreactor has bump on the channel and the other has no bump on the channel. The removal efficiency of VOC has been calculated by the Langmuir-Hinshelwood reaction rate equation that was obtained from the experimental results. From the numerical calculations, it was observed that the conversion ratio of VOC for the microchannel with bump is about 4.5% greater than the microchannel without bump. And the mass transfer characteristics in the microreactor are also shown in numerical results. These results can be used effectively for the photocatalytic numerical analysis.

• Nuclear Engineering and Technology
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• v.54 no.4
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• pp.1482-1494
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• 2022

Power conversion cycles (Subcritical Steam, Supercritical Steam, Open Air Brayton, Recuperated Air Brayton, Combined Cycle, Closed Brayton Supercritical CO₂ (sCO₂), and Stirling) are evaluated for land-based nuclear microreactors based on technical maturity, system efficiency, size, cost and maintainability, safety implications, and siting considerations. Based upon these criteria, Air Brayton systems were selected for further evaluation. A brief history of the development and applications of Brayton power systems is given, followed by a description of how these thermal-to-electrical energy conversion systems might be integrated with a nuclear microreactor. Modeling is performed for optimized cycles operating at 3 MW(e) with turbine inlet temperatures of 500 ℃, 650 ℃ and 850 ℃, corresponding to: a) sodium fast, b) molten salt or heat pipe, and c) helium or sodium thermal reactors, coupled with three types of Brayton power conversion units (PCUs): 1) simple open-cycle gas turbine, 2) recuperated open-cycle gas turbine, and 3) recuperated and intercooled open-cycle gas turbine. Aeroderivative turboshaft engines employing the simple Brayton cycle and two industrial gas turbine engines employing recuperated air Brayton cycles are also analyzed. These engines offer mature technology that can facilitate near-term deployment with a modest improvement in efficiency.

• Journal of Photoscience
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• v.10 no.1
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• pp.175-180
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• 2003

Zeolite, Nafion membranes and vesicles were used as microreactors to control the pathway of photosensitized oxidation of alkenes and remarkable selectivity was achieved.

• Journal of Microbiology and Biotechnology
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• v.17 no.11
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• pp.1826-1832
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• 2007

We describe the fabrication of poly(ethylene glycol) diacrylate (PEG-DA) hydrogel microstructures with a high aspect ratio and the use of hydrogel microstructures containing the enzyme ${\beta}$-galactosidase (${\beta}$-Gal) or glucose oxidase (GOx)/horseradish peroxidase (HRP) as biosensing components for the simultaneous detection of multiple analytes. The diameters of the hydrogel microstructures were almost the same at the top and at the bottom, indicating that no differential curing occurred through the thickness of the hydrogel microstructure. Using the hydrogel microstructures as microreactors, ${\beta}$-Gal or GOx/HRP was trapped in the hydrogel array, and the time-dependent fluorescence intensities of the hydrogel array were investigated to determine the dynamic uptake of substrates into the PEG-DA hydrogel. The time required to reach steady-state fluorescence by glucose diffusing into the hydrogel and its enzymatic reactions with GOx and HRP was half the time required for resorufin ${\beta}$-D-galactopyranoside (RGB) when used as the substrate for ${\beta}$-Gal. Spatially addressed hydrogel microarrays containing different enzymes were micropatterned for the simultaneous detection of multiple analytes, and glucose and RGB solutions were incubated as substrates. These results indicate that there was no cross-talk between the ${\beta}$-Gal-immobilizing hydrogel micropatches and the GOx/HRP-immobilizing micropatches.

• Nuclear Engineering and Technology
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• v.56 no.3
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• pp.1108-1115
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• 2024

Assuring physical security for Micro Modular Reactors (MMRs) will be key to their licensing. Economic constraints however require changes in how the security objectives are achieved for MMRs. A promising new approach is the so-called performance based (PB) approach wherein the regulator formally sets general security objectives and leaves it to the licensee to set their own specific acceptance criteria to meet those objectives. To implement the PB approach for MMRs, one performs a consequence-based analysis (CBA) whose objective is to study hypothetical malicious attacks on the facility, assuming that intruders take control of the facility and perform any technically possible action within a limited time before an offsite security force can respond. The scenario leading to the most severe radiological consequences is selected and studied to estimate the limiting impact on public health. The CBA estimates the total amount of radionuclides that would be released to the atmosphere in this hypothetical scenario to determine the total radiation dose to which the public would be exposed. The predicted radiation exposure dose is then compared to the regulatory dose limit for the site. This paper describes application of the CBA to four different MMRs technologies.

• Journal of the Korean Vacuum Society
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• v.16 no.1
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• pp.65-73
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• 2007

The control of surface properties and spatial presentation of functional molecules within a microfluidic channel is important for the development of diagnostic assays, microreactors, and for performing fundamental studies of cell biology and fluid mechanics. Here, we present soft lithographic methods to create robust microchannels with patterned microstructures inside the channel. The patterned regions were protected from oxygen plasma by controlling the dimensions of the poly(dimethylsiloxane)(PDMS) mold as well as the sequence of fabrication steps. The approach was used to pattern a non-biofouling polyethylene glycol(PEG)-based copolymer or the polysaccharide hyaluronic acid(HA) within microfluidic channels. These non-biofouling patterns were then used to fabricate arrays of fibronectin(FN) and bovine serum albumin(BSA) as well as mammalian cells.

• Korean Chemical Engineering Research
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• v.59 no.4
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• pp.639-643
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• 2021

In this study, fluorinated ethylene propylene (FEP) nanoparticle as an adhesive for fabricating a three-dimensional multilayered microfluidic device was studied. The formation of evenly distributed FEP nanoparticles layer with 3 ㎛ in thickness on substrates was achieved by simple spin coating of FEP dispersion solution at 1500 rpm for 30 s. It is confirmed that FEP nanoparticles transformed into a hydrophobic thin film after thermal treatment at 300 ℃ for 1 hour, and fabricated polyimide film-based microfluidic device using FEP nanoparticle was endured pressure up to 2250 psi. Finally, a three-dimensional multilayered microfluidic device composed of 16 microreactors, which are difficult to fabricate with conventional photolithography, was successfully realized by simple one-step alignment of FEP coated nine polyimide films. The developed three-dimensional multilayered microfluidic device has the potential to be a powerful tool such as high-throughput screening, mass production, parallelization, and large-scale microfluidic integration for various applications in chemistry and biology.

• Nuclear Engineering and Technology
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• v.55 no.9
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• pp.3409-3416
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• 2023

Licensing the next-generation of nuclear reactor designs requires extensive use of Modeling and Simulation (M&S) to investigate system response to many operational conditions, identify possible accidental scenarios and predict their evolution to undesirable consequences that are to be prevented or mitigated via the deployment of adequate safety barriers. Deep Learning (DL) and Artificial Intelligence (AI) can support M&S computationally by providing surrogates of the complex multi-physics high-fidelity models used for design. However, DL and AI are, generally, low-fidelity 'black-box' models that do not assure any structure based on physical laws and constraints, and may, thus, lack interpretability and accuracy of the results. This poses limitations on their credibility and doubts about their adoption for the safety assessment and licensing of novel reactor designs. In this regard, Physics Informed Neural Networks (PINNs) are receiving growing attention for their ability to integrate fundamental physics laws and domain knowledge in the neural networks, thus assuring credible generalization capabilities and credible predictions. This paper presents the use of PINNs as surrogate models for accidental scenarios simulation in Nuclear Power Plants (NPPs). A case study of a Loss of Heat Sink (LOHS) accidental scenario in a Nuclear Battery (NB), a unique class of transportable, plug-and-play microreactors, is considered. A PINN is developed and compared with a Deep Neural Network (DNN). The results show the advantages of PINNs in providing accurate solutions, avoiding overfitting, underfitting and intrinsically ensuring physics-consistent results.