• Transactions of the Korean Society of Mechanical Engineers A
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• v.33 no.10
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• pp.1108-1118
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• 2009

A Very High Temperature Gas Cooled Reactor (VHTR) has been selected as a high energy heat source of the order of $950^{\circ}C$ for nuclear hydrogen generation, which can produce hydrogen from water or natural gas. A primary hot gas duct (HGD) as a coaxial double-tube type cross vessel is a key component connecting a reactor pressure vessel and an intermediate heat exchanger in the VHTR. In this study, a structural sizing methodology for the primary HGD of the VHTR is suggested in order to modulate a flow-induced vibration (FIV). And as an example, a structural sizing of the horizontal HGD with a coaxial double-tube structure was carried out using the suggested method. These activities include a decision of the geometric dimensions, a selection of the material, and an evaluation of the strength of the coaxial double-tube type cross vessel components. Also in order to compare the FIV characteristics of the proposed design cases, a fluid-structure interaction (FSI) analysis was carried out using the ADINA code.

• Nuclear Engineering and Technology
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• v.54 no.8
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• pp.2974-2988
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• 2022

Implementation of component isolation in nuclear industry is challenging due to gaps in research and the lack of specific guidelines. In this study, parameters affecting component-level isolation of advanced reactor vessels are identified based on a representative numerical model with explicit consideration of nonlinear soil-structure interaction (SSI). The objective of this study is to evaluate the effectiveness of, and to identify potential limitations of using conventional friction pendulum bearings to seismically isolate vessels. It is found that slender vessels or components are particularly vulnerable to rotational accelerations at the isolation interface, which are caused by rotation of the sub-structure and by excitation of higher modes in the horizontal direction of the seismically isolated system. Component isolation is found to be more effective for relatively stiffer vessels and at sites with stiff soil. Considering that conventional isolators are deficient in resisting axial tension, it is observed that the optimum location for supporting a component to achieve seismic isolation, is at a cross-sectional plane passing through the center of mass of the vessel. These findings are corroborated by numerous simulations of the response of seismically isolated reactor vessels at different nuclear power plant sites subject to a variety of ground motions.

• Nuclear Engineering and Technology
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• v.53 no.6
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• pp.1924-1930
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• 2021

By using miniature SENB specimens, the fracture properties of the materials in the region of welded metal, 321 stainless steel heat affected zone, 690 alloy heat affected zone of 321/690 dissimilar metal girth welded joints were tested. Both the J-resistance curves and critical fracture toughness of the three different materials are affected by the crack size because of the effect of crack tip constraint. Groups of constraint corrected J-resistance curves of the three materials are obtained according to J-Q-M approach. The welded metals exhibit the best fracture resistance but the worst fracture resistance is observed in the material of 690 alloy heat affected zone.

• The Transactions of the Korean Institute of Power Electronics
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• v.4 no.5
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• pp.483-490
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• 1999

In this paper, the cost-effective design of output reactor which is USCD to suppress the over-voltage at the m motor terminal in the Adjustable Speed Drives(ASD) application is proposed. In the elevator drive svstem. the R IXlwer cable length is relatively shorter than other ASD applications and then the over voltage at the motor terminal depends on the frequency characteristics of the output reactor at the over voltage operating frequency. The over-voltage suppression mechanism of output reactor in ASD application is analyzed and the dominant parameters of output reactor for the over-voltage supression are extracted. Using these as the design values and considering the high frequency characteristics of iron core in the reactor. a new c cost-effective structure of output reactor is proposed. Experimental results of the conventional reactor and the p proposed reactor with a l5kW induction motor are given to verify the propoSLD scheme.

• Nuclear Engineering and Technology
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• v.55 no.8
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• pp.2723-2733
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• 2023

Transuranic nuclides (such as ²³⁸Pu, ²⁵²Cf, ²⁴⁹Bk, etc.) have a wide range of application in industry, medicine, agriculture, and other fields. However, due to the complex conversion chain and remarkable fission losses in the process of transuranic nuclides production, the generation amounts are extremely low. High flux reactor with high neutron flux and flexible irradiation channels, is regarded as the promising candidate for producing transuranic nuclides. It is of great significance to increase the conversion ratio of transuranic nuclides, resulting in higher efficiency and better economy. In this paper, we perform an optimization design evaluation of producing transuranic nuclides in high flux reactor, which includes optimization design of irradiation target and influence study of reactor core loading. It is demonstrated that the production rate increases with appropriately determined target material and target structure. The target loading scheme in the irradiation channel also has a significant influence on the production of transuranic nuclides.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.3497-3500
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• 2007

The internal structure is subjected to dynamic analysis due to the structural integrity. The internal structure shall be installed in the vertical hole call IR1 of reactor core. In order to verify the deflection of the internal structure, the mode and response spectrum analysis of the internal structure was performed. The natural frequency of the internal structure is 11.6 Hz(mode 1 and 2) and deflections of the internal structure are less than values of allowable design (3.2 mm).

• Transactions of the Korean Society of Mechanical Engineers B
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• v.28 no.3
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• pp.265-270
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• 2004

Experiment study on a down scaled two-phase catalytic reactor is presented. As a preliminary step for the development of catalytic reactor, nano-particulate catalyst was prepared. Perovskite La$\_$0.8/Sr$\_$0.2/CoO$_3$is chosen and synthesized as a catalyst considering superior catalytic performance in reduction and oxidation process where oxygen is involved among the reagent. Reactor that has a scale of 2${\times}$10${\times}$25mm was made by machining of A1 block as a layered structure considering further extension to micro-machining. Hydrogen peroxide of 70wt% was adopted as reactant and was provided to the reactor loaded with 1.5 g of catalyst. Reactant flow rate was varied by precision pump with a range of 0.15cc/min to 17.2cc/min. Temperature distribution within reactor was recorded by 3 thermocouples and total amount of liquid product was measured. Temperature distribution and factors that affect temperature were observed and relation between temperature distribution and production rate was also analyzed. Relative time scale plays a significant role in the performance of the reactor. To obtain steady state operation, appropriate ratio of flow rate, catalyst mass and reactor geometry is required and furthermore to get more efficient production rate temperature distribution should be evenly distributed. The database obtained by the experiment will be used as a design parameter for micro reactor.

• Nuclear Engineering and Technology
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• v.56 no.1
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• pp.147-159
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• 2024

Plutonium-238 has always been considered as the one of the promising radioisotopes for space nuclear power supply, which has long half-life, low radiation protection level, high power density, and stable fuel form at high temperatures. The industrial-scale production of ²³⁸Pu mainly depends on irradiating solid ²³⁷NpO₂ target in high flux reactors, however the production process faces problems such as large fission loss and high requirements for product quality control. In this paper, a conceptual design study of producing ²³⁸Pu in a multi-purpose high flux reactor was evaluated and analyzed, which includes a sensitivity analysis on ²³⁸Pu production and a further study on the irradiation scheme. It demonstrated that the target structure and its location in the reactor, as well as the operation scheme has an impact on ²³⁸Pu amount and product quality. Furthermore, the production efficiency could be improved by optimizing target material concentration, target locations in the core and reflector. This work provides technical support for irradiation production of ²³⁸Pu in high flux reactors.

• Structural Engineering and Mechanics
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• v.43 no.4
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• pp.475-502
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• 2012

In this paper, the seismic analysis modeling technologies for sodium-cooled fast reactor (SFR) are presented with detailed descriptions for each structure, system and component (SSC) model. The complicated reactor system of pool type SFR, which is composed of the reactor vessel, internal structures, intermediate heat exchangers, primary pumps, core assemblies, and core support structures, is mathematically described with simple stick models which can represent fundamental frequencies of SSC. To do this, detailed finite element analyses were carried out to identify fundamental beam frequencies with consideration of fluid added mass effects caused by primary sodium coolant contained in the reactor vessel. The calculation of fluid added masses is performed by detailed finite element analyses using FAMD computer program and the results are discussed in terms of the ways to be considered in a seismic modeling. Based on the results of seismic time history analyses for both seismic isolation and non-isolation design, the functional requirements for relative deflections are discussed, and the design floor response spectra are proposed that can be used for subsystem seismic design.

• Journal of Industrial Technology
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• v.22 no.B
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• pp.117-124
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• 2002

We prepared the nano-sized $TiO_2$ particles by the diffusion flame reactor and investigated the effects of several process variables on the generation and transport properties of $TiO_2$ particle. As the length from the tip of diffusion flame reactor increases, the size of $TiO_2$ particle increases by the coagulation between particles. The structure of $TiO_2$ particles prepared is almost found to be anatase. It was found that the $TiO_2$ particle size depends more largely on the change of reactor temperature than on the change of inlet $TiCl_4$ concentration. By the photo-degradation experiment of phenol and toluene with the prepared $TiO_2$ particles, we found that the photo-degradation efficiencies of phenol and toluene change, depending on the process variables such as size of $TiO_2$ photocatlysts, concentration of phenol or toluene. Degradation efficiencies of phenol and toluene was above 90% in our experiments in 60 minutes.