• Journal of the Society of Naval Architects of Korea
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• v.30 no.1
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• pp.20-29
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• 1993

In this paper, a procedure is presented to optimize ship propulsion systems considering the hull- propeller-engine interactions. The propeller diameter and expanded blade ratio are systematically varied to find out the optimum combinations of RPM and BHP at a given design speed by considering cavitation criteria, and then by comparing the fuel oil consumptions of each main engine candidates which can produce each combination of RPM and BHP, appropriate main engine with the lowest fuel oil consumption together with principal characteristics of the optimum propeller are selected.

• Tribology and Lubricants
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• v.38 no.4
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• pp.136-142
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• 2022

This paper investigates the enhanced wear performance of a CrAl coated accident tolerant fuel (ATF) cladding. In the wake of the Fukushima accident, extensive research on ATF with respect to improving the oxidation resistance of cladding materials is ongoing. Since coated Zr claddings can be applied without major changes to the criteria for reactor core design, many researchers are studying coatings for claddings. To improve the quality of the CrAl coating layer, optimization of the manufacturing process is imperative. This study employs arc ion plating to obtain improved CrAl coated claddings using CrAl binary alloy targets through an improved coating method. Surface roughness and adhesion are improved, and droplets are reduced. Furthermore, the coated layer has a dense and fine microstructure. In scratch tests, all the tested CrAl coated claddings exhibit a superior resistance compared to the Zr cladding. In a fretting wear test, the wear volume of the CrAl coated claddings is smaller compared to the Zr cladding. Furthermore, the coated cladding manufactured through the improved process exhibits better wear resistance than other CrAl coated claddings. Based on these results, we suggest that fine microstructure is attributed to a mechanically and microstructurally robust CrAl coating layer, which enhances wear resistance.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.31 no.12
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• pp.1165-1172
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• 2007

The spacer grid set is a part of a nuclear fuel assembly. The set has a spring and the spring supports the fuel rods safely. Although material nonlinearity is involved in the deformation of the spring, nonlinearity has not been considered in design of the spring. Recently a nonlinear response structural optimization method has been developed using equivalent loads. It is called nonlinear response optimization equivalent loads (NROEL). In NROEL, the external loads are transformed to the equivalent loads (EL) for linear static analysis and linear response optimization is carried out based on the EL in a cyclic manner until the convergence criteria are satisfied. EL is the load set which generates the same response field of linear analysis as that of nonlinear analysis. Shape optimization of the spring is carried out based on EL. The objective function is defined by minimizing the maximum stress in the spring while mass is limited and the support force of the spring is larger than a certain value. The results are verified by nonlinear response analysis. ABAQUS is used for nonlinear response analysis and GENESIS is employed for linear response optimization.

• Proceedings of the KSME Conference
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• 2007.05a
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• pp.694-699
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• 2007

The spacer grid set is a part of a nuclear fuel assembly. The set has a spring and the spring supports the fuel rods safely. Although material nonlinearity is involved in the deformation of the spring,nonlinearity has not been considered in design of the spring. Recently a nonlinear response structural optimization method has been developed using equivalent loads. It is called nonlinear response optimization equivalent loads (NROEL). In NROEL, the external loads are teansformed to the equivalent loads (EL) for linear static analysis and linear response optimization is carried out based on the EL in a cyclic manner until the convergence criteria are satisfied. EL is the load set which generates the same response no EL. The objective function is defined by minimizing the maximum stress in the spring while is limited and the support force of the spring is larger than a certain value. The results are verified by nonlinear. ABAQUS is used for nonlinear response analysis and GENESIS is employed for linear response optimization.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.25 no.3
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• pp.189-197
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• 2016

Green vehicles include electric vehicles, natural gas vehicles, and fuel cell vehicles (FCVs). In FCVs, pressure vessels have cylinder valves to control hydrogen flow. These valves should be of high quality in terms of safety because hydrogen is stored at ultra-high pressure in pressure vessels. Hence, safety evaluation of these valves is necessary to secure the safety of the FCV. A structural analysis of the cylinder valve was conducted in this study by using a commercial finite element analysis code. The results showed that the safety factor of valve component ranged 1.06-186.44. After categorizing, the stress components at critical points of the cylinder valve parts were evaluated using the corresponding allowable design criteria in the ASME code. The pressurization cycle test was performed as per the regulation to evaluate the safety of the valve.

• Nuclear Engineering and Technology
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• v.27 no.5
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• pp.687-700
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• 1995

The thermal-hydraulic transient analysis of the proposed CANDU-9 plant was peformed. Several major transients ore analyzed if they meet the heat transport system design requirements. The proposed heat transport system configuration and the preliminary sizes of system equipment are justified by analysis in terms of the fuel integrity and the high system pressure limit during transients. The compliance with AECB R-77 requirements for CANDU-9 reactor was estimated. The analysis results showed that for each postulated accident the peak pressure values in the reactor headers are within the acceptance criteria given in ASME code requirements and the fuel overheating is prevented. One pump start-up during the reactor start-up operation was analyzed to investigate the How reversal through the fuel channel, which is specific in the proposed CANDU-9 plant.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.05a
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• pp.985-990
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• 2003

In order to demonstrate Advanced Spent Fuel Conditioning Process (ACP), shielding facilities such as hot cell suitable to handling radionuclides and process property will be necessary. But the construction of new facilities needs much money, man-power and time, it is now scheduled to remodel the hot cell, which has already been installed and maintained at Irradiated Material Experiment Facility (IMEF) in the Korea Atomic Energy Research Institute (KAERI). The basic structure and concrete shield wall of hot cell partly have been constructed on the base floor in IMEF building in current status. And hot cell after remodeling will be used for carrying out the lab-scale experiment of ACP. The hot cell was built in accordance with 35 curies of fe-59(1.2 MeV) as design criteria of radiation dose limit. But the radioactive source of ACP is expected to be much higher than design criteria of IMEF, shielding ability of the hot cell in the current status is unsatisfactory to the hot test of ACP. Therefore shield wall shall be reinforced with heavy concrete, steel or lead. In this paper, dose rates are calculated according to ACP source, shielding materials, etc., and reinforcement structures are determined considering the current situation of hot cells, installation of shield windows and the easiness of work.

• Tunnel and Underground Space
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• v.33 no.5
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• pp.312-338
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• 2023

The underground disposal facility for spent nuclear fuel demands a specialized design, distinct from conventional practices, to ensure long-term thermal, mechanical, and hydraulic integrity, preventing the release of radioactive isotopes from high-temperature spent nuclear fuel. SKB has established design criteria for such facilities and executed practical design implementations for Forsmark. Moreover, in response to subsurface uncertainty, SKB has proposed an empirical approach involving monitoring and adaptive design modifications, alongside stepwise development. SKB has further introduced a unique support system, categorizing ground types and behaviors and aligning them with corresponding support types to confirm safety through comparative analyses against existing systems. POSIVA has pursued a comparable approach, developing a support system for Onkalo while accounting for distinct geological characteristics compared to Forsmark. This demonstrates the potential for domestic implementation of spent nuclear fuel disposal facility designs and the establishment of a support system adapted to national attributes.

• International Journal of Precision Engineering and Manufacturing
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• v.9 no.1
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• pp.39-46
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• 2008

The end plates of fuel cell assemblies are used to fasten the inner stacks, reduce the contact pressure, and provide a seal between Membrane-Electrode Assemblies (MEAs). They therefore require sufficient mechanical strength to withstand the tightening pressure, light weight to obtain high energy densities, and stable chemical/electrochemical properties, as well as provide electrical insulation. The design criteria for end plates can be divided into three parts: the material, connecting method, and shape. In the past, end plates were made from metals such as aluminum, titanium, and stainless steel alloys, but due to corrosion problems, thermal losses, and their excessive weight, alternative materials such as plastics have been considered. Composite materials consisting of combinations of two or more materials have also been proposed for end plates to enhance their mechanical strength. Tie-rods have been traditionally used to connect end plates, but since the number of connecting parts has increased, resulting in assembly difficulties, new types of connectors have been contemplated. Ideas such as adding reinforcement or flat plates, or using bands or boxes to replace tie-rods have been proposed. Typical end plates are rectangular or cylindrical solid plates. To minimize the weight and provide a uniform pressure distribution, new concepts such as ribbed-, bomb-, or bow-shaped plates have been considered. Even though end plates were not an issue in fuel cell system designs in the past, they now provide a great challenge for designers. Changes in the materials, connecting methods, and shapes of an end plate allow us to achieve lighter, stronger end plates, resulting in more efficient fuel cell systems.

• Fire Science and Engineering
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• v.28 no.3
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• pp.34-42
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• 2014

The concentrations of inert gases ($N_2$, Ar, $CO_2$ and He) required to induce the flame instabilities such as swing, rotation, lifted and blow-out were measured in a cup burner nonpremixed flames for $CH_4$ and $C_3H_8$ fuels. Quantitative differences in the extinguishing concentration with fire suppression criteria (i.e. blow-out or onset of flame instability) were also examined. It was found that the difference in extinguishing concentration was increased with the appearance of lifted flame and the low extinguishing performance of inert gaseous. The maximum difference in extinguishing concentration with the suppression criteria was approximately 35% at the highest fuel velocity condition (1.3 cm/s) for the $C_3H_8$-air nonpremixed flame. It can be also expected that the extinguishing concentration by the criteria based on the onset of flame instability will provide the useful information from the viewpoint of the accurate and economical design concentration.