• Transactions of the Korean Society of Pressure Vessels and Piping
• /
• v.16 no.2
• /
• pp.18-24
• /
• 2020

When a damage occurs in the nuclear fuel burning in the reactor, fission products that should be in the nuclear fuel rod are released into the reactor coolant. In this case, sipping test, a series of non-destructive inspection methods, are used to find leakage in nuclear fuel assemblies during the power plant overhaul period. In addition, the sipping test is also used to check the integrity of the spent fuel for moving to an intermediate dry storage, which is carried out as the first step of nuclear decommissioning, . In this paper, the principle and characteristics of the sipping test are described. The structure of the sipping inspection equipment is largely divided into a suction device that collects fissile material emitted from a damaged assembly and an analysis device that analyzes their nuclides. In order to make good use of the sipping technology, the radioactive level behavior of the primary system coolant and major damage mechanisms in the event of nuclear fuel damage are also introduced. This will be a reference for selecting an appropriate sipping method when dismantling a nuclear power plant in the future.

• Transactions of the Korean Society of Pressure Vessels and Piping
• /
• v.17 no.2
• /
• pp.137-144
• /
• 2021

The mode superposition time history analysis method is commonly used in a seismic analysis. The maximum response in the time history analysis can be derived by combining the responses of individual modes. The residual mode response is the response of the modes which are not considered in the time history analysis. In this paper, the residual vector method to consider the residual mode response in the time history analysis is introduced and evaluated. Seismic analyses for a sample structure model and a reactor vessel model are performed to evaluate the residual vector method. The analysis results show that residual mode response is well calculated when the residual vector method is used. It is confirmed that the residual vector method is useful and acceptable to consider the residual mode response in a seismic analysis of the nuclear power plant equipment.

• Transactions of the Korean Society of Pressure Vessels and Piping
• /
• v.17 no.2
• /
• pp.145-156
• /
• 2021

Ultrasonic Nanocrystal Surface Modification (UNSM) is a peening technology that generates elastic-plastic deformation on the material surface to which a static load of a air compressor and a dynamic load of ultrasonic vibration energy are applied by striking the material surface with a strike pin. In the UNSM-treated material, the structure of the surface layer is modified into a nano-crystal structure and compressive residual stress occurs. When UNSM is applied to welds in a reactor coolant system where PWSCC can occur, it has the effect of relieving tensile residual stress in the weld and thus suppressing crack initiation and propagation. In order to quantitatively evaluate the compressive residual stress generated by UNSM, many finite element studies have been conducted. In existing studies, single-path UNSM or UNSM in a limited area has been simulated due to excessive computing time and analysis convergence problems. However, it is difficult to accurately calculate the compressive residual stress generated by the actual UNSM under these limited conditions. Therefore, in this study, a minimum finite element peening analysis area that can reliably calculate the compressive residual stress is proposed. To confirm the validity of the proposed analysis area, the compressive residual stress obtained from the experiment are compared with finite element analysis results.

• Proceedings of the Computational Structural Engineering Institute Conference
• /
• 2005.04a
• /
• pp.592-600
• /
• 2005

Ship have cutout inner bottom and girder and floor etc. Ship's structure is used much, and structure strength must be situated, but establish new concept when high stress interacts sometimes fatally the area. There is no big problem usually by aim of weight reduction, a person and change of freight, piping etc.. Because cutout's existence grow up in this place, and elastic buckling strength by load causes large effect in ultimate strength. Therefore, stiffened perforated plate considering buckling strength and ultimate strength is one of important design criteria which must examine when decide structural concept at initial design. Therefore, md, reasonable buckling strength about stiffened perforated plate need to ultimate strength limited design . Calculated ultimate strength varied several web height and cutout's dimension, and thickness in this investigated data. Used program(ANSYS) applied F.E.A code based on finite element method

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.18 no.9
• /
• pp.7-16
• /
• 2019

According to KGS FS551, the safety of an exposure pipe system should be calculated quantitatively by calculating the stress of exposed piping for thermal expansion. However, many pipe system designs and installation sites are not equipped for this. Therefore, KGS FS551 suggested the use of safe gas by presenting the recommended pipe shape. The shapes of various pipe systems have been derived. However, the recommended shape could not be an absolute evaluation standard. Furthermore, the ongoing debate over standards between a plumbing installer and an inspector is an obstacle to the efficient and safe use of gas. Therefore, the correct pipe system evaluation method is examined in this study, and the safety of the existing exposed pipe system is verified.

• Journal of Mechanical Science and Technology
• /
• v.16 no.10
• /
• pp.1229-1238
• /
• 2002

In this paper, a method to obtain the sensitivity of eigenvalues and the random responses of the structure with uncertain parameters is proposed. The concept of the proposed method is that the perturbed equation of each uncertain substructure is obtained using the finite element method, and the perturbed equation of the overall structure is obtained using the mode synthesis method. By this way, the reduced order perturbed equation of the uncertain system can be obtained. And the response of the uncertain system is obtained using probability method. As a numerical example, a simple piping system is considered as an example structure. The damping and spring constants of the support are considered as the uncertain parameters. Then the variations of the eigenvalues, the correlation function and the power spectral density function of the responses are calculated. As a result, the proposed method is considered to be useful technique to analyze the sensitivities of eigenvalues and random response against random excitation in terms of the accuracy and the calculation time.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.21 no.1
• /
• pp.36-42
• /
• 2013

Recently, the automobile of the future will be able to substitute an electric vehicle for an internal combustion engine, so the following research is actively in the process of advancing. A traction motor is one of the core parts which compose the electric vehicle. Especially, it is difficult to connect cooling water piping to an in-wheel motor because the in-wheel motor is located within the wheel structure. This structure has disadvantage for closed type and air cooling, so the cooling design of motor housing and internal in-wheel motor is important. In this study, thermo-flow analysis of the in-wheel motor for vehicles was performed in consideration of ram air effect. In order to improve cooling efficiency of the motor, we variously changed geometries of housing and internal shape. As a result, we found that the cooling efficiency was most excellent, in case the cooling groove direction was same with air flow direction and arranged densely. Furthermore, we investigated the cooling performance enhancement with respect to variable geometries of internal in-wheel motor.

• Journal of the Earthquake Engineering Society of Korea
• /
• v.24 no.4
• /
• pp.179-187
• /
• 2020

Seismic qualification of equipment including piping is performed by using floor response spectra (FRS) or in-structure response spectra (ISRS) as the earthquake input at the base of the equipment. The amplitude of the FRS may be noticeably reduced when obtained from coupling analysis because of interaction between the primary structure and the equipment. This paper introduces a method using a modal synthesis approach to generate the FRS in a coupled primary-secondary system that can avoid numerical instabilities or inaccuracies. The FRS were generated by considering the dynamic interaction that can occur at the interface between the supporting structure and the equipment. This study performed a numerical example analysis using a typical nuclear structure to investigate the coupling effect when generating the FRS. The study results show that the coupling analysis dominantly reduces the FRS and yields rational results. The modal synthesis approach is very practical to implement because it requires information on only a small number of dynamic characteristics of the primary and the secondary systems such as frequencies, modal participation factors, and mode shape ordinates at the locations where the FRS needs to be generated.

• International conference on construction engineering and project management
• /
• 2017.10a
• /
• pp.89-98
• /
• 2017

The floor heating method generally uses a wet construction method including the installation of resilient material, lightweight foam concrete, heating piping, and finishing mortar. Such a wet construction method not only delays other internal finishing processes during curing period for two mortar pouring process, but also has a disadvantage that it is difficult to replace the floor heating layer when it deteriorated because it is integrated with the frame. Dry floor heating construction method can be a good alternative in that it can solve these defects. Conversely, when it applied to the wall structure that is vulnerable to the interlayer noise compared with the column-beam structure, the question about the heavy-impact sound(HIS) insulation performance is raised. Therefore, conventional dry floor heating method is hard to apply to the wall structure apartments. Therefore, for the purpose to improve the applicability of dry floor heating method in wall structure apartments, this study investigated the change of floor impact sound, especially HIS insulation performance which is one of the required performance for the floor structure. This study tried to examine whether the change of heavy-impact sound pressure level(SPL) shows a tendency at the significant level according to the shape and mass of the floor structure. Through filed experiments on wall structure apartment, this study confirmed that the form of the raised floor shows better HIS insulation performance than the fully-supported form. In addition, it was also confirmed that the HIS insulation performance increases with the mass on the upper part. Moreover, this study found the fact that a mass of about 30 kg/m² or more should be placed on the upper structure to reduce the heavy-impact SPL according to the bang machine measuring method. Although this study has a limit due to insufficient experiment samples, if the accuracy of this study is increased, it will contribute to the diffusion of dry floor heating by setting the HIS insulation performance target and designing the dry floor heating structure that meets the target.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.36 no.5
• /
• pp.370-376
• /
• 2016

Corrosion on the surface of a structure can generate cracks or cause walls to thin. This can lead to fracturing, which can eventually lead to fatalities and property loss. In an effort to prevent this, laser imaging technology has been used over the last ten years to detect thin-plate structure, or relatively thin piping. The most common laser imaging was used to develop a new technology for inspecting and imaging a desired area in order to scan various structures for thin-plate structure and thin piping. However, this method builds images by measuring waves reflected from defects, and subsequently has a considerable time delay of a few milliseconds at each scanning point. In addition, the complexity of the system is high, due to additional required components, such as laser-focusing parts. This paper proposes a laser imaging method with an increased scanning speed, based on excitation and the measurement of standing waves in structures. The wavenumber of standing waves changes at sections with a geometrical discontinuity, such as thickness. Therefore, it is possible to detect defects in a structure by generating standing waves with a single frequency and scanning the waves at each point by with the laser scanning system. The proposed technique is demonstrated on a wall-thinned plate with a linear thickness variation.