원전 배관 지진응답 거통특성 및 내진성능 평가

곽신영 ( Kwag Shinyoung ),임승현 ( Eem Seunghyun ),곽진성 ( Kwak Jinsung ),오진호 ( Oh Jinho ) 한국복합신소재구조학회 2020 복합신소재구조학회논문집 Vol.11 No.1

최근 국내에서 발생한 경주지진 및 포항지진이 도심지 및 원자력발전소 주변에서 발생함에 따라 인근 주요 구조시스템에 피해를 발생시킨 바 있다. 이에 따라, 본 연구는 원전 배관계통의 지진 거동 특성을 실험 및 해석적으로 규명하고, 이를 바탕으로 내진성능을 평가하는 연구를 수행하는 것을 목적으로 한다. 이를 위하여, 원전 배관계통을 대상으로 한 진동대 시험 결과를 바탕으로 배관 수치해석 모델을 수립하고 이를 시험 결과를 통하여 검증한다. 또한, 이러한 검증된 수치해석모델을 기반으로 배관계통의 내진성능을 평가한다. 수치해석 모델 검증 결과, 수립된 수치모델의 고유진동수, 감쇠비 및 변위 응답이 진동대시험 결과와 유사한 것으로 나타났다. 이러한 검증된 수치모델을 바탕으로 평가된 내진성능 값은 기존 원전 배관의 내진성능 값의 범위와 비교적 유사한 값으로 평가되었다. 이는 설계기준지진을 크게 상회하는 값이지만, 원전 주요 기기 임을 감안할 때 추가적인 내진성능 상향이 확보되면 원전 지진 안전성 향상에 많은 기여를 할 수 있을 것으로 판단된다. 본 연구의 결과는 추후 원전 배관계통 내진성능평가를 위한 정량적인 자료로 활용이 가능할 것으로 판단된다. The recent earthquakes in Gyeongju and Pohang have damaged the major local structures and buildings since they occurred in urban areas and near nuclear power plants. Thus, this study aims to reveal, experimentally and analytically, the earthquake behavior of the piping systems of nuclear power plants and to assess their seismic performance. Based on shaking table test results, the numerical analysis model of a piping system was developed and validated; then, it was used to assess its seismic performance. The validation showed that the fundamental frequency, damping ratio, and displacement response of this numerical model were consistent with the shaking table test results. In addition, the seismic performance estimated by using this model was relatively similar to the performance range of existing nuclear plant piping systems. Thus, these results of this study could serve, in future studies, as quantitative data for assessing the seismic performance of piping systems in nuclear power plants.

Origin of Tearing Paths in Transferred Graphene by H2 Bubbling Process and Improved Transfer of T ear-Free Graphene Films U sing a H eat Press

곽진성 한국재료학회 2022 한국재료학회지 Vol.32 No.12

Among efforts to improve techniques for the chemical vapor deposition of large-area and high-quality graphene films on transition metal substrates, being able to reliably transfer these atomistic membranes onto the desired substrate is a critical step for various practical uses, such as graphene-based electronic and photonic devices. However, the most used approach, the wet etching transfer process based on the complete etching of metal substrates, remains a great challenge. This is mainly due to the inevitable damage to the graphene, unintentional contamination of the graphene layer, and increased production cost and time. Here, we report the systematic study of an H2 bubbling-assisted transfer technique for graphene films grown on Cu foils, which is nondestructive not only to the graphene film but also to the Cu substrate. Also, we demonstrate the origin of the graphene film tearing phenomenon induced by this H2 bubbling-assisted transfer process. This study reveals that inherent features are produced by rolling Cu foil, which cause a saw-like corrugation in the poly(methyl methacrylate) (PMMA)/graphene stack when it is transferred onto the target substrate after the Cu foil is dissolved. During the PMMA removal stage, the graphene tearing mainly appears at the apexes of the corrugated PMMA/graphene stack, due to weak adhesion to the target substrate. To address this, we have developed a modified heat-press-assisted transfer technique that has much better control of both tearing and the formation of residues in the transferred graphene films.

회전익 항공기의 제자리 및 전진 비행에 대한 전산유체-구조 결합해석

곽진성,윤성환,신상준,김종암 한국항공우주학회 2009 한국항공우주학회 학술발표회 논문집 Vol.2009 No.11

2차원 나노소재의 합성 및 대면적 성장 기술

곽진성,윤형덕,권순용 한국세라믹학회 2017 세라미스트 Vol.20 No.3

Shaking table test and numerical analysis of nuclear piping under low- and high-frequency earthquake motions

곽신영,임승현,곽진성,이환호,오진호,구경회,장성진,전법규 한국원자력학회 2022 Nuclear Engineering and Technology Vol.54 No.9

A nuclear power plant (NPP) piping is designed against low-frequency earthquakes. However, earthquakes that can occur at NPP sites in the eastern part of the United States, northern Europe, and Korea are high-frequency earthquakes. Therefore, this study conducts bi-directional shaking table tests on actualscale NPP piping and studies the response characteristics of low- and high-frequency earthquake motions. Such response characteristics are analyzed by comparing several responses that occur in the piping. Also, based on the test results, a piping numerical analysis model is developed and validated. The piping seismic performance under high-frequency earthquakes is derived. Consequently, the highfrequency excitation caused a large amplification in the measured peak acceleration responses compared to the low-frequency excitation. Conversely, concerning relative displacements, strains, and normal stresses, low-frequency excitation responses were larger than high-frequency excitation responses. Main peak relative displacements and peak normal stresses were 60%e69% and 24%e49% smaller in the high-frequency earthquake response than the low-frequency earthquake response. This phenomenon was noticeable when the earthquake motion intensity was large. The piping numerical model simulated the main natural frequencies and relative displacement responses well. Finally, for the stress limit state, the seismic performance for high-frequency earthquakes was about 2.7 times greater than for low-frequency earthquakes

동흡진기를 사용한 원전 배관계 내진성능 상향에 대한 연구

곽신영,곽진성,이환호,오진호,구경회 한국압력기기공학회 2018 한국압력기기공학회 논문집 Vol.14 No.2

In this study, the dynamic absorber and the damper are applied to improve the seismic performance of the piping system, and their quantitative effects on the piping system performance are examined. For this purpose, the response performances of piping system applied with the dynamic absorber/damper are compared with those of the original piping system. Firstly, the frequency response analyses of the piping system with the presence or the absence of dynamic absorber/damper are performed and these results are compared. It has been shown that the maximum acceleration response per the frequency of the piping system is considerably reduced by installing the dynamic absorber and the damper. Secondly, the seismic responses of the piping systems with and without dynamic absorber/damper are compared. As a result of the numerical analyses, it is confirmed that key responses are reduced by 17%-63% due to the installation of the dynamic absorber and damper. Finally, as a result of the seismic performance evaluation, it is confirmed that the HCLPF (High Confidence of Low Probability of Failure) seismic performances are increased by 1.22 to 2.70 times with respect to the failure modes with an aid of the dynamic absorber and damper.

Improvement on optimal design of dynamic absorber for enhancing seismic performance of nuclear piping using adaptive Kriging method

곽신영,임승현,곽진성,이환호,오진호,구경회 한국원자력학회 2022 Nuclear Engineering and Technology Vol.54 No.5

For improving the seismic performance of the nuclear power plant (NPP) piping system, attempts havebeen made to apply a dynamic absorber (DA). However, the current piping DA design method is limitedbecause it cannot provide the globally optimum values for the target design seismic loading. Therefore,this study proposes a seismic time history analysis-based DA optimal design method for piping. To thisend, the Kriging approach is introduced to reduce the numerical cost required for seismic time historyanalyses. The appropriate design of the experiment method is used to increase the efficiency in securingresponse data. A gradient-based method is used to efficiently deal with the multi-dimensional unconstrained optimization problem of the DA optimal design. As a result, the proposed method showed anexcellent response reduction effect in several responses compared to other optimal design methods. Theproposed method showed that the average response reduction rate was about 9% less at the maximumacceleration, about 5% less at the maximum value of the response spectrum, about 9% less at themaximum relative displacement, and about 4% less at the maximum combined stress compared toexisting optimal design methods. Therefore, the proposed method enables an effective optimal DA designmethod for mitigating seismic response in NPP piping in the future

회전익 항공기의 기체 구성품을 고려한 트림해석 개발

곽진성,신상준,김덕관,이관중,이준배 한국항공우주학회 2010 한국항공우주학회 학술발표회 논문집 Vol.2010 No.4

동흡진기 적용을 통한 원전기기의 내진성능향상에 관한 수치적 연구

곽신영,곽진성,이환호,오진호,구경회 한국전산구조공학회 2019 한국전산구조공학회논문집 Vol.32 No.1

In this paper, we study the applicability of Tuned Mass Damper(TMD) to improve seismic performance of piping system under earthquake loading. For this purpose, a mode analysis of the target pipeline is performed, and TMD installation locations are selected as important modes with relatively large mass participation ratio in each direction. In order to design the TMD at selected positions, each corresponding mode is replaced with a SDOF damped model, and accordingly the corresponding pipeline is converted into a 2-DOF system by considering the TMD as a SDOF damped model. Then, optimal design values of the TMD, which can minimize the dynamic amplification factor of the transformed 2-DOF system, are derived through GA optimization method. The proposed TMD design values are applied to the pipeline numerical model to analyze seismic performance with and without TMD installation. As a result of numerical analyses, it is confirmed that the directional acceleration responses, the maximum normal stresses and directional reaction forces of the pipeline system are reduced, quite a lot. The results of this study are expected to be used as basic information with respect to the improvement of the seismic performance of the piping system in the future.

다중 압력 스펙트럼 밀도를 이용한 감쇠 탱크 구조 건전성 평가

곽진성(Kwak Jinsung),정민규(Jung Min-kyu),오진호(Oh Jinho),이종민(Lee Jong-min) 대한기계학회 2016 대한기계학회 춘추학술대회 Vol.2016 No.12

The main purpose of PCS(Primary Cooling System) is to remove heat generated from the reactor core through the heat exchangers. The coolant passing through the reactor core contains a variety of radionuclides. N-16 governs the coolant radioactivities at the core exit, but it has a very short decay time. The main function of decay tank is to decay the readionuclides, especially N-16 by providing enough transient time to ensure that N-16 activity decreases in the decay tank. The decay tank has three internal perforated plates which spread the coolant into the whole section of the decay tank to increase transit time. The perforated plate is affected by various loadings such as seismic load, thermal load, flow induced vibration and etc. Specially, the pressure induced by flow gives the main effect to the structure integrity of the perforated plate. In this paper, structure integrity of decay tank including fatigue is evaluated through the pressure power spectral density functions that are derived from turbulent flow.