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Round robin analysis of vessel failure probabilities for PTS events in Korea
정명조,오창식,최영인,강성식,김만원,김태현,김종민,김민철,이봉상,김종민,김규완 한국원자력학회 2020 Nuclear Engineering and Technology Vol.52 No.8
Round robin analyses for vessel failure probabilities due to PTS events are proposed for plant-specific analyses of all types of reactors developed in Korea. Four organizations, that are responsible for regulation, operation, research and design of the nuclear power plant in Korea, participated in the round robin analysis. The vessel failure probabilities from the probabilistic fracture mechanics analyses are calculated to assure the structural integrity of the reactor pressure vessel during transients that are expected to initiate PTS events. The failure probabilities due to various parameters are compared with each other. All results are obtained based on several assumptions about material properties, flaw distribution data, and transient data such as pressure, temperature, and heat transfer coefficient. The realistic input data can be used to obtain more realistic failure probabilities. The various results presented in this study will be helpful not only for benchmark calculations, result comparisons, and verification of PFM codes developed but also as a contribution to knowledge management for the future generation.
장윤석(Yoon-Suk Chang),윤강옥(Kang-Ok Yun),박영재(Young-Jae Park),김영진(Young-Jin Kim) 대한기계학회 2004 대한기계학회 춘추학술대회 Vol.2004 No.8
The deterministic evaluation methods could not predict exactly the real material behaviors due to the uncertainties. Recently, worldwide researches for economic operation and safe maintenance of nuclear power plant are being carried out based on risk and failure probability. However, unfortunately, few efficient tools to predict the failure probability of wall-thinned piping have been developed from the researches at this time. So, to settle the wall-thinned piping problem, it is necessary to develop the enhanced deterministic evaluation method and to put the probabilistic evaluation method on a firm footing based on the deterministic one. This paper describes enhanced deterministic evaluation method based on a series of finite element analyses, and development of the probabilistic evaluation program based on FORM and Monte Carlo simulation, and calculate failure probability of wall-thinned piping.
치수변화를 고려한 CANDU 압력관의 축방향 결함에 대한 파손확률 예측
곽상록(Sang-Log Kwak),이준성(Joon-Seong Lee),김영진(Young-Jin Kim),박윤원(Youn-Won Park) 대한기계학회 2002 대한기계학회 춘추학술대회 Vol.2002 No.3
The pressure tube is a major component of the CANDU reactor, which supports nuclear fuel bundle and heavy water coolant. Pressure tubes are installed horizontally inside the reactors and only selected samples are periodically examined during in-service inspection(ISI) due to numerous numbers of tubes. ISI results shows half of the pressure tubes have flaw, and axial flaw is dominant rather than circumferential flaw in pressure tube. In this respect, a probabilistic safety assessment method is more appropriate for the assessment of overall pressure tube safety. The failure behavior of CANDU pressure tubes, however, is governed by delayed hydride cracking which is not considered in the application of PFM on pipings and vessels. Since the delayed hydride cracking has more widely distributed governing parameters, it is impossible to apply a general PFM methodology directly. In this paper, a PFM methodology for the safety assessment of CANDU pressure tubes is introduced by applying Monte Carlo simulation in determining failure probability. Initial hydrogen concentration, flaw shape and depth, crack growth rate and fracture toughness were considered as probabilistic variables. Parametric study has been done under the base of pressure tube dimensions, which are derived from ISI data. Applying both unstable fracture condition and plastic collapse condition set failure criteria. The estimated failure probability showed about three-order difference with changing dimensions of pressure tube.
高溫下 304 스테인리스鋼의 크리프-疲勞相互作用下의 미소표면균열에 관한 파괴거동
서창민(Chang-Min Suh),이상돈(Sang-Don Lee),조일현(Il-Hyun Cho) 한국해양공학회 1988 韓國海洋工學會誌 Vol.2 No.2
This paper deals with the micro-surface-cracks behavior on the unnotched smooth specimens of Type 304 stainless steel at 593℃ in air under creep and creep-fatigue conditions that have 10 min and 1 min load holding times respectively. The behaviors of the micro-surface-cracks have been visualized by means of surface replica method and optical micro-photography. The quantitative characteristics of initiation, growth and coalescence of micro-surface-cracks have been investigated by observing and measuring the crack growth behaviors.<br/> Some of the important results are as follows:<br/> Main crack initiates at grain boundary in the early stage(10 to 20%) of its life time and grows through coalescence and finally leads to fracture. The distribution of micro-surface-crack length, 2a, can be plotted against the composite Weibull distribution. The growth rate of the main crack can be plotted against the stress intensity factor, crack tip opening displacement and J integral.
An Evaluation Method of Probability of Elastic-Plastic Fracture by 2-Parameter Criterion
Kim, Tae-Sik,Yoon, Han-Yong,Lim, Myung-Hwan,Jung, Ui-Jung The Korean Society of Mechanical Engineers 2004 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.18 No.1
Many researchers have made a lot of progress in studying the evaluation of fracture probability of brittle materials. However, studies of fracture probability for elastic-plasticity have not been made yet. An evaluation method for fracture probability which is grafted onto a 2-parameter criterion and statistical probability analysis is not only introduced in this study, but also applied to the simple 2-dimensional model and carbon steel piping to vealuate the effect of statistical variables.
Kim, Saekyeol,Cho, Su-gil,Lim, Woochul,Lee, Tae Hee,Park, Sanghyun,Hong, Sup,Kim, Hyung-Woo,Min, Cheon-Hong,Choi, Jong-Su,Ko, Young-Tak,Chi, Sang-Bum Pergamon Press 2019 Ocean engineering Vol.171 No.-
<P><B>Abstract</B></P> <P>In this paper, probability distribution for the size and mass of seafloor manganese nodules is investigated to improve the reliability of a pick-up device in a deep-sea manganese nodule miner. Because the size and mass of the manganese nodules are strongly correlated, statistical models for the size and mass cannot be estimated independently. In order to consider the correlation between the size and mass in a statistical model, the joint probability density function (PDF) is estimated by using copula. This method requires the estimation of the marginal distributions and copula for the two correlated environmental variables. However, this is significantly difficult when there is no prior knowledge of the two physical properties. The proposed method, which employs the Akaike information criterion to select the fittest marginal distributions and copula, provides a systematic procedure to determine a statistical model of correlated environmental variables without any prior knowledge of their distributions. To demonstrate the effectiveness of the proposed method, the joint PDF for the size and mass of manganese nodules is modeled by using the multivariate normal distribution and the proposed method. It was found that the proposed method provides more accurate and reliable estimation results for the two correlated environmental variables.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Estimation of joint distribution for size and mass of deep-sea manganese nodule. </LI> <LI> Statistical modeling method for correlated environmental variables. </LI> <LI> Systematic method to obtain the statistical model without any prior knowledge. </LI> <LI> Akaike information criterion to find the fittest marginal distributions and copula. </LI> </UL> </P>
STS304강의 순수 및 외팔보형 굽힘피로에 대한 파괴확률특성
노성국,정순억 경상대학교 해양산업연구소 2002 해양산업연구소보 Vol.15 No.-
Big accidents of flyings, vessel, subways, gas equipments, buildings and bridge happens frenquently. Therefore many people are suffering harm of property. The destruction cause of macaine components is almost accused by fatigue. This study is test for STS304 specimen by using pure and cantilever bending state. Rounded specimen and notched specimen including fracture surface investigation was comparatively experimented, fatigue life according to degree of surface finishing was examined. Fatigue fracture probability of notched canilever specimens were predicted by P-S-N curve, median rank and Weibull distribution. And at the relation with the rotational speed and stress the fatigue life of the test specimen was higher than low speed at high speed.
최대가능성방법을 이용한 압력용기강 재료의 벽개파손확률 분석
고한옥(Han-Ok Ko),장윤석(Yoon-Suk Chang),최재붕(Jae-Boong Choi),김영진(Young-Jin Kim),김민철(Min-Chul Kim),이봉상(Bong-Sang Lee) 대한기계학회 2006 대한기계학회 춘추학술대회 Vol.2006 No.3
In ductile-brittle transition temperature(DBTT) region of low alloyed steels, two fracture mechanisms are in competition ductile fracture characteristic for high temperatures and transgranular cleavage characteristic for low temperature. Also, scatters of fracture toughness data and transferability problems among different configurations were pointed out as obstacles for application of PCVN(pre-cracked V-notch) specimens despite their efficiency. In this paper a procedure for the determination of the Weibull parameters m and σ<SUB>u</SUB> is developed. This procedure consists of two parts. The first part is the determination of the plastic zone ahead of the crack tip based on the finite element analysis. And the second part is the estimation of the parameters m and σ<SUB>u</SUB> using the maximum likelihood method. The paper concludes with calibrations of both m and σ<SUB>u</SUB> over the DBT region using maximum likelihood method and the fracture toughness data sets for an SA508 pressure vessel steel.
가압열충격을 받는 원자로압력용기의 확률론적 건전성 해석
김종욱(Jong-Wook Kim),허남수(Nam-Su Huh),유연식(Yeon-Sik Yoo),김태완(Tae-Wan Kim) 대한기계학회 2008 대한기계학회 춘추학술대회 Vol.2008 No.11
The objective of this study is to evaluate the integrity for a reactor pressure vessel under the pressurized thermal shock by applying the probability fracture mechanics. A semi-elliptical axial crack is assumed to be in the beltline region of the reactor pressure vessel. The selected random variables are the neutron fluence on the vessel inside surface, the content of copper, nickel, and phosphorus in the reactor pressure vessel material, and initial RTNDT. The probabilistic integrity analysis was performed using the Monte Carlo simulation.