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한국표준형 원전 증기발생기 전열관 축방향 ODSCC 발생원인 분석
김홍덕,박수기,임창재,정한섭,Kim, Hong-deok,Park, Su-ki,Yim, Chang Jae,Chung, Han Sub 한국압력기기공학회 2010 한국압력기기공학회 논문집 Vol.6 No.1
Domestic nuclear steam generators with Alloy 600 HTMA tubes have experienced axial cracking at eggcrate tube support plates(TSPs). The axial stress corrosion cracks were observed at the crevice between outside of tubes and eggcrate TSPs. The root cause of axial cracking was investigated by thermal hydraulic analysis and sludge distribution diagnosis. It is suggested that deposition of sludge at eggcrate TSPs could increase the outside surface temperature of tube and promote the enrichment of impurities at crevice, and thus accelerate cracking. Additionally strategy for reducing the sludge ingress to steam generators is discussed.
CANDU형 원전 압력관에 존재하는 축방향 균열의 응력확대계수
이국희,오영진,박흥배,정한섭,정하주,김윤재,Lee, Kuk-Hee,Oh, Young-Jin,Park, Heung-Bae,Chung, Han-Sub,Chung, Ha-Joo,Kim, Yun-Jae 한국압력기기공학회 2011 한국압력기기공학회 논문집 Vol.7 No.1
CANDU reactor core is composed a few hundreds pressure tubes, which support and locate the nuclear fuels in the reactor. Each pressure tube provides pressure boundary and flow path of primary heat transport system in the core region. In order to guarantee the structural integrity of pressure tube flaws which can be found by in-service inspection, crack growth and fracture initiation assessment have to be performed. Stress intensity factors are important and basic information for structural integrity assessment of planar and laminar flaws (e. g. crack). This paper reviews and confirms the stress intensity factor of axial crack, proposed in CSA N285.8-05, which is an fitness-for-service evaluation code for pressure tubes in CANDU nuclear reactors. The stress intensity factors in CSA N285.8-05 were compared with stress intensity factors calculated by three methods (finite element results, API 579-1/ASME FFS-1 2007 Fitness-For-Service and ASME Boiler and Pressure Vessel Code Section XI). The effects of Poisson's ratio and anisotropic elastic modulus on stress intensity factors were also discussed.
물-공기 횡류시 U 자형 튜브 다발에서의 유체탄성불안정
주인철(In-Cheol Chu),정흥준(Heung June Chung),이창희(Chang Hee Lee),윤영중(Young Jung Yun),정한섭(Han-Sub Chung),변형현(Hyung Hyun Byun),김무용(Moo Yong Kim),문효익(Hyo Ik Moon),이희남(Hui Nam Rhee) 대한기계학회 2006 대한기계학회 춘추학술대회 Vol.2006 No.11
In the present study, a series of experiments have been performed to investigate a fluid-elastic instability of an U-tube bundle in air-water two-phase cross-flow. A total of 39 prototypic U-bend tubes are arranged in a rotated square array with a p/d of 1.633, which is identical to U-bend tube bundle of OPR1000 steam generators. The present experimental facility has 2-span U-tubes in contrast to 9-span U-tubes of OPR1000 steam generators. However, modal analysis shows that the major vibration mode and corresponding natural frequencies are almost same to the full 9-span U-tubes. A total of 12 3-axis acceleromters are installed inside U-tubes to monitor a precise vibration motions. The following parameters were obtained throughout a series of experiments: tube vibration responses and critical velocity for fluid-elastic instability, two-phase damping ratio, hydrodynamic mass. Finally, the instability factor (K) of Connors’ relation was evaluated based on the above measured parameters.
다변량 로지스틱 회귀분석을 이용한 증기발생기 전열관 ODSCC의 POD곡면 분석
이재봉(Jae Bong Lee),박재학(Jai Hak Park),김홍덕(Hong-Deok Kim),정한섭(Han-Sub Chung) 대한기계학회 2007 대한기계학회 춘추학술대회 Vol.2007 No.5
Steam generator tubes play an important role in safety because they constitute one of the primal)' barriers between the radioactive and non-radioactive sides of the nuclear power plant. For tins reason, the integrity of file tubes is essential in minimizing the leakage possibility of radioactive water, The integrity of the tubes is evaluated based on NDE (non-destructive evaluation) inspection results. Especially ECT (eddy current test) method is usually used for detecting the flaws in steam generator tubes. However, detection capacity of the NDE is not perfect and all of the real flaws which actually existing in steam generator tubes is not known by NDE results. Therefore reliability of NDE system is one of tile essential parts in assessing tile integrity of steam generators. In this study POD (probability of detection) of ECT system for ODSCC in steam generator tubes is evaluated using multivariate logistic regression. The cracked tube specimens are made using the withdrawn steam generator tubes. Therefore the cracks are not artificial but real. Using the multivariate logistic regression method, continuous POD surfaces are evaluated from hit (detection) and miss (no detection) binary data obtained from destructive and non-destructive evaluation of tile cracked tubes. Length and depth of cracks are considered in multivariate logistic regression and their effects on detection capacity are evaluated.
증기발생기의 주기적 비파괴검사 자료와 유효POD를 이용한 물리적 결함수의 추정
이재봉(Jae Bong Lee),박재학(Jai Hak Park),김홍덕(Hong-Deok Kim),정한섭(Han-Sub Chung) 대한기계학회 2008 대한기계학회 춘추학술대회 Vol.2008 No.5
It is necessary to know the number of flaws and their size distribution in order to calculate the probability of failure or to estimate the amount of leakage through the tube wall of steam generators. But in-service inspection (ISI) flaw data is different from the physical flaw data. In case of a single inspection, it is easy to estimate the number of physical flaws using the POD curve. However, we may be faced with some difficulties in obtaining the number of physical flaws from the periodic in-service inspection data. In this study a method for estimating the number of physical flaws from periodic in-service inspection data is proposed. In order to calculate the number of physical flaws with periodic ISI data, both probabilities of detecting and missing flaws should be considered. And flaw initiation and growth history must be known also. The flaw initiation and growth history can be inferred from appropriate probabilistic flaw growth rate. Two inference methods are proposed and compared. One is Monte Carlo simulation method and the other is transition (stochastic) matrix method. The effective POD, the total possibility of detection considering both probabilities of detecting and missing flaws for each flaw size, can be calculated using above two inference methods. And two methods are compared and the usefulness and convenience are evaluated from several applications.
Monte Carlo 방법을 이용한 증기발생기 전열관 축방향 균열의 파열확률
이재봉(Jae Bong Lee),박재학(Jai Hak Park),김홍덕(Hong-Deok Kim),정한섭(Han-Sub Chung),김태룡(Tae Ryong Kim) 대한기계학회 2006 대한기계학회 춘추학술대회 Vol.2006 No.3
A statistical assessment model for structural integrity of steam generator tubes was proposed using Monte Carlo method. The growth of axial cracks in steam generator tubes is predicted by statistical approaches. The statistical parameters that represent the characteristics of crack growth and initiation were derived from in-service inspection (ISI) non-destructive evaluation (NDE) data. Based on the statistical approaches, crack growth models were proposed and applied to predict distribution of crack size at the end of cycle (EOC). The probabilistic crack growth rate was calculated from the in-service non-destructive inspection data. And the statistical growth of crack was simulated using the Monte Carlo method. The burst pressure for each predicted flaw at EOC is calculated using correlation between burst pressure and crack size. Probabilistic distributions of the crack size and the probability of burst were obtained from numerously repeated simulations using the proposed assessment model.
김현수(Hyun-Su Kim),진태은(Tae-Eun Jin),김홍덕(Hong-Deok Kim),정한섭(Han-Sub Chung),장윤석(Yoon-Suk Chang),김영진(Young-Jin Kim) 대한기계학회 2008 대한기계학회 춘추학술대회 Vol.2008 No.5
Since the structural integrity of thin-walled tubes in the nuclear heat exchangers is crucial from the viewpoint of safety and reliability, the integrity evaluation for cracked tubes is quite important. Accurate estimation of the failure load is a key element of the structural integrity assessment. In this paper, three-dimensional finite element analyses are carried out for tubes with various sizes of circumferential through-wall cracks in order to determine the failure load under combined loading condition. The analysis results can be directly applied to the practical integrity assessment of cracked heat exchanger tubes, because the comparison between experimental data and finite element analysis results shows a good agreement.
신규인(Kyu In Shin),박재학(Jai Hak Park),김홍덕(Hong Deok Kim),정한섭(Han Sub Chung),정명조(Myung Jo Jhung),최영환(Young Hwan Choi) 대한기계학회 2003 대한기계학회 춘추학술대회 Vol.2003 No.8
Steam generator tubes experience widespread degradation such as stress corrosion cracking, wear, tube rupture, denting, fatigue and so on. The resulting damages can cause tube bursting or leak of the primary water which contains radioactivity. Therefore the allowable size of the damage is required to be determined on the maintenance purpose. The burst pressure of a tube with a T-type combination crack consisting of longitudinal and circumferential cracks is obtained experimentally and analytically. Fracture parameters such as stress intensity factor and crack opening angle are investigated. And tubesheet effect with a T-type combination crack is considered by using the crack opening angle. Also, the burst pressure for a T-type combination crack is compared with that of a single longitudinal crack to develop a length-based criteria.
Monte Carlo 방법을 이용한 Model F 증기발생기 전열관 AVB 마모의 성장 및 생성에 대한 확률론적 예측
이재봉(Jae Bong Lee),박재학(Jai Hak Park),김홍덕(Hong-Deok Kim),정한섭(Han-Sub Chung),김태룡(Tae Ryong Kim) 대한기계학회 2005 대한기계학회 춘추학술대회 Vol.2005 No.11
The growth of AVB wear in Model F steam generator tubes is predicted using the Monte Carlo Method and statistical approaches. The statistical parameters that represent the characteristics of wear growth and wear initiation are derived from in-service inspection (ISI) non-destructive evaluation (NDE) data. Based on the statistical approaches, wear growth model are proposed and applied to predict wear distribution at the end of cycle (EOC). Probabilistic distributions of the number of wear flaws and maximum wear depth at EOC are obtained from the analysis. Comparing the predicted EOC wear flaw data with the known EOC data the usefulness of the proposed method is examined and satisfactory results are obtained.