고온 화력 P91강 재열증기배관의 건전성 제고 방안

이형연,이제환,최현선 한국압력기기공학회 2020 한국압력기기공학회 논문집 Vol.16 No.1

A number of so-called ‘Type IV’ cracking was reported to occur at the welded joints of the P91 steel or P92 steel reheat steam piping systems in Korean supercritical thermal power plants. The reheat steam piping systems are subjected to severe thermal and pressure loading conditions of coolant higher than 570C and 4MPa, respectively. In this study, piping analyses and design evaluations were conducted for the piping system of a specific thermal plant in Korea and suggestions were made how structural integrity could be improved so that type IV cracks at the welded joints could be prevented. Integrity evaluations were conducted as per ASME B31.1 code with implicit consideration of creep effects which was used in original design of the piping system and as per nuclear-grade RCC-MRx code with explicit consideration of creep effects. Comparisons were made between the evaluation results from the two design rules. Another approach with modification or reduction of the redundant supports in the piping systems was investigated as a tool to mitigate thermal stresses which should essentially contribute to prevention of Type IV cracking without major modification of the existing piping systems. In addition, a post weld heat treatment method and repair weld method which could improve integrity of the welded joint of P91 steel were investigated.

면진된 KALIMER 원자로 구조물의 내진설계 및 지진해석

이형연,구경희,유봉 한국지진공학회 1999 한국지진공학회논문집 Vol.3 No.1

본 연구에서는 현재 국내에서 면진설계를 적용하여 개발중인 KALIMER(Korea Advanced Llquid Metal Reactor) 액체금속로에 대한 내진설계 및 지진해석을 위하여 핵심구조물인 원자로구조물에 대한 단순 지진해석모델을 개발하였다 이를 이용하여 면진설계의 경우와 비면진 설계의 경우에 대한 동특성분석과 시간이력 지진해석을 수행하여 비교평가하였다. 또한 ASME 설계코드에 따른 응력한계요건을 검토하기 위하여 등가 지진응력해석을 수행하고 이로부터 내진여유도를 계산하였다 지진안전성에 대한 하나의 지표로서 원자로 구조물이 견딜수 있는 최대지진하중을 결정하기 위한 한계지진하중(Limit seismic load)을 저의하였다 지진해석결과 면진된 KALIMER 원자로구조믈은 비면진된 경우에 비하여 가속도응답과 구조물간의 상대변위응답이 현저히 감소하였고 충분한 내진여유도로 인하여 한계지진하중이 0.8g로 나타났다. In this paper, the seismic analysis model for seismically isolated KALIMER reactor structures is developed and the modal analysis and the seismic time history analysis are carried out for seismic isolation and non-isolation cases. To check the seismic stress limit according to the ASME Code, the equivalent seismic stress analyses are preformed using the 3-D finite element model. From the seismic stress analysis, the seismic margins are calculated for structural members. The limit of seismic load is defined to show that the maximum input acceleration ensures the structural safety for seismic load. In comparison of seismic responses between seismic isolation and non-isolation cases, the seismic isolation design gives significantly reduced acceleration responses and relative displacements between structures. The seismic margin of KALIMER reactor structure is high enough to produce the limit seismic load 0.8g.

가중함수법을 이용한 두꺼운 배관의 응력강도계수 계산 ( Calculation of Stress Intensity Factors for a Thick Pipe Using Weight Function Method )

이형연,김종범,유봉 대한기계학회 1995 대한기계학회 춘추학술대회 Vol.- No.-

아스피린 유발성 기관지 천식 환자에서의 아스피린 탈감작 치료 2예

이형연,윤형진,김성철 동국대학교 경주대학 1993 東國論集 Vol.12 No.-

Some asthma patients are intolerant to aspinin.In these patients ingestion of aspirin causesymptoms of rhinitis, and/or urticaria, bronchospasm whthin 1 to 2 hours, which may be fatal. We conducted oral aspirin test and desensitization in two patients with aspirin induced asthma. One of these patients was admitted due to acute asthmatic attack which develop after ingestion of one tablet(500mg) of aspirin, which followed by acute repiratory failure with cyanosis and severe hypoxia which needed intubation and ventilatory care. And the other was occasionally experienced rhinorrhea, generalized itching and dyspnea after the URI medications including aspirin. They were received increasing doses of aspirin in every two hours until a fall in FEV_1 of 20% and experience asthmatic episode. Asprin desensitization, defined as the ability of the patients to ingest 650mg of aspirin, was successfullly achieved with careful managements at third day of aspirin administration. After desensitization the patient can be tolerant 650mg aspirin of without experiencing respiratory symptoms or decreasing in lung function. These two patients could be successfully desensitized to aspirin with safety. Even though there is no exact mechanism about asprin intolerance, most likely to be related to the ability of aspirin to inhibit cyclooxygenase pathway. Therefore enhanced lipoxygenase metabolism perhaps plays a crucial role. Aspirin desensitization enable the aspirin sensitive patients to use aspirin or other NSAIDs with safety.

가중함수법을 이용한 두꺼운 배관의 응력강도계수 계산

이형연,이재한,유봉,Lee, Hyeong-Yeon,Lee, Jae-Han,Yoo, Bong 대한기계학회 1996 大韓機械學會論文集A Vol.20 No.7

An approximate weight function technique using the indirect boundary integral equation has been presented for the analysis of stress intensity foactors(SIFs) of a thick pipe. One-term boundary integral was introduced to represent the crack surface displacement field for the displacement based weight function technique. An explicit closed-form SIF solution applicable to symmetric cracked pipes without any modification of the solution including both circumferential and radial cracks has been derived. The necessary information in the analysis is two or three reference SIFs. In most cases the SIF solution were in good agreement with those available in the literature.

내열강 소재 및 고온 설계 기술

이형연,이제환,허남수 대한기계학회 2020 기계저널 Vol.60 No.8

열시효가 Mod.9Cr-1Mo강의 재료강도 및 파괴 거동에 미치는 영향

이형연,김우곤,손석권,홍석우,석창성,Lee, Hyeong-Yeon,Kim, Woo-Gon,Son, Seok-Kwon,Hong, Suk Woo,Seok, Chang Sung 대한기계학회 2016 대한기계학회 논문집. Transactions of the KSME. C, 산업기술과 혁신 Vol.4 No.2

발전소 내열강의 물성치는 고온 가동시간이 누적됨에 따라 열시효의 영향을 받는다. 본 연구에서는 제 4 세대 원자력시스템의 재료로 널리 채택되고 있는 Mod.9Cr-1Mo (ASME Grade 91)강을 대상으로 항복강도, 인장강도 및 파괴거동에 열시효가 미치는 영향에 대해 조사 및 분석하였다. 국내에서 가동 중인 초초임계(USC) 화력발전소의 배관계통에서 채취한, 73,716 시간의 가동 이력을 겪은 Gr.91 강 재료가 재료 실험을 위해 사용되었고, 동 시험결과와 가동 이력을 겪지 않은 신재의 시험결과를 비교 분석하였다. 또한 ASME 코드의 물성치와 RCC-MRx 의 물성치와 비교 분석하였고, 이들 설계기술기준 물성치의 보수성은 신재 및 가동 이력을 겪은 재료의 시험결과와 비교 분석을 통해 정량화하였다. The material properties of heat resistant materials at power plants are affected by thermal aging as operating time is accumulated. In this study, the influence of thermal aging on yield strength, tensile strength and fracture behavior for Mod.9Cr-1Mo (ASME Grade 91) steel which is a material widely adopted for Generation IV nuclear energy system has been investigated and analyzed. Service exposed Gr.91 steel materials sampled from a piping system of an ultra-supercritical (USC) plant in Korea with accumulated operation time of 73,716 hours were used for material testing. The test results of the service exposed material specimens were compared with those of the virgin Gr.91 steel specimens. Those test data were compared with the material properties of ASME code and RCC-MRx code. Conservatisms of the material properties in the design codes have been quantified based on the comparisons of those from virgin and service exposed material specimens.

316L 스테인리스강 원통 구조물의 열라체팅 변형 시험 및 해석

이형연,김종범,이재한,Lee, Hyeong-Yeon,Kim, Jong-Bum,Lee, Jae-Han 대한기계학회 2002 大韓機械學會論文集A Vol.26 No.3

In this study, the progressive inelastic deformation, so called, thermal ratchet phenomenon which can occur in high temperature structures of liquid metal reactor was simulated with thermal ratchet structural test facility and 316L stainless steel test cylinder. The thermal ratchet deformation at the reactor baffle cylinder of the liquid metal reactor can occur due to the moving temperature distribution along the axial direction as the sodium free surface moves up and down under the cyclic heat-up and cool-down transients. The ratchet deformation was measured with the laser displacement sensor and LVDTs after cooling the structural specimen which is heated up to 55$0^{\circ}C$ with steep temperature gradients along the axial direction. The temperature distribution of the test cylinder along the axial direction was measured with 28 channels of thermocouples and was used for the ratchet analysis. The thermal ratchet deformation was analyzed with the constitutive equation of nonlinear combined hardening model which was implemented as ABAQUS user subroutine and the analysis results were compared with those of the test. Thermal ratchet load was applied 9 times and the residual displacement after 9 cycles of thermal load was measured to be 1.79mm. The ratcheting deformation shapes obtained by the analysis with the combined hardening model were in reasonable agreement with those of the structural tests.

응급실에 내원한 파상풍 환자의 임상 양상 및 예후 영향 인자 분석

이형연,문정미,민용일,전병조,고양석,이병국 대한응급의학회 2007 대한응급의학회지 Vol.18 No.2

Purpose: Tetanus is difficult for emergency physician to diagnosis at an early stage because of its low incidence and atypical initial clinical features. Therefore, we reviewed the clinical features of 54 tetanus cases and attempted to identify factors associated with prognosis in order to improve early diagnosis and treatment. Methods: We carried out a retrospective chart review of 54 adult tetanus patients who presented to the ED of Chonnam National University Hospital between January 1996 and December 2005. We collected information on demographics, SAPS II score, clinical feature, course of infection and prognosis. We divided the patients to two groups according to the survival and compared their data statistically. Results: Fifty four patients, 33 men and 21 women, were included in the study. The mean age was 50.97±15.95. The most common initial diagnosis in ED were electrolyte imbalance (n=15), neck and facial dystonia (n=9). The mean incubation period was 10.27±6.47 days. The initial SPAS II score 17.29±8.45 and the Wood score was 3.12 ±1.47. Most commonly symptom was dyspnea and dysarthria. Twenty one patients were supported by mechanical ventilation, and the duration of mechanical ventilation was 5.92±4.52 days. On multivariate logistic regression analysis, four variables were found to be associated with the prognosis: incubation period, Wood score, Time interval from initial symptom to mechanical ventilation, initial SAPS II. Conclusion: Four variables correlated well with the prognosis: Incubation period, Wood score, Time interval from initial symptom to mechanical ventilation, initial SAPS II score.

316L 시험원통의 열라체팅 구조시험에 관한 연구 ( A Study on Thermal Ratcheting Structure Test of 316L Test Cylinder )

이형연,김종범,구경회 대한기계학회 2001 대한기계학회 춘추학술대회 Vol.1 No.1