Aspects of Preliminary Probabilistic Safety Assessment for a Research Reactor in the Conceptual Design Phase

이윤환,Lee, Yoon-Hwan The Korean Society of Safety 2019 한국안전학회지 Vol.34 No.3

This paper describes the work and results of the preliminary Probabilistic Safety Assessment (PSA) for a research reactor in the design phase. This preliminary PSA was undertaken to assess the level of safety for the design of a research reactor and to evaluate whether it is probabilistically safe to operate and reliable to use. The scope of the PSA described here is a Level 1 PSA which addresses the risks associated with core damage. After reviewing the documents and its conceptual design, eight typical initiating events are selected regarding internal events during the normal operation of the reactor. Simple fault tree models for the PSA are developed instead of the detailed model at this conceptual design stage. A total of 32 core damage accident sequences for an internal event analysis were identified and quantified using the AIMS-PSA. LOCA-I has a dominant contribution to the total CDF by a single initiating event. The CDF from the internal events of a research reactor is estimated to be 7.38E-07/year. The CDF for the representative initiating events is less than 1.0E-6/year even though conservative assumptions are used in reliability data. The conceptual design of the research reactor is designed to be sufficiently safe from the viewpoint of safety.

담배식물(植物)의 엽서별(葉序別) 질산환원능력(窒酸還元能力) 비교(比較)

이윤환,임선욱,Lee, Yun-Hwan,Lim, Sun-Uk 한국토양비료학회 1987 한국토양비료학회지 Vol.20 No.1

질산태질소(窒酸態窒素)를 선택흡수(選擇吸收)하는 담배식물에 대하여 흡수된 $NO_3-N$의 각조직별(各組織別) 이동양상(移動樣相)과 질산환원효소(窒酸還元酵素)의 활성도(活性度)(nitrate reductase activity. NRA)를 조사하고 생육과정(生育過程)에서 출엽(出葉)된 잎들의 질산환원능력(窒酸還元能力)을 비교조사(比較調査)한 결과(結果) 1. 도관조직(導管組織)인 엽맥(葉脈)까지는 함유(含有)된 질소(窒素)의 대부분(大部分)이 $NO_3-N$으로써 무기태질소(無機態窒素)로 엽맥(葉脈)을 통과(通過)하며 엽육(葉肉)에서는 $NO_3-N$이 환원(還元)되어 무기태질소(無機態窒素)가 거의 검출(檢出)되지 않았다. 2. NRA는 성숙(成熟)된 잎에서 가장 왕성하였으며 분열생장중(分裂生長中)인 잎이나 도관조직(導管組織)에서는 환원기능이 매우 낮은 수준에 머물렀다. 3. 하위(下位)의 성숙엽(成熟葉)은 두껍고 수분(水分)을 많이 함유(含有)하였으며 가장 왕성한 질산환원능력(窒酸還元能力)을 보였다. 4. 생장조직(生長組織)으로 유기질소물질(有機窒素物質)을 공급(供給)하기 위하여 유식물(幼植物)때는 소수(小數)의 좁은 잎에서 높은 수준(水準)의 NRA를 유지(維持)했으나 생육(生育)이 진전되어 많은 잎이 착엽(着葉)되면서 상위(上位)쪽의 성숙엽(成熟葉)은 NRA가 낮은 수준에 머물렀다. Nitrate nitrogen was absorbed dominantly among the inorganic nitrogen nutrients by tobacco plant. Transport and reduction of $NO_3-N$ in plant tissue were the important metabolism for supplying synthetic N compounds to developing tissues during growth period. Under field and environment-controlled condition tobacco plants were grown and seperated to leaf tissues at stalk positions for investigation of nitrogen transport and assimilation ability during period of rapid vegative growth. The results of studies were summarized as follows: 1. $NO_3-N$ absorbed from roots was transported as inorganic nitrogen through the vascular tissue of leaf veins as resulting from the high $NO_3-N$ ratio of the nitrogen content in leaf veins, but these ratios in mesophyll tissue of the same leaf laminae decreased remarkably in disregard of higher accumulation of nitrogen being compared to midvien. 2. Mesophyll tissue of mature leaves appeared higher value of nitrate reductase activity (NRA) comparing with other tissues, stem, leaf vien, and meristmatic tissue at emergence point with young leaves. 3. Matured leaves at lower position being reducing nitrate nitrogen vigorously observed thick laminae and kept high amount of water in them. 4. Mature leaves of young plant reduced $NO_3-N$ vigorously for supply synthetic N compounds to meristmatic tissues at growing point by the reason of narrow and few leaves at young stage, but in advancing growth period NRA of mature leaves along upper position reached to lower value. This appearence attributed to distribution of organic-N compound demanding for growth to increasing numbers of wide leaves.

Lymphatic vessel mapping in the upper extremities of a healthy Korean population

이윤환,Soo-Hyun Lee,Hi-Jin You,Jae-A Jung,Eul-Sik Yoon,Deok-Woo Kim 대한성형외과학회 2018 Archives of Plastic Surgery Vol.45 No.2

Background Intraoperative indocyanine green (ICG) lymphography can effectively detect functioning lymph vessels in edematous limbs. However, it is sometimes difficult to clearly identify their course in later-stage edematous limbs. For this reason, many surgeons rely on experience when they decide where to make the skin incision to locate the lymphatic vessels. The purpose of this study was to elucidate lymphatic vessel flow patterns in healthy upper extremities in a Korean population and to use these findings as a reference for lymphedema treatment. Methods ICG fluorescence lymphography was performed by injecting 1 mL of ICG into the second web space of the hand. After 4 hours, fluorescence images of lymphatic vessels were obtained with a near-infrared camera, and the lymphatic vessels were marked. Three landmarks were designated: the radial styloid process, the mid-portion of the cubital fossa, and the lower border of the deltopectoral groove. A straight line connecting the points was drawn, and the distance between the connected lines and the marked lymphatic vessels was measured at 8 points. Results There were 30 healthy upper extremities (15 right and 15 left). The average course of the main lymph vessels passed 26.0±11.6 mm dorsal to the styloid process, 5.7±40.7 mm medial to the mid-cubital fossa, and 31.3±26.1 mm medial to the three-quarters point of the upper landmark line. Conclusions The main functioning lymphatic vessel follows the course of the cephalic vein at the forearm level, crosses the mid-cubital point, and travels medially toward the mid-axilla.

리스크정보 최적화를 통한 국내 연구용원자로의 안전성 향상

이윤환,장승철,Lee, Yoon-Hwan,Jang, Seung-Cheol 한국안전학회 2022 한국안전학회지 Vol.37 No.2

This paper describes an attempt to improve and optimize the operational safety level of a domestic research reactor by conducting a probabilistic safety assessment (PSA) under full-power operating conditions. The PSA was undertaken to assess the level of safety at an operating research reactor in Korea, to evaluate whether it is probabilistically safe and reliable to operate, and to obtain insights regarding the requisite procedural and design improvements for achieving safer operation. The technical objectives were to use the PSA to identify the accident sequences leading to core damage, and to conduct sensitivity analyses based thereon to derive insights regarding potential design and procedural improvements. Based on the dominant accident sequences identified by the PSA, eight types of sensitivity analysis were performed, and relevant insights for achieving safer operation were derived. When these insights were applied to the reactor design and operating procedure, the risk was found to be reduced by approximately ten times, and the safety was significantly improved. The results demonstrate that the PSA methodology is very effective for improving reactor safety in the full-power operating phase. In particular, it is a highly suitable approach for identifying the deficiencies of a reactor operating at full power, and for improving the reactor safety by overcoming those deficiencies.

국내 연구용원자로 전출력 내부사건 1단계 확률론적안전성평가

이윤환,장승철,Lee, Yoon-Hwan,Jang, Seung-Cheol 한국안전학회 2021 한국안전학회지 Vol.36 No.3

This report documents the results of an at-power internal events Level 1 Probabilistic Safety Assessment (PSA) for a Korea research reactor (KRR). The aim of the study is to determine the accident sequences, construct an internal level 1 PSA model, and estimate the core damage frequency (CDF). The accident quantification is performed using the AIMS-PSA software version 1.2c along with a fault tree reliability evaluation expert (FTREX) quantification engine. The KRR PSA model is quantified using a cut-off value of 1.0E-15/yr to eliminate the non-effective minimal cut sets (MCSs). The final result indicates a point estimate of 4.55E-06/yr for the overall CDF attributable to internal initiating events in the core damage state for the KRR. Loss of Electric Power (LOEP) is the predominant contributor to the total CDF via a single initiating event (3.68E-6/yr), providing 80.9% of the CDF. The second largest contributor is the beam tube loss of coolant accident (LOCA), which accounts for 9.9% (4.49E-07/yr) of the CDF.

국내 연구용원자로 PSA 수행을 위한 초기사건 선정 및 빈도 분석

이윤환,Lee, Yoon-Hwan 한국안전학회 2021 한국안전학회지 Vol.36 No.2

This paper presents the results of an initiating event analysis as part of a Level 1 probabilistic safety assessment (PSA) for at-power internal events for the Korea Research Reactor (KRR). The PSA methodology is widely used to quantitatively assess the safety of research reactors (RRs) in the domestic nuclear industry. Initiating event frequencies are required to conduct a PSA, and they considerably affect the PSA results. Because there is no domestic database for domestic trip events, the safety of RRs is usually assessed using foreign databases. In this paper, operating experience data from the KRR for trip events were collected and analyzed in order to determine the frequency of specific initiating events. These frequencies were calculated using two approaches according to the event characteristics and data availability: (1) based on KRR operating experience or (2) using generic data.

2상류이젝터를 이용하는 $CO_{2}$ 냉동사이클의 성능해석

이윤환,Lee Yoon-Hwan 한국마린엔지니어링학회 2005 한국마린엔지니어링학회지 Vol.29 No.8

The $CO_{2}$ refrigeration cycle is expected to reduce the compressor work and increase the COP by applying two-phase ejector as a device for the recovery of dissipated expansion energy. In this study, the performance of the cycle was simulated and effects of the ejector shapes on the performance of the $CO_{2}$ refrigeration cycle were investigated. The following results were obtained through the cycle simulation. The COP of the $CO_{2}$ refrigeration cycle with two-phase ejector flow which expansion is occured in the isentropic manner is increased by a maximum of 24 $\%$ than the basic cycle with expansion valve If the velocity nonequilibrium in the mixing process is assumed the COP of the cycle is increased with the increase of the length and the decrease of the section area of the mixing tube. The best cycle performance is obtained when the divergent angle of diffuser is 7.

Dose Weight loss and Core Exercise improve Oswestry disability index, Trunk Extensor and Flexor Muscle Strength in Obese Middle-Aged Women with Chronic Low Back Pain?

이윤환(Yun-Hwan Lee),김철호(Chul-Ho Kim),이광지(Jea-Kwang Lee),이지은(Ji-Eun Lee),이호성(Ho-Seong Lee) 대한운동학회 2024 아시아 운동학 학술지 Vol.26 No.1

OBJECTIVES The purpose of this study was to investigate the weight loss and isotonic core exercise on oswestry disability index (ODI), trunk extensor and flexor muscle strength in obese middle-aged women with chronic low back pain. METHODS Eighteen obese middle-aged woman with chronic low back pain were randomly assigned into weight loss + core exercise group (WL+CE, n=6), core exercise group (CE, n=6), and control group (CON, n=6). The weight loss goal was set at approximately 0.5-1 kg per week, and core exercises were conducted for 60 minutes, three times a week, for 8 weeks. Body composition (weight, % body fat, muscle mass, WHR), ODI, trunk extensor and flexor muscle strength were measured before, 4 weeks, and 8 weeks after core exercise. RESULTS WHR and ODI significantly decreased at 4 and 8 weeks of exercise in both the WL+CE and CE groups compared to before exercise (p<.05, respectively). Trunk extensor muscle strength significant increased at 8 weeks after exercise compared to before exercise at 146°, 158°, 170°, and 182° in the WL+CE (p<.05, respectively), and significant increased at 8 weeks after exercise compared to before exercise at 146° and 158° in the CE (p<.05, respectively). Trunk flexor muscle strength was a significant increase at 8 weeks after exercise compared to before exercise at 146°, 158°, and 182° in the WL+CE (p<.05, respectively), and significant increase at 8 weeks after exercise compared to before exercise at 110°, 134°, 146°, and 170° in the CE (p<.05, respectively). CONCLUSIONS The results of this study suggest that weight loss and core exercise improve WHR, ODI, and trunk extensor and flexor muscle strength in obese middle-aged women with chronic low back pain.

수면 유형에 따른 체중부하운동이 사무직 중년여성의 신체조성, 1 RM 근력, 체력 및 수면의 질에 미치는 영향

이완재 ( Wan-jae Lee ),이윤환 ( Yun-hwan Lee ),이지은 ( Ji-eun Lee ),이호성 ( Ho-seong Lee ) 한국체육대학교 체육과학연구소 2023 스포츠사이언스 Vol.41 No.3

이 연구에서는 수면 유형에 따른 체중부하운동이 사무직 중년여성의 신체조성, 1 RM 근력, 체력 및 수면의 질에 미치는 영향을 알아보는데 그 목적이 있다. 18명의 사무직 중년여성을 대상으로 아침형 집단(MNG) 8명, 저녁형 집단(ENG) 8명으로 구분하였다. 체중부하운동은 8주, 주 2회 및 50분 동안 진행하였으며, 신체조성(weight, BMI, MM, BFM, BFP, WHR), 1 RM 근력(BP, LP), 체력(3MST, SR, AS, PU, CU, GS) 및 수면의 질(K-PSQI)은 체중부하운동 전, 4주 및 8주 후에 측정하였다. 1 RM 근력(BP, LP) 및 체력(3MST, SR, AS, PU, CU, GS)은 MNG 및 ENG에서 체중부하운동 전과 비교해서 4주 및 8주 후에 유의하게 증가하였으며. 수면의 질(PSQI)은 MNG에서 체중부하운동 전과 비교해서 4주 및 8주 후에 유의하게 감소하였다. 따라서 이 연구에서는 체중부하운동은 MNG 및 ENG의 1 RM 근력 및 체력을 향상시키며, MNG의 수면의 질을 개선시켰다. The purpose of this study was to investigate the effects of weight-bearing exercise according to chronotype on body composition, 1 RM muscle strength, physical fitness and sleep condition in middle-aged office workers. Eighteen middle-aged woman were randomly assighned to the morningness group (MNG, n = 8) and the eveningness group (ENG, n = 8). All subjects engaged in weight-bearing exercsie for 50 minutes, twice a week, for 8 weeks. Body composition (weight, BMI, MM, BFM,BFP and WHR), 1 RM strength (BP, LP), physical fitness (3MST, SR, AS, PU, CU, and GS) and sleep quality (K-PSQI) were measured before, 4 weeks, and 8 weeks after weight-bearing exercise. 1 RM strength (BP, LP) and Physical fitness (3MST, SR, AS, PU, CU, and GS) were significantly improved in the MNG and ENG (p < 0.05). K-PSQI was significantly improved in the MGN (p < 0.05). This study indicated that weight-bearing exercise had positive effects on physical fitness in MNG and ENG. In particular, weight-bearing exercise was more effective on sleep quality in MGN than in ENG. These results suggest that MNG may benefit from weight-bearing exercise at night for improve sleep quality.

담배식물의 이온均衡에 미치는 形態別 窒素의 영향

李允渙(Yun-Hwan Lee) 한국토양비료학회 1986 한국토양비료학회지 Vol.19 No.2