Seismic behavior of simplified electrical cabinet model considering cast-in-place anchor in uncracked and cracked concretes

전법규,김성완,장성진,박동욱,이홍표 한국원자력학회 2023 Nuclear Engineering and Technology Vol.55 No.11

In the case of nuclear power plants near end of their design life, a reassessment of the performance of safetyrelated equipment may be necessary to determine whether to shut down or extend the operation of the power plant. Therefore, it is necessary to evaluate the level of performance decline due to degradation. Electrical cabinets, including MCC and switchgear, are representative safety-related equipment. Several studies have assessed the degradation and seismic performance of nuclear power plant equipment. Most of those researches are limited to individual components due to the size of safety-related equipment and test equipment. However, only a few studies assessed the degradation performance of electrical cabinets. The equipment of various nuclear power plants is anchored to concrete foundations, and crack in concrete foundations is one of the most representative of degradation that could be visually confirmed. However, it is difficult to find a study for analysis through testing the effect of cracks in concrete foundations on the response of electrical cabinet internal equipment fixed by anchors. In this study, using a simple cabinet model considering cast-in-place anchor in uncracked and cracked concretes, a tri-axial shaking table tests were performed and the seismic behavior were observed.

Time and Crack Effect on Chloride Diffusion for Concrete with Fly Ash

Sang-Hwa Jung,Hwa-Sung Ryu,Subbiah Karthick,Seung-Jun Kwon 한국콘크리트학회 2018 International Journal of Concrete Structures and M Vol.12 No.2

Nuclear power plants are constructed very close to the marine environments for cooling water and the structures are more susceptible to chloride induced corrosion. Cracking in RC structures in mass concrete is unavoidable when they are exposed to chloride contaminated chemical environments. This study is focused on the evaluation of crack and time effect on chloride diffusion rate. Two types of concrete strength grade were taken for nuclear power plant construction and the crack was induced with varying from 0.05 to 1.35 mm of width. The tests for chloride diffusion coefficients from steady-state condition were performed. The influence of crack width on the chloride transmission behavior was discussed and analyzed over an exposure period to one year. The diffusion coefficients due to growing crack width increase in crack width but they decrease with increasing curing period, which yields 57.8–61.6% reduction at the age of 180 days and 21.5–26.6% of reduction at 365 days. Through the parameters of age and crack width which are obtained from regression analysis, the evaluation technique which can consider the effect of crack and time on diffusion is proposed for nuclear power plant concrete.

원자력발전소 건설현장의 철근콘크리트 공종생산성 및 영향요인 분석

허영기,임진호,김경욱,안영철,오재훈 한국건축시공학회 2014 한국건축시공학회지 Vol.14 No.4

Nuclear power plant projects are being increased all over the world. The construction of nuclear power plants needshuge money and time, which makes conducting a detailed analysis of productivity through the whole process. Reinforced-concrete works productivity field data was collected for more than one year and analyzed from anuclear-power-plant project in Korea. The productivities of formwork, rebar-work, and concrete pouring were 0.54 ㎡/man․day, 0.06 ton/man․day, 1.98 ㎥/man․day, respectively. Moreover, it is revealed that ‘Day of the Week’ is adriver of the formwork activity and ‘Overtime’ is for all of the three. The results will be a great interest of industrypersonnel estimating time and cost of a new nuclear power plant. 특수 플랜트 건설은 타 건설사업보다 체계적인 원가 및공정관리가 요구되지만 이를 위하 반드시 필요한 현장 생산성을 구체적으로 분석한 연구는 이루어지지 않고 있다. 본연구에서는 국내에서 건설중인 특수 플랜트 현장의 철근콘크리트공종을 형틀, 철근, 콘크리트로 나누어 생산성을 측정하고 생산성에 영향을 미치는 요인을 분석하였다. 생산성 측정결과 형틀공종 0.54(㎡/man·time), 철근공종0.06(t/man·time), 콘크리트공종 1.98(㎥/man·time)로나타났다. 영향요인으로는 형틀공종은 요일과 야간적업 유무,철근공종은 야간잡업 유무, 콘크리트공종은 야간작업 유무와콘크리트 물량이 통계적으로 유의게 영향을 미치는 것으로 분석되었다.

Logistical Simulation for On-site Concrete Waste Management in Decommissioning

이의택,데이빗 케슬,김창락 한국방사성폐기물학회 2019 방사성폐기물학회지 Vol.17 No.4

Large amounts of concrete waste are likely to arise from the decommissioning of a Kori-1 nuclear power plant. Several studies have been conducted on decommissioning concrete waste in recent decades, however, they have been limited to contaminated concrete issues or were small pilot-scale experiments. This study constructed two industrial-scale models of on-site concrete waste management for clean as well as contaminated concrete. To evaluate the performance of both the models, simulations were conducted using the Flexsim software. The concrete particle size distribution of Kori-1 and concrete processor properties based on widely used construction equipment were used as sources of input data for the simulations. It was observed that it may take over two years to complete the on-site concrete management processes owing to the performance of existing processors. In addition, it was demonstrated that it is essential to identify bottlenecks in the system and enhance the performance of the relevant processors to avoid delays of the decommissioning schedule. Our results suggest that this novel approach can contribute to developing schedules or expediting delayed activities in the Kori-1 decommissioning project.

Logistical Simulation for On-site Concrete Waste Management in Decommissioning

Lee, Eui-Taek,Kessel, David S.,Kim, Chang-Lak Korean Radioactive Waste Society 2019 방사성폐기물학회지 Vol.17 No.4

Large amounts of concrete waste are likely to arise from the decommissioning of a Kori-1 nuclear power plant. Several studies have been conducted on decommissioning concrete waste in recent decades, however, they have been limited to contaminated concrete issues or were small pilot-scale experiments. This study constructed two industrial-scale models of on-site concrete waste management for clean as well as contaminated concrete. To evaluate the performance of both the models, simulations were conducted using the Flexsim software. The concrete particle size distribution of Kori-1 and concrete processor properties based on widely used construction equipment were used as sources of input data for the simulations. It was observed that it may take over two years to complete the on-site concrete management processes owing to the performance of existing processors. In addition, it was demonstrated that it is essential to identify bottlenecks in the system and enhance the performance of the relevant processors to avoid delays of the decommissioning schedule. Our results suggest that this novel approach can contribute to developing schedules or expediting delayed activities in the Kori-1 decommissioning project.

배합수 냉각방법 및 지연제 사용에 따른 서중 원전콘크리트의 특성

이승한(Lee, Seung-Han),정용욱(Jung, Yong-Wook),장석수(Jang, Seok-Soo),여인동(Yeo, In-Dong),최종오(Choi, Jong-Oh) 한국산학기술학회 2013 한국산학기술학회논문지 Vol.14 No.9

온도차가 극심한 하절기와 동절기 콘크리트 타설의 경우 각종 균열의 발생, 콘크리트 품질불량, 내구성 및 강도저하 등 다양한 문제를 야기 시키고 있다. 특히 원전콘크리트의 경우 대량의 타설로 인한 4계절 연속시공이 이루 어져 서중환경에서 콘크리트 품질관리에 많은 문제점이 발생되고 있는 실정이다. 이에 본 연구에서는 서중환경에서 많이 사용되어지는 프리쿨링 공법 중 배합수 냉각방법과 지연제 사용이 원전콘크리트의 특성에 미치는 영향을 검토 하였다. 배합수 냉각방법은 냉수 5℃와 Ice Flake 50% 치환사용 하였으며, 지연제 사용에 따른 원전콘크리트의 굳지 않은 콘크리트 및 경화 후 콘크리트의 특성을 검토하였다. 굳지 않은 콘크리트 특성으로는 슬럼프, 공기량, 응결시간 및 경화 후 압축강도를 측정하였으며, 단열거푸집을 제작하여 손실되는 열을 최소화시켜 각 온도조건하에서 수화열을 측정하였다. 실험결과, 슬럼프 및 공기량 경시변화 종료시간은 20℃에서 120분, 40℃에서 40분으로 나타났으며, 관입 저항에 의한 응결시간은 배합수 냉각방법 및 지연제 사용 모두 초결과 종결을 지연시키는 것으로 나타났으나, 외기온 도가 상승할수록 지연폭은 감소하는 것으로 나타났다. 수화열은 배합수 냉각방법 모두 최고온도의 저감과 도달시간을 지연시키는 것으로 나타났으나, 지연제 사용의 경우 최고온도 저감효과는 없는 것으로 나타났다. 또한 재령별 압축강 도의 경우 3일, 7일의 초기재령에서 Plain과 비교하여 낮은 강도 값을 나타내었으나, 재령 28일에서는 설계기준강도를 모두 만족시키는 것으로 나타났다. In summer and winter, the difference between the temperature during the day and that during the night is high, which leads to various problems during concrete placement, such as cracks and defects in the concrete as well as low durability and strength. Although nuclear power plant concrete is widely used for placement in all seasons, particular attention must be paid to its quality during the summer. Therefore, we evaluated the effects of a cooling method for mixing water, which is a commonly used hot weather precooling method, and the use of a retarder, on the characteristics of Nuclear Power Plant concrete. In the cooling method for mixing water, cold water at 5 was used, with 50% of the water content consisting of ice flakes. The effects of using a retarder were evaluated by reviewing the characteristics of the cement at the unset stage and after hardening. To evaluate the characteristics of the unset cement, we measured the slump, air volumes, setting times, and pressure strengths after hardening. Furthermore, we measured the heat of hydration at different temperatures; the loss of heat was minimized using insulation. Both the slump time and the complete ageing time of the air volume were found to be 120 min at 20℃ and 40 min at 40℃. In the case when the cooling method for mixing water was used and in the case when a retarder was used, the initial and final sets by penetration resistance were delayed, and the delay decreased with increasing air temperature. For the heat of hydration, the cooling method for mixing water not only lowered the maximum temperature but also delayed its attainment. However, the use of a retarder had no effect on the maximum temperature. Moreover, in the early ages (e.g., 3 and 7 days), the pressure strength of the concrete was lower than that of plain cement. However, the strength of 28-day concrete met the standard construction specifications.

Logistical Simulation for On-site Concrete Waste Management in Decommissioning

한국방사성폐기물학회 한국방사성폐기물학회 2019 방사성폐기물학회지 Vol.17 No.4

Large amounts of concrete waste are likely to arise from the decommissioning of a Kori-1 nuclear power plant. Several studies have been conducted on decommissioning concrete waste in recent decades, however, they have been limited to contaminated concrete issues or were small pilot-scale experiments. This study constructed two industrial-scale models of on-site concrete waste management for clean as well as contaminated concrete. To evaluate the performance of both the models, simulations were conducted using the Flexsim software. The concrete particle size distribution of Kori-1 and concrete processor properties based on widely used construction equipment were used as sources of input data for the simulations. It was observed that it may take over two years to complete the on-site concrete management processes owing to the performance of existing processors. In addition, it was demonstrated that it is essential to identify bottlenecks in the system and enhance the performance of the relevant processors to avoid delays of the decommissioning schedule. Our results suggest that this novel approach can contribute to developing schedules or expediting delayed activities in the Kori-1 decommissioning project.

Structural Stability of Recycled Concrete Waste

Jihoon Lee,Jisoo Yoon,Changlak Kim 한국방사성폐기물학회 2022 한국방사성폐기물학회 학술논문요약집 Vol.20 No.1

The structural stability of the recycled concrete disposal container was evaluated and compared the applicability of the current design standards for recycled concrete of nuclear power plant. The structural stability requirement for concrete disposal containers is 37.7 MPa or more. As a result of the compressive strength test on recycled concrete, 50% of coarse aggregates of recycled concrete was 42.1 MPa. In addition, it was found that the bending strength and shear strength of recycled reinforced concrete beam exceeded the current design standard. Therefore, it is judged that recycled concrete containing coarse aggregates can be sufficiently utilized. It was possible to ensure the structural stability of the concrete container without changing the design specifications and reinforcing bars when recycled concrete is applied.

부순모래 사용에 따른 원전 구조물용 콘크리트의 기초적 특성

박성학(Sung-Hak Park),김경환(Kyung-Hwan Kim),최병걸(Byung-Keol Choi),최연왕(Yun-Wang Choi) 한국건설순환자원학회 2017 한국건설순환자원학회 논문집 Vol.5 No.2

본 연구에서는 원전 구조물용 콘크리트의 잔골재로 부순모래를 사용하기 위한 연구의 일환으로 기존의 부순모래 생산공정에서 임팩트크러셔(Impact crusher)의 성능(회전수)을 높여 입형을 개선하고 ASTM C 33에 적합하도록 입도를 조정한 부순모래의 입형 및 입도 특성을 검토하였으며, 강모래에 대한 치환률에 따라 콘크리트를 제조하여 콘크리트 배합 특성, 굳지 않은 콘크리트 특성 및 경화한 콘크리트 특성을 검토하였다. 실험결과, 대부분의 콘크리트 특성이 강모래만을 사용한 콘크리트와 동등한 수준으로 나타났지만, 강모래에 대한 치환률 50% 이상일 경우, 치환률 증가에 따라 허용 범위 내에서 공기량, 압축강도 및 인장강도는 다소 감소되는 것으로 나타났다. This study, as a research for using crushed sand as a fine aggregate of concrete for nuclear structures, we improved the performance of impact crusher in the existing crushed sand production process and adjusted grain size to conform to ASTM C 33 The shape and grain size characteristics of a crushed sand were examined and concrete was prepared according to the substitution ratio of the sand to investigate the properties of fresh concrete and hardened concrete. The experimental results show that most of the concrete characteristics are equivalent to those of concrete using only heavy sand. However, when the substitution rate of steel sand exceeds 50%, the amount of air, compressive strength and tensile strength are somewhat reduced.

Certified Reference Materials for Decommissioning Nuclear Power Plants

Minju Lee,Yoonhee Jung,Sang-Han Lee 한국방사성폐기물학회 2023 한국방사성폐기물학회 학술논문요약집 Vol.21 No.2

The Korea Research Institute of Standards and Science has developed certified reference materials (concrete, soil, and metal radioactive liquid) for measuring gamma-emitting radionuclides to improve and maintain the quality assurance and quality control of the radioactivity measurement in decommissioning nuclear power plants. The raw materials that make up each CRM were mixed in an appropriate ratio with radionuclides. For certification and homogeneity assessment, 10 bottles were randomly selected, two sub-samples were collected from each bottle, and radionuclides were measured via HPGe gamma spectrometry. The results of the homogeneity tests using a one-way analysis of variance on the radionuclides in the CRMs fulfilled the requirements of ISO Guide 35. Coincidence summing and self-absorption correction were performed on measurement results by introducing the Monte Carlo efficiency transfer code and Monte Carlo N-Particle transport code. In concrete analysis, the reference values for five radionuclides (60Co, 241Am, 134Cs, and 137Cs) in the CRM were in the range of 15-40 Bq/kg, and the expanded uncertainty was within 10% (k = 2). In soil analysis, the reference values for the 137Cs and 60Co were 118.7 and 124.4 Bq/kg, and the expanded uncertainty was within 10% (k = 2). In metal radioactive liquid analysis, the reference values for 134Cs, 137Cs and 60Co in the CRM were in the range of 200-270 Bq/kg, and the expanded uncertainty was within 7% (k = 2).