• 대한기계학회논문집A
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• 제35권11호
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• pp.1499-1506
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• 2011

초고온가스로로부터 생성된 $950^{\circ}C$ 정도의 초고온 열을 이용하여 수소를 경제적이며 또한 대량으로 생산하려는 원자력수소생산시스템에서 중간열교환기는 원자로에서 생산된 초고온 열을 수소생산 공장으로 전달하는 핵심 기기중의 하나이다. 한국원자력연구원에서는 초고온가스로에 사용될 핵심 기기에 대한 성능시험을 위해 소형가스루프를 구축하였고 중간열교환기의 유력한 형태로 고려되고 있는 인쇄기판형 열교환기의 소형 시제품을 제작하였다. 본 연구는 인쇄기판형 열교환기 소형 시제품을 소형가스루프에서 시험하기 전에 루프 시험조건하에서 인쇄기판형 열교환기 소형 시제품의 고온 구조건전성을 미리 평가하기 위한 작업의 일환으로 수행한 결과, 즉 고온 구조해석 모델링, 거시적 열 해석 및 구조 해석 결과 등을 정리한 것이다. 해석 결과는 인쇄기판형 열교환기 소형 시제품 성능시험결과외 비교하고 향후 제작될 중형 시제품 설계/제작에 반영할 것이다.

• Nuclear Engineering and Technology
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• 제50권3호
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• pp.356-367
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• 2018

A series of tests dedicated to station blackout (SBO) accident scenarios have been recently performed at the $Prim{\ddot{a}}rkreislauf-Versuchsanlage$ (primary coolant loop test facility; PKL) facility in the framework of the OECD/NEA PKL-3 project. These investigations address current safety issues related to beyond design basis accident transients with significant core heat up. This work presents a detailed analysis using the best estimate thermal-hydraulic code TRACE (v5.0 Patch4) of different SBO scenarios conducted at the PKL facility; failures of high- and low-pressure safety injection systems together with steam generator (SG) feedwater supply are considered, thus calling for adequate accident management actions and timely implementation of alternative emergency cooling procedures to prevent core meltdown. The presented analysis evaluates the capability of the applied TRACE model of the PKL facility to correctly capture the sequences of events in the different SBO scenarios, namely the SBO tests H2.1, H2.2 run 1 and H2.2 run 2, including symmetric or asymmetric secondary side depressurization, primary side depressurization, accumulator (ACC) injection in the cold legs and secondary side feeding with mobile pump and/or primary side emergency core coolant injection from the fuel pool cooling pump. This study is focused specifically on the prediction of the core exit temperature, which drives the execution of the most relevant accident management actions. This work presents, in particular, the key improvements made to the TRACE model that helped to improve the code predictions, including the modeling of dynamical heat losses, the nodalization of SGs' heat exchanger tubes and the ACCs. Another relevant aspect of this work is to evaluate how well the model simulations of the three different scenarios qualitatively and quantitatively capture the trends and results exhibited by the actual experiments. For instance, how the number of SGs considered for secondary side depressurization affects the heat transfer from primary side; how the discharge capacity of the pressurizer relief valve affects the dynamics of the transient; how ACC initial pressure and nitrogen release affect the grace time between ACC injection and subsequent core heat up; and how well the alternative feeding modes of the secondary and/or primary side with mobile injection pumps affect core quenching and ensure stable long-term core cooling under controlled boiling conditions.

• Corrosion Science and Technology
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• 제12권2호
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• pp.102-112
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• 2013

A very high-temperature gas reactor (VHTR) is one of the next generation nuclear reactors owing to its safety, high energy efficiency, and proliferation-resistance. Heat is transferred from the primary helium loop to the secondary helium loop through an intermediate heat exchanger (IHX). Under VHTR environment Alloy 617 is being considered a candidate Ni-based superalloy for the IHX of a VHTR, owing to its good creep resistance, phase stability and corrosion resistance at high temperature. In this study, high-temperature corrosion tests were carried out at 850 - $950^{\circ}C$ in air and impure helium environments. Alloy 617 specimens showed a parabolic oxidation behavior for all temperatures and environments. The activation energy for oxidation was 154 kJ/mol in helium environment, and 261 kJ/mol in an air environment. The scanning electron microscope (SEM) and energy-dispersive x-ray spectroscopy (EDS) results revealed that there were a Cr-rich surface oxide layer, Al-rich internal oxides and depletion of grain boundary carbide after corrosion test. The thickness and depths of degraded layers also showed a parabolic relationship with the time. A corrosion rate of $950^{\circ}C$ in impure helium was higher than that in an air environment, caused by difference in the outer oxide morphology.

• Nuclear Engineering and Technology
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• 제49권7호
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• pp.1537-1546
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• 2017

Many thermal-hydraulic tests have been conducted at the Korea Atomic Energy Research Institute for verification of the SMART (System-integrated Modular Advanced ReacTor) design, the standard design approval of which was issued by the Korean regulatory body. In this paper, the contributions of these tests to the standard design approval of SMART are discussed. First, an integral effect test facility named VISTA-ITL (Experimental Verification by Integral Simulation of Transients and Accidents-Integral Test Loop) has been utilized to assess the TASS/SMR-S (Transient and Set-point Simulation/Small and Medium) safety analysis code and confirm its conservatism, to support standard design approval, and to construct a database for the SMART design optimization. In addition, many separate effect tests have been performed. The reactor internal flow test has been conducted using the SCOP (SMART COre flow distribution and Pressure drop test) facility to evaluate the reactor internal flow and pressure distributions. An ECC (Emergency Core Coolant) performance test has been carried out using the SWAT (SMART ECC Water Asymmetric Two-phase choking test) facility to evaluate the safety injection performance and to validate the thermal-hydraulic model used in the safety analysis code. The Freon CHF (Critical Heat Flux) test has been performed using the FTHEL (Freon Thermal Hydraulic Experimental Loop) facility to construct a database from the $5{\times}5$ rod bundle Freon CHF tests and to evaluate the DNBR (Departure from Nucleate Boiling Ratio) model in the safety analysis and core design codes. These test results were used for standard design approval of SMART to verify its design bases, design tools, and analysis methodology.

• KSBB Journal
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• 제7권1호
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• pp.59-65
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• 1992

외부 순환식 공기리프트 반응기에서 기상유속과 액상의 점도를 변수로 하여 기체체류량과 액체의 순환시간, 혼합시간, 순환속도 및 축방향분산계수를 측정하여 다음과 같은 결론을 얻었다. 1. 기체체류량은 기체유속이 증가함에 따라 증가 하였으며, 점도가 증가함에 따라서는 약간 감소하는 경향을 보였다. 또 기체유속이 증가함에 따라 상승관에서는 기체체류량의 증가율이 감소한 반면 하강관에서는 증가하였다. 2. 기체유속이 증가함에 따라 순환시간 및 혼합시간은 초기에 급격히 짧아지다가 거의 일정한 값을 나타내었으며, 액체의 점도가 증가함에 따라 순환기산과 혼합시간은 모두 증가하였다. 3. 순환 액체의 속도는 기체의 속도에 따라 초기에 급격히 증가하나 기체속도가 약 5cm/sec이상이 되면 그 증가율이 매우 둔화되었으며, 점도가 증가함에 따라 약간 감소함을 알 수 있었다. 또한 압력수지식으로 예측한 이론값과 실험값은 낮은 기체유속 영역에서는 잘 일치하였으나 기체유속이 증가함에 따라 실험값이 이론값보다 작은 값을 나타내었다. 4. 기체유속이 증가함에 따라 Bodenstein number는 감소하였고, 축방향분산계수는 증가하였으며, 점도가 증가함에 따라 약간 감소하는 경향을 보였다. 본 실험범위에서 분산이 많이 일어나mixed folw에 근접함을 알 수 있었다.

• 대한기계학회논문집A
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• 제35권9호
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• pp.1137-1143
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• 2011

초고온가스로의 중간열교환기는 원자로에서 생산된 $950^{circ}C$ 정도의 초고온 열을 수소생산 공장으로 전달하는 핵심 기기이다. 한국원자력연구원에서는 중간열교환기의 후보 형태로 고려되고 있는 인쇄기판형 열교환기의 소형 시제품을 제작하였다. 본 연구는 소형가스루프 시험조건하에서 인쇄기판형 열교환기 소형 시제품의 고온 구조건전성을 시험수행 전에 미리 평가하기 위한 작업의 일환으로 인쇄기판형 열교환기 소형 시제품에 대한 고온 구조해석 모델링, 거시적 열 해석 및 구조 해석을 수행하고 그 결과들을 정리한 것이다. 해석 결과는 곧 수행될 인쇄기판형 열교환기 소형 시제품 성능시험결과와 비교하고 또한 향후 제작될 중형 시제품 설계/제작에 반영할 것이다.

• Nuclear Engineering and Technology
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• 제53권5호
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• pp.1436-1445
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• 2021

To obtain the dynamic characteristics of reactor secondary circuit under transient conditions, the system analysis program was developed in this study, where dynamic models of secondary circuit were established. The heat transfer process and the mechanical energy transfer process are modularized. Models of main equipment were built, including main turbine, condenser, steam pipe and feedwater system. The established models were verified by design value. The simulation of the secondary circuit system was conducted based on the verified models. The system response and characteristics were investigated based on the parameter transients under emergency shutdown and overload. Various operating conditions like turbine emergency shutdown and overspeed, condenser high water level, ejector failures were studied. The secondary circuit system ensures sufficient design margin to withstand the pressure and flow fluctuations. The adjustment of exhaust valve group could maintain the system pressure within a safe range, at the expense of steam quality. The condenser could rapidly take out most heat to avoid overpressure.

• 대한기계학회논문집A
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• 제38권8호
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• pp.831-836
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• 2014

본 연구에서는 한국원자력연구원 내에 설치될 예정인 소듐시험 시설인 SELFA(Sodium Thermal-hydraulic Experiment Loop for Finned-tube Sodium-to-Air heat exchanger) 내에서 정상상태 가동온도가 $510^{\circ}C$의 고온 압력용기인 팽창탱크에 대해 고온 건전성 평가를 수행하였다. 팽창탱크에 대해 3 차원 유한요소해석에 기초하여 고온설계 기술기준인 ASME Section III Subsection NH 와 프랑스의 RCC-MRx 코드를 따라 크리프-피로 손상평가를 수행하였다. 평가결과 팽창탱크는 크리프-피로 설계 과도 하중 하에서 구조적 건전성을 유지하는 것으로 나타났다. 316L 스테인리스강 재질의 동 압력용기에 대해 정량적 코드 비교 분석을 수행하였다.

• Journal of Electrical Engineering and Technology
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• 제5권1호
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• pp.116-128
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• 2010

Modeling of the three phase electric arc furnace and its voltage flicker mitigation are the purposes of this paper. For modeling of the electric arc furnace, at first, the arc is modeled by using current-voltage characteristic of a real arc. Then, the arc random characteristic has been taken into account by modulating the ac voltage via a band limited white noise. The electric arc furnace compensation with static VAr compensator, Thyristor Controlled Reactor combined with a Fixed Capacitor bank (TCR/FC), is discussed for closed loop control of the compensator. Instantaneous flicker sensation curves, before and after accomplishing compensation, are measured based on IEC standard. A new method for controlling TCR/FC compensator is proposed. This method is based on applying a predictive approach with closed loop control of the TCR/FC. In this method, by using the previous samples of the load reactive power, the future values of the load reactive power are predicted in order to consider the time delay in the compensator control. Also, in closed loop control, two different approaches are considered. The former is based on voltage regulation at the point of common coupling (PCC) and the later is based on enhancement of power factor at PCC. Finally, in order to show the effectiveness of the proposed methodology, the simulation results are provided.

• 공업화학
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• 제23권6호
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• pp.608-613
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• 2012

유전체 배리어 방전 플라즈마를 모사 농산물 저장시설($1.0m^3$)의 에틸렌 제거에 적용하였다. 에틸렌이 포함된 공기를 플라즈마 반응기에 유입시켜 처리한 후 다시 농산물 저장시설로 재순환하는 방식으로 시험을 수행하였다. 주요 운전변수는 방전전력, 순환기체 유량, 초기 에틸렌 농도 및 처리시간이었다. 에틸렌의 분해속도는 주로 방전전력과 처리시간에 의해 결정되었다. 다른 조건을 일정하게 유지한 상태에서 플라즈마 반응기 후단에 이산화망간 오존분해 촉매를 설치했을 경우 오존분해 촉매가 없을 때 보다 에틸렌 제거속도가 더 빨랐는데, 이 결과는 플라즈마 반응기에서 배출되는 오존이 농산물 저장시설에 유입 축적되어 에틸렌을 추가적으로 분해했기 때문이다. 에틸렌 초기 농도 50 ppm을 기준으로 하면 이를 완전히 분해하기 위한 에너지 요구량은 약 60 kJ이었다.