원자력발전소 피동 노내 냉각계통 적용을 위한 유압 제어봉 구동시스템 설계

김인국(In Guk Kim),방인철(In Cheol Bang) 대한기계학회 2018 대한기계학회 춘추학술대회 Vol.2018 No.12

To enhance the safety of the nuclear power plants, a passive in-core cooling system (PINCs) is currently being studied for the various reactor types such as PWR, SMR, Gen. IV reactors in UNIST. A PINCs consists of hybrid control rod assemblies, a hydraulic control rod drive mechanism, and a natural circulation loop to remove the decay heat from the nuclear fuels. In PINCs, one of the key elements is the hydraulically driven rod control system that is being studied for their various benefits, including a) ability to be in-vessel control, b) short length of the control rods, and c) safe reactor shutdown. In this paper, a novel hydraulic rod control system was designed and tested. The tests of the hydraulic rod control system with 4-hybrid control rod were conducted with the different weight and geometry. The theoretical models of the steady flow and transient behavior were driven by the force-induced patterned geometry of the cylinder. The experimental results showed that the position of the hydraulic system with control rod was well predicted by the theoretical model within ±8.6%. Finally, this study shows the unique feature of the hydraulically driven system and its behavioral characteristics.

과냉각수조 내의 제트에 의한 용융우드메탈 미립화에 관한 실적 연구

허효 ( Hyo Heo ),정동욱 ( Dong Wook Jerng ),방인철 ( In Cheol Bang ) 한국액체미립화학회 2014 한국액체미립화학회 학술강연회 논문집 Vol.2014 No.-

The liquid jet breakup has been studied in the areas of aerosols, spray and combustion. The jet breakup depends on several parameters, such as the jet velocity, the inner diameter of the nozzle and the density ratio of the water to the jet. This paper deals with characteristics of the jet breakup according to the jet velocity and the nozzle diameter. In order to consider only hydrodynamic factors, all jet breakup experiments were conducted in non-boiling conditions. In the present study, the wood`s metal was used as the jet material. The jet behavior in the water pool was observed by high-speed camera and PIV technique. All the experiments showed that the jet breakup occurred instantly as the jet contacted with the subcooled water and the fragmented debris moved in radial direction. However, there were some differences between experimental conditions. At the small nozzle diameter, there was no significant difference according to changes in the jet velocity. Generally, the breakup rate strongly depends on the jet velocity but the density ratio affects the breakup behavior most significantly at low jet velocity(< 4.5 m/s). For the larger nozzle diameter, extensive breakup occurred as the jet entered the water pool. It was observed that the more molten wood`s metal is ejected, the debris moved strongly in radial direction. After each experiment, the debris of the jet was collected, dried and sieved to analyze characteristics of the jet breakup. Then, the debris was distributed according to the debris size. For the condition of inner diameter of 6.95 mm and the jet velocity of 2.8 m/s, the debris size of 22 mm gave the largest mass fraction, 39%. For higher jet velocity of 3.1 m/s, the debris size of 14 mm gave the largest mass fraction, 36%. For the nozzle with inner diameter of 9.30 mm, the debris size distribution was different. For jet velocity of 2.8 m/s and 3.1 m/s, the debris size with the largest mass fraction was found to be 14 mm. It means that the debris size decreases as either the diameter or the jet velocity increases.

나노유체 : 수조비등 환경에서 나노입자 코팅두께에 따른 임계열유속 결과의 실험적 연구

박성대 ( Seong Dae Park ),문성보 ( Sung Bo Moon ),방인철 ( In Cheol Bang ) 한국액체미립화학회 2012 한국액체미립화학회 학술강연회 논문집 Vol.2012 No.-

Since nanofluids, which are colloidal dispersions of nanoparticles in a base fluid such as water, were known as a way to significantly enhance the CHF, the pool boiling CHF test was conducted in a variety conditions depending on the material, the concentration etc. The concentration is the factor which influences the amount the coating materials on the heater surface. In most papers which are reporting the results of the pool boiling CHF test for nanofluids, the exact heating time is not described according to the heat flux level. The heating time is also an important factor that determines the amount of coated material. Alumina nanofluid is prepared by dispersing nanoparticles into the distilled water as a base fluid. The concentration of nanofluid is 0.01Vol%. Pre-coating process was carried out from 1 to 180 minutes at 600kW/m2. Heating time affects CHF positively in the region of a relatively short pre-coating time. The trend of CHF change is slowly decreased as pre-coating time is incrased. When more nanoparticles are coated on the heater surface but not heat transfer area is limited, the heat resistance which is disturbing the heat flow is increasing. The static contact angle was measured for sessile droplets of pure water (1μl) at 25℃ in air on the clean and nanoparticles coated surfaces boiled in nanofluids. The dramatic decrease of contact angle was observed on the coated heater surface. The results of contact angle are not uncovering the slight decrease of CHF in high pre-coating region. Hydrodynamic instability theory has been known as model of Zuber who proposed initially. The nanoparticle-coated surface has a shorter average distance compared with a bare surface. A case of high pre-heating time has a short wavelength in this work. A short wavelength allows to the vapor to prevent the formation of bulk vapor by venting the vapor equally across the heater surface. But the results of wavelength are not similarly uncovering the slight decrease of CHF in high pre-coating region. Coating thickness was measured by analyzing the SEM images. The thickness is continually increased but the gradient is becoming gentle. Reversely, porosity is decreased as the pre-boiling time is longer. It means that the coating layer formed by nanoparticles is becoming dense. It is clear the coating layer functions as a heat transfer resistance.

하이브리드 제어봉

방인철(In Cheol Bang),정영신(Yeong Shin Jeong),김경모(Kyung Mo Kim),김인국(In Guk Kim) 한국유체기계학회 2014 한국유체기계학회 학술대회 논문집 Vol.2014 No.11

나노유체 : 나노유체를 활용한 APR 1400 부수로 벤치마크 해석

이민호 ( Min Ho Lee ),방인철 ( In Cheol Bang ) 한국액체미립화학회 2015 한국액체미립화학회 학술강연회 논문집 Vol.2015 No.-

In case of pressurized water reactor, thermal conductivity of coolant is crucial factor for improvement of performance and safety of nuclear power plants. In this report, to enhance thermal conductivity of coolant, nanofluid was used. nanofluid is fluid having particles which have scale of nanometer, called nanoparticles. Silicon carbide, aluminum oxide, and graphene oxide have higher thermal conductivity than pure water. Moreover, they have not too big cross-section with neutron, especially thermal. Over 0.1 % of volume fraction of nanoparticle can make conspicuous difference with pure water. In the present study, three nanoparticles, such as SiC, aluminum oxide, and grapheme oxide, were used as nanofluid to show the effect of thermal conductivity. The volume fraction of nanoparticle was 0.2 % 0.5 %, 1.0 %, and 2.0 %. Thermal conductivity and viscosity of nanofluids were measured by KD2PRO and SV-10 respectively. The measurement data of thermal conductivity and viscosity was applied in the MATRA and CFD APR 1400 analysis. As anticipated, relative to pure water, thermal conductivity of nanofluid was increased and viscosity of nanofluid was also increased. But it was not effective as expectation. Due to lowered specific heat of nanofluid, overall coolant bulk temperature was increased and DNBR was decreased and these tendency was deepened with volume fraction of nanoparticle. CFD and MATRA show similar result

긴 히트파이프와 써모사이폰의 열수력적 특성 연구

서요섭(Yosup Seo),방인철(In Cheol Bang),이재영(JaeYoung Lee) 대한기계학회 2014 대한기계학회 춘추학술대회 Vol.2014 No.11

The present study is to compare thermal hydraulic characteristics between a heat pipe and a thermosyphon with relatively large length. Recently the heat transfer devices have been seriously considered for the passive heat removal of reactor core or spent fuels in the nuclear industry. In this research, a series experimental works have been made to measure the thermal performances of heat pipe and thermosyphon with large length conditions. A heat pipe and a thermosyphon with 3m of length and 16.57mm of inner diameter were specially manufactured for experiment. Surface temperature and pressure were measured to compare their performances. The experimental results show that the thermal resistance of heat pipe is 92.61% higher than that of thermosyphon in maximum. It was also found that the gap of thermal resistance increases as the heat input increases. The reason seems to be that the wick structure may work as obstacle for vapor and fluid flow in the large length condition. Therefore, it can be concluded that a thermosyphon shows better performance than heat pipe in the large length condition.

다양한 형태의 곳체다슬기 (Semisulcospira gottschei) 치패용 배합사료에 대두박과 소맥분 이용성

황규덕 ( Hwang Gyu Deog ),김이오 ( Kim I O ),박종호 ( Park Jong Ho ),방인철 ( Bang In Cheol ),김경덕 ( Kim Gyeong Deog ),장현석 ( Jang Hyeon Seog ),이상민 ( Lee Sang Min ) 한국수산과학회 2003 한국수산과학회지 Vol.36 No.5

N/A A feeding trial was carried out to investigate the utilization of dietary soybean meal and wheat flour as substitutes for fish meal and alginate in different dietary types (powder, pellet and flake) for juvenile snail (Sernisulcospira gottschei). After 10 weeks feeding trial, survival was not affected by formulation and type of diets (P>0.05), but weight gain was significantly affected by dietary formulation (P<0.001 ) and type (P<0.05). In the same dietary formulation, weight gain of the snail fed the flake type of diets was lower than that of the snail fed the powder or pellet types. However, the type of diet did not affect weight gain when snail fed diets containing 37% soybean meal and 18% alginate. The weight gain was lower in the snail fed diets containing 25% fish meal compared with that of the snail fed diets containing 33-37% soybean meal at the same dietary type. When soybean meal was used as main protein source in diets, weight gain was not affected by dietary alginate (0 and 18%) and wheat flour (36 and 58%) contents. Crude protein and ash contents of whole body of the snail was not affected either by formulation or by type of diet. Moisture and crude lipid contents of the whole body were significantly affected by dietary formulation, but not by the type. These results indicate that 25% fish meal could be replaced by 37% soybean meal as dietary protein source, and pellet and powder could be desirable dietary type for the optimum growth of the snail.

과냉각수조 내의 제트에 의한 용융우드메탈 미립화에 관한 실험적 연구

허효 ( Hyo Heo ),정동욱 ( Dong Wook Jerng ),방인철 ( In Cheol Bang ) 한국분무공학회 2014 한국액체미립화학회지 Vol.19 No.4

The liquid jet breakup has been studied in the areas such as aerosols, spray and combustion. The breakup depends on several physical parameters such as the jet velocity, the nozzle inner diameter, and the density ratio of the water to the jet. This paper deals with characteristics of the jet breakup according to the jet velocity and the nozzle diameter. In order to consider only hydrodynamic factors, all the experiments were conducted in non-boiling conditions. The jet behavior in the water pool was observed by high-speed camera and PIV technique. For the condition of the inner diameter of 6.95 mm and the jet velocity of 2.8 m/s, the debris size of 22 mm gave the largest mass fraction, 39%. For higher jet velocity of 3.1 m/s, the debris size of 14 mm gave the largest mass fraction, 36%. For the nozzle with inner diameter of 9.30 mm, the debris size distribution was different. For jet velocity of 2.8 m/s and 3.1 m/s, the debris size with the largest mass fraction was found to be 14 mm. It was identified that the debris size decreased as the diameter or the jet velocity increased.

미립화 및 분무장치 2 : 수력학적 캐비테이션을 모의 크러드 침전층 제거 실험

김성만 ( Seong Man Kim ),이승원 ( Seung Won Lee ),박성대 ( Seong Dae Park ),방인철 ( In Cheol Bang ) 한국액체미립화학회 2012 한국액체미립화학회 학술강연회 논문집 Vol.2012 No.-

Axial Offset Anomaly (AOA) referring to an unexpected neutron flux depression is also known as Crud Induced Power Shift (CIPS). Fuel assemblies removed from an AOA core has shown a thick porous deposition layer of crud on fuel clad surface. Hydrodynamic cavitation generates shock pressure of a few tens MPa due to bubble collapse like the cavitation generated by Ultrasonics. It is well known that the cavitation can erode the metal surface. The idea of the current study is that such energetic cavitation bubble collapses could help to remove the crud from the fuel assembly. Therefore, the current study first investigates effects of hydrodynamic cavitation occurred from a single hole orifice fundamentally. The orifice can be easily occurred the cavitation. In addition to common cavitation, effect of swirl was measured and quantified using sensitive film. The purpose of this study is to optimize the effect of cavitation erosion. For investigate the cavitation effect, effect of cavitation was measured by film. The film was discolored by the pressure with a measurement range of its own. It is individual to reflect the value stored pressure as the disposable film. For investigate of removal effect, CRUD was coated by nanoparticle. CRUD consists primarily of magnetite, nickel ferrite, cobalt ferrite, and so on. For only checking the cavitation effects in this work, however, specimens made of SS316L, alloy of Cr, Ni and Fe are simply deposited by silicon carbide nanoparticles since the nanoparticles with the CRUD porous layer. It shows a CRUD-like deposition structure. Weight change of sample was measured the through each coated sample for analyzing the removal effect on each cavitation number. The result of pressure in two flows, higher pressure level is observed in case of using swirl flow. The samples were exposed to cavitation during the same time, and it was compared the result between using only orifice and using both orifice and line static mixer. Maximum shock pressure was recorded at swirl flow caused by line static mixer.

나노유체 : 임계열유속 및 사고 저항성 증진을 위한 크로미아 나노유체 활용

손규민 ( Gyu Min Son ),서한 ( Han Seo ),문성보 ( Sung Bo Moon ),서석빈 ( Seok Bin Seo ),방인철 ( In Cheol Bang ) 한국액체미립화학회 2015 한국액체미립화학회 학술강연회 논문집 Vol.2015 No.-

Hydrogen explosion can threaten the safety of nuclear power plants as shown in Fukushima accident. When zircaloy (fuel cladding) is oxidized, it generates hydrogen and oxidation speeds up at high temperature. The concept of accident-tolerant-fuel (ATF) aims for enhanced safety response, mitigating oxidation of fuel claddings during accident and chrome coating on zircaloy surface shows promising results in this regard. By forming Cr2O3 (chromia or chrome oxide) layer on the outermost surface when oxidized, it prevents further oxidation inwards. However chrome coatings show some limitations since it forms hydrophobic surface and damages critical heat flux (CHF). Instead, direct coating of chromia layer is proposed in this study. Chromia coating on nichrome wire was done by boiling deposition of chromia nanofluid. Chrome coating with PVD was also prepared for comparison. Pool boiling experiment results show that chromia coated wire’s CHF is approximately twice of bare and chrome coated wires. For explanation of CHF enhancement, contact angle was compared showing chromia coating has hydrophilic surface. To ensure that direct coating of chromia has oxidation resistance, samples are oxidized in furnace and weight gain was compared.