• 에너지공학
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• 제23권3호
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• pp.21-26
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• 2014

유럽 원전 시장 개척을 위해 개발 중인 EU-APR1400은 중대사고 대처설비로 노외 노심용융물 보유 및 냉각을 위한 소위 Core catcher라 불리는 노외 노심용융물 냉각설비를 개발 중이며, Core catcher body를 노심용융물로부터 보호하기 위하여 노심용융물의 물성 및 상태를 변화시켜 냉각 및 보유에 유리하게 하는 희생물질을 설치한다. 중대사고 시 원자로 압력용기의 틈으로부터 노심용융물이 분출되어 희생물질에 충돌 시 열 전달량이 매우 증가하게 되므로, 이 때 노심용융물 제트의 충돌에 의한 희생물질의 침식율을 정확하게 예측하는 것은 매우 중요하다. 이 논문에서는 경계층 이론을 기반으로 한 희생물질 침식 모형을 제안하고 KAERI에서 수행한 실험결과와 비교하였다.

• 비파괴검사학회지
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• 제20권4호
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• pp.314-321
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• 2000

모의 원자로내 용융물 냉각 실증 실험 결과 용융물 $Al_2O_3/Fe$ thermite 와 lower head vessel사이에 간극이 발생된다. 간극을 정량적으로 측정하기 위한 기존의 초음파 방법은 구조물의 복잡성과 $2300^{\circ}C$ 에서 용융되는 thermite $Al_2O_3/Fe,\;Al_2O_3$의 영향으로 발생되는 lower head의 열영향부위(HAZ)의 금속학적인 결정입자 크기의 변화로 결정 계면으로부터 발생되는 잡음신호와 초음파 산란, 감쇠, 모드 변환 등이 발생되어 신뢰성이 떨어지고 있다. 간극을 정량적으로 측정하기 위해서 thermite와 lower head 사이에 물이 채워진 형태의 즉 고체, 액체, 고체의 다층구조에서 초음파의 진행 및 반사 형태를 분류 및 분석하였다. 결정립의 잡음을 억제하기 위하여 주파수대역의 확률 처리 방식인 PT(polarity threshold) 알고리즘을 이용하여 약 6dB 신호 대 잡음비의 개선효과를 가져왔다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집A
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• pp.782-787
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• 2001

This paper is concerned with the global rupture of a nuclear reactor pressure vessel(RPV) in a severe accident. During the severe reactor accident of molten core, the temperature and the pressure in the nuclear reactor rise to a certain level depending on the initial and subsequent condition of a severe accident. While the rise of the temperature cause the thermal softening of RPV material, the rise of the internal pressure could cause failure of the RPV lower head. The global rupture of an RPV is simulated by finite element limit analysis for the collapse pressure and mode and this analysis results have been compared with a variation of the internal pressure of RPV. The finite element limit method is a systematic tool to secure the safety criteria of a nuclear reactor and to evaluate the in-vessel corium retention.

• Nuclear Engineering and Technology
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• 제41권9호
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• pp.1157-1170
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• 2009

A variety of Generation III/III+ reactor designs featuring enhanced safety and improved economics are being proposed by nuclear power industries around the world to solve the future energy supply shortfall. Nanofluid coolants showing an improved thermal performance are being considered as a new key technology to secure nuclear safety and economics. However, it should be noted that there is a lack of comprehensible design works to apply nanofluids to Generation III+ reactor designs. In this work, the review of accident scenarios that consider expected nanofluid mechanisms is carried out to seek detailed application spots. The Axiomatic Design (AD) theory is then applied to systemize the design of nanofluid-engineered nuclear safety systems such as Emergency Core Cooling System (ECCS) and External Reactor Vessel Cooling System (ERVCS). The various couplings between Gen-III/III+ nuclear safety features and nanofluids are investigated and they try to be reduced from the perspective of the AD in terms of prevention/mitigation of severe accidents. This study contributes to the establishment of a standard communication protocol in the design of nanofluid-engineered nuclear safety systems.

• Nuclear Engineering and Technology
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• 제54권5호
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• pp.1845-1850
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• 2022

In-vessel corium retention (IVR) during external reactor vessel cooling (ERVC) is a key severe accident management strategy adopted in advanced nuclear power plants. The injection of nanofluids has been regarded as a means of enhancing CHF when using the IVR-ERVC strategy to safeguard high-power nuclear reactors. However, a critical practical concern is that various types of debris flowing from the contaminant sump during operation of an ERVC system might degrade CHF enhancement by nanofluids. Our objective here was to experimentally assess the viability of nanofluid use to enhance CHF in practical ERVC contexts (e.g., when fluids contain various types of debris). The types and characteristics of debris expected during IVR-ERVC were examined. We performed pool boiling CHF experiments using nanofluids containing these types of debris. Notably, we found that debris did not cause any degradation of the CHF enhancement characteristics of nanofluids. The nanoparticles are approximately 1000-fold smaller than the debris particles; the number of nanoparticles in the same volume fraction is 1 billion-fold greater. Nanofluids increase CHF via porous deposition of nanosized particles on the boiling surface; this is not hindered by extremely large debris particles.

• Nuclear Engineering and Technology
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• 제41권8호
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• pp.1005-1014
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• 2009

The Dual Unit Optimizer 2000 MWe (DUO2000) is put forward as a new design concept for large power nuclear plants to cope with economic and safety challenges facing the $21^{st}$ century green and sustainable energy industry. DUO2000 is home to two nuclear steam supply systems (NSSSs) of the Optimized Power Reactor 1000 MWe (OPR1000)-like pressurized water reactor (PWR) in single containment so as to double the capacity of the plant. The idea behind DUO may as well be extended to combining any number of NSSSs of PWRs or pressurized heavy water reactors (PHWRs), or even boiling water reactors (BWRs). Once proven in water reactors, the technology may even be expanded to gas cooled, liquid metal cooled, and molten salt cooled reactors. With its in-vessel retention external reactor vessel cooling (IVR-ERVC) as severe accident management strategy, DUO can not only put the single most querulous PWR safety issue to an end, but also pave the way to very promising large power capacity while dispensing with the huge redesigning cost for Generation III+ nuclear systems. Five prototypes are presented for the DUO2000, and their respective advantages and drawbacks are considered. The strengths include, but are not necessarily limited to, reducing the cost of construction by decreasing the number of containment buildings from two to one, minimizing the cost of NSSS and control systems by sharing between the dual units, and lessening the maintenance cost by uniting the NSSS, just to name the few. The latent threats are discussed as well.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 1997년도 춘계학술발표회논문집(1)
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• pp.592-599
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• 1997

중대사고관리 전략의 하나로서 피동형-설계에 적용되고 있는 용기내부보존(IVR)기념 - 이 논문에서는 실제적으로 원자로 압력용기벽 외부냉각(ERVC)방법을 사용한다 -이 규제측면에서는 용융물의 냉각가능성 쟁점의 해결이라는 문맥에서 조감되었다; 기술측면에서는 IVR개념의 신빙성 및 유융성이 언급되었다. 덧붙여서, 이 ERVC방법들이 개량형-설계에 적용되기 위하여 요구되는 점들이 규제측면과 기술측면에서 각각 검토되었다. 이 검토결과의 바탕위에서 용융물 냉각가능성/급냉가능성의 쟁점과 관련하여 전력연구원(KEPRI) 신형원전개발센타(CARD)에서 개발중인 한국차세대원전(KNGR)-설계에서 선택될 수 있는 대안적 전략들이 제안되었다: (1) 전략1A: 젖은공동방법의 신빙성에 기반을 두는 것; (2) 전략1B: 젖은공동방법/격납건물건전성에 기반을 두는 것; (3) 전략2A : ERVC방법의 신빙성에 기만을 두는 것, (4)전략2B: ERVC방법/격납 건물건전성의 균형된 접근법에 기반을 두는 것. 마지막으로, 신형-설계적용의 관점에서 각각 규제측면과 기술측면에서 본 현황파악 및 대책마련의 권고사항이 제시되었다.

• Nuclear Engineering and Technology
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• 제56권1호
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• pp.9-18
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• 2024

In-vessel retention through external reactor vessel cooling (IVR-ERVC) is a severe accident management (SAM) strategy that has been adopted and used in many nuclear reactors such as AP1000, APR1400, and light water reactor etc. Some reactor accidents have raised concerns about nuclear reactors among residents, leading to a decrease in residents' acceptability and many studies on SAM are being conducted. Experiments on IVR-ERVC are almost impossible due to its specificity, so fluid characteristics are analyzed through BALI experiments with similar condition. In this study, computational fluid dynamics (CFD) via Reynolds-averaged Navier-Stokes (RANS) and large eddy simulation (LES) for BALI experiments were performed. Steady-state CFD analysis was performed on three turbulence models, and SST k-ω model was in good agreement with the experimental measurement temperature within the maximum error range of 1.9%. LES CFD analysis was performed based on the RANS analysis results and it was confirmed that the temperature and wall heat flux for depth was consistent within an error range of 1.0% with BALI experiment. The LES CFD analysis results were compared with those of the Lagrangian-based solver. LES matched the temperature distribution better than SOPHIA, but SOPHIA calculated the position of boundary between stratified layer and convective layer more accurately. On the other hand, Lagrangian-based solver predicted several small eddy behaviors of the convective layer and LES predicted large vortex behavior. The vibration characteristics near the cooling part of the BALI experimental device were confirmed through Fast Fourier Transform (FFT) investigation. It was found that the power spectral density for pressure at least 10 times higher near the side cooling than near the top cooling.

• 한국축산시설환경학회지
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• 제9권1호
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• pp.45-56
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• 2003

$TAO^{TM}$ System is an auto-heated thermophilic aerated digestion process using a proprietary microbe called as a Phototropic Bacteria (PTB). High metabolic activity results in heat generation, which enables to produce a pathogen-free and digested liquid fertilizer at short retention times. TAO$^{TM}$ system has been developed to reduce a manure volume and convert into the liquid fertilizer using swine manure since 1992. About 100 units have been installed and operated in Korean swine farms so far. TAO$^{TM}$ system consists of a reactor vessel and ejector-type aeration pumps and foam removers. The swine slurry manure enters into vessel with PTB and is mixed and aerated. The process is operated at detention times from 2 to 4 days and temperature of 55 to $65^{\circ}C$. Foams are occurred and broken down by foam removers to evaporate water contents. Generally, at least 30% of water content is evaporated, 99% of volatile fatty acids caused an odor are removed and pathogen destruction is excellent with fecal coliform, rotavirus and salmonella below detection limits. The effluent from TAO$^{TM}$ system, called as the "TAO EFFLUX", is screened and has superb properties as a fertilizer. Normally N-P-K contents of screened TAO Efflux are 4.7 g/L, 0.375 g/L and 2.8 g/L respectively. The fertilizer effect of TAO EFFLUX compared to chemical fertilizer has been demonstrated and studied with various crops such as rice, potato, cabbage, pumpkin, green pepper, parsley, cucumber and apple. Generally it has better fertilizer effects and excellent soil fertility improvement effects. Moreover, the TAO EFFLUX is concentrated through membrane technology without fouling problems for a cost saving of long distance transportation and a commercialization (crop nutrient commodity) to a gardening market, for example.

• Nuclear Engineering and Technology
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• 제48권4호
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• pp.915-924
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• 2016

After a severe accident to the nuclear reactor, the in-vessel retention strategy is a key way to prevent the leakage of radioactive material. Nanofluid is a steady suspension used to improve heat-transfer characteristics of working fluids, formed by adding solid particles with diameters below 100nm to the base fluids, and its thermal physical properties and heat-transfer characteristics are much different from the conventional working fluids. Thus, nanofluids with appropriate nanoparticle type and volume concentration can enhance the heat-transfer process. In this study, the moving particle semi-implicit method-meshless advection using flow-directional local grid method is used to simulate the bubble growth, departure, and sliding on the downward-facing heating surface in pure water and nanofluid (1.0 vol.% $Al_2O_3/H_2O$) flow boiling processes; additionally, the bubble critical departure angle and sliding characteristics and their influence are also investigated. The results indicate that the bubble in nanofluid departs from the heating surface more easily and the critical departure inclined angle of nanofluid is greater than that of pure water. In addition, the influence of nanofluid on bubble sliding is not significant compared with pure water.