• 한국세라믹학회지
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• 제55권4호
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• pp.400-405
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• 2018

FCM nuclear fuel, a concept proposed as an accident tolerant fuel in light water reactors, consists of TRISO fuel particles embedded in a SiC matrix. The uniform dispersion of internal TRISO fuel particles in the FCM fuel is very important for improving the fuel efficiency. In this study, FCM sintered pellets with various volume ratios of TRISO-coated particles were prepared by hot press sintering. The distribution of TRISO-coated particles was quantitatively analyzed using X-ray ${\mu}CT$ and expressed as a dispersion uniformity index. TRISO-coated particles were most uniformly dispersed in the FCM pellets prepared using only overcoated TRISO particles without mixing of additional SiC matrix powder. FCM pellets with uniformly dispersed TRISO particle volume fraction of up to 50% were prepared using overcoated TRISO particles with varying thickness.

• 한국세라믹학회지
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• 제51권5호
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• pp.418-423
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• 2014

Fully ceramic micro encapsulated (FCM) nuclear fuel is a concept recently proposed for enhancing the stability of nuclear fuel. FCM nuclear fuel consists of tristructural-isotropic (TRISO) fuel particles within a SiC matrix. Each TRISO fuel particle is composed of a $UO_2$ kernel and a PyC/SiC/PyC tri-layer which protects the kernel. The SiC ceramic matrix is created by sintering. In this FCM fuel concept, fission products are protected twice, by the TRISO coating layer and by the SiC ceramic. The SiC ceramic has proven attractive for fuel applications owing to its low neutron-absorption cross-section, excellent irradiation resistivity, and high thermal conductivity. In this study, a SiC-matrix composite containing TRISO particles was sintered by hot pressing with $Al_2O_3-Y_2O_3$ additive system. Various sintering conditions were investigated to obtain a relative density greater than 95%. The internal distribution of TRISO particles within the SiC-matrix composite was observed using an x-ray radiograph. The fracture of the TRISO particles was investigated by means of analysis of the cross-section of the SiC-matrix composite.

• 방사성폐기물학회지
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• 제3권3호
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• pp.201-211
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• 2005

본 연구에서는 사용후 TRISO 연료 처리를 위한 보다 효과적인 공정개발을 위하여 기존 전처리 기술에 대한 검토를 수행하였다. TRISO 연료 처리에 있어서 가장 중요한 사항은 연료입자에 포함되어 있는 탄소와 SiC성분을 효과적으로 분리하는데 있다. 공정개발 초기에 고려되었던 분쇄 후 배소공정의 경우 $^{14}C$ 처리공정에서 발생되는 2차 폐기물로 인하여 분쇄 후 침출공정으로 대체 되었으나 여전히 해결해야 될 근본적인 문제점이 존재하고 있다. 따라서 본 논문에서는 TRISO 입자의 피복층 제거를 위한 새로운 개념의 열적 파쇄와 용융염 전해반응에 의한 피복층 제거 공정을 제안하였으며 각 공정에 대한 원리를 자세하게 기술하였다.

• 비파괴검사학회지
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• 제26권2호
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• pp.69-76
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• 2006

차세대 원자로로 부각되고 있는 고온가스로에서는 윈자로에서는 고온 안정성 및 핵분열생성물 차단 성능이 우수한 TRISO(tri-isotropic) 핵연료를 사용하고 있다. TRISO 핵연료 입자는 직경이 약 1mm인 구 형태로 입자의 중심에는 직경 0.5mm의 핵연료 커널(kernel)이 포함되며 커널 외곽을 코팅 층이 에워싸고 있다. 이 코팅 층은 완충(buffer) PyC(pyrolytic carbon)층, 내부 PyC층, SiC층, 그리고 외부 PyC층으로 구성되어 있다. 각 코팅 층의 두께는 수십-백${\mu}m$ 범위이고 사양으로 정해져 있으며, 본 연구에서는 각 코팅 층의 두께를 비파괴적으로 측정하기 위하여 마이크로포커스 X-선 발생장치와 고해상도 X-선 평판(flat panel) 검출기초 구성된 정밀한 X-선 래디오그래피 장치를 개발하였다. 개발된 마이크로 X-선 래디오그래피 장치를 이용하여 $UO_2$ 핵물질 $ZrO_2$를 커널로 사용한 모의 TRISO 핵연료 입사에 대한 투과 영상을 획득한 후 디지털 영상처리 기술을 이용하여 코팅 층 사이의 경계선이 구분 가능하도록 영상을 개선하고 디지털 영상처리 알고리듬을 개발하여 코팅 층의 두께를 파동으로 측정하였다.

• Nuclear Engineering and Technology
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• 제55권3호
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• pp.1140-1151
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• 2023

Fully Ceramic Microencapsulated (FCM) fuel is emerging advanced fuel material for the future nuclear reactors. The fuel pellet in the FCM fuel is composed of matrix and a large number of TRistructural-ISOtopic (TRISO) fuel particles which are randomly dispersed in the SiC matrix. The minimum layer thickness in a TRISO fuel particle is on the order of 10^-5 m, and the length of the FCM pellet is on the order of 10^-2 m. Hence, the heat transfer in the FCM pellet is a multi-scale phenomenon. In this study, three multi-scale heat conduction models including the Multi-region Layered (ML) model, Multi-region Non-layered (MN) model and Homogeneous model for FCM pellet were constructed. In the ML model, the random distributed TRISO fuel particles and coating layers are completely built. While the TRISO fuel particles with coating layers are homogenized in the MN model and the whole fuel pellet is taken as the homogenous material in the Homogeneous model. Taking the results by the ML model as the benchmark, the abilities of the MN model and Homogenous model to predict the maximum and average temperature were discussed. It was found that the MN model and the Homogenous model greatly underestimate the temperature of TRISO fuel particles. The reason is mainly that the conventional equivalent thermal conductivity (ETC) models do not take the internal heat source into account and are not suitable for the TRISO fuel particle. Then the improved ETCs considering internal heat source were derived. With the improved ETCs, the MN model is able to capture the peak temperature as well as the average temperature at a wide range of the linear powers (165 W/cm~ 415 W/cm) and the packing fractions (20%-50%). With the improved ETCs, the Homogenous model is better to predict the average temperature at different linear powers and packing fractions, and able to predict the peak temperature at high packing fractions (45%-50%).

• 한국방사성폐기물학회:학술대회논문집
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• 한국방사성폐기물학회 2005년도 춘계 학술대회
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• pp.352-361
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• 2005

In this study, conventional head-end processes of spent TRISO fuel have been reviewed to develope more effective treatment methods. The main concerns in the TRISO treatment are to effectively separate the carbon and SiC contained in the TRISO particles. The crush-burn scheme which was considered in the early stages of the development has been replaced by the crush-leach process because of $^{14}C$ problems as a second waste during the process. However there are still many obstacles to overcome in the reported processes. Hence, innovative thermomechanical concepts to breach the coating layers of the TRISO particle with a minimized amount of second waste are proposed in this paper and their principles are described in detail.

• 한국방사성폐기물학회:학술대회논문집
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• 한국방사성폐기물학회 2005년도 Proceedings of The 6th korea-china joint workshop on nuclear waste management
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• pp.92-106
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• 2005

The head-end processes of spent TRISO fuel have been reviewed to understand the current status and the limitations of the reported processes. The main concerns in the TRISO treatment are to effectively breach and separate the carbon and SiC layers composing the TRISO particles. The crush-bum scheme which was considered in the early stages of the development has been replaced by the crush-leach or $CO_2$ burning and the succeeding CO decomposition process because of a sequestration problem of $CO_2$ containing $^{14}C$. However there are still many obstacles to overcome in the reported processes. Hence, innovative thermomechanical and pyrochemical concepts to breach the coating layers of the TRISO particle with a minimized amount of second waste are proposed in this paper and their principles are described in detail.

• 한국세라믹학회지
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• 제47권6호
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• pp.590-597
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• 2010

HTGR using a TRISO coated particles as nuclear raw fuel material can be used to produce clean hydrogen gas and process heat for a next-generation energy source. For these purposes, a TRISO coated particle was prepared with 3 pyro-carbon (buffer, IPyC, and OPyC) layers and 1 silicone carbide (SiC) layer using a CVD technique on a spherical $UO_2$ kernel surface as a fissile material. In this study, a spherical $UO_2$ particle was prepared using a modified sol-gel method with a vibrating nozzle system, and TRISO coating fabrication was carried out using a fluidized bed reactor with coating gases, such as acetylene, propylene, and methyltrichlorosilane (MTS). As the results of this study, a spherical $UO_2$ kernel with a sphericity of 1+0.06 was obtained, and the main process parameters in the $UO_2$ kernel preparation were the well-formed nature of the spherical ADU liquid droplets and the suitable temperature control in the thermal treatment of intermediate compounds in the ADU, $UO_3$, and $UO_2$ conversions. Also, the important parameters for the TRISO coating procedure were the coating temperature and feed rate of the feeding gas in the PyC layer coating, the coating temperature, and the volume fraction of the reactant and inert gases in the SiC deposition.

• 한국정보처리학회:학술대회논문집
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• 한국정보처리학회 2006년도 춘계학술발표대회
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• pp.669-672
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• 2006

고온가스냉각 원자로에서는 고온 안정성 및 핵분열생성물 차단 성능이 우수한 TRISO(tri-tsotropic) 핵연료를 사용하고 있다. TRISO 핵연료 입자는 직경이 약 1 mm인 구 형태로 입자의 중심에는 직경 $0.5{\mu}m$의 핵연료 커널(kernel)이 포함되며 커널 외곽을 코팅 층이 에워싸고 있다. 이 코팅 층은 완충(buffer) PyC(pyrolytic carbon) 층, 내부 PyC 층, SiC 층, 그리고 외부 PyC 층으로 구성되어 있다. 각 코팅 층의 두께는 수십${\sim}$백 ${\mu}m$ 범위이며, 본 연구에서는 각 코팅 층의 두께를 비파괴적으로 측정하기 위하여 마이크로포커스 X-선 발생장치와 고해상도 X-선 평판(flat panel) 검출기로 구성된 정밀한 X-선 래디오그래피 장치를 구성하고, $UO_2$ 핵물질 대신에 $ZrO_2$를 커널로 사용한 모의 TRISO 핵연료 입자에 대한 래디오그래피 영상을 획득한 후 디지털 영상처리기술을 이용하여 코팅 층 사이의 경계선이 구분 가능하도록 영상을 개선하고 디지털 영상처리 알고리즘을 개발하여 코팅 층의 두께를 측정하였다.

• 한국정보처리학회:학술대회논문집
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• 한국정보처리학회 2005년도 추계학술발표대회 및 정기총회
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• pp.713-716
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• 2005

차세대 원자로로 부각되고 있는 고온가스냉각 원자로에서는 고온 안정성 및 핵분열생성물 차단 성능이 우수한 TRISO(Tri-Isotropic) 핵연료를 사용하고 있다. TRISO 핵연료 입자는 직경이 약 1mm인 구 형태로 입자의 중심에는 직경 $0.35^{\sim}0.6\;{\mu}m$의 핵연료 입자가 포함되며 입자 외곽을 코팅 층이 에워 싸고 있다. 이 코팅층은 완충(buffer) PyC 층, 내부 PyC 층, 외부 PyC 층으로 구성되어 있다. 각 코팅 층의 두께를 수십$^{\sim}$백 ${\mu}m$ 범위이며 사양으로 정해져 있어 핵연료 입자 제조 후 사양을 만족하는지를 검사해야 한다. 본 연구에서는 TRISO 핵연료 입자 정보를 컴퓨터로 생성하고 가상의 X-선 래디오그래피 방법을 이용하여 투시 영상을 구성한 후 Filtered Backprojection 기법을 이용하여 단면 영상을 재구성하고 이 단면 영상을 이용하여 코팅 층의 두께를 정밀하게 측정하기 위한 모의 실험을 수행하였다. 경계선이 불명확한 투시영상이 아닌 경계선이 명확한 재구성 단면 영상을 이용하여 코팅 층의 두께를 약 2.3% 이내의 오차율로 정밀하게 측정하였다.