• Korean Journal of Materials Research
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• v.29 no.8
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• pp.483-490
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• 2019

Currently, the Korean nuclear industry uses ZIRLO as material for nuclear fuel cladding(zirconium alloy). KEPCO Nuclear Fuel is in the process of developing a HANA alloy to enable domestic production of cladding. Cladding manufacture involves multistage heat treatments and pickling processes, the latter of which is vital for the removal of defects and impurities on the cladding surface. SMUT that forms on the cladding surface during such pickling process is a source of surface defects during heat treatment and post-treatment processes if not removed. This study analyzes ZIRLO, HANA-4, and HANA-6 alloy claddings to extensively study the SEM/EDS, XRD, and particle size characteristics of SMUT, which are second phase particles that are formed on the cladding surface during pickling processes. Using the analysis results, this study observes SMUT formation characteristics according to Nb concentration in Zr alloys during the washing process following the pickling process. In addition, this study observes SMUT removal characteristics on cladding surfaces according to concentrations of nitric acid and hydrofluoric acid in the acid solution.

• Proceedings of the Korea Society for Energy Engineering kosee Conference
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• 1993.11a
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• pp.109-109
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• 1993

CANDU 원자로 지역별 대표 핵연료봉 1개에 대하여 열행태를 해석할 수 있는 '평균 단일 핵연료(ASF : Averaged Single Fuel)' 모델을 우선 제안하였다. 핵 연료봉 하나를 12 개 동일 체적의 환형 격자로 나누고 시공간을 고려하는 전진 유한 미분 해석을 적용하여 핵연료봉내에서의 열적 변이를 모사 하였다. 핵연료의 전도도 및 비열은 온도에 종속함이 가정되었다. 주어진 열출력에 대하여, 핵연료와 피복관내의 정상상태 온도분포를 산출하였고 주어진 냉각재 온도 및 표면 열 전달 계수에 대하여 핵연료봉 단위 길이당 저장열을 계산하였다. 초기 온도 분포의 임의 값에 대하여, 시간 단계별 열출력 및 열전달 계수 변이에 따른 저장열, 온도 분포, 냉각재료의 출력과 피복관 온도 변이를 계산하였다. 이후 ASF 모델을 CANDU 14개 지역 출력 특성의 실제적 모사 및 해석이 가능하도록, 14개 지역 대표 핵연료봉모델 모두를 동시에 포함하는 '다영역 핵연료(MZF : Multi Zone Fuel)' 모델로 확장하였다.

• Nuclear Engineering and Technology
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• v.21 no.2
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• pp.143-149
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• 1989

In order to investigate the in-reactor performance of the 14$\times$14 PWR fuel burner: for 3 cycles in power reactor, non-destructive examination was carried out in KAERI Hot Facility. The results obtained are as follows. 1) The surface of middle and bottom parts of the fuel rod was dark and the upper part was gray. 2) Severe defect such as through-hole was not found. 3) The diameter of rod was shrinked by about 0.65%, while the length was increased by about 0.55% Compared with the design values. 4) The burnup was decreased by about 2% at the inconel grid region compared to other parts.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2001.09a
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• pp.41-46
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• 2001

요오드나 세순 같은 핵종들은 고용해도 핵 종들로서 사용 후 핵연료 내 피복관 이나 연료 결정 경계면에 위치하고 있다가 고준위 방사성폐기물 처분 후 지하수가 용기를 부식시키고 용기 내부로 침투하면 고용해도를 가지고 유출된 후 공학적, 천연 방벽을 통해 최종적으로 유출되게 된다. 본 연구에서는 한국원자력연구소에서 개발한 MASCOT-K글 이용하여 고용해도 핵 종들이 조화 유출과 고용해도 유출할 경우 유출 량을 평가 분석해 보았다. 평가 결과 요오드와 같은 고용해도 핵 종인 경우 전체 핵 종 재고량의 최대 10%만이 고용해도 유출을 하지만 그 영향은 조차 유출에 비해 훨씬 중요한 것으로 판명되었다. 이러한 결과를 바탕으로 현재 국내 고 준위 처분 환경에서 보수적인 시나리오로 주목받고 있는 우물 굴착 시나리오를 대상으로 우물까지의 거리 등 입력 자료의 불확실성을 평가해 보았다. 36,000 톤의 사용 후 핵연료를 처분 대상으로 했을 때 성능 평가 결과는 현재 처분 개념이 안전함을 입증한다.

• Tribology and Lubricants
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• v.25 no.4
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• pp.250-255
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• 2009

Oxidation characteristics of Zirlo and Zircaloy-4 tubes, which are widely used as nuclear power fuel cladding, are studied in steam environment up to $1200^{\circ}C$. Oxidation resistances are compared in terms of the mass increase due to the absorption of oxygen. The evolution of microscopic structure accompanied with the oxidation process is investigated. Also, the influence of oxidation on the fretting wear characteristics of the tubes is studied. Piezo-electrically actuated rig is employed to fret the tubes with cross-contacting arrangement. Wear scar is observed and measured, by using microscopes and a 3D-profiler. The results of fretting wear are quantified in terms of scar size, wear volume and wear coefficient, and compared for the three different tube materials of oxidated Zirlo, virgin Zirlo and Zircaloy-4.

• Proceedings of the KSME Conference
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• 2001.06a
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• pp.489-494
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• 2001

The fuel of light water reactor used far several years at high temperature and pressure, so it needs to clad with high corrosion resistance material. The cladding materials need low absorption of a neutron and high corrosion resistance. Cladding materials used Zircaloy-2 in Boiling Water Reactor, Zircaloy-4 in Pressurized Water Reactor and Zirlo has good for long term corrosion. If fracture of cladding tube occured during operation, it caused disaster. So it is needed to estimate of integrity fur cladding materials. In this paper, tension characteristics of cladding materials are investigate which is basic research far fracture characteristic. Also analysis of residual stress effect between tube type(original type) specimen and flattened type specimen.

• Proceedings of the Korean Nuclear Society Conference
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• 1997.10a
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• pp.516-521
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• 1997

국내개발 액체금속로 KALIMER 노심으로 설계한 전기출력 150 MWe (열출력 392 MWth)의 U-Zr이원합금핵연료 사용 소형노심에 대하여 열수력 특성을 분석하고, 그 결과를 전기출력 333 MWe (열출력 840 MWth)의 중형노심설계 특성과 비교ㆍ분석하였다. 분석에는 국내개발 액체금속로 KALIMER 노심설계기술 개발의 일환으로서 개발한 개념설계 초기 단계에서의 노심 열수력 특성 분석 방법을 사용하였다. 열수력 특성 분석은 먼저 각 집합체의 최고 선출력에 따라 유량그룹을 설정하고, 각 집합체의 최고온도 연료봉에 대하여 냉각재 온도, 피복관 중심온도, 핵연료 중심온도 등을 계산하는 방식으로 수행하였다. 특성분석 결과 두 노심 모두 노심내 출력분포를 더욱 평탄화 하고, 노심핵연료 영역에 대한 반경방향 블랑？ 영역의 출력비율을 높이는 작업이 필요하다.

• Nuclear Engineering and Technology
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• v.20 no.3
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• pp.189-196
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• 1988

This study investigates the effect of fuel pellet eccentricity on fuel rod thermal performance under the steady state condition. The governing equations in the fuel pellet and the cladding region are set up in 2-dimensional cylindrical coordinate (r, $\theta$) and are solved by finite element method. The angular-dependent heat transfer coefficient in the gap region is used in order to account for the asymmetry of gap width. Material propeties are used as a function of temperature and volumetric heat generation as a function of radial position. The results show the increase of maximum local heat flux at the cladding outer surface and the decrease of maximum and average fuel temperatures due to eccentricity. The former is expected to affect the uncertainties in the minimum DNBR calculation. The latter two are expected to reduce the possibility of fuel melting and the fuel stored energy. Also, the fuel pellet eccentricity introduces asymmetry in fuel pellet temperature and movement of the location of maximum fuel pellet temperature.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.41 no.5
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• pp.375-380
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• 2017

This paper reports the results of an acceleration test to predict the contact-induced failure that could occur at the cylinder-to-hole joint for the fuel rod of a sodium-cooled fast reactor (SFR). To incorporate the fuel life of the SFR currently under development at KAERI (around 35,000 h), the acceleration test method of reliability engineering was adopted in this work. A finite element method was used to evaluate the flow-induced vibration frequency and amplitude for the test parameter values. Five specimens were tested. The failure criterion during the life of the SFR fuel was applied. The S-N curve of the HT-9, the material of concern, was used to obtain the acceleration factor. As a result, a test time of 16.5 h was obtained for each specimen. It was concluded that the $B_{0.004}$ life would be guaranteed for the SFR fuel rods with 99％ confidence if no failure was observed at any of the contact surfaces of the five specimens.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.26 no.1
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• pp.55-62
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• 2016

Nuclear fuels are always exposed to hot temperature and high speed coolant flow during the reactor operation. Thus the fuel rod accompanies small amplitude vibration due to the turbulent flow. The random vibration causes friction between the fuel rod and the grid structure which provides the lateral supports. The friction is critical to the fuel rod fretting wear, and it degrades fuel performance when a severe wear is developed. LuGre friction model is introduced in the paper, and the performance was evaluated comparing to the classical Coulomb model. It is shown that the developed friction force considering the Coulomb friction is not enough to stop or delay the motion while the stick-slip can be simulated using LuGre friction model. Numerical solutions of the two dimensional spacer grid cell model with the modern friction are also reviewed, and it is discussed that the new friction model simulates well the nonlinear mechanism.