• 한국신재생에너지학회:학술대회논문집
• /
• 한국신재생에너지학회 2011년도 춘계학술대회 초록집
• /
• pp.187.1-187.1
• /
• 2011

RDF(Refuse-Derived Fuel) is a fuel of pelletized form made of combustible solid wastes and can not only be used as alternative energy to fossil fuel but also solve troubles in thermal uses of incinerator. As the first stage for obtaining elementary data required to develop criteria of raw materials appropriate to RDF combustion facilities actively spread recently in Korea, preliminary experiments were conducted on CO, SOx, NOx and HCl production and reduction characteristics in combustion of RDF. RDF samples weighing 2~3 g per a sample were manufactured in a lab-scale way and combustion tests of RDF were carried out in electric furnace with quartz tube of 50 mm inside diameter.

• 대한기계학회논문집A
• /
• 제26권11호
• /
• pp.2305-2311
• /
• 2002

The pressure tube is a major component of the CANDU reactor, which supports nuclear fuel bundle and heavy water coolant. Pressure tubes are installed horizontally inside the reactor and only selected samples are periodically examined during in-service inspection. In this respect, a probabilistic safety assessment method is more appropriate fur the assessment of overall pressure tube safety. The failure behavior of CANDU pressure tubes, however, is governed by delayed hydride cracking which is the major difference from pipings and reactor pressure vessels. Since the delayed hydride cracking has more widely distributed governing parameters, it is impossible to apply a general PFM methodology directly. In this paper, a PFM methodology for the safety assessment of CANDU pressure tubes is introduced by applying Monte Carlo simulation in determining failure probability Initial hydrogen concentration, flaw shape and depth, axial and radial crack growth rate and fracture toughness were considered as probabilistic variables. Parametric study has been done under the base of pressure tube dimension and hydride precipitation temperature in calculating failure probability. Unstable fracture and plastic collapse are used for the failure assessment. The estimated failure probability showed about three-order difference with changing dimensions of pressure tube.

• Journal of Mechanical Science and Technology
• /
• 제15권9호
• /
• pp.1274-1280
• /
• 2001

The fretting wear behavior of the contact between Zircaloy-4 tube and Inconel 600, which are used as the fuel rod cladding and grid, respectively, in PWR nuclear power plants was investigated in air. In the study, number of cycles, slip amplitude and normal load were selected as the main factors of fretting wear. The results indicated that wear increased with load, slip amplitude and number of cycles but was affected mainly by the slip amplitude. SEM micrographs revealed the characteristics of fretting wear features on the surface of the specimens such as stick, partial slip and gross slip which depended on the slip amplitude. It was found that fretting wear was caused by the crack generation along the stick-slip boundaries due to the accumulation of plastic flow at small slip amplitudes and by abrasive wear in the entire contact area at high slip amplitudes.

• 한국소성가공학회:학술대회논문집
• /
• 한국소성가공학회 2005년도 추계학술대회 논문집
• /
• pp.247-250
• /
• 2005

The need for improved fuel efficiency, weight reduction has motivated the automotive industry to focus on aluminum alloys as a replacement for steel-based alloy. To cope with the needs for high structural rigidity with low weight, it is forecasted that substantial amount of cast components will be replaced by tubular parts which are mainly manufactured by the extruded aluminum tubes. The extrusion process is utilized to produce tubes and hollow sections. Because there is no weld seam, the circumferential mechanical properties may be uniform and advantageous for hydroforming. However the possibility of the occurrence of a surface defect is very high, especially due to the temperature increase from forming at high pressure when it comes out of the bearing and the roughness of the bearing, which cause the surface defects such as the dies line and pick-up. And when forming a extruded aluminum tube, the free surface of the tube becomes rough with increasing plastic strain. This is well known as orange peel phenomena and has a great effect not only on the surface quality of a product but also on the forming limit. In an attempt to increase the forming limit of the tubular specimen, in the present paper, surface asperities generated during the hydroforming process are polished to eliminate the weak positions of the tube which lead to a localized necking. It is shown that the forming limit of the tube can be considerably improved by simple method of polishing the surface roughness during hydroforming. And also the extent of the crack propagation caused by dies lines generated during the extrusion process is evaluated according to the deformed shape of the tube.

• Nuclear Engineering and Technology
• /
• 제49권8호
• /
• pp.1740-1747
• /
• 2017

To investigate allowable peak cladding temperature and hoop stress for maintenance of cladding integrity during interim-dry storage and subsequent transport, zirconium alloy cladding tubes were hydrogen-charged to generate 250 ppm and 500 ppm hydrogen contents, simulating spent nuclear fuel degradation. The hydrogen-charged specimens were heated to four peak temperatures of $250^{\circ}C$, $300^{\circ}C$, $350^{\circ}C$, and $400^{\circ}C$, and then cooled to room temperature at cooling rates of $0.3^{\circ}C/min$ under three tensile hoop stresses of 80 MPa, 100 MPa, and 120 MPa. The cool-down specimens showed that high peak heat-up temperature led to lower hydrogen content and that larger tensile hoop stress generated larger radial hydride fraction and consequently lower plastic elongation. Based on these out-of-pile cladding tube test results only, it may be said that peak cladding temperature should be limited to a level < $250^{\circ}C$, regardless of the cladding hoop stress, to ensure cladding integrity during interim-dry storage and subsequent transport.

• 자원리싸이클링
• /
• 제30권6호
• /
• pp.12-18
• /
• 2021

수성가스 전환 반응은 가스화로 생성된 합성 가스에 수소 생산 증가와 H₂/CO 비율 제어를 위해 수증기를 첨가하는 가스화 후속 공정이다. 본 연구에서는 RPF(Refuse plastic fuel) 가스화 시스템의 합성가스를 대상으로 수성가스 전환 반응을 연구하였다. 수성가스 전환 반응은 촉매를 이용하여 high temperature shift(HTS) 와 low temperature shift(LTS) 반응에 대하여 lab scale 관형 반응기를 이용하여 반응 온도, steam/carbon ratio, 유량의 변화가 H₂ 생성과 CO 전환율에 미치는 영향을 조사하였다. 운전 온도는 HTS 시스템이 250-400℃, LTS 시스템이 190-220℃이며 steam/carbon ratio는 1.5-3.5로 변화시켰다. 반응 모의 가스의 농도는 RPF 합성가스의 농도를 기준으로 CO, 40vol%, H₂, 25vol%, CO₂, 25vol%이다. 반응 온도와 steam/carbon ratio가 증가함에 따라 CO 전환율 및 H₂ 생성량이 증가하고, 유량이 증가하면 촉매층의 체류시간 단축으로 CO 전환율과 H₂ 생성량이 감소하였다.

• Nuclear Engineering and Technology
• /
• 제20권2호
• /
• pp.88-104
• /
• 1988

이차원의 유한요소법을 이용하여 axisymmetric R-$\theta$system으로 나누어서 정상과 부하추종 운전시에 핵연료 페렛트와 피복관의 열역학적 거동을 분석하기 위해서 FURA전산코드를 개발하였다. 온도분포와 내부압력을 정확히 계산하기 위해서 페렛트와 피복관의 변형과 핵분열의 기체방출을 전체 핵연료봉 길이로 고려하였다. 열역학적 평 형방정식을 얻기 위해서 Galerkin's Technique과 가상일의 원리를 사용하였고 역학적 해석을 위해서 탄성-소성, 크리프뿐만아니라 스엘링, 재배열, 고밀화 현상등을 고려하였다. 기하학적 모델에서는 4-결점 요소라 페레트 길이의 1/2만을 택하였다. 비선형식을 안정하게 해석하기 위해서 음해법을 도입하여 뉴튼-랩손 반복법을 적용하였다 이 코드의 검증은 해석해와 실험데이타로 비교하였다. 핵연료봉의 일반적인 거동은 axisymmetry system으로 계산하였고 균열된 페레트에 접촉하는 피복관의 거동은 R-$\theta$system을 사용하였다. 부하추종에 의한 피복관의 변형시효의 민감도는 출력율, 진동수, 진폭등으로 비교하였다.

• Nuclear Engineering and Technology
• /
• 제21권2호
• /
• pp.111-122
• /
• 1989

고온 수증기(1323 K)분위기에서 산화시킨 지르칼로이-4 피복관으로, 구리 맨드렐 팽창실험(Copper Mandrel Expension Test)을 변형률(Strain Rate)이 $3.0\times10^{-5}$/sec일때 673-1173 K 온도 범위에서 수행하였다. 본 연구에서, 산화매개변수(Ki)는 시간(t)의 제곱근에 비례하고 $(Ki=\delta_{kit}\frac{1}{2}$), 비례상수($\delta_{ki}$)는 무게증가(Weight Gain), Zr02의 두께, $\alpha$(0) 층에 대하여 각각 0.281, 2.82, 2.313을 사용하였다. 지르칼로이-4의 고온(873-1073 K) 소성변형에 의한 활성화 에너지는 Zr02가 높은 강도를 갖기 때문에 산화 시간이 5분에서 60분으로 증가함에 따라 251 KJ/mol에서 323KJ/mo1로 증가하였다. 산화막 두께, K와 항복 응력의 관계는 ($\sigma/C)^n=K^m$exp (Q/RT)인 관계식을 얻었다. 여기서 n은 6.9, m은 5.7, 그리고 Q가 251, 258, 316, 323 KJ/mo1에 대해 C는 0.155, 0.138, 0.051, 0.046MPa이다.