• 제목/요약/키워드: Zr-2.5Nb pressure tubes

검색결과 32건 처리시간 0.107초

유한요소해석을 이용한 지르코늄 압력관의 블리스터 생성 및 성장 해석 (Formation and Growth Estimation of Blister in Zr-2.5Nb Pressure Tubes based on Finite Element Analysis)

  • 허남수;김윤재;김영진;김영석;정용무
    • 대한기계학회:학술대회논문집
    • /
    • 대한기계학회 2003년도 추계학술대회
    • /
    • pp.1133-1138
    • /
    • 2003

  • The pressure tubes, which contain high temperature heavy water and fuel, are within the core of a CANDU nuclear reactor, and are thus subjected to high stresses, temperature gradient, and neutron flux. Further, it is well known that pressure tubes of cold-worked Zr-2.5Nb materials result in hydrogen diffusion, which create fully-hydrided regions (frequently called Blister). Thus a proper investigation of hydrogen diffusion within zirconium-alloy nuclear components, such as CANDU pressure tube and fuel channels is essential to predict the structural integrity of these components. In this respect, this paper presents numerical investigation of hydrogen diffusion to quantify the hydrogen concentration for blister growth of CANDU pressure tube. For this purpose, coupled temperature-hydrogen diffusion analyses are performed by means of two-dimensional finite element analysis. Comparison of predicted temperature field and blister with published test data shows good agreement.

  • PDF

Microstructure and Mechanical Property of Irradiated Zr-2.5Nb Pressure Tube in Wolsong Unit-1

  • 김영숙;안상복;오동준;김성수;정용무
    • 소성∙가공
    • /
    • 제8권3호
    • /
    • pp.241-241
    • /
    • 1999

  • With the aim of assessing the degradation of Zr-2.5Nb pressure tubes operating in the Wolsong unit-1 nuclear power plant, characterization tests are being conducted on irradiated Zr-2.5Nb tubes removed after 10-year operation. The examined tube had been exposed to temperatures ranging from 264 to 306℃ and a neutron fluence of 8.9×$10^{21}$ n/cm²(E>1 MeV) at the maximum. Tensile tests were carried out at temperatures ranging from RT to 300℃. The density of a-type and c-type dislocations was examined on the irradiated Zr-2.5Nb tube using a transmission electron microscope. Neutron irradiation up to 8.9×$10^{21}$ n/cm²(E>1 MeV) yielded an increase in a-type dislocation density of the Zr-2.5Nb pressure tube to 7.5×$10^{14} m^{-2}$, which was highest at the inlet of the tube exposed to the low temperature of 275℃. In contrast, the c-component dislocation density did not change with irradiation, keeping an initial dislocation density of 0.8×$10^{14} m^{-2}$ over the whole length of the tube. As expected, the neutron irradiation increased mechanical strength by about 17-26% in the transverse direction and by 34-39% in the longitudinal direction compared to that of the unirradiated tube at 300℃. The change in the mechanical properties with irradiation is discussed in association with the microstructural change as a function of temperature and neutron fluence.

Zr-2.5Nb 압력관의 휘어진 CT시편으로 측정한 J 저항곡선의 정확도에 관한 연구 (A Study on Accuracy of J-Resistance Curves Measured with Curved Compact Tension Specimen of Zr-2.5Nb Pressure Tube)

  • 윤기봉;박태규;김영석
    • 대한기계학회논문집A
    • /
    • 제27권11호
    • /
    • pp.1986-1996
    • /
    • 2003

  • Methodology based on the elastic-plastic fracture mechanics has been widely accepted in predicting the critical crack length(CCL) of pressure tubes of CANDU nuclear plants. A conservative estimate of CCL is obtained by employing the J-resistance curves measured with the specimens satisfying plane strain condition as suggested in the ASTM standard. Due to limited thickness of the pressure tubes the curved compact tension(CT) specimens taken out from tile pressure tube have been used in obtaining J-resistance curves. The curved CT specimen inevitably introduce slant fatigue crack during precracking. Hence, effect of specimen geometry and slant crack on J-resistance curve should be explored. In this study, the difference of J integral values between the standard CT specimens satisfying plane strain condition and the nonstandard curved CT with limited thickness (4.2mm) is estimated using finite element analysis. The fracture resistance curves of Zr-2.5Nb obtained previously by other authors are critically discussed. Various finite element analysis were conducted such as 2D analysis under plane stress and plane strain conditions and 3D analysis for flat CT, curved CT with straight crack and curved CT with slant crack front. J-integral values were determined by local contour integration near the crack tip, which was considered as accurate J-values. J value was also determined from the load versus load line displacement curve and the J estimation equation in the ASTM standard. Discrepancies between the two values were shown and suggestion was made for obtaining accurate J values from the load line displacement curves obtained by the curved CT specimens.

  • https://doi.org/10.3795/KSME-A.2003.27.11.1986 인용 PDF KSCI

Formation and Growth of Hydride Blisters in Zr-2.5Nb Pressure Tubes

  • Cheong, Yong-Moo;Gong, Un-Sik;Choo, Ki-Nam;Kim, Sung-Soo;Kim, Young-Suk
    • Nuclear Engineering and Technology
    • /
    • 제33권2호
    • /
    • pp.192-200
    • /
    • 2001

  • Hydride blisters were formed on the outer surface of Zr-2.5Nb pressure tube by a non- uniform steady thermal diffusion process. A thermal gradient was applied to the pressure tube with a heat bath kept at a temperature of 415$^{\circ}C$ and an aluminum cold finger cooled with flowing water of 15$^{\circ}C$. Optical microscopy and tree-dimensional laser profilometry were used to characterize the hydride blisters with different hydrogen concentrations and thermal diffusion time. Hydride blisters were expected to start at a hydrogen concentration of 30 - 70 ppm and a thermal diffusion time of 4 - 6$\times$10$^{5}$ sec. The hydride blister size increases with higher hydrogen concentrations and longer thermal diffusion time . Some of the samples revealed cracks on the hydride blisters. The ratio of hydride blister depth to height was estimated as approximately 8: 1.

  • PDF