• Title/Summary/Keyword: Zr-2.5Nb Pressure Tube

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Delayed Hydride Cracking Velocity of CANDU Zr-2.5Nb Tubes in High Temperature Water

  • Kim Young Suk;Cho Sun Young;Im Kyung Soo;Cheong Yong Moo;Kim Sung Soo
    • Nuclear Engineering and Technology
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    • v.35 no.3
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    • pp.206-213
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    • 2003

  • This study focuses on an understanding of the environmental effect on delayed hydride cracking velocity (DHCV) of CANDU Zr-2.5Nb tubes. To simulate DHC susceptibility of the Zr-2.5Nb tubes in reactor operating conditions, DHC tests were successfully carried out in pressurized water at 180 and $250^{\circ}C$ using a self-designed autoclave for the first time. Using 17 mm compact tension specimens electorlytically charged to 34 and 60 ppm H, 3 to 7 DHCV data were determined in water at both temperatures and compared to those determined in air that were already confirmed to be valid through a round robin test on DHCV of Zr-2.5Nb tubes sponsored by a IAEA coordinated research program. The pressurized water environment has little effect on DHCV of Zr-2.5Nb tube in water at both temperatures even though DHCV is slightly lower in water than that in air. The lower DHCV of the Zr-2.5Nb tube during short-term tests is discussed in viewpoint of the cooling rate from the peak temperature to the test temperature.

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

  • Yoon, Kee-Bong;Park, Tae-Gyu;Kim, Young-Suk
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.27 no.11
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    • pp.1986-1996
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    • 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