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http://dx.doi.org/10.3795/KSME-A.2004.28.8.1109

A Correlation of Striation Spacing and DHC Velocity in Zr-2.5Nb Tubes  

Choi Seung Jun (한국원자력연구소, 지르코늄팀)
Ahn Sang Bok (한국원자력연구소, 지르코늄팀)
Park Soon Sam (한국원자력연구소, 지르코늄팀)
Kim Young Suk (한국원자력연구소, 지르코늄팀)
Publication Information
Transactions of the Korean Society of Mechanical Engineers A / v.28, no.8, 2004 , pp. 1109-1115 More about this Journal
Abstract
The objective of this study is to elucidate what governs delayed hydride cracking (DHC) in Zr-2.5Nb tubes by correlating the striation spacings with DHCV(DHC Velocity). To this end, DHC tests were conducted on the compact tension specimens taken from the Zr-2.5Nb tubes at different temperatures ranging from 100 to $300^{\circ}C$ with a 3 to 6 data set at each test conditions. The compact tension specimens were electrolytically charged with 27 to 87 ppm H before DHC tests. After DHC tests, the striation spacings and DHCV were determined with the increasing the test temperature and yield strength. The striation spacing and DHCV increased as a function of yield $strength^2$ and the temperature. Since the plastic zone size ahead of the crack tip can be represented by ${\sim}(K_{IH}/{\sigma}_{Y})^2$, we conclude that the striation spacing is governed by the plastic zone size which in turn determines a gradient of hydrogen concentration at the crack tip. The relationship between the plastic zone size and the striation spacing was validated through a complimentary experiment using double cantilever beam specimens. Two main factors to govern DHCV of Zr-2.5Nb tubes are concluded to be hydrogen diffusion and a hydrogen concentration gradient at the crack tip that are controlled by temperature and yield strength, respectively. The activation energy of DHCV in the Zr-2.5Nb tubes is discussed on the basis of temperature dependency of hydrogen diffusion and the striation spacing.
Keywords
DHC; Delayed Hydride Cracking; Striation Spacing; Zr-2.5Nb; Pressure Tubes;
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