• Nuclear Engineering and Technology
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• v.41 no.2
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• pp.179-186
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• 2009

This paper presents a thermal creep test under internal pressure and post-test characterization performed on high burnup (68 MWd/kgU) ZIRLO. This research has been done by the CSN, ENRESA, and ENUSA in order to investigate the behavior of advanced cladding materials in contemporary PWRs at higher burnup under dry cask storage conditions. Also, to investigate the hydride reorientation, the cool-down of the samples after the test has been done in a coordinated manner with the internal pressure. The creep results obtained are consistent with the expected behavior from reference CWSR material, Zr-4. During the test, the material retained significant ductility: one specimen leaked during the test at an engineering strain of the tube section of 17%; remarkably, the crack closed due to de-pressurization. Although significant hydride reorientation occurred during the cool-down under pressure, no specimen failed during the cool-down.

• Journal of Powder Materials
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• v.17 no.5
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• pp.385-389
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• 2010

Titanium powders have been usually produced by de-hydrogenating treatment in vacuum with titanium hydride ($TiH_2$) powders prepared by milling of hydrogenated sponge titanium, $TiH_x$. The higher stoichiometry of x in $TiH_x$, whose maximum value is 2, is achieved, crushing behavior is easier. $TiH_x$ powder can be, therefore, easy to manufactured leading to obtain higher recovery factor of it. In addition, contamination of the powder can also minimized by the decrease of milling time. In this study, the hydrogenation behavior of sponge titanium was studied to find the maximum stoichiometry. The maximum stoichiometry in hydride formation of sponge titanium could be obtained at $750^{\circ}C$ for 2 hrs leading to the formation of $TiH_{{\sim}1.99}$ and the treating temperatures lower or higher than $750^{\circ}C$ caused the poor stoichiometries by the low hydrogen diffusivity and un-stability of $TiH_x$, respectively. Such experimental behavior was compared with thermodynamically calculated one. The hydrogenated $TiH_{1.99}$ sponge was fully ball-milled under -325 Mesh and the purity of pure titanium powders obtained by de-hydrogenation was about 99.6%.

• Korean Journal of Materials Research
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• v.15 no.5
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• pp.306-312
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• 2005

The hydrogen sorption properties of $Ti_{0.3}Zr_{0.2}V_{0.5}$ NEC(non-evaporable getter) alloy and its hydrides were evaluated at room temperature. The alloy and hydride powders were prepared by the Hydride-DeHydride(HDH) method. The hydrogen sorption speed of $Ti_{0.3}Zr_{0.2}V_{0.5}$ alloy was measured to increase with the amounts of hydride phase in the getter. The hydrogen sorption speeds of $Ti_{0.3}Zr_{0.2}V_{0.5},\;(Ti_{0.3}Zr_{0.2}V_{0.5})H_{1.52},\;and\;(Ti_{0.3}Zr_{0.2}V_{0.5})H_{1.94}$ were 2.22, 3.14 and 5.08 liter/sec, respectively. The unexpected enhancement of hydrogen sorption speed with the presence of the hydride phase is considered to be due to the pre-saturation of hydrogen trap sites which can retard the diffusion of hydrogen in the alloy.

• Nuclear Engineering and Technology
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• v.41 no.2
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• pp.171-178
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• 2009

The rate of delayed hydride cracking (DHC), V, has been measured in cold-worked and stress-relieved Zircaloy-4 fuel cladding using the Pin-Loading Tension technique. At $250^{\circ}C$ the mean value of V from 69 specimens was $3.3({\pm}0.8)x10^{-8}$ m/s while the temperature dependence up to $275^{\circ}C$ was described by Aexp(-Q/RT), where Q is 48.3 kJ/mol. No cracking or cracking at very low rates was observed at higher temperatures. The fracture surface consisted of flat fracture with no striations. The results are compared with previous results on fuel cladding and pressure tubes.

• Korean Journal of Materials Research
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• v.15 no.2
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• pp.79-84
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• 2005

The lowest activation temperature of a commercial vacuum getter reported so far in literature was about $400^{\circ}C$. Recently, $Ti_{0.3}Zr_{0.2}V_{0.5}$ alloy has been reported to exhibit the activation temperature lower than $200^{\circ}C$ when they are prepared as thin film. In this study, the alloy was prepared as bulk form and its activation temperature and hydrogen sorption properties were investigated in compliance with a standard method. The alloy powder was prepared by arc melting and subsequent HDH(Hydride-DeHydride) process. The activation temperature of the alloy was estimated from the ultimate pressure-temperature curve and located between $150^{\circ}C\;and\;200^{\circ}C$. The hydrogen sorption speed measured by an orifice method was 0.895 liter/sec which is comparable to thin film of same composition.

• Journal of Powder Materials
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• v.24 no.1
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• pp.29-33
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• 2017

Titanium carbide (TiC) powders are successfully synthesized by carburization of titanium hydride ($TiH_2$) powders. The $TiH_2$ powders with size lower than $45{\mu}m$ (-325 Mesh) are optimally produced by the hydrogenation process, and are mixed with graphite powder by ball milling. The mixtures are then heat-treated in an Ar atmosphere at $800-1200^{\circ}C$ for carburization to occur. It has been experimentally and thermodynamically determined that the de-hydrogenation, "$TiH_2=Ti+H_2$", and carburization, "Ti + C = TiC", occur simultaneously over the reaction temperature range. The unreacted graphite content (free carbon) in each product is precisely measured by acid dissolution and by the filtering method, and it is possible to conclude that the maximal carbon stoichiometry of $TiC_{0.94}$ is accomplished at $1200^{\circ}C$.

• Analytical Science and Technology
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• v.15 no.5
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• pp.439-444
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• 2002

DE-O-V ICP-AES has been studied for the analytical characteristics of As, Se, and Ge with PN, USN and HG. Effect of $NaBH_4$ and HCl on the signal intensity of As, Se and Ge with HG and E-O-V ICP-AES were closely investigated. The sensitivities of As, Se and Ge with HG were much greater than those with PN and USN. Accordingly, the detection limits of the elements with HG were lower by a factor of 100 and 10 than PN and USN, respectively.

• Korean Journal of Materials Research
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• v.15 no.4
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• pp.257-262
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• 2005

Nano-sized ZrVFe alloy powders were prepared by the ablation of powder compact in alcobol using a Nd-YAG pulsed Laser. The $Zr_{57}V_{35.}8Fe_{7.2}$ alloy commercially designated as ST707 has long been known as the ideal solution for various vacuum applications. The target for the ablation was sintered pellets of $Zr_{57}V_{35.}8Fe_{7.2}$ alloy powder. The alloy was prepared by arc melting and Hydride-DeHydride method. The ablated powders were mostly circular having fairly large size distribution smaller than 200 nm in all cases. The X-ray diffraction study revealed that the ablated alloy retained the crystal structure of the target alloy. Nevertheless, Fe and V contents in the ablated powder were lower than those in the target alloy. This was believed to result from the high vapour pressures of Fe and V compared to that of Zr. The size of the powders ablated at high energy fluence tends to decrease due at least partly to the breakdown of previously made ones.