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Zirconium alloy cladding materials typically contain circumferential hydrides that may be reoriented to align along the radial direction when the cladding tubes are heated above and then cooled below the solvus temperature. The objectives of this study were to investigate the critical stress levels required to cause hydride reorientation (HRT) and to characterize the fracture resistance of Zircaloy-2 after hydride reorientation. HRT heat-treatment was performed on hydrogen-charged Zircaloy-2 specimens at 593 K (320 °C) or 623 K (350 °C) for 1 to 2 hours, followed by cooling to 473 K (200 °C). Fracture testing was conducted on hydride-reoriented three-point bend specimens at 473 K (200 °C) using an in situ loading stage inside a scanning electron microscope. Direct observations indicated that the reoriented hydrides, which ranged from ≈1 to 22 μm in lengths, were more prone to fracture at larger sizes (>10 μm) compared to smaller sizes (<0.5 μm). The reoriented hydrides reduced fracture resistance through a void nucleation, growth, and coalescence process at the crack tip. The resulting crack-resistance curves for Zircaloy-2 with reoriented hydrides decrease from 38 to 21 MPa(m) with increasing hydrogen contents from 51 to 1265 wt ppm hydrogen. [ABSTRACT FROM AUTHOR]

Objective: To investigate the clinical application of 256 multi-slice spiral computed tomography angiography (MSCTA) technique in the preoperative evaluation of mesenteric angiography in order to provide a reference to vessel anatomy and dissociation in laparoscopic radical operation for colorectal carcinoma., Methods: Clinical data of 50 patients with colorectal cancer who underwent preoperative MSCTA+FDCT and laparoscopic curative operation at our hospital from October 2013 to March 2015 were collected (MSCTA group). The evaluation item was visualization of mesenteric artery, which was compared with the findings under laparoscopic surgery. Meanwhile, another 50 colorectal cancer patients undergoing laparoscopic radical operation by the same surgeon team without preoperative MSCTA examination were used as control(control group). Clinical data were compared between the two groups., Results: MSCTA precisely and correctly demonstrated anatomy and variations of the mesenteric artery and relative nutrient vessel in carcinoma. The angiography reconstruction images were consistent with the visual anatomy and variation from laparoscopic findings, whose diagnostic conformity rate of 100%. As compared to control group, operative time was shorter [(195.0±23.2) minutes vs.(218.0±19.6) minutes, t=8.326, P=0.015], and blood loss was less[(168.1±18.8) ml vs. (206.5±14.3) ml, t=-19.369, P=0.002] in MSCTA group. Differences of number of harvested lymph node, postoperative complication morbidity, postoperative hospital stay and hospitalization cost were not significant between two groups(all P>0.05)., Conclusion: Preoperative MSCTA can demonstrate anatomy and variations of the mesenteric artery precisely and correctly, thus it is beneficial to shorten the operation time and to reduce blood loss.