Papers by Keyword: Zircaloy-2

Abstract: SINQ Target-11 was in operation in 2015 and 2016. It was shut down due to an incident in June 2016, during which the pressure drop in the cooling water loop increased significantly, and meanwhile, the activity of the cooling water also increased tremendously. The evidence indicated a serious failure of the target. As this is the first severe failure since SINQ came into operation in 1997, some post-irradiation examinations (PIE) were performed to analyze the failure mechanisms.

Abstract: The Indian PHWR uses Zr-2.5% Nb pressure tubes and its in-reactor performance mainly irradiation creep and growth depends strongly on its microstructure. A detailed microstructural examination was carried out on unirradiated pressure tubes off-cuts and an irradiated pressure tube S-07 of KAPS-2 (operated for 8 effective full power years (EFPYs)), Microstructural characterization was carried out using transmission electron microscopy. Microstructual observation of un-irradiated off-cuts shows the lamellar morphology of the -Zr along with the -phase present as stingers between two alpha laths as well as fine and coarse beta globules. The size of -Zr lamellae was found to be in the range from 0.17 to 0.2 m, 1.8 to 2.4 m and 1.7 to 2.8 m in the radial, circumferential and axial direction respectively (aspect ratio of 1:7:8). TEM-EDS analysis showed composition of the  phase tin the range of 15-50 wt%Nb. The irradiated pressure tube samples obtained from 13 locations were showing average alpha grain width, grain length and aspect ratio in the range of 0.17-0.27 micron, 1.7-2.3 micron and 7.1-8.5 respectively. Extensive modification in beta morphology could be seen at the high flux and high temperature regions. The  phase was observed to have globulised completely in many regions. They were present at the interface of -Zr laths as well as within the lath. The Nb concentration of the  phase appeared to have increased as the volume fraction had reduced. The microstructure details of irradiated and un-irradiated pressure tubes obtained in this study is expected to help in modeling the dimensional change occurring during irradiation in reactor.

Abstract: Zircaloy-2, an useful nuclear material is studied here by photoacoustics to correlate with the measurements of X-rays. The microstructure variations observed in X-rays could be explained on the basis of thermal diffusivity measured by photoacoustics technique.

Abstract: The nuclear material, Zircaloy-2 is studied here by photoacoustics and the results are correlated with ultrasonic measurements and metallographic microstructures. Precipitation of hard intermetalics and formation of α-martensite, due to thermal aging are also explained through photoacoustic studies.

Abstract: Hexagonal close-packed and lower symmetry metals often exhibit anisotropic mechanical properties because the dominant slip system forbids slip in certain lattice directions. Rod-textured Zircaloy-2 is a model system which can act as a road map for understanding more complex cases. In this case prism slip is dominant and pyramidal slip is only initiated at higher applied stresses. Tensile twinning does not always play a role since its initiation depends on the starting texture. Along the rod axis, Zircaloy-2 exhibits a very strong weighting of poles lying within the basal plane of the structure such as <10 1 0>, <11 2 0> etc. However, perpendicular to the rod axis, all poles are present. The coefficients of thermal expansion are unequal along the a- and c-axes of the crystal structure, so there are always large intrinsic thermal strains. Likewise, the mechanical properties perpendicular to the rod axis are dominated by the interaction of grains with hard and soft plastic response. Over two decades, the residual strains and the in-situ strain response parallel and perpendicular to the rod axis have been measured by neutron diffraction for both tensile and compressive applied stress. The paper reviews our understanding of the strain development for tensile and compressive applied stress in Zircaloy-2 in terms of slip and tensile twinning, the crucial part played by the thermal strains and the simplifying role of the strong texture.