Microstructural Studies of Zr-2.5Nb and Zircaloy-2 Pressure Tubes Irradiated in Indian Pressurized Heavy Water Reactors


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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.



Edited by:

B.S.S. Daniel and G.P. Chaudhari




D. Srivastava et al., "Microstructural Studies of Zr-2.5Nb and Zircaloy-2 Pressure Tubes Irradiated in Indian Pressurized Heavy Water Reactors", Advanced Materials Research, Vol. 585, pp. 56-61, 2012

Online since:

November 2012




[1] D. L. Douglass, , The Metallurgy of Zirconium, Int. Atomic Energy Agency, Vienna, (1971).

[2] B. A. Cheadle, Coleman C. E. and Licht H., , Nucl Tech. 57 (1982)413.

[3] R. A Holt, Journal of Nuclear Materials vol. 372 ( 2008) 182.

[4] D.N. Sah, E. Ramadasan, K. Unnikrishnan, J.L. Singh, P.M. Ouseph, B.N. Rath, H.N. Singh, P.B. Kondejkar, V.D. Alur, Suparna Banerjee, R.S. Shriwastaw, Prerna Mishra, V.P. Jathar, N. Kumawat, M.P. DhotreJournal of Nuclear Materials vol 383 (2008).

DOI: https://doi.org/10.1016/j.jnucmat.2008.08.054

[5] D.N. Sah, D. Srivastava, S. Banerjee, G.K. Dey, TEM examination of irradiated Zircaloy-2 pressure tube material, BARC Report, BARC/2005/E/023.