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Abstract

A metallographic study on the behaviour of the alloying elements Sn, Fe and Cr in high temperature transient oxidations (1600 degrees C - 1800 degrees C) of zircaloy-4 (Zry-4) LWR cladding tubes, was performed by optical microscopy, scanning electron microscopy and electron microprobe x-ray analysis. The oxidations were performed by direct induction heating under oxygen - argon mixtures. The oxidation was made to proceed from the outer surface of the pipes. The examination of the samples revealed that an inner residual layer of the alpha modification of zirconium (alpha-Zr (O)) was left under the zirconium oxide (ZrO-2) scale. The great majority of the alloying elements were found to be present in the inner residual layer of alpha-Zr(O), in two different metallic phases. The micrographs show a typical solidification structure, showing that a liquid phase with the constituents Zr, Sn, Fe and Cr and strongly enriched in the alloying elements, existed along the grains of the residual alpha-Zr(O) at the maximum temperature reached in each transient. The mechanism of melting and of shifting of the liquid phase to the interior of the Zry-4 tubes is briefly discussed.

Additional information

Authors: CAMBINI M, JRC ISPRA ESTAB. (ITALY);BOTTELIER P, JRC ISPRA ESTAB. (ITALY);BUSCAGLIA G, JRC ISPRA ESTAB. (ITALY);MIGLIERINA C JRC ISPRA ESTAB. (ITALY), JRC ISPRA ESTAB. (ITALY)
Bibliographic Reference: JOURNAL OF NUCLEAR MATERIALS, VOL. 115 (1983), NOS. 2&3, PP. 343-346
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