The lnteraction and Dissolutlon of Solid UO2 by Molten Zircaloy-4 Cladding in an Inert Atmosphere or Steam

Abstract

The dissolution of solid UO₂ by molten Zircaloy-4 cladding, and structural changes in the UO₂ matrix, have been investigated at 2000°C, using internally heated fuel-element simulators. Tests were carried out in an inert atmosphere or steam.

Post-test examinations showed that the molten cladding contains varying proportions of uranium and oxygen that come from the partial dissolution of the UO₂. In the presence of steam, the external cladding surface also reacts to form zirconium oxide, the formation of which is a function of heating rate, time and temperature.

The maximum amount of UO₂ dissolved by the molten Zircaloy-4 cladding was 6 vol.% in the inert atmosphere; the typical amount was 0.5 to l vol.%. In steam, the maximum amount was 0.5 vol.%.