Temperature Effect on Plutonium Leach Rate of Nuclear Waste Glass

Abstract

The two kinds of nuclear waste glass with similar composition, a ²³⁸Pu-doped and non-radioactive waste glass, were leached under the ISO-test conditions at temperature between 23 and 90°C. An activation energy of 22±10 kJ/mole was obtained from the initial leach rates of Pu, which was much lower than the 78±9 kJ/mole obtained from those of Si, Na, Sr and Cs. It is suggested that in the initial stages of leaching, Pu is not released from the waste glass with the same mechanisms as the releases of Si, Na, Sr and Cs, but the dissolution of hydrous plutonium dioxide PuO₂•xH₂O formed on the glass surface becomes predominant. In the long duration tests (>32 d), the release of Pu appears to be affected by the solubility of PuO₂•xH₂O remaining in the leached surface layers.