Elemental dissolution study of Pu-bearing borosilicate glasses

Single-pass flow-through tests were conducted to study the effects of self-radiation damage from alpha decay on dissolution kinetics of three radiation-aged Pu-bearing (1 mass% PuO2) borosilicate glasses over a pH interval of 9-12 at 80-88 °C. The chemical compositions of the glasses were identical except the 239Pu/238Pu isotopic ratio, which was varied to yield accumulated doses of 1.3 × 1016, 2.9 × 1017 and 2.6 × 1018 α-decays/g at the time of testing. Release of Al, B, Cs, Na, Si and U to solution increased with increasing pH, whereas Ca, Pu and Sr were invariant over the pH interval. Average dissolution rates, based on B release, were identical within experimental uncertainty for all three glass compositions and increased from 0.17 ± 0.07 at pH(23 °C) 9 to 10.6 ± 2.7 (g/(m2 d1)) at pH(23 °C) 12. Release rates of Pu were 102- to 105-fold slower compared to all other elements and were not affected by isotopic composition, self-radiation damage sustained by the glass, or pH. These data demonstrate that self-radiation damage does not affect glass dissolution rates, despite exposure to internal radiation doses for >20 years.