PNNL

Abstract

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 to 12 at 80o to 88oC. The chemical compositions of the glasses were identical except the 239Pu/238Pu isotopic ratio, which was varied to yield accumulated doses of 1.3 x 1016, 2.9 x 1017, and 2.6 x 1018 ?-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(23oC) 9 to 10.6 ± 2.7 [g/(m2•d1)] at pH(23oC) 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.