Radiation damage can induce significant structural changes in solid materials; these changes may be more extensive in crystalline materials than in glasses, due to amorphization of the crystalline phases. Leaching tests conducted on several simulated waste glasses doped with 244Cm show no significant change in leach rate as a function of increasing dose, even in the case of a partially devitrified waste glasses which exhibited both large volume changes (∼1%) and amorphization of a crystalline phase. Significant increases in the leaching rate of PNL 76-68, a complex simulated nuclear waste glass, were observed to occur in the presence of gamma radiation. Some of the enhanced leaching is due to the generation of nitric acid from air radiolysis in the leach vessel. Nitric acid appears to preferentially attack zinc and lanthanides, both of which normally build up on the surface of the glass when leached in nonacidic solutions. Increased rates were also found for samples irradiated while leaching, but with air excluded to eliminate nitric acid formation, indicating that water radiolysis products may also be important. Samples irradiated with gamma rays prior to leaching showed dissolution rates indistinguishable from that of unirradiated specimens.
ASJC Scopus subject areas
- Waste Management and Disposal
- Environmental Science(all)
- Earth and Planetary Sciences(all)