Structural recovery of self-irradiated natural and 238Pu-doped zircon in an acidic solution at 175°C

Mechanism of hydrothermal alteration of natural self-irradiated and synthetic crystalline titanate-based pyrochlore

“…The approach of the present study is completely different and relates to the question of the long-term performance of a pyrochlore waste form under geological conditions. In this and other studies (see Geisler et al, 2004Geisler et al, , 2005a we accelerated the mineral-fluid equilibration by using an extreme proton activity in our starting solution, which hardly occurs on Earth and, least of all, in a potential nuclear repository. By doing this we are, in principle, able to investigate what will happen with a pyrochlore that is exposed to natural aqueous solutions over geological time scales, if we are able to show that our results on the mechanism of mineral-fluid re-equilibration are independent on the proton activity and that the observations made in our experiments agree to some extent with those made on natural samples.…”

Textural and compositional complexities resulting from coupled dissolution–reprecipitation reactions in geomaterials

“…The influence of water-enhanced diffusion is also well illustrated considering the re-equilibration mechanism of zircons. Hydrothermal alteration of natural metamict zircon occurs as a result of hydrousassisted diffusion (Geisler et al 2003), whereas CDR drives the recrystallization of crystalline zircon (Geisler et al 2007) and Pu-doped metamict zircon (Geisler et al 2005) under hydrothermal conditions.…”

Minerals and Natural Analogues

“…Geisler et al 145 have performed a comparative experiment with a radiation-damaged natural zircon from Sri Lanka and a synthetic 238 Pu-doped zircon (4.7 wt% of 238 Pu) in an acidic solution at 175 C. Both zircon samples have suffered a similar degree of radiation damage, as given by their degree of amorphization. XRD measurements of the experimental run products revealed that during the hydrothermal treatment, only the disordered crystalline remnants recovered in the natural zircon, whereas in the 238 Pu-doped zircon, the amorphous phase strongly recrystallized.…”