Radiation damage effects in candidate titanates for Pu disposition: Pyrochlore

Role of vein-phases in nanoscale sequestration of U, Nb, Ti, and Pb during the alteration of pyrochlore

“…The calculated dose of the pyrochlore is similar to the values reported for, 244 Cm-substituted pyrochlore that becomes amorphous after accumulation of 3-4 × 10 15 α-decay events/mg, and it approaches doses obtained for Zr based pyrochlore, which remains crystalline up to a dose of 3 × 10 17 α-decay events/mg (Strachan et al, 2005).…”

“…Synthetic and natural pyrochlores, general formula A 2 B 2 O 7 , are of great interest for nuclear waste management because of their flexible crystal chemistry (Lian et al, 2001), chemical durability (Kamizono et al, 1991;Hayakawa and Kamizono, 1993;Yokoi et al, 1995;Icenhower et al, 2003;Roberts et al, 2000;Zhang et al, 2000) high waste loading capabilities (Lumpkin et al, 2000;Giere et al, 2002), and radiation resistance (Wang et al, 1999a,b;Sickafus et al, 2000;Weber and Ewing, 2000;Begg et al, 2001;Lian et al, 2001;Zhu et al, 2002;Ewing, 2005;Strachan et al 2005;Lumpkin, 2006). The pyrochlore supergroup has the space group Fd3m, and the chemical composition is described by the general formula of A 2-m B 2 X 6-w Y 1-n ·pH 2 O, where m = 0-1.7, w = 0-0.7, n = 0-1, and p = 0-2 (Hogarth, 1977;Lumpkin and Ewing, 1992;Lumpkin and Ewing, 1996;Atencio et al, 2010).…”

Leach resistance of murataite-based ceramics containing actinides

“…Therefore, it can be expected that their release rates at pH 2 should be about ∼10 −4 -10 −5 and ∼10 −5 -10 −6 g m −2 d −1 , respectively. Steady-state U and Pu dissolution rates from the pyrochlorebased ceramics at 85 • C and pH 2 were found to be about ∼10 −4 g m −2 d −1 [13]. Therefore, actinide release rates from the murataite-based ceramics are suggested to be lower than those from the pyrochlore-based ceramics by 1-2 orders of magnitude.…”

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

“…Begg et al (2001), for example, have not found any difference between the dissolution rate of amorphised and crystalline Y 2 Ti 2 O 7 and Gd 2 Ti 2 O 7 pyrochlore compositions. Icenhower et al (2006) and Strachan et al (2005) presented data that suggest that there is no increase in dissolution rate as a result of a radiation damage. However there are also data available that show a 50-fold increase in the element release rate of Cm-doped amorphous titanate pyrochlores (Weber et al, 1986).…”