An experimental study of the dissolution rates of Nd-britholite, an apatite-structured actinide-bearing waste storage host analogue

Claire Chaïrat (1) , Eric H. Oelkers (1) , Jacques Schott (1) , Jean-Eric Lartigue

1 LMTG - Laboratoire des Mécanismes et Transfert en Géologie

The steady-state dissolution rates of Nd-britholite Ca9Nd(PO4)5SiO4F2 have been measured at 25 °C as a function of aqueous solution composition in open-system mixed flow reactors. Measured Nd-britholite dissolution rates based on Ca, P, and F release are found to be close to corresponding apatite dissolution rates; these 25 °C rates decrease from 10?8 to 10?12 mol/m2/s with increasing pH from 3 to 12. Measured Nd release rates are far slower than those of these other elements; Nd concentrations in solution appear to limited by precipitation of a secondary phosphate phase, which limits aqueous Nd concentrations to <10?12 mol/kg at near neutral conditions. Correspondingly, it appears likely that aqueous actinide release from analogous waste hosts will be similarly limited by the precipitation of sparingly soluble phases.

Domaines: Sciences de la Terre

Claire Chaïrat, Eric H. Oelkers, Jacques Schott, Jean-Eric Lartigue. An experimental study of the dissolution rates of Nd-britholite, an apatite-structured actinide-bearing waste storage host analogue. Journal of Nuclear Materials, 2006, 354, pp.14-27. ⟨10.1016/J.JNUCMAT.2006.01.022⟩. ⟨hal-00316707⟩